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Journal Cover Australian Journal of Structural Engineering
   [5 followers]  Follow    
   Full-text available via subscription Subscription journal
     ISSN (Print) 1328-7982
     Published by RMIT Publishing Homepage  [417 journals]   [SJR: 0.347]   [H-I: 6]
  • Volume 15 Issue 2 - Analysis of shrinkage in prestressed concrete slabs
           and beams
    • Abstract: Warner, Robert F A step-by-step method of analysis is used in this paper to study the long-term effects of shrinkage in prestressed concrete members, and in particular shrinkage warping and loss of prestress. The step-by-step method is also being used in a parallel study of creep in prestressed concrete beams. A simple, closed-form equation is derived for the long-term shrinkage curvature in the cross-section of a rectangular prestressed member that contains tensile and compressive reinforcing steel. This allows the shrinkage deflection of the member to be calculated by first evaluating curvatures at key sections and then integrating. A simple, closed-form equation is also derived for the long-term loss of prestress due to shrinkage. Numerical studies show that tensile and compressive reinforcement strongly influence both the curvature and the prestress loss due to shrinkage. An assumption made in the analyses is that shrinkage occurs uniformly throughout the concrete. This is the basis of the current AS 3600 shrinkage clauses, and hence also of most current shrinkage design calculations. In reality, shrinkage in concrete members is non-uniform and non-linear. The paper concludes with a discussion of non-uniform shrinkage, and gives an outline of how the step-by-step method can be used to analyse non-uniform shrinkage.
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 15 Issue 2 - Reserve of strength in reinforced concrete frames:
           Analysis of arching action
    • Abstract: Valipour, Hamid R; Vesali, Nima Farhang; Samali, Bijan; Foster, Stephen Compressive membrane (arching) action increases both the capacity and stiffness of longitudinally-restrained reinforced concrete elements; however, contribution of arching action in the loading capacity of reinforced concrete beams within framed structures has not been investigated. In this study, the formulation of a non-linear 1D finite element model is briefly explained and then verified against available experimental data. The developed formulation and analytical tool are employed to undertake a parametric study and effects of compressive strength of concrete, longitudinal reinforcing ratio, stiffness of end supports and number of spans on the ultimate capacity of beams within different types of reinforced concrete assemblages is investigated. For the analysed 2D sub-assemblies, the capacity of the beams calculated from plastic hinge analysis (according to AS3600-2009) is more than 15% below the capacity obtained from non-linear 1D finite element model and this is partially attributed to enhancing effect of arching action which cannot be captured by the model adopted in Australian standard AS3600-2009.
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 15 Issue 2 - The Walsh method of beam-on-mound design from
           inception to current practice
    • Abstract: Payne, David C; Cameron, Don This paper reviews the original Walsh design method used for designing slabs on expansive soil and describes how the method has been implemented from its earliest use in the 1970s up to current practice. The focus of the paper is solely on the Walsh design method and, because the Walsh design method has been the instrument for the deemed-to-comply solutions for raft slab designs within the Australian Standard AS 2870, no comparison is made with alternative approaches used either within or outside Australia for designing residential footings. The paper presents previously unpublished changes to the original the Walsh method made as part of its inclusion in the two most recent editions of the Australian Standard AS 2870 and broadly discusses some of the impacts of these changes. A new adaptation of the Walsh method, written by the first named author, is introduced in which new parameters have been adopted to model more accurately the soil-footing interaction than previous adaptations. These changes still achieve residential footing designs comparable to those obtained using existing versions of the Walsh design method and are in keeping with the spirit of the Standard and Walsh's original intentions for the implementation of his program.
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 15 Issue 2 - Interfacial bond strength of resin-impregnated
           fibre-reinforced polymer laminates bonded to concrete using vacuum and
           heat: Experimental study
    • Abstract: Gravina, Rebecca J; Hadigheh, Seyed A; Setunge, S Two processing techniques commonly used in the repair of concrete structures via bond of fibre-reinforced polymer (FRP) onto the substrate are known as the pultruded plate and wet lay-up systems. The pultruded FRP plate and wet lay-up systems both involve the curing of resins of up to several days under ambient conditions to achieve full load capacity and rely on workmanship to achieve good bond. Hence, new techniques for the application of FRP that adopt a vacuum consolidation process and heat to impregnate FRP fibres with resin to improve the curing process, bond strength and speed of application are being developed. In this article, the interfacial bond behaviour of pre-impregnated FRP laminates attached to concrete in the presence of vacuum and heat is studied and compared to more conventional methods of FRP strengthening systems. Further the effects of bondline thickness on the bond performance of pre-preg FRP laminates are also studied whereby three different bondline thicknesses are examined. The interfacial bond thickness was changed by application of resin films between FRP plates and concrete surface.
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 15 Issue 2 - Numerically integrated analysis and design of
           continuous composite beams
    • Abstract: Wang, Aaron J This paper reports a comprehensive three-dimensional finite element study to examine the structural behaviour of continuous composite beams with the consideration of the flexibility of shear connectors. With the full incorporation of material, geometrical and interfacial non-linearities, the results of the proposed finite element models compare quite well with test results of continuous composite beams with a wide range of geometrical configurations, material properties, arrangements of shear connectors as well as loading and boundary conditions. The results from the proposed finite element models are compared with those from the established design rules. A simplified two-dimensional finite element model is also proposed as a performance based integrated analysis and design tool for continuous composite beams as a possible extension of currently available test data and design practice.
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 15 Issue 2 - Limit state approach to sizing and design of
           rectangular footings
    • Abstract: Beletich, Argeo S Limit state design was introduced into some standards in the early 1970s followed by expansion of limit state design into all our structural standards. With pad footings, limit state design is only applied to the structural design components such as thickness of the footing, size and distribution of reinforcement required to resist moments and shear forces. However, the size, ie. contact area of the footing required to transmit column loads is determined by working strength techniques whereby a predetermined allowable soil bearing pressure qa is used to transmit the applied permanent action (dead) loads (G) and superimposed action (live) loads (Q). There appears to be a contradiction in two different approaches applied concurrently in footing design. This article considers the application of limit state design method for determining size of rectangular pad footings.
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 15 Issue 2 - Preface
    • Abstract: Wilson, John; Gad, Emad
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 15 Issue 2 - Establishing compliance of steel mill products: A
           comparison between Australian steel standards and the corresponding
           European standards
    • Abstract: Fatemi-Nayeri, Hamid; Ancich, Eric Steel bridge design as well as other steel structures design could be considered incomplete unless the compliance of the procured steel has been evaluated and determined through a method which is acceptable in accordance with the requirements of the relevant standard. According to Australian structural steel standards, the acceptance of steel is conditional on the evidence of compliance provided in the mill test report/certificate. By comparison, the corresponding European steel product standards include a more comprehensive section explaining the process of evaluation of conformity. This includes a normative section regarding initial type testing, factory production control as well as an informative section regarding a system of attestation of conformity by an approved body and affixing of CE marking on the product by the steel manufacturer. Also, there are provisions in Australian and European standards regarding the method of establishing compliance as the basis of design. However, a lack of adequate statistical data on overseas manufactured steels poses difficulties in the derivation of design values of material or product properties by testing.
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 15 Issue 2 - Drift capacity of lightly reinforced concrete columns
    • Abstract: Wibowo, Ari; Wilson, John L; Lam, Nelson TK; Gad, Emad F This paper presents the findings of a research project investigating the lateral load drift behaviour of lightly reinforced concrete columns. Such columns of limited ductility are common in regions of low-moderate seismicity, and although their strength properties are well defined, the drift performance is less understood. The paper presents the results of an experimental study undertaken and the development of a theoretical model for predicting the lateral load-drift behaviour of lightly reinforced concrete columns together with a simplified bi-linear model for checking purposes. The test results are presented and clearly indicate the dramatic impact that the axial load ratio has on the drift performance of columns of limited ductility, particularly the significantly lower drift capacities that are available in compression dominated columns.
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 15 Issue 2 - A non-linear steel-concrete interface damage model for
           reinforced concrete after cracking
    • Abstract: Castel, Arnaud; Gilbert, RIan; Ranzi, Gianluca; Foster, Stephen In reinforced concrete construction, deflection control is an important performance criterion for its serviceability and sustainability. In this paper, a finite element model dedicated to the calculation of the overall stiffness of reinforced concrete beams is extended in order to take into account steel-concrete interface damage due to excessive live loading resulting from cover-controlled cracking. The effect of cover-controlled cracking is taken into account by implementing a damage variable to reduce the bond at the steel-concrete interface. In addition, a criterion for the initiation of cover-control cracks based on a peak value of the steel stress at the crack location is also defined.
      PubDate: Sat, 26 Apr 2014 19:45:30 GMT
       
  • Volume 14 Issue 3 - Fracture properties of high performance concrete
           containing silica fume
    • Abstract: Zhang, P; Li, Q A parametric experimental study has been conducted to investigate the effect of silica fume on the fracture properties of high performance concrete (HPC), with five silica fume contents (1.5%, 3%, 6%, 9% and 12%) used. The results indicate that the addition of silica fume has greatly improved the fracture parameters of HPC, such as fracture toughness, fracture energy, effective crack length, the maximum mid-span deflection, the critical crack opening displacement and the maximum crack opening displacement of concrete. The fracture parameters of HPC containing silica fume are increasing gradually with the increase of silica fume content when the silica fume content increases from 0% to 3%, while, the fracture parameters begin to decrease after the silica fume content increases beyond 3%. However, the values of the fracture parameters of HPC with the silica fume content below 12% are still higher than that of the concrete without silica fume. It seems a small content of silica fume has an advantage of improvement of the fracture properties of HPC, while an overlarge silica fume content may adversely affect the fracture properties of HPC.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - Strength and durability characteristics of concrete
           made with fly-ash blended cement
    • Abstract: Islam, MM; Islam, MS Sustainability issue in construction sector came forward over the last two decades due to concerns regarding using virgin materials as well as emission of greenhouse gases from production of raw materials. Cement is the prime constituents of concrete and contributes approximately 7% of global man made CO2 production. Interest in blended cements is growing because of its advantages as increased production economy, reduced CO2 emissions and fuel consumption. This paper discusses the effects of cement replacement with supplementary cementitious material fly-ash on the strength development, water permeability and rapid chloride penetration resistance of concrete over the curing age of 365 days. Three different grades of concrete M38, M33 and M28, each with seven different fly-ash replacement level, 10, 20, 30, 40, 50, 60 and 70% were used for the experimental program. Ordinary Portland cement concrete was also used as reference concrete. Coefficient of permeability as well as rapid chloride penetration resistance was determined at an age of 28, 56, 90, 180 and 365 days whereas strength at 3, 7, 28, 56, 90, 180 and 365 days. Test results show that permeability of concrete decreases with the increase of fly-ash level up to an optimum value and then start to increase, whereas strength of concrete increases with the increase of fly-ash up to an optimum level and then starts to decrease. Among all the concretes studied, the optimum amount of cement replacement is reported to be 30%. The study reveals that fly-ash concrete is less permeable and achieves higher strength due to pozzolanic activity of fly-ashes that creates more durable calcium silicate hydrate and fills capillaries and bleed water channels occupied by water soluble lime. As a result fly-ash concrete inhibits the penetration of aggressive species including chloride which can effectively reduce the corrosion of the embedded steel reinforcement.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - Effects of joint thickness, adhesion and web shells to
           the face shell bedded concrete masonry loaded in compression
    • Abstract: Thamboo, JA; Dhanasekar, M; Yan, C The Australian masonry standard allows either prism tests or correction factors based on the block height and mortar thickness to evaluate masonry compressive strength. The correction factor helps the taller units with conventional 10 mm mortar being not disadvantaged due to size effect. In recent times, 2-4 mm thick, high-adhesive mortars and H blocks with only the mid-web shell are used in masonry construction. H blocks and thinner and higher adhesive mortars have renewed interest of the compression behaviour of hollow concrete masonry and hence is revisited in this paper. This paper presents an experimental study carried out to examine the effects of the thickness of mortar joints, the type of mortar adhesives and the presence of web shells in the hollow concrete masonry prisms under axial compression. A non-contact digital image correlation technique was used to measure the deformation of the prisms and was found adequate for the determination of strain field of the loaded face shells subjected to axial compression. It is found that the absence of end web shells lowers the compressive strength and stiffness of the prisms and the thinner and higher adhesive mortars increase the compressive strength and stiffness, while lowering the Poisson's ratio.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - The effect of compressed infill panels on cyclic
           performance of exterior beam-column joints
    • Abstract: Dadi, VVSSK; Agarwal, P The confining effect of infill panels on the hysteresis performance of the external beam-column joints has been studied experimentally. Four hinged joints and two rigid joints have been tested under cyclic loading with the interaction of infill panels on both the sides of the joints. The infill panels have remained subjected to different compression loads applied either at centre or at the end positions of the infill panels. This effect of infill panels has shown an increase with the increase in amount of compression load. The cyclic evaluation of hinged joints with infill panels has been used to determine the shear resistance of infill panels which has not only depended upon the amount but also on the location of compression load. It has been observed that the load-deformation diagrams of rigid beam-column joints with infill panels manifest a significant increase in the capacity of the joint by confining the joint with infill panels. The obtained capacity has almost been the result of the combined effects of two independent systems, ie. bare rigid joint system and compressed infill panel system.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - Cyclic performance evaluation of unconfined and
           confined beam-column joint specimens with different type of reinforcing
           characteristics as per ASCE/SEI 41-06
    • Abstract: Dadi, VVSSK; Agarwal, P The cyclic performance evaluation of external beam-column joints have been evaluated experimentally on the basis of ASCE/SEI 41-06. The effects of a number of additional constructional parameters such as type of reinforcement, percentage of reinforcement, effect of confinement as per IS13920: 1993 (Bureau of Indian Standards, 1993) have also been incorporated. A low decay in strength and high energy dissipation with low post elastic strength degradation over yield is observed in confined specimens as compared to unconfined specimens. The effect of types of reinforcement is reflected in the non-linear behaviour of those beam-column joint specimens which fulfil the strong column-weak beam condition. The plastic rotation capacity of these joints increases with an increase in ductility of reinforcement. A higher value of non-modelling parameters have been observed as compared to ASCE/SEI 41-06.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - Modelling of the concrete compressive failure
           mechanism
    • Abstract: Su, Y; Wu, C; Oehlers, DJ There has been an extensive amount of research into determining the compressive stress-strain properties of concrete for design. Difficulty has arisen in quantifying the softening or descending stress-strain relationship as it has been found to depend on the size and shape of the specimen being tested as well as on the confinement and eccentricity of compressive load applied to the specimen. This difficulty has restricted the development of design rules for reinforced concrete members not only for strength but also for ductility particularly for confined members. In this paper, a meso-scale model, which divides concrete into a three phase composite material consisting of the mortar matrix, aggregate and interfacial transition zone, is used to explain and quantify the softening mechanism of concrete specimens. It is shown that this meso-scale model can both simulate the cracking patterns and deformations which are seen to occur in concrete while softening and also quantify and explain the effects of size, shape, confinement and eccentricity of load. This realistic simulation of the softening mechanism should allow a better understanding and quantification of the compressive failure mechanism of concrete which should lead to the development of better design rules particularly for confined concrete.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - Numerical modelling and full-scale testing of concrete
           piles under lateral loading
    • Abstract: Tuladhar, R; Mutsuyoshi, H; Maki, T Full-scale lateral loading tests were carried out on hollow-pre-cast-pre-stressed concrete piles embedded into the ground. The results from the tests were used as the basis for the analysis where soil was modelled as 20-node solid elements; and for the modelling of piles comparison was done between 3-node beam elements and 20-node solid elements. It showed that the 3-node beam element modelling for pile largely underestimates its lateral capacity. The 20-node solid element modelling can, however, accurately simulate the experimental results when interface element between pile and soil, and the degradation of shear stiffness of soil in cyclic loading is considered.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - Examining the role of structural engineers in green
           building ratings and sustainable development
    • Abstract: Chaudhary, MTA; Piracha, A This paper examines role of structural engineers in design of green buildings by analysing credits available for the structural aspects of buildings in the four rating systems (LEED, BREEAM, Estidama and Green Star). It was concluded that the points related to the structural credits are roughly proportional to the cost of structural elements in buildings. However, participation of structural engineers in the sustainability efforts is disproportionally low based on the percentage of structural engineers holding LEED Accredited Professionals (LEED AP) designation. Embodied and total energy requirements of typical buildings were examined and it was concluded that embodied energy in the structural components has a share ranging from 2% for traditional buildings to 25% for net-zero buildings. Finally, the sustainability aspects related to structural design that are currently ignored in the rating systems were identified and discussed. Such aspects include: baseline material usage, structural robustness and resilience to disasters, structural adaptability and reuse, structural durability and longevity. It was emphasised that a structure can be sustainable, in true spirit of the terminology, without achieving significant points in the rating systems as long it satisfies the guiding principle of reducing burden on natural resources and the environment.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - Early-age tensile strength and calcium hydroxide
           content of concrete containing low-calcium fly-ash
    • Abstract: Sarker, PK The effects of using fly-ash in concrete on the early-age tensile strength and the effectiveness of reactive bond breakers are concerns for applications such as tilt-up panels and liftslabs, however, experimental data is scarce in literature. Fifteen concrete mixtures with up to 40% low-calcium fly-ash were tested. The early-age tensile strength of fly-ash concrete was found to correlate well with compressive strength. The calcium hydroxide (CH) content on concrete surface was found to vary in a wide range because of the varying distribution of aggregates. Generally, the CH content decreased with the increase of fly-ash. The CH content increased with age in the control concrete while the change was relatively small for the fly-ash concretes up to the age of 7 days. Thus, the reduction of CH content in concrete containing high volume low-calcium fly-ash may have signifi cant effect on the performance of bond breakers.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - Post-tensioned band beams as moment resisting frames
           under earthquake loading: A state-of-the-art review
    • Abstract: Davey, MJ; Abdouka, K; Al-Mahaidi, R Post-tensioned concrete wide-band beams are used increasingly as a common floor construction method in Australia. More recently, there has been a growing need for the floor system to contribute to the seismic resistance of the building as a moment frame. However, relatively little is known about the performance of wide post-tensioned beams under this type of loading. This paper reviews the current state of knowledge in this area, and assesses several current building design codes in terms of their relevance to this type of construction. Current research shows the potential to achieve adequate drift and energy dissipation in areas of low to moderate seismicity, but research is very limited, particularly for post-tensioned wide beams. While AS3600-2009 does not contain any width limitations on beams resisting earthquake loads, other codes do limit this width for certain levels of ductility. However, these design codes focus on narrow beams, and the beam width restrictions are generally based on limited research data. Construction techniques and seismicity levels vary significantly for different countries and this affects different design codes. Therefore, the relevance and applicability of several code design and detailing requirements in relation to beam widths and detailing typically used in Australia are questionable.
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 3 - Preface
    • Abstract: Melchers, Rob
      PubDate: Mon, 28 Oct 2013 20:19:04 GMT
       
  • Volume 14 Issue 2 - Preventing failure through the management of
           uncertainty
    • Abstract: Carpenter, J A review of the press or search of the internet tells us that structures continue to fail. These extreme events are a worldwide phenomenon; the so-called developed countries are not immune. This paper explores some of the issues and initiatives stemming from the UK. It will refer to the work of the Standing Committee on Structural Safety, to the recent study of major hazards in construction, and to work on disproportionate collapse. The prevention of failure requires competent persons, robust processes and assured products - the 3Ps - working within a contractual and statutory framework. The issues are wide ranging: globalisation, rapid growth, commercial pressures, and the danger of forgetting "safety" in the rush to accommodate sustainability. How we can bring this about (starting at the education base phase, through initial professional development and then into later professional life) is discussed in the paper. This paper is a continuation of the themes identifi ed in "Safety, risk and failure - the management of uncertainty" (Carpenter, 2008).
      PubDate: Mon, 16 Sep 2013 10:55:16 GMT
       
  • Volume 14 Issue 2 - Preface
    • Abstract: Ho, Peter
      PubDate: Mon, 16 Sep 2013 10:55:16 GMT
       
  • Volume 14 Issue 2 - Incorporating climate change adaptation into
           engineering design concepts and solutions
    • Abstract: Connor, T; Niall, R; Cummings, P; Papillo, M Designers of significant works of infrastructure should consider the complexities of climate change and anticipate the potential impacts over the projected lifetime of the infrastructure. This paper addresses how engineers can comprehensively address climate change in design in a balanced manner. It provides a framework for adaptation in engineering design and includes a specific approach towards a balanced whole-of-life assessment of risk, as opposed to a do-nothing approach, or conservatively designing for worst-case scenario impacts that may not be realised for many decades.
      PubDate: Mon, 16 Sep 2013 10:55:16 GMT
       
  • Volume 14 Issue 2 - Earthquakes and the effects on structures: Some of the
           lessons learnt
    • Abstract: Bull, DK The observed performance of a range of structures when subjected to significant earthquakes will be described. The emphasis of this paper is on reinforced concrete buildings, including frames and walls. The fundamental issues that affect structures will be highlighted: failure and collapse modes; maintenance of load paths; interaction of primary structural elements (eg. floor diaphragms and vertical elements) with secondary elements such as stairs and ramps; structural systems that may employ zones of inelastic behaviour, resulting in "ductility". Observation of structural performance during earthquakes will be used to illustrate the issues noted. Examples of changes in design practice resulting from the observations will be presented.
      PubDate: Mon, 16 Sep 2013 10:55:16 GMT
       
  • Volume 14 Issue 2 - Structural design for disaster risk reduction
    • Abstract: Grundy, P The risk of loss from natural disasters, in terms of lives, livelihoods and social capital, is shown to be unacceptably high compared with acceptable risk from losses for which mankind is responsible. The collective loss is much worse than the sum of individual losses. The impact seems worst for non-engineered housing, fragile and vulnerable to natural hazards. The concept of Disaster Limit State (DLS) has been developed for structural engineers, above and beyond the Ultimate Limit State (ULS). Key to DLS is the recognition of post disaster function of the building or system being designed, combined with the recognition that heightened standards of design must be combined with non-engineering disaster risk reduction measures in a holistic way, with full community engagement. This is a challenge for structural and planning engineers, requiring an expanded vision and imagination.
      PubDate: Mon, 16 Sep 2013 10:55:16 GMT
       
  • Volume 14 Issue 2 - 2011 to 2012 Queensland floods and cyclone events:
           Lessons learnt for bridge transport infrastructure
    • Abstract: Pritchard, RW During the two-year period, April 2010 to April 2012, a series of extreme weather events occurred in Queensland. Due to extensive fl ooding and cyclonic conditions impacting communities and vital infrastructure, the majority of the state was declared a natural disaster zone. As a consequence, it is estimated the road network suffered damages in excess of $7 billion with local authorities suffering additional damage of similar magnitude in monetary terms. This paper identifi es a range of issues encountered as a result of these natural disasters, including the destruction of timber bridges, settlement of piers, scour at abutments and loss of road approaches to bridges. It is postulated that the AS 5100 Bridge Design Code was written mainly for traditional rural applications. Additionally, this paper examines the actual loads that urban bridges were subjected to including fl oating debris such as shipping containers, cars and river-craft (for example 300 t vessels) that should be incorporated in future revisions of AS 5100. It is suggested that in future, bridge design codes should consider the context and location of bridges for connectivity and post disaster functionality. It is recommended such learning's be considered and applied to new bridges and remedial works in conjunction with suggested amendments to AS 5100 Bridge Design Code.
      PubDate: Mon, 16 Sep 2013 10:55:16 GMT
       
  • Volume 14 Issue 2 - Behaviour of tall buildings and structures in strong
           winds: Dynamic properties, response characteristics and vibration
           mitigation
    • Abstract: Kwok, KCS This paper presents techniques and instrumentation employed in the measurement of dynamic structural properties of tall buildings and structures, long-term monitoring of their responses in strong winds, and vibration mitigation systems installed in actual buildings and structures. The merits and limitations of these techniques are discussed. Natural frequencies of vibration, deflected mode shapes and damping values can be determined reliably through dynamic measurements on actual buildings, and these results provide invaluable validations of numerical modelling techniques and generalised prediction formulae. The improved accuracy of prediction processes, coupled with a better understanding of building performance in strong winds, through long-term building monitoring, can lead to significant cost savings in the wind-resistant design and construction of tall buildings.
      PubDate: Mon, 16 Sep 2013 10:55:16 GMT
       
  • Volume 14 Issue 1 - A study of variability and applicability of various
           signal processing techniques in structural system identification
    • Abstract: Bao, C; Hao, H; Li, Z The structural responses and vibration properties such as frequencies and mode shapes are directly related to the structural mass and stiffness. Changing structural conditions will affect the structural responses and vibration properties. Structural conditions can thus be identified through measurements of structural vibration. However, certain uncertainties associated with structure models, changing ambient environmental conditions, changing loading conditions, equipment noises and various signal processing techniques used in extracting structural vibration properties, etc. is inevitable. The influences of these uncertainties on structural vibration properties might be more significant than that of the structural damage, therefore, cause false identification or result in the true structural damage not identifiable. This paper studies the applicability and reliability of a few popularly used modal identification methods including time-domain, frequency-domain and time-frequency domain methods for civil structural system identification. The results indicate that on average a 2% to 3% error tends to be yielded by using different signal processing techniques for vibration frequencies identification when the signal is not heavily noise contaminated, which should be taken into account when estimating the damage detection results. The applicability of the time-frequency domain methods to the identification of time-varying system either with sudden change or continuous variance is also discussed.
      PubDate: Wed, 27 Mar 2013 09:59:01 GMT
       
  • Volume 14 Issue 1 - Determination of the embedded lengths of electricity
           timber poles utilising flexural wave generated from impacts
    • Abstract: Subhani, M; Li, J; Samali, B; Yan, N Round timbers are extensively used as utility poles in Australia for electricity distribution and communication. Lack of information on their conditions results in great difficulties on asset management for industries. Despite the development of various non-destructive testing (NDT) techniques for evaluating the condition of piles, few NDTs are reported for applications on timber poles. This paper addresses challenges and issues on development of NDTs for condition assessment and embedded length of timber poles. For this paper, it is mainly focusing on determining the embedded length of the pole considering loss of the sufficient embedment length is a main factor compromising capacity and safety of timber poles. Since it is impractical for generating longitudinal waves by impacting from the top of poles, utilising flexural wave from side impact on poles becomes attractive. However, the flexural wave is known by its highly dispersive nature. In this paper, one dimensional wave theory, guided wave theory and advanced signal processing techniques have been introduced in order to provide a solution for the problem. Two signal processing techniques, namely short kernel method and continuous wavelet transform, have been investigated for processing flexural wave signals to evaluate wave velocity and embedment length of timber poles in service.
      PubDate: Wed, 27 Mar 2013 09:59:01 GMT
       
  • Volume 14 Issue 1 - Methodology for measuring the vertical displacements
           of bridges using fibre bragg grating sensors
    • Abstract: Yau, MH; Chan, THT; Thambiratnam, DP; Tam, HY In many bridges, vertical displacements are one of the most relevant parameters for structural health monitoring in both the short- and long-terms. Bridge managers around the globe are always looking for a simple way to measure vertical displacements of bridges. However, it is difficult to carry out such measurements. On the other hand, in recent years, with the advancement of fibre-optic technologies, fibre Bragg grating (FBG) sensors are more commonly used in structural health monitoring due to their outstanding advantages including multiplexing capability, immunity of electromagnetic interference as well as high resolution and accuracy. For these reasons, a methodology for measuring the vertical displacements of bridges using FBG sensors is proposed. The methodology includes two approaches. One of which is based on curvature measurements while the other utilises inclination measurements from successfully developed FBG tilt sensors. A series of simulation tests of a full-scale bridge was conducted. It shows that both approaches can be implemented to measure the vertical displacements for bridges with various support conditions, varying stiffness along the spans and without any prior known loading. A static loading beam test with increasing loads at the mid-span and a beam test with different loading locations were conducted to measure vertical displacements using FBG strain sensors and tilt sensors. The results show that the approaches can successfully measure vertical displacements.
      PubDate: Wed, 27 Mar 2013 09:59:01 GMT
       
  • Volume 14 Issue 1 - Damage detection of reinforced concrete structures
           based on the wiener filter
    • Abstract: Jayawardhana,, M; Zhu, X; Liyanapathirana, R This paper presents a novel decentralised structural damage detection method based on the Wiener filter. The Wiener filter is customarily used for filtering out the noise that has corrupted a signal, and it is also used for system identification by matching the output of the filter with that of the unknown system. In this study, a damage index based on the mean square error of the Wiener filter is proposed to indicate the damage in structures. The current measurement is the input of the filter and the response of the undamaged structure is the design signal. Another index calculated from the cross correlation responses of neighbouring sensors is used to determine the damage location. An experimental study has been carried out on a reinforced concrete structure. The results show that this method is effective and reliable for structural damage detection and localisation.
      PubDate: Wed, 27 Mar 2013 09:59:01 GMT
       
  • Volume 14 Issue 1 - Identification of de-bonding between steel bars and
           concrete using wavelet techniques: Comparative study
    • Abstract: Ou, G; Wang, Y; Hao, H; Zhu, XQ The interface between steel bar and concrete plays an important role in retaining the strength of reinforced concrete structures. When the interface is damaged by cracking, de-bonding between the two materials and/or other kinds of damage, significant degradation of the structural performances will occur owing to loss of composite actions. In this study, wave propagation on several steel bars embedded in two concrete plates with different de-bonding scenarios is tested. Piezoelectric actuators and sensors are attached to steel bars for recording input and response signals. This paper uses the wavelet transform combined with the wavelet packet decomposition, component energy and Shannon entropy to analyse the experimental results. The results demonstrate that both damage index and relative entropy are sensitive to the existence of de-bonding damage and change linearly with de-bonding length when there is only a single de-bonding damage, while energy and entropy distribution are largely influenced by the property of the excitation signal. When multiple de-bonding exists, however, both the damage index and relative entropy have no such clear tendency.
      PubDate: Wed, 27 Mar 2013 09:59:01 GMT
       
  • Volume 14 Issue 1 - Structural health monitoring of older timber bridge
           girders using laser-based techniques
    • Abstract: Moore, JC; Mahini, S; Glencross-Grant, R; Patterson, R A new method of measuring the mid-span deflections of older timber bridge girders is presented in this paper. There are many timber beam bridges of unknown reliability in regional Australia under high traffic service loadings that were designed according to older codes. In order to identify the current safety index and probability of failure of these girders while in service, it is necessary to measure their deflections under normal and actual loadings. Because of the large numbers of in-service girders that need to be measured, it is important to use a quick, low cost, and easy-tosetup method in the field. A laser-based method is proposed here, which is adjusted to produce an image of the laser on a graduated chart mounted at the mid-span of the bridge girder. The source is mounted on a stable support. Traffic loading deflects the girder and the chart moves up and down in unison. A high speed camera was used to record the movements of the chart relative to the image of the laser. The video recording of the chart movements relative to the laser source was analysed to identify the peak movements. The chart was inscribed so that any movement of the image could be easily read from the graduated scale. It can be inferred from the results that, when the girder is loaded by moving traffic loads, the peak dynamic deflection of a girder can be readily identified.
      PubDate: Wed, 27 Mar 2013 09:59:01 GMT
       
  • Volume 14 Issue 1 - The three-stage artificial neural network method for
           damage assessment of building structures
    • Abstract: Bandara, RP; Chan, THT; Thambiratnam, DP Building structures are often huge and composed of a number of elements. It may not be possible to make modal measurements along the large number of degrees of freedom. Structural damage detection therefore becomes much more challenging both in terms of measurement and subsequent analyses. Accordingly, a problem in structural damage detection is requirement of a systematic and effective method. Among the developed damage detection techniques, artificial neural networks (ANNs) have become promising tools recently. The main drawback of using ANNs in structural condition monitoring is the requirement of enormous computational effort. To address this issue, a novel technique is proposed using "damage index" derived from frequency response functions (FRFs) with the three-stage ANN method to detect damage. The basic idea of this method is to establish features of damaged structure using FRFs from different measurement points. Then using these features, damage indices of damage cases of the structure are identified. Damage indices corresponding to different damage locations and severities are introduced to ANNs. The effectiveness of the proposed method is validated using the finite element model of a 10-storey framed structure. The results show that the principal component analysis based damage index is suitable for structural damage detection.
      PubDate: Wed, 27 Mar 2013 09:59:01 GMT
       
  • Volume 14 Issue 1 - A statistical strategy to select optimal structural
           health monitoring data in operational modal analysis
    • Abstract: Wang, FL; Chan, THT; Thambiratnam, DP; Tan, Andy CC Operational modal analysis (OMA) is prevalent in modal identification of civil structures. It asks for response measurements of the underlying structure under ambient loads. A valid OMA method requires the excitation be white noise in time and space. Although there are numerous applications of OMA in the literature, few have investigated the statistical distribution of a measurement and the influence of such randomness to modal identification. This research has attempted modified kurtosis to evaluate the statistical distribution of raw measurement data. In addition, a windowing strategy employing this index has been proposed to select quality datasets. In order to demonstrate how the data selection strategy works, the ambient vibration measurements of a laboratory bridge model and a real cable-stayed bridge have been respectively considered. The analysis incorporated with frequency domain decomposition (FDD) as the target OMA approach for modal identification. The modal identification results using the data segments with different randomness have been compared. The discrepancy in FDD spectra of the results indicates that, in order to fulfil the assumption of an OMA method, special care shall be taken in processing a long vibration measurement data. The proposed data selection strategy is easy-to-apply and verified effective in modal analysis.
      PubDate: Wed, 27 Mar 2013 09:59:01 GMT
       
  • Volume 14 Issue 1 - Australian network of structural health monitoring
    • Abstract: Chan, Tommy HT; Wang, Ying
      PubDate: Wed, 27 Mar 2013 09:59:01 GMT
       
  • Volume 13 Issue 3 - Enhancing predicted shear strength for the assessment
           of existing concrete bridges
    • Abstract: Giaccio, C This paper presents a method of calculating the enhanced shear capacity of concrete T-beams that arises from the increased concrete contribution provided by the flange overhangs of reinforced concrete (RC) T-beams in positive bending or sagging. The method applies recognised provisions in the Australian Concrete Bridge Design Code AS5100-5:2004 to enhance the prediction of shear strength of concrete T-beams based on failure mechanisms reported in published experimental work. The method is applied to specimens reported in previous experimental studies that report shear failure in RC T-beams in positive bending or sagging. It is shown to yield conservative estimates of shear strength enhancement that arise in a T-beam giving consideration to the flange overhangs. A discussion is provided to outline the application of this method for calculating shear strength of concrete highway bridge decks where T-shaped cross-sections resist an applied shear. The paper discusses the variability that arises in the prediction of shear strength from applying the method. The variability observed in the application is consistent with that observed in shear strength tests used as a basis for code-based formulations. All international codes use a lower value of strength reduction for shear than pure flexure to cater for this. It is recommended that confidence in the method be increased by applying the method to more testing targeted at isolating the flange proportions on the shear strength of RC T-beams in sagging.
      PubDate: Thu, 3 Jan 2013 16:35:30 GMT
       
  • Volume 13 Issue 3 - Bond characteristics of reinforcing steel bars
           embedded in self-compacting concrete
    • Abstract: Aslani, F; Nejadi, S Self-compacting concrete (SCC) is a special high-performance concrete type with a high flowability that can fill formwork without any mechanical vibration. Modification in the mix design of SCC can have a significant influence on the material's mechanical properties. Therefore, it is important to investigate whether all of the assumptions about conventional concrete (CC) design structures are also valid for SCC construction. Bond behaviour between concrete and reinforcement is a primary factor in the design of reinforced concrete structures. This study presents a bond strength model and bond-slip relationship based on the experimental results from eight recent investigations of SCC and CC. In addition, the proposed model, code provisions, and empirical equations and experimental results from recent studies on the bond strength of SCC and CC are compared. The investigated parameters on bond strength are the steel bar diameter, concrete compressive strength, concrete type, curing age of the concrete, and height of the embedded bar along the formwork.
      PubDate: Thu, 3 Jan 2013 16:34:12 GMT
       
  • Volume 13 Issue 3 - A study on semi-continuous composite beams with
           realistic modelling of end-plate connections
    • Abstract: Wang, AJ A comprehensive parametric study is presented in this paper, which examines numerically the structural behaviour of semi-continuous composite beams with end-plate connections of different material properties and geometrical configurations adopting a two-dimensional finite element model. Both ductile and non-ductile shear connectors are covered to investigate the effect of flexibility of the shear connectors on the overall structural behaviour of semi-continuous composite beams. Moreover, the effect of the uniform elongation strain limits of tensile reinforcement is also studied. Various structural performances, including load-deformation characteristics, concrete cracking and moment redistributions, are covered and studied in depth.
      PubDate: Thu, 3 Jan 2013 16:32:31 GMT
       
  • Volume 13 Issue 3 - Direct displacement-based seismic design of steel
           concentric braced frame structures
    • Abstract: Wijesundara, KK; Rajeev, P The direct displacement-based design (DDBD) procedure is well developed and used for designing reinforced concrete moment resisting frame structures, wall structures and bridges. However, there is limited number of studies available on designing steel concentric braced frame (CBF) structures using DDBD approach. Therefore, it is necessary to develop a DDBD procedure for CBF structures. On this regards, this paper proposes a DDBD procedure for steel CBF structures. The proposed procedure utilises the yield displacement shape derived on the basis of tensile yielding of the braces, and the equivalent viscous damping equation of the system proposed by Wijesundara et al (2011) as a function of system ductility and non-dimensional slenderness ratio for steel CBF structures. Finally, the performance of four steel CBF structures designed according to the proposed DDBD procedure is studied using non-linear dynamic response of the structures. The results show that the performance of CBF structures is in good agreement with the design considerations.
      PubDate: Thu, 3 Jan 2013 16:29:31 GMT
       
  • Volume 13 Issue 3 - Effect of hole location on the load-carrying capacity
           of laminated veneer lumber beams
    • Abstract: Ardalany, M; Fragiacomo, M; Deam, B; Carradine, D Predicting load-carrying capacity of timber beams with holes requires a model capable of accounting for the microscopic material behaviour that influences crack initiation and propagation. The complex stress distribution around the periphery of a hole causes additional tension perpendicular to grain stresses, which can change the failure mode of the beam. This situation can also be affected with a change of hole location within the beam depth because stress intensity factor will be increased by tensile stresses and decreased by compressive stresses. This is not an unlikely situation as services often have to pass through beams at different depths. This paper investigates the effect of changing the hole location through the depth of laminated veneer lumber (LVL) beams utilising an experimental and numerical investigation. Experimental tests to failure of LVL beams and numerical simulations using finite element methods show that for a hole eccentricity of less than 20% of the beam depth, the load-carrying capacity of the beam does not change significantly. For uniformly distributed loading, a linearly decreasing stress intensity factor from the support to mid-span is exhibited, showing an increase in load-carrying capacity as the opening approached mid-span.
      PubDate: Thu, 3 Jan 2013 16:26:08 GMT
       
  • Volume 13 Issue 3 - Mathematical modelling of stress-strain curves of
           masonry materials
    • Abstract: Alwathaf, AH; Thanoon, WA; Jaafar, MS; Noorzaei, J Stress-strain relationship of masonry material is essential to predict strength and deformation of masonry structures in analytical modelling. This relationship is important when the masonry system consists of different material properties. In this study, compression testing is conducted, and the best fit equation of experimental data for masonry block and grout is employed. Numerical technique is proposed to obtain proper material parameters for both ascending and descending parts. The proposed expression is capable of simulating the stress-strain relation for different masonry materials, and can be incorporated efficiently into the biaxial stress model. To examine its ability to simulate the stress-strain behaviour in masonry modelling, the proposed formula has been incorporated into a finite element program for masonry analysis using a micromodelling approach. Accurate simulation for the compression test results is attained by the proposed equation and perfect modelling has been achieved for the masonry system.
      PubDate: Thu, 3 Jan 2013 16:23:49 GMT
       
  • Volume 13 Issue 3 - The gust wind speed duration in AS/NZS 1170.2
    • Abstract: Holmes, JD; Ginger, JD This paper discusses the rationale behind the redefinition of the design gust speed in the Australian/New Zealand Standard for Wind Actions, AS/NZS 1170.2, as one with a duration of 0.2 seconds, based on a moving average of that time. The origin of the basic gust in the Australian Standards since 1971, from the Dines anemometer, is discussed, and the relative response of that anemometer to gusts is compared with the current recording system based on cup anemometers, with digital processing including a moving average filter. The cup anemometers in the automatic weather stations (AWS), with the associated 3-second digital averaging, that have replaced the Dines in Australia, since the early 1990s, are shown to significantly attenuate the high frequency wind fluctuations, and hence record lower gust wind speeds. The correction factors provided in the paper for the post-1990 gusts should be applied by writers of future editions of the standard wishing to use AWS data. It should be noted that users of the standard will not be affected by the redefinition as there will be no changes to either the wind speeds or the shape factors.
      PubDate: Thu, 3 Jan 2013 16:22:06 GMT
       
  • Volume 12 Issue 1 - Forensic Structural Engineering Handbook - Second
           Edition [Book Review]
    • Abstract: Heywood, RJ Review(s) of: Forensic Structural Engineering Handbook - Second Edition, Edited by Robert T Ratay, McGraw-Hill Professional, United States, January 2010, 688 pp., ISBN: 9780071498845. Includes references.
      PubDate: Fri, 9 Nov 2012 12:54:55 GMT
       
  • Volume 12 Issue 1 - Ultimate Impact Resistance and Residual Toughness of
           Pre-stressed Concrete Railway Sleepers
    • Abstract: Kaewunruen, S; Remennikov, AM The pre-stressed concrete sleepers (or railroad ties), which are installed in railway track systems as the crosstie beam support, are designed to carry and transfer the wheel loads from the rails to the ground. It is well known that railway tracks are subject to impact loading conditions, which are attributable to the train operations with either wheel or rail abnormalities such as flat wheels, dipped rails, etc. These loads are of very high magnitude but short duration. In addition, there exists the potential of repeated load experience during the design life of pre-stressed concrete sleepers. Pre-stressed concrete has played a significant role in maintaining the high endurance of sleepers subjected to low to moderate repeated impact loads. In spite of the common use of pre-stressed concrete sleepers in railway tracks, their impact response and behaviour under repetitions of severe impact loads are not deeply appreciated, nor taken into consideration in design. This experimental investigation was aimed at understanding the residual capacity of pre-stressed concrete sleepers in railway track structures under ultimate impact loading, in order to develop state of the art limit states design concepts for pre-stressed concrete sleepers. A high-capacity drop weight impact testing machine was constructed at the University of Wollongong to achieve this purpose. A series of severe impact tests on in-situ pre-stressed concrete sleepers was carried out, ranging from low to high impact magnitudes. The impact energy was evaluated in relation to the drop heights. The impact-damaged sleepers were re-tested under static conditions in order to evaluate the residual fracture toughness in accordance with the Australian Standard. It was found that a concrete sleeper damaged by an impact load could possess significant reserve capacity sufficient for resisting about 1.05 to 1.10 times the design axle loads. The impact behaviour and residual fracture toughness under different magnitudes of impacts are highlighted in this paper. The effects of track environment, including soft and hard tracks, are also presented together with a discussion related to the ultimate limit states design.
      PubDate: Fri, 9 Nov 2012 12:54:55 GMT
       
  • Volume 12 Issue 1 - Studies on Composite Joints under Gravity and Lateral
           Loads
    • Abstract: Wang, AJ Composite beams are connected to steel or composite columns through various types of composite joints, which provide different degrees of flexural continuity from the columns to the composite beams. The flexural rigidities, the deformation capacities and the moment capacities of composite beam-column joints have significant effects on the structural behaviour of the semi-continuous composite beams and composite frames. Among various types of composite beam-column joints, composite joints with end-plates are most commonly used in modern composite buildings because of their high moment capacities and rotation capacities. In this paper, generalised three-dimensional finite element models are proposed to study the structural performance of practical composite joints with end-plates with the careful incorporation of the flexibility of shear connectors and tensile reinforcement. In order to ensure the general applicability of the proposed numerical models, the studies include both the composite joints in semi-continuous beams under gravity loads and the joints in sub-frames under lateral loads; and propose a generalised finite element model for the stiffness and load carrying capacity prediction of composite end-plate joints under various load cases as well. Various important structural behaviour of the composite end-plate joint is also studied through the numerical simulation.
      PubDate: Fri, 9 Nov 2012 12:54:55 GMT
       
  • Volume 12 Issue 1 - Structural Analysis and Design of Glazed Curtain Wall
           Systems
    • Abstract: Sivanerupan, S; Wilson, JL; Gad, EF Glazed curtain wall systems have been gaining popularity in recent times, and are commonly found in all types of commercial, industrial, institutional and residential buildings. The design of curtain wall fa ade systems covers aesthetic considerations, weather proofing and structural evaluation. Structurally the curtain wall is designed for in-plane and out-of-plane loads and movements. The size and the profile of the glazed curtain wall are normally specified by the architect, while the structural design is undertaken by fa ade engineers. There is very limited published literature available on the structural design for engineers especially for the design of point fixed glazed curtain wall systems. In this paper, an overview of the methodology for the design of both unitised glazed curtain wall systems and point fixed glazed curtain wall systems is presented.
      PubDate: Fri, 9 Nov 2012 12:54:55 GMT
       
  • Volume 12 Issue 1 - Effect of Lime and Fly Ash on the Strength of Cement
           Composite Mortar
    • Abstract: Wegian, FM; AlSaeid, HM; Alnaki, AA Different proportions of lime and fly ash mortars were analysed against increasing percentages of fly ash, lime as a replacement of cement, and water-to-cement lime-fly ash ratios at various ages. The study was carried out to determine the maximum permissible fly ash content and the optimum water-to-lime-fly ash ratio in order to attain required strength levels at specific ages. The study examined the variation in strength with the gradual increase in fly ash quantities to cement-lime mortars. The addition of 7.5% to 22.5% of fly ash and 2.25% to 6.75% of lime in cement mortars can increase overall mortar strength.
      PubDate: Fri, 9 Nov 2012 12:54:55 GMT
       
  • Volume 12 Issue 1 - Studies on Semi-continuous Composite Beams with
           Non-uniform Fire Protection
    • Abstract: Wang, AJ An innovative type of non-uniform arrangements of fire protection materials is proposed for efficient fire protection to semi-continuous composite beams. The fire protection is arranged according to applied bending moments and shear forces. Heavy fire protection is applied in high bending and shear regions, while relative thin or even no fire protection is applied in low bending regions. Different failure modes are identified from the results of finite element analyses under different combinations of temperature profiles in both heavily and less fire-protected regions. A simple design approach is then proposed to predict load carrying capacities of semi-continuous composite beams for each of the identified failure modes. A parametric study is conducted thereafter to optimise the arrangements of fire protection materials.
      PubDate: Fri, 9 Nov 2012 12:54:55 GMT
       
  • Volume 12 Issue 1 - Bolted and Dowelled Connections in Radiata Pine and
           Laminated Veneer Lumber Using the European Yield Model
    • Abstract: Franke, S; Quenneville, P Connections with mechanical fasteners are important for all cases of timber structures. The failure of these connections may occur in either ductile or brittle manner. For the calculation of the ductile failure strength or the load carrying capacity, the European yield model (EYM) is used in many standards and accepted as a very accurate model. In the current New Zealand timber standard NZS 3603:1993 (Standards New Zealand, 1993) and the Australian one AS1720.1-1997 (Standards Australia, 1997), the design concept for bolted or dowelled connections is not based on the EYM, and depends only on the diameter, the timber thickness and the species group. The most important parameters for the EYM are the fastener yield moment and the timber embedment strength, but embedment strength values are not available for New Zealand Radiata pine or laminated veneer lumber (LVL). To obtain the missing information and to implement the EYM into the New Zealand and Australian standards, embedment tests parallel, perpendicular and under various load-to-grain angles with different dowel diameters in Radiata pine lumber and LVL were conducted and compiled to build a database of embedment strength values. This paper includes the latest results of the investigations with dowel diameters extended up to 30 mm. Furthermore, different international testing standards are compared and their evaluation methods are used. The test results are also compared with the corresponding results using the Eurocode 5 formulas, and show that adjusted formulas of the Eurocode 5 can be used to predict the load carrying capacity of bolted and dowelled connections in Radiata pine lumber and LVL. Design examples comparing the current methods from the New Zealand/Australian design standards and the proposed method adopted from the EYM of the European design standard are given as well.
      PubDate: Fri, 9 Nov 2012 12:54:55 GMT
       
  • Volume 12 Issue 1 - Compression Strength Perpendicular to the Grain of New
           Zealand Radiata Pine Lumber
    • Abstract: Franke, S; Quenneville, P The compression strength perpendicular to the grain is one of the important timber properties for structural design. Exceeding the strength value will not only lead to large deformations and thus a serviceability issue, but it can also lead to a failure and thus a safety issue. Only some compression strength values and little information about the complete behaviour for Radiata Pine from New Zealand can be found in the literature. To correct this lack of information, tests have been conducted to investigate the compression behaviour, whereby compression strength values perpendicular to the grain much lower than the ones published in the current standard were noted. To make the designers become aware of this issue, the paper presents the experimental results of compression tests perpendicular to the grain with New Zealand Radiata Pine lumber. The test results are compared with strength values of the national and different international standards, as well as experimental research results of different species. It also gives an overview of the testing standards in use in different countries, showing the difficulty to determine a consistent strength value. According to the experimental results, the use of about half of the strength value published in the current design standard for compression perpendicular to the grain is recommended for structural sawn timber from New Zealand Radiata Pine.
      PubDate: Fri, 9 Nov 2012 12:54:55 GMT
       
  • Volume 11 Issue 3 - Comparison of the Impacts of Cyclone Tracy and the
           Newcastle Earthquake on the Australian Building and Insurance Industries
    • Abstract: Walker, G Cyclone Tracy and the Newcastle earthquake were two of the largest natural disasters to impact Australia during the past 40 years. Each was an unexpected event, they resulted in similar overall damage costs, and they both had significant impacts on the building and insurance industries. However, although extensive recommendations for changes in building practice were made in the reports on both events, Cyclone Tracy caused far greater changes in building practice than did the Newcastle earthquake. Cyclone Tracy also had a much bigger impact on the insurance industry. Another significant difference was that building costs almost doubled in Darwin following Cyclone Tracy, but hardly changed in Newcastle following the Newcastle earthquake. In respect of building practice it is suggested that the greater influence of the Commonwealth Government in Darwin at the time of Tracy was a major factor in driving the resulting Australia wide changes in building practice. In respect of the insurance industry the lessons learned from Cyclone Tracy lessened the impact of the Newcastle earthquake, although the latter was the catalyst for a major change in the way catastrophe insurance risk is assessed in Australia. The differences in post-event building costs are attributed to differences in the supply and demand for building services following the events. The analysis of comparative costs also revealed major anomalies in the current published data on the costs of both events and revised estimates of these are presented.
      PubDate: Sat, 6 Oct 2012 14:00:24 GMT
       
  • Volume 11 Issue 3 - Investigation of the Failure of the Newcastle Workers
           Club
    • Abstract: Melchers, RE The collapse of the Newcastle Workers Club during the Newcastle Earthquake in late 1989 was the subject of a Coronial Inquest, but no firm conclusions were reached. This paper describes an independent investigation of the reason(s) for the collapse. It outlines the investigation process, the data available for the investigation, eyewitness accounts not previously published, and gives a systematic overview of the progression of the investigation. It is concluded that while ground-shaking caused by the earthquake was the prime cause, failure would have been unlikely if there had not been significant deficiencies in the structure as built. These and the most likely sequence of failure events are described.
      PubDate: Wed, 3 Oct 2012 10:37:36 GMT
       
  • Volume 13 Issue 2 - Lessons on building design from the 22 February 2011
           Christchurch earthquake
    • Abstract: Goldsworthy, HM This paper summarises some key observations made after the 22 February 2011 (Christchurch) earthquake from a reconnaissance mission conducted by the author on behalf of the Australian Earthquake Engineering Society (AEES), and from other investigators. It is an updated version of a keynote paper given at the AEES annual conference in November 2011. It highlights the damage observed in reinforced concrete buildings and the effects of liquefaction. The author reflects on the adequacy of Australia's existing seismic design philosophy after reporting on the effect of a level 6.3 magnitude shallow earthquake at close range to the CBD of Christchurch.
      PubDate: Wed, 26 Sep 2012 15:12:48 GMT
       
  • Volume 13 Issue 2 - Numerical investigation into the effect of passive
           energy dissipation in low-rise structures built on soft-soil sites
    • Abstract: Chan, RWK; Zhao, Z This paper presents a study into the effectiveness of passive energy dissipation systems in low-rise structures built on soft soil sites subjected to ground motions. In this technique designated energy dissipating devices (EDDs) are installed in the structure such that a portion of the energy originated from ground shaking is diverted to. This paper focuses on displacement-based EDD whose response is highly non-linear. The governing equations of a multi-degree of freedom lumped-mass model with force-displacement non-linearity described by the Bouc-Wen model are presented. Two parameters, namely the brace-EDD assembly to frame stiffness ratios Sr and the yield drift angles γy are identified to be infl uential and a parametric study is carried out using response history analyses. Results indicate that Sr plays an important role on overall structural response, with an increase in Sr generally result in more desirable performance. On the contrary γy plays a less significant role. Results presented in this study give an insight into the preliminary selection of EDD and brace properties.
      PubDate: Wed, 26 Sep 2012 15:11:33 GMT
       
  • Volume 13 Issue 2 - An experimental and statistical analysis of the
           flexural bond strength of masonry walls
    • Abstract: Correa, MRS; Masia, MJ; Stewart, MG; Heffler, LM This paper describes an experimental program where full sized clay brick unreinforced masonry walls were constructed by masons with different levels of skills. The flexural bond strength of each joint in each wall was obtained using the bond wrench test. This provided extensive data for a statistical analysis to assess the degree of spatial correlation of that property. The analysis also included a comparison between the flexural bond strength of joints within the walls and prisms. The study recommended that flexural bond strengths between joints are statistically independent and that the commonly used prisms may not represent adequately the wall.
      PubDate: Wed, 26 Sep 2012 15:09:55 GMT
       
  • Volume 13 Issue 2 - An exact static analysis of rigidly-jointed coplanar
           beam structures subject to distributed loading
    • Abstract: Bardell, NS; Frazer, NEM A simple matrix-displacement method is presented here to facilitate the static analysis of rigidly-jointed coplanar beam frames. The geometric arrangement of the frame, the boundary conditions, the material properties, and the external loading, are allowed complete generality, thereby enabling a large range of 2D structures to be modelled. Point loads, self-weight, inertial and distributed loads may all be accommodated in the analysis; emphasis is placed on the inclusion of the distributed loads, since these prove a more significant challenge to represent accurately in a matrix-displacement type of analysis. The chief novelty of this work is that for such structures exact solutions may be obtained with great ease for the displacement, reactions, and the individual member bending moment, shear force, and axial force, through the inclusion of suitable serendipity functions in the element formulation. The computational effort is the minimum possible for this class of problem, requiring the solution to just 3S simultaneous equations, where S represents the total number of junctions or nodes used to define the frame. Such solutions can easily be implemented using desktop computing, and five examples of increasing complexity are presented herein to demonstrate the efficacy of the method.
      PubDate: Wed, 26 Sep 2012 14:59:18 GMT
       
  • Volume 13 Issue 2 - Recording inter-storey drifts of structures in
           time-history approach for seismic design of building frames
    • Abstract: Hokmabadi, AS; Fatahi, B; Samali, B The growing trend in the application of direct displacement-based or performancebased design, lays more emphasis on the precise prediction of design parameters such as the inter-storey drift controlling the performance level of the structure. Practising engineers employ different methods to record the inter-storey drifts in time-history approach mainly based on the maximum lateral deformation of the structure. In this study, a 15-storey concrete moment resisting building is designed using time-history analysis. Then reliability and accuracy of each method in predicting the maximum inter-storey drifts under the influence of three earthquake records, namely 1995 Kobe, 1994 Northridge and 1940 El Centro earthquakes, are investigated. Results clearly indicate that to choose the most critical drift to evaluate the performance level of structures, the absolute maximum drift over time should be calculated. Other methods based on the maximum storey deflection may result in unconservative design.
      PubDate: Wed, 26 Sep 2012 14:58:10 GMT
       
  • Volume 13 Issue 2 - Knee joints in cold-formed channel portal frames:
           Problems and pitfalls
    • Abstract: Mills, JE Cold-formed C-channel sections have been used in portal frame sheds for a wide range of domestic, agricultural and light industrial applications for many years in Australia and New Zealand. However, in many cases the knee joint designs have been copied from hot-rolled portal frame designs, regardless of the clearly different nature of the sections being connected. Testing has demonstrated that many of the joint designs widely used in practice do not achieve the moment capacity of the sections and fail prematurely. Various alternative joint designs have been proposed and constructed, but many of these also fail to meet required capacities under test. This paper reviews the issues relevant to design and construction of such knee joints and considers the positives and negatives of the principal categories of joints currently used in the cold-formed shed industry. It summarises the findings from a large number of tests conducted over a number of years on many of these joints. It concludes with some cautionary notes regarding what is required for design and construction if these commonly used structures are to function as intended from a structural viewpoint.
      PubDate: Wed, 26 Sep 2012 14:56:38 GMT
       
  • Volume 13 Issue 2 - Quasi-static analysis of ship structures: Recent
           advances in Australia
    • Abstract: Magoga, T Recent quasi-static analysis methods applied to ship structures presented by Australian organisations are summarised and reviewed. Areas of research have included advances in strength assessment approaches, calculation procedures, and the structural response of composites and sandwich structures. Developments in design, maintenance, monitoring, and classification society rules relevant to ship structures are also noted. Research drivers relevant to quasi-static response analysis are identified such as the increasing use of composite structures in ships, and the cost of ownership and operation of aging ships.
      PubDate: Wed, 26 Sep 2012 14:53:13 GMT
       
  • Volume 13 Issue 2 - Wind loading handbook for Australia and New Zealand:
           Background to AS/NZS 170.2 wind actions [Book Review]
    • Abstract: Walker, GR Review(s) of: Wind loading handbook for Australia and New Zealand: Background to AS/NZS 170.2 wind actions, by JD Holmes, KCS Kwok and JD Ginger, ISBN: 0975037617, 9780975037614, Australasian Wind Engineering Society, 2012, 122 pp.
      PubDate: Wed, 26 Sep 2012 14:48:03 GMT
       
  • Volume 13 Issue 1 - Research development on protection of structures
           against blast loading at University of Adelaide
    • Abstract: Wu, C This paper presents a review of research into the protection of structural members against blast loading at The University of Adelaide, including experimental, analytical and numerical studies on characteristics of blast loading, blast resistance of structural members and mitigation of blasts effects on structural members using retrofitting techniques. Explosive blasts are investigated experimentally and numerically to study the distributions of peak overpressure and impulse generated from spherical charges and cylindrical charges with different orientations in unconfined and confined environments. A series of blast tests on reinforced concrete (RC) slabs, ultra-high performance concrete (UHPC) slabs, and aluminium foam protected RC slabs was conducted to investigate the performance of those slabs under blast loads. With the blast testing data numerical models including single degree of freedom model, finite difference model and final element model, have been developed and validated and those numerical models are then used to analyse the blast effects of RC, UHPC and foam protected RC slabs. Investigation of mitigation of blast effects on masonry structures is also addressed.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 13 Issue 1 - Protection of structural systems and mechanisms from
           catastrophic and life-threatening failure caused by unforeseeable events
    • Abstract: Thambiratnam, DP; Perera, NJ Structural framing systems and mechanisms designed for normal use rarely possess adequate robustness to withstand the effects of large impacts, blasts and extreme earthquakes that have been experienced in recent times. Robustness is the property of systems that enables them to survive unforeseen or unusual circumstances (Knoll and Vogel, 2009). Queensland University of Technology with industry collaboration is engaged in a program of research that commenced 15 years ago to study the impact of such unforeseeable phenomena and investigate methods of improving robustness and safety with protective mechanisms embedded or designed in structural systems. This paper highlights some of the research pertaining to seismic protection of building structures, rollover protective structures and effects of vehicular impact and blast on key elements in structures that could propagate catastrophic and disproportionate collapse.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 13 Issue 1 - Behaviour and resistance of hollow and concrete-filled
           mild steel columns due to transverse impact loading
    • Abstract: Yousuff, M; Uy, B; Tao, Z; Remennikov, A; Liew, R This paper presents the behaviour of hollow and concrete-filled mild steel tubular columns under static and impact loading. A total of three test series have been carried out recently at the University of Western Sydney and the University of Wollongong to investigate the performance of steel hollow and concrete-filled steel tube (CFST) columns subjected to static as well as impact loading. The test results reported in this paper are from the first test series, where mild steel was used and no axial load was applied to the columns. In the next two series, the effects of a combined axial and transverse impact loads, the steel type, as well as the location of the impact loading, were considered. At the same time, steel impact property tests using a split Hopkinson's pressure bar were conducted at Hunan University, China. These test results are also reported in this paper. This paper also reports detailed results from a numerical model using ABAQUS to simulate those static and impact experiments. A non-linear finite element modelling explicit time domain dynamic approach has been used for the simulation. The main objective of this paper is to compare the performance of experimental results with numerical results for mild steel hollow and CFST columns and to provide design guidance. Moreover, the behaviour of in-filled tubes under impact loading is also compared with that of hollow sections. Generally, a reasonable level of agreement has been observed between the numerical and experimental results.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 13 Issue 1 - Protective structures research at the University of
           Melbourne
    • Abstract: Ngo, T; Lumantarna, R; Mendis, P Infrastructure engineering research at the University of Melbourne covers various subjects such as safe and sustainable structures, steel connections, high-strength concrete, earthquake engineering, dynamics of structures, and protective structures. The protective structures research group focuses on development of innovative and effective mitigation technologies for the protection of infrastructure from extreme human-caused acts and natural disasters. This paper presents the developments and future challenges in protective structures research, which falls within the scope of performance of structural components subjected to accidental or intentional blast effects, and the mitigation of these effects. The research group branches out into several key areas of interest such as performance and mitigation of structures against blast pressures, and glazing fa ade performance assessment under blast pressures. Developments of both analytical and experimental approaches in the key areas of interest will also be presented in this paper through a review of blast trials conducted in Woomera. Firstly, the loading characteristics were established in the blast trials and the analysis phase. Secondly, once the loading conditions were established the performance of local components (such as blast panels, concrete beams and fa ade components) was analysed. In this part, the performances of the modelling approach were assessed in comparison to the experimental results. The final part of this paper presents a study to establish the global behaviour of structures subjected to blast effects.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 13 Issue 1 - Research at the University of Western Australia on
           structure protections against blast and impact loads
    • Abstract: Hao, H; Ma, G One of the research focus areas of the Structural Engineering Group in the School of Civil and Resource Engineering at the University of Western Australia (UWA) is analysis and design of structures against blast and impact loads. Our research activities spread in a wide spectrum related to structure protections against blast and impact loads, including modelling shock wave propagation and prediction of blast loads on structures; quantification of dynamic material properties and development of dynamic material models; developing fibre-reinforced polymer (FRP) materials with new fibre types; development of theoretical and numerical approaches to predict blast fragmentation; numerical simulation, laboratory impact tests and field blast tests to quantify the effectiveness of FRP strengthening of reinforced concrete structures; and simulation of damage and progressive collapse of building and bridge structures to blast load. The research approaches include theoretical derivations, numerical simulations, and laboratory impact and field blasting tests. These researches are funded by a few ARC Discovery projects. Some of them are carried out with collaborations with researchers in other universities in Australia and other countries. This paper summarises a few research projects, and demonstrates the research capabilities related to protective structures in UWA.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 13 Issue 1 - Probabilistic terrorism risk assessment and risk
           acceptability for infrastructure protection
    • Abstract: Stewart, MG; Netherton, MD; Shi, Y; Grant, M; Mueller, J In the decade since the events of 9/11 there has been renewed interest in understanding the risks of terrorism, and the effectiveness of counter-terrorism measures. Since there is uncertainty associated with terrorist threats, structural and system response, effectiveness of counter-terrorism and protective measures, and terrorists' ability to inflict damage, then there is clearly a need for probabilistic approaches to assessing and mitigating terrorism risks. The paper reviews research projects related to probabilistic terrorism risk assessment and risk acceptability for infrastructure protection currently underway at The University of Newcastle. The review of probabilistic risk assessments are given for: (i) IED design and initiation, and predicting variability of time-pressure load history on infrastructure; (ii) reinforced-concrete structural systems; (iii) fullbody scanners used at airports in the United States; and (iv) buildings subject to a terrorist vehicleborne improvised explosive device. The illustrative examples will highlight research capabilities at the University of Newcastle and identify research challenges to be faced in the future.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 13 Issue 1 - Security and protective structures research in
           Australia
    • Abstract: Stewart, Mark; Hao, Hong
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 3 - A probabilistic three-dimensional finite element study
           on simply-supported composite floor beams
    • Abstract: Tahmasebinia, F; Ranzi, G; Zona, A Composite steel-concrete beams are commonly used as flooring in buildings. The composite action between slab and steel joist is typically provided by shear connectors welded to the top of the steel joist and embedded in the concrete. This paper investigates the effects of material uncertainties on the numerically simulated structural response of simply-supported beam tests reported in the literature by means of Monte Carlo simulation (MCS). The numerical analyses are performed using a three-dimensional finite element model developed using the commercial software ABAQUS and capable of predicting the response of composite steel-concrete members as well as the influence of the shear connectors without having to rely on shear connection load-slip curves obtained from push-out tests. All materials are assumed to behave in a non-linear fashion. Contact regions between the concrete and steel elements are simulated using surface-to-surface and embedment techniques. The statistical information on the structural response obtained from MCS using different realisation sizes is compared and discussed. For the particular case studies considered in this paper it can be concluded that even a reduced number of realisations can already provide meaningful statistical representations of the structural response of the considered composite floor beams.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 3 - Benchmarks for elastoplastic analysis of steel frames
    • Abstract: Petrolito, J; Legge, KA This paper proposes several benchmarks for the non-linear analysis of two-dimensional steel frames with semi-rigid joints. We present mathematical models for the frame members and the semi-rigid joints from which accurate solutions may be obtained, and delineate the simplifying assumptions that are commonly made. Various examples are considered to demonstrate the effects of different assumptions and simplifications, and accurate solutions that can serve as benchmarks are given.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 3 - Simulation of crack propagation in glass panels using
           finite element analysis
    • Abstract: Nurhuda, I; Lam, NTK; Jiang, H; Gad, EF The applicability of the discrete crack approach of finite element (FE) modelling for simulating the propagation of cracks in glass panels was investigated. Two methods of discrete analysis for crack propagation, namely the re-meshing method and node-splitting method, were considered in this investigation. The re-meshing method employs fracture mechanics theory to determine the initiation and direction of crack propagation, whereas the node-splitting method uses plastic strain as the fracture criterion. It was revealed that the re-meshing method can be used to simulate the path of crack propagation in a glass panel which is subject to out-of-plane static loading. Results from FE simulations using the re-meshing method were found to correspond well with observations from physical experimentation conducted in this research. The node-splitting method has also been studied in an attempt to simulate both the initiation and the propagation of cracks. Results were found to be sensitive to the size of the meshing.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 3 - Numerical simulation of the response of non-composite
           steel-concrete-steel sandwich panels to impact loading
    • Abstract: Kong, SY; Uy, B; Remennikov, AM Steel-concrete-steel (SCS) sandwich panels are an effective means for protecting personnel and infrastructure facilities from the effects of external blast and high-speed vehicle impact. In conventional SCS construction, the external steel plates are connected to the concrete infill by welded shear stud connectors. This paper describes a programme of research in which the non-composite SCS panels with axially restrained connections were studied experimentally and numerically. High fidelity finite element models for axially restrained SCS panels subjected to impact loading conditions were developed using LS-DYNA. The simulation results were validated against the dynamic testing experimental results. The numerical models were able to predict the initial flexural response of the panels followed by the tensile membrane resistance at large deformation. It was found that the strain rate effects of the materials and the concrete material model could have significant effect on the numerically predicted flexural strength and tensile membrane resistance of the panels.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 3 - Evaluation of dynamic generalised stress intensity
           factors at cracks and multi-material wedges using the scaled boundary
           finite element method
    • Abstract: Chiong, I; Sun, Z; Xiang, T; Song, C; Tin-Loi, F A unified definition of generalised stress intensity factors is proposed for multimaterial wedges based on the solution of the singular stress field obtained from the scaled boundary finite element method. This definition is consistent with the classical definitions for cracked problems. It is valid for real, complex and power-logarithmic singularities and avoids the breakdown of existing definitions for V-notched problems. The generalised stress intensity factors are evaluated by following standard stress recovery techniques used in the finite element method. This approach is also extended to the transient dynamic analysis of generalised stress intensity factors. The dynamic effect at high frequency is modelled by a high-order stiffness and mass matrix without internal meshing. Numerical examples are presented to verify the definition and the evaluation procedure. The simplicity and accuracy of this approach are demonstrated.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 3 - Numerical modelling of shear connection in
           steel-concrete composite beams with trapezoidal slabs
    • Abstract: Bradford, MA This paper presents a review of the numerical analysis of composite steel-concrete beams, with particular attention on the modelling of composite beams containing deep trapezoidal slabs cast onto profiled steel sheeting. It is concluded that while robust algorithms are available, there is considerable scope for improvement of these models as an alternative to undertaking expensive testing programs in order to formulate practical design procedures. This is of particular relevance to Australian practice, as timely revisions of its composite structures standard are needed.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 3 - Advanced structural analysis
    • Abstract: Petrolito, Joe
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 2 - Discussion on the "investigation of the failure of the
           Newcastle workers club" by Re Melchers
    • Abstract: Woodside, J The author, Professor RE Melchers, is to be congratulated on his paper on the investigation of the failure of the Newcastle Workers Club in 1989 in the Newcastle Earthquake. This paper should be read by all structural engineers as part of their professional development. The hypothesis of failure proposed by the author would appear to be a reasonable one and illustrates what happens with progressive collapse.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 2 - Design wind speeds for temporary structures
    • Abstract: Wang, C-H; Pham, L This note discusses various approaches to determine design wind speeds for temporary structures for Australian conditions and provides recommendations that are consistent with the regulatory approach of the Building Code of Australia (BCA). Temporary structures are defined as structures with a total period of use to perform its intended purpose less than one year. The design wind speeds for these temporary structures could be reduced up to 50% of those recommended in the BCA depending on the Importance Level.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 2 - Cyclic constitutive model for high-strength concrete
           confined by ultra-high-strength and normal-strength transverse
           reinforcements
    • Abstract: Aslani, F; Nejadi, S In this paper, a cyclic constitutive model is developed for high-strength concrete (HSC) confined by ultra-high-strength and normal-strength transverse reinforcements (UHSTR and NSTR), with the intention of providing efficient modeling for the member and structural behaviour of HSC in seismic regions. The model for HSC subjected to monotonic and cyclic loading, comprises four components; an envelope curve (for monotonic and cyclic loading), an unloading curve, a reloading curve, and a tensile unloading curve. It explicitly accounts for the effects of concrete compressive strength, Volumetric ratio of transverse reinforcement, yield strength of ties, tie spacing, and tie pattern. Comparisons with test results showed that the proposed model provides a good fit to a wide range of experimental results.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 2 - Determination of free chlorides in aggregates and
           concrete
    • Abstract: Sirivivatnanon, V; Thomas, WA; Waye, K Chlorides exist as either "bound" or "free" chloride in concrete. It is well recognised that it is the free chloride that contributes to steel depassivation and subsequent corrosion in concrete. In measuring the amount of chlorides in aggregates and concrete, both "water-soluble" and "acid-soluble (total) chloride" test methods have been used. The aggressiveness of the extractive techniques determines the type and amount of chlorides. This was investigated in terms of the type of extracting agent and degree of fractured surface of the materials. It was found that the use of boiling water on materials passing 850-micron sieve offered a well balanced measure of the free chloride contents in aggregate. The findings were also confirmed valid in testing hardened concrete.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 2 - Validation between direct displacement based approach
           and experimental work using precast hollow core wall panel
    • Abstract: Hamid, NHA Existence of hollow sections in precast hollow core wall makes it sceptical to resist earthquake loading. However, this wall can resist earthquake loading if it is designed as a hybrid wall system. It is equipped with unbonded tendons and bonded "fuse-bars" to dissipate energy. It rocks steel-on-steel without inducing any structural damages. In-plane lateral cyclic loading is applied on the wall. Experimental results show that the wall is able to resist earthquake loading without any structural damage. Direct displacement based approach is used to validate the experimental results. There are good correlations between them with very a small percentage of discrepancies.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 2 - Formulation of a genetic algorithm based methodology
           for multiple crack detection in a beam structure
    • Abstract: Parhi, DR; Dash, AK; Das, HC In the current analysis, the vibration characteristics of a cracked cantilever beam having different crack locations and depths have been studied. Numerical and finite element methods have been used to extract the diagnostic indices (natural frequencies, mode shapes) from the beam structure. An intelligent genetic algorithm based controller has been designed to automate the fault identification process. Single point crossover and mutation procedure have been followed to find out the optimal solution from the search space. The outcome from the developed controller shows that the system could not only detect the cracks but also predict their locations and severities.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 2 - Sampling factors for prototype testing of structures
    • Abstract: Wang, C-H; Pham, L This paper proposes the sampling factor for the mean test value as an alternative to that of the minimum test value of resistance for acceptance in prototype testing. The sampling factor was introduced in Australian/New Zealand loading standards AS/NZS 1170.0 to account for the uncertainties involved in prototype testing of a small number of samples to derive the characteristic properties of a much larger population. It requires the use of the minimum test value divided by a sampling factor to obtain an estimate of the 5-percentile value of the population. It is shown that while both procedures are mathematically equivalent, the use of mean value leads to more consistent estimate of the characteristic value of resistance. The sampling factors for the minimum and the mean test values are provided for Weibull and lognormal distributions by Monte Carlo simulation. This process was not feasible at the time when the original minimum value method was proposed about three decades ago.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 12 Issue 2 - Optimum design of cable-stayed bridges
    • Abstract: Yazdani-Paraei, H; Moharrami, H; Maalek, S; Heydari, M This paper is concerned with design optimisation of cable-stayed bridges. Since cable-stayed bridges, due to the presence of cables, have nonlinear elastic behaviour and optimisation algorithms require frequent nonlinear analyses, an innovative fast and easy nonlinear analysis procedure is proposed. The solution procedure is based on dividing the structure into linear and nonlinear parts and determination of unknown forces at their interface by satisfaction of equilibrium and solution of a set of nonlinear compatibility equations. The analysis procedure is completely formulated and extended to P-Δ effect included problems. The optimality criteria (OC) method is used as the optimisation algorithm. Sensitivities of objective function, displacement and stress constraints in the deck, pylon and cables, subjected to a variety of load combinations including dead and moving loads of vehicles are calculated via the proposed sensitivity analysis procedure. Numerical examples are provided to show the nonlinear analysis procedure and its applicability to the optimum design of practical cable-stayed bridges.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 3 - Seismic Hazard Estimation in Canada and Its
           Contribution to the Canadian Building Code: Implications for Code
           Development in Countries Such as Australia
    • Abstract: Adams, J Seismic design provisions of national building codes aim to save lives and reduce losses from future earthquakes. The provisions need to be based on reliable seismic hazard maps, the generation of which is a challenge in low-seismicity regions such as eastern Canada and Australia, and which contain inherently-large uncertainties. A process is needed to incorporate the hazard values into design provisions, and this is best done through continual code improvements occurring within an on-going national code committee. Building codes need to balance the benefits against the costs, and so the improvements are aided by crude risk assessments (to focus the effort where the risk is greatest) together with crude cost-benefit analyses. Most codes become more stringent to match evolving societal goals, and while the cost of increased code requirements may be strongly resisted by some groups, they may also be economically justified (present cost versus future loss). The seismic provisions of national building codes tend to focus on new, engineered 'large' buildings but may not provide comparable benefits to new 'small' buildings and are unlikely to reduce risk in existing buildings, even though damage to these may represent the major loss in moderate-magnitude urban earthquakes like the 1989 Newcastle earthquake. Additional and different strategies are therefore needed to complement existing code activities.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 3 - Effects of the Newcastle Earthquake of 1989 on the New
           South Wales High Voltage Transmission System
    • Abstract: Caldwell, R The Newcastle earthquake of 1989 had a significant effect on the New South Wales high voltage grid. Multiple failures of large, porcelain insulators and operations of transformer Bucholz relays occurred in substations near the epicentre. Although unplanned, these operations correctly initiated a general and immediate loss of supply around Newcastle, resulting in both adverse and beneficial outcomes. The Electricity Commission of New South Wales response was immediate and effective, with all bulk supply points energised after 2.5 hours. Full restoration followed in three weeks, but normal reliability of supply took months to recover. A third phase of review identified areas where either the system or the response may have been improved. 'Lifeline' studies to mitigate the effects of such extreme events are described and recommended for communities at risk.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 3 - Seismic Performance of Face Loaded Unreinforced
           Masonry Walls Retrofitted Using Post-tensioning
    • Abstract: Ismail, N; Lazzarini, DL; Laursen, PT; Ingham, JM Out-of-plane flexural testing of three full-scale unreinforced masonry (URM) walls seismically retrofitted using post-tensioning is reported. The selected wall configurations were representative of common URM walls that were vulnerable to out-of-plane failure, and imitated heritage URM construction by using salvaged clay brick masonry and ASTM type O mortar. Varying levels of pre-compression were applied to the test walls using a single mechanically restrained tendon inserted into a cavity at the centre of each test wall. Three different types of tendons were used for post-tensioning of the test walls, being threaded mild steel bar and sheathed greased seven wire strands (with tensile yield strengths of 1300 and 1675 MPa). Behaviour of the post-tensioned URM walls was compared to the response of a non retrofitted URM wall, with the out-of-plane flexural strength of the post-tensioned masonry walls observed to range from 2.9 to 10.3 times the strength of the non retrofitted URM wall. Several aspects pertaining to the seismic behaviour of post-tensioned masonry walls were investigated, including tendon stress variation, damage patterns, force displacement behaviour, initial stiffness and displacement capacity. Test results were compared with equations developed in previous studies, and it was established that the walls that were post-tensioned using seven-wire strands had measured strengths that compared favourably with predicted values, whereas the wall that was post-tensioned using mild steel bar had failed at a lower measured strength than the predicted value.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 3 - Dynamic Performance of a Brick Veneer House with Steel
           Framing
    • Abstract: Paton-Cole, VP; Gad, EF; Clifton, C; Heath, DJ; Davies, C; Hicks, S; Lam, N Brick veneer construction is a very common form for residential structures in Australia and is growing in popularity in New Zealand. The structural frame is made from steel or timber, and non-structural brick walls are attached to the frame via brick ties. Under earthquake loading there is a complex interaction between the frame and veneer walls, particularly in the outof- plane direction, where there is risk of brick wall collapse. While there is a standard component test method for assessing the seismic capacity of brick ties, this method has been developed around brick veneer on timber studs. In order to realistically assess the overall performance of brick veneer construction with steel framing, a full scale one-room test structure 'Test House' was tested on a shaking table. The Test House incorporated veneer walls with different geometries. It was subjected to varying levels of the El-Centro earthquake ranging from moderate serviceability limit state ground motion to well beyond the design maximum considered earthquake for New Zealand. These levels of shaking were selected in order to ascertain the response for specific limit states to the New Zealand Loading Standard and to compare against minimum performance requirements. Comprehensive measurements on the frame and veneer walls were taken, including acceleration, drift and differential movements between the frame and veneer. The Test House performed very well, with no brick loss up to 2.6 times El-Centro earthquake, which is well in excess of all performance requirements. This paper presents a summary of the outcomes from the experimental test program.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 3 - Twenty Years of Improvement in the Seismic Performance
           of Masonry Veneer Construction
    • Abstract: Beattie, G; Thurston, S A lot of clay has flowed through the kilns since the 1989 Newcastle earthquake. Several significant changes have occurred to make masonry veneer construction safer and stronger over this period, both in the methods of construction of the veneer and the understanding of the behaviour of the veneer panels. These changes have lead to the conclusion that masonry veneer construction can be reliably considered to provide some bracing resistance to a light timber-framed structure, even if only to resist its own inertial loads. Recent research undertaken at BRANZ has investigated the behaviour of full-scale brick veneer single- and two-storey buildings under slow static and dynamic cyclic loading. This paper describes the developments that have occurred since 1989 and this recent research that has provided the new confidence in the seismic performance of clay brick veneer.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 3 - Performance of Unreinforced Masonry Buildings during
           the 2010 Darfield (Christchurch, NZ) Earthquake
    • Abstract: Ingham, J; Griffith, M The 2010 Darfield earthquake caused extensive damage to a number of unreinforced masonry buildings. While this damage to important heritage buildings was the largest natural disaster to occur in New Zealand since the 1931 Hawke's Bay earthquake, the damage was consistent with projections for the scale of this earthquake, and indeed even greater damage might have been expected. In general, the nature of damage was consistent with observations previously made on the seismic performance of unreinforced masonry buildings in large earthquakes, with aspects such as toppled chimneys and parapets, failure of gables and poorly secured face-loaded walls, and in-plane damage to masonry frames all being extensively documented. This report on the performance of the unreinforced masonry buildings in the 2010 Darfield earthquake provides details on typical building characteristics, a review of damage statistics obtained by interrogating the building assessment database that was compiled in association with post-earthquake building inspections, and a review of the characteristic failure modes that were observed. It was observed that structures that had been seismically retrofitted appeared to perform well, with further study now required to better document the successful performance of these retrofit solutions.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 3 - Drift Demand Predictions in Low to Moderate Seismicity
           Regions
    • Abstract: Fardipour, M; Lumantarna, E; Lam, N; Wilson, J; Gad, E This paper presents results obtained from a recent study that is aimed at assessing the drift demand on buildings for a range of projected earthquake scenarios in Australia. Parameters considered that may affect the response of buildings included building height, structural systems, and mass and stiffness distributions. It has been found that, for the range of buildings studied, the maximum angle of drift is 2.6-4.4 times the maximum response spectral displacement of the earthquake divided by the building height. This can be checked against the limiting drift capacity of the building to enable various levels of damage to be predicted for given earthquake scenarios.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 3 - Drift Capacity of a Precast Soft-storey Building in
           Melbourne
    • Abstract: Wibowo, A; Wilson, JL; Gad, EF; Lam, NTK; Collier, P Experimental field testing of a soft-storey building in Melbourne has been undertaken. The soft-storey open ground floor was a precast concrete frame with connections significantly weaker than the members they connected. Four unique tests were conducted with combination between load directions (strong and weak) and restraints of ground slab (with or without ground slab). Displacement measurements undertaken using a number of contemporary techniques are described together with results from ambient vibration testing of the building. The experimental results showed that soft-storey columns had significant displacement capacity controlled by the column width irrespective of strength degradation. An analytical model developed to predict the force-displacement relationship of the tested frame including the influences of connection strength at column ends, gravity rocking strength and ground slab restraint are briefly described and compared with the experimental results.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 3 - Seismic Design
    • Abstract: Wilson, John L; Jordan, Bill
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 2 - Strength Analysis of Fibrous Ferrocement Concrete and
           Effect of Using Superplasticiser
    • Abstract: Wegian, FM Fibre-reinforced concrete (FRC) and ferrocement concrete have been utilised in construction practices for many years. However, limitations with respect to their strength and constructability have restricted their use. Fibrous ferrocement concrete, which is the combination of the FRC and ferrocement concrete, can overcome most of these limitations. This paper presents the results of an experimental investigation on fibrous ferrocement concrete. The compressive strength, flexural strength and impact resistance of fibrous ferrocement concrete are compared with fibrous, as well as with ferrocement, concrete. The results show that the increase of fibre content increases the compressive, flexural and impact strength of the fibrous ferrocement concrete. Similarly, the addition of number of chicken wire mesh layers also improves these strengths. The addition of superplasticisers also improves the workability of fibrous ferrocement concrete.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 2 - Out-of-Plane Bending of Masonry Walls with
           Near-surface Mounted and Externally Bonded Reinforcement
    • Abstract: Fam, A; Shaat, A; MacDougall, C; Chidiac, SE This paper presents an experimental investigation into the flexural behaviour of masonry walls that have been reinforced using near-surface mounted (NSM) or externally bonded (EB) reinforcement, under out-of-plane loading. The study simulates retrofitting applications and also proposes the NSM technique for new wall construction, using pre-grooved blocks, in lieu of the conventional method of internal reinforcing and grouting. To accommodate the NSM reinforcement, the grooves in the masonry blocks were aligned with ducts used to anchor the NSM reinforcement in the concrete footing. Seven wall specimens were tested, including walls reinforced with conventional and stainless steel bars, glass fibre-reinforced polymer (GFRP), and carbon FRP (CFRP) reinforcement. The study demonstrated the feasibility and effectiveness of the NSM technique for new construction. Walls with NSM reinforcement showed a superior performance to those with EB reinforcement. It was shown that increasing the FRP reinforcement ratio may result in a change of failure mode, and as such, the increase in strength may not be proportional to the increase in reinforcement ratio. NSM steel reinforced walls showed a superior performance in terms of strength, stiffness and the ductility associated with the formation of a plastic hinge at the base.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 2 - Investigation of Bond Strength and Flexural Behaviour
           of FRP-strengthened Reinforced Concrete Beams Using Cement-based Adhesives
           
    • Abstract: Hashemi, S; Al-Mahaidi, R Retrofitting of structures has become a major issue worldwide due to increases in the applied loads, human error in initial construction, legal requirement to comply with updated versions of existing codes, or the loss of strength due to deterioration over time. In this regard, fibrereinforced polymer (FRP) retrofitting systems are enjoying a great deal of popularity as a result of the unique properties of FRPs. Retrofitting with epoxy-bonded FRP composites is suitable for environments where the temperature is well below the glass transition temperature (Tg) of the epoxy adhesive. Tg is normally in the range of 55-60 C (fib, 2001; Saafi, 2002). It would be very beneficial if it is replaced with cementitious (mineral) based bonding agents in order to produce fire-resistant strengthening systems. Pilot testing conducted by the authors has shown that excellent bonding properties can be achieved using the cement-based adhesives (Hashemi and Al-Mahaidi, 2009). Test results were applied for the next stage of the project presented in the current paper. Tests include the investigation of bond strength of FRP fabrics to the concrete substrate by single-lap shear test and flexural behaviour of FRP-strengthened reinforced concrete beams using cement-based adhesives. The bond-slip response has been developed for the strengthening system. It is concluded that using cement-based bonding materials is a promising technique in FRP applications for structures located in hot regions or in danger of fire.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 2 - Innovative Strengthening Technique Using
           Post-tensioned Fibre Composite Wraps for Bridge Headstocks
    • Abstract: Aravinthan, T; Heldt, T Engineered fibre composites offer an extremely versatile option to strengthen existing structures to solve structural problems arising from environmental exposure, inadequate designs, increased traffic loads and continuous aging of existing structures. While the behaviour of structures by external post-tensioning using fibre composites for flexure is well understood, there is limited research on shear strengthening, specifically using pre-stressed fibre composites. An innovative system using fibre composites has been investigated for strengthening bridge headstocks with deficient structural performance. The innovative system uses fibre composite wraps that forms an infinite loop around the headstocks and together with anchorage blocks, these are pushed-out and the gap packed with a suitable spacer to maintain the applied pre-stressing force. This paper discusses the research, development and construction of this innovative fibre composite post-tensioning system, and testing it on a model bridge headstocks in Tenthill Creek Bridge. Issues related to the effect of existing shear cracks and the importance of repairing such cracks will be discussed. With further investigation, this strengthening system could be implemented in actual structures to enhance the capacity of bridge headstocks.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 2 - Strength Design Equations for FRP-strengthened
           Concrete Beams
    • Abstract: Rasheed, HA; Motto, NH Externally-bonded fibre-reinforced polymer (FRP) has been established as the technology of choice to strengthen reinforced concrete beams. Researchers and practicing engineers have recently developed design guidelines for FRP strengthening. However, the current state of the art flexural design procedure suggests an iterative process. No earlier efforts have been devoted to develop direct strength design equations on the failure modes of FRP rupture and delamination that can facilitate structural calculations. This study develops exact and approximate sets of closed form equations to design singly- and doubly-reinforced strengthened rectangular sections that fail by FRP rupture or cover delamination. Comparisons with reported experimental strength data indicate excellent agreement. A comprehensive parametric study, including flat and wrapped FRP sheets and laminates, has yielded a simple linear equation that has an almost perfect statistical correlation, and is equally applicable to analysis and design. The equation is found to be unique regardless of the height of the wrapped side of FRP flexural sheets.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 2 - Numerical Modelling of Shear Crack Angles in FRP
           Shear-strengthened Reinforced Concrete Beams
    • Abstract: Godat, A; Labossiere, P; Neale, KW The shear crack angle is a key parameter in the calculation of the fibre-reinforced polymer (FRP) contribution to the shear capacity of a shear-strengthened reinforced concrete beam. In this study, a new approach is developed to estimate the shear crack angles for such a beam. The approach is based on the FRP/concrete interface response. A non-linear finite element model was developed to simulate the behaviour of six beams grouped in three sets according to their dimensions. One unstrengthened beam of each set was used as a benchmark and its behaviour was compared to that of a beam strengthened with a U-wrap scheme. It was found that the numerical model is able to successfully simulate the behaviour of the shear-strengthened beams. The numerical predictions compare very well with previously published experimental data in terms of load-deflection relationships and carbon FRP (CFRP) axial strain profiles along the sheet length. The analysis of the slip profiles along the CFRP strip is helpful to understand the bond behaviour between the concrete and CFRP strips. The interfacial slip profiles are used to predict the shear crack angle along the shear span, and these predictions agree very well with the experimental measurements. The numerical results give failure modes that are identical to those obtained experimentally.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
  • Volume 11 Issue 2 - Deflection Calculation of FRP-strengthened Reinforced
           Concrete Flexural Members
    • Abstract: Smith, ST; Kim, SJ Externally bonded fibre-reinforced polymer (FRP) composite plates can enhance the flexural strength, as well as stiffness to a limited degree, of reinforced concrete (RC) flexural members. Understanding the behaviour of these strengthened members at the serviceability and ultimate load ranges of response is of particular importance to engineers. The description of such behaviour is best described via plotting of the complete moment-curvature, as well as load-deflection responses from initial load to member failure. Based on the assumption of a tri-linear momentcurvature relationship, closed-form analytical solutions are presented in this paper for calculating the complete load-deflection response of FRP flexurally-strengthened one-way RC slabs and beams, which are simply-supported (three- and four-point bending), as well as cantilevered (free-end point load). The analytical predictions compare well with test results and the basis of a new "quad-linear" moment-curvature relationship is proposed that may better capture a so-called "pseudo-ductile" response occasionally observed in experiments. The influence of anchorage of the FRP strengthening for the prevention or delaying of debonding and a procedure for its inclusion in the analytical model is also discussed. Finally, the results of parametric studies are presented.
      PubDate: Tue, 19 Jun 2012 12:30:11 GMT
       
 
 
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