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Journal Cover Australian Journal of Structural Engineering
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   Full-text available via subscription Subscription journal
   ISSN (Print) 1328-7982
   Published by RMIT Publishing Homepage  [403 journals]
  • 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
    • 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 - Behaviour of tall buildings and structures in strong
           winds: Dynamic properties, response characteristics and vibration
    • 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 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 - 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 - 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 - Preventing failure through the management of
    • 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 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 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
    • 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
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