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Journal Cover Australian Journal of Structural Engineering
   [6 followers]  Follow    
   Full-text available via subscription Subscription journal
     ISSN (Print) 1328-7982
     Published by RMIT Publishing Homepage  [415 journals]   [SJR: 0.347]   [H-I: 6]
  • Volume 15 Issue 4 - Strengthening of metallic and concrete structures
           using fibre-reinforced polymer composites
    • Abstract: Al-Mahaidi, Riadh
      PubDate: Mon, 3 Nov 2014 11:00:24 GMT
       
  • Volume 15 Issue 4 - Some issues on the strengthening of steel structures
           with fibre-reinforced polymer materials
    • Abstract: Bocciarelli, M; Colombi, P; Fava, G; Poggi, C Fibre-reinforced polymer (FRP) materials are widely accepted in the strengthening of civil engineering structures due to their unique characteristics such as high mechanical properties, low dead weight and very good corrosion resistance. In particular the use of FRP materials for strengthening concrete structures was deeply investigated in the past. More recently the use of FRP materials was also proposed in the strengthening of timber, masonry and steel structures. Several studies have been conducted in the literature on the reinforcement of steel structures by FRP materials. They include bond strength, flexural and fatigue reinforcement, strengthening against local buckling and durability aspects. Future research should be conducted in order to propose more reliable design guidelines and to finally increase the acceptance in practice of this reinforcement technique. This paper illustrates some issues on the strengthening of steel structures with FRP materials starting from previous works from the authors. The paper starts with a discussion on the benefits and drawbacks in the use of FRP materials in the reinforcement of steel structures. Then some issues concerning the reinforcement of steel structures are illustrated. They include bond behaviour between steel and FRP, flexural strengthening of steel beams including the post-yielding behaviour and bond durability under mechanical (fatigue) and environmental actions.
      PubDate: Mon, 3 Nov 2014 11:00:24 GMT
       
  • Volume 15 Issue 4 - The effect of elevated temperature on the bond between
           high modulus carbon fibre-reinforced polymer sheet and steel
    • Abstract: Liu, HB; Zhao, XL; Bai, Y; Raman, RK Singh; Rizkalla, S; Bandyopadhyay, S The technique of strengthening steel structures with carbon fibre-reinforced polymer (CFRP) has attracted growing attention in research field and in practice, and thus, its environmental durability is of high importance. This paper describes an investigation on the bond characteristics between high modulus CFRP sheets and steel plates under elevated temperature exposures. Tensile tests were carried out on CFRP/steel plate double strap joints at different temperatures (20, 40 and 50 degreesC) that represent the usually encountered conditions for civil infrastructure. High modulus (640 GPa) unidirectional carbon fibre sheets were applied by wet lay-up fabrication method. The fracture surfaces of the failed specimens were studied using a scanning electron microscope and the failure mechanisms were discussed. It was found that the ultimate load decreased significantly when the test temperature was above the glass transition temperature of the adhesive. Larger effective bond lengths were found for the joints tested at the glass transition temperature. It is obvious that the short-term thermal exposure has little effect on their failure patterns. All the specimens failed by fibre breakage at the joint and decohesion accompanied some joints with very short bond length.
      PubDate: Mon, 3 Nov 2014 11:00:24 GMT
       
  • Volume 15 Issue 4 - Enhancement of steel/carbon fibre-reinforced polymer
           adhesively-bonded joints at elevated temperatures through curing
    • Abstract: Bai, Y; Nguyen, T-C; Al-Mahaidi, R; Zhao, X-L Although carbon fibre-reinforced polymer (CFRP) a promising approach to the strengthening of existing steel structures, such an adhesively-bonded system exhibits a significant loss of stiffness and strength in an elevated temperature range. Curing at elevated temperature is examined in this paper, in order to enhance the mechanical performance in the elevated temperature range. Two types of epoxies - with and without carbon nanotube (CNT) modification - were used to prepare steel/CFRP adhesively-bonded joints and both were cured at room temperature (20 degreesC) and at an elevated temperature (80 degreesC), and then tested in tension at temperatures from 20 to 80 degreesC. Remarkable enhancement of stiffness and strength was found for the joints, with or without CNT modification, cured at the elevated temperature, compared to corresponding joints cured at room temperature. The partial safety factors used for laminates by hand lay-up were further evaluated for designing such joints under elevated temperatures.
      PubDate: Mon, 3 Nov 2014 11:00:24 GMT
       
  • Volume 15 Issue 4 - Analysis of adhesive joints between fibre-reinforced
           polymer laminates and structural steel members
    • Abstract: Haghani, R Over the past three decades, fibre-reinforced polymer (FRP) materials have gained a lot of attention in construction especially in the field of infrastructure. The attractiveness of FRP materials is mainly due to their superior mechanical properties such as high specific strength and stiffness, light weight and good fatigue and durability characteristics. The most common applications of FRP materials have been in strengthening and repair of existing structures. Using FRP composites for concrete strengthening and repair has been well researched and documented. However, when it comes to steel structures, the application of FRP materials is somewhat limited. One of the main reasons is the lack of accurate design models for adhesive joints between FRP and steel members. Issues such as the complexity of failure modes and the lack of knowledge of the force transfer mechanism are obstacles that contribute to the difficulty associated with developing accurate design models. This paper deals with analysis of adhesive joints used to bond carbon FRP laminates to steel substrates using a numerical and experimental approach. A numerical model of the studied joint configuration has been developed utilising the finite element method, while, an optic measurement technique has been used to experimentally verify the numerical results. Several classical failure criteria used for design of adhesive joints have been studied to examine their applicability and accuracy in predicting the failure load of the specimens. Different aspects of joint behaviour, such as strain distribution along the bond line and through the thickness of the adhesive layer and failure mechanisms are discussed and conclusions with regard to design of such joints are presented.
      PubDate: Mon, 3 Nov 2014 11:00:24 GMT
       
  • Volume 15 Issue 4 - Durability performance of carbon fibre-reinforced
           polymer strengthened circular hollow steel members under cold weather
    • Abstract: Kabir, MH; Fawzia, S; Chan, THT; Gamage, JCPH The use of circular hollow steel members has attracted a great deal of attention during past few years because of having excellent structural properties, aesthetic appearance, corrosion and fire protection capability. However, no one can deny the structural deficiency of such structures due to reduction of strength when they are exposed to severe environmental conditions such as marine environment, cold and hot weather. Hence strengthening and retrofitting of structural steel members is now very imperative. This paper presents the findings of a research program that was conducted to study the bond durability of carbon fibre-reinforced polymer (CFRP) strengthened steel tubular members under cold weather and tested under four-point bending. Six number of CFRP-strengthened specimens and one unstrengthened specimen were considered in this program. The three specimens having sand blasted surface to be strengthened was pre-treated with MBrace primer and other three were remained untreated and then cured under ambient temperature at least four weeks and cold weather (3 C) for three and six months period of time. Quasi-static tests were then performed on beams to failure under four-point bending. The structural response of each specimen was predicted in terms of failure load, mid-span deflection, composite beam behaviour and failure mode. The research outcomes show that the cold weather immersion had an adverse effect on durability of CFRP-strengthened steel structures. Moreover, the epoxy based adhesion promoter was found to enhance the bond durability in plastic range. The analytical models presented in this study were found to be in good agreement in terms of predicting ultimate load and deflection. Finally, design factors are proposed to address the short-terms durability performance under cold weather.
      PubDate: Mon, 3 Nov 2014 11:00:24 GMT
       
  • Volume 15 Issue 4 - Reinforced-concrete beams retrofitted in shear with
           
    • Abstract: Mofidi, A; Chaallal, O This paper presents the results of a theoretical study of the parameters that affect the contribution of fibre-reinforced polymer (FRP) composite to the shear resistance of reinforcedconcrete (RC) beams retrofitted in shear. To assess and analyse the variables that have the most signifi cant effect on the shear resistance of RC members strengthened with externally-bonded (EB) FRP, the results of available studies reported in the literature are used. In addition to variables related to the mechanical properties of FRP and internal transverse steel reinforcement, the following influential parameters on the shear contribution of FRP are assessed in this study: (i) the shear span ratio; (ii) the longitudinal-steel reinforcement ratio; (iii) the compressive strength of concrete; and (iv) the failure mode of RC beams shear-strengthened with EB FRP. This study shows that the effect of steel stirrups on the shear contribution of FRP is significant. However, the steel stirrups effect is not taken into consideration in existing codes and guidelines. In this paper, a design method is proposed that considers the effect of steel stirrups in addition to other influential parameters on the contribution of FRP to the shear resistance. Comparison with current design guidelines reveals that the proposed model achieves a better correlation with experimental results than current design codes and guidelines.
      PubDate: Mon, 3 Nov 2014 11:00:24 GMT
       
  • Volume 15 Issue 3 - A study on the elephant-foot bulge formation of
           anchored steel tanks
    • Abstract: Elkashef, M; Rashed, A; Haroun, M Elephant-foot buckling, characterised by an axisymmetric shell bulging adjacent to the base support, constitutes one of the main modes of failure in seismically-excited steel tanks and in most cases results in loss of tank contents due to weld or piping connection damage or may lead to total collapse of the tank. Current design codes deal with this mode of failure as a buckling failure and hence calculate an allowable buckling stress and compare it to the axial stress in the shell. Recent earthquake incidents have shown a compelling need to revise these codes. In this paper, an analytical study is performed using non-linear finite element modelling to investigate this mode of failure. A quasi-static hydrodynamic load is applied to the tank walls simulating the effect of the accelerated contained liquid. The elephant-foot buckling phenomenon was shown to correlate closely with the yielding of the steel shell as indicated by the Von Mises stress. A new design methodology is introduced using the Von Mises stress and an example is presented to illustrate this approach. A detailed analysis is also presented to estimate the location of the elephant-foot bulging failure for existing tanks which could serve as an aid in the process of repairing these tanks.
      PubDate: Fri, 19 Sep 2014 16:45:21 GMT
       
  • Volume 15 Issue 3 - Flexural toughness characteristics of self-compacting
           concrete incorporating steel and polypropylene fibres
    • Abstract: Aslani, F; Samali, B Fibre-reinforced self-compacting concrete (FRSCC) is a relatively new composite material which congregates the benefits of the SCC technology with the profits derived from the fibre addition to a brittle cementitious matrix. Fibres improve many of the properties of SCC elements including tensile strength, ductility, toughness, energy absorption capacity, and fracture toughness. Although the available research regarding the influence of fibres on the properties of FRSCC is limited, this paper investigates the fl exural toughness characteristics of SCC incorporating steel and polypropylene fibres. An extensive experimental program is carried out to monitor and record the flexural strength of SCC and FRSCC prism specimens under four point static flexural loading. For this purpose, four different SCC mixes including plain SCC, steel, polypropylene, and hybrid FRSCC mixes are considered in the test program. The flexural strength was tested after 3, 7, 14, 28, 56, and 91 days. The fl exural toughness parameters were obtained using procedure laid down in ASTM C 1018, JSCE, Banthia and Trottier and ACI 544 methods.
      PubDate: Fri, 19 Sep 2014 16:45:21 GMT
       
  • Volume 15 Issue 3 - Time-dependent deflection of composite concrete slabs:
           A simplified design approach
    • Abstract: Gholamhoseini, A; Gilbert, I; Bradford, M Relatively little research has been reported on the time-dependent in-service behaviour of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. Based on an existing analytical model developed by the authors to calculate the time-dependent deflection of composite slabs, a simplified procedure, suitable for use in structural design, is proposed for calculating the time-dependent deflection of composite concrete slabs that takes into account the time-dependent effects of creep and shrinkage. The method is illustrated by three examples and the results are compared with experimental data.
      PubDate: Fri, 19 Sep 2014 16:45:21 GMT
       
  • Volume 15 Issue 3 - An evaluation of design code expressions for
           estimating in-plane shear strength of partially grouted masonry walls
    • Abstract: Hassanli, R; ElGawady, MA; Mills, JE This paper aims to evaluate the in-plane shear strength expressions of partially grouted masonry (PGM) walls in four international design codes, including masonry design codes of practice in the United States, New Zealand, Canada and Australia. Experimental results of 89 partially grouted masonry walls that displayed shear failure were collected from published research. The shear strengths of the walls in the database were calculated using the different code equations and compared with those from the experimental results. In addition, the parameters that influence the shear strength of the walls, including masonry tensile strength, level of axial compressive stress, wall aspect ratio, and the amount and spacing of vertical and horizontal reinforcement are studied. Both univariate and multivariate regression analysis have been employed to investigate the effect of each parameter on the accuracy of the code shear strength predictions. This study illustrates poor correlation between code predictions and test results, indicating that current codes are unable to predict the shear strength of PGM walls. In some cases the code shear strength predictions are three to four times the experimentally measured shear strength, indicating that modifications are needed as the current provisions are unconservative. An equation is therefore proposed which better estimates the strength of PGM walls.
      PubDate: Fri, 19 Sep 2014 16:45:21 GMT
       
  • Volume 15 Issue 3 - Preface
    • Abstract: Wilson, John; Gad, Emad; Pham, Lam
      PubDate: Fri, 19 Sep 2014 16:45:21 GMT
       
  • Volume 15 Issue 3 - Creep in prestressed concrete beams under time-varying
           sustained loading
    • Abstract: Warner, RF In the design of prestressed concrete flexural members it is necessary to allow for the long-term effects of creep and shrinkage, particularly in regard to deflections and prestress loss. Various analytic methods can be used to evaluate these long-term effects, but the calculations for creep become extended and complex if, as is usually the case, the sustained load on the member varies over time. In this study a simplified, approximate method is proposed for dealing with creep under a varying load history. The time-varying moment history in the cross-section of a member is replaced by a constant, sustained, "equivalent" moment, Meq, which has the same long-term effect as the time-varying moment. This equivalent moment can be used together with any appropriate constant-moment creep analysis, but is here combined with previously-derived, closed-form expressions for loss of prestress and creep curvature. The result is a simple procedure for dealing with creep in prestressed members under time- varying sustained loads.
      PubDate: Fri, 19 Sep 2014 16:45:21 GMT
       
  • Volume 15 Issue 3 - Simple hand calculation method for estimating
           deflection generated by the low velocity impact of a solid object
    • Abstract: Ali, M; Sun, J; Lam, N; Zhang, L; Gad, E Codified provisions for estimating impact actions in contemporary codes of practices are convenient to apply but lack generality given that parameters associated with the inertia resistance of the target have not been incorporated into the provisions. This paper introduces algebraic expressions for estimating the maximum deflection of a structural member when subject to the hard impact action of a flying, or fallen, impactor (or projectile). Once the deflection value is known the equivalent static force value can accordingly be found by calibration. The proposed hand calculation model which is aimed at supporting the design and assessment of structures has been verified by comparative analyses involving physical experimentations and computer simulations. Meanwhile, limitations of the proposed model have also been identified.
      PubDate: Fri, 19 Sep 2014 16:45:21 GMT
       
  • Volume 15 Issue 1 - Reinforced concrete: The designers handbook [Book
           Review]
    • Abstract: Bradford, MA Review(s) of: Reinforced concrete: The designers handbook, by AS Beletich, ID Hymas, SG Reid and PJ Uno, APN: 9780646594859, Cement and Concrete Services, 2013, 910 pp.
      PubDate: Mon, 25 Aug 2014 16:47:27 GMT
       
  • Volume 15 Issue 1 - The Cave Creek tragedy, New Zealand, 1995: A
           structural and systemic failure
    • Abstract: Bowling, T In April 1995 a viewing platform near the Paparoa National Park in the South Island of New Zealand collapsed sending 17 students from a Greymouth polytechnic and a national park ranger into the 30 m deep Cave Creek gorge. Thirteen students and the park ranger died. The New Zealand government set up a Commission of Inquiry into the collapse. The report of this Commission found that the primary cause of the collapse was that the platform was not constructed in accordance with sound building practice. However the Commission also found six secondary causes of the collapse, the underlying one being that there was no proper project management system in the government department responsible for the construction of the viewing platform. The paper details the findings of the Commission of Inquiry with respect to the structural failure of the platform and the systemic failure within the New Zealand Department of Conservation at the time.
      PubDate: Mon, 25 Aug 2014 16:44:34 GMT
       
  • Volume 15 Issue 1 - Mitigating footfall-induced vibration in long-span
           floors
    • Abstract: Nguyen, T; Gad, E; Wilson, J; Haritos, N Long-span lightweight floor systems with low damping are susceptible to serviceability problems due to human excitations. This paper discusses two remedial measures to alleviate disturbing footfall-induced vibrations observed on a real office floor of steel-concrete composite construction. One treatment involves stiffening the existing floor beams while the other utilises passive control with an innovative distributed multiple viscoelastic tuned mass damper (TMD) system. Several finite element models reflecting different remedial scenarios are analysed from which the TMD approach and the traditional stiffening technique are found to be comparably effective in reducing the vibration level. However, the proposed TMD solution is far superior, feasible and non-intrusive when applied to existing floors. A probability-based evaluation of the effectiveness of the TMD system is also conducted, taking into account likely variations in the walking force and dynamic properties of both the floor and dampers. The custom-made damper system has been successfully installed on the real floor and performed efficiently in various field tests.
      PubDate: Mon, 25 Aug 2014 16:43:01 GMT
       
  • Volume 15 Issue 1 - Seismic analysis of precast segmental bridge piers of
           the Hunter Expressway viaducts and the proposed amendment to bridge code
           AS5100.2
    • Abstract: Pokharel, HP The method of deriving the seismic design force in the current Australian bridge design code AS5100.2-2004 is force based and requires the use of a structural response factor Rf which is not defined for a structural system consisting of precast segmental concrete piers. There is an initiative to amend the current bridge design code to make it compatible with the changes made in AS1170.4-2007. The initiative also includes displacement based design method as an alternative to the current force based design method. This approach is new in the Australian design offices and there is a need to assess the impact these amendments will create. This paper details the workings of a performance based analysis to derive the seismic horizontal design force for the precast segmental concrete piers which meets the design requirements of the current bridge design code without using Rf. The effect of changes in AS1170.4-2007 and the outcome of implementing displacement based design method in the design of the precast pier have been discussed. The design feature of the Hunter Expressway viaducts which was developed to meet the requirements of AS5100.2-2004 is used to compare the effect of such proposed changes.
      PubDate: Mon, 25 Aug 2014 16:39:06 GMT
       
  • Volume 15 Issue 1 - Structural damage detection using the polynomial
           annihilation edge detection method
    • Abstract: Surace, C; Yan, G; Archibald, R; Saxena, R; Feng, R It is well-known that damage in a structure may cause a discontinuity in mode shapes or their derivatives, which has been used as a basis for some damage detection approaches. However, if the severity of damage is small, the discontinuity will be difficult to be detected. The polynomial annihilation edge detection method improves the accuracy of localising discontinuity in a function by determining intervals of smoothness in the function. The feasibility of this edge detection method in localising and quantifying cracks in a cantilevered beam has been demonstrated (Surace et al, 2013). This study is to further validate this edge detection method on various types of structures and damages using numerical simulations. First, this method is performed on a cantilever aluminium bar under longitudinal vibrations to localise and quantify cracks; then, it is performed on a simply supported steel beam to detect cracks. Finally, this method is applied to a more complicated structure, a cable-stayed bridge model, to localise the damage occurring in girders.
      PubDate: Mon, 25 Aug 2014 16:33:12 GMT
       
  • Volume 15 Issue 1 - Effects of wireless sensor network uncertainties on
           output-only modal-based damage identification
    • Abstract: Nguyen, T; Chan, THT; Thambiratnam, DP The use of wireless sensor networks (WSNs) for structural health monitoring (SHM) has become a promising approach due to many advantages such as low cost, fast and flexible deployment. However, inherent technical issues such as data synchronisation error and data loss have prevented these distinct systems from being extensively used. Recently, several SHMoriented WSNs have been proposed and believed to be able to overcome a large number of technical uncertainties. Nevertheless, there is limited research examining effects of uncertainties of generic WSN platform and verifying the capability of SHM-oriented WSNs, particularly on demanding SHM applications like modal analysis and damage identification of real civil structures. This article first reviews the major technical uncertainties of both generic and SHM-oriented WSN platforms and efforts of SHM research community to cope with them. Then, effects of the most inherent WSN uncertainty on the first level of a common output-only modal-based damage identification (OMDI) approach are intensively investigated. Experimental accelerations collected by a wired sensory system on a benchmark civil structure are initially used as clean data before being contaminated with different levels of data pollutants to simulate practical uncertainties in both WSN platforms. Statistical analyses are comprehensively employed in order to uncover the distribution pattern of the uncertainty influence on the OMDI approach. The result of this research shows that uncertainties of generic WSNs can cause serious impact for level 1 OMDI methods utilising mode shapes. It also proves that SHM-WSN can substantially lessen the impact and obtain truly structural information without having used costly computation solutions.
      PubDate: Fri, 22 Aug 2014 09:11:56 GMT
       
  • Volume 15 Issue 1 - Implementation of Elman neural networks for enhancing
           reliability of integrated bridge deterioration model
    • Abstract: Bu, GP; Lee, JH; Loo, YC; Blumenstein, M; Guan, H Probabilistic modelling is one of the most prominent techniques in bridge deterioration forecast. It can be classified into two types, namely, state- and time-based models. Reliability of both modelling techniques in forecasting long-term performance rely heavily on sufficient amount of bridge condition rating data being available together with well-distributed deterioration pattern over the age of bridge. However, it can be problematic when the available condition rating records are insufficient. In order to overcome this problem, an integrated deterioration method incorporating both the state- and time-based models has recently been developed. Despite such development and advancement, certain issues still remain with some cases of given condition data that cannot be used to produce reliable long-term performance curve. Aiming to achieve enhanced prediction performance, an Elman neural networks (ENN) technique is incorporated in the integrated method to replace the third-order polynomial regression function, the latter being the core component for long-term prediction in the state-based model. In the present study, the ENN are able to generate more reliable deterioration patterns than a typical deterministic method. The results demonstrate that the integrated method incorporating ENN are more effective in handling various situations of condition data quantities and distributions for generating long-term performance curves.
      PubDate: Fri, 22 Aug 2014 09:11:56 GMT
       
  • Volume 15 Issue 1 - Application of Bayesian-designed artificial neural
           networks in Phase II structural health monitoring benchmark studies
    • Abstract: Ng, C-T This paper presents the results of a study into the use of pattern recognition as a method for detecting damage in structures. Pattern recognition is achieved by the use of artificial neural networks (ANNs), however, these require careful design because the number of hidden layers and the number of neurons in each hidden layer are critical to the ANN's performance. In the current study, a Bayesian model class selection method was employed to select an optimal ANN model class that avoids ad hoc assumptions and subjective decisions in the ANN design. The objective of the research was to provide an extended study of the proposed method using the IASC-ASCE Structural Health Monitoring Phase II Simulated Benchmark Structure. Damage-induced modal parameter changes were used as a pattern feature in damage detection. Analysis showed that the proposed method is able to successfully identify damages in the benchmark structure.
      PubDate: Fri, 22 Aug 2014 09:11:56 GMT
       
  • Volume 15 Issue 1 - Rheological properties and compressive strength
           behaviour of polyvinyl alcohol fibre-reinforced concrete
    • Abstract: Noushini, A; Vessalas, K; Samali, B Comprehensive experiments were carried out to assess the effects of uncoated polyvinyl alcohol (PVA) fibres of two geometric lengths (6 and 12 mm) on the fresh and hardened properties of concrete. Fly-ash was also used as partial replacement of Portland cement in all mixes. Based on total concrete volume, four fibre fractions of 0.125%, 0.25%, 0.375% and 0.5% were evaluated for their effect on slump, compacting factor, air content, mass per unit volume, compressive strength, relative strength with age and mode of failure in PVA fibre-reinforced concretes (FRCs). PVA fi bres were observed to decrease the slump and mass per unit volume of FRC, while increasing the compressive strength up to 56 days ageing. With regards to workability and compressive strength, optimum fibre addition was established for 0.25% PVA-FRC incorporating 6 mm fibres with a 12% increase noted in compressive strength compared to the control concrete at 28 days ageing.
      PubDate: Fri, 22 Aug 2014 09:11:56 GMT
       
  • Volume 15 Issue 1 - Simplified analysis of creep in prestressed concrete
           beams
    • Abstract: Warner, RF This paper describes a simple, step-by-step method for evaluating long-term creep effects in prestressed concrete beams. The method has also been used in a parallel study of shrinkage in prestressed slabs and beams. By introducing several simplifying assumptions into a one-step analysis, approximate, closed-form equations are derived for the loss of prestress and the curvature in a prestressed concrete beam section due to long-term creep. The long-term creep curvature is obtained by applying a correction term to the free creep curvature, which is the initial elastic curvature multiplied by the long-term creep coefficient. This correction allows for the restraining effect of the tendon and the reinforcing steel on concrete creep in the section. Creep deflections are obtained by integrating creep curvatures in key cross-sections. A numerical study shows that corrections to the free creep curvature of up to about 30% are needed to account for the presence of the reinforcing steel and tendon. This suggests that the free creep curvature is adequate for many preliminary design calculations, and for detailed calculations where the design is not deflectionsensitive. The calculations also show that reinforcement has an important effect on loss of prestress and long-term deformations.
      PubDate: Fri, 22 Aug 2014 09:11:56 GMT
       
  • Volume 15 Issue 1 - Preface
    • Abstract: Wilson, John; Gad, Emad
      PubDate: Fri, 22 Aug 2014 09:11:56 GMT
       
  • Volume 15 Issue 1 - Dynamic characteristics of submarine pipelines and
           experimental validation of a bedding condition assessment approach based
           on mode-shape curvatures
    • Abstract: Yan, G; Peng, X; Hao, H Due to the adverse operational environment, submarine pipelines are susceptible to the development of free spans under pipes, which may endanger the integrity of entire pipeline systems and subsequently inflict huge economic losses and huge costs to restore ecological conditions. To maintain the integrity of pipeline systems, it is very important to develop an effective and reliable approach to identify and localise free-spanning damage at an early stage. In this study, the influence of different bedding conditions on modal parameters of submarine pipelines is first systematically investigated by considering the subsea operational environment. Then, the feasibility of curvatures of lower-frequency mode-shapes for localising free-spanning damage of pipelines is discussed, and damage indicators based on mode-shape curvatures are proposed. Numerical simulations are conducted on a 100 m long pipeline to illustrate how to localise free-spanning damage using the proposed damage indicators. The efficacy of the proposed damage indicators is validated by experimental tests.
      PubDate: Fri, 22 Aug 2014 09:11:56 GMT
       
  • 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 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
       
 
 
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