Electronic Journal of Structural Engineering

Publications
Loading on the offshore pile
Variation of von Mises stress and displacement under different structural and wave load ratios
Offshore piles are commonly used as foundation elements of various offshore structures, especially large structures such as Tension Leg Platforms (TLP). The stress distribution within such a large structure is a dominant factor in the design procedure of an offshore pile. To provide a more accurate and effective design, a finite element model is employed herein to determine the stresses and displacements in a concrete pile under combined structural and wave loadings. The vertical structural load is essentially a static load, while the lateral wave loading fluctuates in time domain and is directly affected by the incident wave angle. The parametric study will consist of varying certain parameters of the pile to study the effects of the stress distribution under various combinations of structural and wave loadings. Yes Yes
 
This article discusses the changes in tall building design practice after the World Trade Centre (WTC) buildings collapse. Although many suggestions were made post-9/11, regarding the improvement of the performance of buildings, no major changes have yet been implemented. These suggestions and the lessons learnt from the collapse are discussed in the paper.
 
In this part, a non-linear 3D finite element model for the analysis of unreinforced masonry walls subjected to static and seismic loads is presented, in order to demonstrate the applicability and potential of the method proposed in Part 1. The work reported here could also stand “on-its-own”, due to the detailed investigation made on this particular subject. The model developed considers masonry as a two-phase material, treating bricks and mortar joints separately, thus allowing for nonlinear deformation characteristics and progressive local failure of both bricks and mortar joints. The influence of the mortar joints is taken into account by using ‘interface’ elements to simulate the timedependent sliding and separation along the interfaces. Analytical and experimental solutions available in the literature have been employed to verify the results obtained from the present finite element model, showing that it is capable of a high degree of accuracy.
 
The strength reduction finite element method (SRFEM) needs to modify the input shear strength material parameters manually based on various reduction factors, which is trivial. In order to simplify the computation process, the SRFEM can be achieved by using field variables provided by ABAQUS; there-fore, it can be done automatically in software. By deriving the relationship between field variables and reduc-tion factor and getting the corresponding step time t1 when the calculation cannot converge, then it can quan-titatively calculate the stability coefficient of the slope. According to the different decay extent and speed of shear strength parameters c and φ in the process of slope failure, this paper adopted the dual reduction factors finite element method based on field variables for stability analysis of slope, and verified the feasibility of this method in the stability analysis by combining with classic examples, and found that this method not only im-proves computational efficiency but also the calculation accuracy.
 
Incorporating Graphene Oxide (GO) in concrete composite has been a good alternative to Pristine Graphene due to its hydrophilic nature and its ability to readily disperse in water the consequent cementitious mix. The addition of GO to the cementitious mix has been found to enhance mechanical properties. This paper aims to assess the abrasion resistance of GO incorporated concrete for its application in road pavement design. Experiments for strength in terms of compression, workability in terms of slump and abrasion resistance in accordance with ASTM-C418-20 using a sand-blasting rig are presented in the paper. It is shown that the addition of GO at percentages between 0% to 0.08% (to cement weight ratio), the compressive strength improves by 39% and 26% at 7 days and 28 days, respectively. The addition of GO consequently affected the workability where it was found that the addition of polycarboxylate ether (PCE) (superplasticisers) can drastically improve the workability, which is essential in practical applications. The abrasion was measured for specimens prepared with a high GO percentage between 0.1% to 0.3% and measured at 7 days and displayed a reduction of 70% of abraded volume at 0.3% GO. Finally, the study presents the benefits of using GO where the reduced amount of cement usage will consequently lead to sustainable concrete construction.
 
In this study a combination of helical springs and fluid dampers are proposed as isolation and energy dissipation devices for bridges subjected to earthquake loads. Vertical helical springs are placed between the superstructure and substructure as bearings and isolation devices to support the bridge and to eliminate or minimize the damage due to earthquake loads. Additionally, horizontal helical springs are placed between the abutments and bridge deck to save the structure from damage. Since helical springs provide stiffness in any direction, a multi-directional seismic isolation system is achieved which includes isolation in the vertical direction. To reduce the response of displacement, nonlinear fluid dampers are introduced as energy dissipation devices. Time history analysis studies conducted show that the proposed bridge system is sufficiently flexible to reduce the response of acceleration. The response of displacement due to provided flexibility is effectively controlled by the addition of energy dissipation devices.
 
The chemical admixtures named as accelerators improve the early setting and strength of cementations products whereas theh Cement prepared with large volumes of Fly ash (Pozzolana) fetch the durability and better sustainability. Achieving High early strength as well as durability in cementations products is a tough and challenging job which provokes the idea of the addition of accelerators to cement prepared with large volumes of Fly ash (pozzolana). The present study investigated the early setting and strength enhancement of Ordinary Portland Cement (OPC) replacement with 30, 40 and 50% of Fly ash when mixed with the accelerating admixtures such as Calcium nitrate (Ca(NO3)2) and Calcium nitrate (Ca(NO3)2) combination with Triethanolamine (C6H15NO3) at temperature of 25 ± 5 °C and 58±5 % relative humidity. In early ages, the maximum compressive strength was noted for 30 % Fly ash with 1% of Ca(NO3)2 in combinations with 0.05 % of C6H15NO3 and the achieved percentages noted as 18.23% and 54.29% for 1 and 3 days. The microstructural property (SEM) was also determined for OPC replacement with 30% of Fly ash at 1 and 3 days for 1% of Ca(NO3)2 in combination with 0.05, 0.1, 0.15 and 0.2% of C6H15NO3.
 
This paper presents an overview of the historical development of Australian loading specifications followed by discussions on the regulatory and policy aspects of the development. These included the historical and rational reasons for the development of each individual standard as well as the state of the current system. It is hoped that practitioners will gain some insights into the background and principles underpinning the system that is currently in place.
 
This paper presents from first principles methods of evaluating the seismic performance of a building using the method of inertial forces, method of maximum energy and method of maximum displacement. The introduction of these methods forms the main thrust of the paper. Importantly, the building can be deemed safe should this be indicated by any one of the three methods none of which requires the natural period of the building nor structural response factors to be estimated. Whilst these methods are very simple and consume little time to apply, the accuracies of the results are comparable with those from response spectrum methods. It is noted that the fundamental basis of each of these methods is very consistent with the new response spectrum model stipulated by the new Australian standard for seismic actions. A succinct and insightful account of the development of the seismic hazard model for Australia is also provided followed by a commentary on the use of dynamic analysis methods in practice.
 
Effect of elevated temperature on residual mechanical properties of slag based alkali activated concrete (SAC) was compared with Ordinary Portland cement concrete (OPC) when subjected to temperature up to 900 ° C. SAC was prepared using sodium hydroxide and sodium silicate activators. Residual compres-sive strength, tensile strength, flexural strength, modulus of elasticity and bond strength was studied at differ-ent temperature ranges to evaluate effect of high temperature on both concrete. It was observed that compres-sive strength for OPC decreased from 32 MPa to 19 MPa while in SAC variation was decrease was found to be from 32 MPa to 25 MPa. Similarly in SAC variation in residual split tensile, residual flexural strength, re-sidual Modulus of Elasticity and residual bond test was much less compared to OPC concrete. Physical changes were much noticeable in case of OPC at high temperature compared to SAC. This indicates that SAC performed better at high temperature as compared to that OPC.
 
Minimizing energy usage and increasing occupant comfort are the two primary objectives of in-telligent and eco-friendly buildings. Energy savings of up to 70%, combined with significant occupant pro-ductivity gains are possible via the application of wireless sensor and actuator networks (WSAN). Despite the increasing interests in WSAN-based wireless intelligent lighting control, no prior survey work exists. In the paper, we aim to provide a holistic survey of various WSAN-based schemes for intelligent lighting control so that researchers interested in the field can gain up to date knowledge and inspiration for future research. Spe-cifically, an overview of various sensor data collection and management techniques relevant to lighting con-trol is provided; taxonomy of various intelligent decision making schemes for lighting control is detailed; moreover, open issues within this field are identified and future research directions are proposed.
 
In recent years Wireless Sensor Networks (WSNs) have been deployed for Building Monitoring (BM) as they provide a low cost and reconfigurable alternative to centralized cable based sensor systems. Using WSNs gives rise to unique issues in its practical usage. Lifetime of a WSN is one such crucial issue to be addressed during deployment. Clustering is an effective way of extending the lifetime of a WSN. In this article we propose a distributed and energy driven clustering algorithm where the selection of the cluster heads (CHs) are based on relative residual energy level of sensors. Furthermore, the CHs are rotated only when their energy drops below a dynamic threshold computed by the algorithm. As a result, the overheads in the inter sensor communications will be reduced and thereby the proposed algorithm will favor more powerful nodes over the weaker ones to prolong the lifetime of the entire WSN. This will effectively prolong the usability of the monitoring system and thus the underlying safety of the building. The results will show that the proposed algorithm performs better when compared to existing clustering algorithms. Further we present theoretical analysis of the performance of the proposed algorithm in terms of correctness and complexity and explain how to identify the optimal values for key parameters such as transmission range R and re-clustering trigger threshold function value C in order to maximize the network lifetime.
 
An on-line adaptive input estimation method that estimates the moving force inputs of the bridge structure is presented in this research. By using the inverse method, input forces acting on bridge structural system can be estimated from the measured dynamic responses. The algorithm includes the Kalman filter (KF) and the recursive least squares estimator (RLSE). This work presents an efficient weighting factor r of the RLSE, which is capable of improving the estimation results. The capability of the proposed algorithm is demonstrated through several examples of the bridge structure system with different types of the time-varying moving forces as the unknown inputs.
 
The number of high rise building has increased significantly as supporting infrastructure in many big cities in Indonesia. Most of the high rise buildings in Indonesia are constructed using reinforced concrete (r/c) moment resisting frame systems. However, due to the high seismicity of many of the regions of Indonesia, the use of moment resisting frames as single system, especially for tall buildings, are restricted. This structural system is in general quite flexible, and therefore excessive lateral drifts are experienced under seismic forces. In practice, adding buckling restrained brace (BRB) can be used to limit the lateral drift in high rise buildings. The objective of this paper is to present a study on the use of BRB elements in high rise r/c frame buildings to evaluate their seismic performance. In this paper, a 20 story office building located in a high seismicity region is modeled into two basic distinctions, i.e. building with BRB and without BRB. The adopted system of BRB is UBB (Unbonded Brace) type. The seismic response of the buildings is obtained by conducting non-linear time history analysis with seven scaled ground motions. Then, the performance of these buildings are evaluated and compared. Based on the findings, some recommendations are proposed for the use of BRB in the design of high rise r/c frame buildings located in regions with high seismicity. © 2018 Electronic Journal of Structural Engineering. All rights reserved.
 
The metro station structure shows different failure modes when it is located at different burial depths. This re-search work is aimed to determine the influence laws of burial depths on dynamic response and failure modes of the metro station under near and far field earthquakes based on the nonlinear elastic-plastic finite element model of the metro station. The research results show that the horizontal displacements and acceleration dy-namic magnification factors of the metro station decrease and especially the internal forces increase gradually when the burial depth increases. The decreasing amplitude of the horizontal displacements and acceleration dynamic magnification factors of the metro station is reduced and the increasing amplitude of the internal forces slows down when the burial depth increases to a specific extent. Therefore, desirable anti-seismic per-formance could be achieved when a specific range of burial depth is avoided reasonably. At last, indoor shak-ing table test for metro station was done, through which we determined the initial failure position and the failure mode of the metro station under earthquake. And shaking table test results demonstrate the validation of the numerical simulation results.
 
To improve the anchorage effect, steel grit or steel shot of different size and different amount were mixed into resin agent commonly used in China coal mine. 19 groups tests were conducted using rightwhorled rebar bolt anchored into steel sleeve. Three bolt specimens were prepared and tested for each group, and as a comparison, the first group of bolt specimens was tested using resin anchoring agent without grit and steel. In the 2-10 groups, steel grits were added with different amount of 30, 40 or 50 and different particle sizes of 1.5, 2.0 and 2.5 mm. Each particle size corresponds to three quantities, a total of 9 groups of tests were conducted. Steel shots were added in 11-19 group tests with different amount and different particle size. The average peak pulling force of the first group is 121.3 (±3.1) kN, 5 of 9 groups of specimens with steel grit are more than 121.3 kN, and 8 of 9 groups of specimens have better average peak pulling force than 121.3 kN. It can be concluded that, under the condition of testing, the anchorage effect can be improved after steel shots are mixed into resin anchoring agent. © 2017 Department of Civil and Environmental Engineering. All rights reserved.
 
To study the basic mechanical properties of lightweight concrete incorporating shale aggregate replaced partially by nature sand (LCSARP), a variety of mixes were designed and the properties of the mixes were determined through a series of laboratory tests including compressive strength test, splitting tensile strength test, flextural strength test and tests to determine modulus of elasticity and poison's ratio. The failure processes, failure modes and the influences of replacement rate of natural sand on essential mechanical properties of LCSARP were studied. The result show that the failure modes of LCSARP are different from ordinary Portland cement concrete. In General, the mechanical properties of LCSARP show an increasing trend with the incremental replacement rate of natural sand, including fcu, fc, splitting tensile strength, flexural strength, fc/fcu, tension and compression's ratio, and the ratio (defined as similar flexure and compression's ratio (SFCR)) between flexural strength and the square root of cube compressive strength. With the incremental replacement rate of natural sand, the elastic modulus of LCSARP increases gradually, while the reverse is true for the Poisson's ratio. In terms of LCSARP, a precise and applicable relationship for the mechanical property parameter as fcu, fc, splitting tensile strength, flexural strength, fc/fcu at different replacement rates of natural sand was individually established by the regression analysis. A parabolic function between tension-to-compression ratio and Poisson's ratio for LCSARP was established that correlates well to the experimentally measured results. © 2017 Department of Civil and Environmental Engineering. All rights reserved.
 
Recycled aggregate concrete (RAC), as a way to reuse waste concrete, is good for solving environmental and resource problems. In this paper, the frost resistance durability of RAC under an extreme cold environment was studied, RAC specimens with different replacement rates were designed, and then the indexes of the specimens, such as mass loss rate, were calculated and compared. It was found that with the progress of the freeze-thaw cycle, the higher the replacement rate of recycled concrete aggregate (RCA) was, the worse the frost resistance durability was. The mass loss rate of RAC-3 (100% RCA replacement rate) was 5.56%, the strength loss rate was 40.86%, and the relative dynamic elastic modulus was 61.89%, all of which were significantly lower than that of RAC-0. The experimental results verify that the excessively large replacement rate of RCA is not conducive to the frost resistance durability of concrete. The replacement rate of RCA needs to be paid attention to when used in an extremely cold environment.
 
Waste management is becoming a major issue for communities worldwide. Glass, being nonbiodegradable, is not suitable for addition to landfill, and as such recycling opportunities need to be investigated. Due to the high material consumption of the construction industry, the utilisation of waste glass as a partial replacement for fine aggregate in structural concrete is particularly attractive. This project aimed to determine the level of glass replacement resulting in optimal compressive strength. Three concrete samples were tested at 7 and 28 days, for glass replacement proportions of 15, 20, 25, 30 and 40%. Compressive strength was found to increase up to a level of 30%, at which point the strength developed was 9% and 6% higher than the control after 7 and 28 days respectively. This demonstrates that concrete containing up to 30% fine glass aggregate exhibits higher compressive strength development than traditional concrete.
 
Sustainable concrete construction is critical to the economic development of infrastructures. The need and demand for infrastructure development is crucial to economic and social well-being of all nations. Of all the constituents in concrete coarse aggregate forms the biggest volume. As the reserve of aggregates is finite, the availability of suitable recycled concrete aggregate from demolition of concrete structures provides an alternate source to meet the increasing demand of new construction. Research on recycled concreteaggregate (RCA) at NUS was first conducted in the 1980’s. In recent years, further studies cover two main areas. The first is on the technique to improve the quality of recycled coarse concrete aggregate by means of microwave treatment. The other is to develop a modified acid treatment method to fully remove all attached materials from RCA coarse particles. This provides a more reliable basis for determination of the mortar content in RCA thus achieving a more precise relationship between properties of RCA and mortar content. Results on the relationship between 24-hour water absorption, bulk density and Los Angeles abrasion resistance of RCA and mortar content show a higher regression coefficient compared to others in published literature.
 
The paper deals with the experimental investigations done on free vibration characteristics of typical FRP aircraft instrument panel boards made of E-glass /Poly vinyl ester composite. Seventeen panel boards are made using the hand lay-up technique with different number of layers, fibre orientations, thickness and fibre contents. Their physical and elastic properties are determined experimentally. The support conditions and the loadings are simulated in the same manner, as they are located on the aircraft. The first three natural frequencies are determined experimentally. These results are compared with the same results obtained using a finite element analysis software package. Apart from these seventeen boards a number of analytical models with variations in the fibre orientations, the number of layers etc. are also studied and the results obtained are discussed.
 
The dynamic performance of railway vehicles needs to be carefully monitored to ensure their safe operation. Presently a number of systems such as the Vehicle Track Interaction Monitor and the Instrumented Revenue Vehicles, utilize a number of on-board inertial sensors to obtain near-real time information on the dynamic performance of railway vehicles. These systems provide rich data sets that give an indication of the underlying track condition and the corresponding dynamic response. This paper outlines the use of Machine learning to develop dynamic behavior predictive models for railway vehicles from measured data. This study worked on the development of 2 types of predictive models, viz. regression and classification model. The regression model predicted the time series dynamic response amplitude and the classification model classified the track sections based on the response distribution over it. Train speed and parameters estimated from the unsprung mass were used as predictors in the model. After the trial of a number of predictive models the Ensemble Tree Bagger method was found to have highest overall prediction accuracy. These predictive models can be utilized as a decision making tool to determine safe operational limits and prioritize maintenance interventions. © 2018 Electronic Journal of Structural Engineering. All rights reserved.
 
In this paper, a one-stage model-based damage identification technique based on the response power spectral density of a structure is investigated. The technique uses a finite element updating method with a Bayesian probabilistic framework that considers the uncertainty caused by measurement noise and modelling errors. The efficacy of two different evolutionary algorithms -a genetic algorithm and a covariance matrix adaptation evolution strategy -is examined via numerical simulation of time-history response data for a beam structure. A range of different damage scenarios have been considered including: both single and multiple damage locations; varying damage severity; the introduction of noise and modelling errors and incompleteness in the number of captured modes and measurement response data. The results clearly show that both evolutionary algorithms implemented are effective and their overall performance, measured in terms of accuracy, is very similar. However, the covariance matrix strategy is found to be significantly superior in terms of its convergence rate and the number of function evaluations required to find the solution for both noisy and noise-free response data.
 
High precision stretch bending of aluminum alloy profile is the key technology for making car’s frame body. A numerical simulation study on the displacement-controlled process for a typical kind of L-section aluminum alloy profile used in high-speed rail with finite element analysis software is presented. The effect of different friction coefficients, with or without baffle and cover plate on the equivalent stress,strain and cross-sectional distortion are investigated. It is shown that the increase of the friction coefficient can increase the cross-sectional distortion, equivalent stress and strain. The installation of baffle and cover plate can significantly reduce the cross-sectional distortion in the middle section of the profile, and increase the equivalent stress and strain to some extent.
 
This study focuses on the possibility of using rice husk ash (RHA) to produce high performance mortar of 100 MPa. The variables of study include effect of grinding and level of cement replacement with RHA. The fine aggregate used was mining sand instead of silica sand which is frequently used in producing high performance concrete (HPC). The average particle size of the RHA used was 13.50 μm, 20.43 μm and 29.92 μm and level of cement replacement was at 0%, 10 %, 15 % and 20 %. The results show that the use of 10 % RHA with the average particle size of 20.43 μm gave better compressive strength from 3 days onwards compared to control OPC and silica fume and the use of 20% of RHA with the average particle size of 13.50 μm at 28 days gave better compressive strength compared to other concrete.
 
The Grenfell disaster of June 14, 2017 brought into sharp focus the dangers posed by combustible façade materials. Polyethylene core panelling has been implicated in numerous fires such as The Address Downtown, the Saif Belhasa in Dubai and the Lacrosse building in Melbourne. Due to the large number of buildings with potentially combustible cladding, there is significant pressure to find an accurate and fast method to identify such cladding and any associated insulation as part of the overall assessment process. Over the past year, several different approaches to identification have been proposed and in this paper, we recount our expe-riences in developing a methodology to achieve this and discuss the limitations of this method and of competing methods.
 
Dynamic analysis should be preferred for seismic design of buildings and other structures instead of a static one. However, in several current building codes seismic static design of buildings requires an amplification of torsion moments (or story eccentricities) computed from lateral forces statically applied at floor levels. Discrepancy of factors used to estimate torsion amplification among codes suggests further study on this subject. The main objective of this paper is to show estimations of the building dynamic torsion. These estimations were obtained from experiments conducted in a four-story reinforced concrete building without accidental eccentricity that was excited with a dynamic force generator placed at the roof. The exciter was operated at several frequencies and it was placed at two roof positions. By assuming three degrees of freedom for each building slab and using acceleration records from tests, equations of motion of the system were used to estimate dynamic story torsional moments. Results support the idea that building torsional response also depends on coupling between the excitation force frequency and the building modal frequencies associated with torsion (either pure torsion or translation coupled with torsion).
 
A procedure is presented in which the method of column analogy, normally applicable to the analysis of single-span and closed frames, is extended for the analysis of multi-span frames with columns hinged to the ground. The extension involves consideration of conditions of rotations at the hinges. For illustration, a two-span hinged frame issolved in details. Results are in excellent agreement with values obtained using classical structural methods.
 
Fundamental principles from structural dynamics, pseudo excitation method and perturbation techniques are used to develop a new fast stochastic method for seismic analysis of the combined structure-damper system. In the approach, the mathematical equation of structure-damper system is expressed in the perturbation form, based on which the inverse operation of the matrices is avoided. Moreover, the new method also does not need the solution of any complex eigenvalue problem, in contrast to other methods found in the literature. Finally, the computation efficiency of the method is examined, and numerical comparisons with exact results are carried out to verify the accuracy of the proposed method. In all cases examined, the approach presented here shows excellent agreement with the exact results.
 
Highly concentrated stresses are imposed on maturing concrete slab local anchorage zones when post-tensioning (PT) load is applied. The prime nonlinear phenomena of the concrete while hydrating are the evolution of stiffness, the thermal strains, the visco-elastic nature of the concrete and cracking. Thermal and visco-elastic effects are more pronounced in early ages due to a higher rate of hydration reaction and the different phases present. The stresses associated with these effects may cause minor cracks in concrete, even prior to the application of the PT load. Finite Element simulation of early-age concrete behaviour is presented representing about four days of concrete curing in a plywood box. The thermal evolution is validated using experimental data obtained for the same mix. Results demonstrate that hydration reaction and visco-elastic effects can produce tensile stresses at critical times when the PT load is being applied. These stresses can have significant effects to the "spalling" stresses when a concentrated load is applied to the concrete section.
 
A numerical study by CFD (Computational Fluid Dynamics) simulation to obtain optimum spacing in between interfering and principal building where the interference effects are nullified and the behavior of principal building will be the same as the isolated building. The analytical result of rectangular plan shape prismatic bluff bodies are investigated in a series of Fluid Flow (CFX) analysis to study the optimum spacing in between interfering and principal building at 0° and 90° wind angle. This study highlights the Interference Factor (IF) of principal building which is similar to the an isolated building due to increasing spacing in between interfering and principal building. The plans of both the buildings are rectangular in shape and similar dimensions and principle axis. This study also highlights the IF, also found by the graphical representation of different spacing between interfering building and principal building.
 
In the present paper, a direct time domain procedure is used for dynamic linear and nonlinear analysis of the coupled system of reservoir-dam-foundation in 3D space. The foundation is assumed massed and infinite elements are used to model the semi-infinite medium via the far-end boundary of the foundation model. The nonlinear behavior of mass concrete is modeled using the smeared crack approach in which the elements can be cracked in each Gaussian point. The reservoir is assumed to be compressible and is modeled using finite element method with appropriate boundary conditions. The coupled system is solved using the staggered displacement method. As a case study, KARADJ double curvature arch dam in Iran is chosen to in-vestigate the effect of massed foundation on the seismic response of the system. It is found that the response of the system with massed foundation including infinite elements is the same as that when the artificial ab-sorbing boundary on the far-end boundary of the foundation is modeled using the viscous boundary. In addi-tion, when the foundation is assumed mass-less, the resulted seismic stresses within the dam body can be too conservative. Decreasing the crack profiles and displacements are observed in nonlinear analysis of the dam when infinite elements are used to model the semi-infinite medium via the far-end boundary of the foundation model.
 
This paper presents a vibration-based structural health monitoring (SHM) technique for the identification of damage in a concrete arch beam replica section of the Sydney Harbour Bridge. The proposed technique uses residual frequency response functions (FRFs) combined with principal component analysis (PCA) to form a damage specific feature (DSF) that is used as an input parameter to artificial neural networks (ANNs). Extensive laboratory testing and numerical modelling are undertaken to validate the method. In the proposed technique, FRFs are obtained by the standard modal testing and damage is identified using ANNs that innovatively map the DSF to the severity of damage (length of damage cut). The results of the experimental and numerical validation show that the proposed technique can successfully quantify damage induced to a concrete arch beam simulating a real life structural component of the Sydney Harbour Bridge.
 
Shear walls attached to or detached from the frame's columns  
Relationship between force reduction factor (R), over strength ( d ), ductility reduction factor (R  ) and displacement ductility factor () [8]  
Geometrical and mechanical characteristics of the material used in experimental tests
Wall element separated into layers and the direction of their operations  
Response curves with their bilinear response curves for X direction
In equivalent static analysis procedure, the design seismic force is affected by the response factor related to the inelastic behavior of the structure. This factor, whose value is used to calculate the amount of the energy damping, absorbed by the structure, depends on some parameters such as ductility and over strength. It is regarded as a constant coefficient for each type of structural systems in seismic codes. However, in dual structural systems, the effect of features like the geometry of the structure and lateral forces resistance system on this coefficient is not taken into account. This research is aimed at investigating the effect of the arrangement and length of the shear wall in the plan on the response modification factor in dual concrete systems. To do this, 15 concrete buildings as high as 30 to 45 meters were analyzed by nonlinear static method, using Perform 3D software. The initial estimation of the shear wall length was based on resisting 75 percent of the design base shear force by the shear walls. Next, the over strength factors, ductility coefficients, and subsequently the response modification factors of the models were determined and compared to the value used in the design procedure, presented in ASCE7 code. The results indicated that the value of response modification factor, in comparison with the presented value in ASCE7 code, was varied between-18% to +25% over changing the arrangement of the shear walls, and increased for up to +32% by increasing the length of the shear wall in the plan as much as 100% in proportion to the original model.
 
plate end debonding strength models
Rehabilitation of existing infrastructure has become a priority in recent years as an alternative to the daunting costs of rebuilding structures. Traditional repair methods have drawbacks, many of which can be overcome through the use of fibre reinforced polymer FRP laminates. However, the behaviour of FRP rehabilitated structures has yet to be conveniently and accurately modelled in many situations. For example, better understanding of their failure modes will allow for more precise designs that will balance safety and cost. To strengthen an RC beam or slab for flexure, FRP laminates are usually bonded externally on the structural element. A common failure mode encountered in initial tests was the laminate debonding from the surface. Here, the bond strength and modes of debonding between the FRP laminates and reinforced concrete members strengthened in flexure are reviewed. Current models for predicting the bond strength between the laminates and concrete are also scrutinized.
 
Blast studies involving bridges. 
Blast events can lead to critical injuries along with heavy casualties in addition to disastrous structural failure, thereby giving rise to detrimental economic and social impacts, both domestically as well as internationally. Bridges, an integral component of a vibrant transportation network, are not only vulnerable to accidental incidents, but also susceptible to deliberate attacks. Blast engineering regarding civil infrastructure, although very crucial in this modern era, has only received rapidly evolving interest in recent time, and many areas in this field, including most of the aspects regarding bridges, demand intensive attention. A state-of-theart review of the previous blast research projects concerning bridges is presented in this paper. The simplistic and advanced theoretical and practical investigation strategies employed are explained, and the distinct assumptions and justifications adopted are highlighted. The blast consequences observed on the individual bridge elements considered are described together with the subsequent impact on the overall integrity of the corresponding bridge systems. The mitigation tactics proposed are discussed, with major emphasis on the functions delivered as well as the inherent effectiveness. Further enquiries to be carried out for the future development of this engineering discipline are also identified.
 
Self-compacting concrete is a new generation of high-performance concrete with the aim of building durable concrete structures without any skilled laborers for concrete placement. This paper displays mixture proportion of self-compacting concrete and briefly discusses the effects of addition of rice husk ash (RHA), fly ash (FA) and ground granulated blast furnace slag (GGBS) to fresh properties, compressive strength and durability performance of self- compacting concrete.
 
Ordinary Portland cement (OPC) is conventionally used as the primary binder to produce concrete. The environmental issues associated with the production of OPC are well known. Binders could be produced by a polymeric reaction of alkaline liquids with the silicon and the aluminium in source materials of geological origin or by-product materials such as fly ash. Low-calcium fly ash-based geopolymer is used as the binder, instead of Portland or other hydraulic cement paste, to produce concrete. The manufacture of geopolymer concrete is carried out using the usual concrete technology methods. As in the case of OPC concrete, the aggregates occupy about 75-80 % by mass, in geopolymer concrete. The silicon and the aluminium in the fly ash react with an alkaline liquid that is a combination of sodium silicate and sodium hydroxide solutions to form the geopolymer paste. Geopolymerisation in fly ash based concrete could be occur by using different solutions with the solution-to-fly ash ratio by mass of 0.25 to 0.30. The best compressive strength will be more than 60 MPa for mixtures that used a combination of sodium hydroxide and sodium silicate solution, after curing the specimens for 24 hours at 65oC. The proportion of alkaline solution to alumino-silicate powder by mass should be approximately 0.33 to allow the geopolymeric reactions to occur. Alkaline solutions forms a thick gel instantaneously upon mixing with the alumino-silicate powder. By the use of the mass ratio of the solution to the powder of about 0.39 and mixing 57% fly ash with 15% kaolin or calcined kaolin and the alkaline liquid comprise 3.5% sodium silicate, 20% water and 4% sodium or potassium hydroxide the maximum compressive strength will be 75 MPa when fly ash and builders’ waste are used as the source material.
 
This paper presents the results of an experimental study of the effect of curing temperature on the compressive strength and split tensile strength of Geopolymer concrete (GPC) which is made using fly ash produced at Norochcholai coal power plant. A relationship between splitting tensile strength and compressive strength also is also developed using test data. The results are then compared with some expressions published in international literature. A mixture of Sodium Silicate and Sodium Hydroxide solutions was used to activate low calcium class F fly ash to form Geopolymers. All specimens were oven cured for 48hours where curing temperature was varied from ambient temperature to 80oC at 20oC intervals. One day of rest period was given to every sample before curing. Test results showed that curing temperature has a significant effect on rate of strength gaining of GPC. The output of this study has provided a better understanding of the correlation between splitting and compressive strengths of GPC, which has therefore helped to generate a new expression with better accuracy for GPC prepared using locally available fly ash.
 
Self-supporting lattice towers, which are having quite a few unique structural features, play a vital role in communication networks. Ensuring structural stability of these giant structures under all possible natural and human threats are vital as failures of such structures may cause a catastrophic human & property damages. Further, possible communication outages caused by failure of tower/towers in disaster situation are a critical as it may hamper rescue and other emergency operations. This was experienced by South and South East Asian countries during 2004 Tsunami. Hence, need of mitigating these situations have been highlighted by various reports. Therefore, ensuring structural integrity of self-supporting lattice towers under seismic forces is an essential and timely need. This paper discusses a seismic performance of four leg and three leg lattice towers under Response Spectrum analysis under different sub soil conditions. Results of seismic analyseshas also been compared with wind analyses results.
 
Trapezoidal profile of the corrugated web plates.
Simulation of local flange buckling for I-girders and modeling of the web support according to AISC-LRFD.
Local buckling of the corrugated web girders’ flanges and the assumed buckling coefficients of the AISC-LRFD. Combault, J. 1988. The Maupré Viaduct near Charolles, of such girders is 12% to 37% higher than that of France, Proceedings of the NEC/COP National Steel Con- plate girders with plane webs. Thus, the equations struction Conference, Miami Beach, USA, pp.12.1-12.22. used to calculate the critical moment of girders with Combault, J, Lebon, J.D. and Pei, G. 1993. Box girders using plane webs would underestimate the capacity of Corrugated Steel Webs and Balanced Cantilever Construc- plate girders with corrugated web to resist lateral tion. Proc. of the FIP Symposium, Kyoto, pp. 417-424. buckling but they are conservative for design pur- Elgaaly, M., Hamilton, R.W. and Seshadri, A. 1996. Shear strength of beams with corrugated webs, Journal of Struc- poses. Furthermore, it was concluded that the equiv- tural Engineering, ASCE, Vol. 122, No. 4, pp. 390-398. alent moment factor concept which is used for the El-Metwally, A.S. 1999. Prestressed Composite Girders with plate girders with plane web is equally applicable to Corrugated Webs. MSc Thesis, Department of Civil Eng. plate girders with corrugated webs. Thus, all the eq- The University of Calgary, Calgary, Alberta, Canada, 189p. uations and tables which are currently used to de- El-Metwally, A.S. and Loov, R.E. 1999. Composite prestressed concrete beams with corrugated webs, Proc. of termine the equivalent moment factor for plane web the Annual Conference of the Canadian Society for Civil girders may be used for corrugated web girders. Engineering, Regina, Saskatchewan, Canada, Vol. 1, pp. The numerical model was used to investigate the 305-314. local buckling of the compression flange of corru- Galambos, T.V. 1998. Guide to stability design criteria for gated web girders. It is concluded that the flange metal structures, 5th ed., John Wiley and Sons, NY, USA. Lebon, J. 1998. Steel corrugated web bridges - first achieve- outstand-to-thickness ratio, which is currently used ments, Proc. of the 5th Int. Conf. on Short and Medium by codes of practice as one of the criteria classifying Span Bridges, CSCE, Calgary, Canada, CD-Proceedings. the section compactness, should be based on the Leiva-Aravena, L. 1987. Trapezoidally corrugated panels large outstand of the corrugated web girder’s flange. buckling behaviour under axial compression and shear, Division of steel and Timber Structures, Chalmers University of Technology, Gothenburg, Report S84:2, Sweden, Publication S 87:1. 5 REFERENCES Luo, R. and Edlund, B. 1994. Buckling of trapezoidally corrugated panels using spline finite strip method, Thin Walled American Institute of Steel Construction (AISC). 2003. Man- Structures, Elsevier Science Limited, Vol . 18, pp. 209-240. ual of steel construction: Load and Resistance Factor De- Johnson, R.P. and Cafolla, J. 1997a. Corrugated webs in plate sign (LRFD). 3rd edition, Illinois, USA. girders for bridges, Structures and Buildings, ICE, Vol 123, Bergfelt, A. and Leiva-Aravena, L. 1984. Shear buckling of pp.157-164. trapezoidal corrugated girder webs, Division of steel and Johnson, R.P. and Cafolla, J. 1997b. Local flange buckling in Timber Structures, Chalmers University of Technology, plate girders with corrugated webs, Structures and Build- Gothenburg, Publication S 84:2, Sweden, 64p. ings, ICE, Vol 123, pp. 148-156. CAN/CSA-S16.1-02. 2002. Limit states design of steel struc- Reinhard, J.M. 1994. Pont de la Corniche, Ouvrages d’Art No. tures. Canadian Standard Association, Ontario, Canada. 19, pp. 14-19 (in-French). Capra, A. and Leville, A. 1996. The bridge at Dole, Proceed- Sayed-Ahmed, E.Y. 2001. Behaviour of steel and/or composite ings of the FIP Symposium, Post-Tensioned Concrete girders with corrugated steel webs, Canadian Journal of Structures. London, Vol. 1, pp. 135-141. Civil Engineering, vol. 28, No. 4, pp. 656-672. Chen, W., and Lui, E. 1987. Structural stability: theory and Sayed-Ahmed, E.Y. 2003a. Lateral Stability of Plate Girders implementation. Elsevier Science Publishing Co., NY, with Corrugated Steel Webs. Proceedings, 31st Canadian USA. Society for Civil Engineering Conference: Building our Ci- Cheyrezy, M. and Combault, J. 1990. Composite bridges with vilization, Moncton, New-Brunswick, Canada. June 2003. corrugated steel webs - achievement and prospects, IABSE GCF231-1 to GCF231-10. Symposium, Mixed Structures: Including New Materials, Sayed-Ahmed, E.Y. 2003b. Girders with Corrugated Steel IABSE Reports, Brussels, pp.479-484. Webs: Buckling Modes and Numerical Modeling. Proceedings, Advances in Structures: Steel, Concrete, Composite and Aluminum, Sydney, Australia, June 2003, pp. 807-812. 
Results of the finite element buckling analysis for cor- rugated steel web girders subjected to end moments.
Corrugated web girders represent a new structural system emerged in the past two decades. The girder's flanges provide the flexural strength of the girder with no contribution from the corrugated web which provides the girder's shear capacity. Failure of the web occurs by steel yielding, web buckling or interactively between them. Lateral torsion and local flange buckling of corrugated web girders represent another two possible failure criteria. Here, the work previously performed by the author on corrugated web girders was compiled and presented in a comprehensive format. The starting point is the shear behaviour of the corrugated webs which is investigated focusing on the failure modes affecting the web design. An interaction equation that considers web buckling and yielding is proposed. Numerical analyses are performed to investigate the buckling modes of the corrugated web, verify the validity of the proposed equation and explore the post-buckling strength of corrugated web girders. The numerical model is extended to determine the critical moment causing lateral instability for corrugated web girders. The applicability of the critical moment design equations, currently used for plane web girders, to corrugated web girders is examined. The numerical model is then used to scrutinize the local buckling behaviour of the compression flange. The applicability of the currently used limiting values for the flange outstand-to-thickness ratios to corrugated web girders is investigated.
 
Material Properties
Summary of displacements at the centre and supports of the test panels
Summary of major cracks
This paper presents experimental studies of concrete façade response to blast pressures. The experimental program also aims to establish the influence of fixings assemblies on the performance of pre-cast concrete façade panels. The current standardized approach of pre-cast concrete design as defined in UFC3-340-02 limits the support fixity of pre-cast wall panels to be a simply supported system. The restriction to a simply supported system in a pre-cast wall panel would lead to inefficient design due to non-optimized use of concrete panel thickness. The experimental results showed that varying fixing assemblies may lead to a partial fixity condition, which is not accounted for in the UFC3-340-02 design guideline. The partial fixity conditions observed in the experimental results indicate that there are residual capacities in the pre-cast façade systems. The efficacy of the façade panel system could be improved by taking into account partial fixity in the support system. Similarly, premature shear failure could also be prevented by understanding the additional contribution of the partial fixity on fixing assemblies. © 2015, Department of Civil and Environmental Engineering. All rights reserved.
 
The analysis of structural members in a compartment in a steel framed building subjected to fire attack is often difficult owing to the combined complexity of the material degradation and of the actions induced by thermal strains. Although such analyses can be carried out using advanced finite element packages such as ABAQUS and ANSYS, they do not permit an ‘overall feeling’ of the underlying structural mechanics to be fully articulated or understood. It is important that the response of structures under fire conditions, and the parameters that influence this response, are fully understood so that safe and economical performancebased fire designs can be achieved, and that codified treatments can be prescribed. This paper presents numerical studies of a steel beam subjected to fire attack in a steel framed compartment. The analysis is based on an analytical procedure that allows for a solution for the actions and deformations to be stated in closed form prior to the attainment of first yield of the steel at elevated temperature. It is found that the response of members under fire attack is governed by the slenderness ratio of the member subjected to elevated temperature the restraint afforded by the adjacent, cooler elements in the building frame and the applied thermal regimes.
 
Transient based technique is known as one of the most economical ways for pipeline condition assessment. This technique involves monitoring and analysing pressure transient profiles at multiple points in a distributed system. Its application is restricted due to its low spatial resolution (10 m). It is hypothesised that by increasing the number of pressure transducers and reducing the gauge length (distance between the transducers), the spatial resolution of the measurements would highly be improved. However, the deployment of pressure transducers is restricted to the location of the hydrants. In this paper, a submersible quasi-distributed optical fibre based pressure sensors were proposed, constructed and tested in laboratory to verify this concept. For this context, this paper describes the proposed optical device and presents some preliminary analysis and results obtained from a set of experiments. The experimental results show that using the quasi-distributed optical fibre based pressure transducers for pressure transient analysis can potentially detect small anomalies (200 mm) and measure the growth of the anomalies along a water pipe. © 2018 Electronic Journal of Structural Engineering. All rights reserved.
 
Structures should be designed for a long in-service life at the lowest cost. Performance based design (PBD) can be used for damage and performance assessment of older FRP-retrofitted multi-storey RC moment resisting frames (MRFs). PBD can be performed using nonlinear pushover analysis according to current codes. In this paper, performance of an existing/older RC frame that has been retrofitted with steel-braced by other researchers is assessed in order to evaluate the ability of the FRP-web bonded system to upgrade the performance level and ductility of RC MRFs. Initially, the flexural stiffness of FRP-retrofitted exterior and interior joints of each level of an existing RC ordinary moment resisting frame (OMRF) is determined using nonlinear finite element (FE) analysis. The stiffness obtained is then used in a mathematical model for pushover analysis of the FRP-retrofitted frame. The plain and the retrofitted frames (both steel-braced and FRP-retrofitted) are analysed using a nonlinear pushover analysis method. The seismic performances of the retrofitted frames are then compared with the plain frame. Finally, the global damage index of the frames at the performance point (and at the life safety (LS)) are determined from the capacity curves and discussed. This evaluation demonstrates that the damage degree of the frame is reduced after retrofitting particularly by FRP. In addition, the FRP-retrofitted frame has a lower damage index at the LS level.
 
The Masonry structures are complicated systems that require a thorough and detailed know-ledge and information regarding their behavior under seismic loading. Appropriate modeling of a masonry structure is a prerequisite for robust earthquake resistant design. However, modeling a real structure to a ro-bust quantitative (mathematical) representation is a very difficult and complicated task. This paper presents an approach toward a solution of the problem. A novel methodology for earthquake resistant design of masonry structural systems, either before or after their repair and/or strengthening, is presented. The entire process is il-lustrated in the case study of a 4-storey historical masonry structure located in the city of Patras, in Greece.
 
The present study deals with both experimental and numerical investigation on buckling effects of laminated composite plates subjected to varying temperature and moisture. A simple laminated plate model is developed for the buckling of composite plates subjected to adverse hygrothermal loading. A computer program based on FEM in MATLAB environment is developed to perform all necessary computations. The woven fiber Glass/Epoxy specimens were hygrothermally conditioned in a humidity cabinet where theconditions were maintained at temperatures of 300K-425K and relative humidity (RH) ranging from 0-1% for moisture concentrations. All the investigations are made with a symmetric cross-ply laminates. The present study deals with both experimental and numerical investigation on buckling behavior of laminated composite plates subjected to varying temperature and moisture concentration. Quantitative results are presented to show the effects of geometry, material and lamination parameters of woven fiber laminate onbuckling of composite plates for different temperature and moisture concentrations with simply supported boundary conditions with different aspect and side-to-thickness ratios. Experimental results show that there is reduction in buckling loads in KN with the increase in temperature and moisture concentration for laminates with clamped-free-clamped-free boundary conditions
 
This paper proposes a method for the preliminary arrangement of columns having variable sizes on an asymmetric plan, such that the resulting structure will have minimum torsion. Asymmetry can be due to shape of the plan as well as arrangement of columns having variable sizes. This study shows the influence of first three modes in determining the structural behavior of RCC framed buildings during earthquake. The time periods were approximately calculated by using 3D-shear-torsion beam method. The optimization was done using Genetic algorithm in Matlab. The seismic performance of general asymmetric structures with uniform square columns were compared with optimized asymmetric structures having columns with variable sizes. The results from pushover analysis showed significant increase in strength and ductility along the direction having torsion.
 
This paper presents an overview of recent research in Australia into seismic activity and ground motion modelling which has culminated in the development of a new response spectrum model for Australia as featured in the new standard for seismic actions. An important element of the research is the prediction of the displacement demand of small-moderate magnitude earthquakes that are characteristics of the intraplate tectonic environment of Australia. The practical implementation of the response spectrum model is illustrated at the end of the paper with the case-study of a lifeline facility. Advancements in seismic demand is complimented by the accurate assessment of the seismic performance of the structure and their sub-assemblages including those with non-ductile behavior.
 
Top-cited authors
Tuan Duc Ngo
  • University of Melbourne
Priyan Mendis
  • University of Melbourne
Anant Gupta
N. Haritos
  • University of Melbourne
Panagiotis G. Asteris
  • School of Pedagogical & Technological Education