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Pedestrian bridges are increasingly becoming landmark structures designed to promote a modern vibrant image of their surrounding landscape. Designs are becoming more daring; spans are increasing and becoming more slender and the use of lightweight materials is more prevalent. The net result is that it is often the serviceability limit state, rather than the ultimate limit state, that controls the bridge design. Sean O'Casey Bridge, Dublin, is the most recently constructed pedestrian bridge over the River Liffey. This articulated steel bridge, designed by O'Connor Sutton Cronin Consulting Engineers following an international design competition, is located in Dublin's docklands and spans approximately 88m across the river. This paper describes the pedestrian crossing tests, experimental modal analyses, and associated numerical modelling undertaken to assess vibration serviceability. The results of these analyses and their implications for the serviceability limit state assessment of pedestrian bridges are discussed in this paper. [ABSTRACT FROM AUTHOR]

Structural engineers, whether they are designers, contractors or academics, are frequently faced with the problem of introducing innovation into practice through research, such as for the development of new structures or the use of new materials such as fibre reinforced polymer. Hence, research is pivotal to the introduction of innovation. How research is applied is invariably a very complex and often costly problem and consequently needs careful examination to be effective. All engineers do research but by the very nature of research we all do research in different ways. This paper is the author's reflections on research procedures and approaches often used in structural engineering. These approaches are then illustrated using the author's research particularly on developing a generic failure model for reinforced concrete which can be applied to the seemingly disparate reinforced concrete problems of moment-rotation, shear capacity and the effect of confinement. Numerous concepts are introduced in this paper such as: the use of empirical modelling in plugging the gaps in the structural mechanics models; the elusive concept that is pivotal to understanding and should not be confused with the illusive concept; and categorisation of researchers to help sort out the mass of information available. [ABSTRACT FROM AUTHOR]

This paper presents the finite-element procedure for fatigue evaluation of reinforced concrete bridge deck under the application of truck wheel load. The approach is based on the smeared crack concept with the introduction of the fatigue tests of concrete and reinforcing steel available in the literature and the Palmgren-Miner linear criterion of cumulative damage in the analysis. The models are validated with the fatigue test of 1/6.6-scale AASHTO bridge deck under the application of fixed-point repetitive loading presented in previous study. Results are in good agreement. Significant contribution of the developed approach to the fatigue evaluation of bridge deck is a series of S-N relations which can be simulated at any desired levels of damage. This permits the investigation of the deterioration of bridge deck which is appeared to be useful information for highway agencies to prolong the life of their bridge decks. S-N relations are simulated at crack areas of 10%, 20%, 30%, and 40% of the bottom surface area of the deck slab to represent the propagation of crack. Deterioration of bridge deck subjected to passages of five-axle double-unit trucks in Thailand is investigated to demonstrate the application of the simulated S-N relations. [ABSTRACT FROM AUTHOR]

This paper presents a vibration-based damage identification method that utilises a 'damage fingerprint' of a structure in combination with Principal Component Analysis (PCA) and neural network techniques to identify defects. The Damage Index (DI) method is used to extract unique damage patterns from a damaged beam structure with the undamaged structure as baseline. PCA is applied to reduce the effect of measurement noise and optimise neural network training. PCA-compressed DI values are, then, used as inputs for a hierarchy of neural network ensembles to estimate locations and severities of various damage cases. The developed method is verified by a laboratory structure and numerical simulations in which measurement noise is taken into account with different levels of white Gaussian noise added. The damage identification results obtained from the neural network ensembles show that the presented method is capable of overcoming problems inherent in the conventional DI method. Issues associated with field testing conditions are successfully dealt with for numerical and the experimental simulations. Moreover, it is shown that the neural network ensemble produces results that are more accurate than any of the outcomes of the individual neural networks. [ABSTRACT FROM AUTHOR]

In this paper, a damage detection method based on an efficient algebraic algorithm of element modal strain energy sensitivity is proposed for detecting damage location and severity. The method adopts a closed form of element modal strain energy sensitivity. The element damage equations have been systematically established and a solution technique incorporated with the singular value decomposition-based regularization algorithm is used to ensure the correct solutions. A number of assumed damage scenarios for numerically simulated beams and two-dimensional frame structure have been used to demonstrate the applicability of proposed method. The noise effect is also presented. It is demonstrated that the proposed method is efficient in a one-step (non-iterative) procedure. [ABSTRACT FROM AUTHOR]

This paper reviews the experimental and modeling work that has been carried out concerning the behavior of fiber-reinforced polymer (FRP) composites in fire since the 1980s. The first part focuses on the thermophysical properties and temperature responses, while the second considers thermomechanical properties and responses, which are significantly affected by the thermal exposure of the FRP material. Furthermore, the application of deformation-based or strength-based failure criteria enables the prediction of time-to-failure. If the fire exposure time is less than the time-to-failure, the post-fire behavior is of interest and the post-fire properties and their potential recovery after cooling are particularly addressed. This fundamental understanding obtained as a result of both modeling and experimental work makes a reliable endurance design for FRP structures in fire possible. [ABSTRACT FROM AUTHOR]

A refined plastic hinge analysis method, known as one of the most effective and practical second-order inelastic analysis methods for steel frames, is able to evaluate the ultimate structural behavior of steel frames by considering the geometric and material nonlinearities. However, an appropriate advanced nonlinear solution technique has to be incorporated to help structural engineers perform the rational design of steel frames by predicting the ultimate strength and post-failure structural behavior accurately. In this study, a refined plastic hinge analysis method, combined with a work-increment-control solution technique with an iterative procedure in incremental loading steps, was presented in order to overcome the shortcomings of the load-increment-control solution techniques employed in previous studies. In the workincrement- control solution technique of present study, one convergence criterion refining the problem of using two convergence criteria in the conventional increment/iteration procedure of work-increment-control solution techniques and an automatic incremental algorithm calculating the load factor and the magnitude of incremental work for next incremental loading step were employed. To verify the accuracy and appropriateness of the present approach, three representative plane steel frames employed in previous studies were analyzed, and the analysis results were compared with those by other approaches. The present approach, that evaluated fairly accurately the load-displacement relationships, ultimate loads, plastic hinge numbers and locations, and the post-critical responses up to the formation of collapse mechanism of the plane steel frames, proved to be acceptable. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to investigate the structural behavior and performance of deep beams reinforced in shear with a honeycomb steel mesh (HSM). A series of four-point loading tests on five simply supported deep beams were carried out. The control beam was substantially deficient in shear strength, another beam was fully reinforced in shear by stirrups, and four other beams were reinforced with various configurations of HSM. The primary variables were the diagonal cell width and welding condition of the HSM. The shear behavior and performance of deep beams reinforced with various configurations of HSM were compared with those of the control beam and the beam reinforced in shear by stirrups. In this study, all of the tested deep beams failed in shear. Crack patterns and failure modes of the specimens were explained on the basis of the arch action. It was found from the test results that HSM was effective in reinforcing deep beams in shear. Further, the butt- welded HSM with a diagonal cell width of 100 mm was shown to be most effective in terms of stiffness, load carrying, and energy absorption capacities. [ABSTRACT FROM AUTHOR]

A bounded stochastic optimal semi-active control strategy for random excited hysteretic systems by using MR damper is proposed and illustrated by an example of a single degree-of-freedom hysteretic system. First, the dynamics of MR damper and the hysteretic force are expressed by using the Bouc-Wen model. Then, the system is converted into an equivalent nonlinear non-hysteretic stochastic system, from which the optimal bounded semi-active control law consisting of optimal unbounded control and bang-bang control is derived by using stochastic averaging method and stochastic dynamical programming principle. Finally, the response of optimally controlled system is predicted from solving the Fokker-Planck-Kolmogorov (FPK) equation associated with the fully averaged Itô equation. Numerical results show that the proposed control strategy has high control effectiveness and efficiency. [ABSTRACT FROM AUTHOR]

Double-I built-up columns are used extensively in low and medium rise steel structures. These sections have inherent compression, torsion and bending strength in all directions. The open sides of this type of column are covered with plates. When I beams are connected to double-I built-up columns through the column cover plate, the load transfer at the joint becomes a disturbing problem. To modify the connection, the authors propose a special type of connection using side plates. In this method the end of a beam is connected to the column by full depth side plates instead of direct welding of the beam ends to the column. The new geometry eliminates the traditional welded connection between the end of the beam and the face of the column. A series of eight non-linear, three dimensional finite elements models were developed to study the behaviour of the connection under cyclic loadings. The results obtained from the numerical analyses indicate that the proposed connection geometry has sufficient strength and ductility to be applied in 'special moment frames (SMF)' as a 'full strength' connection. [ABSTRACT FROM AUTHOR]

This document is a guest editorial from the journal "Advances in Structural Engineering" discussing the challenges faced by concrete infrastructure, such as sustainability, corrosion damage, alkali-aggregate reaction damage, and resilience. The editorial highlights the development of a new class of advanced materials called Ultra-High Performance Concrete (UHPC) and Ultra-High Performance Fiber Reinforced Cementitious Composite (UHPFRC), which offer high mechanical performance and durability. The special issue of the journal includes thirteen papers on UHPC, covering topics such as material-level performance, innovative design of UHPC structures, and the fundamental behavior of UHPC structures. The editors express gratitude to the authors and reviewers for their contributions to the special issue. [Extracted from the article]

This special issue contains a collection of excellent research work conducted by experts from around the world mainly on application of high-strength steel in civil construction. The editors of this Special Issue are grateful to the authors for their efforts in preparation of the high-quality papers and to the reviewers for providing constructive and timely reviews. With the ever-increasing application of high strength steel (HSS) material in industries due to its unique characteristics such as strength, energy absorption, weight and cost saving, there is a high potentiality for taking advantage of the exceptional capacities of this material in construction practice. [Extracted from the article]

The finite element (FE) model updating method aims to fit the parameters of a given initial analytical model in such a way that the model behavior corresponds as closely as possible to the measured behavior. However, the success of applications of the method depends on the analytical conceptualization of complex civil engineering structures, a well-designed and controlled modal test and an integration of analytical and experimental arts. This paper presents a sensitivity-analysis-based FE model updating procedure for FE model updating of Runyang Cable-stayed Bridge tower based on ambient vibration measurements. The updated model results correlate well with the experimental data in both the active frequency range and the passive frequency range. Extensive comparisons are made among the results obtained from different model updating cases. It is found that the appropriate initial FE model and determination of updating parameters are very important for the FE model updating of Runyang Cable-stayed Bridge tower. [ABSTRACT FROM AUTHOR]

The article offers information on the Best Paper Award given by the journal "Structural Engineering." The annual award aims to give special recognition to authors of the most meritorious paper published by this journal in a given year. The awardees are judged by the journal's International Editorial Board and International Advisory Board.

The article announces that two articles published in the 2006 issue of the journal including "Identification of Bifurcation Points Occurring on the Mechanism Paths of Deployable Structures," by T. Yoda and Z. You and "Debonding Mechanisms in FRP Plated Unreinforced Masonry Under Out-of-Plane Loading," by Shaohua Xia and Deric Oehlers have received the 2006 Best Paper Award from the journal.

In the engineering structures using circular steel tube (CST), the eccentric loading of CST members often occurs due to installation error and structural form. Existing research mainly focuses on the bearing resistance of circular steel pipes under the condition of eccentricity at one end. In practical application, both ends of CST members also may be eccentric. And with the increase in eccentricity, material yielding may occur prior to flexural buckling. So far, it's lack of reports about the mechanical behavior of CST members subjected to eccentric loading at both ends and the boundary between material yielding and flexural buckling. This paper presents experimental, numerical and theoretical studies on bearing resistance of thin-walled circular steel tube with slenderness ratio of 30, 40 and 50, subjected to eccentric loading at one end and both ends, respectively. The study reveals a significant discrepancy in the prediction of bearing resistance for circular tubes subjected to eccentric loading at both ends according to existing design codes. Considering the synthesis of bending moment and deflection caused by eccentric loading at both ends, the calculation method of the bearing resistance based on flexural buckling of CST is established, which enhances the prediction accuracy of test verification. In addition, a theoretical boundary between the two failure modes appearing in CST members under eccentric loading at one and both end(s) - flexural buckling and reaching the material yielding strength - was established as dominated by the slenderness ratio and loading eccentricity. [ABSTRACT FROM AUTHOR]

The application of steel trapezoidal corrugated web in steel-concrete composite girders has been widespread in building structures and has also appeared in bridges for a few decades, due to their advantageous mechanical properties. Embedding the trapezoidal web in the concrete slab leads to additional advantages such as omitting the welds of the top flange, a greater extent of the accordion effect and extra resistance in the load transfer between the two materials. Despite these advantages and their increasing use, there are not many experimental studies to analyse the behaviour of the embedded trapezoidal web and its involvement in shear connection resistance. In order to expand the experimental studies, laboratory tests are executed between 2017–18 at the Department of Structural Engineering of the Budapest University of Technology and Economics on large-scale test specimens, with a total number of 43 embedded specimens. The current paper introduces the executed test program, the analysed specimens, their specialties regarding the geometrical layout and the obtained results. The paper gives a quantitative comparison of the 43 specimens and evaluates the analysed shear connectors regarding their static performance. [ABSTRACT FROM AUTHOR]

High-strength steel (HSS) has been increasingly applied in structural engineering, while the work on residual stress of HSS sections is still insufficient. Limited research is available for welded H-sections above 690 MPa while with a plate thickness of more than 10 mm. This paper deals with the residual stress distributions of welded H-sections with flame-cut edges, which are fabricated from HSS plates with yield strength of 690 MPa and 960 MPa and thickness of 10 mm–20 mm, using both experimental and numerical method. The experiments showed that the welded tensile residual stresses in the weld region are not significantly affected by sectional dimensions and steel grade. Verified by comparing with the experimental results, three-dimensional (3D) finite element (FE) models using sequentially coupled thermal-stress analysis was adopted for parametric study of compressive residual stress of welded H-sections made of 690 MPa HSS. The results showed that the compressive tensile stress is negatively correlated with plate thickness as well as width-thickness ratio. Through regression analysis, formulae were proposed for estimation of compressive residual stress in the flange and web, respectively. Finally, residual stress distribution model was developed, which was proved effective by comparing with the experimental and FE results. [ABSTRACT FROM AUTHOR]

The article presents information on the J.M. Ko Medal which has been established in 2011 by the periodical "Advances in Structural Engineering" in honor of the founding Editor-in- Chief of the periodical, Professor J.M. Ko, who was instrumental in launching it in 1997. The selection process for the medal to be awarded in 2013 will start with the initial screening of papers by the Editors of the journal.

Vibration-based energy harvesting represents a clean power technology that can be of interest for application in civil engineering structures. This study focuses on energy harvesting using cantilever piezoelectric devices excited by operational and ambient bridge vibration. The optimal design and analysis of energy harvesters is usually performed using the mean and standard deviation of a response quantity of interest (i.e. voltage) under broadband Gaussian white noise excitation. In this paper, a novel holistic approach to the problem is proposed through the statistics of the voltage of piezoelectric energy harvesters under real measured bridge vibration base excitation. A new semi-analytic expression of the expected power is developed. The solution is based on the closed-form of the frequency response function between the harvester output voltage and the base excitation, and the experimentally measured spectral density of the latter. A study on the influence of the electromechanical coupling of the problem equations is first conducted. Then, a sensitivity analysis of the piezoelectric energy harvester parameters is performed. The critical analysis is developed through a case study of the measured long-term vibrations of a bowstring-arch highway bridge. Both operational and ambient vibration records are considered in the feasibility study. The results show the potential of the semi-analytic expression to evaluate the harvested power of piezoelectric harvesters under operational structural vibration. This is a promising approach to confidently develop future analyses on the power requirements of wireless sensor networks for SHM. [ABSTRACT FROM AUTHOR]

Long-span cable-supported bridge is one of crucial transportation infrastructures. Structural health monitoring (SHM) system that is used to assess structural service conditions and detect early damage has drawn a growing attention in engineering structural society. It provides a real-time monitoring of various structural changes under operational and extreme conditions. Yangluo Bridge over Yangtze River in Wuhan city of China is a 1280 m central span suspension bridge with an orthotropic steel box girder. Taking the SHM system of Yangluo Yangtze River Bridge as an example, this paper presents an implementation of SHM system on the bridge in terms of sensor layout, data acquisition strategy, data transmission, data processing, and abnormal alarm framework. With such an SHM system, the typical monitoring results are demonstrated such as operational environments, loadings, structural deformation, strains, dynamic properties, and structural responses. The SHM system of Yangluo Yangtze River Bridge is continuously gathering data and monitoring structural behavior. It is anticipated that it will provide either scientific or technological supports to the service comfort and safety of the bridge. [ABSTRACT FROM AUTHOR]

The attenuation zones (AZs) of periodic structures can be used for seismic isolation design. To cover the dominant frequencies of more seismic waves, this paper proposes a new type of periodic isolation foundation (PIF) with an extremely wide low-frequency AZ of 3.31 Hz–17.01 Hz composed of optimized unit A with a wide AZ and optimized unit B with a low-frequency AZ. The two kinds of optimized units are obtained by topology optimization on the smallest periodic unit with the coupled finite element-genetic algorithm (GA) methodology. The transmission spectra of shear waves and P-waves through the proposed PIF of finite size are calculated, and the results show that the AZ of the PIF is approximately the superposition of the AZs of the two kinds of optimized units. Additionally, shake tests on a scale PIF specimen are performed to verify the attenuation performance for elastic waves within the designed AZs. Furthermore, numerical simulations show that the acceleration responses of the bridge structure with the proposed PIF are attenuated significantly compared to those with a concrete foundation under the action of different seismic waves. Therefore, the newly proposed PIF is a promising option for the reduction of seismic effects in engineering structures. [ABSTRACT FROM AUTHOR]

According to the observations of past earthquakes, the vertical ground motions have had a striking influence on the engineering structures, especially reinforced concrete ones. Nevertheless, the number of studies on their aftermath is insufficient, and despite some endeavors done by researchers, there is still a shortage of knowledge about the inclusion of vertical excitation on the seismic performance and the collapse probability of RC buildings. Hence, the variation in the collapse risk of three high-rise RC frame-core wall structures when they undergo bi-directional ground motions is discussed. In this paper, incremental dynamic analyses are carried out under two circumstances, including the horizontal (H) and the combined horizontal and vertical (H+V) earthquakes, and the seismic fragility curves are derived. The inter-story drift ratio corresponding to the onset of collapse has also been defined. The buildings collapse risk under the two circumstances is obtained from the risk integral. Results indicate that in the H+V state, structures meet the collapse criteria for lower intensity measures. Thus, the collapse risk increases as the structures are subjected to bi-directional seismic loads, and the consideration of this effect leads to a more accurate evaluation of buildings seismic performance. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) is a revolutionary breakthrough in the history of structural engineering innovation due to its unique characteristics to strengthen and repair the deficient reinforced concrete structures. This paper aimed at evaluating the flexural characteristics of jute fiber reinforced polymer (JFRP) bonded reinforced concrete beams. The influence of the test variables comprised of strengthening scheme and corrosion rate for reinforced concrete (RC) beams. The experimental study comprised of casting six RC beams and testing them in flexure loading. To determine the flexural response of RC beams, three beams were fabricated with JFRP laminate having a level of corrosion of 0%, 7.5%, and 15%, whereas three beams were designated as control beams having same corrosion levels with no JFRP. Test results indicated that all JFRP strengthened beams exhibited increased ultimate load, yield load, first cracking load, and lower ductility index compared to control beams. The results also revealed that JFRP strengthening technique improved the flexural strength of the corroded beams efficiently, albeit the ultimate load of the beams diminished with higher corrosion level. Analytical calculations were carried out for quantifying the flexural characteristics and mass loss of beams which provided a good agreement with the test results. [ABSTRACT FROM AUTHOR]

For 3D flutter analysis of cable supported bridges, the aeroelastic effects of cables include the aerodynamic forces acting on cables and local lateral vibrations of cables, as well as the interaction of both. In order to investigate the aeroelastic effects of cables, a 3D flutter analysis method by a commercial structural analysis software package is developed and verified by the simply supported thin plate example and two actual bridges. The developed method can treat the cable as a multi-link model, instead of a single link model, and therefore can show the lateral degrees of freedom along the cable. Also it can simulate the structural damping perfectly and solve the flutter modes successfully. The flutter behaviors including aeroelastic effects of cables of two example bridges, Yangpu Bridge and Jiangyin Bridge in China, are investigated based on the developed method. The calculated results show that for the Yangpu cable-stayed bridge with a 602 m main span, the flutter critical wind velocity can be increased by 20.2% with the consideration of aeroelastic effects of cables. For the Jiangyin suspension bridge of 1385 m main span, however, the impact of the aeroelastic effects of cables on the flutter critical wind velocity is neglectable. The mechanisms of the aeroelastic effects of cables are discussed in this paper. [ABSTRACT FROM AUTHOR]

Modular Steel Buildings (MSBs) are fast evolving as an effective alternative to conventional on-site steel construction. An explanation of the concept of modular steel design, including its unique detailing requirements is given in this paper. The paper also focuses on a typical MSB floor system which is achieved by welding the webs of the stringers directly to the floor beams. A typical modular floor grid structure is designed using conventional methods. The floor is then modelled using the finite element method and analyzed under the effect of dead and live service loads. This allows an assessment of the effect of direct welding between stringers and floor beams on the analysis and design of floor beams, stringers, and welded connections. The results reveal that consideration of the true behaviour of direct welding leads to a distribution of forces and moments which is different from those found in conventional steel buildings. A simplified analytical model is proposed to capture such behaviour. Regression functions have been developed to describe the model. In practice, the proposed model can predict the actual forces and moments, leading to a reliable design of modular steel floors. [ABSTRACT FROM AUTHOR]

This paper is concerned with the analysis and design of radially retractable roof structures (RRS). This new type of structure consists of a foldable lattice of angulated beams connected by scissor hinges to which cover plates or membranes are attached. However, the current design has two obvious shortcomings. First of all, there is a lack of a convenient way to keep all the pivots of an angulated beam within the boundary of its corresponding RRS plate. Secondly, the stiffness of the RRS is too small to resist external loads, which limits the practical application of this structure. This paper aims to tackle these two problems. Based on the analytical formulae given by previous studies, we propose a corresponding design method for the RRS plates and thus the designers can easily figure out plates which fit perfectly together for an RRS. To increase the stiffness of the RRS, a few support conditions for the RRS are discussed and then the structural behavior of numerical simulated models under different support conditions is investigated. Moreover, some measures to increase the stiffness of the RRS are proposed, providing additional choice to the designers. Physical model is built to demonstrate the design concepts and show that the geometrical and mechanical analysis is correct. [ABSTRACT FROM AUTHOR]

Study of the dynamic properties of a monolayer cable net is described in this part II of the paper. The linear vibration properties of a cable net are analyzed in the form of a lumped-mass system based on the assumption of small-amplitude vibration. The respective influence of two vital factors: geometric shape and cable pretension on the dynamic properties of cable nets at different deflected positions under load is especially focused upon. Results show that when the geometric shape has a small displacement, the displacement influence on frequencies of vibration is almost the same as that of pre-tension, otherwise, the influence of geometric shape is far greater than that of pre-tension. Dynamic tests on the cable net model mentioned in Part I were also carried out at each pre-stretching stage. The results of experiments agree well with those of finite element analysis (FEA). In addition, a modified method called ‘MML’ based on Rayleigh's approach for the calculation of fundamental frequency is put forward in this paper, since it was found that Rayleigh's approach may sometimes introduce large errors. The nonlinear dynamic properties of the cable net were also analyzed. Different from the linear vibration case, nonlinear cases are to some extent amplitude-dependent. Thus explicitly approximate formulae for the first and second nonlinear modal frequencies are derived from continuous theory assuming the cable net to act as a continuous membrane. Transient dynamic analysis using the finite element software ANSYS was carried out to validate the formulae. The results given by the formulae and those via numerical analysis agree with each other well. [ABSTRACT FROM AUTHOR]

This paper reports an investigation into the stability of dual systems composed of the multi-storey steel frame and the flexural-shear bracing system. The lateral buckling of cantilever column, to simulate the bracing system in the dual systems, is first studied with both the flexural and shear deformations taken into account. A very accurate solution in simple expression, capable of considering the variations of the sectional properties and axial force along the height, is proposed for the buckling load of such a cantilever column, with which an explicit solution is proposed for the buckling load of steel frames with the flexural-shear bracing system. The threshold stiffness of the flexural-shear bracing system, the minimum stiffness for the braced steel frame failing into the non-sway buckling mode, is also investigated. Utilizing this threshold stiffness, a simple expression illustrating the relationship between the buckling loads of weakly braced frame with the fully braced and unbraced steel frames is presented. Comparisons are made between the predictions of solutions presented in this paper and those from the finite element (FE) analysis, showing reasonable agreements between these two results. [ABSTRACT FROM AUTHOR]

The buckling behaviour of thin shell structures under load has been a persistent challenge to engineering designers and researchers over many decades. In this article I consider two unusual experimental studies on the buckling of thin-walled elastic cylindrical shells, each of which sheds intriguing light on the buckling phenomena. The classical theory of buckling of thin cylindrical shells under axial compression predicts that the buckling stress will be proportional to t/R– the ratio of thickness to radius – other things being equal. But collected results of experimental studies from many laboratories, when plotted on log–log scales, show clearly that the buckling stress is actually proportional to (t/R)1.5, with the measured buckling stresses being scattered through a factor of about 4 for shells with R/t > 200. Such scatter is commonly judged to be in accord with Koiter's theory of 'imperfection sensitivity'. But that theory lays no claim to an understanding of the empirical 1.5-power law. I claim that a key to this situation is the experimental performance of some small-scale open-topped silicone rubber shells, buckling under their own weight, which clearly demonstrates a 1.5-power law, but with very little scatter. The buckling mode of these shells involves almost entirely inextensional deformation, with a single small dimple growing near the base, separated from the rest of the shell by a narrow boundary layer that accounts for almost all of the dimple's elastic strain energy. A straightforward, simple analysis of the mechanics of the dimple is consistent with the experimental 1.5-power law. As noted above, experimental buckling loads of shells that are closed at both ends also show the empirical 1.5-power law, but now with significant statistical scatter. A second aim of the paper is to throw light on that phenomenon. I venture to attribute it to the effect of the boundary conditions of the shell. I adduce support for this view from experimental observations on the buckling of a shell with special, frictional end-fittings. That feature produces significantly higher collapse loads, and with much smaller scatter, than for corresponding shells with fixed boundaries; and it permits striking pre-buckled deformations to occur, of a kind not previously noted. It will be appreciated that neither of the two parts of this article depends on the widely accepted theory of imperfection-sensitivity; hence my choice of title. It is a pleasure for me to submit this article to a special publication in honour of Michael Rotter, with whom I have discussed matters of this sort through three decades. [ABSTRACT FROM AUTHOR]

Glass façade systems in buildings are subject to racking actions caused by inter storey drifts from earthquakes and wind action. The performance of façade systems is dependent on the amount of imposed drift and the interaction of the glass panels with the façade structural support frames. There are two major concerns related to the glass façade system performance during and immediately after a seismic event; hazards to people from falling glass and the cost associated with building down time and repair. It was observed that earthquake damage to glass façade systems resulting from in-plane racking actions is increasingly common and yet there has been limited research published in this field. The research completed to date has mainly focused on traditional framed glass façade systems; however, the racking performance of point fixed glass façade system (PFGFS) is likely to be quite different. Therefore, the aim of the research presented in this paper is to assess the in-plane racking performance of PFGFS which is a façade system gaining popularity worldwide.Two unique full scale in-plane racking laboratory tests on typical PFGFS with different types of connections were conducted and specific racking mechanisms were identified. Sophisticated non-linear finite element models (FE models) were developed and benchmarked against experimental results with excellent correlation. Further detailed FE analyses were conducted to evaluate the individual drift contributions of each racking mechanism such as rigid body translation of the glass panels at the oversize holes for construction tolerance, spider arm rotation and spider arm deformation. It was found that most of the drift capacity is attributed to the rigid body translation at the oversize holes. In this paper, the laboratory test setup and the experimental results are discussed together with the confirmatory FE analysis results to assess the in-plane racking performance of the PFGFS. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the guest editors discuss various papers within the issue on topics including the life-cycle performance assessment, performance-based design, and structural performance.

This paper deals with the prediction of crack width for reinforced concrete structural members under pure bending. An analytical method is proposed to estimate the flexural crack width for reinforced concrete members. The proposed method utilizes conventional crack theory. Also, to consider stress conditions in tensile zone reinforced concrete members, a bond-slip relationship developed from axial tension tests was used. An analytical equation for the estimation of maximum crack width is formulated as a function of maximum bond stress. The validity, accuracy and efficiency of the proposed method are obtained by comparing the analytical results with the experimental data, and major design codes, as well as a number of analytical solutions. The analytical results presented in this paper indicate that the proposed method can effectively estimate the flexural crack width of reinforced concrete members under bending. [ABSTRACT FROM AUTHOR]

The article titled "Local Stress and Nonlinear Mechanical Behaviors of the V-Shape Pier-Girder Joint Based on Model Test" has been retracted at the request of the authors and the Journal Editor. The authors were unable to reproduce the conclusions from the published data in a recent field testing, as the cracks distribution appeared differently. The authors were also unable to provide the original raw data and unedited images from their article. One of the authors disagrees with the retraction, while the other authors did not respond for comment. [Extracted from the article]

A tall building may be modeled as a shear beam since its bending is mainly induced by relative sliding of parallel floor slabs. Classical shear beams do not consider the presence of bending moment. Since the bending moment of a building can be originated from tension-compression force couple due to combined effects of strong wall-to-wall and wall-to-slab interactions, a modified shear beam theory cooperating with bending moment is needed. This paper gives a theoretical analysis of a refined shear beam model. Emphasis is placed on the determination of the natural frequencies of a shear beam on an elastic base such as soil and carrying a lumped mass. The characteristic equation for free vibration of a modified shear beam is obtained. The influences of translational and rotational spring stiffnesses, axially compressive loads and attached mass on the natural frequencies are illuminated. [ABSTRACT FROM AUTHOR]

This paper describes experimental and numerical studies on the fatigue behavior of steel connections under combined loads, including a cyclic load and a static load. The steel connections consist of two steel plates joined together by single-sided girth welds. They were tested to failure under a constant amplitude tensile cyclic load combined with varied tensile static loads, which are perpendicular to the cyclic load. The experimental results reveal that the presence of the tensile static load in the perpendicular direction to the cyclic load is able to reduce the fatigue crack propagation rate and hence extend the fatigue life. Modeling of the steel connections is described in this paper to determine the effect of the magnitude of tensile static load on fatigue propagation life. The Boundary Element Analysis System Software (BEASY) is used. The analyses of these tested specimens are compared with their experimental results. It is proved that the boundary element method through the BEASY software is able to provide a close estimation of the cyclic behavior of steel connections. [ABSTRACT FROM AUTHOR]

Driving velocity, natural frequency of vehicle and natural frequency of bridge are the main contributing factors to vibration of a vehicle when passing a bridge. By separating contributions of the first two factors, one can estimate the natural frequency of a bridge indirectly from vehicle acceleration response when it crosses a bridge. In this paper, we apply this concept to estimate the bridge fundamental frequency indirectly using the response of a passing instrumented vehicle. The paper first describes analytical formulation and finite element simulation to demonstrate the feasibility of the method. Afterwards, it describes an experimental verification as a proof-of-concept of the method on a full-scale simply-supported short span bridge by using a light commercial vehicle instrumented with accelerometer. Dynamic responses of the vehicle while passing the bridge are recorded and analyzed. Spectra analysis of the vehicle responses reveal that the first natural frequency of the bridge can be estimated with reasonable accuracy when the vehicle moves with constant velocity. The concept of indirect frequency estimation is useful for assessment of short and medium span bridges where permanent instrumentation and routine visual inspection can be too costly. In this method, one can use inspection vehicle instrumented with vibration sensor to conduct periodic measurements by passing the vehicle over several monitored bridges and estimate their fundamental frequencies. When significant change in frequency is detected, detail inspections can be further conducted to investigate the possible damage on the bridge. [ABSTRACT FROM AUTHOR]

This paper investigates the characteristics of temperature gradients in a high-performance concrete (HPC) box girder with unconventional cross section under the solar radiation in Shanghai, China. The comparisons of thermal effects calculated according to the Chinese and foreign design code provisions show that the temperature gradient models of the current codes are not appropriate for the HPC box girder with unconventional cross section. In this paper, a new method is proposed to determine the solar temperature actions based on the stationary binomial probability model of random process. For the HPC box girder, the design standard value of equivalent linear temperature differences and cross-section temperature differences in the design reference period are obtained from the proposed method. Finally, the solar temperature gradients in the HPC box girder with unconventional cross section are gained based on the suggested design standard values. [ABSTRACT FROM AUTHOR]

Presented in the paper is the formulation of a governing second-order differential equation for the moment distribution along the length of a beam having two interfaces with partial shear interaction where two flange and two web components join to form the box shaped section. For practical applications such a closed-section beam of Fiber Reinforced Polymer (FRP) can be assembled from individual pultruded profiles using mechanical fasteners. This assembly approach can be used to construct deeper section sizes than can be achieved with a single pultrusion, and which can be transported in flat-pack units. In developing the governing equation for flexural response account is made of the finite connection stiffness at the web/flange interfaces by applying conventional elastic beam theory. The differential equation for the partial interaction problem is solved to formulate closed form equations for the flange force and the maximum deflection of a simply supported beam under four-point bending. A numerical parametric study is presented to show changes in beam performance indicators with the degree of shear interaction between the upper and lower bounds of full- and non-interaction. Results from a series of load tests using a three-layered prototype FRP beam are shown to be in good agreement. The theoretical predictions for maximum deflection are however found to be directly linked to the appropriateness of the measured connection stiffness entered into the closed-form equation. [ABSTRACT FROM AUTHOR]

This paper mainly deals with the kinematics of those widely used planar deployable structures, which are formed by angulated beams connected at with pivots. The equilibrium matrix method, which is quite different from displacement based methods, has been used to study their kinematic properties and as the basis for numerical simulations of the deployment movements. Two typical angulated beams, i.e. the depth multi-angulated beam (DMAB) and the breadth multi-angulated beam (BMAB), are explained and the corresponding equilibrium matrices deduced using matrix reduction theory, in addition, for these macro elements, the nature of the relationships between the equilibrium matrix and the stiffness matrix is discussed. Kinematic properties, e.g. infinitesimal movements and self-stress modes etc., have been studied and interpreted based on the orthogonal subspace of the equilibrium matrix. In this paper, an algorithm based on the equilibrium matrix SVD adopting an incremental procedure is described and applied to the motion analysis of deployable structures. Some typical numerical examples are illustrated to demonstrate the validity and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

In design of steel structures including bare steel frames, composite steel-concrete structures and those with walls and slabs, the conventional method considers each member separately and the effective length is then assumed for member resistance check. This involves inconsistency between the analysis method and the design method. The primitive and rather inadequate second-order P-Δ-only analysis considering only the sway effect has been used extensively in industry and in many computer programs. However, as the P-δ effect for member bowing is ignored, the effective length is still required to be assumed for every member. Researchers in PolyU have completed the second-order P-Δ-δ analysis and design method for bare steel frames and recent research has been directed to the design of walled frames such that the effective length is not required for flexural buckling check. In this paper, the structural shear wall is modeled by finite shell element whereas the imperfect stability function is employed to model beam-column members. The slab is proposed to be modeled by efficient floor elements. The model is compared well with the results by others. The P-δ effect for member bowing is considered so that the section capacity check alone is sufficient to check the structural adequacy without the assumption of effective length, classification of sway and non-sway frame mode and the tedious individual member resistance check. [ABSTRACT FROM AUTHOR]

This paper investigates the structural performance of steel-concrete-steel (SCS) sandwich structures comprising a lightweight concrete core sandwiched in between two steel plates. Different types of mechanical shear connectors such as stud shear connectors and Bi-Steel bar connectors are reviewed and their uses in SCS sandwich construction are discussed. Special J-hook connectors are developed and their uses are not restricted by the concrete core thickness. Direct shear (push-out test) and tension tests have been carried out on J-hook connectors to investigate their performance in transferring shear and tension forces between steel and concrete. The structural performance of SCS sandwich beams and slabs with J-hook connectors subjected to static and dynamic loads is also investigated and test results show that SCS sandwich structures with the J-hook connectors are capable of resisting impact with less degree of damage in comparison with the sandwich structures with overlapping stud shear connectors. The plastic capacity of the sandwich beams and slabs can be predicted with reasonable accuracy using the plastic analysis described in this paper. [ABSTRACT FROM AUTHOR]

The most vulnerable feature of most existing tall reinforced concrete chimneys when subject to severe earthquake excitation is the relative weakness of the sections around the openings near the chimney base. This paper documents an experimental study undertaken to investigate the cyclic behaviour of typical chimney sections with openings orientated to be bending critical and shear critical and the results are compared with previous tests with no openings. Significantly, no such cyclic tests have been previously been completed. The experimental results presented include; failure mode, over-strength factor, ultimate curvature, available ductility, hysteretic behaviour and strain distribution and the results are compared with some predictive analytical section models and design guidelines. The research indicated that chimney sections with openings were not brittle, but were significantly less ductile than sections without openings. The paper is relevant for both assessing existing chimney stacks and for the design of new chimneys in the vicinity of openings. [ABSTRACT FROM AUTHOR]