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Viscous dampers (VDs) connecting adjacent multi-story buildings are significantly useful not only for preventing severe earthquake-induced pounding, but also for mitigating the response of buildings. In the current study, in addition to utilizing viscous dampers, enhanced hybrid active tuned mass dampers (EHATMDs) are used at the top of asymmetric buildings and active tendons (ATs) are used at the sixth floor of symmetric buildings, while all these buildings are interconnected by VDs. The interval type-2 fuzzy logic controller (IT2FLC) is employed to produce real-time active forces applied to the actuators of EHATMDs and ATs. Moreover, soil-structure interaction (SSI) effects are considered. The aim is to assess the performance of all the mentioned controllers in mitigating both the translational and torsional responses of structures rested on soft soil. To reach these goals, three different layouts of adjacent buildings, including asymmetric and symmetric buildings, are taken into account. The results showed that the layout where asymmetric buildings were controlled by VDs in both main directions had the highest performance.

In this paper, a simplified modeling and analysis method for skyscrapers with an outrigger system is introduced. The simplified method is mainly based on the superelements and dominant degree of freedom methods, and it is codified by using MATLAB software. The simplified method results are verified with analysis results of the ETABS detailed model, where static, modal, and dynamic analyses are conducted. The proposed method's applicability on different configurations of tall buildings with outriggers systems is also verified through a parametric study. A comparative study with some previous studies is conducted to prove the efficiency of the proposed method. It was found that the adopted simplified modeling method has good accuracy in predicting the lateral displacements and inter-story drifts in the linear and nonlinear analysis. Furthermore, the simplified model has good accuracy in predicting the first modal shape and its corresponding period, while it has less accuracy in predicting the higher modal shapes and periods. Also, it was found that the simplified model underestimates the Max and Min story acceleration in comparison with the accurate model. The parametric study confirmed the proposed method's applicability on different configurations and topologies of tall buildings with an outrigger system. As a result, the simplified modeling method gives a deep understanding of the outrigger system behavior and its parameters. Therefore, it is an effective tool for modeling and analysis in the preliminary design stage. However, further improvements on the simplified modeling method should be conducted in future studies to increase the accuracy and quality of the obtained results and avoid its disadvantages.

The present study proposes a practical yet reliable model for stay cables in cable-stayed bridges considering large force variation under seismic actions. The proposed model is capable of approximating the nonlinear equivalent stress-strain relationship of cables, taking into account the variation of equivalent modulus of cables during the earthquake as well as possible cable loosening. The cable performance based on the proposed method shows an overall good agreement with the actual response of cables. Then, the model is applied to a case cable-stayed bridge under seismic actions and the structural response is compared with the conventional method which models the cables with a constant equivalent modulus derived at dead load state. Comparing to the proposed model, the conventional method fails to accurately describe the cable force at the low stress level and shows discrepancies in time histories of the structural response in terms of amplitude and phase angle. Moreover, conventional method might lead to underestimation of the bending moment at the tower bottom and longitudinal displacement at deck end for most cases, resulting in unconservative seismic design. Such result highlights the importance of applying the proposed model in seismic design of cable-stayed bridges.

Advent of concrete damaged plasticity material models has drastically improved the accuracy in predicting the structural response of concrete structural elements using finite element Analysis. However, exploration of the accuracy of this method in analysing complex concrete forms is scanty. Gravity Beams, a term coined in this investigation, are those beams in which gravity is used to design the topology of beam form conjointly with the novel manufacturing strategy ‘Fabric Formwork’. In this investigation these beam forms were numerically analysed using prevalent material and damage models. Numerical structural response was evaluated using these models and compared to experimental response. It was deduced from the comparative evaluation that numerical models closely predict the structural response of gravity beams. Moreover, dissimilarity analysis revealed that the diversion of the results was due the shape error between Modelled gravity beams, which were used for numerical analysis, and actual 3D scanned beams. It was deduced after analysis of experimental and numerical failure patterns that local imperfections also play a major role in the deviation in the numerical model. Furthermore, cross-sectional proportion ratio (CPR) was also introduced to give a numerical identity to gravity beams. This ratio was used to frame a parametric comparison of gravity beams and the corresponding structural response, to explore the parametric dependency.

In this paper, an innovative column reinforced with HRB 600 MPa reinforcements and ultrahigh-strength (UHS) steel bars with low bond strength was proposed. To study the cyclic behavior of the proposed column, three square cantilever columns were designed and tested under constant axial load and cyclic lateral load. The main parameter was the area proportion of the UHS longitudinal bars in the column section. Under the principle of equal area design, three proportions of 35%, 65% and 100% were selected. As the test results showed, with the increase in the UHS reinforcement area proportion, the columns had an improvement in reducing the residual displacement. Employing the UHS steel bars in the column can make the lateral deformation distribution of the column more uniform in the plastic hinge zone, which means a lower deformation curvature and mitigated concrete damage, thus leading to a corresponding small damage index. Numerical models were established and verified by comparison with the experimental hysteretic response of the three columns under cyclic loading. Additionally, parametric studies consisting of the axial load ratio (ALR) and stirrup arrangement (SA) were conducted. The effects of these parameters on the seismic behavior of the proposed columns were further investigated.

This paper presents a state-of-the-art review of significant studies published on coupled buildings. The approach of connecting two adjacent buildings has been effectively applied to reduce structural responses of a coupled building which is subjected to seismic excitation. The coupled building control utilizes two adjacent structures to transfer dynamic force which is applied to each other in order to reduce critical responses. The aim of this article is to review technologies and methods in structural connection of coupled buildings which are classified as (a) rigid (b) passive, (c) semi- active, (d) active, and (e) hybrid. The concepts of these connections are explained and formulated. The comparison, application and feature of connections are tabulated. Finally, some approaches to enhance the performance of connections and draw backs of studies are suggested.

An efficient and accurate beam element for performing explicit dynamic analysis of reinforced concrete beam elements was built using the absolute nodal coordinate formulation (ANCF). Such a formulation is useful for performing dynamic analysis under large strains and displacement with sudden load changes, such as during impact loading or for progressive collapse analysis. Compared with traditional nodal position formulations, ANCF uses position vector gradients to describe the rotation of the body and strain state, thereby avoiding the need for interpolating non-vectoral rotation parameters. The fiber element method was applied to calculate element stiffness from section deformations by subdividing beam elements into uniaxial fibers. The combined fiber element beam-column model with ANCF was validated by traditional co-rotational analysis and the quadrature element method (QEM), and thus may be used in general nonlinear dynamic analysis.

This paper presents a parametric study to evaluate the effects of soil-structure interaction (SSI) on the constant-strength inelastic displacement ratios (CR) of self-centering single-degree-of-freedom (SDOF) systems characterized by flag-shaped hysteretic behavior. The elastic homogeneous soil half-space below the foundation is simulated according to the concept of Cone model. Intensive nonlinear time-history analyses of soil-structure systems are conducted using three sets of 20 synthetic ground motions, which are matched to the design response spectra corresponding to very dense, stiff and soft soil classes. The effects of different parameters (i.e., fundamental period of the fixed-base superstructure, Tfix; strength reduction factor, R; structure-to-soil stiffness ratio, a0; aspect ratio of the superstructure, s; secondary stiffness ratio, α; and energy dissipation ratio of the flag-shaped model, β) on the inelastic displacement ratios are investigated and discussed. The analysis results indicate that similar trends are generally observed in inelastic displacement spectra with different soil class conditions, and ignoring SSI underestimates the peak inelastic displacement demands of the soil-structure systems. The inelastic displacement ratios increase when the value of R or a0 increases, while a rise in α or β leads to lower inelastic displacement ratios. It is found that aspect ratio has basically no influence on the inelastic displacement ratios for low a0 values, while has mitigating and amplifying influence on the inelastic displacement ratios below and above a threshold period for high a0 values.

Additional damping ratio (ADR), which plays a significant role in damped structure design, is broadly utilized to evaluate damping effect of the dampers. In current method, the ratio of energy dissipated by the dampers in one complete cycle to maximum strain energy of the structural system is adopted as the value of ADR. In the computation of damper energy dissipation, the bilinear model is commonly used to characterize hysteresis behavior of displacement-dependent dampers such as BRB. However, the accuracy of the bilinear model is not precise enough. In the light of the Bouc-Wen model can accurately characterize hysteresis behavior of various dampers, the analytical solution of hysteresis energy is derived. The ADR calculation methods based on the strain energy and the energy dissipated by the inherent damping of the main structure are proposed, respectively. The bi-objective design method of the RC frame with BRBs is put forward. The damping effect of the dampers is included in the design objectives, which makes up the deficiency of single objectives with the story drift ratio. The design objectives are that the story drift ratio of the frame does not exceed the limit, and the damping ratio reaches the expected value. The layout and force of the dampers are taken as design variables. Based on the finite element method, a RC frame with BRBs is designed iteratively. The reasonable time period length of time-varying energy is determined. Meanwhile, the strain energy method and modal damping energy dissipation method are compared and analyzed. As a result, the calculation result of strain energy method is larger than that of modal damping energy dissipation method. The strain energy method is hazardous to structural safety, and the modal damping energy dissipation method is suggested. The bi-objective design method is effective, which can further improve the structural performance.

Following an earthquake event, the safety of continued occupancy in terms of whether a mainshock-damaged building could withstand upcoming strong aftershocks is a key question for stakeholders. To answer this question, the residual collapse capacity of mainshock-damaged buildings should be evaluated, and in this way, an accurate assessment of the structural damage inflicted during a mainshock-aftershock sequence is of great importance. Recent studies have shown that energy-based damage measures, which calculate the dissipated energy due to cyclic-plastic deformations, can more accurately reflect the secondary damage induced by aftershocks than deformation-based damage measures. Park-Ang damage index is a combined seismic damage measure that integrates the damage caused by excessive deformations with the damage caused by the cumulative hysteretic energy dissipation. This study presents a framework for assessing the post-mainshock structural safety, in which the quantification of the damage accumulated during a mainshock and the determination of the remaining capacity to sustain strong aftershocks are made based on the Park-Ang damage index. First, residual collapse capacity diagrams are produced by performing incremental dynamic analysis under a suite of selected sequential ground motions. Next, an average diagram is made to find the maximum safe damage index, so that values above this threshold would represent the buildings that are deemed to be unsafe. The proposed framework is applied to a reference four-story steel moment-frame building to investigate its collapse potential and evaluates its structural safety in a hypothetical earthquake scenario. The results of the case study indicate that the proposed framework can effectively help structural engineers to decide on whether a mainshock-damaged building is safe to reoccupy and communicate the final decision in a simple diagram to stakeholders.

In this paper, performance based a fire resistance design method for evaluating the flexural carrying capacity of reinforced concrete (RC) beams has been proposed. The developed method is associated with a simple heat transfer model for RC beams subjected to the unsteady state heat transfer at transient heating boundary condition with three basic heating mechanism, i.e., conduction, convection and radiation. The validity and verification of the fire resistance design method and heat transfer model have been established with the experimentally measured and compiled database. Parametric studies also conducted to investigate the fire-resistance rating of designed RC beams and comparative appraisal of existing codes practices has been examined. Through the results of the fire resistance design method, it reveals that the developed method is capable to predicts fire-resistance rating of RC beams at fire scenarios, nominal cover, type of aggregate and thermal-induced concrete properties.

The impact of reinforced concrete beam-column joints on the shear strength of a building under cyclic loading depends on the types of joints applied. This study considers models of the uniaxial and biaxial joint shear strength of exterior beam-column joints. Prediction models of the uniaxial shear strength under uniaxial cyclic loading based on ACI 352, ASCE 41, and gene expression programming (GEP) have been developed. The ACI 352, ASCE 41, and GEP formulas have the potential to achieve improved results. This study considers a means by which to improve the results of previous models through a proposed deep neural network (DNN) model with three hidden layers among the artificial neural network structures. The R-squared value and mean absolute error determined through this DNN model are 97.94% and 34.13% for the uniaxial model and 98.28% and 2.70% for the biaxial model, respectively. These results indicate that the DNN model is more suitable than the ACI 352, ASCE 41, and GEP models for joint shear strength predictions.

A vertical spring had a changeable horizontal stiffness to avoid resonance under a seismic displacement, and a viscous damper had a perfect energy dissipation function to reduce the seismic displacement. They were joined together to achieve a seismic isolation system considerably reducing the seismic acceleration response, however, their displacement should be paid more attentions under an earthquake or in a shaking table test. Because the interface friction in the system affected the scaling process of the system in the shaking table test and the corresponding displacement responses, the system was numerically scaled before a real shaking table test. The comparison between the displacement responses of scaled models and prototype models shows that the spatial friction variation and the gravity distortion are the error sources of the relative and residual displacements of scaled models. The error of scaled relative displacement is reduced by the means of increasing PGA, damping constant, spring constant or reducing vertical spring length with zero stress, however, the error of scaled residual displacement is still chaotic under these means. Only if the error sources above are eliminated fundamentally will the error of scaled models be avoided. The conclusions are validated correct by a real shaking table test.

There are several algorithms for determining control forces of active devices in civil engineering structures. Uniform distribution of deformations theory is a structural concept which mainly focuses on equalizing deformations in order to promote the utilization of ductility capacity of structural elements thereby mitigating damages to a structure. In common active control algorithms, deformation uniformity and reducing damages are barely noted. In this research, a new active control algorithm regarding uniform deformation theory will be proposed. Uniform distribution of Deformation Control (UDC) algorithm consists of a massless optimized Virtual Added linear structure with Pinned connections (VAP) which is added to a desired original structure. This VAP can be treated as an added stiffness matrix. Once the parameters of the VAP were optimized in a manner that the desired responses were obtained from the new integrated structure, then, the new integrated structure is developed and analyzed in each time step. Finally, the VAP beams axial forces are extracted and applied to the original structure as control forces via active control devices such as active tendons. This proposed control algorithm is simple and effective in reducing responses especially drifts, making more uniform thereby reducing structural damages as well as decreasing the required capacity of actuators and the power consumption eventually. High potential and promising performance of the proposed UDC algorithm will be represented through numerical investigation in an office building example. The results are compared with Nonlinear Instantaneous Optimal Control (NIOC) algorithm as a very common active control algorithm for linear and nonlinear structures.

As part of a research on structural response of modular buildings and assemblages, this experimental study investigates the effects of gypsum sheathed light-gauge steel stud walls on the natural dynamic characteristics of modular steel frames. A full-scale volumetric steel module is instrumented with sensitive accelerometers connected to a data acquisition system, to study the effects of different infill wall configurations. To this end, the module’s sides are covered with bare light gauge steel frames and then different configurations and arrangements of gypsum plasterboard linings. The module’s acceleration responses are recorded during free and ambient vibration tests for each case. Then the operational modal analysis is conducted on the recorded data using output-only algorithms to extract the main dynamic characteristics of the steel module, including natural frequencies, mode shapes, and modal damping ratios. The contribution of different configurations and arrangements of infill walls to the response are examined and their effects are discussed. It is observed that the infill walls can change the dynamic characteristics of the modular steel frame more than the level suggested by the design specifications, such as 30–50% reduction by ASCE7-16.

The enormous environmental impact of construction is becoming increasingly apparent and unacceptable to many structural engineers, whose designs typically account for the majority of a building's embodied carbon. It is timely, therefore, that consensus is forming around a methodology for calculating embodied carbon. This encourages the inclusion of all life cycle stages, from material production and construction, through use and eventual demolition, disposal and reuse. In practice, however, end-of-life processes are fraught with uncertainty and often ignored, despite the potentially large associated carbon fluxes. Further uncertainty exists when considering bio-based construction materials, which store carbon during use. There are no widely-accepted means of accounting for timing of these carbon fluxes, despite the long service life of most buildings. Could we consider whole-life carbon in a more holistic and climate-focused way? This article uses dynamic life cycle assessment to convert greenhouse gas emission histories to key climate impacts using a simple dynamic model. The implications for structural design decisions are explored by comparing concrete, steel and timber options for a typical medium-rise building structure. Concrete is found to have a higher impact than steel, with the climate response of both options dominated by the large initial emissions of material production and construction. Timber has the smallest impact, for this example, under a typical scenario with sustainable forest management and re-emission of sequestered carbon at end-of-life. The analysis takes a forward-looking approach to sequestration, with timing corresponding to the growth of replanted trees. An optimistic timber scenario, whereby future carbon-capture technology avoids most end-of-life emissions, demonstrates the possibility of structures with small long-term climate cooling effects. Conversely, in a hypothetical worst-case scenario where no replanting or subsequent sequestration occurs, the long-term warming effect of the timber structure is increased by the net emission of biogenic carbon. Although end-of-life processes are important in the long-term, particularly for timber, the analysis also highlights the importance of the initial emissions from material production and construction. These cause high rates of short-term temperature increase and prolonged accumulation of radiative heat for all the buildings, but the impacts are again lowest for timber. Most importantly, the investigation shows how dynamic life cycle assessment can be used to explore climate impacts in a comprehensive, graphical and unbiased way. As a simple extension to established methodologies for calculating embodied carbon, it is a powerful decision making tool in the climate emergency.

The research efforts reported here are aimed at experimentally investigating the effects of incorporating steel fibres, with various dosages, on the shear capacity and shear behaviour characteristics of reinforced concrete deep beams. The primary experimental results obtained during this research, as well as an extensive secondary dataset, were used to examine and verify a proposed new model by the authors for calculating the shear resistance of steel fibres reinforced concrete (SFRC) deep beams. The experimental investigation involved 12 deep beams with four fibres dosages, namely: 0, 30, 40, and 65 kg/m3 and three stirrup ratios, namely: 0.1%, 0.15%, and 0.25%. The experimental results have shown that steel fibres improved the shear resistance of the deep beams (up to 55%), decreased the shear crack width (up to 68%), reduced the displacement of the beams (up to 57%), and enhanced the deformation capacity of the beams (up to 45%). The authors propose a new semi-empirical formula for estimation of the shear resistance of SFRC deep beams. The accuracy of the formula was evaluated using 116 beams dataset including a primary dataset obtained during this project as well as the published secondary dataset. The reliability and accuracy of the proposed formula were compared with other four published formulas. It is evident that the newly proposed formula increases the accuracy and reliability of the estimation of the shear resistance of SFRC deep beams when compared to the previously published models.

In this study, experiments were carried out to evaluate the seismic performance of a hybrid prestressed precast concrete (HPPC) system devised to ensure the integrity of precast concrete (PC) beam-column joints by introducing the post-tensioning method. A total of four full-scale HPPC beam-column joints were fabricated, and the presence of a topping slab, a post-tensioned length, and a type of tendon were set as the main variables. The quasi-static cyclic loading tests were performed to analyze the load-story drift ratio response, failure mode, ductility, residual deformation, and energy dissipation capacity of each specimen. The seismic performance of the specimen was then quantitatively evaluated based on the acceptance criteria of the ACI 374 report. The shear strength estimation model for the HPPC beam-column joints was also proposed and the proposed model was verified in detail using the test results.

To improve the punching shear capacity and ductility of slab-column connections, a new type of slab-column connection embedded with a steel skeleton was proposed and studied. An experimental investigation was conducted by testing a total of nine simply supported slab-column connection specimens subjected to vertical loads. The influences of the type of the steel skeleton, reinforcement ratio, steel content and slab thickness on the punching shear behavior of the composite connections were investigated. The test results indicated that the embedded steel skeleton could effectively improve the punching shear capacity of the slab-column connections, and the structural ductility was increased by changing the failure mode from punching shear to bending-punching. In addition, finite element (FE) software was employed to conduct parametric studies. Simulation results showed that the effects of the reinforcement ratio and the length of I-shaped steel on punching shear behavior of the composite slab-column connections were proved to be significant. Based on experimental and numerical studies, an analytical model was developed to predict the punching shear capacity of the proposed composite connections, and the calculated values were well in agreement with the results of tests and simulations.

CFRP ropes are relatively new and cheap materials that can be used in strengthening and rehabilitating RC elements. This research was designed to investigate the experimental behaviour of heat-damaged and unheated RC beams strengthened and retrofitted using near-surface mounted (NSM) carbon fiber polymer (CFRP) ropes. Ten RC beams were tested under a four-point loading test. Five beams were subjected to 700°C for 3 h and were partially damaged by heat while the other remaining beams were unheated. Several strengthening configurations were adopted where CFRP ropes were continuously anchored along the beam length. The flexural strength of the test specimens was then predicted using the ACI-440 guidelines and compared to the experimental results. Test results showed that the continuous strengthening configuration is considerably efficient in increasing the flexural strength of the RC beams. Adopting two layers of continuous CFRP ropes along the beam length, anchored at the tensile reinforcement level, increased the load capacity and stiffness of the unheated beams by 60% and 78%, respectively. It also restored the load capacity of the heat-damaged beams with an additional 47% in its’ load carrying capacity, but it decreased their peak deflection. Test results showed that the current ACI-440 guidelines that are designed for predicting the flexural strength of RC beams strengthened with NSM bars could be applied to predict the flexural strength of RC beams strengthened with NSM CFRP ropes with a suggested modification factor for the effective strain.

The analysis and design of concrete columns wrapped with fiber-reinforced polymer (FRP) composites require the mathematical equation of stress–strain relationship and the ultimate conditions (i.e., stress and strain) corresponding to the failure of FRP-confined concrete. The ultimate conditions of FRP-confined concrete were mostly developed using empirical methods based on regression analysis of test data obtained from the literature. There is a lack of mechanics-based formulations of the ultimate condition. In addition, from a practical design perspective, despite new advancements in the field of FRP confinement and the availability of sophisticated analysis-oriented and data-driven models, design guidelines and practicing engineers mainly need a single equation for the stress–strain relationship of confined concrete. Thus, in this study, a five-parameter William-Warnke plasticity model was utilized to find a new mechanics-based prediction of the ultimate condition of FRP-confined concrete using an updated database of 788 test data. Moreover, a new optimized stress–strain relationship based on the general expression of the Richard and Abbott equation was developed using 200 complete experimental stress–strain curves from 16 different independent studies. The proposed stress–strain relationship was presented in a single equation for the ease of application and its performance was verified against the experimental curves.

The Resilient Slip Friction Joint (RSFJ) is a relatively new friction damper developed and introduced in New Zealand. It is used in structures to dissipate the earthquake energy with the advantage of re-centring the structure back to its upright position. This paper investigates the experimental and analytical behaviour of the RSFJ when it is affected by the second-order effect (SOE) both in the damper in-plane and out-of-plane cases due to possible inherent imperfection in reality. The main consequences of SOE is firstly the reduction of the axial force capacity, stiffness of the damper and in return the structure, change in damping ratio. All of these may end up changing the effective period and seismic response of the structure. The ultimate catastrophic effect of SOE might be the failure of the damper if it is not properly designed for it in advance. From this perspective, this paper proposes some analytical expressions for the prediction of the damper response when it is affected by SOE. Furthermore, it investigates the effect of boundary conditions on SOE and provides some recommendations so that the SOE is minimized.

Localized corrosion often occurs on steel members due to paint peeling led from insufficient durability of the coating material or human collision, which may significantly reduce the load carrying capacity and safety performance of the structures. The effects of the parameters such as localized corrosion penetration, circumferential corrosion ratio, longitudinal corrosion ratio, slenderness ratio and eccentricity of mechanical behaviors of locally corroded circular steel tubes under compression were studied experimentally and numerically. Based on the test results and the finite element analysis, a calculation method was proposed for predicting load carrying capacity of the corroded specimen under compression. It is found that localized corrosion did not change the failure modes of test specimens, and all of them failed in the limit point buckling mode. The factors affecting the degradation of load carrying capacity and stiffness of localized corrosion specimens from high to low were corrosion time, circumferential corrosion ratio and longitudinal corrosion ratio. The most unfavorable localized corrosion modes of load carrying capacity and stiffness were H3L3-270 and H3L1-270, respectively. The load carrying capacity degradation of members increases with the increase of the localized corrosion ratio, circumferential corrosion ratio and longitudinal corrosion ratio, while decreases with the increase of the eccentricity. The formula proposed can be used to predict the load carrying capacity of locally corroded circular steel tube members under compression.

The seismic performance and design method of fabricated concrete bridge piers limit their applications in complex and harsh environments. In this study, a continuous bridge pier in an 8-degree seismic fortification intensity area was considered as a prototype. Two 1/3-scale models were designed and manufactured. The specimens were connected via a grouted sleeve connections (SFP) and a grouted sleeve prestressing tendon composite connections (SSFP), respectively. Moreover, a cast-in-place 1/3-scale model (reinforcement concrete pier, RCP) was designed as a comparison specimen. Quasi-static experiments were performed on these three specimens. The seismic performance of the specimens was analysed according to the failure phenomena, bearing capacity, displacement ductility, stiffness, energy-dissipation capacity, and residual deformation. On these basis, a bearing-capacity estimation method for SFP (including SSFP) was developed and validated. The results indicated that the damage to the SFP and SSFP mainly accumulated along the top and bottom of the sleeves. The plastic hinge area of the SFP and SSFP moved up or down. Thus, the damage to the SFP and SSFP was concentrated at the joints. Cracks first occurred at the seam of the two fabricated specimens when the loading drift was relatively small. Then, the concrete at the loading edge of the joints was crushed. Furthermore, the longitudinal bars yielded and broke. Finally, the specimens failed. Compared with the RCP, the SFP and the SSFP had larger yield and ultimate displacements. The bearing capacities of the RCP and the SFP were similar. However, the bearing capacity of the SSFP was significantly higher. The bearing capacities of the SFP and SSFP did not decrease significantly before the specimens failed. Compared with the RCP, the SFP had a lower initial stiffness, a lower stiffness degradation rate, similar displacement ductility, smaller residual displacement, and less cumulative energy dissipation. The SSFP was better than the SFP with regard to the displacement ductility, initial stiffness, and cumulative energy dissipation. Thus, the SFP and SSFP can satisfy the seismic requirements of high-intensity areas. The proposed bearing-capacity estimation method can be used for the seismic design and evaluation of SFPs and SSFPs.

Eurocode (EC3) bending moment design model of mono-symmetric corrugated web girders (CWGs) is based on the critical failure mode among the tension flange yielding, the compression flange yielding and the lateral-torsional buckling (LTB) of the compression flange. Recently, LTB behaviour of S460 laterally-unrestrained mono-symmetric CWGs with fully-effective flanges has been investigated by the authors, from which EC3 design model has been modified to better represent their actual strength. Nevertheless, the effect of the local buckling (LB) of slender compression flanges on the flexural strength and behaviour of such long girders has not been examined. While the corrugated web potentially makes large contribution to the out-of-plane stiffness, LB of the compression flange is expected to reduce LTB resistance of such girder significantly. Principally, this paper is devoted to exploring such effect on the accuracy of EC3 bending moment design model. Currently, virtual tests, by using ABAQUS software, are generated based on accurate validation. Then, parametric studies, intentionally designed to eliminate the tension flange yielding, are carried out on simply supported girders considering mainly the influences of the flange and web dimensions on the behaviour of S460 mono-symmetric CWGs. The strengths of such girders are compared with EC3 design model, from which it is found to provide unsuitable predictions. Hence, new formula has been proposed to accord better with the FE results. Additionally, several conclusions are provided at the end to assist design engineers in suggesting efficient cross-sections.

This paper proposes a deep-learning framework, specifically, a Deep Belief Network (DBN), for studying the web crippling performance of cold-formed stainless steel channel sections (lipped and unlipped as well as fastened and unfastened) with centered and offset web holes under the end-two-flange loading condition. G430 ferritic, S32205 duplex and 304 austenitic stainless steel grades are considered. A total of 17,281 data points for training the DBN are generated from an elasto plastic finite element model, validated from 69 experimental results reported in the literature. When a comparison was made against a further 53 experimental results reported in the literature, the DBN predictions were found to be conservative by around 10%. When compared with Backpropagation Neural Network (a typical shallow artificial neural network) and linear regression model based on PaddlePaddle, it was found that the proposed DBN outperformed these two methods, using the same big training data generated in this study. Using the DBN predictions, a parametric study is then conducted to investigate the effect of web holes, from which unified strength reduction factor equations are proposed. Finally, a reliability analysis is conducted, which shown that the proposed equations can predict the web crippling strength of cold-formed stainless steel channel sections under the end-two-flange loading condition.

In this paper, the isolation performance of truss string structure on rubber bearings considering relative rotation between the upper and lower surfaces of the bearings is studied. Through the test and finite element analysis, the following conclusions are obtained: the initial rotation angle has a great influence on the horizontal stiffness of the isolation bearing. In practical engineering, the loss of prestress, the change of temperature and general vertical loads will produce rotation angle between upper and lower surfaces of the bearings. Therefore, the numerical analysis of the truss which consider rotation angle of the rubber bearings is carried out. The results show that the horizontal acceleration responses of the truss decreases, and the displacement of the isolation bearing exceeds the code limit. Therefore, the practical engineering structure should consider the influence of the rotation angles.

The stable equilibrium state of a structural system corresponds to the relative minimum total potential energy state. In order to analyze the structures by energy principle, energy minimization is addressed as an optimization problem. In early studies, few structural problems are investigated with the aid of energy minimization; flat and curved plates, bending plates, sandwich plates, cylindrical shell elements, truss elements, hyper-elastic membranes. The aim of this paper is to investigate the analysis of plane stress/strain elements through energy minimization. For this purpose, three state-of-art parameter-less metaheuristic algorithms were used to find the relative minimum total potential energy; Teaching–Learning Based Optimization (TLBO), Elitist Teaching–Learning Based Optimization (ETLBO), and Jaya Algorithm (JA). Additionally, a modification of Jaya Algorithm that named The Modified Jaya Algorithm (MJA) is proposed to analyze the plane stress/strain elements. According to the analysis results of the benchmark problems, TLBO and MJA are robust for the plane stress/strain analysis. In addition, MJA is more suitable algorithm in respect of computational efficiency from the other compared metaheuristic algorithms.

Studies conducted after Northridge and Kobe earthquakes have shown that brittle failures in connections and members of structures led to extensive and catastrophic damage. Consequently, evaluation of critical points in a structure, controlling, and mitigating the seismic responses of structures, and avoiding structural damage such as low-cycle fatigue are needed. In this study, an adaptive control algorithm is used to reduce the low-cycle fatigue damage in two benchmark structures equipped with MR dampers. First, optimum parameters of the adaptive control method, called the Simple Adaptive Control Method (SACM), are calculated. The effectiveness of using SACM to mitigate the structural response of a three-story benchmark structure and a twenty-story benchmark structure under earthquake is studied. Finally, reducing fatigue damage on those structures subjected to various earthquakes is examined to extend the fatigue life of the structures. To calculate the cumulative fatigue, the rain-flow counting technique is used. In order to validate the developed nonlinear models, natural frequencies and displacement response of a three-story structure subjected to three different earthquakes are compared with the values presented in the reference studies. A numerical search method is used to minimize the ratio of cumulative fatigue and maximum ratio of roof displacement in each structure. The results show that the adaptive control system can reduce fatigue damage in elements, and fatigue life could be extended in structures. Also, the effects of using the semi-active adaptive control approach on dynamic characteristics of a structure are studied.

This paper proposes a novel rotational damper, called rotational yielding damper (RYD), for enhancing the seismic behavior of new and existing building structures. In the proposed damper, hourglass-shaped cylindrical steel pins, named hourglass steel pins (HSP), are used as energy dissipating elements, which can be easily replaced in case of failure after severe earthquakes. The earthquake input energy is dissipated through inelastic deformations of HSPs during the loading. The effectiveness of HSP as an energy dissipation element has already been validated numerically and experimentally in various locations of structures. In this paper, a numerical study is performed to evaluate the behavior of the proposed damper and investigate the effects of important damper parameters on the cyclic response of a simple steel frame equipped with it. In addition, the application of the proposed damper in an eccentrically braced frame is also studied. For these purposes, a multi-scale modeling approach in Abaqus software is used to develop numerical models. The results clearly reveal that a properly designed and manufactured RYD has high energy dissipation capacity and equivalent viscous damping as well as high lateral strength and stiffness. Therefore, it can be inferred that RYD can serve as an energy dissipation device in building structures.

Bayesian networks support the probabilistic failure analysis of complex systems, e.g., dams and bridges, needed for a better understanding of the system reliability and for taking mitigation actions. In particular, they are useful in representing graphically the interactions among system components, while the quantitative strength of the interrelationships between the variables is measured using conditional probabilities. However, due to a lack of objective data it often becomes necessary to rely on expert judgment to provide subjective probabilities to quantify the model. This paper proposes an elicitation process that can be used to support the collection of valid and reliable data with the specific aim of quantifying a Bayesian network, while minimizing the adverse impact of biases to which judgment is commonly subjected. To illustrate how this framework works, it is applied to a real-life case study regarding the safety of the Mountain Chute Dam and Generating Station, which is located on the Madawaska River in Ontario, Canada. This contribution provides a demonstration of the usefulness of eliciting engineering expertise with regard to system reliability analysis.

The influence of the material strain-hardening response on the plastic stability of the moderately thick stainless-steel and mild-steel tubular columns is studied. A parametric study on the strain-hardening slope of the material σ-e; curve is presented to exhibit variation of the load-carrying capacity in the tubes. The mechanism of the so-called elephant’s foot plastic buckling mode is discussed. The load-carrying capacity and post-yield response of a couple of representative tubes, examined by experiments, are also simulated using the finite element method (FEM), thereby validating the integrity of the incorporated numerical framework. The framework is used to examine the load-carrying performance of the tubes with various D/t ratios. The results produced by the parametric study are used to investigate a collapse index for the prediction of the ultimate load-carrying capacity of the tubes. Useful results about the collapse state of the tubes with different D/t are obtained by focusing separately on the various segments of the material sequential softening after yield point. The results highlight the significance of each segment of the post-yield portion of σ-e; curve on the load-carrying capacity of various tubular columns. For example, this study shows that for a case study (tube with D/t = 30) by doubling the slope of the later segment of the strain-hardening region in the σ-e; curve, one can expect a significant increase (as high as 111%) in the energy absorption capacity prior to collapse threshold state (CTS). In contrast, a moderate increase of only 17% shall be expected in columns with D/t = 60 when the same level of change to the strain-hardening slope is considered.

In recent decades, different macro-models have been proposed for simulating the behaviour of concrete shear walls because of their significant role in the seismic performance of urban buildings. The ability of Timoshenko's beam theory to evaluate the behaviour of slender and moderate-aspect-ratio concrete shear walls was evaluated in this work. For this purpose, a non-linear displacement-based Timoshenko fibre element was first added to OpenSees software. A new constitutive model based on modified compression field theory was used for the stress–strain relationship of the materials. To validate the element and the materials used, the results of the numerical model were compared with a set of laboratory tests of concrete shear walls subjected to cyclic and seismic loads (shaking table tests). Evaluation of the numerical model and the experimental results revealed that the analysis procedure used to model the reinforced concrete walls predicted their overall and local responses with acceptable accuracy. It can thus be used as a reliable tool for the analysis of slender and moderate-aspect-ratio concrete shear walls.

Process optimization using metaheuristic algorithms is rapidly gaining interest from engineering practitioners and researchers. This study uses the cuckoo search algorithm (CSA) to find the optimum parameters of a novel smart damper under seismic excitations. For this purpose, seismic responses of four-story and nine-story building configurations under seven pairs of ground motions have been considered. The smart damper is a shear polyurethane friction (SPF) passive control device, made up of shape memory alloy (SMA) plates, friction devices, and polyurethane springs. The damper was installed using braced frame shear links of Y-shaped inverted type, in the form of a vertical link beam placed in the eccentrically braced frames. Because the shear mode of failure is common in such a configuration, the SPF damper is expected to reduce the residual inter-story drifts of the building subjected to strong earthquake loading. Numerical optimization and time-domain simulations were carried out using the MATLAB and OpenSees software programs, respectively. The targeted optimization criteria include the peak values of inter-story drift, residual drift, and floor acceleration; and the design parameters consist of SMA cross-sectional area, friction force, and the polyurethane stiffness of the SPF-SMA system. The results of this study demonstrate the suitability of CSA for the determination of optimum parameters of the SPF-SMA system for the buildings and ground motions considered. Future studies will investigate the generalizability of the proposed method to other building configurations and ground motions.

Material efficiency is not currently a common driver of building design. Indeed, in previous studies, we estimated that 12% of the mass of steel used in structural frames would be saved by more accurate specification of steel members. However, this inefficiency is not the main reason structural frames are light or heavy. We show here for the case of steel structures that it is the layout of the grid and the choice of the decking which have the largest impact on the embodied carbon of frames. Using a database of real designs, associated to a generative design model, we quantify the impact of grid and decking selections. Using our model, we find that real designs are relatively efficient economically, but less so environmentally: the typical building frame could have 40–60% less embodied carbon, and be approximately 10–20% cheaper with the right selection. We show how more complex frames have higher embodied carbon than simpler grids. From our findings, we establish a list of design considerations that architects and structural engineers should account for when creating an initial design to lower the embodied carbon: the complexity of the layout, the optimisation of the design and the choice of the decking technology.

Corrugated plates are gaining increasing attention from researchers based on their recent extensive use in structural engineering, thanks to their potential to provide lighter and more economic structures. However, tests on the flexural behaviour of trapezoidally corrugated web girders (CWGs) are still scarce in the literature. Accordingly, the purpose of this paper is to provide the fundamental behaviour of laterally-unrestrained trapezoidally CWGs by experimental and numerical investigations. The middle parts of the specimens are loaded by pure bending moment by adopting the four-point loading process. Firstly, three CWGs are tested experimentally by changing the flange width and web height, with corrugation dimensions kept the same. The flange width varies from 80 mm to 100 mm and the web height changes from 300 mm to 400 mm. The girders are found to fail by the lateral-torsional buckling mechanism without any local flange buckling or web distortion. After that, ABAQUS software is used to increase the data required to explore the influence of different parameters on the behaviour of CWGs. The accuracy of the finite element (FE) models is verified by using the test results. This is followed by parametric studies investigating the behaviour of CWGs through the variations of the flange width, flange thickness and web height. The results indicate that increasing flange width is an effective solution for increasing the ultimate moment capacity of CWGs which is accompanied by a slight increase in the lateral displacement of the girder. Furthermore, girders with large flange widths have high load carrying capacities compared with the material used. Additionally, the results show that increasing the web height has a positive effect on the moment capacities of CWGs.

This research paper conducted a hysteretic behavior simulation on a single-span and single-storey frame composed of prestressed concrete-encased steel beams and concrete-encased concrete filled steel tube (CFST) columns. The hysteretic parameters of stiffness degradation, strength degradation and pinching behavior for members were suggested according to tested results. After that, an analytical model for corresponding out-jacketing frames with single-span and multi-storey was developed, and amounts of elastoplastic seismic response analysis were conducted for seismic fortification intensities 7 and 8 with various site-classes and design earthquake groups under rare earthquake. The results indicated that, the out-jacketing frames assigned to Intensity 7 with Site-classes I0 to III behaved perfectly in seismic collapse resistance performance, which could be designed as regular frames by using China's current codes; while referring to Intensity 8, a certain amount of out-jacketing frames assigned to Site-classes I0 to III had inter-storey collapse mechanism, and several design proposals were developed to prevent collapse failure by measurements of enhancing seismic grade.

In real engineering, with the gradual deterioration of mining geological conditions, the improvement of the bearing performance of fully grouted bolts is beneficial to better control of the roadway surrounding rock. For this purpose, based on the idea of steel fiber reinforced concrete, a systematic laboratory study was conducted to investigate the effect of steel fiber grout on the bearing performance of anchored specimens. Three steel fibers with different diameters (0.5, 1.0 and 1.5 mm) were selected. Fiber specimens and fiber-free specimens were prepared and a series of pull-out tests were conducted. The experimental results show that the steel fiber grout can effectively improve the bearing performance of the anchored specimens and enhance the anti-destructive ability of the anchored specimens. The steel fibers in the grout can enhance the mechanical interlocking effect, the dilatancy effect and the friction effect of the anchoring interface, thereby improving the ability of the anchored specimen to withstand additional loads. The reinforcement effect of steel fiber on the bearing performance of the anchored specimens presents an obvious diameter dependence. With the increase of the steel fiber diameter, the bearing properties of the anchored specimens tend to increase and the cumulative AE counts, cumulative AE hits, cumulative AE energy and AE events also increase. Moreover, the steel fiber grout can more fully mobilize the bearing performance of the anchoring interface, and the number of microcracks in the fiber specimens increases during the bearing process. This research results may provide a useful reference for the support design of fully grouted bolts.

The environmental impact of traditional Ordinary Portland Cement (OPC) concrete is a significant problem that requires urgent solutions in the construction industry. The development of geopolymer concrete is one of the most significant breakthroughs in the process of replacing OPC concrete. Through comprehensive experimental and numerical analyses, this study investigates the structural behaviours of large-scale steel reinforced geopolymer concrete beams (GCBs) made from low-calcium fly ash and ground granulated blast furnace slag (GGBFS). Firstly, small-scale experiments were carried out to investigate the effects of water/binder and activator/binder ratios on the mechanical properties of geopolymer concrete (e.g. elastic modulus, compressive strength, direct tensile strength). The experimental results show that the mechanical properties of geopolymer concrete increases with increasing the activator/binder ratio and decreasing the water/binder ratio. Secondly, three groups of GCBs with different steel reinforcement ratios (D1-0.41%, D2-0.75%, and D3-1.5%) were made and four-point bending tests were conducted. The same mix proportion (water/binder of 0.45 and activator/binder of 0.08) with the compressive strength of 39.1 MPa, elastic modulus of 32.0 GPa, and the direct tensile strength of 3.06 MPa, was used for the three groups. The obtained moment–curvature results, which consists of three distinct stages (linear elastic, tension cracking of GCBs, and steel yielding), show that the three groups (D1-D3) behave in a ductile manner. Moreover, the moment capacity of GCBs increases when the steel reinforcement ratio increases (D1-21.5 kNm, D2-44.2 kNm and D3-83.6 kNm). Finally, nonlinear, three-dimensional finite element (FE) analysis based on the damage plasticity constitutive law was developed to capture and validate the structural behaviour of GCBs from the experiments. Numerical results indicate that the developed FE models accurately capture the structural behaviours (moment–curvature and cracking behaviour) of GCBs. The discrepancies between the numerical and experimental moment–curvature results are from 1 to 5% for the tensional cracking and yielding points. Therefore, the developed FE models can be used as an effective tool for the further development and design of geopolymer concrete structures.

The three mechanisms governing the strand-concrete (S-C) bond in pretensioned concrete (PTC) systems are: (i) adhesion, (ii) mechanical interlock, and (iii) friction. These mechanisms can be influenced by various parameters like the compressive strength of concrete (fc), applied prestress (fps), and embedment length of the strand (le). The existing test methods for S-C systems use unstressed strands and defines bond strength (τb), as the stress corresponding to a slip of 2.5 mm at free end (say, τ2.5). The unstressed strands and τ2.5 approach may lead to unconservative results and significant scatter. This paper presents the experimental program on the effects of fc (43 and 62 MPa), fps (0.1 fpu and 0.7 fpu), and le (500 and 1000 mm) on the bond stress-slip (τ-s) behaviour in PTC systems. Analysis of the results of tests on 24 specimens indicated that (i) defining the τb as τ2.5 at the free end is not suitable for PTC specimens and (ii) the τ2.5 at live end exhibits significant scatter and is dependent on the embedment length, le. Consequently, the paper proposes a conceptual model on strand-concrete bond behavior and a rational method to determine τb as the stress corresponding to the yield bond stress (τyield). The determined τyield is independent of fps and le and exhibits less scatter than τ2.5. Finally, the use of taut strand specimens is recommended as they are easier to prepare than stressed strand specimens, to determine τyield.

Deep-water bridges located in a V-shape canyon may suffer from spatially varying ground motions due to the canyon topography. This paper focused on the effect of canyon topography on the seismic responses of a deep-water continuous rigid-frame bridge that crosses a V-shape canyon. The ground motions in three example sites with different topography conditions were simulated by the numerical spectral element method. A database with one hundred point-sources considering the uncertainties of seismic magnitude and source location was sampled and adopted to simulate the seismic waves propagating from the source to the bridge site. Nonlinear seismic response analyses of the example deep-water bridge were performed under the simulated spatially varying ground motions considering the hydrodynamic added mass on the piers. The effects of the canyon topography on the seismic wave field, peak ground acceleration at bridge foundations, and seismic responses of the bridge were analyzed. According to the example studies, the canyon topography induces a significant spatial variation of the ground motions for the bridge in the canyon. Compared with the canyon topography, the influence of water within the canyon on the ground motion is slight. Neglecting the effect of canyon topography leads to the inappropriate assessment of the seismic fragility of the deep-water bridge in both component and system levels.

In this paper, the mechanical properties of polyvinyl chloride (PVC)-coated woven fabric at high-temperature and after exposure to high-temperature were studied using a uniaxial tensile test. The test temperature range is 20 °C to 170 °C. The high-temperature test shows that the maximum stress at 170 °C reduced to 57%−59% of that at 20 °C. The after exposure to high-temperature test of prestressing shows that the combined effect of high-temperature and constant external force enhanced the stiffness and reduced the material’s impact toughness. The experimental phenomena can be explained by polymer physics.

Existing physics-based methods for estimating the lateral strength of reinforced concrete (RC) columns lack generalization capabilities, where the methods for predicting the shear strength of shear- and flexure-shear-critical columns cannot be used to predict the flexural strength of flexure-critical columns, and vice versa. This paper proposes a nature-inspired, metaheuristic, least squares-support vector machine for regression (LS-SVMR) model for enhancing the generalization of lateral strength prediction of RC columns. The metaheuristic LS-SVMR model is a hybrid computational intelligence approach, which integrates LS-SVMR to elucidate the nonlinear mapping between influential factors and the lateral strength with a nature-inspired metaheuristic optimization algorithm, called coupled simulated annealing (CSA), to efficiently tune the hyper-parameters and facilitate the training process. The generalization performance is validated by comparison with several machine learning (ML) models using cross-validation strategies and with commonly used physics-based approaches as well as by successfully modeling the physical processes associated with variation of lateral strength of flexure-, shear-, and flexure-shear-critical columns when input predictors vary.

To mitigate the deficiency of the conventional steel frames, a novel steel frame system using rocking truss (SFWRT) and self-centering energy dissipative devices (SCED) was developed. The SCED consists of structural members, pre-tension tendons, abutting element and friction dissipation devices, which exhibits excellent self-centering and energy dissipation capacity. This new structural system is analyzed using Incremental Dynamic Analysis method (IDA). A scaled earthquake acceleration response spectrum from a specified ground motion was used in this analysis. It is found that the formation of the plastic hinges of the structural components includes four stages: emergence, developing, degradation and completely bearing capacity loss. A comparative study is also made to investigate the development of these plastic hinges under different ground motions in both traditional steel frame and SFWRT. The results for evaluating the lateral collapse resistance capacity indicate that the rocking truss can significantly decrease the structural dynamic response and improve the seismic performance of buildings. The collapse probability curves of the steel frame and SFWRT based on three limit states are compared. It is found that the rocking truss is helpful to reduce the collapse probability under earthquakes. The damage of the steel frame as well as the expected loss of the main structure after an earthquake can be significantly reduced with the help of rocking truss, which would also reduce the repair cost and improve the structural resilience under earthquakes significantly.

The present work deals with the improvement of the seismic performance of a Single Story-Single Bay Special Truss Moment Frame (STMF) by incorporating Shape Memory Alloys (SMAs) as dissipation devices in the special segment, which can recover their initial geometry after mechanical distortion by unloading through the phase transformation (martensitic-austenitic phase). STMFs were initially designed with a special segment located in the middle of the truss to dissipate the input energy through the formation of plastic hinges at the four corners of the chord members. This mechanism is replaced with the input energy dissipation through the SMA deformation in a pin-ended special segment. In what follows, the frame at hand is examined incorporating SMA bars per diagonal of either 0.025 m or 0.035 m in diameter, restrained against buckling, simulated via a 4-DOF mechanical model consisting of two lumped masses, under selected ground motions. To further evaluate the performance of the frame with SMAs incorporated and at the same time verify the model, a non-linear dynamic time-history analysis is conducted using SeismoStruct Finite Element software. The response of the proposed system is compared with the one of the conventional one. Results show that the proposed system leads to a decrease of the maximum displacement and potentially allows a much lighter construction.

Fundamental concepts of the developed site load-factor approach for the assessment of existing bridges are introduced in this contribution. The method is complemented by the calibration of the partial factors accounting for uncertainties. The calibration is crucial for the simple application of the method in concordance with semi-probabilistic approaches commonly presented in design guidelines. As means of verification of the proposed methodology, a reliability analysis of the site load factor approach is offered to assure that the intended safety level required by codes is achieved. Results indicate that reductions of the static load effects mandated by design stipulations can be implemented, while maintaining the required safety levels. The methodology presented here is developed in the context of data collected in South Africa, nevertheless the framework is general and can be extrapolated to any other country or dataset.

To reduce the amount of reinforcement and control crack width, ultra-high strength rebar reinforced Engineered Cementitious Composites (UHSRRE) beams are considered a promising choice. A model is developed for predicting the flexure deflection of UHSRRE beams in service stage based on internal force equilibrium and the compatibility of deformation. In this model, the bilinear stress–strain model for Engineered Cementitious Composites (ECC) and ultra-high strength rebar is adopted, and the tensile zone of UHSRRE beams is considered. The flexure tests of seven beams with different reinforcing ratios and matrix materials are carried out for verifying the proposed model. It is observed that the experimental results are basically consistent with the predicted results. This model can provide a useful tool for the calculation of deflection. Additionally, parametric analysis is conducted to analyze the influence of reinforcement bars and matrix materials on the bending deformation of UHSRRE beams. Through comparison of the results, it is found that using higher strength grade bars not only reduces the amount of reinforcement but also maintains excellent bending performance.

The construction of bridge substructures by in-situ assembly of precast concrete segments provides significant benefits in quality control and economy, but their seismic stability is always a concern. Incidentally, prefabricated components have long been used in building tall pagodas for thousands of years in China. Among the pagodas that have survived numerous centuries, the timber pagodas are believed to be assembled structures of great research value in respect of seismic isolation design. There is indeed a certain degree of similarity between the timber pagodas and the proposed precast segmental bridge columns with resettable sliding joints. The smart seismic isolation mechanism in multi-storey timber pagodas with mortise-tenon rocking columns and distributed bracket sets has the following key features: (a) high lateral flexibility, (b) smart energy dissipation system, (c) guided self-centring behaviour, and (d) measures to enhance vertical stability. Actually, the resettable sliding joints in the present precast segmental bridge columns are so designed and distributed to obtain a similar seismic isolation mechanism. Time-history simulation results of seven conceptual models show that the columns with resettable sliding joints outperform the other counterparts especially in respect of (a) the overall seismic isolation between the top mass simulating the deck and the shaking ground, (b) the control of residual sliding displacements at segment interfaces, and (c) satisfactory energy dissipation performance.

Recently, a new generation of roll-formed aluminium sections have been produced by BlueScope Permalite Australia and utilized in structural systems. However, limited research has been conducted to investigate their buckling instabilities including web crippling failure. The empirical nature of the current design guidelines may also lead to inaccurate estimation to their web crippling capacities. Therefore, this study aims to investigate the web crippling behaviour of and the design considerations for roll-formed aluminium lipped channel (ALC) sections using a combination of experimental study and finite element analysis (FEA). In total, 40 ALC specimens were tested under one-flange loading conditions with flanges being restrained to the supports (Fastened). Non-linear finite element models were also developed and validated against the experiments. An extensive parametric study was subsequently conducted to extend the range of geometrical dimensions and aluminium alloy grades of ALC sections. Further, the applicability and accuracy of the design rules given in the American, Australian, and European specifications were assessed. It was found that most of these guidelines yield either unconservative or over-conservative predictions of the ultimate web crippling capacities, and hence suitable modifications were proposed. Predictions due to the modified design rules showed a good agreement with both experimental and numerical results, and are hence recommended to be incorporated in relevant aluminium standards.

Lateral responses of a pile are governed by its mutual interaction with the supporting soil, known as the Pile-Soil Interaction (PSI), which in turn influences its structural limit states. The present study evaluates the seismic limit states for bridge pile in sand, while incorporating the parametric influences of pile and soil assessed through PSI. Such influences have not been dealt with in the past, except for the p (soil-pile reaction) – y (pile deflection) responses (though with only few pile parameters). Pile cross sectional size, grades of concrete and reinforcement, longitudinal and transverse reinforcement ratios, axial load ratio and the sand effective friction angle are observed to affect the PSI and consequently the limit states. Thus, limit states are proposed as parameterised expressions, generated through regression on the limit state data obtained by analysing the damage model (developed herein) for the pile-soil system samples generated over wide ranges of the influential parameters. These expressions, validated through the compliance with the expected trends and a fair agreement with a test result, can be readily used to obtain the expected values of the limit states over a broad range of parametric combinations and without requiring analysis repetition. These, in turn, can contribute to reliable estimation of fragility of a bridge system with the given properties for its pile foundation.