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This study deals with the behaviour of duplex stainless steel bolted connections. The aim of the study is to respond to the question if the current stainless steel design specifications are able to predict the behaviour of such connections. Firstly, the net cross-section capacity of duplex stainless steel plates subjected to tensile loading are presented. They were conducted to obtain the stress–strain curves and tensile fracture behaviour used to support the finite element (FE) fracture simulations. Secondly, nonlinear FE models are developed for duplex stainless steel bolted connections subjected to tensile loading. The FE models are validated against experimental data in terms of load–displacement curves, failure modes and ultimate loads. Then, a numerical parametric study that consists of 133 duplex stainless steel grade EN 1.4162 bolted connection specimens is carried out. The failure modes of bolted connections are carefully examined, including combined tear out and bearing, bearing and net section, looking at the influence of parameters such as end distance, edge distance and spacing between the bolts in the connections. The results are compared to the design rules prescribed in the current stainless steel design specifications. Generally, it is found that the Australian/New Zealand (AS/NZS), American (SEI/ASCE) Specification and European codes conservatively predict the ultimate strengths of the bolted connections, whereas the strengths predicted by the AS/NZS and SEI/ASCE specifications are overall more accurate and less scattered.

Light-gauge Steel Framed (LSF) floor panels are commonly employed in conventional and modular building constructions on the basis of their lightweight nature. Previous research studies on the fire performance of LSF floor panels have been limited to Cold-Formed Steel (CFS) lipped channel and hollow flange joists. Therefore, there is a need for research on the fire performance of the LSF floor panels designed with optimised CFS joists in conventional floor panels and modular floor panels. This paper focuses on the fire performance of LSF conventional and modular floor panels made of optimised CFS joists found in the literature, using Finite Element (FE) analyses. Heat transfer FE models of LSF floor panels were developed and validated against the data available in the literature. Subsequently, the validated FE models were extended to investigate the LSF conventional and modular floor panels made of optimised CFS joists. In total 32 different LSF modular and conventional panels were analysed. A load ratio-critical average joist temperature relationship was derived based on the past test results and extensive FE results. The established relationship in conjunction with time-temperature profiles from the FE analysis was used to predict the Fire Resistance Rating (FRR) of the LSF conventional and modular floor panels made of optimised CFS joists. The results showed that modular floor panels withstand significant standard fire loading compared to the conventional floor panels while optimised CFS joists can also be used to enhance the fire performance.

A dynamic stiffness element for flexural vibration analysis of delaminated multilayer beams is developed and subsequently used to investigate the natural frequencies and modes of two-layer beam configurations. Using the Euler-Bernoulli bending beam theory, the governing differential equations are exploited and representative, frequency-dependent, field variables are chosen based on the closed form solution to these equations. The boundary conditions are then imposed to formulate the dynamic stiffness matrix (DSM), which relates harmonically varying loads to harmonically varying displacements at the beam ends. The bending vibration of an illustrative example problem, characterized by delamination zone of variable length, is investigated. Two computer codes, based on the conventional Finite Element Method (FEM) and the analytical solutions reported in the literature, are also developed and used for comparison. The intact and defective beam natural frequencies and modes obtained from the proposed DSM method are presented along with the FEM and analytical results and those available in the literature.

Suction caisson foundations provide options for new foundation systems for offshore structures, particularly for wind turbine applications. During the foundation design process, it is necessary to make reliable predictions of the stiffness of the foundation, since this has an important influence on the dynamic performance of the overall support structure. The dynamic characteristics of the structure, in turn, influence its fatigue life. This paper describes a thermodynamically consistent Winkler model, called OxCaisson, that delivers computationally efficient estimates of foundation stiffness for caissons installed in homogeneous and non-homogeneous linear elastic soil, for general six degrees-of-freedom loading. OxCaisson is capable of delivering stiffness predictions that are comparable to those computed with three-dimensional finite-element analysis, but at a much lower computational cost. Therefore, the proposed model is suited to design applications where both speed and accuracy are essential, such as large-scale fatigue assessments of offshore wind farm structures. The paper demonstrates that the OxCaisson model can also be applied to short, rigid monopile foundations.

In the present work, cohesive and overlapping crack models are integrated in a comprehensive numerical algorithm in order to investigate both tensile and compressive failures in plain or steel-bar reinforced concrete (RC) structural elements. These two fracture mechanics models offer a high capability in the investigation of non-linear phenomena occurring in the loading process of plain concrete or RC beams subjected to bending. Based on the crack-length control scheme, these non-linear models are able to describe snap-back and snap-through instabilities, crack formation/propagation, steel yielding/slippage, concrete crushing and scale effects on the structural brittleness. In the present work, some parametric studies are carried out on plain concrete or RC beams in order to highlight how the abovementioned structural phenomena, which are observed in engineering practice, can be effectively captured by means of a non-linear fracture mechanics approach. Moreover, dimensional analysis is adopted to confirm how the behaviour of lightly reinforced concrete beams can be effectively described by means of two non-dimensional brittleness numbers, leading to a scale effect on the minimum reinforcement percentage, ρmin, proportional to beam depth raised to −0.15.

This paper deals with an evaluation of the generalised partial safety factor for resistance properties by using a statistical determination of a resistance model for predicting the punching capacity. The factor takes the material, model and geometric uncertainties into account. The Eurocode 2 design model for the assessment of the punching resistance without shear reinforcement was statistically analysed using an extensive database of experimental tests. The correction factor b of the model and the coefficient of variation of the model errors were evaluated according to Annex D of EN 1990. The statistical parameters of the basic variables in the resistance functions were assumed according to the recommendations of the Joint Committee on Structural Safety Probabilistic Model Code. The comparison of the safety factors obtained with the material safety factor currently used reveals that the current factor 1.50 underestimates the values obtained for the design model analysed.

Seismic assessment of reinforced concrete (RC) buildings heavily relies on the deformation capacity predictions of members. Similarly, the prediction of the deformation capacity of retrofitted RC columns has the utmost importance for seismic retrofit design. In this paper, a new unified drift model is proposed in order to estimate the rotation capacity of RC columns retrofitted with concrete jacketing, steel jacketing and fibre-reinforced polymer (FRP) wrapping. In order to generate the model, an extensive database was compiled consisting of 269 columns composed of 39 concrete-jacketed, 91 steel-jacketed and 139 FRP-wrapped RC columns failing in flexure mode. In the proposed drift model, the key model parameters are the confinement stress ratio, the axial load ratio and the lap splice length. The accuracy and scatter of the estimations with regard to the previous models were studied. For all of the column retrofitting options, the proposed unified model was observed to have rotation predictions better than the previous models in terms of the mean of the predicted to experimental rotation capacity ratios and with a reduced standard deviation.

Prestressed hollowcore slabs are potentially critical segments in the construction sequence of a precast concrete structure, in which very early age strength is vital for ensuring factory productivity. Importantly, the construction industry is striving to reduce concrete's carbon footprint by using Portland cement substitutes, particularly using ground granulated blastfurnace slag (GGBS) in Ireland. This paper investigates the early age strength enhancement methods for slag-concrete mixes, in order to address the well-known retarding effects arising from slag's inclusion. The strength enhancement methods, including temperature curing and a novel accelerating admixture, are used to activate the slag in the concrete mixes, with replacement rates up to 50% GGBS. The efficacy of these methods is investigated in relation to establishing the development of compressive strength and modulus of elasticity over time (being relevant to stress transfer), particularly at very early and at later ages for strength compliance. The study demonstrates the potential for using up to 50% GGBS mixes for slab production while still maintaining the strengths sufficient to achieve existing productivity targets in precast concrete production.

Seismic isolation systems exposed to far-fault earthquakes can reduce floor accelerations and story drift ratios to acceptable levels. However, they exhibit different structural performances in each earthquake due to different excitation frequency contents. By optimizing the isolation system parameters, their performance may be maintained at the best level under different far-fault earthquakes. In this study, the optimization of the parameters of the nonlinear isolation system of a 5-story benchmark building is performed by Teaching-Learning Based Optimization (TLBO) algorithm to minimize peak floor accelerations under historical far-fault earthquakes with and without exceeding a specified base displacement limit. According to the results of the analyses, it can be said that TLBO algorithm is a robust algorithm with low standard deviations for determining optimum nonlinear isolation system parameters.

A modified design method of a novel large-span floor system called an open-web sandwich slab (OWSS) is discussed. By considering some crucial parameters ignored in current design procedures, a new design procedure based on experiments and simulations is proposed. Considering the dimensions of the shear keys, the linear stiffness of the chords and the linear stiffness ratio between the chords and the shear keys, four specimens were tested and the failure modes and plastic behaviour of the specimens were studied. Based on the experimental results, a series of finite-element simulations was conducted and a crucial integrality coefficient was proposed. Based on the tests and simulations, a modified design procedure was then developed, with recommended values of some crucial coefficients. Finally, a case study was examined to show the efficiency of the new design procedure and the advantage of the OWSS; the results showed that the newly designed OWSS had advantages compared with a traditional solid beam.

A ‘locking-bolt’ demountable shear connector (LBDSC) is proposed to facilitate the deconstruction and reuse of steel-concrete composite structures, in line with achieving a more sustainable construction design paradigm. The LBDSC is comprised of a grout-filled steel tube and a geometrically compatible partially threaded bolt. The latter has a geometry that ‘locks’ the bolt in compatible holes predrilled on the steel flange and eliminates initial slip and construction tolerance issues. The structural behaviour of the LBDSC is evaluated through nine pushout tests using a horizontal test setup. The effects of the tube thickness, strength of concrete slab, and strength of infilled grout on the shear resistance, initial stiffness, and ductility of the LBDSC are assessed. The experimental results show that the LBDSC can achieve higher shear resistance and similar initial stiffness as compared to traditional welded studs. In addition, all tested LBDSCs exhibited slip capacities ranging from 14 to 32 mm and can be classified as ductile shear connectors according to Eurocode 4. A detailed finite element model was also created and found to be reliable to reproduce the experimental behaviour. Parametric studies were subsequently conducted using the validated model to study further parameters and generalise the experimental results. Due to the specific test setup, non-negligible uplift forces were generated in the connector and the potential implications are discussed.

In order to improve the performance of wet joints in prefabricated ultra-high-performance concrete (UHPC) bridges, a comparative study was conducted to investigate the flexural behaviour of UHPC joint beams. Experimental tests were implemented on a complete beam and on five further specimens with, respectively, vertical joint, rhombus joint, vertical joint with strips, tied rhombus joint with strips, and welded rhombus joint with strips. The specimens’ failure modes, ultimate flexural capacities, strain distributions and load–deflection curves were investigated. The test results show that the flexural capacity of the joint beams is lower than that of the complete beam. Among the five specimens with wet joints, the welded rhombus joint with top and bottom strips had the greatest stiffness, the highest cracking resistance capacity, and the best flexural performance. From the best to the worst performing, the remainder of the wet joint specimens took the following order: the unwelded rhombus joint with strips, the vertical joint with strips, the rhombus joint and the vertical joint. In accordance with the test results and the related theoretical analysis, this paper proposes formulas to calculate the flexural capacity of the beam with UHPC joints.

Civil infrastructures are vulnerable to catastrophic failures when exceeding the limit loading, requiring a reliable structural control mechanism, such as bracing systems, to enhance the integrity and stability of the structure. Bracing systems improve the performance of the structures by increasing the stiffness/strength of structures, the damping coefficient, and/or the energy absorption capacity. However, the functionality of these bracing systems is not controllable and may be altered after strong seismic events. Recently, the smart bracing systems based on multifunctional materials, particularly the shape memory alloy (SMA) and the magnetorheological fluid (MRF) have been developed. The superelasticity properties of SMA give the capability of recovering the original state after remarkable deformation. Furthermore, the SMA dissipates the energy of the applied load in the loading-unloading mechanism. The viscosity of MRF is variable and depends on the intensity of the applied magnetic fields. In the present study, a state-of-art hybrid SMA-MRF-based core bracing system is designed and in-house fabricated to enhance the structural behavior of the bracing system, including energy dissipation capacity and equivalent damping coefficient. Experimental tests have been conducted to illustrate the functionality of the system and the benefits of the SMA and the MRF systems. Finally, the seismic performance of the three-, six- and nine-story buildings equipped with the proposed SMA-MRF damping system is numerically assessed using nonlinear response history analyses. The results reveal that the proposed damping system significantly improves the seismic performance of the archetype buildings.

Failure of unreinforced masonry following the 2011 Christchurch earthquake demonstrated that many masonry strengthening solutions were inadequate for the peak ground accelerations that were experienced, and also that many of the failures were associated with underperformance of masonry anchors. Recent in-situ pull-out tests of anchors in vintage masonry structures has identified that in these tests, the failure is predominantly via splitting of the masonry units. This finding is in contrast to current design approaches that only consider failure via the formation of a cone or wedge, or masonry unit extraction. To further examine the potential for unit splitting prior to the failure modes identified in current design approaches, a laboratory campaign investigating masonry unit properties and anchor pull-out capacities, covering quasi-static, cyclic and impact loading of anchors and also incorporating the influence of quality of installation is reported here. The results of this campaign confirm that the unit splitting is an important failure mode, which may explain the observed anchorage underperformance. It is further observed that whilst cyclic and impact loading, as well as poor quality of installation have a detrimental effect on anchor performance, performance nonetheless exceeds published characteristic strengths. Additionally, as part of the laboratory campaign, a simple method for supporting masonry test units has been developed which has demonstrated good replication of the in-situ test results.

This paper utilises non-linear finite-element analysis with three-dimensional (3D) solid elements to gain insight into the role of shear reinforcement in increasing punching shear resistance at internal columns of flat slabs. The solid element analysis correctly captures the experimentally observed gradual decrease in concrete contribution to shear resistance with increasing slab rotation and the failure mode but is very computationally demanding. As an alternative, the paper presents a novel approach, in which 3D joint elements are combined with non-linear shell elements. Punching failure is modelled with joint elements positioned around a control perimeter located at 0.5d from the column face (where d is the slab effective depth). The joint elements connect the nodes of shell elements located to either side of the punching control perimeter. The punching resistance of the joints is related to the slab rotation using the failure criterion of the critical shear crack theory. The joint-shell punching model (JSPM) considers punching failure both within the shear-reinforced region and due to crushing of concrete struts near the support region. The JSPM is shown to accurately predict punching resistance while requiring significantly less computation time than 3D solid element modelling.

In this experimental study, Glass Fiber Reinforced Polymer (GFRP) plates were used to retrofit timber I-joists having a top flange-notch or a web-hole. Three types of GFRP reinforcing plates were used to retrofit and test 27 flange-notched and 27 web-holed I-joists for 3.65 m and 6.1 m span lengths. Another 200 I-joists were also tested to compare the performance improvement of the GFRP retrofitted I-joists. These I-joists had two different sizes of flange notch (100 mm × 100 mm and 100 mm × 150 mm) and two different diameters (150 mm and 200 mm) of web-hole located at different locations from the support. Although North American codes do not allow any form of a notch in the flange of I-joist, the current study shows that full capacity restoration can be achieved with proper retrofitting. From the four-point bending test of the I-joists, it is observed that GFRP plates can improve the structural capacity of retrofitted flange-notched or web-holed I-joists up to 605% and 106%, respectively, compared to the capacity of I-joists with a flange notch or a web hole, respectively. Two prediction models proposed here can predict the structural capacity of the retrofitted flange-notched and web-holed I-joists with different GFRP reinforcements with reasonable accuracy.

Seismic response of masonry towers has been widely studied, whereas research on their behavior under other dynamic forces is not common. The aim was to study the dynamic effects of bell swinging on a masonry tower, evaluating the response through different approaches. For this purpose, the south tower of the National Palace of Mafra was adopted due to its slenderness and its four swinging bells located at 49 m height. Dynamic identification tests allowed to determine the tower’s dynamic properties aimed at calibrating a numerical model. Frequency analyses assessed possible resonance effects by comparing the frequencies of the excitations with those of the tower. Nonlinear dynamic analyses evaluated the response in terms of displacements and cracking, while nonlinear static analyses determined damage patterns assuming different load combinations. Variations of structural stiffness and intensity of the forces were also studied. The results demonstrated that the tower, subjected to bells action, remains within the elastic range with a high safety level. Moreover, crack patterns correspond to local damage, which do not compromise the stability of the structure. Finally, parametric analysis allowed to obtain equivalent static load factors for bells of the Spanish system., This work was performed in the University of Minho with the funding from the ELARCH Program (Euro-Latin America partnership in natural Risk mitigation and protection of the Cultural Heritage), an Erasmus Mundus Action 2 Partnership (552129-EM-1-2014-1-IT-ERA MUNDUS-EMA21) by the European Commission and coordinated by the University of Basilicata, Italy.

To facilitate construction and on-site quality testing, a new type of panel joint using cast-in-place connecting beams was developed and studied. The proposed connecting beams consist of overlapping vertical U-shaped steel bars stretching out of the wall and the footing, longitudinal prestressed steel strands, L-shaped steels and infilled high-strength grout. One monolithic shear wall specimen and five precast specimens were tested under simulated seismic loads. The test parameters studied included the presence or absence of L-shaped steel, sectional depths and the locations of connecting beams and locally non-bonded U-shaped steel bars. The effects of these parameters on the failure modes, hysteresis curves, stiffness, ductility and energy dissipation capacity were evaluated. The test results showed that the precast shear walls with the proposed panel joint achieved desirable seismic behaviour – comparable to or better than that of monolithic specimens – and can thus be safely applied in buildings in seismic zones. The use of L-shaped steel, prestressed steel strands and high-strength grout effectively delayed concrete crushing at the wall toes and thus improved the loading capacity, deformation capacity, initial stiffness, ductility and energy dissipation capacity of the precast shear walls.

There is a global drive to promote and optimize the design of high performance buildings at low cost and minimum environmental impact. Although reinforced masonry construction is known for its better fire protection, structural durability, and construction cost reduction, its use is hindered by a lack of understanding of its resistance to earthquake loads. This research aims to quantify the effect of influential parameters on the seismic performance of Reinforced Masonry Shear Walls (RMSW) with masonry boundary elements (MBEs). A new system/configuration for RMSW with C-shaped masonry units has been proposed. A new experimental test setup was designed and built to capture the response of the lower panel of RMSW in a 12-storey building subjected to quasi-static loading protocol. Test results showed that the proposed system could provide the lateral strength and ductility required to resist earthquake events and that the average measured compressive strain was almost four times the limit specified in CSA S304-14. The results also showed that single out-of-plane support at the loading beam level was inadequate, leading to out-of-plane failure. When additional out-of-supports were provided, the failure mode changed to web crushing and buckling of vertical web reinforcement.

This paper studies the method of determining the fracture parameters of pre-notched concrete beams with horizontal pre-set cracks and the influence of fracture intersection on fracture characteristics of concrete based on the three-point bending test. Pre-notched concrete beams with horizontal pre-set cracks were designed as 13 groups according to the different positions, lengths and widths of horizontal pre-set cracks. The fracture toughness was calculated on the basis of the cohesive force model of concrete, and the crack opening displacement obtained by using the digital image correlation technique. The study's results indicate that the distance between the pre-set crack and the notch tip as well as the pre-set crack length and width have various influences on the fracture propagation of edge mode I crack, the bearing capacity and unstable fracture toughness of concrete beams owing to varying degrees of loss of cohesion in the fracture process zone (FPZ). The study also finds that a large lack of cohesion in the FPZ indicates a high possibility of a reduction in the bearing capacity and unstable fracture toughness of concrete beams.

The punching and post-punching shear behaviours of reinforced concrete (RC) flat plate structures are often studied by using a representative slab–column connection isolated from the parent structure. In this study, a set of numerical modelling techniques is established to create a competent three-dimensional non-linear model to simulate punching and post-punching shear behaviours of RC slab–column connections without shear reinforcement, through the use of which the punching shear failure featuring a critical punching shear surface and an abrupt drop of the applied force in the load–displacement response is able to be accurately reproduced. The post-punching shear behaviour, taking the form of an increased load-carrying capacity which is ceased by rebar fracture in the suspension stage, is also well captured. Using the proposed numerical model, typical punching and post-punching shear failure mechanisms are studied in some detail.

Floor systems constructed from slabs and beams are critical structural elements of reinforced concrete (RC) frame structures, allowing them to resist progressive collapse. To elucidate the complex effects of the slab and its thickness on the progressive-collapse resistance of RC spatial frame structures, three 1/3-scale 2 × 2 span substructure specimens, including one three-dimensional (3D) skeletal frame substructure and two 3D frame–slab substructures with different slab thicknesses, were tested in a middle-column-removal scenario. The test results indicated that the frame–slab substructure exhibited two resisting progressive-collapse stages: a primary mechanism stage, with small deformations, and a secondary mechanism stage, with large deformations. The slab contributions were separated from the floor system and quantified by comparing the results for the skeletal frame substructure and frame–slab substructure. Although there were no in-plane confinements, the slab also significantly improved the resistance against progressive collapse, owing to the compressive and tensile membrane action in the primary and secondary mechanism stages, respectively. Increasing the slab thickness increased the compressive membrane action of the slab, which significantly enhanced the progressive-collapse resistance under small deformations. However, under large deformations, the beam and slab did not work synergistically, which limited the development of secondary mechanisms against progressive collapse.

The artificial potential field method is usually applied to the path planning problem of driverless cars or mobile robots. For example, it has been applied for the obstacle avoidance problem of intelligent cars and the autonomous navigation system of storage robots. However, there have been few studies on its application to intelligent bridge cranes. The artificial potential field method has the advantages of being a simple algorithm with short operation times. However, it is also prone to problems of unreachable targets and local minima. Based on the analysis of the operating characteristics of bridge cranes, a two-dimensional intelligent running environment model of a bridge crane was constructed in MATLAB. According to the basic theory of the artificial potential field method, the double-layer artificial potential field method was deduced, and the path and track fuzzy processing method was proposed. These two methods were implemented in MATLAB simulations. The results showed that the improved artificial potential field method could avoid static obstacles efficiently.

Ever-increasing scarcity of land and demand for high-rise structures has significantly contributed to the use of combined piled raft foundations (CPRF) in soft ground. However, utility, design constraints and aesthetic considerations bring asymmetry to superstructures, making structures more vulnerable during seismic excitations. Traditional design practices involve designing superstructure elements and foundation considering fixity at the base of the superstructure and ignoring soil-structure interaction (SSI) which may result in under-estimation of forces and displacement in the system. Hence, the present study aims at developing new seismic design guideline pertaining to asymmetric single and multi-storied structure supported on CPRF embedded in soft clay. Some important parameters, such as torsional coupling mode of vibration and multi-storey idealisation involving the effect of higher modes are investigated incorporating seismic SSI effect. The study broadly reveals that the torsional to lateral period ratio considerably influence the seismic response of asymmetric structural system on the piled raft foundation due to the incorporation of SSI. Furthermore, multi-storey building idealisation gives a higher estimation of response compared to single storey idealization in superstructure and pile head which may be due to the effect of higher modes of vibration and SSI

This study assesses experimentally and numerically the cyclic loading response of reinforced concrete beams with web openings and shear-flexure strengthened carbon fiber reinforced polymer (CFRP) sheets using an external bonded technique. The influence of the beams on the reverse cyclic effect including the parameters of the hysteretic failure modes, stiffness degradation performance, energy dissipation, pinching width ratio, and ductility, are discussed. A numerical approach is employed to evaluate an innovative rectangular web opening and external bonding strengthening with an FRP sheet. A numerical model was used to validate the results of the tested specimens. Appropriate simulation techniques, which characterize the properties of constitutive materials, and a concrete damaged plasticity model were used for modeling development. Further, they are incorporated to apply models with new parameters. The results indicated that the use of CFRP as a strengthening system around the opening can significantly improve the overall stiffness capacity and beam behavior under cyclic loading. In particular, the increase in the load-carrying capacity over the control beam reached 63.43% for the beam with an opening in the shear zone and 73% for that with an opening in the flexural zone. The load–displacement hysteresis loops of the tested specimens were compared with those simulated by numerical models. Good convergence between the predicted and measured results was observed under all cyclic loading rates.

Fatigue damage assessment is critical for the structural design of the wind turbine nacelle chassis. However, existing fatigue damage indicators and assessment method cannot be both fast and accurate. In this paper, we propose a quantitative support vector regression-based fatigue damage assessment (SVR-FDA) method. First, the equivalent stress amplitude (ESA) is defined to simplify the fatigue damage indicator. Second, we establish the pre-calculated ESA database, including the ESAs of the wind turbine nacelle chassis under many varying wind flow conditions. Finally, based on the pre-calculated ESA database, we establish the SVR-FDA model, which can calculate the ESA of any given wind flow condition. A wind turbine nacelle chassis fatigue damage dataset, released by Goldwind, was applied to validate the proposed method. The results demonstrated that the SVR-FDA yielded the highest assessment accuracy for the lifetime ESA, as compared with four popular machine learning algorithms, including the least absolute shrinkage and selection operator, random forest, extreme gradient boosting, and deep neural network.

Steel-concrete composite beams have been used in bridge construction for decades. Novel demountable bolted shear connectors, that allow bridge disassembly and offer high level of prefabrication, are proposed for the connection of the deck with the steel beams, as an alternative to the conventional headed studs. In terms of sustainability, bolted shear connectors facilitate the replacement of deteriorating bridge components and therefore extend the bridge design life. Despite their effectiveness, research on steel–concrete composite beams with bolted shear connectors is limited. In order to expand the available literature, this paper develops a three-dimensional finite element model to investigate the behaviour of a novel demountable shear connector for precast steel–concrete composite bridges. The connector uses high-strength steel bolts, which are fastened to the steel beam with the aid of a special locking nut configuration that prevents the slip of the bolts within their holes. The accuracy of the proposed FE model is validated by comparing its predictions with the experimental results available in the literature. Once validated, the FE model was then used to conduct a parametric study to evaluate the effect of bolt height, diameter and tensile strength, bolt pretension and the compressive strength of concrete on the load-slip behaviour, the shear resistance, the slip capacity and the stiffness of the shear connectors.

In this study, a deep learning-based axial capacity prediction for cold-formed steel channel sections is developed using Deep Belief Network (DBN). A total of 10,500 data points for training the DBN are generated from non-linear elasto plastic finite element analysis, which incorporated both initial imperfections, as recommended by the Australian/New Zealand Standard (AS/NZS 4600:2018) and residual stresses as recommended by Moen et al. A comparison against experimental results found in the literature was conducted. It was found that the DBN was conservative by 9%, 6% and 8% for stub columns, intermediate columns, and slender columns, respectively. When compared against a typical shallow artificial neural network (Backpropagation Neural Network) and a typical machine learning model (Linear regression model based on PaddlePaddle), it was shown that DBN performed around 2% better than both with the same training data. When the same comparison was made for both the Effective Width Method and the Direct Strength Method, it was found that they were conservative by 15%, 13%, and 15%, respectively. Based on the DBN output data, new and improved design equations for AS/NZS 4600:2018 were proposed.

This paper presents the application of a multi-target digital image correlation method (MT-DIC) to investigate the structural performance of structures with flat steel surfaces based on an experimental program. The displacement of a regular pattern of colored labels using the MT-DIC method and the obtained results are subsequently used to get deformations, strains, relative displacements, tension fields, and hysteresis curves of two steel plate shear walls models subjected to cyclic loading at different drifts ratios. MT-DIC operations are carried out based on a code written in the commercial software MATLAB. Results showed that the MT-DIC method is capable of capturing the in-plane deformations of the steel plate shear walls with an accuracy of 0.2 mm. The relative displacement of colored labels is used to extract the strain contours on the steel surface. The results show that the presented method can be used to extract and study the tension field angle and pattern of the steel plate shear wall under lateral load. The direction of the main compression strains is also used to study the buckling waves and pattern. Hysteresis curves of tested specimens are also obtained using this approach and compared with experimental results, which show a good agreement.

This study investigated the capacity of finite element modelling (FEM) approaches to predict the experimentally obtained behaviour of concrete-filled spiral-welded stainless-steel tube (CF-SWSST) short and long columns. Using the ABAQUS software, FEM was carried out of 24 CF-SWSST column tests. Nominal outside diameter to thickness ratios, effective length to diameter ratios and load eccentricity to diameter ratios equal to 51–114.5, 4.5–12.0, and 0–0.4 had been considered for the tests that were modelled. The distinct spiral weld seam geometry of the SWSST was explicitly considered in the FEM. Widely reported and accepted FEM modelling approaches and material models were adopted for this work. The concrete damaged plasticity model was utilised for the concrete core, while the stress–strain behaviour of stainless-steel was modelled using a modified Ramberg-Osgood relationship. On average, the capacities predicted by the FEM for the CF-SWSST columns were found to be non-conservative. The non-conservativeness was higher for specimens under concentric axial loading and increased with column and section slenderness. The actual to predicted capacity ratios were much closer to 1.0 for eccentrically loaded CF-SWSST columns, with conservative capacities predicted for eccentrically loaded specimens with the smallest section slenderness. For load eccentricity to diameter ratios of 0.15 and 0.4, there was negligible difference in the prediction conservativeness. Compared to analogous concrete-filled spiral-welded mild-steel tube columns, the FEM predictions obtained for the CF-SWSST columns were notably less conservative. This suggested that separate material constitutive models may be warranted for the FEM of CF-SWSSTs compared to their mild-steel counterparts. For the modelled eccentrically loaded specimens, the FEM predicted globally flexurally deformed states which agreed with those obtained experimentally, though the local buckling patterns were not replicated. In addition, the FEM qualitatively captured the experimentally obtained bending stiffness and strain variations. A modelling sensitivity study found that the FEM results were effectively equivalent even when the SWSSTs were modelled as plain seamless tubes.

The mechanical behavior of rockfall impacts on shed slabs was studied in three aspects: the rockfall impact force, the inertia effect coefficient, and the structural damage evaluation. A test model composed of a concrete slab and a cushion layer was constructed. Nine batches of impact experiments with energies ranging from 50 to 250 kJ were conducted. The dynamic impact model was established using LS-DYNA to analyze the dynamic impact response characteristics and inertia effect based on the SPH–FEM coupled method. Moreover, random sample expansions were calculated, and methods for assessing the impact force and inertia effect coefficient were proposed. In addition, the applicability of the proposed equation was verified by comparing the calculated results with relevant published experimental data and the Japanese calculation method of impact force. Furthermore, the velocity and mass of the rockfall were selected as the main control variables for damage assessment. A damage assessment index based on punching bearing capacity was established, and the level of damage was classified. Additionally, the influence of the parameters of the concrete slab and cushion layer thickness on damage assessment was analyzed. The impact resistances of the Ultra-High Performance Concrete (UHPC) and normal concrete slab were compared. The results demonstrated that the effect of impact force and the concurrent impact-induced inertia effect should be considered in structural designs. The larger the mass rockfall, the greater the damage sustained by the slab under the same impact energy. The compressive strength of concrete and the yield strength of steel have the greatest and least influence on the damage degree, respectively. A 90 cm-thick sand cushion on a slab increases the impact resistance of the slab by 25%–30%, compared with a 60 cm-thick sand cushion layer. Moreover, it was found that the UHPC concrete slab has good impact resistance, which is approximately twice that of the C40 concrete slab. One of the highlights in this paper is that the SPH–FEM coupled method is proposed to reproduce the physical phenomenon of sand pit-forming. Compared with FEM, SPH–FEM generates a simulated value that is closer to the experimental value.

A novel energy dissipation system named multi-toggle brace damper (MTBD) system is proposed in this paper. A theoretical mechanism for analysing the magnification factor of the MTBD system is established. Based on the finite element models (FEMs) simulated by ABAQUS, several single-story two-dimensional frame models with fluid viscous damper are investigated and compared with the theoretical mechanism. The magnification factors of the MTBD systems are compared with those of the traditional toggle brace damper (TTBD) systems. In addition, the dynamic responses of several three story three-dimensional reinforced concrete frame structures with different brace damper systems under various earthquake excitation levels are considered and investigated. The results show that the theoretical mechanism of the MTBD system is almost identical with the FEMs. Compared with the concrete frame with the TTBD system, the MTBD system has a larger amplification factor, a fuller hysteresis loop and a more obvious energy dissipation effect. The roof maximum displacements of the concrete frame structures with MTBD system are reduced by 41.1% on average. The MTBD system can significantly enhance the vibration control effect and reduce the dynamic response of the superstructures.

In modular steel building (MSB), connection is a critical part in the structural behavior and ability of load transferring. Previous MSB joints mainly use inter-connection plate or plug-in device, which ignore practical difficulties to hoist and install the modular unit. Therefore, this paper proposed an innovative corner-fitting connection, which is fully prefabricated and liftable. The seismic performance of the novel connection was analyzed by using finite element (FE) software ABAQUS. Numerical study of the novel joint was based on Simplified FE model and Detailed FE model. The developed FE model was verified by comparing with the test results of innovative connections in the previous references. The Simplified model for the joint was developed by using springs to connect the components. Five quasi-static cyclic loading FE analysis were performed on the innovative MSB connection to explore its load transferring capacity and seismic behavior. Results showed that weakening at the beam end can transfer the plastic hinge to the weakened position with little effect on the overall strength. The developed Simplified model can accurately predict the load–displacement curve and Von-mises stress of the joint. With these results, the cyclic response can be incorporated into the Simplified global model by defining the stiffness and dashpot coefficient of the spring. This paper proposed an engineering practical joint and Simplified FE model for seismic analysis of MSB, which is useful for the rapid development of this promising construction method.

This study examines the suitability of artificial neural networks (ANNs) for refined load rating estimation and bridge management. Bridge management for girder bridges commonly relies on AASHTO line girder (1D) analyses. Less conservative, more rigorous methods are permitted by AASHTO, but provide uncertain return on investment. This study demonstrates that a small set of refined analyses, coupled with ANNs, can be used as a predictive tool to anticipate the likely outcome for similar methods and bridges in a population. Two ANN-based load-rating prediction models were considered: (1) single-best-network, and (2) committee networks (CN). Load rating prediction accuracy was examined on a hybrid subset, consisting of hypothetical and real bridges representative of a steel girder bridge inventory. ANN-based prediction models were trained to map governing inputs (structural and geometric bridge characteristics) to load ratings obtained from 3D FE analyses. Prediction accuracy for bridges outside the training subset demonstrated that refined load ratings can be reliably estimated (about 5% mean absolute error) using a properly trained network model with optimized model complexity. The CN model provided improved prediction accuracy with higher confidence levels than the single-best-network approach, and exhibits less sensitivity to population size as the training sample size was reduced.

Concrete bridge piers are vulnerable to strong ground motions because of inducing significant residual drifts, which reduce the seismic resilience of bridges. A broad range of mitigation techniques is presented in the literature to reduce the vulnerability of bridge piers located in high seismic zones. Hybrid reinforced concrete piers are the most popular techniques to improve the seismic resilience of highway bridges. In addition, posttensioned segmental bridge piers are proposed as an alternative to expedite the construction procedure and also meliorate the performance of bridges in terms of residual deformations. However, very limited studies investigated the seismic performance of a whole bridge, especially for the purpose of comparing seismic resilience of the bridge columns. In this paper, a comparative study is implemented to explore the seismic vulnerability of a bridge reinforced with a hybrid configuration (i.e. combination of shape memory alloys (SMA) and normal-strength bars, and combination of high-strength and normal-strength bars) as compared to a reference conventional pier, which fully reinforced by normal-strength rebars. Moreover, a posttensioned segmental pier is considered to evaluate the strength and self-centering ability of this pier as compared to the monolithic ones. To do so, a 2D bridge model is developed in OpenSees simulation platform. Fragility curves are developed to assess the seismic vulnerability of the bridge model constructed with different piers. In this regard, a suite of 20 near-fault earthquake motions are applied to the bridge through Incremental Dynamic Analysis (IDA). Each of these records is scaled to 15 Peak Ground Accelerations (PGAs) ranging from 0.1 g to 1.5 g . The fragility curves reveal the chance of failure for each bridge model and aid in determining the impact of each pier on the seismic vulnerability of the bridge.

This study evaluates the effects of infills on the seismic resilience of special steel moment resisting frames. For this purpose, three structures of 4, 8 and 12 story are selected and designed in three different modes namely without infills, with Infills and with infills having openings. Finite element models are developed in OpenSees software. Seismic capacity and demand of structures are calculated using incremental dynamic analysis (IDA). Then, using statistical methods and probabilistic functions based on inter story drifts of the structures, fragility curves are obtained according to the HAZUS instructions. Finally, by quantifying damages, changes in seismic resilience are assessed. This makes it possible to relate the probability functions, fragility and resilience curves in an integrated approach. The results of the analysis show that infills may significantly reduce structural damages and an increase its resilience at different risk levels. The role of infills in increasing the resilience index is highlighted by the increase in risk level. This increase has been far more significant in low rise frames. It is also observed that the decreasing effect of infill openings in resilience index of high-rise buildings is less than low-rise ones although insignificant in some cases which can be overlooked.

Gradual changes of weight and geometry of vehicles combined with traffic values sometimes leads to old existing bridges having to be strengthened and retrofitted. The optimal solution to follow is based on the resistance capacity reserves of each structure, on the existing traffic level at the moment of retrofitting works and on the estimated future traffic. Almost all existing road bridges in Romania were designed according to national provisions/standards. Starting with 2010, following the European Community’s decision, the projects should be designed according to the Eurocodes and the existing bridges, must also comply with the new European load models. The process of checking existing bridges for the action of load models described in Eurocodes is a complicated task. However, the process for the evaluation of the bearing capacity reserves can be significantly simplified using a probabilistic approach. The approach presented in this paper is based on the effects, in terms of bending moments and vertical displacements, produced by several types of vehicles on the bridge superstructure. For presenting the use of this proposed methodology, typical bridge superstructures with precast concrete girders of different lengths were analyzed. The proposed methodology allows to establish the “vulnerability” of existing bridges on live loads.

There is a limited design guidance for practitioners regarding the shear design equations of circular-concrete members with fiber reinforced polymer (FRP) reinforcements, especially the case of incorporating FRP bars and spirals. The objective of this study is to enhance the methods used for estimating the shear capacity of reinforced concrete (RC) beams with FRP bars and spirals. A database of 44 circular concrete beams reinforced with FRP bars tested under shear were compiled from different experimental studies. Two proposed models based on approaches developed for rectangular sections, to predict the shear capacity of beams without and with stirrups, were compared with the selected available shear design equations. The shear strength estimated using the proposed models are slightly more accurate. The comparison indicates that the shear capacity of FRP-reinforced concrete members with circular cross sections may be determined with the V cf and Vsf approaches developed for rectangular sections provided that certain modifications are made to take into account the effective shear depth, equivalent breadth, the mechanical properties and geometry of GFRP spirals.

This article presents a study to evaluate the structural response of a cable-stayed bridge under a novel system, partially earth-anchored system with crossing cables at the main span. Six side-to-main span ratios, ranging from 0.24 to 0.39 in increments of 0.03, are tested for different bridge response parameters for both the superstructure and substructure. The loads considered in the analysis are the dead load and traffic load. Three-dimensional finite element models of the bridge are developed using structural analysis software SAP2000 and are validated based on the data available in the literature. From this study, it is found that the side-to-main span ratios have a significant effect on girder axial force and anchorage forces while having a very minor effect on cable axial forces. The results also show that the ratio does not affect the bending moment of the main span, but that when a small ratio is considered particular attention needs to be paid to the pier farther from the pylon to avoid uplifting. Deck vibration and longitudinal movement, as well as pylon longitudinal displacement, are not to be an issue for this super-long bridge.

This paper presents a combination of corrugated and flat plates to construct a seismically efficient compound section for steel shear walls. To assess the efficiency of the proposed section, a numerical and parametrical study was conducted using Finite Element (FE) software ABAQUS. The parametrical study included 45 different FE models consisting of three section types, five different length-to height ratios, and three values of plate thickness. The pushover analysis was performed for all the models. Both geometric and material nonlinearity have been considered in the analyses. The available experimental data was used to validate the FE modeling. The results indicated that the proposed wall improves the seismic parameters of the conventional steel plate shear wall. Besides the improvement of elastic stiffness, ultimate strength, and energy absorption capability, the proposed wall also reduces stress in the main frame. By reducing the imposed stress in the main frame, the ductility demand is reduced. As a result, a more economical system is achieved. Moreover, the necessary equations were suggested to achieve the push-over curve without requiring FE modeling, representing proper accordance with the FE results.

In this study, the aeroelastic active control of a suspension bridge was studied using both experimental and numerical methods. Two flat plates attached on either side of the suspension bridge were used as the control surfaces. With a suitable rotation of the control surfaces, the turbulent flow around the bridge was modified, thus addressing the problem of aeroelasticity. An appropriate feedback control law was determined using a two-dimensional numerical model. Next, a wind tunnel experiment was conducted to validate the numerical results. The numerical analysis was conducted for a suspension bridge with a span of 3000 m. The effectiveness of the control was considered based on the arrangement of the control wings along the span of the suspension bridge. The ratio between the total length of the control surfaces and the span length was investigated. The coupling of the modes of the suspension bridge also affected the control results. It was suggested that aerodynamic stability could be enhanced by using a partially installed control surface. Moreover, the buffeting responses of bending and torsion of the suspension bridge could be reduced.

A new multi-scale numerical method is proposed to simulate crack propagation in reinforced concrete structures. First of all, a three-phase composite material model is used to build the concrete structures at meso-level. And a modified Weibull distribution model is introduced to describe further the microscopic characteristics of concrete. Then different constitutive relations are adopted for components of concrete and reinforcing bars. Next, the numerical program written in ANSYS parametric design language and tool control language is executed to investigate the fracture behavior of reinforced concrete structures. The program, which can check the development of multiple cracks, is greatly improved by contrast with traditional methods. Finally, relevant experiments are conducted for comparing with the numerical results. The analysis results indicate that the program has strong robustness. Moreover, a good agreement is achieved between simulation results and experimental observation.

The geometry and the orientation of stiffener portray a crucial act in the analyses of stiffened plates. The authors have recently studied the response of bare plates under bending and buckling using a new method [1] , [2] known as the NURBS-Augmented finite element method (NAFEM). In the present work, this NAFEM is extended for investigating the response of plates with stiffeners subjected to free vibration. In its formulation, the numerical model has been made such that the straight and curved stiffeners can be placed arbitrarily with any disposition and need not be in line with the mesh grids. The stiffener’s stiffness matrix is expressed in terms of plate stiffness matrix, thus eliminating the requirement to model the stiffener separately as a beam element.

The axial compressive behavior of laminated bamboo lumber (LBL) columns with a chamfered section was investigated using 15 specimens with lengths varying from 600 mm to 3000 mm; all considered samples had same square cross section of 100 mm × 100 mm with 10 mm chamfers at each corner. Axial compression tests were carried out to analyze the impact of slenderness ratios on failure modes, strain and ultimate bearing capacity of LBL columns. Two failure modes were observed i.e. compression failure and buckling failure. Obtained results on the ultimate vertical strain and ultimate load showed a downward trend with the increase in slenderness ratios; the correlation between the ultimate strain, ultimate load and the slenderness ratios were fitted. The approximate solution method was adopted to reveal the lateral deflections of buckling columns by a quartic functional model. Based on the ideal elastic–plastic constitutive model and Hill failure criterion, FEM was carried out to simulate the axial compression tests. The simulation results agreed well with both test and theoretical results, which verified the feasibility of proposed methods used under similar working conditions in this paper.

A full-scale 3D thermo-mechanical Finite Element (FE) model was conducted in this research to investigate the effect of open-field thermal loads on the structural response of box-girder bridges. A box-girder bridge with a span of 50 m was analyzed for temperature, radiation and displacement fields using COMSOL Multiphysics. To verify the FE model, a full-scale experimental box-girder segment was constructed and instrumented with temperature, radiation and other sensors. From the experimental records, three days with extreme temperature and radiation measurements were selected. The stresses and displacements are discussed at specific points along the 24 h of the selected days and at specific times along critical sections. The FE analysis showed that the vertical and lateral stress distributions exhibited approximately similar behaviors to their corresponding temperature distributions with minor differences but with reversed sign. The results also showed that the maximum stress was compressive, which was −3.35 MPa in summer −3.83 MPa in winter. On the other hand, the maximum vertical and lateral displacements were 12.5 and 1.2 mm, respectively in summer and 2.7 and 1.9 mm in winter.

SiC/SiC ceramic matrix composites (CMCs) exhibit significant randomness of damage processes under load. In this study, a simplified simulation method was established based on the macroscopic damage constitutive model, characteristics of fewer test samples, and complex data sources for determining the randomness of the material behavior. Moreover, the established model was verified by introducing an uncertainty parameter to the constitutive model. By considering a typical high-dimensional nonlinear function as a numerical example, the reliability and error of the characterization methods were compared with specimens and studied in terms of the extreme-value interval, tolerance interval, evidence theory, and fuzzy set method with the distribution characteristics of single and mixed parameters. In conjunction with the sensitivity analysis, the randomness of the mechanical behavior was more evident at the damage stage, and the uncertainty of material behavior relied on the loading state. In addition, the correction method of the constitutive parameters and formal errors of the model were established using the Bayesian theorem to acquire additional data. Thereafter, the proposed method was employed for quantifying the uncertainty in the strength of the CMC turbine rotor blade. The determinacy results revealed that the failure risk could be more effectively evaluated by the strength analysis considering the uncertainty of the model, thus providing guidance toward structural design improvement aligned with engineering practice.

In the extension project of the China National Academy of Painting, the radial spherical plain bearing (RSPB) is used in a structural joint with an inserted plate. This new structural RSPB joint has complicated mechanical behaviors and universal rotational performance. In this work, the simulation and experiment methods were used to investigate the RSPB joint mechanical properties (uniaxial ultimate bearing capacity, failure mode) and reliability. Furthermore, the out-of-plane rotational performance was studied with eight finite models for the application. According to FEA and test results, this new RSPB joint has functional mechanical properties. It is useful in steel truss structures and provides a possibility for engineers to design hinge joints in building structures.

Based on piezoelectric ceramics' piezoelectric effect, a new type of piezoelectric ceramic friction damper (PCFD) is designed and manufactured to provide a reliable energy dissipation device for structural response control. In the PCFD, high-strength bolts limit the deformation of piezoelectric ceramics under voltage, and the resulting reaction force changes the preload of high-strength bolts, thereby realizing real-time adjustment of friction by adjusting the positive pressure on the friction surface. The influence of friction plates with different materials on the hysteretic performance of friction damper under different tightening torque is investigated by cyclic loading test to determine the friction plate's selection in the PCFD. The hysteretic performance test is carried out to evaluate the energy dissipation capacity of PCFD with different voltages, and the experimental results are compared with the theoretical values. The finite element model of PCFD is established to analyze the stress distribution of each component of the PCFD under different voltages. Based on the semi-active control characteristics of PCFD, the Takagi-Sugeno fuzzy neural network semi-active control system for frame structure with PCFD is designed. The adaptive learning function of the adaptive network-based fuzzy inference system (ANFIS) is used to generate fuzzy rules and fuzzy neural network controller (FNNC). Finally, the semi-active control simulation of three-storey frame structure model under seismic excitation is carried out by Simulink. The experimental and numerical results show that the PCFD designed in this paper has good energy dissipation capacity, and the maximum control force increases linearly with the increase of voltage. The combination of FNNC, which is established by ANFIS, and PCFD can effectively reduce the structure response.

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.