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This paper presents a novel method for the underwater crack detection by fuse the optical and texture information. Underwater crack images were influenced by the harsh underwater environment, lead to making crack detection challenging, especially difficult to capturing the details of cracks accurately. To improve detection accuracy, it was necessary to obtain more feature information related to cracks. Therefore, this paper proposes a dual-input branch semantic segmentation model to achieve the fusion of optical and texture information, and introduces the Convolutional Block Attention Module (CBAM) module to enhance the performance of the semantic segmentation model. The optimal network architecture was determined by selecting the backbone network and optimizer, and a custom Tversky loss function was introduced to make the semantic segmentation model pay more attention to the crack area. The results show that the detection accuracy, IoU, and F1-Score can reach 96.07 %, 0.95, and 0.96 respectively. Through multiple comparative experiments, the effectiveness of the proposed method was validated, particularly compared to the non-fused texture information method, where the accuracy, IoU, and F1-Score were increased by 3.30 %, 6.74 %, and 7.88 % respectively. Finally, by visualizing the variation pattern of cracks in the detection model, the operational mechanism of the proposed method was explained. This confirms that the proposed method significantly improves the accuracy of underwater crack detection, and provides a novel approach for the underwater defect detection. • A new underwater crack detection method by fusing optical and texture information. • The crack feature extraction performance of the semantic segmentation model has been improved through the CBAM module. • Feature visualization and importance analysis reveal the variation patterns of cracks in the proposed model. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study aimed at characterizing the lateral cyclic behaviour of Glulam (GL), Laminated Veneer Lumber (LVL), and Glued Laminated Veneer Lumber (GLVL) shear walls anchored to the foundation by means of conventional hold downs and angle brackets, which are fastened to the timber walls with annular ring nails. Monotonic and cyclic tests are conducted on these mechanical anchors, with hold down connections tested under tensile loads and angle bracket connections under shear loads. Withdrawal tests on annular ring nails embedded in GL, LVL, and GLVL elements are also conducted, to investigate the withdrawal response of the fasteners. The experimental tests reveal that the lateral behaviour of GL, LVL, and GLVL shear walls is similar to that of Cross-Laminated Timber (CLT) shear walls, primarily governed by the wall base connections and by the wall geometry. Hold down and angle bracket connections exhibited a mechanical behaviour governed by the steel-to-timber joints, to large extent comparable with that of typical hold downs and angle brackets fastened to CLT elements. Generally, higher ductility and lower load carrying capacity were reached by hold downs and angle brackets fastened to GL elements compared to those reached by hold downs and angle brackets fastened to LVL and GLVL elements. All quantities relevant for the seismic design, such as stiffness, load carrying capacity, ductility, and overstrength factors are calculated and discussed through the paper. These quantities are then compared with results from different experimental investigations on hold downs and angle brackets fastened to CLT elements available in the literature. Finally, an analytical model for the calculation of the lateral load carrying capacity of the shear walls is presented and used to verify that the same calculation models used for CLT shear walls can be adopted for GL, LVL, and GLVL shear walls. • The lateral behaviour of Glulam, LVL and GLVL shear walls is investigated. • The cyclic behaviour of hold downs and angle brackets fastened to Glulam, LVL and GLVL elements is investigated. • Mechanical properties and overstrength factors of the wall base connections are presented. [ABSTRACT FROM AUTHOR]

Bridge girders are subjected to repeated patch loading during incremental launching (i.e. travelling over supports). Plastic deformations are likely to occur in the girder already at the first patch loading. They influence the girder's structural response and bring about a decrease in the ultimate resistance at subsequent patch loadings. This problem is analysed in the present paper through the serviceability limit state (SLS) of incrementally launched bridge I-girders (ILBGs). The SLS of ILBGs is a current problem since only a few studies, with contrasting conclusions and certain limitations, have been recognised in the literature. Research is limited on plate girders without longitudinal stiffeners made of structural steel. Flat slide-type launching shoes are considered in this paper. The serviceability requirement (repeatable behaviour of ILBGs) and criterion (that effective membrane strains should remain in the elastic range) are adopted from the literature. So, the serviceability resistance is adopted as a load at the start of the effective membrane plastic strains in the girder. In order to propose a practical and simple SLS design procedure, the serviceability resistance is normalised against the ultimate resistance, so a serviceability correction factor (k sls) is defined. The paper presents a parametric numerical analysis of the factor (k sls). A finite element model previously developed and validated by the author is employed to simulate a nonlinear response of patch-loaded girders. The parametric study includes 599 girders. k sls is inversely proportional to the web thickness and directly proportional to the flange thickness and the yield strength of the steel material. The load length, web depth and flange width do not influence k sls. The influence of the spacing between transverse stiffeners on k sls is negligible. Finally, by regression analysis of the results of parametric study, an original and reliable serviceability correction factor is proposed as the main objective of the research. The range when the SLS of ILBGs should be checked is also defined. [Display omitted] • The serviceability correction factor (k sls) is the serviceability resistance normalised against the ultimate resistance. • A parametric numerical analysis of k sls is conducted. The numerical database contains 599 patch-loaded girders. • The load length, web depth and flange width do not influence k sls , while the influence of the spacing between transverse stiffeners is negligible. • k sls is inversely proportional to the web thickness and directly proportional to the flange thickness and steel grade. • A reliable, original and simple empirical expression for k sls is proposed. [ABSTRACT FROM AUTHOR]

This paper proposes a new mechanical model to describe the dowel action with the aim of using the model to gain a deeper understanding of the unstable dowel splitting cracking observed in shear experiments of beams without shear reinforcement. The model was developed by combining beam on elastic foundation (BEF) theory and fracture mechanics. The proposed model is able to predict the whole evolution process of dowel action until the propagation of the dowel splitting crack becomes unstable. The model theoretically proves that the development of a dowel splitting crack can become unstable under certain conditions, therefore leading to the unstable shear failure of the whole member. In addition to the derivation of the analytical model, the paper also validates the model using data from the literature. Finally, an analytical solution of the critical shear displacement that triggers the unstable dowel splitting crack is derived. It can be used to improve the failure criterion initially proposed in the Critical Shear Displacement Theory (CSDT). • A mechanical model for dowel action is proposed based on beam on elastic foundation theory and fracture mechanics. • The unstable dowel splitting cracking is theoretically demonstrated in the proposed model. • A closed-form analytical solution is derived for critical displacement for unstable cracking. • The full load-displacement response of dowel action can be obtained using the proposed model. • The proposed model can predict the experimental data with reasonable accuracy. [ABSTRACT FROM AUTHOR]

The shear strength of piers and spandrels is a crucial factor in masonry buildings, affecting structural safety. Such a strength can be increased in several ways, particularly by using fiber reinforced cementitious matrix (FRCM) reinforcements. These reinforcements can be applied symmetrically on both sides of the wall or only on one side. As it is well known, the FRCM-to-substrate adhesive properties strongly affect the effectiveness of such reinforcements. Moreover, a complete covering of the reinforced surface with bidirectional mesh evenly distributes the stresses, improving the load-bearing capacity. Appropriate test methods, for example diagonal tests, can be effectively used to evaluate the shear capacity of masonry panels, even with externally bonded composite material reinforcements, and the corresponding failure mechanism. This paper describes the results of an experimental campaign involving masonry panels, made with three different types of mortar, also reinforced with a PBO-FRCM system, subjected to diagonal tests. Through the experimental results, it was possible to determine the shear capacity of the panels, identify the failure mechanisms and evaluate the effectiveness of the FRCM reinforcements. The predictive capability of design formulas proposed in the literature for evaluating the shear capacity of unreinforced and reinforced masonry panels has been analyzed in the paper. • The results of an extensive experimental program on masonry panels subjected to diagonal tests are described in this research. • Three different types of masonry, differing for the type of mortar, and both unreinforced and reinforced panels are analyzed. • The experimental shear capacity of the panels is compared with the predictions of design formulas available in the literature. [ABSTRACT FROM AUTHOR]

This paper presents an experimental program on a series of long-span cold-rolled aluminium portal frames with various configurations subjected to different load combinations. The main structural members of the portal frame systems, including columns and rafters, were constructed using cold-rolled aluminium back-to-back built-up channel sections made from aluminium alloy 5052-H36 materials. The objectives of this paper are to understand the structural behaviour of different portal frame configurations and to explore possibilities for improving the performance of the structural systems, including strength and ductility enhancements. A total of four full-scale two-bay portal frame systems, each featuring two end frames and a central frame, were tested. The columns were braced against flexural-torsional buckling by girts spanning between the columns of the central frame and the columns of the two end frames. As a result, the portal frames failed due to in-plane sway deformations with the columns reaching their full section capacities. The tests revealed that the addition of rafter tie and sleeve stiffeners significantly improved the performance of the cold-rolled aluminium portal frame systems. Described in a separate publication, the authors also conducted a study to experimentally investigate the behaviour of the same system but with unrestrained columns, resulting in failure due to flexural-torsional buckling. Collectively, these two works form the foundation for further studies on cold-rolled aluminium portal frames in particular, and aluminium structures more generally. • Four full-scale portal frames of cold-rolled aluminium back-to-back built-up channel sections are tested. • Aluminium alloy 5052-H36 materials are used to fabricate the cold-rolled aluminium structural members and frame components. • Portal frames are tested under two loading cases, including vertical loads only and combined horizontal and vertical loads. • Braced columns of the portal frames by girts spanning between the frames enhance the load capacity of the frame system. • Rafter tie and sleeve stiffeners added to the portal frames significantly improve the performance of the portal frame systems. [ABSTRACT FROM AUTHOR]

Civil infrastructure relies heavily on structural health monitoring systems. However, these systems often encounter challenges due to sensor failures and environmental damage. Consequently, numerous anomalous data points are generated, significantly distorting the accuracy of structural safety assessments. While deep neural networks have emerged as a promising tool for efficiently identifying abnormal data, the meticulous optimization of hyperparameters during training remains a challenge. To address this challenge, this paper introduces a novel approach termed multiple transfer learning, designed to continually enhance a model's classification performance without the need for meticulous hyperparameter configurations. This methodology achieves adaptive training by iteratively migrating across bridge anomaly datasets, bypassing the need for elaborate hyperparameter setting. In this study, five distinct hyperparameter working conditions are established and evaluated to validate the effectiveness of the multiple transfer learning method. The findings highlight the robustness of this approach, demonstrating that multiple transfer learning achieves satisfactory recognition accuracy levels irrespective of the initial hyperparameter setting during network model training. This method circumvents the need for continuous hyperparameters optimization, enabling the adaptive detection of abnormal bridge data. • A training method called multiple transfer learning based on transfer learning is proposed in this paper to solve setting hyperparameters. • The relationship between the number of multiple transfer learning times and the accuracy of anomaly data identification is displayed. • Comparison experiments with different working conditions were set up to verify the effectiveness of multiple transfer learning. [ABSTRACT FROM AUTHOR]

The research object of this paper is to investigate the mechanical behavior and develop an analytical model of the prestressed circular-section rocking steel piers with external energy-dissipating devices under the horizontal cyclic load. Based on the method of monolithic beam analogy under monotonic loading, the concept of generalized rotation angle and intercept strain in the pre-decompression state was introduced. The geometrical equations for the pre- and post-decompression stages are deduced. The calculation formulas for internal forces of each component and the analytical calculation method for the entire process of the rocking steel pier under horizontal cyclic loading are established in detail. To reproduce the hysteresis curve of the test, some special test conditions, such as the retraction effect of prestressed tendons and increase of the compressed area due to the vertical plates, were considered in the analytical model. The results show that the analytical method based on generalized rotation angle and intercept strain can ensure an ideal transition of the hysteresis curve of the pier in pre- and post-decompression stages. Except for the pier with particularly severe local buckling and ovalization deformation, the calculated results obtained from the proposed analytical model agrees well with the test results for the rocking steel bridge piers. The effect of prestressed tendons and the P –Δ effect on the lateral load–displacement curve of rocking steel bridge biers was further analyzed through parametric study using the proposed model. The analytical calculation method presented in this paper provides a theoretical tool for seismic design of the rocking steel pier in engineering practice. This paper provides important guidance for the establishment of seismic design method of rocking steel piers. • to deduce the geometrical equations for the pre- and post-decompression stages of the rocking steel pier. • to establish the analytical calculation method for the entire process under horizontal cyclic loading. • to analyze the effect of prestressed tendons and the P –Δ effect on the lateral load–displacement curve. [ABSTRACT FROM AUTHOR]

This paper proposed a new method to strengthen and repair concrete columns, which combined active and passive confinement. The method involved the use of iron-based shape memory alloy (Fe-SMA) strips to quickly exert active confinement to these columns, followed by the use of fiber-reinforced polymer (FRP) and high-density polyethylene (HDPE) tubes as external passive confinement to improve the load-bearing capacity, durability, and ductility of concrete columns. Rubber concrete that performs high energy consumption and certain strength was used as the cladding layer to improve the impact resistance of the concrete column. This paper explored the effect of this method on the bearing capacity performance of concrete columns through axial compression tests and set three test variables, including different net-spacing of Fe-SMA, different FRP wrapping forms, and different FRP layers. The test outcomes showed that all three test variables obviously improved the load-bearing capacity and ductility of concrete columns, peculiarly when applying active confinement. Eventually, this paper proposed a theoretical model to predict the peak compressive strength of the specimen, which can provide a reference for designing this active-passive confinement strengthening method. • A new technique for strengthening concrete columns by using a combination of active and passive confinement was proposed. • The effect of different experimental variables on axial compressive behaviour of concrete columns were tested. • The variation laws of the axial compression performance of specimens were researched. • A theoretical model was given to predict the peak compressive strength of the specimen. [ABSTRACT FROM AUTHOR]

A comprehensive investigation into the mechanical properties of 50 and 70 mm thick high strength S690 steel plates and their butt-welded sections under tension was presented in this paper, and a total of 40 tensile tests were conducted. Firstly, a total of 18 proportional coupons with circular cross-sections were extracted at three different layers within the plate thicknesses. Tensile tests on all of these coupons were carried out to obtain their mechanical properties, and their variations across the plate thicknesses were also examined. Secondly, submerged arc welding was adopted to prepare butt-welded sections between these thick steel plates with various heat input energy. Micrographic examinations on typical heat-affected zones of the welded sections were also performed. Standard tensile tests on a total of 22 proportional coupons with rectangular cross-sections were carried out to obtain their mechanical properties, and the full range deformation characteristics of these coupons were assessed and compared, in particular, their tensile strengths and elongations at fracture. This paper presents important experimental evidence on the mechanical properties of these high strength steel plates of practical thicknesses in construction, and also of their butt-welded sections. It is demonstrated that there is little or even no reduction in their mechanical properties of these butt-welded sections, provided that the welding processes are properly controlled according to established welding practice. Hence, full strength butt-welded sections between these thick high strength S690 steel are readily achieved in practice, similar to those of the commonly adopted S355 steel. These important findings are contrary to general understanding as many researchers and engineers consider that the mechanical properties of these high strength S690 steel are reduced significantly after welding, irrespective of their plate thicknesses. [Display omitted] • Mechanical properties of thick high strength S690 QT steel plates were investigated. • There are significant variations in yield and tensile strengths across 70 mm thick plates. • Microstructures of heat-affected zones under various heat input energy were obtained. • No or little reductions in mechanical properties are found in these thick welded sections. • A proper control on welding procedures avoids reductions in their mechanical properties. [ABSTRACT FROM AUTHOR]

The modal-domain structural model updating and damage detection methods own the advantage that they perform the whole computation without the information of system input, when compared to the time-domain. The system input required in the time-domain methods is hardly measured in realistic field tests of civil engineering structures. However, the time-domain methods own the advantage that they carry out model updating based on raw measured dynamic responses but not the processed (and compressed) modal parameters. The modal-domain methods only uses the compressed modal parameters, and some useful system information may be lost in the compressing process. Thus, higher errors and uncertainties are induced in the model updating results from the modal-domain methods. To take advantages and avoid disadvantages from the traditional time-domain and modal-domain model updating methods, a novel time-domain MCMC-based Bayesian model updating method without the information of the system input is developed in this paper by incorporating a newly developed dynamic response reconstruction technique and extending the formulation of the posterior probability density function (PDF) and the corresponding bridge PDF in the MCMC sampling process. A new modal decomposition algorithm is proposed in this paper for accurate modal response decomposition even in case of dense or sparse modes, and filters are not required for higher computation accuracy. Experimental case studies on a two-story steel frame were conducted to illustrate the proposed methodology in both structural model updating and damage detection. According to the analysis results, it is concluded that the proposed methodology outperforms the modal-domain methods especially in the cases with small number of measured DOFs. • No excitation information is needed with the proposed time-domain MCMC-based Bayesian model updating method. • A novel modal decomposition method is proposed to obtain the modal responses without filters. • The uncertainties introduced by some uncontrolled factors are quantified with the proposed technique. [ABSTRACT FROM AUTHOR]

Italian and European transportation networks include a significant number of existing bridges, built since the early '60s, characterised by simply supported prestressed concrete (PC) girders with post-tensioned steel tendons. Corrosion of tendons, which may lead to significant loss of structural capacity, cannot be detected by simple visual inspections and requires advanced and expensive testing by bridge owners. Therefore, procedures aimed at risk-informed prioritisation of advanced inspections and possibly retrofit are needed. The paper presents a study on the fragility of existing PC girder bridges considering traffic loads, accounting for corrosion-induced effects. An automated framework is proposed, aiming at the efficient probabilistic structural assessment of the investigated bridge typology accounting for different critical corrosion scenarios and the influence of knowledge-based uncertainty related to geometric and mechanical properties. To simulate corrosion effects, prestressing steel tendon geometric and mechanical characteristics are modified through a specific algorithm able to estimate variations in flexural and shear bearing capacity of critical cross-sections. To simulate the traffic loads, a simplified analysis is performed by using code-based traffic load models. In the paper, the framework is tested with reference to a dataset of case-study superstructures. The obtained fragility curves are deeply discussed, highlighting the effects of the number of girders and span length on the corrosion-induced increase in fragility. Although the proposed methodology presents some simplifications, it could improve the current practices of risk prioritisation, by supporting transportation authorities in ensuring the safety of the existing bridge stock. • A methodology for fragility analysis of PC girder bridges under traffic loads is proposed. • The methodology accounts for knowledge-based uncertainty and corrosion of tendons. • The strategy for flexural response analysis of cross-section considering corrosion is validated. • The methodology is applied for six case-study superstructures. [ABSTRACT FROM AUTHOR]

Fiber-reinforced concrete is a typical unidirectional fiber-reinforced composite. For practicality and efficiency, fiber-reinforced concrete usually has the fiber and matrix modeled separately and then the fiber is embedded into the matrix. Therefore, this paper proposes a novel method to realize the topology and fiber orientation optimization for fiber-reinforced concrete structures. The optimization formulation considers two types of discrete variables, i.e., topology and fiber orientation, which are optimized by using the solid isotropic material with penalization method and bi-value coding parameterization method, respectively. To reduce the computational complexity, the topology and fiber orientation are independently updated at each iteration during the optimization process. Numerical examples verify the validity of the proposed method, which provides new ideas for the design of fiber-reinforced concrete structures. • This paper proposes a topology optimization method for fiber-reinforced concrete structures using membrane-embedded model. [ABSTRACT FROM AUTHOR]

Friction is an important source of energy dissipation in structural damping. The effect of friction on the damping ratio, however, has not been fully investigated. This paper presents an experimental study of the nonlinear damping ratio induced by friction at bolted joints of a bridge model in the laboratory. The decay responses of the bridge were tested under various bolt configurations and pre-torques. The nonlinear characteristics of the damping ratio were analyzed, and the experimental results were interpreted through numerical simulations. The relationship between damping ratio and amplitude of the Iwan model was derived. The results show that friction induces a nonlinear damping ratio. The damping ratio exhibits two opposite nonlinear characteristics under the influence of bolt joints. The damping ratio may either decrease with decreasing amplitude or may increase, and both of these nonlinear patterns can be elucidated by the Iwan model. Numerical simulations successfully replicate these two nonlinear damping ratios. A case study of an actual steel truss bridge is used to discuss the possible effects of bolt joints on the damping ratio. The results of this paper reveal the nonlinear damping patterns induced by bolt joints and provide an optional model for such structures. • There are two opposite nonlinear patterns of bridge damping ratio under the influence of bolt joints. • The configuration and pre-torque of bolts induce the damping ratio to vary in the range of approximately 0.25% to 1.20%. • High pre-torque may result in lower damping ratio. • The Iwan model can explain the two nonlinear patterns of the damping ratio. [ABSTRACT FROM AUTHOR]

The realistic consideration of reusability of a fire effected RC structure or structural member relies on the accurate estimation of post-fire structural capacity. Bond between steel and concrete play a vital part in the structural analysis of RC. This paper presents a study on bond behaviour of RC structural members exposed to fire employing ISO-834 fire scenario and using beam-end test specimens to take into account the realistic boundary conditions of a flexural member. The study is a continuation of the previous work done by authors. The focus of this paper is to understand the residual bond behaviour considering various concrete covers and the presence of transverse reinforcement for various fire durations. Two different fire exposure scenarios are considered, namely one-sided heating, where only the surface with the minimum concrete cover is exposed to fire and three-sided heating, where two side surfaces along with the surface with minimum cover are exposed to fire. The beam-end specimens were exposed to fire for a desired fire exposure duration, followed by a natural cooling to room temperature. An unconfined pull-out test was performed thereafter to obtain residual behaviour. The results show that although concrete cover and presence of transverse reinforcement do have an influence on the absolute values of the residual bond splitting strength after fire, the relative values of bond degradation due to fire are not very strongly influenced by these parameters. • Post-fire bond behavior of reinforcement in concrete is experimentally investigated considering real fire scenarios. • Different concrete cover and transverse reinforcement in the bonded zone are considered. • Modified beam-end specimen is used in the experimental investigations. • Specimens are subjected to ISO834 fire scenarios for different fire exposure durations with one- or three- sided exposure. • Severe reduction in post-fire bond capacity and stiffness is observed for all the investigated cases. [ABSTRACT FROM AUTHOR]

Nonlinear energy sink (NES) is a type of vibration absorbers that does not have linear stiffness. Through establishing strongly nonlinear coupling between a primary system and a NES, the targeted energy transfer can be achieved from the primary system to the NES, thereby realizing vibration absorption in a wide frequency range. A significant amount of research work has been conducted on developing the NES for unidirectional vibration energy transfer over the last decade. More research is expected to develop further NESs to address various engineering vibration problems. Meanwhile, the question of whether NES can be practically applied to engineering is always being asked. The main objective of this paper is to review the research progress on dynamic design of NESs to promote the application of NESs to reduce engineering structure vibration. To do so, this paper first summarizes the characteristics of NESs, including vibration absorption mechanism, the threshold of targeted energy transfer, and strong nonlinearity characteristics. Then, dynamic designs of the NESs proposed in the literation are reviewed in terms of nonlinear stiffness design, mass design and damping design. Special attention is placed on the nonlinear stiffness design for NESs, including design principle, multi-stability design, track design, and magnetic design. The gaps between these design approaches and applications are explained. NES cells and their distributed vibration control strategy are also introduced. The research progress on the NES optimization design is also briefly discussed. Following the extensive review on NES dynamic design research, future promising research topics are recommended with an attempt to advancing the engineering application of NES. It is expected that this paper would help readers to understand the progress of NES dynamic design research and the future NES development for more practical applications. • The research progress on dynamic design of the nonlinear energy sink is reviewed. • The NES cell and its distributed vibration control strategy are also introduced. • Future promising topics are recommended to advance the application of NES. [ABSTRACT FROM AUTHOR]

Rocking of a non-symmetric block on a compliant horizontally-moving base is explored for the first time in this paper through a combination of analytical, numerical and experimental approaches. A compliant base model is proposed, which is shown to have good overall accuracy, in particular predicting when rocking will be initiated. The proposed model predicts a significantly lower rocking threshold, which is much more sensitive to the eccentricity of the centre of mass, in comparison with the threshold determined assuming the base is rigid. The proposed model predicts that a highly non-symmetrical block, with its centre of mass outside the middle third of its base, will have uplifted even when it is at rest and no horizontal excitation is applied. The proposed model also predicts lower overturning thresholds, which is because the static overturning angles reduce when the compliance of the base is accounted for. The proposed compliant base model provides an accurate tool suitable for the design of base isolation systems for the seismic protection of freestanding museum artefacts or mechanical equipment, as evidenced by the extensive numerical and experimental test results presented in this paper. • Dynamic response of non-symmetric rigid blocks standing on a horizontally-moving compliant base. • Combination of analytical, numerical and experimental studies. • The compliant base model can better predict when rocking will be initiated. • The rocking thresholds are significantly lower than those determined assuming the base as rigid. • The rocking thresholds are sensitive to the eccentricity of the centre of mass. [ABSTRACT FROM AUTHOR]

This paper proposes a novel structural analysis approach, the neural networks-based spring element (NNSE) method, to synergize machine learning (ML) techniques with the line finite element method (LFEM) for the second-order analysis method of pile-supported structures. Traditional LFEM, widely used in upper structure design, showcases limitations in efficiently modeling complex Soil-Structure Interaction (SSI) along piles since it requires dense element mesh for accuracy. Conversely, ML offers a mesh-free alternative for analyzing single piles but struggles in simulating pile-supported structures as the training sample collection for large-scale problems might be unbearable. This paper addresses these challenges by proposing a new analysis framework to utilize the neural network (NN) model, which only describes structural responses of single piles, for the simulation of entire pile-supported structures. In the proposed method, the NN model is not directly used for structural analysis but employed to formulate a new spring element named the NNSE to model single piles in pile-supported structures. This NNSE can be seamlessly implemented within the existing LFEM framework to analyze pile-supported structures, eliminating the dense mesh requirement for single piles and thereby significantly improving the computational efficiency. Extensive examples are provided to verify the effectiveness of the proposed method, indicating its potential in promoting the second-order analysis method to the design of pile-supported structures. • A novel NNSE method is proposed for analyzing pile-supported structures. • NNSE efficiently captures nonlinear SSI using one element per pile. • This method surpasses existing solutions in both efficiency and accuracy. • NNSE provides a novel integration of FEM and ML for structural analysis. [ABSTRACT FROM AUTHOR]

Friction Pendulum Bearing (FPB) with shearing keys will exhibit friction-coupling effect and collision phenomenon subjected to horizontal orthogonal ground motions. This paper establishes a numerical analysis model of FPB with four shear keys and viscous damping, considering the impact of the friction coupling effect and collision between the FPB and the shear keys on its displacement response. The influence of parameters of FPB on seismic displacement response with considering collision effect under horizontal orthogonal ground motions was studied. The results suggest that adjustments in damping and equivalent stiffness exclusively impact the amplitude of the displacement response, maintaining the response waveform. Conversely, variations in friction significantly alter the response waveform, as friction induces changes in the natural frequency of FPB. A heightened collision impact is noted with reduced spring stiffness. The displacement response is particularly amplified when the collision occurs at the vicinity of peak displacement in the time-history response of FPB. When the restoring stiffness and Peak Ground Acceleration (PGA) are low, the friction coupling effect significantly reduces the amplification of displacement response caused by collision effects. Viscous damping can considerably reduce the impact of collisions on the peak displacement of FPB and prevent the collision effects from noticeably amplifying or diminishing the peak displacement of FPB. • This paper proposes a numerical model of FPB considering shear key collisions. • Theoretical derivations and categorizations of collision and shearing scenarios involving shear keys are presented. • This model enables a decoupled analysis of the displacement response of FPB with shear keys under orthogonal horizontal seismic motions. [ABSTRACT FROM AUTHOR]

Built-up radially battened columns (RBCs), comprising several identical circular steel tubes interconnected by multiple radial-shaped battens, represent an innovative column design that combines aesthetic appeal with exceptional load-bearing capacity. This makes them well-suited for architectural applications in large public buildings such as stations and airports. The axial compressive strength design methods for the built-up RBC have been extensively explored in the authors' prior studies. However, in real-world engineering applications, built-up RBCs may experience simultaneous axial compression and varying directional bending moments, particularly when considering potential eccentric compression or wind and earthquake loads in public buildings. Currently, strength design methods for this loading condition are still lacking. To address this deficiency, this paper primarily delves into the failure mechanism and strength design methods for built-up RBCs experiencing combined axial compression and arbitrary directional bending moments. Initially, the sectional strength of the built-up RBC is investigated by using a shell finite element model (FEM) for the built-up RBC. It is revealed that the compression-bending sectional strength of the built-up RBC exhibits significant differences with varying bending directions and tube numbers. Moreover, in some bending directions, the M - N sectional strength curve of the built-up RBC exhibits convexity. By integrating theoretically derived equations grounded in the principles of materials mechanics with FEM numerical calculations, concise and practical design equations are proposed for accurately predicting the sectional strength of the built-up RBC under combined axial compression and arbitrary directional bending moments. Subsequently, The buckling strength of the built-up RBC is studied using the FEM, considering initial geometrical imperfections consistent with first-order flexural buckling and accounting for geometric nonlinearity. It is noted that the bending direction of the built-up RBC may deviate during loading. Besides, the M - N buckling strength curve of the built-up RBC is not as convex as its M - N sectional strength curve. Based on calculations from numerous examples, practical design equations for predicting the buckling strength for the built-up RBC under axial compression and any directional bending moments are introduced. The key findings of this paper contribute to the compression-bending strength design of RBCs, enriching RBC design theory and promoting the widespread application of built-up RBCs in actual engineering projects. [Display omitted] • The M - N strength of RBCs varies with different bending directions and tube numbers. • The M - N sectional strength curve of the built-up RBC is convex. • The built-up RBC's bending direction may deviate during loading. • The M - N buckling strength curve of RBCs is less convex compared to its M - N sectional strength. • The M - N strength of RBCs can be predicted by a quadratic function. [ABSTRACT FROM AUTHOR]

This paper presented an innovative uplift-restraining friction pendulum bearing (UR-FPB) to address the limitations of traditional FPBs, which are unable to withstand vertical tensile loads. The UR-FPB is composed of a friction set acting as the horizontal sliding module and an anti-uplift set acting as the vertical uplift-restraining module. Based on this configuration, the study derived the theoretical force-displacement relationships of the UR-FPB, established three solid finite element models in Abaqus, and proposed a hybrid modeling method based on OpenSees. Then the practical effectiveness of this bearing and the credibility of the theoretical analysis models and hybrid numerical models were validated. The theoretical and numerical results demonstrate that the frictional behavior of the UR-FPB in horizontal sliding is characterized by multi-stage hysteresis relationships. The numerical results on the sliding characteristics and the corresponding hysteresis relationships are highly consistent with the theoretical results. The UR-FPB has a large horizontal sliding capacity similar to that of traditional FPBs, while the design of the anti-uplift configuration does not reduce or limit this sliding capacity. Significantly, the study investigated the uplift-restraining behavior of the UR-FPB and its effect on the horizontal responses. The analysis results suggest that the UR-FPB has a good uplift-prevention capacity and this paper recommends that the design value of tensile capacity should not exceed the yield force in tension. Therefore, this novel uplift-restraining friction bearing has an expected effectiveness, which can simultaneously resist vertical tensile loads and function as a horizontal seismic isolator. The proposed hybrid modeling method may provide a useful reference to model the behavior of the UR-FPB in software used for response-history analysis. • The study develops an innovative uplift‐restraining friction pendulum bearing (UR-FPB). • Three solid finite element models of the UR-FPB are established. • A hybrid modeling method for the UR-FPB is proposed based on OpenSees. • Theoretical analysis models and hybrid numerical models are validated. • This bearing exhibits excellent three-dimensional mechanical behaviors. [ABSTRACT FROM AUTHOR]

Shear wall structures are widely used in high-rise buildings. However, the design process of shear wall structures suffers from inefficiencies. This paper introduces StructDiffusion, an end-to-end intelligent system for shear wall layout generation and analysis. The proposed approach tackles the layout design task by employing a novel diffusion model architecture to generate conditional images. Key components of the proposed method include pretrained diffusion models, ControlNet for conditional control, and LoRA for efficient adaptation. Notably, the method allows for architectural plan images and basic textual design conditions as inputs, enabling manipulation of the generated layouts by adjusting attributes such as building height and seismic intensity. To evaluate the quality of the model's design swiftly, this paper presents a comprehensive evaluation framework that incorporates perceptual and structural validity metrics. Through experimental analyses, this paper demonstrates the effectiveness of the proposed model in generating layouts, surpassing the capabilities of GAN-based methods. Furthermore, our study investigates model-specific parameter configuration, text-guided capabilities, code compliance, and computational efficiency. StructDiffusion significantly enhances the automation and intelligence of structural engineering workflows. The framework effectively addresses challenges associated with instability, data scarcity, and limitations in assessment. This pioneering application of diffusion models opens up promising avenues for advancing data-driven structural design. • Pioneering stable diffusion models to replicate human structural design expertise. • Generating tailored layouts by aligning text-based design conditions and image-based architectural layouts. • Integrating LoRA, a low-rank decomposition technique, to optimize training efficiency with limited data. • Proposing an evaluation metric combining image quality and structural design considerations for robust model assessment. [ABSTRACT FROM AUTHOR]

Rammed earth is a traditional construction technique that has recently gained attention because of its benefits from an ecological perspective. The conservation of the existing valuable cultural heritage sites and the quality control of new constructions built with this material require the development and application of practical inspection techniques. This paper explores the application of sonic tests and sonic tomography as practical tools for monitoring the state of conservation of existing structures and the identification of heterogeneities or damaged areas. Two groups of 6 rammed earth specimens were manufactured and tested. The manufacturing process of each group allowed the application of compression loads and the identification of the Sonic Wave Propagation Velocities along directions parallel and perpendicular to the compaction forces during manufacturing. The SWPV were identified for the different paths between 9 measuring points located at two opposite sides of the specimens, leading to up to 6 different planes for each specimen. The SWPV are identified by identifying the Time-of-Flight of the elastic wave between each pair of excitation and receiver points. A discretized coloured map of the SWPV distribution for each plane defined by the measurement points array is obtained by the application of an algorithm already developed by the authors to obtain tomographic images for other materials and applications. The SWPV are identified after 2 different increasing values of a uniform compressive load is applied to each specimen. The results show that the analysis of the SWPV and tomographic images is sensitive to heterogeneities, such as compaction gradients from the manufacturing process, and also to the accumulated damage in the solid. The paper demonstrates that the proposed technique can be potentially used for a qualitative inspection of the state of conservation of specific rammed earth constructions. • Sonic wave propagation velocities (SWPV) are identified for different directions. • SWPV maps are obtained following a transmission tomography approach. • Estimated values of SWPV at 3 horizontal and 3 vertical planes are analysed. • SWPV are sensitive to progressive damage and compaction gradients. • No material anisotropy is found according to SWPV values. [ABSTRACT FROM AUTHOR]

The low-temperature brittle failure of materials could aggravate the brittle characteristics of shear failure of RC beams, which urgently needs scientific research. This paper aims to investigate the shear behavior and corresponding size effect of reinforced concrete (RC) beams at low temperature by numerical analysis. Firstly, a two-stage thermo-mechanical coupled mesoscale simulation method was developed, which considered the meso-structure characteristics of concrete as well as the ice-strengthening effect. Based on the mesoscale simulation method validated through a series of tests, the progressive shear failure process of RC beams at room and low temperatures was captured. The influences of temperature (T = 20, −30, −60 and −90 °C), structural size (cross-sectional height H = 300, 600, and 1200 mm) and shear span-to-depth ratio (a / h 0 = 1.0, 1.6, and 2.3) on key indexes of shear behavior were quantitatively analysed. The results indicate that compared to that at room temperature, the shear failure process of RC beams at low temperature is more rapid, exhibiting more obvious brittle characteristic. When the temperature drops from 20 °C to −90 °C, the nominal shear strength of RC beams is enhanced with a maximum increase of 57.0 % (for H = 300 mm) while the mid-span displacement is reduced with a maximum decrease of 46.8 % (for H = 300 mm). Compared to that at room temperature, the size effect on nominal shear strength of RC beams at low temperature is enhanced, with a maximum increase of 20.4 %. Finally, considering the influences of low temperature and shear span-to-depth ratio on the nominal shear strength, an improved size effect analytical model for was established, which can predict the shear capacity of different sized RC beams at low temperatures. This paper can provide a reference for the safe application of reinforced concrete structures in low temperature environments, and lay a foundation for the formulation of reinforced concrete structure design specifications at low temperature. • The shear behavior of RC beams at low temperature was modeled by 3D mesoscale model. • The meso-structure characteristics and ice-strengthening effect was considered in model. • The influences of low temperature and size characteristics of RC beams were investigated. • An improved size effect theoretical formula of RC beams at low temperature was established. [ABSTRACT FROM AUTHOR]

This paper aims to comprehensively discuss the latest research developments in the field of underwater structural defect detection and health assessment. The underwater robots can carry the non-contact detection equipment such as optical and acoustic devices, as well as the contact-based detection equipment like ultrasonic instruments, making them important platforms for underwater structural detection methods/tools. This paper first introduces the current progress of underwater robots in the underwater structural detection, elucidating the research progress in autonomous and intelligent path planning algorithms for underwater robots. It discusses the advantages and disadvantages of non-contact defect detection methods for underwater structures based on optics and acoustics, as well as their adaptability to different detection objects and requirements. The research also investigates contact-based underwater defect detection methods and points out the limitations of such methods. It summarizes methods for the three-dimensional (3D) reconstruction using underwater images or video data, laying the foundation for precise localization and quantitative analysis of underwater structural defects. It discusses the mainstream methods for assessing the health of underwater structures, highlighting the shortcomings of existing methods. Finally, it identifies the challenges and future trends facing current underwater structural defect detection methods, providing direction for future research in the intelligent underwater structural detection and assessment. • This paper investigates the research status in underwater structure detection, and proposes future development directions. • This paper provides a comprehensive review of non-contact and contact based underwater structure detection methods. • This paper provides a comprehensive summary of the assessment methods and research directions for underwater structures. [ABSTRACT FROM AUTHOR]

Full-depth precast deck panels hold the potential to enhance constructability and productivity, and reduce the costs associated with highway bridges. This paper investigates the influence of discontinuous shear connections between girders and panels on the flexural behaviour of composite beams. Experimental findings from precast composite beams and direct shear tests are presented, including L-shape push-off tests and double shear tests to determine resistance at rough concrete-to-concrete plain interfaces and shear pocket connections. Composite beams with a full-depth precast slab connected through a shear pocket with shear keys into the upper face of a precast beam exhibit equivalent flexural resistance to monolithic beams when shear pocket spacing remains below the effective depth of the composite beam. However, composite beams with shear pockets featuring plain interfaces show a reduction in flexural resistance of up to 30% compared to monolithic beams. Moreover, composite beams with shear keys demonstrate interface shear stiffness up to four times greater than those with plain interfaces, indicating full interaction. The paper proposes simplified equations to estimate flexural resistance for composite beams with full-depth precast slabs joined by shear pockets, showing a coefficient of variation of only 12% compared to experimental results, offering a reliable method for predicting flexural resistance in composite beams with discontinuous connections. • An empirical equation derived from direct shear tests is proposed for rough plane surfaces. • Two types and spacing of shear pockets in composite beam were analysed. • Composite beams with shear keys exhibit high interface shear stiffness. • Under cyclic loading, composite beams with shear keys demonstrate minimal stiffness loss. • Simplified equations for estimating the flexural resistance of composite beams are proposed. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic characteristics and Finite element model updating of two confined masonry buildings in Messina, constructed in the aftermath of the devastating 1908 earthquake. The study addresses the need for advanced research in this field to enhance the understanding of the dynamic behaviour of confined masonry structures. The authors identified the modal parameters of the buildings from ambient vibration tests. Finite element models have been developed and fine-tuned in a second step to optimize the agreement between the simulated and observed modal parameters. The optimized parameters are then compared with the outcomes of nondestructive tests on masonry and reinforced concrete. This research addresses the modelling issues when dealing with confined masonry structures, offering guidance to engineers to select the modelling parameters. The paper emphasizes the substantial stiffening effect introduced by confined masonry, as evidenced by the optimized Young's modulus of masonry, which is almost two and a half times higher than values obtained from flat jack tests. To accurately represent the interaction between reinforced concrete ties and masonry panels within equivalent frame models, it becomes crucial to adequately overstate the masonry stiffness to capture the mutual coupling between structural components. • Dynamic characterization of confined masonry buildings. • Intelligent Automated Operational Modal Analysis approach. • Predictive capabilities of simplified FE modelling for confined masonry. • Genetic optimization algorithm to fine-tune modelling parameters. • Insight to select model parameters for confined masonry. [ABSTRACT FROM AUTHOR]

This paper investigates comprehensively the resonance and cancellation conditions for the free vibration of elastically-supported (ES) beams subjected to successive moving loads. Focus is placed on application of the cancellation condition to minimize bridge vibrations, considering particularly the effect of elastic supports. In terms of the modal amplitude R of free vibration of the ES beam, both resonance and cancellation conditions are identified. This paper is featured by the fact that the cancellations are classified into two types as the external (load-related) and internal (structure-related) ones. Through the (internal) cancellation function, the criterion for selecting the optimal support stiffness ratio (SSR) is derived for the first time for suppressing the resonance of short to medium-span railway bridges. It depends solely on the bridge/vehicle length ratio L / d , and can be utilized to achieve near-perfect cancellation. The theoretical findings are validated by the finite element method (FEM) for various parameters. The results reveal that for beams with lengths in the ranges of (0.5 d , d ] and (1.5 d , 2 d ], an SSR closer to the lower bound of the acceptable range should be selected to achieve the best effect. And for beams with lengths in the range of (d , 1.5 d ], the SSR should be selected as close to the optimal value as possible. Besides, it was found that damping in the beam and supports contributes to further suppression of vibration for bridges designed with optimal SSR. • Derive new resonance and cancellation conditions for elastically supported beams. • Classify cancellations as external (load-related) and internal (structure-related) ones. • Optimal support stiffness ratio (SSR) for near-perfect cancellation of resonance. • Optimal SSR relies solely on the bridge/vehicle length ratio and is easy to use. • Verify the effectiveness of SSR criterion for various factors. [ABSTRACT FROM AUTHOR]

Knowledge of displacement responses of high-rise buildings under harsh wind excitations is essential for their wind-resistant structural design. This paper develops a machine learning model named long short-term memory (LSTM) to estimate the displacements of a 420-m-high building during Super Typhoon Mangkhut based on available field measurements. The developed model is trained and validated using the field measurements on the building during typhoon events, and the performance of the model is assessed against several evaluation criteria. Then, the trained LSTM model is employed to estimate the displacements of the skyscraper during Mangkhut. The accuracy of the estimated displacements is validated in time and frequency domains. Moreover, the background and resonant components of the estimated displacements during the extreme windstorm are analyzed. This paper aims to provide valuable reference for the wind-resistant design of high-rise buildings in tropical cyclone-prone regions. • Develop an LSTM model to estimate displacement responses of a 420-m-high building During Super Typhoon Mangkhut. • Examine effectiveness and accuracy of the developed LSTM model based on field measurements on the building during typhoons. • Estimate displacements of the skyscraper during Super Typhoon Mangkhut based on the LSTM model and available measurements. • Explore across-wind and along-wind responses, along with resonant and background components of the estimated displacements. [ABSTRACT FROM AUTHOR]

Currently, progressive collapse studies are mostly conducted based on an event-independent assumption. With studies employing an event-dependent premise mainly concerning explosion or fire events, the aftermath of impact loading is seldom reported. Meanwhile, interactions between reinforced concrete (RC) members and superstructures under impact loading need further evaluation. In this paper, finite element models of RC structures subjected to impact loading and progressive collapse are established and validated utilizing LS-DYNA. A valuing methodology of erosion parameters for the continuous surface cap model (CSCM) considering element size is proposed in this process. The influence of impact column removal (ICR) on the progressive collapse performance of RC frame structures is studied at sub-assemblage and structure levels. The parametric study indicates that the ICR process can be described by an impact loading stage and a gravity load stage. It is also found that structures experiencing ICR are exposed to a higher risk of progressive collapse, with the downward force exerted by the impacted columns being a significant contributing factor. Dynamic analyses demonstrate that the acceleration of the column removal point (CRP) can be used to validate and quantify the downward force. The hybrid force-displacement boundary conditions of frame columns give rise to the development of downward force. Recommendations for resisting progressive collapse considering ICR are proposed based on the analytical results of the paper. • A new threat-dependent perspective to progressive collapse research is elucidated, focusing on impact column removal (ICR). • Interactions between impacted columns and superstructures are illuminated, emphasising the influence of downward force. • The boundary conditions of frame columns suggest a new research roadmap for impact response of structural members. • The study on the effects of ICR indicates higher progressive collapse risk due to downward forces and initial damage. • Recommendations of resisting progressive collapse considering ICR are proposed. [ABSTRACT FROM AUTHOR]

In recent studies, deep learning methodologies have shown significant promise in crack detection. However, their practical implementation faces challenges due to the intricate diversity of structural surfaces and the inherent narrowness of cracks. To mitigate these problems, this paper introduces SegFormer, an efficient semantic segmentation model with hierarchical Transformer, for crack detection on concrete and asphalt surfaces in multiple scenarios. The combination of Cross-Entropy (CE) and Dice loss functions is employed to enhance the detection of fine cracks. Additionally, the paper presents an evaluation framework and discusses metrics for assessing crack segmentation results to provide a more precise and comprehensive analysis of model performance. Experimental results indicate that SegFormer outperforms Convolutional Neural Networks (CNNs) such as FCN, U-Net, and DeepLabV3 utilizing different backbones. Notably, the integration of multiple loss functions contributes to a more stable training process, expedites convergence, and yields enhanced results compared to models utilizing individual loss functions. • SegFormer is introduced for fine crack detection in various scenarios. • The combination of CE and Dice loss functions enhances crack detection. • A comprehensive model evaluation framework is presented. • Metrics for fine crack segmentation assessment are discussed. [ABSTRACT FROM AUTHOR]

Bonding strips is widely used for the strengthening of structures. This paper addresses the challenge of stress concentration in the strip-strengthened beams, where interfacial stresses at the end of the strip are usually large enough to causes premature brittle debonding failure. Lengthening bonded strips and thickening adhesive layer are effective solutions to decrease the stresses but sometimes difficult to implement. For example, obstacles under the beam may stop the strip from being lengthened with bonding. This paper proposes a feasible solution for this case that is extending the strip without bonding and then fixing it with additional anchors at the end. Analytical expressions are derived for interfacial stresses in strip-bonded beams with the end-anchored unbonded segment (EAUS). The deformation coordination relationship between EAUS and the beam is considered. The anchor bolts are analogous to elastic foundation beams to obtain their shear stiffness which will greatly influence the tension at the strip end. The theoretical results are then verified by finite element simulations. Moreover, parameter studies are performed to explore the effects of various strengthening configurations such as the length of the bonded and unbonded segments on interfacial stresses. The investigations show that the presence of the EAUS could substantially alleviate the concentration of interfacial stresses. The findings of this study provide a new approach on how to control stress concentration in the strip-strengthened beams. • Developed the analytical solution for the interfacial stresses in end-anchored unbonded segment. • Validated the analytical solutions via finite element simulations. • The interfacial stresses in strip-bonded beams were mitigated by appending end-anchored unbonded segment. • The anchor bolt was compared to an elastic foundation beam. [ABSTRACT FROM AUTHOR]

To improve the bearing and energy dissipation of the precast concrete (PC) shear wall, this paper proposes an angle-section and C-section steel embedded PC wall with external low-yield-point steel (LYP) energy dissipators (EDs). The wall is an energy-dissipation and load-bearing bi-functional system during the seismic and a design method for this wall is also presented in this paper. Two full-size precast shear walls with and without external EDs (PWE and PW, respectively), were designed based on the proposed method and tested under an axial compression ratio of 0.2. Seismic performance in terms of failure modes, hysteretic behavior, strength envelope, stiffness degradation, energy dissipation, and steel strains was investigated and discussed. According to the crack pattern observed during the test, the PW and PWE were found to be in flexural–shear failure mode, and the PWE exhibited better seismic behavior compared with the PW, The yield and peak loads of the PWE compared with those of the PW increased by 23% and 22%, respectively. The equivalent viscous damping ratios of the two walls exceeded 0.05. When the walls were under a large displacement, the equivalent viscous damping coefficient of the PWE was higher than that of the PW. Moreover, the cumulative energy dissipation of the PWE exceeded that of the PW by 15–55%. The strain in the embedded steel in the PWE was less than that in the PW, indicating that the PW suffered more nonlinear strain and concrete damage. Test results indicate that the supplementation of replaceable external EDs can improve lateral bearing and energy dissipation capacities as well as decrease the nonlinear strain to reduce the extent of damage to wall panels. Additionally, the analytical model of PWE based on the fiber model was proposed and the rationality of the model was verified by comparison of the numerical and tested results. Furthermore, a parameter analysis was conducted to investigate the seismic behavior of PWE considering various structural properties. • A precast concrete wall with angle and C-shaped steel embedded and low-yield-point steel energy dissipators is proposed. • The design method for PWE is also presented in this study and verified by test results. • Two full-scale wall panels are tested under lateral cyclic loading. • The use of supplemental external devices improve the bearing and energy dissipation capacities of the precast shear wall. [ABSTRACT FROM AUTHOR]

In this paper, seismic analyses of single-layer dome structures are carried out, with a particular emphasis on the incorporation of randomness in both geometrical imperfections and ground motions. First, the paper introduces models for random geometrical imperfections and stochastic ground motions, employing the Stochastic Imperfection Mode Superposition Method (SIMSM) for imperfections and utilizing the Spectral Representation Method (SRM) for ground motions. These models are designed to comprehensively account for the inherent uncertainties in real-world structural behavior. Subsequently, the Probability Density Evolution Method (PDEM) is applied to investigate the probabilistic response and seismic reliability of dome structures, which allows for a detailed examination of key performance indicators, such as displacement, plastic ratio, and strength damage, under the influence of random factors. Both deterministic and stochastic analyses are conducted to gain insights into the impact of randomness in geometrical imperfections and ground motions. The computational results unveil a crucial finding: an unfavorable distribution of imperfections can significantly compromise the dynamic performance and safety of single-layer dome structures. Furthermore, the paper delves into parametric analyses, with a specific focus on imperfection amplitude, the rise-span ratio and roof load as pivotal parameters. These analyses provide valuable insights into the sensitivity of the structural response to variations in these critical design factors. • Both the randomness in ground motions and geometrical imperfections is considered. • The randomness in ground motions has more significant impact. • Larger rise-span ratio can be detrimental to the dynamic reliability. • Excessive roof loads negatively impact the dynamic reliability of dome structures. [ABSTRACT FROM AUTHOR]

In this paper, a novel equilibrium-based form-finding approach for a mega-latticed structure is presented based on vector-based 3D graphic statics and the Combinatorial Equilibrium Modelling (CEM). This approach can be effectively applied to the conceptual design phase of the structures with various design objectives under conservative loads. It allows us to adjust the design parameters in real time during the design phase and to obtain the resultant forms immediately. Based on a certain selection strategy, the forms have a better state of internal membrane forces compared to the original spherical structure. An ANSYS Parameter Design Language (APDL)-based automatic geometric modelling method for mega-latticed structures with various surface forms is developed. The proposed method solves the problem that the existing modelling methods are only available for spherical structures. It is highly applicable for modelling mega-latticed structures with spherical, cylindrical, and other heterogeneous surfaces. Furthermore, a complete design workflow that combines the proposed form-finding approach (for conceptual design), the automatic geometric modelling method (for transformation), and the finite element method (for deepening design and analysis), is discussed. This paper provides a reference for the design of mega-latticed structures and similar truss-based spatial structures. • A new equilibrium-based form-finding approach for a mega-latticed structure is proposed. • An automatic geometric modelling method for mega-latticed structures is improved. • A design workflow combining the form-finding approach and finite element method is discussed. • A case study is performed to verify the validity of the whole structural design process. [ABSTRACT FROM AUTHOR]

The paper presents an experimental program on a structural system, consisting of three long-span portal frames. The primary structural members, including columns and rafters, were constructed using cold-rolled aluminium back-to-back built-up channel sections. The system configuration featured two bays of single-span cold-rolled aluminium portal frames connected in parallel by a series of purlins spanning between the rafters to create a free-standing structure. A total of three full-scale tests (Frame Tests 1,2 & 3) were conducted with two loading scenarios. Frame Tests 1&2, which were identical to ensure accuracy, were subjected to vertical loads only, while Frame Test 3 underwent testing with combined horizontal and vertical loads. In all the tests, the columns were unbraced. The main objectives of this paper are, first, to describe the test setups and observe the structural behaviours of the portal frame systems. Consequently, the ultimate capacities were determined, and the predominant failure modes of the portal systems were identified as flexural-torsional buckling of the unbraced columns. The paper also provides information on the mechanical properties of the aluminium alloy 5052-H36 materials used to fabricate the structural members and frame components, obtained from compressive and tensile coupon tests. Further, the elastic buckling loads of the columns in the frame systems are reported in this paper, as determined from the measured load-deformation curves. While this paper primarily delves into the behaviour of the cold-rolled aluminium portal frames with a focus on flexural torsional buckling failures of unbraced columns, the authors have also conducted a separate study on the same system. In that separate study, the portal frames with the columns predominantly restrained against flexural-torsional buckling were investigated to enhance the ultimate capacities of the portal frame systems. • Three full-scale portal frames fabricated from cold-rolled aluminium back-to-back built-up channel sections are tested. • Aluminium alloy 5052-H36 materials are used to fabricate the cold-rolled aluminium structural members and frame components. • Portal frames are tested under two loading cases, including vertical loads only and combined horizontal and vertical loads. • Observed failure mode of the portal frames is flexural-torsional buckling of the unbraced columns. • Elastic critical loads of the columns of the portal frame tests are determined using the measured load-deformation curves. [ABSTRACT FROM AUTHOR]

The challenges of the substantial self-weight in prefabricated bridge deck slabs, the presence of numerous scattered steel beam components, and the low durability of bridge deck slabs have long been difficult issues to address in the context of traditional prefabricated steel-normal concrete (NC) composite girder bridges with flat steel webs. This paper proposes a solution through the optimization of structural forms and material properties by introducing a novel structural configuration as prefabricated steel-laminated concrete (LC) composite girder bridges with corrugated steel webs. The flat steel webs were substituted with corrugated steel webs, and the LC bridge deck slab was composed of a NC layer and an ultra-high performance concrete (UHPC) layer. This paper conducted three groups of experimental tests to comparatively analyze the effects of web forms and bridge deck materials on the flexural performance of composite beams. The results indicate that, under the conditions of consistent beam height and steel usage, composite beams with corrugated steel webs have fewer steel components, better stability, and smaller difference in bearing capacity compared to composite beams with flat steel webs. Compared with NC bridge deck slab, laminated bridge deck slab can increase the stiffness and bearing capacity of composite beam by about 13%, and the thickness of the bridge deck slab can be reduced by 20%. Furthermore, this paper presents a shear connection degree calculation method suitable for composite beams with corrugated steel webs, which effectively reduces the number of connectors. • I-beams with corrugated steel webs have similar load-carrying capacity and better stability to flat web beams. • The flexural contribution of the corrugated steel web cannot be ignored. • UHPC-NC laminated bridge deck slab increases the flexural capacity of composite beams by at least 13%. • The shear connection degree of steel-laminated concrete composite beams should be at least 0.85. [ABSTRACT FROM AUTHOR]

Measuring a large grid structure is always based on the traditional total station, which requires a significant workforce. Aiming at the ring structure's characteristics, this paper fully uses multi-sensor advantages and proposes an automatic identification method of grid structure nodes. This method combines deep learning, panoramic camera, and laser scanning and improves the existing method of measuring the lifting process of the grid structure. The main contributions of this paper are as follows: (1) Aiming at the issue with existing measurement methods relying on complex multi-camera systems, a method based on a single panoramic camera and deep learning is proposed to quickly complete the full-field image target points detection, which provides a basis for the identification of target areas in the point clouds; (2) For the challenge posed by a large number of point clouds models and complex processing, a method of automatically capturing point clouds nodes by integrating panoramic camera and laser scanning was proposed. The projection points of the interest region of the image corresponding to the target region in the point clouds and precise identification of nodes were completed; (3) A node classification method and optimization method based on density peak clustering was proposed to solve the problem of node aliasing and processing node center in some areas of interest, for the classification and displacement calculation of grid structure nodes. The proposed method is validated on the scale frame model of a gymnasium, demonstrating the practicability of the proposed approach. • Aiming at the issue with existing measurement methods relying on complex multi-camera systems, a method based on a single panoramic camera and deep learning is proposed to complete image target detection, which provides a basis for the identification of target areas in the points cloud; • Aiming at the challenge posed by a large number of point clouds models and complex processing, a method of automatically capturing point clouds nodes by integrating panoramic camera and lidar was proposed. • A node classification method and optimization method based on density peak clustering was proposed to solve the problem of node aliasing and processing node center in some areas of interest, for the classification and displacement calculation of cable network structure nodes. [ABSTRACT FROM AUTHOR]

Hybrid reinforced concrete steel (RCS) frames consisting of reinforced concrete (RC) column and steel (S) are used frequently in practice for mid-to-high-rise buildings. RCS frames possess several advantages from structural, economical and construction view points compared to either traditional RC or steel frames. One of the key elements in RCS frames is the beam-to-column joint. This paper suggests a design method to evaluate the mechanical behaviour of a novel type of exterior RCS beam-column connection in which a steel profile totally encased into a RC column is used to connect the beam through the steelwork part of composite section. The proposed design model is developed considering experimental test results and finite element (FE) analyses. In the first part of the paper, an experimental investigation on the static behaviour of the hybrid joint is presented. Four full-scale specimens were tested under monotonic loading. The primary differences between the specimens are the concrete class and the anchorage length of the embedded steel profile in the RC column. The experimental results indicated that the overall behaviour of the specimens was significantly affected by the shear panel deformations of the embedded profile. Next, a finite element model was created. The FE model predictions compared favourably against experimental tests and confirmed the order of yielding/cracking of joint components. Finally a design method based on Eurocodes 2, 3 and 4 is proposed to determine the initial rotational stiffness and the bending resistance of the joint. • Experimental tests on hybrid steel beam to RC column joints with encased steel profile. • Limited impact of long encased steel profile on mechanical characteristics. • Order of yielding/cracking of components evaluated experimentally and by finite elements. • An Eurocode model for the initial rotational stiffness and bending resistance. [ABSTRACT FROM AUTHOR]

This paper introduces a recursive formulation of blind modal identification as an alternative to conventional diagonalization methods based on multi-lagged covariance matrices. While traditional blind source separation methods are effective for modal identification in structural systems, dynamic systems experiencing sudden changes or rapidly changing environmental conditions require real-time algorithms for continuous health assessment. The proposed recursive eigenspace updates on output covariance estimates, using generalized eigen perturbation, show promise in identifying modal parameters for numerically simulated systems excited with white and colored noise spectra. The paper presents a detailed framework based on recursive simultaneous diagonalization, avoiding real-time diagonalization of multi-lagged covariance matrices by incorporating two auto-covariance matrices with different lags. To evaluate the performance of the new real-time algorithm, synthesized data from a five-degrees-of-freedom system is used. A comparison with traditional independent components demonstrates the effectiveness of the proposed approach in separating closely spaced modes with high damping in real-time. Experimental investigations conducted on controlled vibroimpact test beds confirm the robustness of the proposed approach. Furthermore, the paper shows that the modal parameters obtained using the proposed method for the benchmark ASCE-SHM structure are consistent with those obtained from state-of-the-art methods. The examples presented in the paper indicate that real-time mode separation for dynamic systems in operating conditions is feasible, which is a novel contribution in the field of recursive simultaneous diagonalization. [Display omitted] • Recursive simultaneous diagonalization achieved in a computationally efficient technique. • Online modal recovery performed on linear systems and practical benchmarks. • Comparison with traditional BSS based methods demonstrated and the effectiveness established using the proposed recursive method. • Error plots for eigenspace correlation indicates a steady convergence at from 20% sample population. • Development of recursive Mahalanobis distance as a new condition indicator for identifying online change of state. [ABSTRACT FROM AUTHOR]

This paper focuses on a reinforced concrete corbel strengthening method using post-tensioning cables, or just using the prestressing strands themselves, which are led through additionally drilled cable ducts. The text describes a highly efficient method that has also other advantages besides efficiency, which are: the character of the structure of concrete columns with corbels does not change, the prestressing reinforcement is protected by the concrete both mechanically and against elevated temperatures, and it is easy to apply. Firstly, the paper briefly describes some of the other available methods. However, these methods usually utilize the surface of the concrete, which is often impaired. Additionally, the alternative methods cannot be used or are considered in practice to be insufficiently reliable in specific situations. The paper then describes the design, the actual implementation, and verification of the post-tensioning by measuring the concrete deformation on real columns and full-scale corbels. It also discusses the preliminary design using Strut-and-Tie method Other sections of the text describe the measurements on full-scale corbel specimens and the subsequent numerical analysis performed using advanced methods. The concordance of the results confirms the correctness of the implementation and the design of the described strengthening method. • Strengthening of RC corbels by post-tensioning using substitute cable ducts method. • System validation via concrete deformation measured on real corbels and corbels models. • Verification of the strengthening system using advanced numerical analysis. [ABSTRACT FROM AUTHOR]

The use of external steel bracing systems (named exoskeletons) has recently emerged as a convenient technique for seismic upgrading of existing RC structures, as it possibly limits disturbance or interruption of building occupancy. However, although some conceptual formulations of the design problem can be found in the scientific literature, there are no universally accepted design criteria. The present paper highlights how alternative design choices can reverberate their effects on (i) the seismic performance of the upgraded structural system, (ii) its economic and ecological impact. For the sake of simplicity and consistency with the most common approach of practicing engineers, the present study adopted a force-based seismic design approach. The critical discussion proposed herein was obtained by varying the intensity of the seismic base shear force adopted for the exoskeleton design. Results of the design assessment show that the adoption of larger values of exoskeleton seismic design forces may not be the most suitable choice, especially if economic and ecological impacts are taken into account. • The paper deals with designing steel exoskeletons for seismic retrofitting of existing RC frames. • A comparison between three different upgrading solutions is reported. • A critical discussion about upgrading interventions is provided including member- and foundation-level interventions. • The adopted design procedures are consistent with the most common practice. • Economic and ecological impacts are determined with the aim to rate the alternative seismic retrofit options. [ABSTRACT FROM AUTHOR]

Quantifying the uncertainties of engineering systems modeled as nonlinear oscillators subject to random excitation is a theoretically complex and computationally demanding task. Consequently, finding an optimal design of such systems considering their life-cycle performance is prohibitive with Monte Carlo simulation methods. In this paper, an efficient performance-based design optimization approach is developed for finding the optimal parameters of engineering systems modeled as nonlinear/hysteretic oscillators subject to stationary and non-stationary excitation. This novel approach utilizes an arbitrary polynomial chaos expansion to estimate the expected cost of failure without performing a computationally expensive integration over the hazard levels. Moreover, we introduce a novel sequential heuristic optimization scheme based on simulated annealing to minimize the total expected cost over the structure life-cycle. Three examples are included in the paper to assess the developed optimization scheme. First, we use the developed framework to optimize a linear single-degree-of-freedom oscillator subject to broadband excitation. Second, a multi-degree-of-freedom oscillator with cubic nonlinearity in damping and stiffness, subject to stationary broadband excitation, is optimized to show the influence of the problem dimensionality in the optimization process. In the last example, a multi-story reinforced concrete shear building modeled as a multi-degree-of-freedom Bouc-Wen oscillator with stiffness and strength degradation and subject to multi-hazards modeled as stationary (wind excitation) and non-stationary (earthquake) stochastic processes, is optimized. • An efficient performance-based design optimization scheme is developed. • The best design of MDOF systems consider their life-cycle performance. • Statistical linearization is combined with time-variant reliability. • The monetary loss is estimated with an arbitrary polynomial chaos expansion. • A sequential simulated annealing optimization is employed in the framework. [ABSTRACT FROM AUTHOR]

The most common and practical connection between CLT walls can be realized with inclined screws. This choice avoids the realization of more elaborated half-lap or spline joints. The failure mechanism of CLT-to-CLT screwed connections is highly ductile. However, the epistemic and aleatoric uncertainties associated with the capacity estimation of the connection might lead to an undesired overstrength, compromising the expected hierarchy between failure mechanisms. This paper presents the results of an extended experimental campaign to estimate the overstrength of CLT-to-CLT screwed connections. However, the overstrength directly obtained from the experimental tests could be underestimated. In the experimental campaign, the same wood and screw stock is used, which might not represent the actual scatter of the material properties and construction uncertainties of the as-built connection (e.g., the screw inclination). Therefore, this paper attempts to provide a model-driven assessment of the overstrength factor, assuming more realistic values for the parameter uncertainties. The authors propose a method for removing the contribution of epistemic uncertainty to the model-driven estimation of the overstrength based on experimental tests with two Montecarlo simulations. Following the proposed method, the paper compares the overstrength estimations from the experimental tests to the predictions of analytical and nonlinear finite element models. This study has proven that an overstrength factor between 1.8 and 2 can represent the actual uncertainties in as-built CLT-to-CLT screwed connections. • Overstrength assessment of CLT-to-CLT screwed connections. • Proposal of a novel formulation for overstrength. • Experimental tests on CLT-to-CLT screw connections. • Epistemic and aleatoric uncertainties in the overstrength estimate. • Uncertainty propagation in analytical and FE models. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on web crippling behaviour of cold-formed stainless steel square and rectangular hollow sections (SHS and RHS) at elevated temperatures. A total of 21 web crippling tests were conducted under the Interior Two-Flange (ITF) loading condition as codified in ASCE/SEI 8–22 Specification at various temperatures up to 800 °C. Tensile flat and corner coupon tests were conducted to obtain the material properties of the cold-formed stainless steel SHS and RHS at various temperatures corresponding to those pre-set in the web crippling tests. Details of the test specimens, setups and procedures are comprehensively documented in this paper. Furthermore, the specimen temperatures together with the test results, including failure modes, web crippling strengths and load-deformation curves are fully reported. The obtained test results were used to evaluate the suitability of codified web crippling design provision as per ASCE/SEI 8–22, where reduced material properties were used in calculating the web crippling strengths at elevated temperatures. In addition, the test results were also compared with the predictions obtained from existing design rules in literatures for cold-formed stainless steel SHS and RHS at elevated temperatures. Moreover, reliability analyses were conducted to assess the reliability levels of these design provisions. It is demonstrated that the available web crippling design provisions can provide generally conservative and reliable strength predictions, and therefore are deemed suitable for predicting the web crippling strengths of cold-formed stainless steel SHS and RHS at elevated temperatures. • This investigation serves as the first test programme to study web crippling behaviour of CFSS sections at elevated temperatures. • Flat and corner coupon tests were conducted to obtain material properties at various temperatures. • A total of 21 web crippling tests were conducted under ITF loading condition with temperatures up to 800°C. • Test results are reported and existing web crippling design provisions are also assessed. [ABSTRACT FROM AUTHOR]

The collapse of the I-95 overpass in Philadelphia on June 11, 2023, due to a tanker-induced fire, caused significant traffic disruptions to an important transportation system on the East Coast of the United States. The increasing frequency of similar bridge fire events over the last few years has ignited a debate to re-visit the fire performance of bridges and to account for fire hazards in bridge structures. From this lens, this paper employs the established methodology of fire-based importance factors to assess the vulnerability of the I-95 overpass and then examines the causes and mechanisms for its collapse. To complement this methodology, the paper also presents mitigation strategies, if included, that could have mitigated the collapse of this overpass. More specifically, a finite element model is applied to trace the response of an I-95 girder section under combined effects of thermal and mechanical loading, considering three representative fire scenarios: standard, hydrocarbon, and design fire. Results from numerical simulations show that the bridge experienced rapid temperature rise as in the case of a hydrocarbon fire, leading to the failure of steel girders within 15 min of fire exposure. The developed model was also applied to evaluate strategies that could have minimized the collapse of the overpass under similar fire incidents: composite action and fire insulation. Both alternatives contributed to increasing the fire resistance of the steel girder, with the latter option proving to be significantly more effective. Overall, the increasing frequency of bridge fire incidents in recent years demostrates the need to integrate fire hazards into the design of critical infrastructure, particularly critical bridges, to enhance their resiliency under possible fire scenarios. • Vulnerability of bridges for fire induced collapse is highlighted. • The causes and failure modes in the fire induced collapse of I-95 bridge is analyzed. • The strategies that could have minimized the collapse of I-95 bridge is discussed. • An approach for enhancing resiliency of bridges against fire hazard is laid out. [ABSTRACT FROM AUTHOR]

This paper summarises current research findings related to the behaviour and simulation of a relatively new type of structural component: recycled aggregate concrete-filled steel tube columns (RACFST). The first part of the paper presents a review of the latest experimental campaigns on RACFST columns subjected to a variety of loading conditions. For each of loading condition, highlight observations about the behaviour of RACFST columns are presented. The second part of the paper provides a summary of numerical modelling approaches developed for simulating the structural behaviour of RACFST columns. Special attention is paid to the selection and calibration of material models for recycled aggregate concrete. Finally, directions for future investigations in this area are outlined and discussed. The review will benefit researchers and professionals seeking to gain an in-depth understanding of the behaviour of RACFST columns, and fills a gap in existing literature regarding a number of practical issues related to the numerical modelling of these components. • A state-of-the-art review of experiments on RACFST columns is presented. • The experimental behaviour of RACFST columns is summarised. • Different numerical modelling strategies for modelling RACFST columns are discussed. • Research gaps and directions for future investigations are highlighted. [ABSTRACT FROM AUTHOR]

This paper presents a novel developed Sprayed Ultra-High-Performance Cementitious Sandwich Panel (SUHPC-SP) for structural applications. The SUHPC-SP features sprayed UHPC outer layers making it suited for structural load bearing applications, and a foamed concrete core layer offering high thermal properties. With the development of enhanced material properties and novel production methods, the established SUHPC-SP can achieve optimal mechanical performance while minimising the volumes of material required. As such, this study assesses SUHPC-SP potential to increase sustainable outputs over reference Brick and Block (B&B) construction; by quantifying and comparing the whole life cycle environmental and economic impacts of the two methods. A comparative life cycle assessment (LCA) of these types of construction products is presented for the first time in this paper. The study found that integrating SUHPC-SP over typical B&B construction can reduce environmental impacts by as much as 500% and costs by up to 180%. This informs sustainable construction decisions, offering an effective alternative to conventional inefficient building methods and materials. • The study assesses the LCA of sprayed Ultra High-Performance Cementitious Sandwich Panels (SUHPC-SP). • A comparative LCA between SUHPC-SP and brick & block construction was assessed. • Sandwich panels have the potential to reduce costs and environmental impacts. • Using SUHPC-SP over typical brick & block reduces costs by up to 180%. • Using SUHPC-SP over typical brick & block reduces environmental impacts by up to 500%. [ABSTRACT FROM AUTHOR]