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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]

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]

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]

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 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]

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]

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 is concerned with the behaviour of square concrete-filled dual-stiffened steel tubular (CFDSST) slender columns with a concentrically-placed inner circular steel tube. Previous studies have illustrated that these columns have greater structural performance in terms of load-carrying capacity compared with conventional concrete-filled stiffened steel tubular (CFSST) columns. However, the behaviour of CFDSST slender columns filled with ultra-high strength concrete (UHSC) has not been investigated and current design codes do not include provisions for UHSC, although it is increasingly popular owing to demands for structures to be lighter and more sustainable. Accordingly, the current paper fills that gap in existing knowledge and explores the behaviour of CFDSST slender columns using finite element (FE) analysis. The available test results from previous studies were collated and are employed to validate the numerical model. The validated FE model is then employed to investigate the axial load versus deflection responses for a wide variety of UHS-CFDSST slender columns. The behaviour of both intermediate-length and long columns is assessed through parametric analyses. The results of these studies show that the strength of the concrete sandwiched between the two steel sections, the yield strength of outer steel tube, and the outer tube slenderness ratio have a significant effect on the axial resistance of UHS-CFDSST intermediate-length columns, while the capacity of long columns is most affected by the sandwiched concrete strength. The ultimate resistances are compared with different available design methods, and AISC 360–16 code is recommended for predicting the ultimate resistance of UHS-CFDSST slender columns with modifications proposed to account for the different components forming this innovative cross-section. • New research is presented on the behaviour of square concrete-filled dual-stiffened steel tubular (CFDSST) slender columns. • Ultra high strength concrete is employed for the infill, for the first time. • An advanced finite element model is developed and validated. • The behaviour of intermediate-length and long columns is assessed by parametric analyses and reliable design is proposed. • The results show the potential of these sections to offer innovative structural solution for heavily loaded scenarios. [ABSTRACT FROM AUTHOR]

Applications of concrete-filled square (or circular) stainless-steel tubes keep increasing in cold-region coastal engineering structures. However, their behaviours under low-temperature bending have not been fully investigated, which brings obstacles to their engineering applications. To address this issue, this paper investigated flexural behaviours of concrete-filled square/circular stainless-steel tubular beams (CFSSSTBs/CFCSSTBs) at low temperatures through eight four-point bending tests. The main studied parameters were low temperatures (20∼−60 ℃) and cross-section type (circular or square shape). Test results showed that both CFSSSTBs and CFCSSTBs exhibited flexural failure and exhibited excellent ductility under low-temperature bending benefiting from the excellent ductility of stainless steel; bending resistances of CFSSSTBs and CFCSSTBs were improved by 5% and 22%, respectively. This study also developed finite element models (FEMs) for simulations on flexural behaviours of CFSSSTBs/CFCSSTBs at low temperatures. The FEMs considered both low-temperature material and geometric nonlinearities. Validations against eight tests proved the capacities of FEM simulations on low-temperature flexural behaviours of CFSSSTBs/CFCSSTBs. Finally, the code equations in Eurocode 4 and AISC 360 were used to predict the stiffness and ultimate bending resistances of CFSSSTBs/CFCSSTBs. Validations showed that the code equations underestimated the bending resistances of CFSSSTBs/CFCSSTBs. This study provided fundamental information on the flexural bending mechanism of CFSSSTBs/CFCSSTBs) at low temperatures. • Low-temperature flexural behaviors of concrete-filled stainless-steel tubular beams (CFSSTBs) are reported. • Low temperatures improve stiffness and bending resistances of CFSSTBs. • Bending resistances of circular CFSSTBs are more improved than square ones as T decreases. • Code equations conservatively predict low-temperature bending resistances of CFSSTBs. [ABSTRACT FROM AUTHOR]

The request of material savings in bridge constructions leads to the development towards slender and lightweight structures, which are more sensitive to human-induced vibrations caused by walking pedestrians. The resulting accelerations do not endanger the structural safety, but can be perceived as unpleasant for the user and must therefore be restricted within the limit state of serviceability. For this purpose, the guidelines define acceleration intervals, called as "comfort levels" (CL), which evaluate the comfort of the pedestrians, given the maximum acceleration of the bridge. The model for human-induced loads in the design guideline is based on conservative and deterministic simplifications. In particular, the uncertainties in the human gait parameters are neglected. The main objective of this paper is to develop an uncertain load model for walking pedestrians based on Fourier series. The aleatory and epistemic uncertainties in the human gait parameters are quantified with appropriate uncertainty models relying on available data. In a dynamical finite element analysis, the model is used to simulate groups of pedestrians randomly walking over a bridge to calculate the resulting acceleration amplitudes. The approach is applied to a single span beam and to a real world footbridge using a 3D finite element model. The results are then evaluated within the CLs, enabling new assessment methods. • Uncertainty quantification for human-induced loads. • Introduction of a Fuzzy Fourier load model for walking pedestrians. • Simulation of human-induced vibrations of a real world footbridge with polymorphic uncertain data. • New assessment methods for the footbridges comfort level. [ABSTRACT FROM AUTHOR]

To support more sustainable construction, this paper experimentally investigates the cyclic behavior of laminated timber (Laminated Veneer Lumber (LVL)) and glubam (Glue Laminated Bamboo) connections with slotted-in steel plates in terms of experimental test, numerical simulations and parameter identification. Experimental tests included eight different configurations: two materials (LVL and glubam), two bolt diameters (8 and 10 mm), and one or two bolts. Two different cyclic-loading protocols were applied for each type of connection: only tension and tension/compression. The observed behavior is then compared to a finite element model developed in OpenSeesPy, which takes into account factors such as sliding, contact, pinching, cyclic stiffness, and strength degradation. To identify the best set of parameters for the model, three different approaches are considered: genetic algorithm, fast deterministic neural network, and probabilistic Bayesian method. First, the model identification is carried out by means of a genetic algorithm-based optimization. The parameter-identification results are evaluated in terms of elastic stiffness, yielding point, and ductility. Next, a sensitivity analysis is performed to determine the significance of the parameters, and an innovative approach combining neural network and sensitivity analysis is proposed for fast and preliminary parameter identification. Then, probabilistic Bayesian identification is employed to calculate the posterior distribution of the model parameters identified and the confidence bounds of the estimated response. Finally, different model identification parameters are compared and suggestions for algorithm selection are provided. • Comprehensive study on laminated bio-based connections with slotted-in steel plates • Experimental characterization of the cyclic behavior of eight configurations • OpenSeesPy model with zero-length elements based on Pinching4 and slip • Sensitivity-based neural network method for parameter identification • Comparison and discussion on three model parameter identification techniques. [ABSTRACT FROM AUTHOR]

Modal shapes derived from Operational Modal Analysis (OMA) lack normalization with respect to masses, hindering direct estimation of effective mass or modal participation factors. The mass-change method is suitable to solve this issue since it proposes an experimental derivation of scaling factors for modes based on OMA results in different load conditions. However, in the case of bridges, the method application is challenging, as significant static masses are required on the deck for OMA in loaded conditions. To address this challenge, trucks can be used as added masses during standard static proof load tests for bridges, making the mass-change method feasible. However, the presence of trucks introduces dynamic coupling effects among bridge and vehicles, potentially complicating the dynamic identification. This paper proposes a methodology to exploit data obtained from OMA on bridges loaded with stationed trucks within the framework of the mass-change method in order to get the modal scaling factors for the mass normalisation of mode shapes and taking into account possible effects of the dynamic coupling between the two systems. To this purpose, the bridge dynamics with added stationed trucks is studied by introducing a finite element model to address the bridge-vehicles dynamic coupling. Then, a simple but effective 2-degree of freedom system is introduced to develop a parametric investigation in a non-dimensional manner in order to provide a practical tool for engineers to account for the bridge-truck dynamic coupling effects. Finally, numerical applications are proposed to derive some conclusions about the effectiveness of the proposed procedure and its suitability in real applications. • A mass-normalization bridge mode shape procedure using stationed vehicles is presented. • The dynamic coupling effects among bridge and stationed vehicles is addressed. • A FE and a simple 2-DoF models are developed to study the dynamic coupling effects. • A general tool to support the dynamic identification of loaded bridges is provided. • Dynamic tests can be done during mandatory static proof load tests for new bridges. [ABSTRACT FROM AUTHOR]

Concrete production and construction are responsible for a considerable share of the total carbon emissions annually. With the emerging need to cut carbon emissions from the construction sector, there has been a big interest in optimising the embodied carbon of superstructures. However, limited attention is given to optimising the embodied carbon of foundations as most designers are more interested in addressing the optimal foundations cost instead. For the first time in the open literature, this paper presents a generic genetic-algorithm-based tool to optimise the design of reinforced concrete piles. The algorithm is capable of allocating the optimal design parameters and geometry for reinforced concrete piles at any given soil conditions and required pile capacities. The algorithm is used to compare the environmental impact of different concrete pile types; solid cylindrical piles, hollow cylindrical piles, solid tapered piles and hollow tapered piles at different load capacities, the optimisation results are then compared to common industrial pile designs to quantify the possible carbon and material savings. Results show that a significant cut of more than 70% of the embodied carbon values can be achieved if the optimal pile type is used compared to common industrial design. Moreover, a finite element model built and validated over ABAQUS is used to compare the geotechnical performance of the different pile geometries. Finite element analysis results show a negligible difference between the stiffness of the different pile types when tested in the same soil conditions highlighting an outstanding optimisation efficiency of the proposed optimisation tool. [Display omitted] • A novel pile optimisation algorithm is proposed. • The embodied carbon of different pile geometries is compared. • A finite element model is presented to compare the different piles' stiffnesses. • Optimal pile geometries can save up to 70% of the carbon emissions compared to common pile designs. [ABSTRACT FROM AUTHOR]

This paper examines the influence of variable axial force on the seismic performance of flexural domain reinforced concrete (RC) columns through experimental testing of five full-scale specimens. The test results demonstrate that fluctuating axial force, when combined with simulated cyclic seismic loading, significantly impacts the flexural behavior of RC columns. The behavior of RC columns under fluctuating axial loads was markedly different from that of columns under constant axial loads. A notable observation was that the failure mode of the columns transitioned from ductile flexural failure to flexure-shear failure when comparing columns subjected to constant axial loads to those subjected to fluctuating axial loads that alternated between compression and tension. This study further demonstrated that the lateral load capacity of the columns, along with their deterioration, was significantly influenced by both the fluctuating pattern and intensity of the axial forces, as well as the displacement ductility. An empirical equation was proposed to estimate the residual lateral load capacity of flexural domain RC columns under varying axial forces, providing a practical tool for designers to assess the behavior of columns under different loading conditions. To corroborate the conclusions drawn from the experimental investigation and gain further insights into the influence of fluctuating axial force on the seismic behavior of flexural domain columns, this study additionally proposes a finite element (FE) model. According to the experimental and numerical results, an empirical equation to estimate the ultimate drift capacity of RC columns subjected to varying axial force is also proposed. • Experimental investigation on seismic performance of flexural reinforced concrete column subjected to varying axial forces. • Finite element model was proposed to corroborate the conclusions drawn from the experimental investigation. • Two empirical equations were proposed to estimate the residual lateral load capacity and ultimate drift capacity. [ABSTRACT FROM AUTHOR]

This paper introduces a method for analyzing resonance between Offshore Wind Turbine (OWT) structures and wave loads using Wave Participation Factor ratios (WPFs). Despite temporal fluctuations in WPFs due to wave loads, they prove effective for identifying key modes influencing wave load behavior in both fixed and floating OWT structures. For fixed OWT foundations, nonlinear soil behavior causes some natural frequency variations under wave forces, but they typically remain within a limited range. Lower natural frequency modes show minor WPFs, reducing the risk of resonance with wave loads. Modes with higher natural frequencies have substantial WPFs and are less prone to resonance. However, precautions are needed to avoid rotor-induced wind load resonance. Floating OWT structures have large WPFs in their first six near-rigid body motion modes, while mooring line stiffness leads to substantial variations in these modes. It's crucial to control the first six nonlinear frequencies outside the dominant wave load range. Beyond these six modes, natural frequencies significantly exceed wave load frequencies, reducing resonance concerns. In summary, this study presents an effective method for assessing resonance between OWT structures and loads, providing valuable insights for structural design and operational safety. • Wave participation factor ratios (WPF) were developed to find wave resonance for OWTs. • For fixed OWTs, lower modes show minor WPFs, reducing the risk of wave resonance. • Higher modes with substantial WPFs are less prone to resonance for wave loads. • Floating OWTs have large WPFs in the first 6 near-rigid body motion modes. • It's crucial to control the first 6 frequencies outside the dominant wave load range. [ABSTRACT FROM AUTHOR]

The condition of stay cables greatly affects the safety of bridges. Cable force is an important health indicator of cables, but it is difficult to directly assess the condition of a stay cable by the cable force because the cable force is affected by the operating environment including temperature and vehicles. In this paper, the condition of the stay cable is assessed by constructing a normalized sequence of the vehicle-induced cable force peaks (VICFPs) of the stay cables on the same side. The normalized sequence of the VICFPs of the same side cables is only related to the structure itself, and the damage to the cable can cause an abnormal reduction in the sequence. First, the normalized sequence of the VICFPs of the same side cables is derived and defined, and the change in the normalized sequence of the VICFPs with damage is qualitatively analyzed by a simplified mechanical model. An indicator of the change in the normalized sequences is constructed, and the condition assessment of the stay cables is realized by building the control chart of the indicator. Second, via a finite element model of a cable-stayed bridge, the sequences of different vehicle weights, different lanes, and different damage degrees are verified and analyzed. Last, the proposed method is applied to an actual bridge, and the results indicate that the proposed method has sufficient feasibility and accuracy. • The vehicle-induced cable force peak (VICFP) is derived through mechanical analysis using influence coefficients. • The effects of various damages on VICFP are distinguished by a simplified model, and a condition indicator is established. • A new method for condition assessment of stay cables is proposed by combining indicators with mean value control charts. • A vehicle-induced cable force extraction method based on local largest distribution density fitting is presented. • The numerical simulations and an engineering application are carried out to verify the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a novel corrugated steel-sprayed ECC (CSSECC) composite arch, which possesses high load-bearing capacity and fast construction speed. To investigate the ultimate load-bearing capacity, composite effect, and key mechanical indices, five 6 m-span arch specimens were tested. A finite element model was developed, and parametric analysis was conducted. The results indicate that the ultimate load-bearing capacity and damping ratio of the CSSECC composite arch specimens can reach 3.4 and 6.5 times that of the corrugated steel (CS) arch, respectively, and increasing the ECC thickness significantly enhances the damping ratio. Both studs and epoxy resin contribute to the composite effect, but studs are more reliable than epoxy resin even though their design shear connection degree is the same at 1.2. Finally, a design method for the stability bearing capacity under axial compressive was proposed. • Four CSSECC composite arches and one CS arch were tested under three-point loading. • Load-displacement curve and composite effect were analyzed to examine the work mechanism. • FEM was developed and the influence of parameters on the stability bearing capacity under axial compressive were analyzed. • A design method was proposed to predict the stability bearing capacity under axial compressive. [ABSTRACT FROM AUTHOR]

This paper investigates the buckling behaviour and load-carrying capacity of G550 high-strength cold-formed steel multi-limb built-up section columns under axial compression. Each built-up section consists of multiple lipped and unlipped channel sections connected by self-tapping screws. The C3U1 section is formed by three C-sections (i.e. lipped channel section) and one U-section (i.e. unlipped channel section), while the C2U2 section is formed by two C-sections and two U-sections. The experimental programme involved tensile coupon tests, measurements of initial geometrical imperfection, and column tests on ten C3U1 and ten C2U2 multi-limb built-up section columns. The numerical modelling programme was then performed, with the nonlinear finite element models created and validated against the experimental results. The applicability of the codified Effective Width Method and Direct Strength Method for predicting the strengths of G550 high-strength cold-formed steel multi-limb built-up section columns, as specified in the American Specification and Australian Standard, was then evaluated. The evaluation results showed that the codified Effective Width Method led to rather conservative and less accurate failure load predictions for G550 high-strength cold-formed steel multi-limb built-up section columns, while the codified Direct Strength Method provided accurate and consistent failure load predictions and thus applicable to the design of G550 high-strength cold-formed steel multi-limb built-up section columns. Concerning the lack of design guidelines specifically for multi-limb built-up sections, a modified Direct Strength Method was thus proposed as an alternative design method and shown to provide accurate failure load predictions. • The structural performance of G550 high-strength CFS multi-limb built-up section columns was investigated. • 20 axial compression tests on G550 high-strength CFS multi-limb built-up section columns were conducted. • FE models were developed and validated against test results and then used for future analysis. • Codified design methods were evaluated for their applicability to G550 high strength CFS multi-limb built-up section columns. • A modified DSM was proposed as an alternative design method and shown to provide accurate failure load predictions. [ABSTRACT FROM AUTHOR]

To explore a cost-efficient bridge structure system and expand the options for long-span bridges in mountainous regions, we propose an innovative cable-stayed deck arch (CSDA) bridge with significant potential benefits. This paper discusses the conceptualization, structural design considerations, and implementable construction methods of this bridge-type. We trial designed two CSDA bridges with span arrangements of 268 + 350 + 268 m and 280 + 3 × 380 + 280 m to demonstrate the versatility of our proposal in different topographic situations and its ability to accommodate both single and multiple main spans. The finite element analysis confirms the mechanical properties and structural feasibility of the conceptual designs. A comprehensive comparison with other types of bridges under identical conditions reveals that this new hybrid bridge is not only lightweight in structure, excellent in performance, and elegant in form, but also cost savings and with minor environmental impact. The preliminary study indicates that the CSDA bridges are suitable for the construction demand of high-rise pier and long-span bridges in mountainous terrain, and also an economical option for the main span between 350 to 400 m. • An innovative cable-stayed deck arch bridge is proposed, taking into account the design considerations and construction methods. • The bridge type accommodates different hilly terrain conditions and can be arranged with either single or multiple main spans. • The cable-arch load ratio is derived analytically and has proved the rationality of the structure system. • The proposed bridge exhibits excellent structural performance and other advantages. [ABSTRACT FROM AUTHOR]

Identifying the optimal intensity measure (IM) contributes to reducing uncertainties in probabilistic seismic demand models (PSDM) and enhancing confidence of their results. Although many studies have discussed appropriate IM s for mainshocks, relatively less attention is paid to the potential aftershock effect. In particularly, the optimal IM s for developing PSDM of transmission towers subjected to sequential earthquakes has not been well studied previously. Therefore, this paper conducts a multi-metric evaluation to identify the optimal IM in the context of mainshock-aftershock (MSAS) fragility analysis of transmission towers. This evaluation process includes collecting a set of ground motions recorded with varying magnitudes and fault distances to construct MSAS sequences, followed by comprehensive discussions on their seismic characteristics by comparing thirty-six potential IM s candidates. Additionally, a finite element model of a transmission tower is established to numerically investigate different engineering demand parameters (EDP) of the tower under the selected MSAS sequences. The optimal PSDM of the transmission tower is determined by evaluating each couple of IM − EDP on a logarithmic space using multiple evaluation metrics. Through this analysis, the first-mode spectral acceleration S a (T 1 , ξ) is identified as the optimal IM as it exhibits excellent correlation, efficiency, practicality and proficiency with the EDP s of the transmission tower, especially with the inter-segment displacement ratio. Consequently, seismic fragility curves of the transmission tower are developed using the optimal IM. The research outcome can contribute to improving the understanding of the probabilistic assessment of transmission towers in the MSAS scenario. • Seismic characteristics of mainshocks and aftershocks are differentiated. • Aftershock effect on the seismic responses of a transmission tower is numerically quantified. • Multi-metric evaluation of optimal IM s for transmission towers is performed. • Neglecting subsequent aftershocks will underestimate seismic fragility. [ABSTRACT FROM AUTHOR]

This paper aims to explore the enhancement effect of spiral stirrup on concrete-filled cold-formed steel built-up box (CF-CFB) columns. Herein, four specimens were designed and fabricated to explore the impact of the spiral stirrup and riveted form on the axial compression performance of CF-CFB columns. Then, the finite element model of spiral stirrup-reinforced concrete-filled cold-formed steel built-up box (RCF-CFB) stub columns was established, and a systemic parametric investigation was conducted to explore the impact of geometric and material parameters on the compression performance of RCF-CFB stub columns. Afterwards, the analysis included an assessment of contact stress and stress distribution was conducted to uncover the confining effect. The analysis results revealed that the failure mode of the RCF-CFB column was tube buckling and concrete crush, accompanied by the spliced tube separating at the buckling area. The built-in reinforcement could significantly improve the performance of the built-up column, while riveted forms of spliced steel tubes had little effect. Furthermore, the axial bearing capacity of the RCF-CFB column would increase with the enhancement in steel yield strength, concrete strength, tube thickness, and longitudinal bar diameter. Finally, a calculating method to predict the axial bearing capacity of the RCF-CFB column was proposed, and the applicability of the method was demonstrated by comparison with experimental and FE data. • Compression tests were carried out on the performance of the concrete-filled cold-formed steel built-up box columns. • An analysis model of concrete-filled cold-formed steel built-up box stub columns was established and validated. • A practical method for predicting the axial compression load capacity was proposed. [ABSTRACT FROM AUTHOR]

This paper presents an approach to investigate the effect of temperature on the transmission and distribution of vibration energy for train-track-bridge coupled systems. The vibration of the coupled system can be simulated by integrating the multi-body dynamics model of the train with the finite element models of the track and bridge. The transmission and distribution of vibration energy can be evaluated using a structural intensity method. This approach was implemented to investigate the vibration characteristics of a coupled system under extreme temperature conditions. The system consisted of a CRH2 high-speed train, a CRTS I double-block ballastless track, and an arch bridge. The results show that extreme temperature not only impacts the characteristics of vibration energy transmission in the coupled system but also affects vibration energy distribution. This research provides new insights into vibration control and optimization design for bridges in regions with significant temperature variations. • A vibration energy quantification and visualization method for train-track-bridge coupled systems is proposed. • Hybrid modelling integrating multi-body dynamics and finite element models is performed. • Thermal effect as well as track irregularity are considered. • Vibration energy transmission characteristics of each substructure of the coupled system are analyzed. • The distribution law of vibration energy under various thermal conditions is analyzed for a high-speed railway arch bridge. [ABSTRACT FROM AUTHOR]

Deconstructable structures offer great flexibility and reduce material waste. Fiber Reinforced-Polymer (FRP) decks resting on steel girders combine high durability, lightweight, fast construction, and deconstructablility. Composite action between the decks and girders is achieved using shear connectors. Until now, most shear connectors use adhesives or grouts, limiting their maintenance, reuse, or recycling. This paper presents a closed-form solution to analyze the behavior of an FRP deck connected to multi-girders using variable sequential stiffness shear connectors considering partial Degree of Composite Action (DCA). The analytical model, which is verified using Finite Element model and prior experimental studies, is further used to study stress and deflection for various multigirder configurations. Finally, the DCA considering variable stiffness shear connectors is presented and linked to effective width ratios, paving the way for adopting variable stiffness in bridge standards. • The analytical model accounts for multi-girder configurations. • Closed-form solution for deconstructable variable stiffness shear connectors. • A design guideline linking effective width for different degrees of composite action. [ABSTRACT FROM AUTHOR]

Constructing an interpretable model for the long-term deformation Structural Health Monitoring (SHM) of earth-rock dams is of great significance for improving the safety state evaluation and monitoring effect. In this paper, a physics-data-driven model for the deformation SHM of earth-rock dams is proposed based on deep mechanism knowledge distillation. Firstly, the deterministic model is established based on the Finite Element Model (FEM) and outputs the hydraulic load component curve and aging component curve. Then a regression prediction model (HTSGAN) between influencing factors and deformation measurements at multiple measurement points is established based on the Graph Convolutional Network (GCN) and attention mechanism. Finally, the Teacher-Hydraulic-Time-Seepage Graph Attention Networks (T-HTSGAN) model is established based on the feature-based multi-teacher knowledge distillation using the knowledge of hydraulic loading physics and soil-rock creep physics of the FEM for mechanism constraints. The model effectively solves the problems of poor model interpretability and lack of physics knowledge constraints in previous earth-rock dam SHM models. The research results are applied to a project of a 185.5-meter-high concrete-faced rockfill dam, and the predictive performance of the model is more effective and stable through the comparison of six baseline models. The comparative analysis of the component curves proves the effectiveness of the proposed knowledge distillation method for mechanism constraints and improves the interpretability of the neural network model. Therefore, the model is more suitable for engineering applications. • A new physics-data-driven deformation monitoring model for earth-rock dams is proposed. • Mechanical constraints of dam SHM model is further improved by a new neural network model mechanism constraint method. • The application results of a high CFRD show that the model has high accuracy and good engineering applicability. [ABSTRACT FROM AUTHOR]

Conventional cold-formed steel wall systems suffer from low lateral loading-carrying capacities and stiffnesses, which represent the main barrier to their use in multi-story buildings. To address it, a cold-formed steel center-sheathed shear wall (CFSCSSW) system with higher lateral load-carrying capacity and better lateral structural performance is proposed. This paper presents experimental, numerical, and analytical studies on the behavior of the proposed CFSCSSW subjected to combined vertical and horizontal loads. Firstly, a full-scale test was conducted, with the test setup, loading procedures and measuring instrument reported in detail. The obtained test results, including the load-carrying capacity, failure mode and strains, were fully analyzed. Then, finite element modeling was conducted to simulate the experimental observations, and parametric studies were carried out to investigate the influences of different geometric and loading parameters on the behavior of CFSCSSWs. Finally, a three-strip model with a variable position on end studs (TSM-VPC) was proposed for CFSCSSWs and shown to accurately simulate the direction of the tensile field within the sheathing and also resulted in high accuracy in calculating the load-carrying capacities, followed by a design example. ● An innovative cold-formed steel center-sheathed shear wall (CFSCSSW) system is proposed. ● A full-scale test on CFSCSSW under combined loading is conducted, with test results fully analysed. ● The influences of key geometric and loading parameters are investigated through parametric studies. ● A three-strip model is proposed for calculating the load-carrying capacity of CFSCSSW. [ABSTRACT FROM AUTHOR]

Traditionally, uncertainty quantification in the context of liquid storage tanks has primarily focused on ground motion record-to-record variability, along with partial consideration of material randomness. This paper presents a comprehensive framework for addressing "modeling uncertainty" in the seismic analysis of rectangular tanks, including the influence of foundation interactions. The framework encompasses uncertainties inherent in both general finite element and mathematical modeling techniques, as well as uncertainty in modeling parameters (e.g., hydrodynamic mass and concrete constitutive model). This is achieved through the implementation of an efficient design of experiments. By employing an innovative intensifying artificial acceleration, over 26,000 transient simulations are conducted, spanning the full spectrum of structural behavior from linear to nonlinear regimes. Through a series of uncertainty quantification and sensitivity analyses, this study assesses bias and dispersion arising from diverse model assumptions. Furthermore, fragility analysis and machine learning post-processing techniques are employed to extract latent insights from the generated data. The outcomes underscore that numerical and mathematical modeling uncertainties can bear comparable significance to ground motion record-to-record variability. The adoption of distinct modeling strategies introduces biases in fragility curves, particularly within higher damage states. Consequently, it is advised to account for modeling randomness directly (via simulation) or approximately (leveraging the insights from this study) in any uncertainty quantification related to storage tanks. • A unified framework is proposed for epistemic uncertainty quantification. • The modeling variability is quantified in the liquid storage tanks for the first time. • An innovative intensifying artificial acceleration is used for uncertainty quantification. • The significance of β m o d e l i n g for coupled tank–foundation system is demonstrated. • A detailed machine learning-based sensitivity analysis is performed. [ABSTRACT FROM AUTHOR]

Given that the stiffness of joints has an important influence on the global behavior of steel structures, considerable efforts have been made to develop methods to characterize their behavior. In the component method, that is adopted by Eurocode 3, one of the most relevant components is the column web panel in shear; however, this component has never been the subject of research when additional plates are welded between the column flanges to attach the secondary beams to the minor axis of the column. This paper proposes a stiffness formulation for the component column web panel in shear with additional plates, taking into account the stiffening contribution of these additional plates. To archive this, four experimental tests of beam-to-column joints were carried out, a finite element model was calibrated with the experimental data by comparing moment-rotation and moment-deformation curves, a parametric study of sixty different configurations was performed with the calibrated finite element models to obtain the stiffness of the component column web panel in shear and the initial stiffness of the joint. Then, the proposed stiffness formulation for the component was validated with the results of the parametric study, obtaining a very good agreement. Finally, a compilation of the stiffness formulation of all the components of the joint type extended end plate with additional plates was made and validated, when comparing this analytical stiffness with the initial stiffness of the joints of the parametric study, satisfactory concordance was found. [Display omitted] • Study of end plate bolted steel joint with additional plates welded between column flanges to attach secondary beams. • Experimental work to validate finite element models. • Development of a parametric study with finite element models. • Proposal of a formulation for the component column web panel in shear with additional plates welded between column flanges. • Compilation and validation of the stiffness formulation for all the components of the studied joint. [ABSTRACT FROM AUTHOR]

Semi-oval hollow section is an innovative cross-section profile, including one semi-circular flange, one flat flange and two flat webs. While the semi-circular flange (exposed to fluid or wind) offers a low level of hydrodynamic or aerodynamic drag, the flat elements facilitate connections with other members. This paper presents experimental and numerical investigations into the local buckling behaviour and resistances of austenitic stainless steel semi-oval hollow sections under combined compression and bending. A testing programme was firstly conducted and included initial local geometric imperfection measurements and ten eccentric compression tests. In conjunction with the testing programme, a numerical modelling programme was performed, where finite element models were developed to validate against the test results and conduct parametric studies for expanding the test data pool over a wider range of cross-section dimensions and loading combinations. The obtained test and numerical data were used to evaluate the applicability of the relevant design interaction curves for austenitic stainless steel rectangular hollow sections, as prescribed in the European code and American specification, to austenitic stainless steel semi-oval hollow sections. On the basis of the evaluation results, the codified design interaction curves were found to provide conservative resistance predictions. Finally, an improved design interaction curve, with more accurate end points and suitable shape, was developed and led to more accurate and consistent resistance predictions for austenitic stainless steel semi-oval hollow sections under combined compression and bending. • The local buckling of austenitic stainless steel semi-oval hollow sections under combined loading was studied. • Ten eccentric compression tests were conducted. • FE models were developed to simulate the test results and then used to perform parametric studies. • The applicability of relevant codified design interaction curves was assessed, showing conservatism. • A new design interaction curve was proposed and provided improved design accuracy and consistency. [ABSTRACT FROM AUTHOR]

In large-span bridges or high-rise buildings, CFST columns with large width-to-thickness ratio are often adopted, which require proper stiffening measures to improve the mechanical behaviors. This paper presents a comparative study of circular CFST stub columns with different stiffening methods, including longitudinal stiffeners (cross-shaped, T-shaped and ordinary type), additional reinforcement and headed studs. Axial compression tests have been conducted to investigate the effects of different stiffening methods on the failure mode, ultimate strength and ductility of the circular CFST stub columns. Finite element models are established to simulate the columns' behaviors and conduct parametric studies. Based on test and simulation results, an axial bearing capacity prediction model for circular CFST stub columns stiffened by longitudinal stiffeners is proposed. It is demonstrated that the failure modes of the steel tube and core concrete are changed by the longitudinal stiffeners. The longitudinal steel stiffeners as well as reinforcing cage can effectively improve the axial bearing capacity and ductility of the columns. The latter is more efficient in promoting the bearing capacity while the former is more efficient in improving the ductility and residual strength. A combination of the additional stirrups and the ordinary stiffeners will be a more economical choice. In addition, the proposed formula gives better prediction accuracy compared to the equations in various design codes. • Axial compression tests are conducted on circular CFST stub columns with different stiffening methods. • Longitudinal stiffeners with different shapes, additional rebar and headed studs are studied. • Finite element models are established to simulate the columns' behaviors and conduct parametric studies. • An axial capacity model for circular CFST columns stiffened by longitudinal stiffeners is proposed. • Longitudinal stiffeners and reinforcing cage can improve the axial capacity and ductility of the columns. [ABSTRACT FROM AUTHOR]

The seismic response is a critical aspect of structural engineering, as it directly influences the design and safety evaluation of such systems. Structural seismic response becomes more complicated when unavoidable uncertainties in the structure are considered. Therefore, solving and analyzing the stochastic dynamic response of structures efficiently and accurately is of great significance. Various uncertainty quantification methods such as the stochastic finite element method, Monte Carlo method, and polynomial chaos expansion method have made significant progress in this field. However, these methods do not provide a comprehensive study of the seismic response of stochastic structures and efficiency problems rapidly emerge as the number of random variables increases. This paper delivers a comprehensive study of the seismic dynamic response of space truss and reticulated shell structure considering uncertainties in material properties, geometry, and loading. To this end, the finite element model of the structure was first modeled and the deterministic solutions were obtained. Then, polynomial surrogates are modeled for the natural frequency, mode participation factor, mode superposition response, and transient response of the structure under stochastic uncertainties. The sparse grid technique is used to select sparse quadrature points, which overcomes the curse of dimensionality caused by full grid integration. The results demonstrate that the sparse grid-based polynomial chaos expansion is more efficient. Uncertainty quantification reveals the uncertainty of modal analysis, response spectrum analysis, and transient response analysis of space truss and reticulated shell under seismic excitation. In summary, this study provides valuable insights and an efficient and accurate uncertainty quantification tool for the seismic dynamic analysis of stochastic structures, ultimately contributing to safer and more robust structural designs. • Analyzing the seismic dynamic response of stochastic structures comprehensively. • Sparse grid-based PCE for quantifying uncertainty in stochastic dynamics. • Addressing the dimensional catastrophe of traditional non-intrusive PCE. • Sparse grid-based PCE metamodel for post-processing is more efficient and accurate. [ABSTRACT FROM AUTHOR]

• 15 tests of bolted joints between Fe-SMA and steel plates are carried out. • The reliability of reinforcing steel structures with bolted Fe-SMA is verified. • The key influencing parameters of the bolted joints are obtained. • Some design suggestions on bolted joints between Fe-SMA and steel plates are proposed. The new intelligent material Iron-based Shape Memory Alloy (Fe-SMA) brings novel solutions for the performance rehabilitation of existing steel structures. To fully utilize the potential of the Fe-SMA active prestressed reinforcement, the systematic study of reliable joint is significant. Therefore, the bolted joints between Fe-SMA and steel plates was experimentally studied in this paper, whose reliability and convenience in metal structures have been generally accepted. Firstly, a series of 15 mechanical performance tests of bolted joints between Fe-SMA and steel plates were carried out. The key influencing parameters of the bolted joints were obtained, and different failure modes were observed, which can provide experimental verification for further finite element modelling and theoretical study. Furthermore, the effects of end distance e , edge distance s , bolt diameter d , thickness of Fe-SMA plate t and bolt layout on the ultimate load-bearing capacity, initial stiffness and failure modes of the bolted joints between Fe-SMA and steel plates were discussed, and some specified design suggestions on bolted joints between Fe-SMA and steel plates were proposed. This paper mainly aims to provide the experimental basis and design recommendations for compilation of the relevant specifications, which is expected to advance the scientific application of Fe-SMA in the performance rehabilitation of steel structures. [ABSTRACT FROM AUTHOR]

This paper discussed the torsional performance of special-shaped concrete-filled steel tubes (SCFST) columns. A pseudo-static test research of nine specimens was carried out under pure torsion. The investigated factors include section shape, stiffening form, width-to-thickness ratio of column limbs and steel tube thickness. The failure modes, hysteresis curves, skeleton curves, energy dissipation capacity, and stress distribution were analyzed to investigate the torsional performance of specimens. The overall failure modes of different section forms are ductile damage. There are a number of 45°oblique buckling in the steel tube, and the steel plates at the top and bottom of the column are transversely torn. At the concave corner, the weld of multi-cell and the welded point of the tensile steel bar were cracked from the top to bottom. Besides, the concrete is mainly crossed by torsional oblique cracks. The hysteresis curves of the SCFST columns are plump shape without pinching phenomenon, representing good energy dissipation capacity. The effect of stiffened methods is the most significant for the torsional performance. The ductility and bearing capacity of multi-cell specimens are better than those of tensile-bar stiffened specimens. Based on the same torsion ratio of concrete and steel tube and ignoring the effect on the tensile bars, calculation methods for initial torsional stiffness and torsional bearing capacity were proposed. Comparison results show that the calculation method has good performance in terms of the accuracy and efficiency. • A pseudo-static test research of special-shaped concrete-filled steel tube specimens was carried out under pure torsion. • The finite element model for SCFSTs was developed and parametric analysis was conducted. • Calculation methods for initial torsional stiffness and torsional bearing capacity were proposed. [ABSTRACT FROM AUTHOR]

Prefabrication assembly technology has been widely recognized due to its rapid construction, minimal environmental impact, and superior quality of precast components. The reliability and construction convenience of the connection joints of precast components are particularly important. In this paper, a novel Ultra High-Performance Concrete (UHPC)-filled concrete-filled steel tube (CFST) socket connection (UCSC) was proposed for the column-beam connection. To explore the shear behavior and shear load transfer mechanism of UCSC joints, four direct shear experiments were conducted in terms of different parameters (socket depth, presence of studs). Meanwhile, ABAQUS was used to perform a systematic parametric analysis (socket length, embedded length, outer diameter of CFST, thickness of steel tube). The results indicated that the shear performance of UCSC joints was significantly influenced by both the socket depth and the outer diameter of CFST. The proposed finite element model (FEM) can predict the load-displacement relationships of UCSC joints with a maximum peak load error of 2.3 %. Combining the experimental results and numerical results, a simplified calculation model was formulated to accurately estimate the shear bearing capacity of UCSC joints, and was verified by numerical and experimental results with a maximum error of 8.6 %. The research results have practical implications for the preliminary design of UCSC joints to avoid non-ideal failure mode. • Experimental studies were conducted to evaluate the shear performance of UCSC. • A FEM was established to predict the force-displacement curve and shear failure mode of UCSC. • A simplified calculation model was developed to predict the ultimate shear bear capacity of UCSC. [ABSTRACT FROM AUTHOR]

Being critical components in composite structures, the short-term structural behaviour of stud shear connectors has been extensively investigated. Despite this, there has been somewhat limited attention devoted to their time-dependent behaviour. In this paper, the results of four long-term push-out tests are reported: the test parameters including the loading age and stud diameter. The test results are shown to be simulated accurately by a finite element model established using ABAQUS, in which the long-term behaviour of the concrete is considered by implementing a stepwise approach. The numerical procedure is applied to conduct a parametric analysis, with the effects of different parameters, viz., the loading age, concrete material, external environment, stud size and reinforcement ratio being considered. Based on the numerical results, an analytical formulation is derived for the creep coefficients of composite members with different loading ages. Comparisons with FE model data shows that the derived equation has sufficient accuracy and can be applied for designing composite structures considering their long-term response. • Tests of stud connections under sustained loading; • Significant creep slip of the connection found during the tests; • Creep model of stud connection proposed for analysis of composite structures. [ABSTRACT FROM AUTHOR]

Concrete-filled corrugated steel tubular (CFCST) column is a novel type of steel-concrete composite column, comprising four corrugated steel plates, four square-section steel bars at the corners, and infilled concrete. The transversely placed corrugated steel plates can effectively prevent their premature local buckling, release the axial load, and provide lateral confinement effects on the infilled concrete. This paper investigated the axial compressive behavior of CFCST columns through experimental, numerical, and theoretical approaches. Experiments were conducted on 20 specimens, focusing on their axial load-resistant behavior. The specimens demonstrated excellent axial bearing capacity, ductility, and residual bearing capacity. Besides, the mechanical behavior of corrugated steel plates throughout the loading process was analyzed through the development of the horizontal and vertical strains. Furthermore, a finite element (FE) model was developed to simulate the axial compressive behavior of CFCST columns, which was validated against the experimental data. The FE model was used to analyze the compressive behavior of each part in CFCST columns, revealing that the infilled concrete and steel bars primarily bear the axial load, while the corrugated steel plates mainly provide lateral supports to the infilled concrete. Finally, a simplified method for calculating the critical width of corrugated steel plates and a formula for the axial bearing capacity of CFCST columns were proposed. It was indicated that the limiting width-to-thickness ratio of the corrugated steel plates was larger than that of the steel elements in conventional CFST columns. These formulas were demonstrated to be accurate enough and suitable for the engineering designs. • Axial compression tests involving 20 CFCST columns were performed. • Finite element models were developed and validated against test results. • The mechanical behavior of each part of the CFCST column was analyzed in detail. • A theoretical analysis was conducted to determine the critical width of the corrugated steel plate. • Theoretical formula of the axial bearing capacity of the CFCST columns was proposed. [ABSTRACT FROM AUTHOR]

Although extensive experimental and numerical studies have been conducted on the axial performance of steel tube and sandwiched concrete jacketed CFST columns, contableurations with outer square tubes and inner circular CFST components are rarely found. This paper investigates the axial performance of square steel tube and sandwiched concrete jacketed circular CFST columns, examining the effects of outer steel ratio and sandwiched concrete strength on failure patterns, relative load-strain curves, and load-bearing capacity. The analysis of ultimate compressive capacity confirmed the effective confinement provided by the outer square steel tube. Based on the experimental results, a finite element model was established to further study the working mechanism of retrofitted columns. The load on components, distribution of longitudinal stress and transverse constraint stress on concrete revealed that the inner concrete experiences dual confinement effects from both inner and outer steel tubes, with the constraint of the outer square steel tube becoming significant only during the load dropping phase. Furthermore, a simple equation was proposed for predicting the axial compressive load-bearing capacity of retrofitted columns using superposition methods and design codes. Comparison results demonstrated good agreement between experimental and calculated values. • The axial performance of circular CFST columns strengthened with square steel tube and sandwiched concrete jackets was investigated. • The outer tube thickness had a greater impact on the compressive strength of retrofitted columns compared to the sandwiched concrete strength. • A finite element model was established to study the force mechanism of axially-loaded circular CFST columns strengthened with square STSCJ. • An equation was proposed to calculate the axial compressive capacity of retrofitted columns based on the superposition methods and design codes. [ABSTRACT FROM AUTHOR]

This paper studied the seismic behavior of a novel self-centering concrete-filled steel tubular column-steel beam (SCSTCSB) joint. The restoring force was provided by the post-tensioned tendons arranged in the CFST columns. Cyclic loading tests were performed on five 1/3 scaled specimens by varying the parameters of steel tendon type, concrete strength (f c), and axial compression ratio (n). The failure modes, hysteresis behavior, stiffness and strength degradation, energy dissipation, post-tensioned tendons response, residual deformation, and strain distribution were studied in detail. The finite element models were established to capture the stress distribution of the joints. In addition, parameter analysis was performed by expanding 17 finite element models. The results show that the ratio of residual deformation to beam rotation angle of the specimens ranged from 0.068 to 0.172. And the proposed joints demonstrated excellent self-centering ability. The self-centering (SC) performance of joints with ordinary steel tendons was better than that of joints with high-strength steel tendons. With the increase of n , the SC performance of the joints intensified at the lower ratio (n from 0.1 to 0.3) and weakened after n = 0.3. The flexural capacity of the joints improved with the increase of axial compression ratio (n), width-thickness ratio (D / t), diameter of steel tendons (d), and assembly part strength (f y,a). • The seismic behavior of self-centering CFST column-beam joints with PT tendons arranged in column was investigated under cyclic loading. • Ordinary steel tendons exhibited better results than high-strength steel tendons in self-centering (SC) performance. • With increase of axial compression ratio, the SC performance of joints intensified at the lower ratio (0.1-0.3) and weakened after n = 0.3. • The flexural capacity of the joints increased with increasing axial compression ratio, concrete strength, diameter of steel tendons and assembly part strength. [ABSTRACT FROM AUTHOR]

In this paper, experiments were carried out to analyze the behavior of the square columns reinforced longitudinally by GFRP bars along with different ratios of hooked end fibers under eccentric compressive loading. Eight short square columns with a cross-section dimension of 150x150mm and a height of 1200 mm, were fabricated to conduct the experimental program. A 150 mm enlargement in column-cross at both ends was considered to develop an eccentric axial load. The columns were tested under different load eccentricity ratios (0.26, 0.5, 1). Different tie spacings (50, 100, 120) mm. Different ratios of steel fibers 0 %, 0.5 %, and 1 % were incorporated into the concrete mix. It was observed that columns with steel fibers demonstrated good characteristics, including higher ultimate load, increased ultimate deflection, and enhanced ductility and toughness compared to the columns without steel fibers due to multiple cracking behaviors. The ductility of the columns reinforced with GFRP bars was enhanced by 46.8 %, and 68 % for steel fiber volume ratios of 0.5 % and 1 %, respectively. The energy absorption was increased by 42 % and 77 % for steel fibers ratios of 0.5 % and 1 %, respectively. When GFRP bars were used as longitudinal reinforcement, there was an improvement in the bond behavior between the concrete and the GFRP bars. All concrete columns reinforced by GFRP bars failed due to flexure-compression failure. There was no observed rupture of GFRP bars during the experimental test and the maximum strain did not reach 40 % of their ultimate strain capacity. Nonlinear Finite Element analysis was conducted to simulate the behavior of tested columns. The equations from previous studies and the codes were established to predict the nominal peak capacity of columns considering all parameters. In general, there was a reasonable level of agreement observed between the experimental data and the theoretical results determined for seventy-column specimens in the current study and from previous studies in the literature. • Performance of concrete columns reinforced with GFRP bars under an eccentric compressive loading. • Variable ratio of End – Hooked steel fibers were used. • Behavior was examined in experimental and analytical manners. • 4-Non-linear finite element analyses were achieved and compared with experimental results. • The nominal capacity of the columns was predicted. [ABSTRACT FROM AUTHOR]

Equipping cross-ties on the cables of cable-stayed bridges to form a cable network is regarded as an effective measure to suppress large cable vibrations and has been realized in practical engineering. However, most of the existing studies on the suspended cable (small sag) network have ignored the contributions of dynamic axial forces to transverse forces of the cables. More importantly, the dimension of the characteristic matrix is relatively large. Therefore, the current study introduces the transfer matrix method (TMM) to solve the in-plane free vibration problem of a two-cable network with dynamic axial forces of the cables considered simultaneously. Compared with the methodology utilized by the previous studies, the dimension of the resulting characteristic matrix is smaller and is independent of the number of cross-ties. Three cases, i.e., a two-cable network with two cross-ties, with three cross-ties and with four cross-ties, are explored in detail. Their frequencies and mode shapes are compared with those obtained by finite element model (FEM) to demonstrate the validity of the results in this paper. Meanwhile, the effects of dynamic axial forces on the first two frequencies and mode shapes are analyzed. The results show that the contributions of dynamic axial forces should be taken into account in transverse forces when calculating the first two frequencies of the cable network with flexible cross-ties. • A novel analytical method is proposed to solve the cable network system. • Dynamic axial forces are included to obtain more accurate results. • The dimension of the resulting characteristic matrix is small. • The dimension does not increase with the increase in the number of cross-ties. [ABSTRACT FROM AUTHOR]

The assumed mode method (AMM) is widely used for dynamical modeling but faces increasing challenges in developing low-dimensional and high-precision models of complex structures for investigations of nonlinear dynamical responses and active vibration control. This is mainly because the current complex structure has an increasing number of components, each of which needs to be discretized by multiple assumed modes in dynamical modeling, leading to increasing degrees of freedom for the system. To address this issue, this paper proposes a dimension-reduced method based on the assumed mode weighting method, referred to as Mode Weighting Method (MWM). The modeling process of a multi-beam structure is fully presented as an example to show the strategy of the MWM. During this process, the assumed mode (AM) model (the dynamic model derived in terms of a set of assumed modes) is developed first where the joints of the structure between its components are considered as artificial springs and each component is discretized by its vibration modes without constraints. The components of the eigenvector of the characteristic equation derived from the AM model are taken as the weighting coefficients to get the approximate analytical global modes of the structure by multiplying the corresponding assumed modes. Consequently, a nonlinear dynamic model with a few degree of freedom is obtained by discretizing the structure with the weighted modes. Moreover, a technique for simply obtaining the weighted mode (WM) models by directly processing the AM model through a transformation matrix is presented. To validate the proposed method, the simulations on the natural characteristics and the dynamical responses for both linear and nonlinear models, are performed respectively based on the WM and the finite element models, where both results are well matched each other. This work provides a new way of developing advanced dynamical modeling methods for structural dynamics design, optimization, and active vibration control. [Display omitted] • A Mode Weighting Method (MWM) for nonlinear dynamical modeling of complex structures. • A low-dimensional and high-precision dynamical model of a muti-beam structure. • Investigation of the dynamical characteristics of the muti-beam structure with nonlinear elastic supports. [ABSTRACT FROM AUTHOR]

Concrete dams are prone to cracks during construction and operation process. Cracks on the upstream surface may induce the risk of hydraulic fracturing, thereby significantly reducing the safety of dam structure. Nevertheless, image processing technology, non-destructive testing technology and structural performance analysis technology with cracks are in a relatively independent state, leading to difficulties in analysis of actual cracks combined with numerical simulations. This paper proposes a novel approach for combination of intelligent identification technology and refined finite element method (FEM) for modeling and simulating the hydraulic fracturing resistance of the actual crack in concrete dams. With image processing technology and non-destructive testing technology, direction and depth of actual cracks are identified and extracted, then the 3D geometric model of actual cracks is generated. The refined model with the identified actual crack is constructed by the node projection strategy. This approach is used to assess the hydraulic fracturing resistance of the concrete dam with actual cracks in the alpine region. The results demonstrate that the critical crack depth of hydraulic fracturing is 12.93 m, and the opening width is 1.01 mm, which is 2.53 times the limit value for Class D cracks in the code (DL/T5251–2010). The refined modelling method based on actual crack detected on site can accurately evaluate the crack state compared to the conservative code. • A novel approach for generation and simulation of the 3D actual crack is proposed. • Refined FEM model with the identified actual crack is established by node projection strategy. • Hydraulic fracturing resistance of the actual crack in the concrete dam is evaluated. • Refined simulation method based on actual crack can accurately evaluate crack state compared to the conservative code. [ABSTRACT FROM AUTHOR]

Climate change exacerbates the structural deterioration of concrete highway bridges, posing a threat for them to resist vehicle collisions. However, the investigation into the safety of highway bridges under the joint effects of climate change, deterioration, and collisions caused by heavy vehicles is lacking. This paper presents a practical framework for assessing the lifetime fragility of concrete highway bridges exposed to both heavy vehicle collisions and climate change-accelerated corrosion. The main challenge of applying fragility-based approach in this framework lies in developing surrogate demand models, which traditionally requires extensive time-consuming simulations of vehicle-bridge collisions using finite element methods. To overcome this, an impact force time history model is proposed as an efficient alternative to represent collision demands on bridge piers by heavy vehicles. Implementation of this model has demonstrated a remarkable reduction of approximate 90% in computational time requirements compared to the collision analysis. The framework enables the generation of fragility surfaces at any given time throughout the bridge's service life. The effectiveness of the framework is demonstrated using an example highway bridge, and fragility surfaces are generated for various climate scenarios. The results indicate a rise in the probability of collapse, from 0.4% for a structurally sound bridge to 87.2% after 80 years of chloride exposure when subjected to a heavy vehicle collision with an impact velocity of 100 kph and a truck weight of 36 t. Additionally, the impact of climate change is evident, further increasing this probability to 97.4%. These findings underscore the significant roles that both corrosion and climate change play in influencing the vulnerability of concrete bridges to heavy vehicle collisions. Addressing these factors in collision design and lifetime assessment is essential for ensuring the structural resilience and safety of bridges over time. • Evaluation of bridges' vulnerability under the combined impacts of heavy vehicle collisions, corrosion, and climate change. • Development of an impact force time history model as a substitute for dynamic collision simulations. • Characterization of bridges' collision resistance, incorporating site-specific chloride exposure and climatic conditions. • Analysis of bridges' time-dependent failure probabilities during collision events throughout its lifespan. [ABSTRACT FROM AUTHOR]

Prestressing is a viable and effective technique used in concrete structures that allows the improvement of their performance. Its efficiency depends on the layout of the tendons, understood as the number of strands, their profile, curvature, and eccentricities. Layout design is a laborious and usually iterative trial-and-error process that aims to ensure that stress limits are not exceeded while, on the other hand, to minimize the total weight of prestressing steel. To automate the process, this research presents a novel genetic algorithm and a machine learning-based approach with a parametrically defined geometry of a tendon consisting of straight lines and circular arcs. The paper describes assumptions, implementation, and validation of the methods using a two-span two-girder bridge structure as an example. The genetic algorithm was incorporated to minimize the total weight of prestressing steel and ensure a correct design with no limit state exceedances. Since prestress evaluation in statically indeterminate structures requires repetitive and time-consuming numerical simulations, usually finite element analysis (FEA), a neural network was used to predict numerical output based on the layout parameters. The introduction of the neural network significantly reduced the total computation time. The results show the usability of the proposed approach in further studies and in engineering practice. • Genetic algorithm and neural network combined establish an effective optimization framework for prestressed concrete design. • Genetic algorithm is able to find optimal solutions even when all candidates in initial generations exceed the constraints. • Neural network can successfully replace time-consuming Finite Element Analysis (FEA) in design process. • The profile geometry of a tendon can be easily parametrized using linear segments and circular arcs. [ABSTRACT FROM AUTHOR]

In this paper, the boundary-based finite element method (BFEM) is developed for the bending-extension coupling analysis of shear deformable laminated composite curved beams with non-uniform thickness. The curved beams are discretized into a series of uniform straight segments. Based upon the first order shear deformation theory and the reciprocal theorem of Betti and Rayleigh, the boundary integral equations (BIEs) associated with each beam segment are derived and expressed in explicit form. The fundamental solutions required in the BIEs are obtained explicitly from the associated Green's function. Since no singular integrals, numerical integrations and function interpolations are involved in the BIEs, our proposed BFEM provides an exact solution for a straight beam with uniform thickness, and only one single element with two end nodes is required for our analysis. Even only an approximate solution is provided for a curved beam with non-uniform thickness, BFEM converges faster than the conventional finite element method, and the results are in well agreement with those obtained by the commercial finite element software. Through the illustrated numerical examples, its generality is shown by: (1) stacking sequence of laminates: symmetric or unsymmetric; (2) beam geometries: straight, stepped, or curvilinear with uniform or non-uniform thickness; (3) loading types: axial force, transverse force and/or bending moment; distributed or concentrated; and (4) supporting conditions: clamped, simply supported, or free; with or without internal supports. • Incorporate with bending-extensional coupling and transverse shear deformations. • Develop BFEM for composite laminated curved beams with non-uniform thickness. • Solve all involved integrals and construct element stiffness matrices explicitly. • Derive explicit-form analytical solutions for straight uniform laminated beams. • Provide more efficient and accurate results than conventional finite element method. [ABSTRACT FROM AUTHOR]

Light weight steel-based panels are largely used for the envelope (walls, roofs) of different kind of buildings. They are typically designed from the weather-related conditions of the site (climatic actions, thermal comfort). Despite their low weight, they have adequate load carrying capacities under transverse loads. However, under extreme loading conditions, like the high intensity pressures associated with external explosions, the panels can be heavily damaged or detached from the structure. The study presented in the paper describes the results obtained on liner tray walls tested for transverse loading until complete failure. The test program included also shear tests on end fastenings. The liner trays were arranged as single span systems supported on side beams and loaded at the mid-span. After a quasi-linear response, the maximum flexural strength is reached. Then, due to a local instability, there is a drop in capacity, followed by an increase in response capacity due to development of catenary forces. If the end fasteners have adequate resistance, the ultimate capacity in the catenary stage can be significantly higher than the peak flexural capacity. The ultimate capacity depends also on the in-plane stiffness of the support columns. • Experimental assessment of liner tray wall panels in case of transverse loads. • 2 types of end support conditions, one with low in-plane stiffness and one with high in-plane stiffness were considered. • Increasing the number of end fasteners allows development of catenary forces. • Tests on liner trays confirmed the results on individual fasteners. • Easy to use Finite element models calibrated against test data. [ABSTRACT FROM AUTHOR]

Glued-laminated timber (GLT) is an efficient and renewable material with potential to enhance sustainability in construction, but its potential has been partly hindered by relatively large uncertainty related to its strength. Previous research indicate that by linking information from the grading process to the GLT fabrication more reliable GLT beams could be made. To this end, this paper represents a finite element based modelling approach combining a continuum damage model with sequentially linear analysis that is suitable for simulation of the bending stiffness and strength of GLT beams. The model has been implemented in Matlab and can be easily integrated into different parametric simulation workflows. Based on validation against 36 experimentally tested GLT beams, the model can predict bending stiffness with high accuracy and provides reasonably accurate predictions for bending strength. The model is also capable of producing qualitatively realistic fracture patterns of GLT beams. The mesh-size study suggests that the best agreement for bending strength with test data is obtained with a sparse mesh, which is discussed in detail. The model is considered suitable for follow-up studies involving the optimization of GLT beam layups. • A novel simulation approach for glued-laminated timber beams is presented. • The model has been validated against experimental data with good agreement. • The model can also qualitatively predict post-peak fracture behaviour. • Mesh-size effects are evaluated and suggestions based on findings are given. [ABSTRACT FROM AUTHOR]

Operational Modal Analysis (OMA) is a powerful approach to be used in structural performance assessment of historical masonry buildings during their service life. OMA is effective for detecting global damage to masonry buildings, although in some conditions it may exhibit poor sensitivity in detecting local/slight structural damage. Additionally, establishing robust correlations between changes in modal features and the residual load-bearing capacity of monitored buildings is an unresolved task in most of real-world applications. To deepen into these aspects, this paper presents an experimental and numerical program involving two full-scale masonry wall specimens tested under controlled laboratory conditions. Progressive damage was induced in diverse structural settings, and OMA was used to identify the modal features of the wall systems at increasing damage levels. Damage-induced decays in modal features were correlated with performance limit states related to the structures' residual load-bearing capacity, while non-linear Finite Element (FE) models were defined to replicate the tests. The obtained results contribute to filling current research gaps by demonstrating that natural frequencies and mode shapes can be sensitive to local and slight structural damage, also proposing correlations between damage-induced decays in modal features and performance limit states, hence corroborating the use of FE models for replicating damage-induced decays in both vibration frequencies and mode shapes. • Full-scale masonry walls are progressively damaged in diverse structural settings. • OMA is used to detect localized/small damage to the tested masonry buildings. • Modal features are found to be sensitive to the increasing damage entity. • Correlations are made between structures' modal features and load-bearing capacity. • FE models can accurately replicate damage-induced modifications in modal features. [ABSTRACT FROM AUTHOR]

Shear walls are widely used as lateral load-resisting systems in high-rise building structures. The design and nonlinear analysis of shear walls under seismic loads for recoverability are complicated and challenging, which demands nonlinear computer modeling procedures. This paper presents a novel finite element named Double Vertical Beam-column with Shell Element (DVBSE) for the nonlinear analysis of complex reinforced concrete shear walls with columns. The DVBSE is implemented in the open-source finite element program OpenSees. The theoretical formulations of DVBSE are described in detail. The accuracy of the developed DVBSE is established by comparing the finite element analysis results with existing experimental data on recoverable steel-GFRP composite bar reinforced concrete shear walls. The comparative study demonstrates that the proposed DVBSE is superior to the commonly used finite element model in simulating the responses of recoverable complex shear walls under seismic loads. These research findings contribute to further advancements in the development of new shear wall elements and lay a solid foundation for the nonlinear numerical simulation of innovative shear walls. • A new finite element DVBSE is developed for modeling shear walls under seismic loads. • The DVBSE incorporates vertical fiber-based beam-column elements and shell elements. • The DVBSE is implemented in the open-source finite element program OpenSees. • The accuracy of the DVBSE is verified by test results of recoverable complex shear walls. • The DVBSE offers an efficient approach to simulate the seismic behavior of shear walls. [ABSTRACT FROM AUTHOR]

This paper presents the application of a thick-shell nonlinear finite element analysis procedure to estimate the punching shear resisting performance of reinforced concrete slab-column connections under variable connection shear stress conditions. In the analyses performed, varied connection shear stress conditions stem from slabs being supported by columns with different cross-section aspect ratios, being subjected to different distributions of gravity loading, being constructed with different planar reinforcement ratios in orthogonal directions, as well as the application of unbalanced bending moments. Forty-eight isolated slab-column connection specimens presented in the literature were modelled and analyzed using a thick-shell finite analysis procedure. All numerical results were developed using a predefined set of material models and analysis parameters, a consistent meshing procedure, and are shown to provide meaningful agreement with experimental data without the need for case-specific model calibration or the adoption of specialised failure criteria. The results show that thick-shell modelling methods can be suitable for estimating the punching shear response of slabs subjected to non-uniform shear stress development in connection regions, and can provide similar levels of precision to that obtained for the analysis of idealised slab-column connections typically used for design procedure and model development. • Low-cost shell FEA for punching shear assessment of reinforced concrete flat plates. • Analysis of 45 non-idealised connection specimens representative of real-world construction. • Good agreement between FEA simulations and reported results without model calibration. • Result accuracy comparable to that obtained for more typical idealised connection specimens. [ABSTRACT FROM AUTHOR]