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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]

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]

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]

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]

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]

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]

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]

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]

This paper studies network arch timber bridges. The network patterns considered in the paper are suitable for bridges with a light deck on evenly spaced transverse crossbeams. Therefore, the equidistant distribution of hangers fastening points along the deck is assumed. In bridges made of steel and concrete, hangers are usually equally distributed along the arch. In presented cases, hangers distribution along the arch results from values of parameters like: a number of hangers, an arch rise, a bridge span and hangers inclination. This paper introduces a new network pattern as a modification of a radial pattern. The presented analyzes were performed as a parametric study of variable geometric parameters, on a vast set of 2D FEM models of the network arch with modified radial pattern. The focus was on bending moment distribution on the arch, as it is highly sensitive to even small changes in hanger arrangement. In addition, as a light deck may increase hanger relaxation, the number of relaxed hangers was also analyzed. Values of bending moments were obtained from static analyzes of different load cases, with symmetrical and unsymmetrical load applied on the deck. The results indicate, that introduced radial network pattern modification can improve the performance of the network arch. [ABSTRACT FROM AUTHOR]

Concrete roof shells have shown to be inherently able to sustain earthquakes, but the reasons for this apparent seismic resistance have been subject to limited research. Concrete shells exhibit a high structural efficiency and thus can be constructed very thin. Because of their relative lightweight nature, the earthquake forces induced in a thin shell structure are relatively low. However, the shape of a shell structure is typically established so that it performs optimally under gravity loads, carrying the loads to the foundations mainly through membrane action over the shell surface. Unanticipated horizontal forces induced by earthquakes generate bending stresses in concrete shell structures, which could lead to structural damage. Through a parametric study of 8 cm thick, concrete roof shells with a square plan, the research presented in this paper demonstrates that small to mid-sized (span < 15 m) thin concrete roof shells can indeed be intrinsically earthquake resistant. They owe this resistance to their great geometric stiffness and low mass, which lead to high fundamental frequencies that are well above the driving frequencies of realistic seismic actions. Due to these characteristics the shells analyzed in this paper behave elastically under the earthquake excitation, without surpassing the maximum allowable concrete strength. For shallow shells it is observed that the vertical components of the earthquake vibrations, can induce larger stresses in the shell than the horizontal components. It is further demonstrated that by increasing the rise and curvature of larger shells (20 m by 20 m), their fundamental frequencies are increased and the damaging effect of the vertical earthquake vibration components mitigated. [ABSTRACT FROM AUTHOR]

This paper presents a multi-disciplinary approach for identification of historic buildings structural health with combination of Terrestrial Laser Scanning (TLS) survey, Deviation Analysis (DA) and Finite Element (FE) numerical modelling. The proposed methodology was discussed through the application to an illustrative case study: an early medieval period brick minaret (Eğri Minaret) located in Aksaray (central Turkey). After standing upright for several centuries, the minaret has developed tilt, and today the structure is supported with steel cables. Precise direction of inclination, leaning angle, local deviations from circular building shape, deflections from vertical planes, local curvatures and related maps were obtained with high accuracy by DA, based on detailed point cloud 3D mesh model. Differently from traditional approaches in FE analysis, the paper discusses a method for direct transfer of high accuracy TLS based 3D model to FE structural analysis software, subsequently employed to interpret and verify structural health of the historic building. Through the discussion of the results, it can be considered that the integration of these different techniques (being the whole process non-destructive, effective and expeditious for surface analysis) is a promising methodology for health assessment and analysis of historic constructions. [ABSTRACT FROM AUTHOR]

Bridge weigh-in-motion (BWIM) provides an alternative to conventional static weigh station for obtaining vehicle axle weights. Existing BWIM algorithms assume the vehicles being measured are traveling at a constant speed. This is a reasonable assumption for short-span highway bridges, but will yield large error for railroad bridges and bridges subjected to speed varying traffic. This paper presents a static BWIM methodology to improve the estimation accuracy on axle weights when measuring a vehicle traveling at nonconstant speed. A novel speed correction procedure is proposed and incorporated into the BWIM methodology by converting variable speed response data with nonuniform spatial spacing to uniform spacing. This new method can lead to an increased BWIM accuracy for bridges subjected to speed varying traffic. The BWIM methodology proposed in this paper is based on static analysis, and consists of the following components: Speed Detection, Lateral Load Distribution Determination, Influence Line Determination, Speed Correction, and Axle Weight Determination. In this paper, both numerical study and field study have been conducted. The numerical study is performed using finite element analysis to evaluate the performance of the BWIM results when measuring loads traveling at constant speed and variable speed. The results of the numerical study demonstrate the need of applying speed correction for BWIM analysis, and show the proposed speed correction procedure is able to improve BWIM accuracy for a variable speed vehicle to the similar level of accuracy as a constant speed vehicle. Field study is performed on a steel truss bridge located at the University of Alabama campus. With the obtained data on the bridge, the proposed BWIM methodology is applied to determine the axle weights of a vehicle moving at nonconstant speed. Results of the field study show that large error in axle weight prediction is expected when the vehicle is moving at nonconstant speed on the bridge, and correcting the response data using the proposed procedure can significantly improve the accuracy of axle weight predictions. [ABSTRACT FROM AUTHOR]

A test series was carried out and reported in a companion paper on the semi-rigid behaviour of aluminium alloy gusset (AAG) joints subjected to bending moment and axial force. This paper presented the results of an extensive numerical analysis program devoted to the investigation of the bending behaviour of AAG joints. The analysis was developed by means of finite element (FE) models implemented in the non-linear code ABAQUS. The procedure was accurately calibrated on the basis of the available experimental results. It is indicated that the FE models could be used effectively to describe the mechanical performance of AAG joints, including the failure modes, deformation process and bending moment-rotation curves. Furthermore, the shear connector, the thick plate and the advanced contact of bolts and bolt holes could improve the bending behaviour of AAG joints. According to the deformation process of AAG joints, a four-line model was proposed to simulate the bending moment-rotation relationship. To develop a further understanding, the effects of the member height, axial force, bolt pretension force, bolt gap and material nonlinearity on the bending behaviour of AAG joints were investigated. [ABSTRACT FROM AUTHOR]

Heavily-loaded short coupling beams with large amounts of transverse reinforcement fail in sliding shear or diagonal compression under the complex interaction between shear and flexure. These failure modes often occur after yielding of the flexural reinforcement and limit the displacement capacity of the member. To study such failures, this paper compares experimental results with predictions of models with various levels of complexity. It is shown that complex nonlinear finite element models (FEM) can capture adequately the entire behaviour of short coupling beams, while the classical flexural model produces unconservative strength predictions. It is also shown that strut-and-tie models are reasonably conservative provided that their geometry is selected to maximize the strength predictions. To produce similarly adequate strength predictions as those of the FEM – while at the same time maintaining the simplicity of the flexural model – the paper proposes a mechanical model based on strain compatibility. The main assumption of the model links the principal compressive strains in the critical section to the longitudinal strains in the tension zone. It is shown that the model captures well the effect of different test variables on the shear strength. When applied to a database of 24 tests, the model produced an average shear strength experimental-to-predicted ratio of 1.12 with a coefficient of variation of 8.4%. [ABSTRACT FROM AUTHOR]

Material non-linearity of pier members is an important factor that needs to be considered for dynamic analysis of the bridge pier subjected to barge impact. However, many existing studies pertaining to barge impact on the bridge pier are based on the assumption that the pier is rigid or elastic. High-resolution finite-element simulation serves as the main strategy for dynamic analysis of the bridge pier subjected to barge impact considering material non-linearity of pier members. However, high-resolution finite-element simulations are expensive regarding both calculation time and computing resources, thus efficient models are often required. This paper develops the numerical model of the square RC pier column with fixed base. By coupling the simplified mass-spring model developed by the authors previously with the RC pier column at the impact position using fibre beam elements, the efficient model is developed to predict the impact force time-history and dynamic responses of the RC pier column subjected to barge impact. The studies in this paper show that the prediction quality of the proposed efficient model is adequate for different impact scenarios. [ABSTRACT FROM AUTHOR]

A numerical investigation on cold-formed high strength steel (HSS) tubular beams is presented in this paper. The nominal 0.2% proof stresses of the HSS sections ranged from 700 MPa to 1100 MPa. In the complementary study [1], experimental investigation on the beam specimens have been performed. In the present study, numerical modelling methodology for beams was first validated and parametric study on the cold-formed HSS tubular beams was conducted. A total of 423 numerical data was obtained to investigate the structural performance of HSS tubular beams. The experimental and numerical results were then compared with the codified design guidelines from ANSI/AISC 360-10 [2], EN 1993-1-1 [3], AS 4100 [4] and AISI S100 [5] in addition to the predictions from Direct Strength Method (DSM) for square hollow sections (SHS), rectangular hollow sections (RHS) and circular hollow sections (CHS). The codified slenderness limits for sections subjected to bending were examined. Improvements on the design guidelines are proposed in this paper. [ABSTRACT FROM AUTHOR]

This paper describes a study of the Tempul Aqueduct, one of the first structures designed and built by Eduardo Torroja. At a time when computers did not exist, Torroja’s courage and innovation were outstanding. He was in no way constrained by a lack of theoretical knowledge, inadequate materials and the contemporary doubts about cable-stayed structures. In fact, he was able to build one of the world’s first prestressed concrete structures, and a precursor to modern cable-stayed and extradosed bridges. This paper briefly reviews the history of the Tempul Aqueduct, gives the results of the analysis of this structure by several Finite Element Models (FEMs), and compares the FEM results to those obtained by Torroja himself. The FEM results confirm the validity of Torroja’s conceptual design. The paper also contains a detailed analysis of the influence of the structural system on the behavior of the bridge and the effect of removing the live loads with the aim of providing a better understanding of the context and behavior of the Tempul aqueduct. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to the analysis of thin-walled beams. The proposed model is developed by utilizing the eXtended Finite Element Method (XFEM). Global enrichment functions are added to a standard 3D Finite Element (FE) coarse mesh to enhance its performance and reduce the number of degrees of freedom. These analytical functions provide an approximate solution in the longitudinal direction of the beam. The resulting model bridges the gap between the Finite Prism Method (FPM), which provides an efficient approximation to beam bending with analytical functions but has also well-known limitations, and a detailed 3D FE model, which can accurately resolve thin-walled structures but is computationally demanding. Our method can be easily extended for beams with non-prismatic cross-sections (e.g., tapered beams) or with perforations, which makes it more general than other semi-analytical methods, such as the FPM. However, these extensions are not in the scope of this paper. Additionally, one can improve the solution by sectional and/or longitudinal mesh refinements. The performance of the model is investigated on two benchmark problems. The results show that the proposed method captures different global and sectional deformation modes of thin-walled beams when subjected to torsion, including shear-lag and distortion cross-section. Furthermore, convergence studies demonstrate the superior performance of the proposed method as compared to the FPM, and a 3D FE model with a coarse mesh. • A new model is proposed for the analysis of thin-walled beams. • The model is developed based on the extended finite element method. • Global enrichment functions are added based on the free-vibration modes of continuous beams. • An explicit stiffness matrix is formulated for a 3D eight-node brick element with enrichment functions. • The model captures different modes of deformation including shear-lag and distortion of the cross-section. [ABSTRACT FROM AUTHOR]

• A 3D finite element model is developed for the two-step corbel. • A database with 126 corbels is made by parametric analysis. • An analytical model is proposed for the design of two-step corbels. • The proposed analytical model has strength reduction factors calculated. Corbels are a common element in the beam–column connections of precast concrete structures. This paper analyses the failure of a two-step corbels system using computational modeling. A finite element model is developed and calibrated using the test results for two-step corbels without secondary reinforcement but with steel fiber–reinforced concrete. A database is developed from the parametric analyses of two-step corbels, varying the a/d ratio (0.34–0.76), the rate of the main reinforcement (0.19–0.50%), the compressive strength of the concrete (30–70 MPa) and the amount of steel fibers (1.0% and 1.5%). An improved analytical model, using the developed database, is proposed to design the two-step corbels. The reliability of the proposed analytical model is evaluated using a second database, developed in this paper, and a strength reduction factor of 0.66 for failure by yielding of the main reinforcement and 0.56 for failure by crushing of the concrete strut, were obtained. Therefore, the improved analytical model obtained for the design of two-step corbels represents an advance, in terms of structural safety and economy, when compared to the previous analytical models recommended in the literature. [ABSTRACT FROM AUTHOR]

[Display omitted] • A quantitative criterion for determining the deformation mode of tubes under oblique loads is proposed. • A method for fast judging the deformation mode of multi-cell tubes under oblique loads is proposed based on the SVM, with the accuracy above 91%. • The cross-section length and structure height are showed as the main sensitive parameters affecting the oblique load stability of multi-cell tubes. • An optimal method to increase the critical load angle of tube is proposed according to the instability hyperplanes. This paper aims at oblique load stability of multi-cell tubes and proposes a fast prediction method for fast judging the deformation mode of multi-cell tubes under oblique loads based on support vector machines (SVM). Firstly, the finite element model of multi-cell tubes under oblique load is established and verified by the compression experiments. According to the mechanical response and deformation characteristics of multi-cell tubes under oblique loads, a quantitative criterion for determining the deformation of tubes is proposed. Through the combination of finite element data and SVM, the prediction models of four types multi-cell tubes with oblique crushing is established, with the accuracy above 91%. A fast prediction method of critical load angle of tubes is proposed. The analysis of the critical load angle instability hyperplane shows that the cross-section length and structure height are the main sensitive parameters, and the response of the critical load angle is nonlinear. The prediction model proposed in this paper can quickly predict the stability of the multi-cell tubes and provide directions for the optimization of the stability of the multi-cell tubes. [ABSTRACT FROM AUTHOR]

High wind uplift loads acting on the light gauge steel roofing systems during tropical cyclones and storms frequently cause premature failures of roof connections, which lead to extensive damage to roofing systems. Such roofing system damage was observed in recent cyclones due to premature failures of steel roof batten to rafter/truss connections. They were mostly observed to be due to a localised pull-through failure in the bottom flanges of roof battens. Hence a series of small scale and full scale tests of roof battens was first conducted to study their pull-through failures. To further enhance the understanding gained from the experimental study and to predict the pull-through capacities of a wide range of roof battens, finite element models were developed and analysed using a suitable failure criterion. This paper first presents the applicability of the failure criterion for different roof batten geometries and screw fastener head sizes. Then it provides the details of a numerical parametric study conducted to study the pull-through failures of roof battens in relation to influential parameters such as batten geometry and screw fastener head sizes. Finally, this paper proposes suitable design equations and capacity reduction factors for the calculation of the design pull-through capacities of thin-walled steel roof battens. [ABSTRACT FROM AUTHOR]

This paper concerns the short-term behaviour of innovative steel-timber composite (STC) floors comprising of cross-laminated timber panels connected to steel girders by various mechanical fasteners and/or glue. The results of four-point bending tests performed on full-scale STC beams are reported and the structural behaviour (the load-deflection response, short-term stiffness, peak load capacity, and failure modes) of the proposed STC system is studied. In addition, extensive non-linear 1D and 2D finite element (FE) analyses of STC beams are carried out and the numerical results are verified against the test results. It is shown that 1D and 2D FE models are adequate in capturing the structural response of the STC beams. Using the FE and experimental results, the composite efficiency of STC beams that can significantly influence their structural behaviour beams is determined and reported in the paper. [ABSTRACT FROM AUTHOR]

In this paper, a new flexibility-based beam-column element with member initial imperfection is proposed for direct analysis or second-order inelastic analysis of steel structures. In past decades, the stiffness-based elements gain great successes in handling large deflection problems while the flexibility-based elements play a dominant role in plastic analysis. Apart from the merits of the above two types of elements, the proposed flexibility-based type element considers member initial imperfection and distributed plasticity along the member length and therefore one element is generally sufficient to model a member for practical design. On the contrary, several stiffness-based elements are required to model a member in order to capture the plastic behavior of member under complex loads. The conventional flexibility-based type elements cannot meet the codified requirements of direct analysis as they do not take member initial imperfection into account and this limitation is removed in the new element proposed in this paper. Several examples are given in this paper to illustrate the accuracy and validity of the proposed element. [ABSTRACT FROM AUTHOR]

The prediction and control of crack widths in reinforced concrete structures has been the subject of research for many years. However, there is still a lack of consensus on the design of reinforcement for crack control in walls with edge restraint. The paper describes an experimental programme undertaken to investigate the influence of early-age thermal contraction and long-term shrinkage on cracking in four edge-restrained reinforced concrete walls loaded in bending about their major axis. Bending was introduced as a result of initial preload as well as restraint of deflection due to volumetric change. The walls measured 3500 mm long by 180 mm thick with heights of 500 mm and 750 mm. The paper highlights the main findings of the experimental programme and presents the results of nonlinear finite element analysis that was carried out to investigate the effects of wall geometry and reinforcement ratio on crack widths in edge-restrained walls. Results suggest that crack widths in edge-restrained walls are significantly influenced by the wall geometric properties such as wall aspect ratio and wall height which are only indirectly accounted for through the restraint factor in crack width calculations to EN 1992. [ABSTRACT FROM AUTHOR]

In this paper, a nonlinear finite element analysis of slab-beam-column connection in precast concrete structures is presented. The detailed experimental results of the full-scale connection have been discussed in a different paper. However, due to the complexity of slab-beam-column connection and the unique features of the tested specimen, the numerical study was carried out to better understand the structural behavior. The internal connection was comprised by corbels, dowels and a continuity bars passing though the column. The FE model was validated using the experimental results of the precast concrete connection and it showed good capacity to represent the behavior observed in laboratory. A parametric analysis was conducted with the variation of the diameter of the continuity bars and the properties of the cast in place concrete. As a result of this study, some information about stresses, strains and displacements not obtained experimentally was determined in the numerical simulation and, with the parametric analysis it was concluded that the diameter of the continuity bars had more influence in the precast concrete connection capacity than the concrete compressive strength. [ABSTRACT FROM AUTHOR]

This paper addresses the structural safety assessment of the Chapel of the Würzburg Residence (Germany), one of the most important churches of the Central European Baroque. It was declared as World Heritage Site by UNESCO in 1981, one of its most unique and distinctive characteristics is the geometry of its complex vaults. Intersections between vaults are warped and vaults surfaces were built using only one layer of brick masonry. In this work, a nonlinear finite elements (FE) model has been developed and used to assess the structural safety of the building. In order to update the model by identifying the dynamic response of the building, experimental ambient vibration tests have been previously subsequently carried out. Operational Modal Analysis (OMA) has been used to experimentally identify both modal displacements and natural frequencies. The numerical FE model is them adjusted using genetic algorithms until its dynamic response resembles that experimentally observed, thus providing a valid model to further analyse the structural behaviour of the building. After briefly descripting the Chapel, the methodology followed to update the numerical model and the obtained results from a non-linear analysis on this over-complex vaulted structure are the main goals of the paper. [ABSTRACT FROM AUTHOR]

This paper investigates the mechanical behaviour of lap steel-timber composite connections using a 3-D continuum-based finite element (FE) model. In the FE models developed, the non-linear behaviour and failure of the timber is captured by a stress-based failure criterion formulated in the framework of continuum-damage mechanics. Yielding of the steel plates and fasteners ( i.e. coach screws and bolts) is captured by an elastic-hardening plastic constitutive law. These FE models are validated by experimental (push-out) tests conducted on laminated veneer lumber (LVL)-steel and cross-laminated timber (CLT)-steel composite lap connections. It is shown that the FE models developed in the paper can replicate adequately the load-slip response and failure mode of the hybrid steel-timber composite connections tested. The validated FE model is used to undertake a parametric study that elucidates the influence of the yield strength and the length of the fasteners and the post-tensioning force in the bolts on the stiffness, load carrying capacity and load-slip behaviour of hybrid steel-timber composite connections. [ABSTRACT FROM AUTHOR]

This paper discusses aspects related to the determination of the buckling resistance of multi-span steel columns and beams in accordance with Eurocode 3 (EN 1993-1-1:2005, 2005). In particular, the paper reviews and extends the method previously proposed by the authors (Gonçalves and Camotim, 2005) for uniformly compressed members (columns) integrated in structural systems, which means that it is (i) system-based , i.e. relies on system parameters, and (ii) consistent with the Eurocode 3 buckling curves. It is shown that, besides making it possible to avoid individual member checks, the proposed approach provides relevant insight into the structural efficiency of the complete system. In order to illustrate the application of the proposed approach, several examples are presented and discussed throughout the paper. For comparison purposes, “exact” buckling (collapse) loads are provided, which are obtained from non-linear elastoplastic finite element analyses including member imperfections. [ABSTRACT FROM AUTHOR]

• The results of a parametric study performed on 72 five-story RC shear walls. • An equation to estimate the plastic hinge length of innovative RC shear walls with improved self-centering properties. • An equation to estimate the inelastic rotational capacity of innovative RC shear walls with improved self-centering properties. The application of damage-resisting reinforced concrete (RC) shear walls is a novel topic in structural engineering. In recent years, more studies have been performed on the response of damage-resisting RC shear walls. These studies were mainly conducted on one-story specimens with limited ranges of dimension, reinforcement ratio, and axial load ratio. Furthermore, the studies were mostly aimed at the performance parameters of damage-resisting walls and overlooked the seismic design parameters, such as the plastic hinge length and inelastic rotational capacity, of the walls. This paper presents a parametric finite element analysis study on the plastic hinge length and inelastic rotational capacity of three types of damage-resisting RC shear walls with improved self-centering properties under cylic lateral loads. The studied walls were reinforced with conventional steel bars and a type of self-centering reinforcement consisting of shape memory alloy (SMA) bars, glass fiber reinforced polymer (GFRP) bars, and post-tensioned high-strength steel strands. The study showed that the plastic hinge length was comparable in partially post-tensioned walls and conventional steel-reinforced RC walls, while the plastic hinge was longer in steel-GFRP reinforced walls and shorter in steel-SMA reinforced walls with respect to conventional steel-reinforced RC walls. It was also shown that the inelastic rotational capacity was comparable in partially post-tensioned and conventional RC walls, while the inelastic rotational capacity was larger in steel-GFRP reinforced walls and slightly smaller in steel-SMA reinforced walls with respect to conventional steel-reinforced RC shear walls. This paper also offeres a method to adapt the plastic hinge length and inelastic rotational capacity formulas of CSA and ACI standards for the seismic design of the studied steel-GFRP reinforced, steel-SMA reinforced, and partially post-tensioned RC shear walls. [ABSTRACT FROM AUTHOR]

• A novel dual-pinned self-centering coupled CLT shear wall (DSCW) is introduced. • An equivalent energy design procedure (EEDP) is proposed for the DSCW. • The EEDP is used to design the DSCWs of a 12-story prototype building. • A detailed finite element model of the DSCW is developed. • The seismic performance of the DSCW is assessed using NTHA and IDA. The use of mass timber structures has considerably grown in recent years. This has increased the demand for sustainable, resilient and high-performance mass timber structural systems. In this paper, a novel self-centering balloon-type cross-laminated timber (CLT) shear wall system, called the dual-pinned self-centering coupled CLT shear wall (DSCW), is proposed for tall building applications. The DSCW consists of two sets of CLT panels that are coupled to one another using self-centering friction dampers and are either pinned at their base or sit on V-shaped truss assemblies. This paper also introduces an equivalent energy design procedure (EEDP) that can be used to design the DSCW such that it meets different performance objectives and roof displacement targets at various earthquake intensities. The procedure was used to design the DSCWs of a 12-story prototype building located in Vancouver (Canada). The DSCWs of the prototype building were numerically modeled and subjected to extensive nonlinear time history and incremental dynamic analyses. The results of these analyses show that the proposed EEDP can be efficiently used to design the DSCW such that it achieves the target roof displacements and performance objectives. The results also show that the DSCWs of the prototype building meet the seismic performance requirements of FEMA P695. Overall, the results presented in this paper demonstrate that EEDP-designed DSCWs have excellent seismic performance and can be safely used in tall buildings located in high-seismicity regions. [ABSTRACT FROM AUTHOR]

• Interaction stresses and load deformation histories of each component were studied. • Parameters effect on confining stress and infill concrete strength were discussed. • The constitutive models of infill concrete and stainless steel tube were proposed. • The fiber element models using proposed models were verified. • The international design codes were assessed and new design equation was proposed. Concrete filled double-skin tubular (CFDST) stub column with outer stainless steel circular hollow section (CHS) and inner carbon steel CHS is presented in this paper. It combines the strength of stainless steel, concrete and carbon steel, and also provides the stainless steel's durability, ductility and corrosion resistance properties along with the lighter weight due to the sectional feature. Finite element analysis (FEA) is done in this paper and the developed FE models are verified with the available test results on the basis of failure modes, full load-deformation curves and ultimate strengths of the specimens. Afterward, a series of parametric analysis are conducted to investigate the structural performance of each component and the overall column as well as the confining stresses between the tubes and concrete. In addition, the effect of stainless-steel grade, concrete strength, carbon-steel strength, diameter-to-thickness ratio of outer tube, diameter-to-thickness ratio of inner tube and hollow ratio on confining stress and mechanical property of sandwiched concrete is studied. The constitutive models of sandwiched concrete and outer stainless steel tube under plane stress are proposed. Based on these proposed models, the fiber element model is used to predict the mechanical properties of this composite column and then checked with the finite element modelling (FEM) outputs. Different design methods such as ACI code, European code, continuous strength method (CSM), Han et al. method and Nie et al. method are assessed to evaluate the applicability and accuracy. Finally, a new design method for calculating the ultimate bearing capacity of the CFDST stub column is proposed, which exhibits good agreement with the results of the FEA. [ABSTRACT FROM AUTHOR]

• Reliable 3D finite element models are developed for FRP-confined concrete-encased cross-shaped steel columns (FCCSCs). • An in-depth understanding on the complex confinement mechanism of FCCSCs is achieved. • The effects of key parameters on the mechanism and behaviour of FCCSCs are thoroughly examined. Fibre-reinforced polymer (FRP)-confined concrete-encased cross-shaped steel columns (FCCSCs) are an emerging type of hybrid columns. In an FCCSC, the concrete is subjected to combined confinement from the steel section and the FRP tube, leading to an enhanced load capacity and excellent ductility of the column. While several recent experimental studies have demonstrated the excellent structural performance of FCCSCs, the complex confinement mechanism behind their structural behaviour has not been clarified or thoroughly examined. This paper presents a comprehensive study aiming to investigate the confinement mechanism of FCCSCs. In this paper, the experimental observations of FCCSCs are first summarized, followed by three-dimensional FE modelling of the columns. The FE models, after being verified against the test results in various aspects, are used for a systematic parametric study. In this study, the complex interaction between the three components of FCCSCs (i.e., FRP tube, steel section and concrete) is illustrated explicitly and the effects of key parameters (i.e., flange width, flange thickness, web thickness and FRP tube thickness) are examined separately and thoroughly, leading to an in-depth understanding of the confinement mechanism of FCCSCs. In particular, through the examination on the distribution of steel flange-to-concrete normal pressure, it is shown quantitatively that the variations of the dimensions of the steel section in a practically wide range have only marginal effects on its confinement to the concrete, while the increase of FRP tube thickness tends to reduce the confinement effect from the steel section. [ABSTRACT FROM AUTHOR]

• Experimental and numerical studies on concrete-filled cold-formed steel elliptical stub columns were conducted. • Three different grades of concrete (C40, C70, C100) were investigated. • Predictions from current design methods were compared with test and numerical results. • New design method considering the confinement effect was proposed. • The strength predictions by the new design method with the resistance factor of 0.9 are accurate and reliable. The present paper reports an experimental and numerical investigation on the behavior of concrete-filled cold-formed steel elliptical stub columns. The test program was performed on four elliptical hollow sections infilled with concrete of three different grades (C40, C70 and C100). Thirteen fixed-ended stub columns were tested and details of test program are described in this paper. The test program was further supplemented with numerical analyses, where finite element model was firstly developed to emulate the compressive behavior observed from the tests and then used to generate more numerical data via parametric studies. The test results together with the numerical data derived herein were compared with the predictions by the current design rules for concrete-filled steel tubular columns with conventional cross-section shapes. The current American Specifications ANSI/AISC 360 and ACI318 as well as the European Code EN1994-1-1 were evaluated. The comparison demonstrated that both American Specifications result in generally conservative and reliable compressive strength predictions for concrete-filled cold-formed steel elliptical stub columns, whilst the predictions by the European Code are accurate but not reliable. New design method considering the confinement effect was proposed herein, which could provide accurate and reliable compressive resistance predictions for concrete-filled cold-formed steel elliptical stub columns. [ABSTRACT FROM AUTHOR]

The determination of the nonlinear response of structural members subjected to a close-in explosive threat is challenging. There are various ways to quantify the blast resistance and mode of failure of a structural member, e.g. experimental testing which is expensive and time-consuming, or high-fidelity finite element analysis which is also time-consuming. The familiar analytical approach using an equivalent single-degree-of-freedom (SDOF) system is much less costly, however, as will be shown in this paper, may lack accuracy. Based on an extensive study of the nonlinear response of a ground-floor column of a high-rise building subjected to close-in explosive threat, using nonlinear explicit finite element analysis as well as analytical single-degree-of-freedom (SDOF) system approach, the source of inaccuracy of the analytical approach is identified, and an empirical approach using Multivariable Polynomial Regression (MPR) is established. The paper presents a head-to-head comparison of the results produced by finite element analysis, the SDOF system analysis, the empirical approach, and experimental test data to emphasize the accuracy and time-efficiency of the proposed approach. The approach has the potential to establish itself as a time-efficient preliminary vulnerability assessment methodology of structural members subjected to close-in blast loading. [ABSTRACT FROM AUTHOR]

A simplified method for predicting the deflections of composite box girders with corrugated steel webs is presented in this paper. In the proposed method, the governing equations of the composite box girder bridge are derived based on the principles of the minimum total potential energy method. The vertical deflection of the composite box girder bridges with corrugated steel webs is obtained by solving the governing equations with the associated boundary and load conditions. The accuracy and efficiency of the proposed method are validated for three composite box girders with corrugated steel webs (single-cell and double-cell box girders) with the results obtained based on the finite element method. [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]