Journal of Constructional Steel Research最新文献

This paper introduces a methodology for developing collapse fragility curves for windstorms, with a focus on assessing collapse of electrical transmission towers for hurricane events. Incremental dynamic analysis (IDA) that incorporates the entire hurricane duration is adopted for collapse modeling. Fragility curves are cumulative distribution functions of a structural limit state such as collapse capacity, which is designated in this work as the intensity measure associated with the onset of collapse. A suite of selected hurricane wind records are used with IDA to propagate uncertainties from wind speeds, directions, and durations to collapse capacities. Compared with earthquake engineering methodologies, this work proposes appropriate approaches for scaling of wind records, fitting of IDA curves from simulation data, and parameter estimation of hurricane fragility curves. Fragility curves are appropriate for use both to quantify uncertainty in the context of performance-based wind design and for regional loss assessments. As inelastic deformations are allowed in performance-based wind design, it is useful to develop fragility curves based on nonlinear time history analysis for the entire windstorm duration, which has not been addressed in prior work.

There exists no analytical model in the literature capable of predicting the stress-strain behavior of hybrid filament wound fiber reinforced polymer (FRP)-concrete-steel double skin tubular columns (DSTC) under axial compression. To address this, an analytical model is first developed to incorporate bi-directional fibers and predict the non-linear hoop stress-hoop strain response in filament wound FRP laminated cylindrical tube under internal pressure. This model is then used to predict the confinement pressure exerted by the FRP tube on the sandwiched concrete in DSTC when subjected to uniaxial compression. Next, an analysis-oriented model is used to predict the complete stress-strain response of DSTC confined by bi-directional FRP tube. The model's predictions are compared with the test results collected from literature, and based on performance parameters, it is concluded that the proposed model significantly reduces the error in predicting the global axial stress-strain behavior of DSTC with bidirectional FRPs. Parametric studies are then performed to understand the influence of geometrical parameters and material properties on the axial behavior of DSTC. It was found that the variation of effective confinement pressure across the concrete section is the key factor influencing the global axial stress-strain behavior. Finally based on these parametric studies, a critical confining stiffness necessary to supress the softening response in DSTC was proposed, which is dependent on the void ratio of these columns.

The so-called ortho-composite-slab combines the orthotropic stiffened steel deck as a lightweight construction for medium and long span bridges with the robustness of composite slabs to handle increasing traffic loads. The structure consists of an orthotropic stiffened steel deck, a relatively thin layer of reinforced concrete and dowel strips with teeth in the form of clothoids as shear connectors. In addition to the significant advantages of low deadweight and long service life, the ortho-composite-slab is characterized by fast and economical production. The construction was investigated by a comprehensive experimental test program in combination with structural-mechanical calculations as part of the AiF-FOSTA research project P 1265 at the TUD Dresden University of Technology. Within the scope of the project, basic principles for the design of ortho-composite-slabs with dowel strips were developed. This paper first gives an overview of the experimental test program. This is followed by a detailed discussion of the static and cyclic tests on sections of the ortho-composite-slab (so-called beam tests). The statistical evaluation of the tests and the assignment to a fatigue resistance curve are presented.

In this paper, we present a novel computational approach for stiffness-update of fire-exposed structural member to rigorously study the thermo-mechanical coupling of a real-time hybrid fire simulation. This approach realistically considers the stiffness and strength degradation of the fire-exposed member at each instance of continuous fire evolution and its effect on the global response of the structure. A newly independent computational and experimental framework for hybrid fire procedure is implemented in this study, which applies a well-suited benchmark structure consisting of high strength steel S690QL. Various case studies with different influencing aspects such as different load ratios, heating rates and computational control parameters are presented to investigate most important temperature- and rate-induced numerical and experimental challenges. In addition, different limitations of HFS approaches in state-of-the-art studies are addressed and enhanced by the new proposed approach. This study marks a significant advancement in real-time hybrid fire simulation and proves the competence of presented methodology for rigorous and robust assessment of the fire performance of structural systems, leading to more realistic fire design of structures.

This study aims to assess the global reliability of coupled transmission tower-insulator-line systems considering soil-structure interaction (CTTILSs-SSI) subjected to multi-hazard of wind and ice. Firstly, two simplified models of CTTILSs-SSI under stochastic wind and ice loads are established, and their governing equations are derived through the Lagrange equation. On this basis, a global reliability assessment framework of CTTILSs-SSI is proposed based on the improved maximum entropy method, in which the global performance function of CTTILSs-SSI is defined via the state variable description method. Finally, a practical ultra-high voltage overhead transmission line located on the icing zone is chosen to illustrate the proposed framework. Moreover, to investigate the influence of soil-structure interaction (SSI) and soil types on the global reliability of transmission tower-insulator-line systems (TTILSs), the global reliability of CTTILSs-SSI with various soil types is compared with that of a fixed base system. The results indicate that under the in-plane wind and ice loads, the global failure probability of TTILSs is almost zero, and it is essentially not affected by the SSI effect and soil types. However, under the out-of-plane wind and ice loads, the global failure probability of CTTILSs-SSI is higher than that of the fixed base system, and the global failure probability of CTTILSs-SSI increases as the soil stiffness decreases. Accordingly, it may be more reasonable to consider the SSI effect into the global reliability analysis of TTILSs subjected to ice and out-of-plane wind loads, particularly when the soil is soft.

The lateral impact behaviour of concrete-filled steel tubular flange girders (CFSTFGs) with local corrosion was investigated in this study. Lateral impact tests on 18 girders were completed, and the effects of the local corrosion degree, impact height, impact number, and specimen type were considered. The damage development, failure modes, impact force, midspan deflection, reaction force, and energy absorption were analyzed. The tested results indicated that the CFSTFGs mainly experienced overall bending deformation under lateral impact, while the girder with corroded web and flange had the lowest impact resistance. As the local corrosion degree increases, the plateau impact force gradually reduces while the maximum deflection increases of girders. The peak and plateau stages of the impact force become more noticeable as the impact number increases. Then, a finite element analysis (FEA) model of CFSTFGs with local corrosion under lateral impact was developed and calibrated. The full-range analysis of impact responses of a typical CFSTFG with local corrosion was carried out, including the impact process, bending moment development, force balance, and plastic deformation energy. The key parameters affecting the impact force, midspan deflection, and dynamic bending moment of CFSTFGs were also discussed. The simplified method was finally proposed to calculate the dynamic flexural capacity of CFSTFGs with local corrosion under lateral impact.

This study explores the load-deformation relations of concrete-filled double-skin steel tubular (CFDST) columns under axial compression, utilizing the machine learning predictive techniques. A comprehensive database of the circular CFDST columns was assembled from previous literature, including their load-deformation relationship data. Criteria were established to classify the types of load-deformation curves. Six machine learning algorithms were employed to predict the yield point, ultimate strength point and failure point, thereby reconstructing the load-strain curve for CFDST columns. Various performance metrics were used to assess the accuracy of these machine learning models. The experimental results were compared and analysed across different models. Furthermore, the predicted ultimate compressive strengths were compared and analysed with the results obtained from the application of current codes of practice. The findings revealed that the machine learning models exhibited superior performance in predicting the load-strain relations of CFDST columns, and the support vector regression (SVR) model exhibited a superior fit to the actual experimental results.

This paper aims to investigate the seismic shear behavior of the composite joint consisting of partially-encased composite (PEC) column and steel beam. Two specimens, including one PEC column (strong-axis direction) to steel beam joint and another PEC column (weak-axis direction) to steel beam joint, were tested under constant axially compressive load on the column and cyclic load at the top of column. The designs and fabrications of specimens were described in detail. The failure modes of these two type joints were obtained, their joint panel zone were all failed by shear, and several indexes that could reflect the seismic performance of the composite joint, such as the hysteretic curves, the ductility, the stiffness degradation, and the energy dissipation capacity were analyzed. It was founded that the ductility coefficients of the strong-axis joint specimen and weak-axis joint specimen are both close to 2.0, the shear failure of these joints should be avoided in seismic region. The T/CECS719-2020 shear strength models produced conservative predictions of the shear bearing capacity of these joints. The predicted shear bearing capacity of strong-axis joint is 60.12% of the experimental value, and the predicted value of weak-axis joint is only 32.46% of the experimental value. The prediction of the shear bearing capacity of weak-axis joint should consider the role of the column flanges and the concrete not wrapped by connecting plates in shear resistance.

Void growth plays a significant role in ductile fracture prediction of aluminum. This study proposes 2 deep learning models to address this issue. For voids that retain their ellipsoidal characteristics during growth, the ellipsoidal void Semiaxes Long Short-Term Memory (SLSTM) method is proposed, using the 3 principal features of the ellipsoid to represent the voids. For voids that undergo arbitrary shape changes during growth, an innovative deep learning method called Voronoi tessellation-assisted LSTM (VLSTM) is proposed. This method uses the Voronoi algorithm to standardize data features and employs Principal Component Analysis (PCA) to perform data compression before neural network training. This new method combines the Voronoi algorithm, LSTM neural networks, and PCA algorithms, and is termed as VLSTM-PCA. In this study the deep learning-based SLSTM surrogate models and VLSTM-PCA surrogate models run approximately 514 and 537 times faster than ABAQUS finite element simulations, significantly enhancing efficiency while maintaining high prediction accuracy. Finally, growth patterns of ellipsoidal voids under different stress triaxialities are analyzed.

Beam-to-column connections with vertical oblique angles are being used in construction; however, such connections have not been adequately researched to confirm their seismic performance. This study investigated the cyclic behavior of beam-to-column connections with vertical oblique angles, offering critical insights through theoretical analysis and full-scale experiments. Mechanical interactions at the beam ends were initially analyzed to predict failure sections and strengths. Full-scale experiments under cyclic loading conditions were conducted for verifying these predictions. The experimental results highlighted the hysteretic behavior, and the failure modes of the beam ends showed that vertical oblique angles have a negligible effect on the hysteretic behavior of the beam-to-column connections. Moreover, the plastic deformation capacity and strain distribution of the beam ends vary with regard to vertical oblique angles, which is consistent with the theoretical predictions. Finite element analysis also confirmed the experimental results, demonstrating the effectiveness of proposed method for predicting the structural performance of the connections.