The use of cold-formed steel (CFS) systems has significantly increased in the past few decades, especially in the construction of low to mid-rise buildings. Compared to hot-rolled sections, CFS ...members are often more economical and efficient due to their low weight, ease and speed of construction and greater flexibility in manufacture. In most conventional CFS buildings, diagonally strap-braced stud walls provide the primary lateral force-resisting system. This study aimed to develop a better understanding of the structural behaviour of CFS strap-braced stud wall systems under seismic loading. To achieve this, a detailed numerical model was developed, accounting for material nonlinearity, initial geometric imperfections, nonlinear behaviour of the connections and secondary moments due to P-Δ effects. This model was validated against previous experimental results on full-scale wall systems. A comprehensive parametric study was then conducted using the validated model to investigate the effect of key design parameters, namely the number of studs, the presence and intensity of vertical loading, the thickness of the structural elements and the steel grade of the straps, on the seismic performance of the system. The lateral load-resisting capacity, deformation capacity, ductility and energy dissipation under lateral loading were investigated and are here discussed. An efficiency index was proposed for each of these variables, allowing design solutions to be rated in terms of their ability to improve the material efficiency of the system, and design recommendations were derived for performance-based design.
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•Performance of CFS strap-braced walls investigated under seismic & vertical loads.•Extensive numerical investigation conducted using experimentally validated models.•Effect of key design parameters on strength, ductility & energy dissipation investigated.•The vertical loading had a significant adverse effect on all performance parameters.•Increasing the strap thickness and steel grade led to the highest Efficiency Index.
This paper presents the results of an experimental campaign investigating the seismic behaviour of full-size cross laminated timber (CLT) wall systems with sound-insulated shear-tension angle ...brackets. The main aim of the study was to investigate the influence of more and less flexible soundproofing bedding under the CLT wall. The paper shows a comparison of lateral load-bearing capacity, displacement capacity, ductility and stiffness obtained from racking tests on uninsulated specimens and specimens with various types of bedding insulation and levels of vertical load. Moreover, an analytical procedure to estimate the lateral load-displacement response of CLT walls with bedding insulation is proposed. This model is verified by direct comparison to the experimentally determined lateral load-displacement backbone curves. The results show that the elastomeric bedding does not have a significant effect on the bearing capacity of the wall system tested, but it reduces the stiffness and increases the displacement capacity. Due to the large decrease in stiffness, the insulation causes an overall reduction in ductility. The analytical estimation proposed was able to capture the reduction in lateral stiffness and adequately predict the load-bearing capacity.
•Monotonic and cyclic shear tests of walls, analytical model.•The insulation does not significantly influence the lateral load-bearing capacity.•The insulation reduces the lateral stiffness of the wall and overall ductility.•High vertical load can cause irreversible deformation of the CLT slab and insulation.•The analytical model adequately predicted the lateral load displacement response.
To investigate the seismic behavior of spiral stirrup-confined square concrete-filled steel tubular (SS-CFST) columns, ten square CFST columns, including eight SS-CFST columns and two ordinary CFST ...columns were experimentally studied through the cyclic loading tests. The critical test variables included the axial load ratio, spiral pitch, and longitudinal reinforcement ratio. First, the seismic behavior of the SS-CFST columns was herein discussed and clarified based on the failure modes, hysteretic response, skeleton curves, load-bearing capacity, strength and stiffness degradation, ductility and energy dissipation. Then, a total of 53 full-scale finite element (FE) models were established for parameter analysis of SS-CFST columns. The experimental and numerical results showed that the expansion deformation, necking and fracture of spiral stirrup were not formed when the SS-CFST columns were damaged, but the confinement effect effectively reduced the concrete fragmentation, alleviated the buckling of steel tube and longitudinal rebar, and limited the expansion of internal cracks. In the range of n=0.20–0.50, the ductility of SS-CFST columns significantly decreased with an increase in the axial load ratio, despite the stable bearing capacity and good energy dissipation of the columns. Moreover, unlike SS-CFST columns with high axial load ratio, spiral stirrup can only slightly improve the load-bearing capacity of SS-CFST columns with small axial load ratio (nt≤0.35). Compared with ordinary CFST columns, the strength degradation, ductility, collapse resistance, and energy dissipation of SS-CFST columns were significantly improved except for lateral stiffness, and the ultimate drift ratio of all SS-CFST columns in the test was greater than 3.00%. Furthermore, for SS-CFST columns, increasing the longitudinal reinforcement ratio can improve the lateral load-bearing capacity and stiffness. Finally, the formulas established in this paper can be adopted to assess the lateral load-bearing capacity of SS-CFST columns.
•Experimental and numerical investigations were conducted on the seismic behavior of SS-CFST columns under cyclic loading.•The failure modes and the development of plastic hinge region of the SS-CFST and CFST columns were compared.•Spiral stirrup effectively limited the expansion of internal cracks, and alleviated the buckling of steel tube.•A full-scale FE model was developed to carry out the working mechanism and parametric analysis.•Formulas for calculating the lateral load-bearing capacity of SS-CFST columns were established.
•Bearing capacity of laterally loaded piles buried in cohesive soils under critical undrained conditions was considered in this contribution.•An evolutionary data mining technique was implemented to ...develop a model based on a comprehensive field measurements database.•Results were compared with outcomes of two empirical models and an artificial neural network-based model from literature.•The presented model was shown to be very robust and with strong capabilities in capturing and reproducing load bearing capacity behaviour of piles under lateral loading.
The complex behaviour of fine-grained materials in relation with structural elements has received noticeable attention from geotechnical engineers and designers in recent decades. In this research work an evolutionary approach is presented to create a structured polynomial model for predicting the undrained lateral load bearing capacity of piles. The proposed evolutionary polynomial regression (EPR) technique is an evolutionary data mining methodology that generates a transparent and structured representation of the behaviour of a system directly from raw data. It can operate on large quantities of data in order to capture nonlinear and complex relationships between contributing variables. The developed model allows the user to gain a clear insight into the behaviour of the system. Field measurement data from literature was used to develop the proposed EPR model. Comparison of the proposed model predictions with the results from two empirical models currently being implemented in design works, a neural network-based model from literature and also the field data shows that the EPR model is capable of capturing, predicting and generalizing predictions to unseen data cases, for lateral load bearing capacity of piles with very high accuracy. A sensitivity analysis was conducted to evaluate the effect of individual contributing parameters and their contribution to the predictions made by the proposed model. The merits and advantages of the proposed methodology are also discussed.
The seismic performance of the innovative steel-reinforced reactive powder concrete (SRRPC) composite columns was evaluated via the cyclic experiments considering the steel shape ratio, axial ...compression ratio and the stirrup ratio. The SRRPC columns generally exhibited appreciable seismic behavior, great crack-resistance and excellent anti-spalling property. It was found that increasing the steel shape ratio from 4.20% to 5.35% can significantly enhance the ductility and the energy dissipation capacity. As the axial compression ratio increased from 0.1 to 0.3, the peak lateral load increased but the ductility significantly decreased. Increasing the stirrup ratio from 1.57% to 2.52% was not helpful for seismic performance in the pre-peak zone but was beneficial to the strength and ductility in the post-peak zone. Moreover, the average strength loss of the SRRPC columns with low axial compression ratio at the 4.5% drift ratio was less than 12.5%, satisfying the modern seismic drift criteria. Two coefficients, βtu and k, for predicting the equivalent tensile strength were identified and compared to the suggested values from the specifications JGJ/T 465-2019 and T/CCPA 35-2022, respectively. An analytical model was successfully developed to predict the lateral load-bearing capacity. Good agreements were found between the experimental and analytical results.
•Performance of log-house construction systems under lateral loading.•In-plane behaviour of Standard half-lapped joint and Tirolerschloss joint systems.•Monotonic and cyclic testing of single corner ...joints and full-scale wall specimens.•Proposal of a simplified rheological model.
The paper presents the outcome of a research on the in-plane behaviour of two different log house construction systems when subjected to lateral loading. Such systems, identified by the way the logs are joined together are: the Standard half lapped joint (ST) system and Tirolerschloss joint (TR) system. Two stages of experimental testing were carried out at the laboratory of the University of Trento. In the first stage the focus was on the corner joints and on a possible wall reinforcement system (22 monotonic and 5 cyclic tests were performed). In the second stage full-scale wall specimens were tested (5 monotonic and 5 cyclic tests). Several layouts were investigated: 4.2m long walls with thin (TR and ST) or thick logs (ST); “short” walls (2.75m long); walls with openings.
The test results highlighted some critical aspects in the in-plane behaviour of the walls. The lateral load carrying capacity of the wall appeared to be influenced by two main phenomena: friction and corner-joint interlocking. Due to mounting tolerance a large displacement was required to fully engage the corner joint resistance. A large horizontal plateau characterized the post friction part of the load displacement curve (wide plateau) both for ultimate limit state (ULS) and serviceability limit state (SLS). The cyclic tests showed a high level of energy dissipation that was attributed to the “inter-log friction”. In order to have a better insight into such aspects, a simplified rheological/analytical model was developed by using the experimental data as input parameters. A good agreement between the model output and the experimental behaviour was obtained.
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