Articles
Composite beams consisting of precast concrete slabs and steel beams connected by deconstructable high-strength friction-grip bolts (HSFGB) have recently attracted much research attention due to their compatibility with sustainable construction. However, studies on the behavior of these composite beams have been entirely deterministic, with no consideration for uncertainty in the governing parameters, especially for the bolted shear connector varieties. In this paper, a three-dimensional finite element model is developed to investigate the behavior of this type composite beam considering the nonlinearities of the geometry, materials, and component interfaces. Nonlinear springs with zero length are utilized to model the HSFGB shear connectors, and then the complete beam model is embedded in a Monte Carlo-based probabilistic assessment approach. The results show that the simplified spring model is reliable in predicting the behavior of composite beams while being efficient in terms of computational efficiency and time savings for conducting probabilistic analyses. The probabilistic analysis finds that Monte Carlo simulation is a useful method for identifying probabilistic trend behaviors with acceptable accuracy to quantify the effect of structural parameter uncertainties. The composite beam with a partial shear connection shows a greater variety of beam responses than the composite beam with a full shear connection. © 2025 Institution of Structural Engineers
Eccentrically braced frames (EBFs) are widely recognized as effective seismic resisting systems for buildings and other structures due to their high ductility and stiffness. The performance of EBFs heavily relies on the behaviour of the critical component known as the link, which governs the system's ductility, strength, and overall response. While the link is typically subjected to high shear force and bending moment, the significance of axial force in certain EBF configurations has received limited attention in previous studies and design codes. This research aims to investigate the effects of high axial load on the reliability and performance of EBF links using the finite element method. Experimental data is utilized to validate numerical models, ensuring the accuracy of the subsequent reliability analysis. The assessment of link reliability under high axial force is conducted within the framework of Eurocode 8 (EC8), employing the first-order reliability method (FORM). The results demonstrate that EBF links with very short lengths exhibit acceptable levels of reliability. However, as the link length increases, the target reliability index is not met. To address this challenge, a modification factor is proposed based on the Rackwitz–Fiessler iterative procedure, enabling adjustments to the link shear design. Furthermore, a sensitivity analysis is performed to evaluate the influence of random variables on the reliability analysis. © 2025 Institution of Structural Engineers
In this study, a novel method termed the Optimum Stiffness Finder (OSF) is introduced to determine the equivalent stiffness matrix for sandwich beams with lattice cores. The OSF method utilizes the Particle Swarm Optimization (PSO) algorithm to simplify the calculation of equivalent stiffness, addressing the challenges posed by the geometric complexity of lattice cores. This equivalent stiffness matrix is crucial for dynamic instability analysis, enabling the determination of dynamic instability regions that conventional finite element software does not calculate. For validation of the proposed method, the free vibration results of both three-dimensional finite element models developed in ABAQUS and OSF method are compared with results from the literature, confirming the accuracy of the finite element modeling. First, the free vibration results of three-dimensional finite element models developed in ABAQUS were compared with results from the literature, confirming the accuracy of the finite element modeling. Once validated, the ABAQUS models are used to obtain displacement values under uniform loading, which served as target data for the OSF algorithm. The OSF algorithm then optimized the stiffness matrix for Timoshenko beam theory in one-dimensional finite element analysis. The equivalent beam's vibration results are subsequently compared with those from the literature to ensure consistency and accuracy. The findings demonstrate the potential of the OSF method to streamline the dynamic stability analysis of lattice core sandwich beams, providing an efficient and accurate approach for engineering applications. © 2025 Institution of Structural Engineers
Steel and Composite Structures (15986233)56(1)pp. 49-65
The combination of precast concrete slabs and steel beams connected by deconstructable high-strength friction-grip bolts has emerged as a promising solution for sustainable construction. However, the lack of design guidelines and r egulations has restricted its widespread use. This study aims to conduct a reliability analysis to evaluate the flexural resistance factor (φ) for composite beams with HSFGB shear connectors, as the AISC Specifications incorporate the shear connector resistance factor as part of the overall resistance factor of the composite beam. To analyze the behavior of the composite beam, a three-dimensional finite element model was developed and validated. Additionally, a sensitivity analysis was performed to investigate the impact of various parameters on the flexural strength of the composite beam. The flexural resistance factor for this type of composite beam with varying degrees of connection was evaluated providing an acceptable level of safety. The variability and uncertainty in connectors were determined based on existing push-out tests using statistical analysis. A reliability study found that the reduction factor of flexural resistance for this type of composite beam is dependent on the degree of shear connection. Additionally, using the flexural resistance factor recommended for conventional composite beams with welded shear connectors in the AISC code is unconservative for deconstructable composite beams. © 2025 Techno-Press, Ltd.
Mechanics Based Design of Structures and Machines (15397742)52(2)pp. 628-649
Due to the low thickness of cold-formed steel (CFS) sections, welding of traditional studs on them is not recommended; and there is a need to use shear connectors suitable for this type of sections. In this paper, the behavior of U-shaped shear connectors as connectors compatible with CFS composite beams has been investigated, to offer practical relationships for predicting the ultimate strength of this type of connectors. Accordingly, after the development of finite element (FE) models with the ability to predict the ultimate strength of U-shaped connectors, their performance against experimental results was validated. Then, an extensive parametric study, consisting of 216 numerical samples, was accomplished to provide a reliable database. As the main and most important of this study, two methods of artificial neural networks and stepwise regression were developed, and practical formulations were proposed to predict the ultimate strength of U-shaped shear connectors in CFS composite beams. Finally, in addition to evaluating the accuracy of the proposed formulas, a comparison was made between them and the relationships proposed by AISI, AS/NZS and EC3 codes for CFS screw connections. The relationships presented in this paper can be used by practical engineers in the design process of CFS composite beams. © 2022 Taylor & Francis Group, LLC.
