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This paper investigated the structural robustness of steel-framed modular buildings based on the alternative load path method using LS-DYNA. The structural responses of a reference structure were first simulated to understand typical building motion, load redistribution mechanisms and failure modes after removal of a base corner module. Based on the reference scenario, a comprehensive parametric study was then carried out to investigate the effects of structural configuration (number of modules of each floor), module posts (wall thickness and number of supporting posts) and other features (inclusion of floor slab, longitudinal wall bracing, connection stiffness and connection capacity) on the structural responses of steel modular buildings. It was found that the collapse resistance of steel modular buildings could be improved with an increase in the number of modules per floor, the number and capacity of supporting posts, higher rotational stiffness and capacity of inter-module connections, and the use of longitudinal wall bracing. Consideration of floor slabs provided a more realistic description of collapse mechanisms, due to the slab-related contact interaction and diaphragm action. Also, the structure was more vulnerable to the removal of modules (or posts) near the end corner of a building.

An innovative nodal joint system with thin-walled steel sleeve and plate is examined for development of latticed shell structures using hollow section glass fiber reinforced polymer (GFRP) members. In the proposed system, the GFRP members were connected to a steel gusset-plate space node through bolted sleeve joints (BSJs). The mechanical performance of BSJs was first examined through cantilever bending experiments. Then, the performance of the entire nodal joint system incorporating the space node was examined in bending for both in-plane and out-of-plane stiffness. Its performance was then characterized by nonlinear springs and evaluated at a structural level based on a space latticed structure configuration through finite element (FE) analysis and the resulting structural performance satisfied the ultimate limit state (ULS) and serviceability limit state (SLS) requirements as per relevant standards. A parametric study was also conducted to understand the effect of joint rotational stiffness on the overall structural performances.

This paper investigates the mechanical performance of beam-to-column connections for steel-framed building modules with RHS and SHS sections of relatively small member sizes. In the experimental program, three forms of connections are tested under static bending, including a completely welded connection (W), a bolted end plate connection (EP) and the proposed end plate–stiffener connection (ST), and the failure modes, moment–rotation behaviours and strain responses were recorded during experiments. Results show that ST connection exhibited superior connection strength, stiffness and ductility compared with the EP connection. In addition, a detailed finite element analysis was conducted to model the connection behaviours, considering bolt pretension, contact behaviours and detailed bolt geometry, showing good comparison with experiments. Furthermore, a parametric study was performed on the end plate thickness and stiffener thickness for the proposed end plate–stiffener connection. Such results finally enable a comparative study to investigate the performance of module during road transportation, highlighting the effects of connection stiffness.

This paper describes the dynamic and fatigue performances of a large-scale space frame assembled using pultruded glass fiber reinforced polymer (GFRP) composites, with reference to pedestrian bridge application. The experimental structure was assembled by circular hollow section (CHS) GFRP members with the assistance of a novel steel connection system. The results from free vibration tests were analyzed using peak-picking (PP) and stochastic subspace identification (SSI) methods to extract modal parameters, i.e. natural frequencies, damping ratios, and mode shapes. From both experimental and validated FE analysis results, the proposed space frame structure satisfied the standard requirements for pedestrian bridge application in terms of natural frequency. The torsion mode as the first order mode shape can be avoided when the contribution of a bridge deck is considered. Furthermore, the structure was examined with 2.1 million fatigue load cycles and then statically loaded up to failure. The failure load showed no decrease when compared with that of a space frame without fatigue. The structural stiffness and strain of critical compressive members measured at 0.3 million fatigue loading intervals showed no significant variations, indicating that the applied fatigue did not degrade structural components and connections.

Reliability-based design optimisation paradigm has become increasingly popular to achieve economical yet safer structural designs. However, within the iterative optimisation procedure, it is a challenging problem to simultaneously satisfy both, accuracy and computational efficiency of reliability analysis, particularly for nonlinear or large design problems. Addressing the shortcomings of the mainstream reliability estimation methods, this paper presents a new reliability-based design optimisation method that combines an analytical high-order moment-based uncertainty evaluation with an efficient response surface modelling. The proposed framework allows for the precise calculation of reliability through accurate high-order moments. The fast and accurate reliability estimation in combination with efficient sampling, in turn, reduces the total number of finite element analysis in achieving the final design. The proposed moment-based design optimisation methodology was tested on problems ranging from the design of a simple cantilever to a three-dimensional multistorey steel structure. It outperforms the mainstream methods with higher accuracy and lower computational burden especially when applied to a highly nonlinear numerical problem.

Glass-fiber-reinforced polymer (GFRP) composites with innovative sleeve joints are examined for space frame assembly. The sleeve joint connects one end of a steel tubular connector with a circular solid or hollow GFRP composites by adhesive bonding, the other end being flattened to enable easy connection with other members using mechanical bolts. Experiments were conducted to investigate the mechanical performance in tension and compression. In the tensile specimens, pull-out failure occurred between GFRP and adhesive when the bond length was relatively short, and tensile fracture of the steel tubular connector occurred when the bond length was sufficiently long. In the compact compressive specimens, yielding of the flattened steel tube occurred because of the bending moment at the fully fixed support. Global buckling failure was observed for slender compressive members. Load-bearing capacity was analytically estimated for different loading scenarios and compared well with experimental results.

The use of bolted sleeve joints has been proposed for assembling pultruded glass fiber-reinforced polymer (GFRP) tubular profiles into space lattice shell structures. Such joint configurations may introduce a semi-rigid end condition and further affect the capacity of the connecting members in compression. Three batches of specimens assembled with pultruded GFRP profiles of different lengths and bolted sleeve joints at both ends were prepared and tested under static axial compression. A detailed three-dimensional finite element model considering bolt geometry, contact behavior, bolt pretension, initial geometric imperfection, and failure criterion for fiber-reinforced polymer (FRP) composites was developed and validated with experimental results showing good comparisons. It was found that the bolted sleeve joints exhibited semi-rigid behavior and that the failure modes and the effective length factor were dependent on member slenderness. The relationship between effective length factor and member ...

This paper investigates bolted sleeve joints for connecting tubular pultruded fiber-reinforced polymer (FRP) sections in tubular structures such as space frames. In the proposed joint, FRP profile and steel connector are telescoped and then clamped by mechanical bolts. Four batches of specimens were prepared and tested under static axial loading (tension and compression). Design parameters, namely the type of fastener (ordinary bolt or blind bolt), member size, and bolt group layout, were selected and examined. During experiments, failure modes, load-displacement and load-strain relationships were recorded to evaluate the joint performance. A staggered pattern within a bolted sleeve joint had a negligible effect on the load distribution compared with a nonstaggered pattern. The study showed that the joint capacity could be optimized effectively by adjusting the joint geometry. When blind bolts are used, a compromise between ease of cavity fixing and joint performance must be noted. Finally, a simp...