An alternative design for deconstructable external semi-rigid composite joints with precast geopolymer concrete slabs: Numerical study

Abstract

This study offers a 3D finite element modeling (FEM) and parametric analysis of a novel extended endplate beam-to-column semi-rigid deconstructable external composite joint (DECJ) under cyclic loading. This innovative DECJ is created by connecting the precast geopolymer concrete slab to the top flange of a steel beam using bolted shear connectors, and inserting threaded central reinforcing bars into the column flanges to enhance the demountability of the entire system. The FEM was developed using ABAQUS software and verified against the experimental study results to analyze the structural behavior and failure modes of the proposed DECJ system. The study investigates the effect of various parameters, including the diameter of bolted shear connectors, the degree of shear connection, the ratio of central reinforcing bars, the thickness of the endplate, the thickness and strength of the geopolymer concrete slab, and the bolt diameters of the connection zone. The findings suggest that to prevent the failure of bolted shear connectors, the optimal shear connection degree of approximately 73 %–90 % and the concrete slab thickness of 80-120 mm should be maintained. Additionally, the central reinforcing bar ratio is preferred to be around 0.98 % to avoid the failure of shear connectors and reinforcing bars. Furthermore, the ratio of endplate thickness to connection zone bolt diameter should be between 0.64 and 0.82 to reduce the fracture risks of connection zone bolts. Finally, a new predictive equation is proposed to determine the plastic moment capacities of DECJs with precast concrete slabs, demountable bolted shear connectors, and demountable central reinforcing bars under cyclic loading. © 2024