Experimental evaluation of deconstructable external composite joints with stiffened end-plates and bolted shear connectors under cyclic loading

Abstract

This study presents an innovative approach for semi-rigid deconstructable external beam-to-column composite joints (DECJs) under cyclic loading featuring central reinforcement bars, stiffened extended end-plate, bolted shear connectors, and precast geopolymer concrete slabs. The study aimed to enhance the assembly, deconstructability, moment symmetry, and sustainability of DECJs by inserting central reinforcement bars through column flanges and improving the moment symmetry by using stiffened end plates. Six full-scale steel-concrete composite joints were designed and tested to assess their seismic performance, focusing on stiffness, moment-rotation responses, ductility, slip between the precast concrete slab and steel beam, strength degradation, energy dissipation, and failure modes. The variables include the stiffened and unstiffened extended end-plate, the diameter of central reinforcement bars, and the diameter and Grade of the bolted shear connectors. The experimental results showed that the use of bolt shear connectors, central reinforcement bars, and stiffened end plates in DECJs significantly enhances the rotation capacity, approximately 1.7 to 3 times higher than that provided by Eurocode 8 and FEMA-350 standards. The integration of gusset plates into the extended endplate configuration significantly improves the seismic performance of the DECJ, particularly under sagging moments, enhances moment symmetry, and reduces the risk of premature failure of the end plate. Moreover, it provides joint demountability and reduces the carbon footprint of the system. Finally, a predictive equation is proposed to determine the plastic moment capacities of DECJs under cyclic loading. © 2026 Elsevier Ltd