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

Abstract

This study presents an innovative approach for deconstructable external semi-rigid composite beam-to-column joints (DECJs) under cyclic loading featuring friction-grip bolted shear connectors, central reinforcing bars, and prefabricated geopolymer concrete slabs. The proposed design aimed to enhance deconstructability and sustainability by inserting central reinforcing threaded bars through column flanges, allowing for the disassembly of joint elements after their service life. Five full-scale external steel-concrete composite joints were designed and tested under cyclic loading to assess their seismic performance, focusing on failure modes, slip, moment-rotation responses, ductility, stiffness, energy dissipation, and strength degradation. The variables are the reinforcement ratio for central reinforcing bars, the diameter of bolted shear connectors, and the presence of steel fiber in geopolymer concrete (GPC) slabs. The experimental results showed that the use of bolt shear connectors, central threaded bars, and steel fiber-reinforced GPC slabs in DECJs significantly enhances the rotation capacity approximately 2–2.7 times higher than that provided by EC4. The proposed DECJ enhances the moment capacity and ductility of the joints, making them suitable for seismic applications. Moreover, it provides joint deconstructability, reduces the carbon footprint of the system, and effectively predicts the moment capacity of specimens, aligning with observed failure modes. Finally, a simple design model for estimating the moment capacity of the joints is proposed using the component-based modeling approach. © 2025 Elsevier Ltd