Experimental, analytical, and numerical studies of steel-strengthened glulam wood–PVC composite hollow members under four-point bending

This work investigated the flexural performance of glulam wood–polyvinyl chloride composite hollow members (GWPVC), fabricated by assembling individual wood–polyvinyl chloride composite (WPVC) elements with epoxy adhesive and strengthened in singly and doubly reinforced configurations. Shear bonding strength tests were conducted to confirm that the capacity satisfied standard requirements. Several strengthening materials, including carbon fiber-reinforced polymer (CFRP), low-cost glass fiber-reinforced polymer (LC-GFRP), and steel, were evaluated using the VIKOR method within a multi-criteria decision-making (MCDM) framework based on mechanical performance. Steel was identified as the most suitable strengthening material. The study highlights steel strengthening as an approach to improve the flexural performance and serviceability of GWPVC members, with predictions from analytical method with iterative technique (AMIT) that considers shear deformation effects and finite element method (FEM) simulations, validated against experimental results. Four-point bending tests showed that the ultimate load and initial bending stiffness increased by up to 220.63% and 109.22%, respectively, compared with unstrengthened specimens. Parametric results from AMIT demonstrate that flange reinforcement is more effective than web reinforcement, particularly when placed farther from the neutral axis. Strengthening also extended the serviceable span length of GWPVC members from 3.38 m to 5.27 m, confirming feasibility for residential prefabricated floor panel applications.