Experimental and computational investigation of mechanical anchors for large-scale applications of reinforced concrete with a fiber-reinforced polymer blast retrofit

Abstract

While fiber-reinforced polymer (FRP) laminates have been shown to enhance the blast resistance of reinforced concrete (RC) structural elements, a knowledge gap exists when the RC components are large, and mechanical anchors must be installed throughout the RC component to avoid delamination and debonding. The objective of this study was to investigate two different mechanical anchorage systems installed throughout RC slabs with carbon fiber-reinforced polymer (CFRP) blast retrofits. Two RC slabs with CFRP retrofits were constructed, one with an epoxy anchor and steel strap anchorage system and the other with an epoxy anchor and steel plate anchorage system. The feasibility of each mechanical anchorage system for large-scale applications was assessed with considerations from the construction process. The two specimens were experimentally subjected to explosive loadings in full-scale live blast testing, and strain, acceleration, displacement, and damage were recorded during the experiments. Finite element analysis (FEA) models for the two specimens with different anchorage systems were developed and validated utilizing the experimental results. Because different loadings were utilized in the experiments, the validated FEA models were used to compare the performance of the two specimens. For both experiments, the epoxy anchors exhibited no visible movement and failure initiated in the concrete and not at the interface of the concrete and CFRP. The FEA comparison of the two specimens with different anchorage systems showed the inbound behavior of the two specimen to have nearly identical behavior. The steel plates required significantly less effort to install on the epoxy anchors compared to the steel straps making the plate anchorage system attractive for large-scale applications of FRP retrofits to RC structural elements.