Experimental and analytical flexural performances of reinforced concrete beams strengthened with post-tensioned near surface mounted basalt composite laminates

Near surface mounted (NSM) is a technique that improves the strengthening capacity of composite laminates. The use of a post-tensioning technique modifies the performance of the strengthening because it is active bearing loads from the very beginning. This study compares the performances of three beams: one without strengthening, one with passive NSM laminate, and a third with post-tensioned NSM laminate. The experimental approach compares the pre-cracking and post-cracking performance until failures, showing that the post-tensioned solution withstands larger loads in pre-cracking and presents less deformation in post-cracking. Moreover, post-tensioning is an effective technique that can prevent loss of stiffness even after cracking. Finally, simple analytical equations based on the plane cross-section for pre-cracking and failure analysis are proposed, showing good agreement with the experimental results.