Cyclic In-Plane Shear of Concrete Masonry Walls Strengthened by FRP Laminates

Abstract

Synopsis: Cyclic in-plane shear tests were conducted on six full-scale walls built from reinforced concrete masonry units and strengthened by unidirectional composite laminates. Carbon/epoxy, E-glass/epoxy and pre-cured carbon/epoxy strips were placed on one or both sides of the walls. Each wall sample was loaded with a constant axial load simulating the gravity load, and incremental cyclic lateral shear loads were applied in accordance with the Acceptance Criteria (AC-125) of the International Code Council Evaluation Services (ICC-ES 2003). Displacements, strains and loads were continuously monitored and recorded during all tests. Evaluations of the observed strength and ductility enhancements of the strengthened wall samples are made and limitations of such retrofit methods are highlighted for design purposes. Results obtained from current tests indicated that the limit-state parameter influencing strength gain of the FRP retrofitted walls was the weak compressive strength of the masonry units, especially at the wall toe where high compression stresses exist. Despite such a premature failure caused by localized compression damage of the masonry at the wall toe, notable improvement in their behavior was achieved by applying the FRP laminates to either one or two sides of the walls. However, it should be cautioned that available theoretical models may significantly overestimate the shear enhancement in the FRP strengthened walls, if other limiting failure modes are not considered.