Numerical-parametric analysis of debonding phenomena in frcm-strengthened masonry elements

Abstract

The application of composite materials as structural strengthening requires the use of special adhesives. The choice of the adhesive depends on several factors, one in particular is related to the characteristics of the support (concrete, masonry or wood). There are many types of natural and synthetic adhesives: the most suitable adhesives for composite materials are based on epoxy resin; mortar-based adhesive are currently the topic of several researches in order to ensure sustainability and to use renewable technologies also in the field of civil engineering. The aim of this paper is to providing a contribution regarding numerical study of adhesion problems of FRCM (Fiber Reinforced Cementitious Matrix) strengthening system. Using software based on Finite Element Method (FEM), single-lap shear bond tests have been performed implementing bond-slip laws available for masonry supports and inorganic matrix systems. The numerical model used in the simulations includes two types of reinforcements: PBO-FRCM and FLAX-FRCM, applied on masonry support. FRCM (cement-based composites) are nowadays widely used in the reinforcement of existing structures; unfortunately, the guidelines for the qualification of FRCM systems are not yet operational, as there are no design criteria available, if not for standard applications. Consequently, of this, numerical analyses have been carried out considering debonding law provided by the Guidelines CNR-DT 200 R1/2013; different parametric analyses have been allowed in order to compare computational and experimental results with Guidelines predictions. For the purpose of the work, the parameters analyzed were the bond length, the bilinear bond strength-slip and the bond interface between reinforcement-support and reinforcing fiber-matrix. In the end, all the results highlighted the different debonding mechanisms observed during the experimental analyzes, both for the reinforcement system PBO-FRCM and Flax-FRCM applied to masonry support, mainly due to the loss of adhesion.