Bond behaviour of FRP strengthening applied on curved masonry substrates: numerical study

Abstract

The recent experimental and numerical studies concerning the local bond behavior of Fiber Reinforced Polymer (FRP) systems externally applied on curved masonry elements clearly underline the role of the geometric curvature on the performance of FRPs. In particular, the interaction between shear stresses and tension or compression normal stresses both arising at the FRP/masonry interface influences the bond strength and, consequently, the debonding behavior of FRPs. Then, the development of reliable numerical models able to predict the bond behavior of FRPs applied on curved masonry structures necessarily requires to consider this important feature which, on the contrary, is generally neglected in the case of flat substrates.Aim of the present paper is to numerically investigate the bond behavior of FRP strengthening systems externally applied on curved masonry specimens. In particular, considering the simple spring-model approach proposed by the authors in previous research, a new constitutive law derived from the work of Thorenfeld et al. ( 1987) is here proposed by also considering the coupled behavior between shear and normal forces at the reinforcement/masonry interface. Numerical analyses are developed with reference to case studies deduced from the literature and consisting of shear-lap bond tests of curved masonry specimens characterized by different values of the geometric curvature and different strengthening configurations. The obtained results show the ability of the proposed modeling approach in capturing some effects, such as the beneficial friction effect when compression normal stresses develop at the interface level.

Advanced and Simplified Modeling Approaches for the Study of the Bond Behavior of FRP Systems on Curved Masonry Substrates

“…Regarding the interface-shear springs, a tri-linear symmetric behavior was proposed by eventually including a friction effect occurring in the de-bonding phase when compression forces arise at the reinforcement/substrate. The latter feature was indeed essential for reproducing the post-peak behavior of curved specimens strengthened at the extrados [20,21,23].…”

“…One of the approaches recently carried out by the Authors, here called spring-model, consists of a schematization of specimens strengthened by FRP throughout a 1D-model composed of springs [15,20,21]. The model directly comes from a previous similar one carried out for specimens with a flat configuration [7].…”

A Simple and Low-Cost Numerical Model for FRP-Masonry Interface Behavior

“…In such models, the problem of reinforced systems subjected to shear is typically reduced to the study of an elastic FRP strip glued on a rigid substrate by means of an inelastic interface where different softening stress-slip relationships can be adopted [12][13][14]. The existing 2D/3D numerical models generally adopt a microscale FE modelling, thus being intrinsically more complex but providing at the same time more detailed information [15][16][17][18][19]. An intermediate approach is the utilization of mono-dimensional non-linear normal and shear spring elements [20] to provide albeit in a simplified manner, but useful and reliable information on the local interaction between the stiff reinforcing strip and the brittle substrate, maintaining the computational burden quite limited.…”