Abstract
The mechanical behavior of the adhesive interface between the fiber-reinforced polymer (FRP) strip and the concrete substrate often controls the response of FRP-strengthened reinforced concrete (RC) members. Plenty of studies devoted to understanding the mechanical behavior of FRP strips glued to concrete are currently available in the scientific literature. However, they are mainly focused on the response under monotonic actions, which is certainly relevant in a wide class of practical applications. Conversely, few contributions are currently available to better understand the response of FRP-to-concrete interfaces under cyclic actions, such as those deriving from either seismic excitations or traffic loads. This paper presents a unified numerical approach to simulate both monotonic and cyclic behavior of FRP plates glued on quasi-brittle substrates like those made of concrete. Particularly, a damage-based approach is proposed to simulate the fracture behavior of FRP-to-concrete joints under loading/unloading cycling tests. The model is formulated within the general framework of Fracture Mechanics and is based on assuming that fracture at the FRP-to-concrete interface develops in (pure shear) mode II, as widely accepted in similar problems. Two alternative expressions of the bond-slip behavior are herein considered and their preliminary validation is finally proposed. The proposed results highlight the difference between the monotonic and the cyclic response; particularly, they show that the latter is characterized by a significantly lower force and displacement capacity.
Highlights
Fiber-reinforced polymer (FRP) materials recently gained popularity in a variety of retrofitting solutions aimed at upgrading structural members in existing civil engineering structures, such as concrete columns [1], wooden floor beams [2] and masonry panels [3]
As a matter of fact, the mechanical response of the adhesive interface often controls the structural performance of reinforced concrete (RC) members strengthened by externally-bonded (EB) FRP strips
Ko and Sato [14] proposed an empirical bond-slip model intended at simulating the behavior observed in a series of monotonic and cyclic tests carried out on aramid (A), carbon (C) and polyacetal (P) FRP strips glued to concrete blocks and tested in double shear
Summary
Fiber-reinforced polymer (FRP) materials recently gained popularity in a variety of retrofitting solutions aimed at upgrading structural members in existing civil engineering structures, such as concrete columns [1], wooden floor beams [2] and masonry panels [3]. Such studies, intended at investigating either the behavior of FRP-to-concrete adhesive joints or the response of EB-FRP strengthened RC beams, were generally carried out by only considering monotonic actions applied to the members under consideration. Ko and Sato [14] proposed an empirical bond-slip model intended at simulating the behavior observed in a series of monotonic and cyclic tests carried out on aramid (A), carbon (C) and polyacetal (P) FRP strips glued to concrete blocks and tested in double shear. In the authors’ best knowledge, several studies, both theoretical and experimental in nature, are already available to investigate the mechanical behavior of FRP-to-concrete adhesive joints under monotonic actions, no well-established formulation is available yet for simulating the cyclic response of such joints, being this topic only approached in few experimental studies, one of which is considered as a reference [14]. The proposal of a mechanically based approach for simulating the cyclic response and, investigating the consequences of two different assumptions for the bond-slip law are the two main novelties of this paper, which should be intended as the first step of a new research line
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