Numerical calibration of bond law for GFRP bars embedded in steel fibre-reinforced self-compacting concrete

Abstract

An experimental program was carried out at the Laboratory of Structural Division of the Civil Engineering Department of the University of Minho (LEST-UM) to investigate the bond behaviour of glass fibre reinforced polymer (GFRP) bars embedded in steel fibre reinforced self-compacting concrete (SFRSCC) for the development of an innovative structural system. Thirty-six pull-out-bending tests were executed to assess the influence of the bond length, concrete cover, bar diameter and surface treatment on the bond of GFRP bars embedded in SFRSCC. This paper reports the results of a numerical study aiming to identify an accurate GFRP–SFRSCC bond–slip law. Thus, the above mentioned pullout bending tests were simulated by using a nonlinear finite element (FE) constitutive model available in FEMIX, a FEM based computer program. The bond–slip relationship adopted for modelling the FE interface that simulates the interaction between bar and concrete is the key nonlinear aspect considered in the FE analyses, but the nonlinear behaviour of SFRSCC due to crack initiation and propagation was also simulated. The evaluation of the values of the relevant parameters defining such a bond–slip relationship was executed by fitting the force versus loaded end slip responses recorded in the experimental tests. Finally, correlations are proposed between the parameters identifying the bond–slip relationship and the relevant geometric and mechanical properties of the tested specimens

Experimental investigation of bond behaviour of two common GFRP bar types in high – Strength concrete

“…The slip corresponding to the maximum bond stress obtained from GFRP (type A) reinforced specimens is higher than that obtained from GFRP (type B) reinforced specimens, indicating that the amount of slip is influenced by the surface treatment. The effect of surface properties on the slip was also confirmed by Lee et al[4] and Pepe et al[24]. All specimens reinforced with steel bars exhibited high initial stiffness without a slip when chemical adhesion was dominated.…”

Neutral axis depth and moment redistribution in FRP and steel reinforced concrete continuous beams

“…The bond-slip effect for FRP reinforcement may have some influence on the ultimate load and rotation capacity. A more accurate analysis of FRP-reinforced beams should be based on a reasonable bond-slip law for FRP reinforcement [20,21]. For the present study, however, the approximation of perfect bond between FRP reinforcement and concrete is acceptable, since the development of both the neutral axis depth and moment redistribution for FRP-reinforced concrete beams tends to stabilize after reaching a level far below the ultimate load and rotation capacity, as will be indicated later.…”

Bond characteristics of straight- and headed-end, ribbed-surface, GFRP bars embedded in high-strength concrete

“…Cosenza et al [22] investigated the bond stress-slip behavior of FRP bars and proposed a modification to the bond prediction evaluation (BPE) model to account for the FRP characteristics. Diverse efforts were dedicated in order to develop more refined bond-slip model to cover various surface treatments, shear and axial stiffness, bar diameter, bond length, confinement applied to the FRP bars due to concrete shrinkage or external loads, and swelling of FRP bars due to temperature variation and moisture absorption [32][33][34][35][36][37][38][39][40][41][42].…”