An alternative modeling approach to incorporate bond-slip effects in fiber-based elements

Abstract

Fiber-based elements can provide accurate estimates of the global and local inelastic response of RC members subjected to reversed cyclic loads. However, fiber-based elements per se do not account for the localized deformations that arise from strain penetration or bond-slip effects at the member ends. To account for bond-slip effects, some researchers have suggested the use of modified properties for the steel reinforcement fibers, or that a zero-length element be attached at the element ends. In this study, a modified modeling procedure is proposed to include anchorage-slip effects in reinforced concrete frame members modeled with fiber-based beam-column elements. The proposed modeling approach is based on local bond-slip laws that can be implemented in general-purpose fiber-element software, and it differs from existing approaches in that it does not require the use of a zero-length element (though it could be used), and that it can be used with any local bond-slip relationship representative of a variety of bar embedment conditions. As such, the model can be used to simulate the effects of bond-slip of short or long embedment lengths in confined or unconfined concrete. The proposed modeling procedure is validated by comparing the calculated response with experimental data from four independent investigations. The test data included three columns and two beam specimens with various confinement and reinforcement configurations and included members reinforced with conventional and high-strength steel reinforcement. The results from the analyses show that the proposed modeling procedure provides a very good estimate of both the global and the local responses (anchorage-slip rotation) of the specimens.