Finite element model to predict structural response of predamaged RC beams reinforced by toughness-improved UHPC under unloading status

Abstract

This paper simulates the structural response of strengthened predamaged reinforced concrete (RC) beams with reinforced ultrahigh performance concrete (UHPC) layer using finite element (FE) analysis. The FE models simulate the whole strengthening procedures for the predamaged RC beams by using UHPC to replicate the actual test conditions. A ‘tracking and positioning elements and nodes’ technology is applied for UHPC elements when the strengthening UHPC layer is activated. Concrete damaged plasticity (CDP) model is used for normal strength concrete and UHPC. The nonlinear behavior of reinforcing bars is taken into account. A newly developed interfacial model for the UHPC-RC interface is included in the FE model. The FE models are calibrated and validated by comparison with the experimental results. Load-deflection curves, characteristic loads, and damage patterns extracted from the FE simulation agree well with the experimental results. Finally, a parametric study is conducted to investigate the effect of height of the UHPC layer, height of the RC layer (size effect), and reinforcement ratio inside the UHPC layer on the flexural response of the strengthened beam with pre-damage in the RC beam. This study might provide a reference for future design and construction of predamaged RC beams reinforced by UHPC layer, to extend their service life and reduce maintenance costs.