Effect of Permanent Formwork using Ultra-High Performance Concrete onStructural Behaviour of Reinforced Concrete Beam Subjected to Bending asa Function of Reinforcement Parameter

Abstract

In order to use ultra-high performance concrete (UHPC) as a permanent formworks for a reinforced concrete (RC) slab in a construction field, the structural performance of the RC-UHPC composite beams subjected to bending are experimentally investigated. The main parameters are the rebar location and the UHPC thickness. The experimental results show that the crack patterns of the composite specimen is different compared to the reference RC specimen, because of the crack localization phenomenon of UHPC. Within the post peak state of the load-deflection relationship, the composite specimen behaves similar to the RC specimen. However, the reinforcement of deformed bars in the UHPC section shows a synergy effect on structural performance; both load and deformation capacity is significantly increased. Nevertheless, it is required to reinforce the bars in normal concrete section for preventing debonding failure as well as for retaining the load resisting capacity at the post peak state. The best structural performance of the composite specimen is found when the reinforcement ratios are the same in the both normal concrete and UHPC sections. The results of this study help to apply and design the thin UHPC panel as a permanent formwork for retrofitting existing structures.