Flexural Performance of UHPC-Concrete-ECC Composite Member Reinforced with Perforated Steel Plates

A novel reinforced concrete structural member comprising ultrahigh-performance concrete (UHPC) and engineered cementitious composite (ECC) was proposed for use in underground structures, such as prefabricated utility tunnels. In this composite member, UHPC was used as the exterior (i.e., soil side) protective layer to prevent the penetration of water and corrosive agents, and ECC was used as the interior (i.e., service environment side) protective layer to improve the member's crack-control capacity and fire resistance. Ordinary concrete was filled between the UHPC and ECC layers. The composite member was reinforced with perforated steel plates to achieve strong mechanical interaction between the composite materials and to ensure structural integrity. The proposed composite was experimentally characterized as follows. The tension-stiffening effect in ECC panels with a perforated steel plate was evaluated using direct tensile tests. The flexural behavior of the reinforced UHPC-concrete-ECC members was characterized with four-point bending tests. The failure processes of the composite members were analyzed via the digital image correlation (DIC) method. Finally, a simplified theoretical method was developed to estimate the yield and ultimate load-carrying capacities of the composite member, and the estimated results showed good agreement with the test results. Overall, the proposed composite member had favorable mechanical performance and durability due to the strategic use of UHPC and ECC.