Investigation Of Ultra-High Performance Concrete For Precast Decked Bulb-Tee Bridgegirder Connections

Abstract

In recent decades, many state departments of transportation have chosen ultra-high performance concrete (UHPC) as a proper solution for several difficulties of the precast bridge system. The use of steel fiber reinforcement contributes significantly to the various advantages that UHPC material provides in comparison to conventional concrete. The fundamental goal of this research study is to develop and improve the transverse joint design (shear key) that provides satisfactory implementation in a connection area between two adjacent precast decked bulb-tee bridge girders using UHPC as a grout material. The design and building of fully simulated connected decks were completed to assess the strength and performance of this particular transverse joint using UHPC material under ultimate monotonic loading and cyclic loading (fatigue) as an experimental investigation. The focus of these experimental tests was on the bond between the precast concrete and UHPC material, cracking behavior under low stresses of cyclic loading, cracking and failure behavior under high stresses of cyclic loading, and monotonic ultimate loading behavior. Furthermore, a finite element analysis was performed for validation and clarification of the effect of the deck thickness on the connection joint's strength. Meanwhile, other studies, such as the interfacial bond strength between UHPC and conventional concrete and the bond behavior between the reinforcing rebars and the concrete, were executed to participate in investigating the performance and behavior of connection joints between the decks of bulb-tee bridge girders. These experiments and the subsequent analysis showed that the decked bulb-tee girder system using UHPC as grout material provided higher strength than the cast-in-place entire deck by approximately 44 percent in terms of the bending moment capacity. In this study, the particular transverse joint design and noncontact lap-splice of the connection joint exhibit acceptable behavior where the failure mode of all simulated decks was the conventional concrete crushing. The groove and intentionally roughened surfaces of the precast concrete members before casting the grout material (UHPC) show great improvement when they increase the bond strength compared to the smooth surface by approximately 73% and 77%, respectively. The form and content of this abstract are approved. I recommend its publication. Approved: Chengyu Li