UHPC Connection Details for Simple for Dead Load and Continuous for Live Load Steel Bridges in Nonseismic Areas

A simple for dead load and continuous for live load (SDCL) steel bridge system offers an accelerated construction solution for steel bridges. Currently, the available details for this system consist of a girder-end detail and a cast-in-place normal strength concrete (NSC) diaphragm with tight tolerances. This paper presents a study on developing a continuity detail SDCL system using ultrahigh-performance concrete (UHPC) as the diaphragm to simplify construction, improve durability, and increase tolerances. The study involved calibrating a coupled damage plasticity microplane model for UHPC and validating the material models using experimental data on similar continuity details with NSC diaphragms and a large-scale UHPC specimen. The validated models were used in a parametric study to develop a simplified connection detail utilizing UHPC. Compared to the conventional SDCL detail using NSC, the UHPC diaphragm can simplify girder-end details, eliminate the need for continuity of bottom flanges, and subsequently increase construction tolerances. In this paper, the effect of parameters like the gap between girders and the seat height of girders is studied. The diaphragm can be partially cast with UHPC, while the remaining portions can be constructed with the NSC pier. Unlike the NSC diaphragm, the UHPC portion does not require additional reinforcing bars. Implementation of this developed detail could improve the on-site construction time, durability, and constructability of SDCL steel bridge systems.