New Connections for Enhancing Robustness of Precast Concrete Frame Structures
Travis E. Thonstad, Yihai Bao, Jonathan M. Weigand, Joseph A. Main, Hai S. Lew
A recent experimental and computational study of two precast concrete moment-frame assemblies under a column removal scenario revealed vulnerabilities in the moment connections arising from (a) local bending of reinforcing bars due eccentricity in the tensile load path between components and (b) reduction in the ductility of reinforcing bars due to welding. To overcome these issues, three new alternative connections, which incorporate welded link plates, threaded bars, and grouted bars, respectively, are proposed to enhance the robustness of precast concrete frame structures. Computational analyses were conducted for one of the tested assemblies and for geometrically identical assemblies that incorporated the alternative connection details. The peak vertical load capacity of the assembly with the proposed link plate connections was 78 % larger than that of the tested assembly, while the capacity of the assembly with the proposed threaded bar connections was 124 % larger. The corresponding vertical displacements were 194 % and 232 % larger, respectively. Computational analyses of the proposed grouted bar connections are underway, but similar connections have performed well in previous testing under reversed cyclic loading. This paper describes the three proposed connections concepts, presents results from modeling and outlines plans for component and full-scale connection testing.
2018 PCI Convention and National Bridge Conference