Blast and Impact Loading and Response of Structures
Full Session with Abstracts
Connections between precast concrete components must be economical and constructible, and they must also be robust: able to redistribute gravity loads from damaged to undamaged portions of the structure during extreme loading events. Testing of two precast concrete moment-frame subassemblies under an interior column removal scenario by NIST in 2015 revealed vulnerabilities in the welded link plate connections arising from (a) localized bending of anchorage bars due to eccentricity in the tensile load path between components, and (b) a reduction in the ductility of the deformed bar reinforcement due to welding.
To overcome these vulnerabilities, five new alternative connections incorporating welded link plates, threaded bars, grouted bars, and bar couplers, respectively, are proposed to enhance the robustness of precast concrete frame structures. These new connections were investigated using numerical models of beam-column assemblies with the same geometry as those tested by NIST in 2015, but incorporating the alternative connections. The vertical load carrying capacities of the assemblies with the alternative connections under a sudden column loss were found to be larger than that of the assembly with tested connections, but experimental demonstration of these new connection concepts is still needed.
This presentation describes the enhanced connection concepts, their construction and their expected performance. In particular, it examines component testing of the modified welded link plate connection concept, which incorporates the minimal modifications to the tested configuration necessary to improve its performance. In this connection concept, the anchorage bars are welded in-line with the field welded link plates, the widths of the link plates are reduced, and a free length is added between the link plate welds. These modifications are meant to reduce eccentricities in the tension load path and promote plastic deformation of the link plates, which are intended to act as structural fuses. These tests will validate key aspects of the of numerical models and to help to finalize detailing of the connection concept in preparation for planned full-scale connection testing.