Shake Table Testing of Bidirectional Ductile Diagraphs with Buckling‐Restrained Braces in V-shaped configuration

Abstract

The Bidirectional Ductile Diaphragm concept relies on Buckling Restrained Braces (BRBs) used at ends of spans in common multi‐span bridges to provide seismic resilient damage‐free bridges at low cost, while minimizing displacement demands to levels that can be easily accommodated by conventional expansions joints. This paper reports on the results of a shake-table testing program of Bidirectional Ductile Diaphragms designed with Buckling Restrained Braces (BRBs) deployed in a V-shaped layout. A single span taken from a scaled straight bridge with no skew, simply supported on slider bearings, and BRBs end connection details was subjected to: (1) earthquakes scaled to match the design level; (2) BRB deformation demands corresponding to 75 years of cycles of bridge thermal expansions, and: (3) earthquake scaled to levels exceeding the design level such as to bring the BRB to fracture upon repeated cycles of large inelastic deformations at extreme ductility demands. Results demonstrate that bridges using the bidirectional ductile end diaphragm concept with BRBs in a V-shaped configuration can develop a stable hysteretic response, with inelastic deformations concentrated in the BRBs. These bridges would experience no loss of functionality following an earthquake, resulting in fully resilient bridges that remain in service throughout and after the earthquake.