Asynchronous Shake-Table Testing of Seismic Resilient Multispan Bridges Having Buckling Restrained Braces in Bidirectional Ductile Diaphragm

The bidirectional ductile end diaphragm concept uses energy-dissipating buckling restrained braces (BRB) as fuses located at the end of a bridge superstructure's floating spans. This system using BRBs can provide seismic resilient and damage-free bridges fully operational immediately after an earthquake. A shake-table testing program was conducted to subject a 1/2.5-scale specimen to series of ground motions. The specimen tested represents one span of a five-span bridge having BRBs connected to the abutment and the pier next to it. The purpose of these tests was to experimentally validate proposed connection details when subjected to the three-dimensional (3D) displacement histories (compared with the axis of the BRBs) that resulted from bidirectional ground motions and the fact that the connections must accommodate inclined BRB layouts. The test protocol included earthquake displacement histories that represent design demands, cycles of thermal excitations, and (to eventually make the BRBs fail) extreme motions. The testing program validated the effectiveness of the proposed concept and the ability of BRBs to sustain multiple ground motions before failure.