Torsional effects on short-span highway bridges

The torsional effects on short-span highway bridges are investigated for two situations: post-design asymmetric bridges and nominally symmetric bridges subject to seismically induced torque. The study indicates that for post-design asymmetric bridges the presence of accidental post-design asymmetric factors significantly influences the dynamic response of bridges having a small rotational to translational frequency ratio. For nominally symmetric bridges, the seismically induced torque often triggers rotational motions, which tend to aggravate the bridge deck displacements and magnify the shear forces of the supporting columns. If necessary, this torsional effect should be considered in the seismic design of bridges.