Impact Factors Of Curved Steel Box Girder Bridges

The dynamic loading of 28 three-span continuous single box girder bridges and 216 three-span continuous multi-box-girder bridges, with span lengths ranging from 22.83-30.48-22.86 m to 64.01-85.34-60.01 m (75-100-75 ft to 210-218-210 ft), due to vehicles moving across rough bridge decks is analyzed. The curved single box girder bridges are divided into a number of thin-walled beam elements. The curved multi-box-girder bridge is modeled as a curved grillage system. The analytical vehicle, simulated as a nonlinear vehicle model with 11 degrees of freedom, is the HL-93 truck as described in the American Association of State Highway and Transportation Officials (AASHTO) specifications. Truck parameters include the body, suspensions, and tires. The bridge deck surface is assumed to be classed “good” and is simulated using a stochastic process (power spectral density function). The bridge-vehicle interaction model is validated by field test results from two curved steel box bridges. The analytical results show that the torsion impact factors for curved box girder bridges can be relatively high, while moment, shear and deflection impact factors are normally less than those of corresponding straight box girder bridges due to restricted vehicle speed on curved bridges. The proposed simplified impact equations are appropriate for the design of both curved single box and multi-box box girder bridges.