Impact Factors of Curved Steel Multibox Girder Bridges

A method for estimating dynamic loading of steel multibox girder bridges caused by moving vehicles, based on an extensive parameter analysis of 216 multibox girder bridges, was developed. The curved multibox 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 AASHTO specifications. Truck parameters include the body, suspensions, and tires. The bridge deck surface is assumed to be classed as good and is simulated with 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, whereas moment, shear, and deflection impact factors are normally less than those of corresponding straight box girder bridges because of restricted vehicle speed on curved bridges. The proposed simplified impact equations are appropriate for the design of curved steel box girder bridges.