Study of dynamic load allowance on negative bending moment zone for continuous girder bridges under natural traffic flow

Investigating the negative bending moment dynamic load allowance (NBMDLA) is crucial for characterizing dynamic response under moving loads in continuous girder bridges. This study proposes a recommended value for NBMDLA based on field test of continuous girder bridges under natural traffic flow. Firstly, strain signals in the negative bending moment zone and natural traffic flow information were collected from three continuous girder bridges. Then, NBMDLA was analyzed factors such as vehicle speed, vehicle type, and vehicle lateral driving position. Finally, a recommended NBMDLA value was proposed through statistical regression. Results indicate that NBMDLA increases significantly with rising vehicle speed. Lighter vehicles tend to result in larger NBMDLAs. Vehicle lateral driving position has a significant effect on NBMDLA, though without a clear linear trend. A recommended value of 0.3 is proposed as a design reference for new continuous girder bridges.