Dynamic Load Allowances Corresponding to Different Responses in Various Sections of Highway Bridges to Moving Vehicular Loads

Dynamic load allowance (DLA) is an important index used in design and evaluation of dynamic performance of highway bridges to moving vehicular loads. In many codes, DLAs of different responses in various sections are not distinguished. To facilitate a rational design and objective evaluation, the quantitative relationships of DLAs corresponding to different responses in various sections are systematically studied using both theoretical derivation and numerical simulation. According to results of theoretical derivation, for simply supported girder bridges, DLA of deflection is almost 20% higher than that of bending moment in the mid-span section. According to results of numerical simulation, for continuous girder bridges, DLA of negative (upward) deflection is 20% higher than that of positive deflection, and DLA of negative bending moment is 40% higher than that of positive bending moment in critical cases. These significant differences cannot be ignored. Finally, the contributions of high modes to different dynamic responses in various sections are investigated. Based on the recommended approach to considering these differences, the dynamic performance of bridge can be designed and evaluated in a simple yet rotational way.