Unified Approach for Analysis of Box-Section Members under Combined Actions

Reinforced concrete (RC) structural elements with box sections are commonly used in the horizontal and vertical structures of bridges. Reinforced concrete structures in bridges have often failed under the combined forces of bending, axial load, shear, and torsion caused by wind and earthquake. It is very important to find out the failure mechanism and to give a unified failure expression of RC box sections under these combined forces. In this paper, a theoretical study and deduction of the unified failure expression on the reinforced concrete members with box sections under combined bending, shear, axial force, and torsion were carried out with a stress equilibrium assumption. The results of a theoretical analysis were compared with the experimental results of reinforced box girders under torsion, bending, and shear forces. Both the theoretical results and the test results showed a good correlation, thus demonstrating that the unified failure expression for reinforced concrete members with box sections can be used in the static calculation of such bridge members.