Effects of Strain Rate on Reinforced Concrete Structure under Seismic Loading

The effects of strain rate on the reinforced concrete structure under seismic loading are studied in this paper. Firstly, the strain-rate effects of reinforcing steel with the grades HPB235, HRB335 and HRB400 were investigated using the MTS electro-hydraulic servo-controlled testing system at the strain rate (2.5 x 10(-4)/s similar to 0.1/s) that might be experienced during earthquakes. Based on the test results, dynamic increasing factors (DIF) which are functions of strain rate and quasi-static yielding strength of reinforcing steel are gotten. Then, two kinds of expressions on the effects of strain rate on concrete are chosen for these analyses. Finally, considering the strain-rate effects of concrete and steel, the three-dimensional finite element model of reinforced concrete frame structure subjected to three-component earthquake inputs is established based on a practical project, in which three peak levels of ground accelerations are taken into account. Using the nonlinear time history analytical method, the distribution of strain rate and the effects of strain rate on the base shear force, bending moment and top displacement of structure are studied. These results may provide a reference for reinforced concrete frame structure in seismic design.