Study on the static pushover of frame structure with staircase

A large number of staircase damages in reinforced concrete frame structures has attracted much concern during 2008 Wenchuan Earthquake. In order to fully investigate the interaction mechanism and failure modes between the staircase components and surrounding frame members, a static monotonic test on a one story two bay RC frame structure with staircase under the lateral loading was carried out. The experimental results indicated that the distribution of internal force in staircase components under the lateral loads is significantly different from the traditional design methodology in which only gravity loads are involved. The staircase can noticeably increase the lateral stiffness of overall structure but introduce the torsion effect as well. In general, the staircase experienced the damage earlier and much severe than the main structure. It was concluded that the flights are under the combined action termed the axial force, biaxial bending moment and biaxial shear force. The joint of flight and landing beam may become one of the most attacked parts by lateral force. The mid-span of landing beam is suffered the unexpected higher negative moment. The punching failure may occurred at the mid-span of platform and landing beam due to the K-braced effect from the flights.