Seismic Performance of Reinforced-Concrete Stairways during the 2008 Wenchuan Earthquake

Abstract

A large number of stairways experienced minor to extreme damage during Wenchuan Earthquake (Ms=8.0) that shook northwestern Sichuan on May 12, 2008. A postearthquake field reconnaissance on buildings was carried out in the epicentral region. Typical stairway configurations identified in the epicenter areas and the corresponding damage experienced are discussed in this paper. Various types of seismic damage to the stairway components or the primary structures occurred because of the interaction between the stairways and the primary structural systems. The primary structures were affected by the formation of short columns or short beams and high local shear stresses in the floor diaphragms and beam-column joints of the stairwells. Stairway components were vulnerable to seismic actions where the distresses included cracking or spalling of concrete, buckling of reinforcing bars in the middle of the flights or at the stair flight-landing junction, high local stresses in the landing slab of L-shaped stairways and in the middle of landing beams, and stress concentration at the corner of Z-shaped stringer. Brittle stair enclosures and finish materials were particularly hazardous due to their falling debris.