Computational assessment of the seismic behavior of steel stairs

Stairs are an essential nonstructural system within buildings, providing egress to occupants as well as much needed access for emergency responders following an extreme event, such as an earthquake. Unfortunately, past earthquakes continue to reveal that these displacement-sensitive systems are highly vulnerable to damage and collapse. In this paper, high fidelity finite element models are developed and exercised in an effort to advance understanding of the seismic behavior of steel stairs under pseudo-static displacement loading indicative of earthquake-induced building movements. The proposed modeling approach is first validated through comparison with a set of experimental data and subsequently extended into a parametric study to broaden the range of stair configurations and details. In particular, the effect of story height, connection and landing details, and geometry on the behavior of the system is studied. Parametric analysis results indicate that the static force and displacement response of the stairs are sensitive to these key design parameters. Importantly, stair-to-buidling connections are subjected to large stress and strain demands under lateral displacement loading, as such their capability to maintain connectivity during an earthquake is crucial for robust seismic performance and hence continued functionality of the stair as a system.