دانلود رایگان مقاله انگلیسی ارزیابی محاسباتی رفتار لرزه ای پله های فولادی - الزویر 2018

ABSTRACT

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.

Conclusions

Despite the significance of stair systems related to occupant evacuation and post-event recovery operations following an earthquake, past events repeatedly demonstrate the seismic vulnerability of these critical nonstructural systems. Their seismic behavior is complex due to their variability in spatial geometry and construction details. This paper presents a computational study of the seismic response of prefabricated steel stair systems with a focus on scissors configured stairs. To this end, a high fidelity three-dimensional finite element model is first developed and validated against prior experimental results. A parametric study is subsequently performed to explore the impact of loading directions as well as critical design variables on the lateral force-displacement response of the stairs and the connection behavior. Design variables considered in this study include story height, landing post configuration, connection details, and geometric configuration. Based on the parametric analysis of eight stair models, key findings are summarized as follows:

1. The seismic behavior of the stair differs significantly between loading in the two horizontal directions. The stair attains larger forces and relative landing displacements when loading is applied in the parallel direction. The upper flight resembles an inclined axial member in the case of parallel loading, thus imposing large displacement demands on the landing and connections. In the case of transverse loading, the upper flight tends to perform as a flexural member, which effectively enhances the overall deformability and reduces the force demands of the stair. The selection of loading of course will be irrespective and may occur in sync, due to the natural bi-directional nature of an earthquake; nonetheless, these studies allow an understanding of the most critical conditions and potential design pitfalls that should be considered in practice.