Necessity of steel staircase separation and development of simplified design relationships

This study seeks to demonstrate the necessity of separating the staircase from the primary structure and, as an innovative and practical objective, to find a simplified and meaningful relationship between the inter-storey drift obtained from simplified analyses and measures such as the separation gap width in the separation method. Interaction between staircase components and the primary structure may lead to unforeseen behaviour in both the staircase components and the primary structure. Therefore, the separation method has a strong scientific and functional rationale. To this end, 48 steel building models were investigated. The results indicate that the ratio of the gap size to the inter-storey drift obtained from linear equivalent static analysis is similar among the studied models, except for the two-storey model. This ratio is at most 1.5 times at the first intermediate floor and at most 60% in the remaining floors. In the two-storey model, this ratio reaches up to three times at the first intermediate floor, while in the remaining floors it remains the same 60%. Furthermore, the provisions of the American Society of Civil Engineers/Structural Engineering Institute 7-22 standard concerning the minimum separation gap are considered inadequate for mid-rise steel moment-resisting frame structures.