Determination of critical collapse resistance of steel framed-structure: Fast manual calculation

Abstract

This paper proposes a fast manual calculation method for determining the critical collapse resistance (CCR) of steel frame structures caused by an edge column loss. The critical collapse deformation (CCD) of the frame structure in an edge column loss is determined prior to calculating the CCR. Systematic parametric analysis is performed to examine the impacts of floor aspect ratio, slab rebar, slab thickness, beam depth, and beam span on the CCD of the frame structure. It is found that the CCD of the frame structure caused by the edge column loss can be determined by the beam depth, beam span and floor aspect ratio. When the beam span is increased by one beam depth, the CCD of the frame structure is increased by 0.2 times of the beam depth. The slab rebar and slab thickness have minimal effects on the CCD of the frame. When the rebar diameter and slab thickness are decreased by 50 % and 30 % respectively, the change of the CCD of the frame structure is within 10 %. A hardening factor is introduced to calculate the CCR of the frame in an edge column loss, defined as the ratio of the CCR to the yield resistance of the frame. Through more than 20,000 parametric analyses, it is found that the hardening factor can be determined by the normalized CCD (NCCD, the ratio of CCD to the yielding deformation) and the span-to-thickness ratio (STR) of the slab. For the STR of 40 and NCCD of 32, the hardening factor of the frame structure in an edge column loss is more than 3.0. A detailed process for calculating the CCR of the frame structure in an edge column loss is given. The results in the case study demonstrate that the error between the proposed method and the numerical analysis is within 10 %.