Theoretical investigations on load‐bearing capacity of RC flat‐plate framed structures subject to middle column loss

Abstract

Summary This paper presents theoretical studies on load‐bearing capacity of reinforced concrete flat‐plate framed structures. The existing methods for determining load‐bearing capacity of simply supported slabs are first reviewed, and their limitations are presented. An energy‐based refined method is then proposed to enhance the accuracy of the existing methods by considering the contributions to internal energy dissipation due to the extension of reinforcing bars along yield lines, the additional resultant bending moment from membrane forces, and the sectional bending moment along yield lines of slabs. The refined method for simply supported slabs is extended for fixed supported slabs, and thus, the load‐bearing capacity of reinforced concrete flat‐plate structures subject to a middle column loss is analytically determined. The performance of the proposed method is validated against test results and also verified against finite element analyses. Parametric studies are conducted to investigate the effect of reinforcement ratio, slab thickness and aspect ratio on the stiffness, and yield‐line resistance of structures. It is found that for the fixed supported slabs, it is reasonable to assume negative yield lines along the slab edges to consider the effect of obvious concrete crushing along the edge. Square slabs have higher ultimate loads than rectangular slabs, due to a longer horizontal yield line in the middle in the rectangular slab, which has detrimental effect on the sectional ultimate bending moment. The numerical results show that the reinforcement ratio has little effect on the initial bending stiffness and yield‐line resistance of slabs for a given slab thickness and aspect ratio. The initial stiffness and yield‐line resistance increase as the slab thickness increases. For the same reinforcement ratio and slab thickness, a larger aspect ratio leads to a lower initial bending stiffness, yield‐line resistance, and stiffness in tensile membrane action stage, due to a longer yield line along which tensile membrane forces have a detrimental effect on the sectional bending moment.

Experimental and Theoretical Investigations on Progressive Collapse Resistance of the Concrete‐Filled Square Steel Tubular Column and Steel Beam Frame under the Middle Column Failure Scenario

“…Harry and Lu [9] developed a simplified theoretical model for a generic beam in a column removal scenario, considering the degradation of strength in the plastic regions and axial restraint effect, and gained its resistance functions. Zhang et al [10] investigated loadbearing capacity of reinforced concrete flat-plate framed structures with simply supported slabs and fixed supported slabs. ey proposed an energy-based model considering the contributions of internal energy dissipation and yield-line effect; then, they analyzed the effect of its parameters on load-bearing capacity, such as reinforcement ratio, slab thickness and aspect ratio on the stiffness, and yield-line resistance.…”