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A simulation method for the fire-induced progressive collapse of concrete structures

Numerical simulation is an important method to investigate the fire-induced progressive collapse of the entire structural system of building structures. In this work, a numerical method to simulate the fire-induced progressive collapse of reinforced concrete (RC) structures is proposed. Firstly, the high-efficiency elements for structural elements exposed to fire action are established, including a fiber beam element and a multi-layer shell element, by integrating the materials constitutive relations of steel and concrete under high temperature with the conventional beam and shell elements. To simulate the discontinuous displacement field during the structural collapse, the element deactivation technology and the corresponding failure criteria for various structural components are introduced to the proposed finite element models. Therefore, the influence of the internal force redistribution in the structural systems due to the failure and fracture of structural components on the collapse behavior of the whole structures can be considered. Furthermore, to efficiently simulate the quasi-static process of fire action and the dynamic process of structural progressive progress, this paper presents an equivalent time method to analyze the alternative static-dynamic processes by using the dynamic approach only. A computing time ratio is proposed in this method to transform the long fire acting time into the short virtual dynamic time. By this way，the computing time of the dynamic analysis under the fire action is reduced significantly．At last, the accuracy and efficiency of the element models are validated via a series of tests on the RC members in fire, including beams, columns and slabs. The application of the numerical method is demonstrated through the simulation of the fire-induced progressive collapse of a high-rise RC frame-core tube structure.

Author(s):

Mengzhu Diao    
Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology
China

Yi Li    
Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology
China

Xinzheng Lu    
Key Laboratory of Civil Engineering Safety and Durability of Ministry of Education, Tsinghua University
China

Mingjian Ying    
Key Laboratory of Civil Engineering Safety and Durability of Ministry of Education, Tsinghua University
China