Techno Press

Steel and Composite Structures   Volume 28, Number 2, July25 2018, pages 209-221
Dynamic increase factor for progressive collapse analysis of semi-rigid steel frames
Yan Fei Zhu, Chang Hong Chen, Yao Yao, Leon M. Keer and Ying Huang

Abstract     [Full Text]
    An empirical and efficient method is presented for calculating the dynamic increase factor to amplify the applied loads on the affected bays of a steel frame structure with semi-rigid connections. The nonlinear static alternate path analysis is used to evaluate the dynamic responses. First, the polynomial models of the extended end plate and the top and seat connection are modified, and the proposed polynomial model of the flush end plate connection shows good agreement as compared with experimental results. Next, a beam model with nonlinear spring elements and plastic hinges is utilized to incorporate the combined effect of connection flexibility and material nonlinearity. A new step-by-step analysis procedure is established to obtain quickly the dynamic increase factor based on a combination of the pushdown analysis and nonlinear dynamic analysis. Finally, the modified dynamic increase factor equation, defined as a function of the maximum ratio value of energy demand to energy capacity of an affected beam, is derived by curve fitting data points generated by the different analysis cases with different column removal scenarios and five types of semi-rigid connections.
Key Words
    progressive collapse; dynamic increase factor; alternate path method; nonlinear static analysis; semi-rigid steel frame
(1) Yan Fei Zhu, Chang Hong Chen, Yao Yao:
School of Mechanics and Civil Engineering, Northwestern Polytechnical University, Xi'an, 710129, China;
(2) Leon M. Keer:
Civil and Environmental Engineering, Northwestern University, Evanston, IL, 60286, USA;
(3) Ying Huang:
School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an, 710055, China.

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