Techno Press
Techno Press

Earthquakes and Structures
  Volume 18, Number 2, February 2020 , pages 263-273
DOI: https://doi.org/10.12989/eas.2020.18.2.263
 


Computing input energy response of MDOF systems to actual ground motions based on modal contributions
Taner Ucar

 
Abstract
    The use of energy concepts in seismic analysis and design of structures requires the understanding of the input energy response of multi-degree-of-freedom (MDOF) systems subjected to strong ground motions. For design purposes and non-time consuming analysis, however, it would be beneficial to associate the input energy response of MDOF systems with those of single-degree-of-freedom (SDOF) systems. In this paper, the theoretical formulation of energy input to MDOF systems is developed on the basis that only a particular portion of the total mass distributed among floor levels is effective in the nth-mode response. The input energy response histories of several reinforced concrete frames subjected to a set of eleven horizontal acceleration histories selected from actual recorded events and scaled in time domain are obtained. The contribution of the fundamental mode to the total input energy response of MDOF frames is demonstrated both graphically and numerically. The input energy of the fundamental mode is found to be a good indicator of the total energy input to two-dimensional regular MDOF structures. The numerical results computed by the proposed formulation are verified with relative input energy time histories directly computed from linear time history analysis. Finally, the elastic input energies are compared with those computed from time history analysis of nonlinear MDOF systems.
 
Key Words
    
 
Address
Department of Architecture, Dokuz Eylul University, 35390, Buca, Izmir, Turkey
 

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