Seismic response evaluation of single-layer latticed shells based on equivalent modal stiffness and linearized iterative approach

Abstract

Seismic evaluation methods based on the modal decomposition principle highly depend on whether the dominant modes of a structure are correctly identified, but current modal pushover methods usually ignore this core issue. Firstly in this paper, the established threshold value method for mode identification is enhanced with a stronger theoretical basis considering the harmonic loading and resonance, so that the dominant modes can be truncated more convincingly. Then due to the rough description of capacity curve in the conventional modal pushover method using the base shear and roof displacement, overall coupling responses are incorporated into the derivation of the equivalent modal stiffness, who associates the modal properties with the overall ones. On this basis, the capacity curve is obtained and the equivalent single-degree-of-freedom system is generated, which essentially differs from that of the conventional method. Seeing the capacity curve featured with strong nonlinearity, a linearized iterative approach is proposed for accurate estimation of the performance point. Thus, an improved modal pushover procedure is established. For detailed comparative evaluation, three single-layer latticed shells and a practical engineering structure, named Shanghai International Convention Center, are employed as analytical models with initial geometrical imperfection and member buckling considered. Calculating results of nodal displacements, element stresses, as well as the quantity of yielding members, demonstrate the unfavorable underestimation from the conventional method. Meanwhile, good agreement on response estimation is reached between the improved procedure and the nonlinear response history analysis method, attesting the satisfying accuracy of the improved procedure.