ERROR ANALYSIS AND IMPROVEMENTS OF LARGE SPRING/STIFFNESS METHOD FOR STRUCTURAL DYNAMIC RESPONSE ANALYSIS

To verify the practical applicability and accuracy of the large spring/stiffness method (LSM), the dynamic responses of a two-degree-freedom (2DOF) finite element model using the Rayleigh damping assumption are performed respectively according to the LSM and traditional theoretical methods under four groups of seismic ground motion excitations. The origin of errors and the applicability of the LSM are discussed. Then the improved LSM application to a uniform excitation and a non-uniform excitation are respectively presented herein, based on the modification of ground displacements considering the influences of Rayleigh damping. It indicates that the LSM is inapplicable to the structural seismic response analysis in the case of Rayleigh damping theoretically. And the errors depend on the damping coefficients α and β in the case of the uniform seismic excitation and on the coefficient β in the case of the non-uniform seismic excitation respectively. The errors increase monotonously with the aggrandizement of the damping coefficient β. It is also validated that the improved LSM is able to yield results that are identical to those of traditional theoretical methods.