Abstract
The paper presents a method of estimating earthquake responses of asymmetric reinforced concrete structures based on nonlinear deformation modes. Shaking table tests of one-third scale six-story eccentric reinforced concrete wall-frame specimens were conducted and analyzed with a nonlinear three-dimensional frame model. A fair correlation was observed between the test and the frame analysis. Several wall-frames were designed by varying the plan, location and stiffness of the walls from the specimen to simulate general cases of torsional responses, where the 2nd mode is dominant as well. The intensities of the earthquake motions for the simulation were also varied to simulate also wide range of structural responses from elastic to inelastic deformations. The dominant modes were derived from the nonlinear responses, in which general characteristics were discussed in terms of effective mass ratio. The value approaches a constant when the inelastic response is large. The constant could be derived from nonlinear pushover analysis considering the first mode and the second mode in the assumed load vectors. A new method of estimating nonlinear responses based on the deformation modes in the dynamic responses are proposed based on the general characteristics. The estimates are compared with the results of nonlinear dynamic frame analysis, where a better correlation was observed than those by past simple methods generally from elastic to inelastic responses.
