The effective fundamental period, Te , in the direction under consideration, shall be determined using the force-displacement relation of the nonlinear static pushover analysis. The nonlinear relation between the base shear and target displacement of the control node shall be replaced by a bilinear relation to estimate the effective lateral stiffness, Ke , and the yield strength, Vy , of the building. The effective lateral stiffness shall be taken as the secant stiffness calculated at a base shear force equal to 60 percent of the yield strength. The effective fundamental period, Te , shall then be calculated as:
where:
where:
| Ti | = | Elastic fundamental period in the direction under consideration calculated by elastic dynamic analysis. |
| Ki | = | Elastic lateral stiffness of the building in the direction under consideration. |
| Ke | = | Effective lateral stiffness of the building in the direction under consideration. |