Partial Capacity Design, An Alternative to the Capacity Design Method

The Capacity Design method (CDM) is a well accepted design procedure for earthquake resistant design. CDM employs strong column-weak beam design philosophy. The failure mechanism expected in the CDM is the so called Side Sway Mechanism. To ensure that the side sway mechanism can develop, the columns should be designed stronger than the capacity of the beams. In the cases of gravity load dominated structures, forcing the column to be stronger than the beams will lead to excessive column strength. Applying CDM also implies that the columns can not be designed before the beams are designed. Hence, this is not very practical in real world of design practice. To overcome these shortcomings, the authors investigate several alternatives allowing partial side sway mechanism, in which the internal columns are allowed to develop plastic hinge while the perimeter columns are to remain elastic for a certain seismic load level except at the base of the structure. To ensure that the perimeter columns remain elastic, these perimeter columns are designed to resist magnified internal forces due to the nominal earthquake load multiplied by a certain magnification factor, f. This method is called the Partial Capacity Design Method (PCDM). Several efforts have been made to find the suitable magnification factor. In the latest development the determination of the magnification factor is based on the natural period of the structure in plastic condition, the plastic period. The plastic period, Tpl is predicted using a correlation between the elastic and plastic natural period developed from data of several structures previously observed. This paper describes the basic concepts of the CPDM and shows the performance of several symmetrical fully ductile concrete moment resisting frames designed in accordance with the latest Indonesian Seismic Code (SNI 03 1726-2002) using the proposed method. The seismic performances of these buildings are evaluated using three-dimensional static nonlinear pushover and dynamic nonlinear time history analyses.