Ductility-based seismic design of precast concrete large panel buildings

Two approximate methods based on mechanism analysis suitable for seismic as sessment/design of structural concrete are reviewed. The methods involve us e of equal energy concept or equal displacement concept along with appropri ate patterns of inelastic deformations to relate structure's maximum latera l displacement to member and plastic deformations. One of these methods (Cl ough's method), defined here as a ductility-based approach, is examined in detail and a modification for its improvement is suggested. The modificatio n is based on estimation of maximum inelastic displacement using inelastic design response spectra (IDRS) as an alternative to using equal energy conc ept. The IDRS for demand displacement ductilities are developed for a singl e degree of freedom model subjected to several accelerograms as functions o f response modification factor (R), damping ratios, and strain hardening. T he suggested revised methodology involves estimation of R as the ratio of e lastic strength demand to code level demand, and determination of design ba se shear using R-design less than or equal to R and maximum displacement, d etermination of plastic displacement using IDRS and subsequent local plasti c deformations. The methodology is demonstrated for the case of a 10-story precast wall panel building.