Report - PEER - University of California, Berkeley

4. CONCLUSIONSIn the space available, a simple and effective design procedure was outlined thatexplicitly addresses roof drift, system ductility, and the influence of MDOF effects(higher mode effects). The design procedure uses an estimate of the yielddisplacement as a primary design parameter. Yield Point Spectra are used todetermine the required lateral strength. The fundamental period of vibration of thestructure is observed to be a consequence of the strength provided to satisfy theperformance objectives, rather than being an independent parameter whose value isestimated at the start of the design, as is done in conventional design procedures. Thebasic elements of the design approach are described herein; examples provided in thereferences suggest the robustness of the basic assumptions and procedures.The design procedure was developed on the basis of planar systems and involvedsimplifying assumptions. Various modifications can be considered. For example,corrections could be introduced to account for tendency of ESDOF systems tooverestimate the roof displacement of inelastic systems (e.g., Chopra et al., 2003).However, the slight conservatism that results from neglecting this effect is consideredadvantageous at this time. Similarly, the Yield Point Spectra format may be used toplot curves of other performance parameters (e.g., hysteretic energy dissipation orresidual displacement ductility). However, ductility is directly related to the roofdisplacement, and other parameters can be correlated to ductility (e.g., Farrow andKurama, 2003). Similarly, the design procedure is intended for structures that do notdevelop plan torsion. Extensions to consider torsionally-irregular structures can beconsidered at an appropriate time. Finally, the validity of the design proceduredepends on the accuracy with which the structure is modeled. Assumptions regardingthe strength, stiffness, and hysteretic characteristics of the lateral-force-resisting andgravity-load carrying structural components as well as the possible participation ofso-called “non-structural” components can be significant, regardless of the methodused for design.REFERENCESAschheim, M., E. Black (2000). Yield Point Spectra for seismic design andrehabilitation, Earthquake Spectra, 16(2):317-335.Aschheim, M. A. (2002). Seismic design based on the yield displacement, EarthquakeSpectra, 18(4):581-600.Aschheim, M. A., E. F. Black, I. Cuesta (2002). Theory of principal componentsanalysis and applications to multistory frame buildings responding to seismicexcitation, Engineering Structures, 24(8):1091-1103.Aschheim, M., E. Hernández Montes (2003). The representation of P-∆ effects usingYield Point Spectra, Engineering Structures, 25:1387-1396.Aschheim, M., T. Tjhin, C. Comartin, R. Hamburger, M. Inel (2004). The ScaledNonlinear Dynamic Procedure, ASCE Structures Congress, May 22-26.491