Determination of displacement limits for the seismic rehabilitation of concrete buildings

✍ Scribed by Ekwueme, Chukwuma G.

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 242 KB
• Volume: 8
• Category: Article
• ISSN: 1062-8002
• DOI: 10.1002/(sici)1099-1794(199906)8:2<79::aid-tal128>3.0.co;2-#

✦ Synopsis

As our understanding of the response of buildings to earthquakes improves, design codes in seismic regions around the world are changing to keep up with advances in the understanding of building performance. These changes demand the development of new analytical tools and procedures to satisfy the emerging design criteria. This paper describes analytical procedures that can be used with the voluntary ordinance for hazard reduction in existing concrete buildings in the City of Los Angeles, a typical example of the new, displacement-based seismic rehabilitation criteria. Displacement-based procedures demand an accurate representation of element stiffness over the entire range of building behavior and the methodology described herein determines element stiffness with nonlinear analyses that begin with the stress strain relationships of concrete and steel. Methods for determining the material stress versus strain relationships are reviewed, and the effects of lateral confinement and tension stiffening on concrete behavior are demonstrated. Material behavior is then extended to the development of moment-curvature relationships, which are the basis for determining the change in stiffness of flexural elements with increasing deformation. Displacement limits of the structure are determined by correlating the calculated building displacements and story drifts to strains and curvatures at critical cross sections. The paper presents techniques for performing this correlation by considering the redistribution of forces that occurs with changes in member stiffness at different displacement levels and by applying basic structural mechanics principles.