Design for Lateral Loads/Systems

Single Abstract

341185 - Evaluation of Current Design Practice for Structures Subjected to Near-Field Ground Motions

Friday, April 20
11:00 AM - 12:30 PM
Location: 204AB

Near-field ground motions with forward rupture directivity effect contain strong pulses at the beginning of the record and as a result are recognized to impart high amount of energy into the structure. These pulse-type motions can place severe seismic demands on the structures, causing extensive damage in cases where the lateral load-resisting systems have not been properly designed for the near-field effects. The response characteristics that set these motions apart from the far-field ordinary earthquakes underscore the need for designers and researchers to develop specific design provisions for structures located near a seismic source. Nevertheless, the design response spectra as defined in the current seismic design codes are generated under the hypothesis of far-field ordinary events and are merely modified by introducing additional factors to take into account the near-field seismic response. To evaluate the adequacy of the current design practice for seismic resiliency of these structures in the near-fault regions, this paper presents an evaluation of drift demands for a prototype 12-story concrete structure subjected to fault-normal component of a set of near-field records with forward rupture directivity. This structure is designed with special moment resisting frames and shear walls in two orthogonal directions for a site class in Los Angeles, California (seismic zone 4 and soil type SC), following both a: (i) Direct Displacement-Based Design (DDBD) approach, and (ii) Force-Based Design (FBD) procedure as incorporated in the building codes. Results from nonlinear dynamic time history analysis of the prototype structure will be used to: (i) assess the structural seismic performance during near-field motions with different intensities; and (ii) evaluate adequacy of the near-field effects that exist in both force- and displacement-based design methodologies as used in current codes around the world. The information presented in this study is deemed useful for establishing design response spectra of equivalent pulse-type records representing near-field ground motions with different characteristics.

Maryam Nazari

Assistant Professor- Department of Civil and Geomatics Engineering
California State University, Fresno

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Sri Sritharan

Wilkinson Chair of Engineering and Professor of Civil Engineering
Iowa State University

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