- Author
- Gross, J. L. | Kunnath, S. K.
- Title
- Application of Inelastic Damage Analysis to Double-Deck Highway Structures.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Department of the Interior, Reston, VA
- Report
- NISTIR 4857, August 1992, 83 p.
- Distribution
- Available from National Technical Information Service
- Keywords
- highways | structures | computer models | damage | earthquakes | reinforced concretes | case histories
- Identifiers
- computer analysis; finite element analysis; inelastic analysis; seismic analysis; structural analysis; Cypress Viaduct; Inelastic Damage Analysis of Reinforced Concrete Structures (IDARC)
- Abstract
- The Loma Prieta earthquake of October 17, 1989, caused extensive damage to many highway structures and particularly to double-deck structures. The most notable was the collapse of the Cypress Viaduct (Interstate 880). A study was undertaken by NIST to identify, using computer-based analysis methods, causes of structural failure of elevated highway structures resulting from the Loma Prieta earthquake and thereby reveal the potential for damage or collapse of similar structures nationwide. The IDARC analysis program, developed at the University of Buffalo, was used in the inelastic seismic analysis. Features of the program and enhancements incorporated to model the Cypress Viaduct structure are described. To accurately determine beam and column moment-curvature relationships, separate computer analyses were conducted. In addition, a smeared-crack approach finite element analysis was employed to determine the lateral load-deformation relationship of the pedestal regions. The model of the Cypress Viaduct was subjected to the Oakland Outer Harbor Wharf ground acceleration record in the plane of the bent. The analysical model was calibrated using static lateral load tests, ambient and forced vibration tests, and observed performance. Results of time-history analyses, which include a prediction of member damage, indicate that collapse was initiated by a shear failure of the pedestal regions as concluded by the Governor's Board of Inquiry. The analytical and modeling procedures reported herein may be used to faciliate comparison and selection of effective approaches to seismic strengthening.