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International Concrete Abstracts Portal

Showing 1-5 of 16 Abstracts search results

Document: 

SP160-15

Date: 

June 1, 1996

Author(s):

James Warnar

Publication:

Symposium Papers

Volume:

160

Abstract:

Simply stated, shotcrete is sprayed concrete or mortar. Because of difficulty in obtaining good compaction and fully encasing large or closely spaced bars, it has traditionally been used in thin, relatively lightly reinforced sections. Unique to seismic repair and retrofit are heavily reinforced and often thick sections. Because of its ease of application in areas of poor access and the resulting reduction in construction time and cost, the process can be especially advantageous in seismic applications. Special procedures are required, however, to obtain good quality work under the common inherent constraints that often exist and overcome the limitations. Although not widely recognized, proven procedures are well established and have been successfully used in seismic repair and retrofit applications for nearly 50 years. Basic principles of the shotcrete process are reviewed in this paper; those special procedures required for proper placement in heavily reinforced and thick sections are discussed.

DOI:

10.14359/1556

Document: 

SP160-14

Date: 

June 1, 1996

Author(s):

Christopher R. Thewalt and Bozidar Stajadinovic

Publication:

Symposium Papers

Volume:

160

Abstract:

The catastrophic collapse of the old Cypress Viaduct during the 1989 Loma Prieta earthquake emphasized the vulnerability of elevated freeway bridge structures. One track of the joint Caltrans and University of California, Berkeley, research project is the investigation of outrigger knee joints found in elevated freeway bents. This project has two principal goals: to evaluated the behavior of the existing outrigger knee joint subassemblies under a combined transverse and longitudinal loading and to devise and experimentally verify upgrading strategies and repair techniques suitable for application on the existing elevated freeways. The performance of the existing outrigger knee joint subassemblies was evaluated by testing two as-built models. After considering several upgrading strategies, two were tested on the remaining five specimens. In parallel with the experiments, a set of tools was developed for design and analysis of the upgraded subassemblies. A summary of the design, analytical, and experimental work conducted to date is presented in this paper.

DOI:

10.14359/1555

Document: 

SP160-10

Date: 

June 1, 1996

Author(s):

Bernard L. Meyers

Publication:

Symposium Papers

Volume:

160

Abstract:

Describes the seismic rehabilitation methods for the reinforced concrete substructures of two structural steel bridges in California, the South San Francisco Overhead Bridge and the Los Angeles River Bridge. The rehabilitation is part of the seismic retrofit program implemented by the California Department of Transportation (Caltrans) after the 1989 Loma Prieta earthquake. The analysis and design basically followed the general seismic retrofit principles and guidelines developed by Caltrans and other research institutes in recent years. However, due to the site conditions and retrofit limitations of these two bridges, innovative methods were employed to minimize the retrofit costs.

DOI:

10.14359/1554

Document: 

SP160-08

Date: 

June 1, 1996

Author(s):

Edward R. Fyfe

Publication:

Symposium Papers

Volume:

160

Abstract:

In 1987, testing began on a concept to use high strength fibers to retrofit columns to increase strength and ductility. The tests were completed on 14 columns at the University of California, San Diego. Columns were tested for confining the lap-splice flexural areas for circular and rectangular columns with increased strength and ductilities in testing of eight or more. Columns were tested for shear-flexural performance (with no lap-splice) with tested increased strength and ductilities of eight or more. The rectangular columns were wrapped in the shape of the rectangle successfully. The University of British Columbia in Vancouver used the wrap system for columns and pier cap retrofit and obtained a ductility of 12. Thirty-two field installations have been completed as of October 1994. Design recommendations and durability testing has been completed.

DOI:

10.14359/1552

Document: 

SP160-06

Date: 

June 1, 1996

Author(s):

Zareh B. Gregorian and Garen B. Gregorian.

Publication:

Symposium Papers

Volume:

160

Abstract:

Prior to the upgrading the seismic zoning of Massachusetts, not much attention was given to new or existing structures in the east coast with regard to seismic design and strengthening. Strengthening existing structures undergoing renovations has become mandatory for all government owned and operated buildings. This paper is the result of strength evaluation of two VA hospital buildings which are planned to undergo major renovations. Various options were considered for seismic strengthening of the two existing reinforced concrete frame structures, built in the 1930s without any earthquake load design considerations. Adding interior shearwalls, exterior buttresses, steel cross bracings, and base isolation proved to be complex, costly, and undesirable for architectural reasons. Use of peripheral shearwalls, attached to existing concrete frames was considered as a final solution for strengthening.

DOI:

10.14359/1550

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