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Showing 1-5 of 16 Abstracts search results

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: 

SP160-05

Date: 

June 1, 1996

Author(s):

Jeffery T. Miller and Lawrence D. Reaveley

Publication:

Symposium Papers

Volume:

160

Abstract:

The seismic upgrade of the Hotel Utah was accomplished by constructing new concrete shearwalls to strengthen an existing historic building constructed in the early 1900s. Feasibility studies were performed to consider different methods of seismic upgrade; results indicated that new concrete shearwalls would provide the most economical method of upgrade without significant impact on the interior floor plan of the building. Construction of the new shearwalls was performed, for the most part, at the interior of the building which required special design and construction procedures.

DOI:

10.14359/1549


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: 

SP160-09

Date: 

June 1, 1996

Author(s):

Azez Hindi

Publication:

Symposium Papers

Volume:

160

Abstract:

Reports tests of a three span reduced scale segmental box girder bridge model post-tensioned with external tendons. The objectives of this study included the determination of the effect of using external tendons discretely bonded at an intermediate diaphragm in each segment and/or using grouted internal tendons on the strength and ductility of external tendon bridges. The scope included experimentally determining and analytically predicting the external tendon maximum stress and the flexural capacity of the bridge. The flexural tests, performed on the three span model, were conducted in three phases. In the first phase, the external tendons were discretely bonded at only two or four intermediate diaphragms in each span. In the second phase, the external tendons were discretely bonded at all ten intermediate diaphragms in each span. In the third phase, supplementary ungrouted or grouted internal tendons were added. The test results indicated that discrete bonding of external tendons and/or using grouted internal tendons substantially improved the strength and ductility of this kind of construction.

DOI:

10.14359/1450


Document: 

SP160-02

Date: 

June 1, 1996

Author(s):

Riyad S. AboutahaI

Publication:

Symposium Papers

Volume:

160

Abstract:

Inadequate shear strength and inadequate lap splices in the longitudinal reinforcement are two major deficiencies in non-ductile reinforced concrete columns. Such deficiencies limit the lateral strength and ductility of older reinforced concrete moment-resisting frames. Provisions of older codes led to columns with shear strength less than required to develop the member's flexural capacity. Consequently, non-ductile shear response may dominate the behavior of older short columns. In addition, lap splices in older concrete columns were primarily designed as compression splices, but may actually experience large tensile forces during earthquakes. As a result, lap splices in older concrete columns are often inadequate to develop the yielding strength of the spliced bars in tension. This paper presents results of an experimental investigation on the use of rectangular steel jackets for seismic retrofit of rectangular reinforced concrete columns with inadequate shear strength or inadequate lap splices. Three large scale columns with inadequate lap splices and four large scale columns with inadequate shear strength were tested under lateral cyclic loading. The basic unretrofitted columns showed early dramatic non-ductile failures. However, the retrofitted columns with steel jackets exhibited excellent response, higher strength, and much higher ductility and energy dissipation. Test results suggest that rectangular steel jackets can considerably improve the performance of columns with inadequate shear strength. Also, the steel jackets can significantly enhance the response of wide columns with inadequate lap splices, when stiffened with adhesive anchor bolts.

DOI:

10.14359/1546


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