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International Concrete Abstracts Portal

Showing 1-5 of 11 Abstracts search results

Document: 

SP152-09

Date: 

March 1, 1995

Author(s):

E. J. Ulrich Jr., and C. J. Ehlers

Publication:

Symposium Papers

Volume:

152

Abstract:

The St. Luke's Medical Tower is the Texas Medical Center's tallest building and Houston's tallest building to open the 1990s. The combination of the following unique foundation features reduced development costs by over $1,000,000: (1) tallest soil-supported building on shallow foundations in the Southwest; (2) temporary dewatering system designed to function as the permanent system; (3) excavation-bracing system designed to form the permanent basement wall and only individual braces were temporary; (4) basement walls esigned to accept loads from future contiguous towers; (5) drilled pier soldier piles installed with polymer drilling fluid (the first use on a major Texas project); and (6) drill pier soldier piles installed in accordance with the new American Concrete Institute Standard Specification for the Construction of Drilled Piers (ACI 336.1-89), the first known use of the specification. The factored load condition was considered fictional in foundation, and basement wall design in that factored load-concrete-subgrade compatibility was not achieved. Significant cost savings was achieved by allowing the geotechnical engineer to be part of the design team beginning with project concept studies and extending throughout underground construction. The geotechnical engineer and the team developed feasible foundation schemes that could be integrated into construction needs, instead of relying only on specialty design builders.

DOI:

10.14359/1527


Document: 

SP152-10

Date: 

March 1, 1995

Author(s):

J. P. Stewart, K. H. Pitulej, and H. S. Lacy

Publication:

Symposium Papers

Volume:

152

Abstract:

Describes the design of a load-compensated mat foundation on highly compressible soil. The mat was used to support over 800,000 square feet of variable height building. While the design of the mat was mostly routine, the behavior at the mat edges was difficult to determine. The deformations at mat edges were the major concern since they were influenced by the need to raise grades around the building perimeter. The design procedure incorporated soil-structure interaction analysis to determine the extent of lightweight fill zones required to control edge deformations. Settlement monitoring over a period of two years has confirmed the design approach.

DOI:

10.14359/1529


Document: 

SP152-05

Date: 

March 1, 1995

Author(s):

J. S. Horvath

Publication:

Symposium Papers

Volume:

152

Abstract:

Two mat foundations supporting buildings were analyzed using traditional methods for modeling soil subgrades, as well as more recently developed methods. The primary purpose of the analysis was to evaluate the relative and absolute accuracy of subgrade models that can be used in routine practice. The results indicate that some of the newer methods consistently provide significantly better agreement between calculated and observed behavior compared to the traditional methods. In addition, determination of the appropriate subgrade parameters is more rational with the newer methods. With current computer analysis capabilities, there is no reason to continue use of traditional methods that were reasonable alternatives when only manual calculations could be performed. Detailed recommendations for modeling subgrades in practice are presented, with consideration given to the capabilities of commercially available structural analysis computer software. Other factors that influence mat behavior, such as superstructure interaction effects, are also discussed.

DOI:

10.14359/1434


Document: 

SP152-04

Date: 

March 1, 1995

Author(s):

E. J. Ulrich, Jr.

Publication:

Symposium Papers

Volume:

152

Abstract:

Often, an apparently compatible relationship between mat and soil deteriorates due to the plague of construction details and the design-construction relationship. This paper reviews subgrade reaction in case studies of four landmark buildings in Houston. Concepts related to mat foundation analysis using the finite element method are discussed to acquaint the practitioner with the related soil-structure interaction concepts. Also included is an examination of structural considerations in connection with mat foundation design.

DOI:

10.14359/1453


Document: 

SP152-01

Date: 

March 1, 1995

Author(s):

E. J. Ulrich, JR.

Publication:

Symposium Papers

Volume:

152

Abstract:

Subgrade response is the most important parameter in analyzing and designing mat foundations. Rational design of a mat foundation requires consideration of immediate and long term subgrade response. The soil response determines mat behavior, and differential movement exacerbates moments. Often, long term movement provides the most severe mat behavior characteristics. The popular use of a single modulus of subgrade reaction k, to model subgrade response is wrong and will lead to wrong designs. Mat analysis and design should be performed using the discrete area method, in which subgrade responses can be properly modeled because of the use of varying moduli of subgrade reaction. The geotechnical engineer and the structural engineer must form a solid bond to cope with mat foundation design from early planning through construction; both must work together to assure successful performance. Often, construction details and procedures will govern performance and can ruin any analysis. For this reason, the geotechnical engineer should be on site accessing conditions.

DOI:

10.14359/1519


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