Limit State Design in Geotechnical Engineering and its Applications for Deep Foundations in Egypt
Muhammad Ahmed El Sayed Zayed;
Abstract
The Working Stress Design (WSD) philosophy has been used for the design of foundations in Egypt; however the Limit State Design (LSD) philosophy is used in the design of superstructures. The incompatibility arises from applying two different design philosophies for both substructures and superstructures has led to confusions and misleading due to the use of incompatible design philosophies. Subsequently, implementation of LSD in the geotechnical design in Egypt has become essential.
In this study, the main differences between WSD and LSD were investigated. The feasibility of applying LSD philosophy for the geotechnical design in Egypt was examined. A rational procedure to calibrate the reduction factors and partial safety factors, to be used with LSD, was inspected and illustrated. The developed calibration procedure was applied on the design methods of pile foundations. Reduction factors and partial safety factors for axially loaded single piles were calibrated via calibration-by-fitting technique. Two different approaches of the factored resistance approach and the factored strength approach were employed in the calibration procedure of the reduction factors and partial safety factors.
CHAPTER (5)
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The aim of the calibration process was to define the required reduction factors and partial safety factors so that design values using LSD shall be quite close to those obtained from current practice of WSD, so that the foundation designed based on LSD would not suddenly appear significantly over-designed or under-designed with respect to past experience. As such, it was difficult to determine what sort of improvements the LSD philosophy offered. However, this is essential for the transition phase where both design philosophies shall be applicable for different geotechnical design problems.
Reduction factors for total pile resistance and pile side and base resistance were evaluated using calibration-by-fitting technique throughout applying the factored resistance approach, i.e., Load and resistance Factor Design (LRFD). Partial safety factors for soil strength parameters to be used in LSD were assessed using the same calibration technique throughout applying the factored strength approach.
The calibrated resistance reduction factors from this study are found to be relatively consistent with those values adopted in other geotechnical limit state design codes worldwide.
5.2. Conclusions
Based on the conducted calibration of the reduction factors and the partial safety factors, the following conclusions are offered:
1) The use of WSD in Egyptian geotechnical practice has proved to fulfill the aspects of safety and economy and has been supported by
In this study, the main differences between WSD and LSD were investigated. The feasibility of applying LSD philosophy for the geotechnical design in Egypt was examined. A rational procedure to calibrate the reduction factors and partial safety factors, to be used with LSD, was inspected and illustrated. The developed calibration procedure was applied on the design methods of pile foundations. Reduction factors and partial safety factors for axially loaded single piles were calibrated via calibration-by-fitting technique. Two different approaches of the factored resistance approach and the factored strength approach were employed in the calibration procedure of the reduction factors and partial safety factors.
CHAPTER (5)
-117-
The aim of the calibration process was to define the required reduction factors and partial safety factors so that design values using LSD shall be quite close to those obtained from current practice of WSD, so that the foundation designed based on LSD would not suddenly appear significantly over-designed or under-designed with respect to past experience. As such, it was difficult to determine what sort of improvements the LSD philosophy offered. However, this is essential for the transition phase where both design philosophies shall be applicable for different geotechnical design problems.
Reduction factors for total pile resistance and pile side and base resistance were evaluated using calibration-by-fitting technique throughout applying the factored resistance approach, i.e., Load and resistance Factor Design (LRFD). Partial safety factors for soil strength parameters to be used in LSD were assessed using the same calibration technique throughout applying the factored strength approach.
The calibrated resistance reduction factors from this study are found to be relatively consistent with those values adopted in other geotechnical limit state design codes worldwide.
5.2. Conclusions
Based on the conducted calibration of the reduction factors and the partial safety factors, the following conclusions are offered:
1) The use of WSD in Egyptian geotechnical practice has proved to fulfill the aspects of safety and economy and has been supported by
Other data
| Title | Limit State Design in Geotechnical Engineering and its Applications for Deep Foundations in Egypt | Other Titles | التصميم بطريقة حالات الحدود في الهندسة الجيوتقنية وتطبيقاتها على الاساسات العميقة في مصر | Authors | Muhammad Ahmed El Sayed Zayed | Issue Date | 2014 |
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