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Nhan đề: Pile Testing - Selection and Economy of Safety Factors
Tác giả: Likins, Garland
Từ khoá: Safety
Static loads
Load and resistance factor design
Pile tests
Load tests
Allowable stress design
Foundation design
Năm xuất bản: 2004
Tóm tắt: Historically, while driven piles were designed conservatively by a static analysis, and then almost always installed to a driving formula, the inaccuracy of dynamic formulae for field verification of pile capacity is widely recognized. In some cases the design was verified by a static load test, performed along ASTM D1143 procedures to a maintained load of two times the design load, which engineers viewed as having the same effect as the pile having a safety factor of two. However, since static tests rarely failed, the actual safety factor was certainly higher. Modern piling practices have seen several improvements. The Federal Highway Administration (FHWA) actively promoted quick static loading procedures to up to three times the design load. Computer analyses with the so-called "wave equation" (with realistic models for hammer, pile, and soil) have largely replaced dynamic formulae. Over the last 30 years, dynamic pile testing has become routine due to (a) good correlation with static tests to failure, (b) the additional information it provides on hammer performance and driving stresses, and (c) the economy of this testing. Codes, both in public and private sectors, have been developed for both load and resistance factor design (LRFD) and allowable stress design (ASD) to minimize the risk of foundation failures. The selection of global safety factors (or LRFD resistance factors) to satisfy a foundation design with tolerable risk and at an acceptable cost relates to the type and amount of capacity verification performed. Based on a review of several codes, a comparison of traditional methods of dynamic formulae and static analyses with modern methods of analysis and testing is made, demonstrating the economics of the modem methods through the reduction in safety factors.
Mô tả: Contributions in Honor of George G. Gobel July 27-31, 2004 | Los Angeles, California, United States © 2004 American Society of Civil Engineers
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