A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Load and Resistance Factor Design (LRFD) for Deep Foundations
Full implementation of the AASHTO LRFD Bridge Design Specifications for deep foundations is hampered by provisions that are inconsistent with current geotechnical engineering practice. Static pile-capacity analyses are typically used to estimate required pile lengths and quantities, whereas dynamic analyses are used to determine pile capacity during pile driving. Currently, the resistance factors for static and dynamic analysis are multiplied by each other, resulting in designs that are significantly more conservative than used in past practice, increasing foundation costs. Resistance factors for drilled shafts in sand or gravel are not provided in the LRFD Specifications, and many of the state departments of transportation do not have the data or the resources to do their own calibrations as recommended in the specification. The effect of various construction techniques on drilled shaft resistance factors also is not addressed in the LRFD Specifications. The resistance factors for deep foundations were not calibrated for the LRFD load factors. In addition, the resistance factors do not account for the variability of the site conditions and the number of load tests conducted. Another shortcoming is that many accepted design procedures, some of which are commonly recommended by FHWA, are not supported by the LRFD Specifications. The objective of this research was to address the aforementioned issues and to provide resistance factors for the load and resistance factor design of deep foundations. Under NCHRP Project 24-17, the University of Massachusetts at Lowell with the assistance of D'Appolonia, the University of Maryland, the University of Florida, and the University of Houston assembled databases for static analysis of drilled shafts and driven piles and for dynamic analysis of driven piles. These databases were used for the statistical evaluation of resistance factors.
Load and Resistance Factor Design (LRFD) for Deep Foundations
Full implementation of the AASHTO LRFD Bridge Design Specifications for deep foundations is hampered by provisions that are inconsistent with current geotechnical engineering practice. Static pile-capacity analyses are typically used to estimate required pile lengths and quantities, whereas dynamic analyses are used to determine pile capacity during pile driving. Currently, the resistance factors for static and dynamic analysis are multiplied by each other, resulting in designs that are significantly more conservative than used in past practice, increasing foundation costs. Resistance factors for drilled shafts in sand or gravel are not provided in the LRFD Specifications, and many of the state departments of transportation do not have the data or the resources to do their own calibrations as recommended in the specification. The effect of various construction techniques on drilled shaft resistance factors also is not addressed in the LRFD Specifications. The resistance factors for deep foundations were not calibrated for the LRFD load factors. In addition, the resistance factors do not account for the variability of the site conditions and the number of load tests conducted. Another shortcoming is that many accepted design procedures, some of which are commonly recommended by FHWA, are not supported by the LRFD Specifications. The objective of this research was to address the aforementioned issues and to provide resistance factors for the load and resistance factor design of deep foundations. Under NCHRP Project 24-17, the University of Massachusetts at Lowell with the assistance of D'Appolonia, the University of Maryland, the University of Florida, and the University of Houston assembled databases for static analysis of drilled shafts and driven piles and for dynamic analysis of driven piles. These databases were used for the statistical evaluation of resistance factors.
Load and Resistance Factor Design (LRFD) for Deep Foundations
S. G. Paikowsky (author)
2004
87 pages
Report
No indication
English
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