The importance of lower-bound capacities in geotechnical reliability assessments [electronic resource]
| Title: | The importance of lower-bound capacities in geotechnical reliability assessments [electronic resource] |
| Author: | Najjar, Shadi Sam. |
| Abstract: | The ability to manage risk in geotechnical engineering relies on a realistic assessment of the probability of failure for designs . Most reliability analyses focus on the mean and variance and an assumed , mathematically convenient distribution to model the left -hand tail of the distribution for capacity . However , the reliability of a geotechnical engineering system is governed by a physical constraint on the smallest available capacity . This lower -bound capacity is usually neglected in conventional reliability analyses . In this study , databases of load tests conducted on offshore and onshore deep foundations are analyzed to provide evidence for the existence of a lower -bound capacity that can be calculated using site -specific soil properties and information about the geometry of the foundation . Next , realistic probability distributions that can accommodate a lower -bound capacity are proposed and used to relate reliability to the lower -bound capacity . Multiple Load and Resistance Factor Design (LRFD ) design -checking formats that include information on the lower -bound capacity in addition to the conventional design information are then introduced . Finally , practical approaches are presented for updating information about lower -bound capacities using installation data , proof -load data , and historical performance of foundations under load . Databases with deep foundations show clear evidence of the existence of a lower -bound capacity that typically ranges from 0 .4 to 0 .8 of the predicted capacity in both cohesive and cohesionless soils . Results from reliability analyses indicate that the presence of a lower -bound capacity can have a significant effect on increasing the reliability of a deep foundation . The effect of the lower -bound capacity increases as the coefficient of variation for the capacity increases and as the target reliability index increases . This result indicates that reliability -based design codes need to incorporate information about lower -bound capacities . Incorporation of a lower -bound capacity into design is expected to provide a more realistic quantification of reliability for decision -making purposes and therefore a more rational basis for design . |
| URI: |
http : / /hdl .handle .net /2152 /1499
http : / /hdl .handle .net /2152 /1499 |
| Date: | 2006-01-27 |
Citation
(2005).
The importance of lower-bound capacities in geotechnical reliability assessments [electronic resource].
Doctoral dissertation,
The University of Texas at Austin. Available electronically from
http : / /hdl .handle .net /2152 /1499
.
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