Development of variable LRFD φ factors for deep foundation design due to site variability.

Details

• Creators:
  McVay, Michael C. ; Klammler, Harald ; Faraone, Michael A. ; Dase, Krishnarao ; Jenneisch, Chris
• Corporate Creators:
  University of Florida. Dept. of Civil and Coastal Engineering
• Corporate Contributors:
  Florida. Department of Transportation ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • Load factor
  • Foundation engineering
  • Design practices
  • Surveying
  • Location
  • Resistance (Mechanics)
  • Piers (Supports)
  • Soil structure
  • Soils
  • Soil compaction
  More +
• Resource Type:
  Tech Report
• Geographical Coverage:
  Florida
• Edition:
  Final report; 9/1/10-5/1/12.
• Corporate Publisher:
  Florida Department of Transportation
• Abstract:
  The current design guidelines of Load and Resistance Factor Design (LRFD) specifies constant ?? values ; for deep foundation design, based on analytical method selected and degree of redundancy of the pier. ; However, investigation of multiple sites in Florida reveals significant variability of soil/rock properties from ; site to site (costal conditions) suggesting the introduction of variable ?? values based on reliability-based design ; approach. Building on previous work (BD545-76) a geostatistical (variograms) approach was developed to ; quantify the spatial uncertainty for site specific conditions. As a result, ?? values are evaluated due to both a ; site’s measured spatial uncertainty and error associated with a particular analytical method. ; This report summarizes subsequent efforts to further expand the applicability of the reliability design to the ; analytical models currently available in the FB-DEEP software program. For the geostatistical analysis, a ; simple yet robust graphical user interface (GUI) was developed, which considers two design scenarios: 1) ; conditioning to nearby boring data, and 2) unconditional mean site data. For either scenario the GUI generates ; thousands of potential data sets, which are evaluated by FB-DEEP to asses mean pile/shaft resistance and ; spatial uncertainty at a pier location. Spatial uncertainty is then combined with the design method error ; associated with the selected FB-DEEP model to asses ??. For demonstration of the application of the GUI, ; standard penetration test (SPT) and laboratory strength data were collected from seven FDOT projects and ; subsequent ?? values were evaluated. The ?? values ranged from 0.3 to 0.7 depending upon amount of ; subsurface data, measure summary statistics, and degree of spatial correlation. The report concludes with ; recommendations (in situ measurements, load testing, etc.) on improving the computed ?? on a site-by-site basis.
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• Format:
  PDF
• Funding:
  BDK75 977-23
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/24474/dot_24474_DS1.pdf
• File Type:
  [PDF - 3.69 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:7d2cb0a786dcd0efa49a2365468056d57521ddcbd93af25f5cf385af508fb2fb