STRUCTURAL RESISTANCE FACTORS FOR DRILLED SHAFTS CONSIDERING CONSTRUCTION FLAWS. IN: CURRENT PRACTICES AND FUTURE TRENDS IN DEEP FOUNDATIONS

The design of any foundation should involve consideration of the structural ultimate limit state. In the case of drilled shafts, this usually involves the use of methods published in the various structural design codes for the design of super-structural beam-columns. However, drilled shafts are cast-in-situ elements that are subject to a much more uncertain construction history than an element in the superstructure. Voids, soil inclusions, offset and corroded reinforcing steel, and weakened concrete can exist in the finished product without the knowledge of the designer. Large voids and soil inclusions, occupying more than 15% of the cross-sectional area of the shaft, can usually be detected with state-of-the-practice nondestructive evaluation methods. In such case the shaft is repaired or replaced if the defect is in the critical location. However, smaller voids, corroded and offset steel, and slightly weak concrete cannot be detected reliability. The premise of this paper is that the effects of such flaws must be included in the design process. A series of experimental and analytical studies were performed to evaluate appropriate structural resistances for drilled shafts that have some probability of containing undetectable construction flaws. The tests included field tests on large-scale drilled shafts constructed with small flaws, structural laboratory tests on 0.305-m-diameter modes and on 0.76-m diameter specimens to evaluate scale effects. The laboratory and field tests were modeled using a calibrated section analysis model in order to extend the experimental results over a larger spectrum of flaws and flaw combinations than were feasible in the experimental study. A simple probability model was then used to evaluate the final structural resistance factors, based on the frequency of flaws observed at selected field sites, reported in the literature, and as represented via expert opinions. This paper summarizes the probabilistic aspects of the research and proposes structural resistance factors for use in evaluating axial and bending of drilled shafts based on simple modifications of existing code equations for structural beam columns. The recommended factors multiply the capacities computed from nominal structural design equations.

• Record URL:
  https://doi.org/10.1061/40743(142)10
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0784407436
• Corporate Authors:

  American Society of Civil Engineers

  Geo-Institute
  Reston, VA  United States  20191-4400
• Authors:
  • O'Neill, M W
  • Sarham, H A
• Conference:
  • Contributions in Honor of George G. Gobel
  • Location: Los Angeles California, United States
  • Date: 2004-7-27 to 2004-7-31
• Publication Date: 2004-7

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 166-185
• Monograph Title: CURRENT PRACTICES AND FUTURE TRENDS IN DEEP FOUNDATIONS
• Serial:
  • ASCE Geotechnical Special Publication
  • Issue Number: 125
  • Publisher: American Society of Civil Engineers

Subject/Index Terms

• TRT Terms: Beams; Cast in place structures; Columns; Concrete; Design; Drilling; Experiments; Flaw detection; Foundations; Nondestructive tests; Resistance (Mechanics); Shafts (Machinery); State of the practice; Structural analysis
• Subject Areas: Design; Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00987888
• Record Type: Publication
• ISBN: 9780784407431
• Files: TRIS
• Created Date: Mar 9 2005 12:00AM