Evaluation of Torsional Load Transfer for Drilled Shaft Foundations

Despite the prevalence of the use of drilled shafts for the support of traffic signal and signs along state highways, relatively little is known about the torsional load transfer between the structure and soil providing its support. A review of literature indicated that just three full-scale torsional loading test series have been conducted, and these did not report the observation of the torsional load transfer. To help address this gap in knowledge, two instrumented test shafts, which were designed to support signal pole type SM3 based on Oregon Department of Transportation (ODOT) Standard Drawing TM653, were constructed to evaluate the torsional capacity and load transfer of these shafts at full-scale at the Oregon State University (OSU) Geotechnical Engineering Field Research Site (GEFRS). Two shafts were constructed: one shaft designated as the torsion test drilled shaft with production base (TDS) was constructed using the dry method, whereas another shaft designated as the torsional drilled shaft with frictionless base (TDSFB) was constructed by placing bentonite chips at the bottom of the cavity to create near-zero base shear condition. Monotonic, quasi-static and cyclic loading tests were performed using two hydraulic actuators and a displacement couple. The imposed rotation and corresponding torque was monitored using stringpotentiometers and load cells, respectively. Embedded strain gages were installed on both test shafts over five depths to measure shear strains and reveal the load transfer of the drilled shafts in torsion. The torsional load transfer is back-calculated from the instrumentation data and described in detail. Existing design procedures for predicting torsional capacity of drilled shafts were investigated. The Colorado Department of Transportation (CDOT) Design Method and the Florida District 7 Method, both of which can treat layered cohesive and cohesionless soils, were selected to estimate the torsional capacities of the test shafts and compared with the test results. However, these design methods appeared to over- and under-predict the torsional capacity, respectively, indicating the need for the development of improved methods for assessing torsional capacity.

  • Record URL:
  • Corporate Authors:

    Oregon State University, Corvallis

    Department of Biological and Ecological Engineering
    Corvallis, OR  United States 

    Oregon Department of Transportation

    Research Section
    555 13th Street NE
    Salem, OR  United States  97301

    Federal Highway Administration

    400 Seventh Street, SW
    Washington, DC  United States  20590-0003
  • Authors:
    • Stuedlein, Armin W
    • Barbosa, Andre R
    • Li, Qiang
  • Publication Date: 2016-5

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Maps; Photos; References; Tables;
  • Pagination: 159p

Subject/Index Terms

Filing Info

  • Accession Number: 01599210
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-OR-RD-16-14
  • Contract Numbers: SPR 304-701
  • Files: TRIS, ATRI, USDOT, STATEDOT
  • Created Date: May 18 2016 11:41AM