Load rating and retrofit testing of bridge timber piles subjected to eccentric loading.

Details

• Creators:
  Caiza, Pablo ; Shin, Moochul ; Andrawes, Bassem
• Corporate Creators:
  Illinois Center for Transportation ; University of Illinois at Urbana-Champaign. Department of Civil and Environmental Engineering
• Corporate Contributors:
  United States. Federal Highway Administration
• Subject/TRT Terms:
  • Piles (Supports)
  • Load factor
  • Fiber reinforced polymers
  • Retrofitting
  • Bending moments
  • Live loads
  • Timber
  • Finite element method
  • Highway bridges
• Publication/ Report Number:
  FHWA-ICT-12-014;ICT-12-014;UILU-ENG-2012-2023
• Resource Type:
  Tech Report
• Geographical Coverage:
  Illinois
• Corporate Publisher:
  Illinois. Department of Transportation
• Abstract:
  This report first evaluated the load rating procedure currently in use by the Illinois Department of Transportation (IDOT) for rating timber ; piles supporting multiple-span, simply supported bridges. For simplicity, these piles are often rated under concentric loads, and the effect ; of bending in the piles is neglected. Recent studies have shown, however, that under highly eccentric live loads, the effect of bending ; moments in the piles is of great importance and could have an impact on the piles’ load rating. The report proposed an alternative ; structural load rating method for timber piles based on the National Design Specification for Wood Construction (NDS), which took into ; consideration the effect of combined compression-flexure behavior of piles. This method was used to conduct a parametric study to ; investigate the effect of several geometric and structural parameters on the load rating of bridge timber piles using 3-D finite element ; models of concrete deck bridges supported on groups of timber piles. The results showed that the proposed load rating method produced ; significantly lower ratings for piles with moderate to high levels of deterioration, as compared to the ratings obtained using the ; conventional approach. Among the studied parameters, the length of piles was found to have the most significant impact on the load ; rating of the piles. The report also presents a study on examining a fiber reinforced polymer (FRP)-based retrofitting method for timber ; piles subjected to combined axial and bending loading. A total of twenty pile specimens were tested in the study, four under compressiononly load and sixteen under compression-flexure load. Each specimen was tested twice, before and after retrofitting with glass FRP ; (GFRP) or carbon FRP (CFRP) sheets. To assess the impact of realistic field conditions, different details of the FRP retrofit technique ; were investigated, including using mortar shell, introducing a mortar-filled wedge in the tested specimen to mimic the effect of decayed ; wood, and “posting” the piles with nails instead of steel drift pins. The test results showed that the strength of the tested specimens using ; the proposed GFRP retrofit technique was fully recovered or even enhanced compared to that of the unretrofitted specimens, regardless ; of the retrofit details adopted in the tests. On average, specimens retrofitted with GFRPs showed strength 10% greater than that of ; unretrofitted specimens. The behavior of CFRP sheets, however, was less satisfactory due to the small thickness of the CFRP shell used ; as a result of the high strength of CFRP compared to GFRP. It was also found from the study that using mortar shell along with FRP ; sheets helped enhance the stiffness of the retrofitted pile. Finally, linear regression analysis was conducted on the test data to develop a ; formula that could be used for the design of FRP retrofit for bridge timber piles subjected to axial-bending loading.
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• Format:
  PDF
• Funding:
  R27-82
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/26724/dot_26724_DS1.pdf
• File Type:
  [PDF - 2.86 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:2fb097dd4c39043cc1fc9c04231a7cbe54b999b9db9444e94fb2ce5375b1a4c860a2bcb2d79c9ba5e81366b0fea911f7ee70c31c5e1a575af5dd2fdacda6619f