Resiliency of Prestressed Concrete Beams Exposed to Fire

Details

• Creators:
  Zhu, Zheda ; Quiel, Spencer E. ; Naito, Clay J.
• Corporate Creators:
  Lehigh University. ATLSS Engineering Research Center
• Corporate Contributors:
  Pennsylvania. Department of Transportation. Bureau of Highway Safety and Traffic Engineering ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  Bridge Decks Case Studies Deflection Failure Failure Analysis Fire Fire-induced Damage Classification Flexure Hazards Heat Transfer I-85 Atlanta Bridge Fire Case Study Numerical Analysis Prestressed Concrete Prestressed Concrete Bulb-T Bridge Girders Shear Strength Shear Tests

  More +
• Publication/ Report Number:
  FHWA-PA-2023-006-E04005 WO 07
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Edition:
  Final Report: Jan. 2022 to May 2023
• Corporate Publisher:
  Pennsylvania. Department of Transportation. Bureau of Planning and Research
• Abstract:
  Numerical simulations were used to investigate the thermo-structural response of simple span prestressed bulb-T concrete bridge girders to fire hazards located underneath the bridge. The approach consists of three steps: (1) fire modeling, (2) heat transfer modeling, and (3) structural modeling. The effects of thermal concrete spalling are accounted for in all analyses via periodic concrete removal by implementing a semi-empirical thermal gradient relationship. The numerical approach is validated via case study for span 30NB of the I-85 bridge near Atlanta, GA that collapsed due to severe fire in 2017. The results of fire characterization and thermo-structural analysis for the prestressed bulb-T girder cross-section (which had harped strands) showed good agreement with the outcomes of the actual event and identified flexural runaway as the primary mode of fire-induced failure. The proposed approach was then applied to a sample bridge provided by PennDOT to evaluate the thermo-structural vulnerability of its prestressed bulb-T girders (with straight strands only). Fire durations longer than 60 minutes had greater likelihood of causing heavy damage to the girder, while flexural runaway was possible after 2.5 hours of exposure. Residual damage was assessed for fires that burned out before the onset of flexural runaway. As expected, fires located underneath the quarter span induced less residual deflection than fires under midspan. Numerical results indicated that the structural fire performance of these prestressed bulb-T girders is associated with strand patterns and section geometry, as well as the intensity and clearance to the fire. Deeper embedment of the prestressing strands within thicker sections of concrete will improve the response of these girders to fire.
• Format:
  PDF
• Funding:
  E04005 WO 07
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:1aa8b6b75e54aa4229996e740d1e29dcccdc8bc00cf9c5965536f258a2ed6a01bef144eae6ec99ab0eb8a3b9b5aed6060607449b20990f36599ef55f5dfa1736
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/89150/dot_89150_DS1.pdf
• File Type:
  [PDF - 8.59 MB ]