Improving the accuracy of camber predictions for precast pretensioned concrete beams.

Details

• Creators:
  Honarvar, Ebadollah ; Nervig, James ; He, Wenjun ; Sritharan, Sri ; Rouse, Jon Matt
• Corporate Creators:
  Iowa State University. Bridge Engineering Center
• Corporate Contributors:
  Iowa. Highway Research Board
• Subject/TRT Terms:
  • Curvature
  • Precast concrete
  • Prestressed concrete
  • Beams
  • Accuracy
  • Creep
  • Shrinkage
  • Finite element method
  • Thermal analysis
• Publication/ Report Number:
  IHRB Project TR-625;InTrans Project 11-390
• Resource Type:
  Tech Report
• Geographical Coverage:
  Iowa
• Corporate Publisher:
  Iowa State University. Institute for Transportation
• Abstract:
  The discrepancies between the designed and measured camber of precast pretensioned concrete beams (PPCBs) observed by the ; Iowa DOT have created challenges in the field during bridge construction, causing construction delays and additional costs. This ; study was undertaken to systematically identify the potential sources of discrepancies between the designed and measured camber ; from release to time of erection and improve the accuracy of camber estimations in order to minimize the associated problems in ; the field. ; To successfully accomplish the project objectives, engineering properties, including creep and shrinkage, of three normal ; concrete and four high-performance concrete mix designs were characterized. In parallel, another task focused on identifying the ; instantaneous camber and the variables affecting the instantaneous camber and evaluated the corresponding impact of this factor ; using more than 100 PPCBs. Using a combination of finite element analyses and the time-step method, the long-term camber was ; estimated for 66 PPCBs, with due consideration given to creep and shrinkage of concrete, changes in support location and ; prestress force, and the thermal effects. ; Utilizing the outcomes of the project, suitable long-term camber multipliers were developed that account for the time-dependent ; behavior, including the thermal effects. It is shown that by using the recommended practice for the camber measurements ; together with the proposed multipliers, the accuracy of camber prediction will be greatly improved. Consequently, it is expected ; that future bridge projects in Iowa can minimize construction challenges resulting from large discrepancies between the designed ; and actual camber of PPCBs during construction.
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• Format:
  PDF
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/29403/dot_29403_DS1.pdf
• File Type:
  [PDF - 4.73 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:4986a6d9f4b9a99891301feb10edc4fd196f52975ae0c9c7fd295961763da0d40a8e2dea2e142ff9dd5b9bac1c65da3410c3ed84148ca443c20609f740c6461d