Investigation of negative moment reinforcing in bridge decks.

Details

• Creators:
  Phares, Brent M. ; Jayathilaka, Sameera ; Greimann, Lowell
• Corporate Creators:
  Iowa State University. Bridge Engineering Center
• Corporate Contributors:
  Iowa. Highway Research Board ; Iowa. Dept. of Transportation
• Subject/TRT Terms:
  • Prestressed concrete bridges
  • Bridge decks
  • Reinforcement (Engineering)
  • Live loads
  • Moments (Mechanics)
  • Tensile strength
  • Field tests
  • Finite element method
  • Parametric analysis
  • Transverse cracking
• Publication/ Report Number:
  IHRB Project TR-660;InTrans Project 13-469
• Resource Type:
  Tech Report
• Geographical Coverage:
  Iowa
• Corporate Publisher:
  Iowa State University. Institute for Transportation
• Abstract:
  Multi-span pre-tensioned pre-stressed concrete beam (PPCB) bridges made continuous usually experience a negative live load ; moment region over the intermediate supports. Conventional thinking dictates that sufficient reinforcement must be provided in this ; region to satisfy the strength and serviceability requirements associated with the tensile stresses in the deck. The American ; Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design ; Specifications recommend the negative moment reinforcement (b2 reinforcement) be extended beyond the inflection point. Based ; upon satisfactory previous performance and judgment, the Iowa Department of Transportation (DOT) Office of Bridges and ; Structures (OBS) currently terminates b2 reinforcement at 1/8 of the span length. Although the Iowa DOT policy results in ; approximately 50% shorter b2 reinforcement than the AASHTO LRFD specifications, the Iowa DOT has not experienced any ; significant deck cracking over the intermediate supports. ; The primary objective of this project was to investigate the Iowa DOT OBS policy regarding the required amount of b2 ; reinforcement to provide the continuity over bridge decks. Other parameters, such as termination length, termination pattern, and ; effects of the secondary moments, were also studied. Live load tests were carried out on five bridges. The data were used to ; calibrate three-dimensional finite element models of two bridges. Parametric studies were conducted on the bridges with an ; uncracked deck, a cracked deck, and a cracked deck with a cracked pier diaphragm for live load and shrinkage load. The general ; conclusions were as follows: ;  The parametric study results show that an increased area of the b2 reinforcement slightly reduces the strain over the pier, ; whereas an increased length and staggered reinforcement pattern slightly reduce the strains of the deck at 1/8 of the span length. ;  Finite element modeling results suggest that the transverse field cracks over the pier and at 1/8 of the span length are mainly due ; to deck shrinkage. ;  Bridges with larger skew angles have lower strains over the intermediate supports. ;  Secondary moments affect the behavior in the negative moment region. The impact may be significant enough such that no ; tensile stresses in the deck may be experienced.
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• Format:
  PDF
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/29404/dot_29404_DS1.pdf
• File Type:
  [PDF - 6.62 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:8b6b8ffdc7499d6054fefd2b4c81c8cff706cc921ab97fded9c5684d5a4a1b8f634cc47c7e61d841dffc0b4781f61413ea51fa5dc78881b549a4e84801b7951d