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:
  Bridge Decks Field Tests Finite Element Method Live Loads Moments (Mechanics) Parametric Analysis Prestressed Concrete Bridges Reinforcement (Engineering) Tensile Strength 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.
  
  
• Format:
  PDF
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:8b6b8ffdc7499d6054fefd2b4c81c8cff706cc921ab97fded9c5684d5a4a1b8f634cc47c7e61d841dffc0b4781f61413ea51fa5dc78881b549a4e84801b7951d
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/29404/dot_29404_DS1.pdf
• File Type:
  [PDF - 6.62 MB ]