Flexural Capacity of Concrete Elements with Unbonded and Bonded Prestressing [Summary]

Details

• Creators:
  Consolazio, Gary ; Potter, William
• Corporate Creators:
  University of Florida. Dept. of Civil and Coastal Engineering
• Corporate Contributors:
  Florida. Department of Transportation. Research Management Center
• Subject/TRT Terms:
  Bridge Design Concrete Bridges Flexural Strength Load And Resistance Factor Design Prestressing Reinforced Concrete Tendons (Materials)
• Resource Type:
  Brief
• Geographical Coverage:
  Florida ; United States
• Edition:
  Research Brief
• Corporate Publisher:
  Florida Department of Transportation
• Abstract:
  Prestressed concrete is widely used in bridge construction and is considered a cost-effective and efficient method of construction. However, durability issues have arisen which have been attributed to poor grouting practice or material performance. To improve durability and facilitate replacement of tendons, bridge construction projects in Florida may now incorporate flexible fillers in lieu of cementitious grout. These structures utilize concrete components with a combination of unbonded tendons and bonded prestressing and/or mild steel reinforcement. Although this is a new design approach in the United States, it has been widely used in European countries. However, the use of mixed reinforcement conditions (i.e., the simultaneous use of unbonded and bonded prestressed reinforcement) in concrete members has structural implications. The flexural behavior of prestressed beams is affected by the presence of unbonded tendons. In the present research, this parameter was characterized by U/T, which is the ratio of unbonded tendon force to total tendon force at flexural capacity; this parameter varies between 0 for fully unbonded sections to 1.0 for fully bonded sections. Strains in unbonded tendons are not compatible with adjacent concrete strains, which makes the strain compatibility approach of capacity calculation non-applicable. In an unbonded tendon, stresses are dependent on the deformation of the entire member as well as tendon geometry. At the ultimate section strength condition, stress for unbonded tendons is lower than for bonded tendons. Current design guidance for prestressed concrete members with mixed reinforcement conditions is based on conservative underestimation of flexural capacity. A major component of this study was therefore the development of improved guidelines for computing the flexural capacity of members with mixed reinforcement conditions.
• Format:
  PDF
• Funding:
  BDV31-977-93
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:23f84f8f0f7bb9275506143b5a6c35cefed36648adce8c8bed583fe9e5c5a03abbe75477ac1776371d7b8813c99699ab78859d8b3f6a84614510213e5ac87f9e
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/75093/dot_75093_DS1.pdf
• File Type:
  [PDF - 168.63 KB ]