A simplified method for prediction of long-term prestress loss in post-tensioned concrete bridges.

Details

• Creators:
  Youakim, Samer ; Karbhari, Vistasp M.
• Corporate Creators:
  University of California, San Diego. Dept. of Structural Engineering
• Subject/TRT Terms:
  Concrete Bridges Maintenance And Repair Post-tensioned Prestressed Concrete Construction
• Publication/ Report Number:
  UCSD / SSRP-06/21
• Resource Type:
  Tech Report
• Geographical Coverage:
  California
• Corporate Publisher:
  California. Department of Transportation
• Abstract:
  Creep and shrinkage of concrete and relaxation of prestressing steel cause time-dependent changes in
  
  the stresses and strains of concrete structures. These changes result in continuous reduction in the
  
  concrete compression stresses and in the tension in prestressing steel. Reasonably accurate estimate
  
  of the long-term prestress losses are needed to avoid any serviceability problems of the structure (due
  
  to cracking and/or excessive deflection). An analytical method is presented to predict the long-term
  
  prestress losses in continuous cast-in-place post-tensioned bridges. The method is based on the basic
  
  principles of solid mechanics and satisfies the requirements of equilibrium and compatibility of the
  
  bridge cross section. The proposed method for a section in concrete girder reduces to a single
  
  equation with three coefficients, which are functions of the modulus of elasticity and creep
  
  coefficient of concrete, location and amount of prestressing and non-prestressed steel, and geometry
  
  of the cross section. To expedite the use of the method and to make it more appealing to practicing
  
  engineers, design aids are provided to estimate these three coefficients. The method is further
  
  extended to continuous bridge girders by using the force method to calculate the change in
  
  connecting moments at intermediate supports and hence the increase or decrease in prestressing
  
  losses. The predictions of the proposed method are compared with the current provisions of design
  
  standards and codes of practice. It is shown that the present empirical equations of the bridge
  
  standards can overly underestimate or overestimate the long-term prestress losses, depending on the
  
  concrete creep and shrinkage properties as well as prestressing and non-prestressed steel ratios.
  
  
• Format:
  PDF
• Funding:
  59A0337
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:c7e7718eccd4a043fadfe9c47330aa11c4b30445e1df515052ef2dffa9569ec1
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/27525/dot_27525_DS1.pdf
• File Type:
  [PDF - 820.68 KB ]