Prestress losses assumed for bridge girder design and deflection analyses are dependent on the concrete modulus of\r\nelasticity (MOE). Most design specifications, such as the American Association of State Highways and Transportation Officials\r\n(AASHTO) bridge specifications, contain a constant value for the MOE based on the unit weight of concrete and the concrete\r\ncompressive strength at 28 days. It has been shown in the past that that the concrete MOE varies with the age of concrete. The\r\npurpose of this study was to evaluate the effect of a time-dependent and variable MOE on the prestress losses assumed for bridge\r\ngirder design. For this purpose, three different variable MOE models from the literature were investigated: Dischinger (Der\r\nBauingenieur 47/48(20):563ââ?¬â??572, 1939a; Der Bauingenieur 5/6(20):53ââ?¬â??63, 1939b; Der Bauingenieur, 21/22(20):286ââ?¬â??437,\r\n1939c), American Concrete Institute (ACI) 209 (Tech. Rep. ACI 209R-92, 1992) and CEB-FIP (CEB-FIP Model Code, 2010). A\r\ntypical bridge layout for the Dallas, Texas, USA, area was assumed herein. A prestressed concrete beam design and analysis\r\nprogram from the Texas Department of Transportation (TxDOT) was utilized to determine the prestress losses. The values of the\r\ntime dependent MOE and also specific prestress losses from each model were compared. The MOE predictions based on the ACI\r\nand the CEB-FIP models were close to each other; in long-term, they approach the constant AASHTO value. Dischingerââ?¬â?¢s model\r\nprovides for higher MOE values. The elastic shortening and the long term losses from the variable MOE models are lower than that\r\nusing a constant MOE up to deck casting time. In long term, the variable MOE-based losses approach that from the constant MOE\r\npredictions. The Dischinger model would result in more conservative girder design while the ACI and the CEB-FIP models would\r\nresult in designs more consistent with the AASHTO approach
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