Time-Dependent Finite Element Analysis of Prestressed Concrete Beams

Based on ABAQUS general finite element software, UMAT Fortran subroutine is compiled to estimate the long-term deflections of prestressed concrete beams. And the calculated values using the software corresponded well with the laboratory results. By generalizing key parameters impact on long−term deflections of prestressed concrete beams, time-dependent finite element analysis was conducted. Taking type of concrete, concrete grade, age of concrete when the initial stress was applied, effective prestressing tensile force, type of prestressed tendon, reinforcement ratio for nonprestressed compression steel reinforcement and mean relative humidity into account, a simplified formula for long-term deflection of prestressed concrete beam at midspan was suggested. And the calculated values using the suggested formula corresponded well with the laboratory and filed test results. The errors were within 10%. However, the calculated errors using the common codes were larger, which resulted in the unsafe values.