Estimation of beam prestress by deflection and strain measurements

Laboratory test of reinforced and prestressed concrete structures have been used widely to explore the behavior of reinforced and prestressed concrete components and structures; Such tests are often time-consuming and costly. However, numerical models have been shown to compare favorably with experiments. Thus, computations are viewed nowadays as efficient alternatives to tests, time-wise and cost-wise. In the research reported in this thesis, finite-element model were used in a study of pretressed structural components in order to correlate levels of pretension with deflection and strain measurements. The two main objectives were to develop a suitable finite element model of prestressed concrete beams and to forecast beam prestension on the basis of deformations resulting from specified simple load, e.g., a uniformly distributed transverse load. A commercial finite-element analysis package (ANSYS 12) was used to set up, use and evaluate the computational model. Furthermore, a finite-difference model was employed in order to ascertain the validity of ANSYS results by comparison with engineering beam theory taking into account the applied pretension. This study demonstrates the potential usefulness of deflection and strain measurements as indicators of the pretension applied or remaining in prestressed concrete beams.