A probabilistic comparison of prestress loss methods in prestressed concrete beams

Camber and long-term deflections are directly linked to the loss of prestressing force, a characteristic of all prestressed concrete members. In this investigation, the effects of the inherent variability of the parameters used to estimate prestress loss was studied for two typical bridge beam cases using several prestress loss predictive methods at final service conditions. A parametric study was conducted to assess the general effect of single parameter variation on the calculation of prestress loss. Monte Carlo simulations were used to assess the distribution of prestress loss considering the variability of all parameters simultaneously. Results of the Monte Carlo simulations were also used to evaluate the impact of loss variability on deflection and cracking moment calculations. Results show that the variability of parameters has a notable effect on prestress loss variation and that this variation significantly influences the estimated deflection and cracking moment of prestressed concrete beams. Indeed, the variation in camber between beams cast on the same prestressing bed can be partially explained through the variability of materials and predictive methods used.