Model B3.1 for multi-decade concrete creep and shrinkage: Calibration by combined laboratory and bridge data

Recent comparisons with numerous data on excessive multi-decade deflections of segmentally erected prestressed box girder bridges revealed the need for recalibration of RILEM B3 model for creep and shrinkage of concrete. With this aim, data from 69 large bridge spans have already been collected at the time of writing but a joint effort of Northwestern University and RILEM TC-MDC. The NU-ITI Laboratory Database has been updated by new data from JSCE, Japan, and a large collection of datasets for modern concretes containing admixtures. Extensive sensitivity analysis of the dependence of model B3 parameters on the material composition and strength is presented. The laboratory data are weighted, with emphasis on long-time tests, particularly the 30-year laboratory tests of Brooks. Combined optimization of both the bridge and laboratory data leads to better formulae of model B3.1 for predicting creep and shrinkage parameters from material strength and composition.