Microplane Model for Concrete: II: Data Delocalization and Verification

Abstract

The new microplane model developed in the preceding companion paper is calibrated and verified by comparison with test data. A new approximate method is proposed for data delocalization, i.e., decontamination of laboratory test data afflicted by localization of strain-softening damage and size effect. This method, applicable more generally to any type of constitutive model, is based on the series-coupling model and on the size-effect law proposed by Bažant. An effective and simplified method of material parameter identification, exploiting affinity transformations of stress-strain curves, is also given. Only five parameters need to be adjusted if a complete set of uniaxial, biaxial, and triaxial test data is available, and two of them can be determined separately in advance from the volumetric compression curve. If the data are limited, fewer parameters need to be adjusted. The parameters are formulated in such a manner that two of them represent scaling by affinity transformation. Normally only these two parameters need to be adjusted, which can be done by simple closed-form formulas. The new model allows good fit of all the basic types of uniaxial, biaxial, and triaxial test data for concrete.