Implementation and Application of Fracture Mechanics Models for Concrete Structures

Doktorsavhandling, 1996

Two numerical models for simulation of concrete cracking and bond slip have been implemented and applied in various comparative analyses. Both models were implemented in the commercial finite element system ABAQUS. The concrete crack model was based on the enhanced strain concept, while the interface model was developed and formulated to simulate the bond slip behaviour at the release of the prestressing force in the strands in prestressed hollow core slabs. The concrete crack model was implemented as an element model using C++ and was realised using three abstract data types. This method of implementation not only made it possible to get a well structured code but also laid the foundation for future implementations of more complex element types. The interface model (simulating bond slip) was implemented as a constitutive model using Fortran 77. To investigate the capability of the models, they were applied in several comparative analyses of laboratory experiments. For the concrete crack model three different experiments were studied: a pull-out test, a shear test and a combined tension-shear test. The model proved to be reasonably good at simulating the response of the different tests. Before using the interface model for its intended purpose, i.e., modelling the release of the prestressing force in prestressed hollow core slabs, numerous comparative analyses of laboratory experiments were conducted aiming at verifying the capacity of the model. This investigation showed that the interface model did reproduce reasonably well the behaviour observed in the experiments. After the series of comparative analyses, the interface model was used in several analyses of hollow core slabs, in an effort to establish failure limits of influential parameters of the slabs.