Numerical investigation on primary and secondary cracks in thick concrete members

This study investigates the crack formation process in thick reinforced concrete members subjected to imposed deformations, focusing on the development of secondary cracks in addition to geometrically set primary cracks. A validated nonlinear fracture-plastic finite element model is used to analyze the influence of reinforcement layout, member thickness, and restraint conditions. The results show that the occurrence of secondary cracks depends primarily on the ratio of member thickness (Formula presented.) to surface distance of the application point of tensile force on the cross-section (Formula presented.), with thresholds of (Formula presented.) for single-layer and (Formula presented.) for double-layer reinforcement. Even though the current engineering model used in the MRZ guideline still yields appropriate reinforcements amounts for crack control in very thick concrete members, the study reveals that refinements of current design models may be necessary for structures with increased performance demands. In addition, the study highlights the importance of accurate bond modeling in nonlinear simulations.