MEASUREMENT OF THE RATIO GF/GF FOR NUMERICAL ANALYSIS OF CONCRETE STRUCTURES

Abstract

THE FRACTURE ENERGIES GF , OBTAINED BY THE WORK-OF-FRACTURE METHOD, AND GF , OBTAINED BY THE SIZE EFFECT METHOD, ARE TWO DIFFERENT MATERIAL CHARACTERISTICS. THE FRACTURE ENERGY GF REPRESENTS THE AREA UNDER THE COMPLETE LOAD-DEFLECTION CURVE, AND THE FRACTURE ENERGY GF REPRESENTS THE AREA UNDER THE INITIAL TANGENT OF THE SOFTENING CURVE. IT IS POSSIBLE TO SHOW THROUGH NUMERICAL SIMULATION OF NOTCHED FRACTURE SPECIMENS THAT, AT MAXIMUM LOAD, THE COHESIVE CRACK WILL NEVER BE OPENED ENOUGH FOR THE TAIL STRESSES OF THE SOFTENING CURVE TO OCCUR. CONSEQUENTLY, GF DETERMINES THE MAXIMUM LOAD OF MOST CONCRETE STRUCTURES IN PRACTICE. NEVERTHELESS, MANY ¯NITE ELEMENT PROGRAMS REQUEST THE COMPLETE SOFTENING CURVE CORRESPONDING TO THE FRACTURE ENERGY GF . IN THIS CASE, THE RATIO GF=GF IS WORTHY TO BEINVESTIGATED BECAUSE THE ENERGY GF IS EASIER TO BE OBTAINED THROUGH THE EXPERIMENTS. IN THIS WORK, THE CORRELATION BETWEEN GF AND GF IS INVESTIGATED. THE RESULTS OBTAINED IN AN EXPERIMENTAL PROGRAM, DEVELOPED AT PUC-RIO IN ORDER TO STUDY THE FRACTURE PROPERTIES OF IGH-PERFORMANCE CONCRETE, ARE PRESENTED AND COMPARED WITH SOME RESULTS SHOWED IN THE LITERATURE. A NUMERICAL EXAMPLE ILLUSTRATES THE DEVELOPMENT OF THE COHESIVE ZONE DURING SPECIMEN TESTING.