A THREE-DIMENSIONAL PHOTOELASTIC INVESTIGATION OF STRESSES AND CRACKS FORMED IN CONCRETE AROUND DEFORMED REINFORCING BARS

When deformed bars are used as tensile reinforcement, the characteristics of the cracks formed in the concrete around the reinforcement are basically different from those of cracks formed around plain bars. These cracking characteristics of deformed bars influence or even define the bond mechanism between deformed bars and concrete. For rational design of structures subjected to unusual loading such as earthquakes, it is desirable to know the state of stress in concrete around the reinforcing ribs and, also, to predict the intensity and pattern of cracks formed.;Stress freezing technique of photoelasticity has been employed to evaluate the three-dimensional principal state of stress in concrete around a deformity in tensile and pull-out tests. Stress trajectories produced from the results of experiments completely predict the crack pattern in concrete and agree with test results on concrete. Stress intensity factors due to transverse and splitting cracks were calculated combining linear elastic fracture mechanics and three-dimensional photoelasticity. A new shape of reinforcing rib is introduced and experimented along with the conventional shape in order to compare and study the difference in stress states and crack patterns.