EFFECT OF SMALL CIRCULAR OPENING ON THE SHEAR AND FLEXTURAL BEHAVIOR AND ULTIMATE STRENGTH OF REINFORCED CONCRETE BEAMS USING NORMAL AND HIGH STRENGTH CONCRETE

摘要

In this investigation the effect of small circular opening on the shear and flexural and ultimate strength of beams made by normal and high strength concrete have been studied. The main factors of this test are the changes of diameter, the position of opening and the type and location of reinforcement around the opening and changes in the strength of concrete. In this investigation 9 beams by using normal concrete and 5 beams by using high strength concrete were made and tested. One beam was solid and filled with normal concrete and was used as reference for comparison with other beams with an opening. The testing beams have been loaded as simple beam with two concentrated and symmetrical load. In the beams made of ordinary concrete, when the diameter of opening exceeded the 1.3 of depth of the beam, the reduction of ultimate strength increased and patterned of cracking as well as mode of failure of the beam changed. The effect of concrete strength depended on parameters such as diameter and the position of opening. In order to control the cracks and restrain their width, it is better to use diagonal shear reinforcement. For increasing the ultimate shear strength of the beam usage of diagonal reinforcement and stirrups in top and bottom of opening is recommended. At the end the results of tests were compared with equation of some codes.