EFFECT OF SMALL CIRCULAR OPENING ON THE SHEAR ANDFLEXTURAL BEHAVIOR AND ULTIMATE STRENGTH OFREINFORCED CONCRETE BEAMS USING NORMAL AND HIGHSTRENGTH CONCRETE

摘要

In this investigation the effect of small circular opening on the shear and flexural and ultimatestrength of beams made by normal and high strength concrete have been studied. The mainfactors of this test are the changes of diameter, the position of opening and the type and locationof reinforcement around the opening and changes in the strength of concrete. In this investigation9 beams by using normal concrete and 5 beams by using high strength concrete were made andtested. One beam was solid and filled with normal concrete and was used as reference forcomparison with other beams with an opening. The testing beams have been loaded as simplebeam 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 ultimatestrength increased and patterned of cracking as well as mode of failure of the beam changed. Theeffect of concrete strength depended on parameters such as diameter and the position of opening. In orderto control the cracks and restrain their width, it is better to use diagonal shear reinforcement. Forincreasing the ultimate shear strength of the beam usage of diagonal reinforcement and stirrups in top andbottom of opening is recommended. At the end the results of tests were compared with equation of somecodes.