Abstract
This paper describes experimental results of reinforced concrete shear walls with a opening. Testing models consist of three series M-I, M-II and M-III, Each of them has the different experimental subject. The series of M-I was tested for the evaluations of the reduction in the stiffness and in the strength of the wall models which have one opening but different in scale, and M-II series with one and the same scale opening for the evaluation of the effects of the diagonal reinforcements on the edge of opening. M-III series was tested for the evaluation of the effects of the amount of shear reinforcements in walls. The results from these tests are summarised as follows. (1) In spite of various type of models, all skelton curves of them have a transitional peculiar point on log-log coordinantes and the points have nearly the same values of τ/F_c and R=δ/h. It is evaluated that τ/F_c≒0.08〜0.1 and R≒0.7〜0.8×10^<-3> radian. At the state under load corresponded to those poinst, all cracks on the wall have still hair-breadth. (2) Both reinforcements with diagonal bars and with the steel plate on the edges around the opening were unable to contribute to increasing the initial strength. But diagonal reinforcements take effect for the control of diagonal tension crack caused by stress concentration at the corners and the steel plate around opening is useful to keep the surrounding area of opening having no crack until final. (3) Ultimate failure of wall is not caused by the stress concentration around opening but by the distributed shear stress at both sides of opening. Therefore, the increase of shear reinforcements, a_w・σ_y, make linearly the ultimate strength of wall raise. (4) A large amount of shear reinforcements, that is, double arrangement with closed spacing bars in wall are useful to keep the core concrete of the wall from failure. (5) Our experimental results of the walls with considerably high shear reinforcement show slightly lower strength as usual, concerning the lowering ratio of ultimate strength of walls depend upon the increase of opening area.
