1. Introduction
This paper aims at improving a strength reduction factor r3 related to opening height for RC shear walls in the AIJ design standard1). FEM analyses were conducted to simulate experimental behavior/performance of three shear wall specimens without/with vertical aligned openings. Based on the analytical results, r3 was verified through investigating shear contributions of the wall components. Moreover, a new strength reduction factor newr3 was proposed to improve the accuracy of the original r3.
2. Outline of experimental study on RC shear walls with openings2)
The specimens were designed with different opening configurations: Specimen W0 without opening, Specimen W1 with single-aligned openings, and Specimen W2 with double-aligned openings. As a result, it was experimentally verified that the lateral strengths estimated for the specimens with openings based on r3 overestimated the maximum strengths obtained from the tests. Therefore, FEM analyses of the specimens were performed mainly to clarify why the overestimations were caused.
3. FEM analyses
Two-dimensional FEM analyses were conducted for the specimens to simulate the experimental behavior/performance. The analytical results of all specimens, in particular, the shear force vs. drift angle relationships and damage developments, up to R of 0.5 x 10-2 rad. showed good agreements with the experimental results. Moreover, contributions of the wall components to the overall lateral strengths were investigated and compared with the estimations by r3. Consequently, the lateral strengths estimated for the specimens with openings overestimated the experimental maximum strengths. It was concluded that the overestimations were caused by overestimations on the flexural resistances of the partial walls divided by the openings.
4. Proposal for improving the strength reduction factor related to opening height
A new strength reduction factor newr3 was proposed with a flexural strength reduction index α for this type of wall, in particular the wall with a boundary column on the tensile side. The index α considered reduction of an arm length between coupled forces on the wall bottom from an assumption in the original r3. The estimations for the ultimate strengths of the above specimens using newr3 showed good agreements with the experimental results.
5. Conclusions
Major findings from the present study are summarized to show the appropriateness of the proposed strength reduction factor newr3 for RC shear walls with vertically aligned openings.
