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Six squat walls were tested under cyclic loading to investigate the effects of flanges and high-strength reinforcing bars on the shear strength. Test parameters were the grade of reinforcing bar, wall geometry, and reinforcement ratio. The strength and deformation capacity of the specimens with high-strength reinforcing bar were comparable to that of normal-strength reinforcing bar specimen with identical design strength. The shear strength of flanged walls was two times the nominal shear strength of ACI 318-19, regardless of the web reinforcement ratios. The test results showed that the vertical reinforcing bar and concrete in the flanges contributed to the shear strength. Shear strength was calculated using a multiple shear panel model, which included the effect of flanges. The results showed that the strength contribution of the flanges accounted for 40% of the overall shear strength. This result indicates that for the economical design of squat walls, the effect of flanges can be considered.
Keywords: cyclic loading tests; flanged walls; high-strength reinforcing bar; shear strength; squat walls.
Existing experimental studies for squat walls (heightto-length ratio < 1.0)1-21 have focused on the evaluation of shear strength according to failure modes.1,20,22-29 While the majority of existing studies have focused on isolated rectangular walls,2,16-20,22,23,26,27,30-33 the reality is that many buildings have walls with flanges. In particular, safety-related auxiliary buildings in nuclear power plants (NPPs) consist of grid-type squat walls. In this case, the shear strength contribution of flanges may be significant. If the shear strength contribution of flanges is considered for the design of walls, the constructability and economy of walls can be improved, particularly for NPPs, using the high reinforcement ratio of large-diameter reinforcing bars. Further, in the recent version of ACI 318 (ACI 318-1934), the use of a high-strength reinforcing bar (Grade 690 MPa [100 ksi]) was permitted for the shear design of walls. Thus, if in addition to the effect of flanges, the effect of a high-strength reinforcing bar is considered, the economy and constructability can be further improved. For this reason, existing studies have conducted tests on the use of high-strength reinforcing bars in walls.16,18,21,35 The results demonstrated that the tested shear strength of walls with high-strength reinforcing bars was equivalent to that of normal-strength reinforcing bar walls provided that the design shear strength...