In the February 27, 2010 Chile Earthquake many medium height buildings with structural wall elements collapsed. According to damage surveys one of the factors associated with this structural failure was high flexural compression stress in flange walls. The objectives of this study are to evaluate the provision in the current standard for effective flange width in tension and compression, to clarify high compression stress in flange walls, and clarify the effect of porous sub-standard concrete on effective width. The effective flange width is the width of the flange that influences the lateral forces acting in the plane of the web wall. It is related to stress and strain distribution. As stress and strain distribution is nonlinear, to avoid nonlinearity used uniform distribution of stress and strain. This study is based on experimental testing of three specimens of symmetrical cross-sections walls (H-shaped). The Specimens are designed in accordance with Japanese standard at 1/3 scale acting monotonic or cyclic lateral and axial force. The output the tests is strain distribution in flange walls from each side of each specimen. Data was obtained by installing reinforcement strain gauges in all three specimens, as well as concrete strain gauges in specimen H2 to observe compression. Mechanical properties also analyzed in this study to determine stress-strain relationship models. Bilinear model for steel and trilinear model for concrete used to obtain stress. Effective flange width is calculated by divided the area of stress distribution with the maximum stress.
From these tests it is concluded that effective width should be greater than standard provisions for both tension and compression. In cyclic tests, effective flange width for compression is greater than for tension, before compression is neglected. In general, it is indicated that the use of sub-standard concrete does not significant effect to effective flange width.