Special Truss Moment Frame Component Test 15 - 2C12x20.7 (RBS)

Specimen 15 was made of double channels C12x20.7 that the width of the flanges was cut off in order to reduce the moment capacity by 20%. This specimen employed the same idea of reduced beam section (RBS) used in wide flange sections, hence; 2C12x20.7 with reduced beam section (RBS). Like Specimen 14, this specimen was tested under cyclic loading with the test setup representing the chord members in the special segment of a prototype STMF. This prototype STMF specimen will utilize buckling restrained braces (BRBs) to enhance its behavior. In order to avoid heavy reinforcement of the members outside special segment which have to remain elastic, RBS will be used to reduce the special segment chord members’ capacity. In order to reduce bulging encountered in Specimen 14, this specimen employed one pair of stiffeners that bisect the distance between the end of the horizontal welds, connecting the channels to the gusset plate, and the first stitches. The Specimen exhibited a stable behavior under cyclic loading up to 1.5% story drift or 3.61% member drift. The use of stiffener may prevent plastic flow in the flanges of the channels and caused premature fractures of the channels after the 2nd cycle of 1.5% story drift was completed. When comparing hysteretic behavior of specimens 14 and 15, it can be seen that Specimen 14 exhibited a more ductile behavior than Specimen 15. Although, maximum moment capacity of Specimen 15 was noticeably higher than that of Specimen 14.