Special Truss Moment Frame Component Test 4 - 2C12x20.7

Special truss moment frame component test 4, made of double channels 2-C12x20.7, was tested under cyclic loading. The test setup is a representative of half of the chord in the special segment of the prototype special truss moment frame. In experiment 3, the weld between the channels and the closest stitches to the gusset plate fractured due to the web of the channels in the plastic hinge zone bulged out. As a result, the orientation of the stitches at this particular location and of the next pair of stitches was made horizontal instead of vertical as normally seen in a conventional stitch. In addition, a stiffener was added on each channel web in the middle between the locations of the stiffeners appeared in experiment 3 in order to minimize bulging. This resulted in 3 pairs of stiffeners near the plastic hinge zone at the interval of 4.25 in. center-to-center. In addition, 2 cycles of 2.38% story drift were added into the loading protocol. Minor flange local buckling, bulging, and weld crack were observed at 1.5% story drift. Flange and web local buckling, bulging, and weld crack progressed as the test continued and strength started to slightly drop at 2.38% story drift. By using 3 pairs of stiffeners, bulging was confined within the first two pairs of stiffeners near plastic hinge and web local buckling occurred at several spots. The hysteretic behavior of the specimen was stable and ductile. The test was terminated at 2.75% story drift or 8.67% member drift when the web and the flange of the west channel fractured.