Seismic Responses of Special Concentrically Braced Frame With In-Plane Buckling Brace
Date Issued
2009
Date
2009
Author(s)
Lien, Yu-Chyun
Abstract
For resisting earthquakes, the special concentrically braced frames dissipate energy by the braces yielding tension and buckling in compression. The tradition design of connection of gusset plates and braces make the braces buckle out-of-plane. The out-of-plane deformation can become 40cm in previous tests. The buckled braces probably damage the wall covering the braces even people or equipment nearby. The research transfer the braces buckling direction into in-plane by the knife plates, and test in a two story real size fame specimen to investigate the responses of the braces buckling in-plate. Then build a FEM model by ABAQUS to simulate the responses of specimen. Hope to establish a design procedure of frames in braces buckling in-plane. And use FEM model instead of real size test to reduce the cost of time and money.he specimen in this research have been used for 3 TCBF tests and a BRBF test. Only changed the gusset plates and braces, and kept the frame remain. The specimen is 6.66m tall and 6.7m wide. The arrangement of braces is X type. The braces is H175x175x11x7.5, same as the second test of TCBF. Because of additional knife plates, the braces length in this test is a little shorter than the second TCBF test. The gusset plate design use the UFM instead of ellipse bending design method. The actuator act on the middle of roof slab to proceed cyclic test. n this test, the two braces in east side buckled in sequence, then the two braces in west buckled after a long time. Large nonlinear strain happened on the local buckling area of the two east braces. Lead to the in-plane buckling braces fractured earlier than the second test of TCBF. The reason may be the shorter brace length result in poor ductile deformation behavior. In research of a improved design method, the concept of balance design is used to allow the knife plates, gusset plates and braces develop non-elastic behavior but make sure the fracture only happen in the braces. The balance design not only improves the system ductility but also the economy of gusset plates and knife plates. The research improve the braces buckling behavior by elongate the braces. Design the rectangular shape gusset plates using generalized UFM to break the shape restrain of original UFM and reduce the cutting cost. Consider to move the net section issue from the connection of braces and knife plates to the cross section of knife plates and gusset plates. The weld of braces and knife plates is accomplished precisely in the factory and keep 5cm slot in each end for fabricating. So we can save the cover plates and take advantage of uniform distribution of flexibility in braces and buckling behavior. After series of improve design, hope to demonstrate the better design method of the braces buckling in-plane in next tests.
Subjects
SCBF
brace buckle
FEM analysis
Type
thesis
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