Experimental Study on Optimum Strength of Beam-to-column Connection Consisting of Wide Flange Members with Out-of-plane Beams

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In a steel frame of wide flange members beam to column connections have a great deal of shear deformation capacity which is essential in earthquake resistant design of steel frames. An experimental study on the load carrying capacity of these connections stiffened by out of plane beams are carried out. The experimental parameters in this test are the yield ratio of a connection and connected members, alpha , and width thickness ratios of column flanges.Obtained results are as follows : (1) Elasto-plastic deformation behavior of frames subjected to horizontal shear forces changed at the yield ratio, alpha , of about 0.4. (2) In the frame with the yield ratio, alpha , exceeding 0.4, the maximum shear strength of the connection increased a little in the presence of the out of plane beams. (3) And the energy absorption of connections from beginning to maximum strength was not gained by the presence of the out of plane beams. (4) The width thickness ratio of column flanges gives no remarkable difference in the maximum shearing strength and the energy absorption capacity of the connection. However, deterioration of shearing strength after maximum is greater in the width thickness ratio of 15 than in that of 10. (5) In the case of alpha less than 0.4 , the maximum shear strength of the connection increased remarkably in the presence of out of plane beams and the lower alpha the more remarkable. (6) The energy absorption capacity up to the maximum strength is also remarkable in the case of alpha less than 0.4 . (7) The out of plane beams give the stiffness to the connection web irrespective of width thickness ratio of flanges in members. The stiffened connection web shows a great deal of energy absorption capacity and stable restoring force characteristics of the frame.Thus the yield ratio of 0.4 in a connection and members is preferable in actual spatial frames in a view point of earthquake resistant design.