LOW-CYCLE FATIGUE TEST ON THE WELDED FLANGE-BOLTED WEB TYPE BEAM-TO-COLUMN CONNECTION FOCUSING ON ARRANGEMENT OF WEB BOLT

Abstract

 The most widely used beam-to-column connection type in high rise buildings for seismic-resistant frames is the welded flange-bolted web type beam-to-column connection. Most of the studies conducted so far on this connection type have evaluated the maximum bending strength by considering the bearing strength of bolts. This results were reflected in "Recommendation for Design of Connections in Steel Structures" in Japan.
 Recently, it is concerned that long period earthquakes will occur. Under long period earthquake, beam-to-column connection in high-rise building will be subjected a large number of small amplitude cycles of seismic force. Therefore, it is important to investigate the plastic deformation capacity of the beam before engaging the bearing capacity of the bolts. This problem was investigated by several studies using both cyclic loading and shaking table tests for high-rise building structures. However, the effect of the bolts arrangement on the moment transfer of the web was not one of the considered parameters.
 The purpose of this study is to investigate the influence of bolt arrangement and that of the moment transfer efficiency of the beam web on the plastic deformation capacity of beam. For this purpose, a shear plate and the beam flanges are welded to the 50mm thick end plate. Therefore, the out-of-plane deformation of the column plate is not taken into consideration.
 The specimens were tested by cyclic loading. Five types of bolt arrangements were designed by considering the bearing strength and slip critical design strength.
 The conclusions of this test are as follows:
 1) If the out-of-plane deformation of column skin plate can be neglected, the incipient slip critical strength obtained from the relationship between moment transfer of web and the relative rotation angle between the shear plate and web agrees with the calculated values.
 2) The plastic deformation capacity of the welded flange-bolted web type beam-to-column connection under relatively small amplitudes is determined as the minimum value between the slip critical strength and yield strength.
 3) In case with the slip critical strength of friction joint with high strength bolts on web is greater than the yield strength of the shear plate, upper limit of the plastic deformation capacity of the beam was confirmed. These specimens had almost the same number of cycles to failure as a typical shop welded beam-to-column connection.