Seismic resistance capacity of beam–column connections in high‐rise buildings: E‐Defense shaking table test

Abstract

A series of E-Defense shaking table tests are conducted on a large-scale test specimen that represents a high-rise steel building. Two types of connections featuring the connection details commonly used in 1970s, in the early days of high-rise construction in Japan, are adopted: the field-welded connection consisting of welded unreinforced flanges and a bolted web type, and the shop-welded connection in which the flanges and web are all-welded to the column flange in the shop. To examine the seismic capacity of a total of 24 beam-to-column connections of the specimen, particularly when it is subjected to long-period ground motion characterized not so much by large amplitude as by very many cycles of repeated loading, the test specimen is shaken repeatedly until the connections fractured. The test results indicate that a few of the field-welded connections fractured from the bottom flange weld boundary in a relatively small cumulative rotation primarily due to the difficulties in ensuring the welding and inspection performance in the actual field welding. The shop-welded connections are able to sustain many cycles of plastic rotation, with an averaged cumulative plastic rotation of 0.86 rad. Two shop-welded connections exhibit ductile fractures but only after experiencing many cycles. The presence of RC floor slabs promotes the strain concentration at the toe of the weld access hole in the bottom flange by at least twice compared with the case without the slab, which had resulted in a decrease in the cumulative plastic rotation by about 50%. 606 Y.-L. CHUNG ET AL.existing high-rise buildings, long-period ground motions could demand significantly larger energy dissipation than the design waves commonly used in the Japanese seismic design, especially to beam-to-column connections, with anticipated cumulative deformations amounting to several to 10 times larger than those expected for the design waves [4].The 1994 Northridge and the 1995 Hyogoken-Nanbu earthquakes tested the seismic performance of steel moment frames, which have been widely used in seismic design in the U.S. and Japan. In the earthquakes, severe damage was observed in the welded unreinforced flanges and bolted web connections (WUF-B) [5][6][7]. A number of Japanese high-rise buildings built in the 1970s had also adopted WUF-B connections, although connection details were similar but not exactly identical to those damaged in the earthquakes.Considering those circumstance, the writers decided to experimentally evaluate the seismic performance of the high-rise buildings subjected to long-period ground motions. Several alternatives were considered for the type of testing, i.e. a shaking table test, a hybrid online test, and a quasi-static loading test. In all cases, the test specimen had to preserve a realistic scale since the behavior involving serious damage such as fractures was to be simulated. A substructure-based hybrid online test [8][9][10][11][12][13] was appealing to conduct such a test, but quasi-static loading was not necessarily preferable a...

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