From ceginfo@u.washington.edu Mon Jul 1 14:38:38 2002 Received: from mailscan5.cac.washington.edu (mailscan5.cac.washington.edu [140.142.32.14]) by lists.u.washington.edu (8.12.1+UW01.12/8.12.1+UW02.01) with SMTP id g61LcWw3049146 for ; Mon, 1 Jul 2002 14:38:35 -0700 Received: FROM mxu3.u.washington.edu BY mailscan5.cac.washington.edu ; Mon Jul 01 14:38:31 2002 -0700 Received: from mxout4.cac.washington.edu (mxout4.cac.washington.edu [140.142.33.19]) by mxu3.u.washington.edu (8.12.1+UW01.12/8.12.1+UW02.06) with ESMTP id g61LcVbr032606 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO) for ; Mon, 1 Jul 2002 14:38:31 -0700 Received: from mailscan-out2.cac.washington.edu (mailscan-out2.cac.washington.edu [140.142.33.17]) by mxout4.cac.washington.edu (8.12.1+UW01.12/8.12.1+UW02.06) with SMTP id g61LcUS4029657 for ; Mon, 1 Jul 2002 14:38:30 -0700 Received: FROM homer41.u.washington.edu BY mailscan-out2.cac.washington.edu ; Mon Jul 01 14:38:29 2002 -0700 Received: from localhost (ceginfo@localhost) by homer41.u.washington.edu (8.12.1+UW01.12/8.12.1+UW02.01) with ESMTP id g61LcTDw095852 for ; Mon, 1 Jul 2002 14:38:29 -0700 Date: Mon, 1 Jul 2002 14:38:29 -0700 (PDT) From: Civil and Environmental Engineering To: cegrads@u.washington.edu Subject: Ph.D. Defense -Jubum Kim (fwd) Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII The final examination for the Ph.D. degree for Jubum Kim will be held on Wednesday, July 3, 2002 at 1:30 p.m. in 218 More Hall. "Behavior of Hybrid Frames Under Seismic Loading" > > Abstract: > > A new type of frame has been developed recently for resisting > seismic loads in buildings. It consists of precast concrete beams > and columns that are joined by a combination of conventional steel > reinforcing bars and unbonded post-tensioned tendons. Because the > reinforcement consists of two different types, each with its own > function, the system is referred to as a Hybrid Frame. Its > viability has been demonstrated experimentally. > > The nonlinear action in the Hybrid Frame takes place at the > beam-column interface. When the story drift exceeds a threshold > value, the beam rocks on the face of the column and a gap opens at > the top or bottom of the interface. The opening of the gap > stretches the unbonded PT tendon that crosses the interface, and > the tendon therefore tends to close the gap, thereby bringing the > frame back to the upright position. The tendon remains elastic > throughout the response, even though the behavior is nonlinear due > to the local loss of contact during rocking. Reinforcing bars > cross the interface and are grouted into ducts in the beam and > column. When the gap opens and closes, the bars yield alternately > in tension and compression. They contribute to the moment > strength of the connection and dissipate energy. > > In this study, a corner hybrid beam-column joint sub-assemblage > was tested to determine its response to lateral load. The test > illustrated the ability of the hybrid frame to meet the minimum > strength and toughness requirements of concrete framing systems > that are not detailed per current building code provisions. > > In a hybrid frames, the center-to-center distance between two > adjacent columns increases as the gap opens at the beam-column > interface. This beam growth is also present in a conventional > cast-in-place reinforced concrete frame due to beam hinging, but > is often neglected in design practice. In order to investigate how > the beam growth affects the frame response to earthquake loading, > computational models for both a hybrid frame and a conventional > reinforced concrete frame were developed and the responses that > they predicted were verified against experimental results. It was > shown that ignoring the effects of beam growth could underestimate > the structural demands on some of the framing members. In > particular, the demands on the outer columns were much greater > than those on the columns in the middle, especially at the lower > floors. > > Multi-bay, multistory hybrid frames with different configurations > were designed and subjected to static lateral load and then to > horizontal ground motion. It was found that the effects of beam > growth were important, and that they were greater under the static > loading. The static response thus provided an upper bound to the > dynamic action. The response of the frames, including inter-story > column drifts and demands on individual framing members, was > closely related to the geometry of the frame, such as the clear > span-to-beam depth ratio, and a number of bays. > > A simplified method was developed to determine the response of a > building frame, including the effects of beam growth. The method > was based on kinematics and the strength of the framing members > and was significantly simpler than the detailed finite element > analyses against which it was calibrated. The method was shown to > reproduce the primary features of the beam growth behavior and to > provide a good estimate of the critical response quantities. > Professor John F. Stanton, Chair Ashley F. Emery, GSR Marc O. Eberhard Gregory A. MacRae Gregor R. Miller .