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• PRC 보- 기둥 접합부의 내진성능

– 저자 :  송진아, 박홍근, 이창남, 엄태성

Prefabricated reinforced concrete (PRC) uses prefabricated re-bars for fast construction and cost-saving. In the present study, prefabricated re-bar details for beam-column connection were developed. Cyclic loading tests were performed to evaluate the earthquake resistance of interior and exterior beam-column connections. The beam-column connections were designed in full scale to satisfy the requirements of the special moment frame specified in KCI 2007 and ACI 318-08. For the PRC method, re-bar welding, coupler splice, headed bar anchorage, and high strength steel (SD500W) were used in the specimens. Test results showed that the PRC connections showed deformation capacity greater than the minimum story drift ratio of the special moment frame, 3.5 %, specified in ACI 374.1-05. The load-carrying capacity, yield stiffness, and energy dissipation capacity of the PRC connections were comparable to those of conventional reinforced concrete connection. The major failure modes of the PRC connections were flexural crushing of concrete and re-bar fracture at the beam plastic hinge region. The re-bar welding and coupler splice did not significantly affect the performance of the specimens.

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• Cyclic Seismic Testing of Composite Concrete-Filled U-shaped Steel Beam to H-Shaped Column Connections

– 저자 : 이철호, 박홍근, 박창희, 황현종, 이창남, 김형섭, 김성배

In this study, the cyclic seismic performance of a concrete-filled U-shaped steel beam to H-shaped steel column connections was experimentally
evaluated. The concrete-filled U-shaped steel beams were compositely attached to the concrete floor slab. The test was conducted in two stages. The first testing program was carried out on one-sided moment connections to find the most promising connecting scheme. The strengthening scheme, or welding steel plates to the beam bottom flange with minimized stress concentration, was shown to be the most satisfactory, and it was used in the second-stage test on two full-scale cruciform specimens. Considering the unique constructional nature of the proposed composite connections, the critical limit states such as weld fracture, local buckling, concrete crushing, and rebar buckling were carefully addressed in designing specimens. Test results showed that the connection details and design procedures proposed in this study can successfully control the critical limit states mentioned previously. The proposed connection detail successfully pushed the plastic hinging to the tip of the strengthened zone as intended in design, thus effectively protecting the more vulnerable beam-to-column welded joint. The specimens typically exhibited a maximum story drift capacity of more than 5.5% rad, exceeding the minimum limit of 4% rad required of special moment frames. Four of the five specimens tested in this study eventually failed because of a low-cycle fatigue fracture across the beam bottom flange at a high story drift greater than 5.0% rad.

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• Cyclic Loading Test for Beam-Column Connection with Prefabricated Re-Bar Details

– 저자 : 엄태성, 송진아, 박홍근, 김형섭, 이창남

A Prefabricated Reinforcing Bar Construction (PRC) Method was developed for fast construction and cost savings. In this study, a prefabricated reinforcing bar connection method for the earthquake design of beam-column connections was developed. Three interior and one exterior full-scale beam-column connections, including a conventional reinforced concrete (RC) specimen, were tested under cyclic loading. The test specimens were designed to satisfy the requirement of the special moment frame specified in ACI 318-08. In the proposed connection method, reinforcing bar welding, coupler splice, and headed bar anchorage were used, considering the PRC Method. The test results showed that the story drift ratio of the PRC beam-column connections exceeded 3.5%, which is the requirement of ACI 374.1-05. The load-carrying capacity, yield stiffness, and energy dissipation capacity of the PRC specimens were comparable to those of the conventional RC specimen. The major failure modes of the PRC specimens were flexural concrete crushing and reinforcing bar fracture at the beam plastic hinge region. The welding of the reinforcing bars and the coupler splice did not significantly affect the performance of the specimens.