Abstract
Buildings constructed with non-seismic details are at risk of damage and collapse when an earthquake occurs due to a lack of strength, stiffness, and ductility. For reinforced concrete (RC) moment-resisting frames, seismic retrofitting methods that can enhance strength or ductility should be applied. However, such strategies have many disadvantages related to constructability, serviceability, securing integrity, and cost. In this paper, a welded concrete-filled steel tube (WCFST) system was examined in order to resolve the problems of the existing seismic retrofitting methods for RC moment-resisting frames. To evaluate the seismic performance of the proposed system, two specimens, one with non-seismic details and another reinforced with a WCFST seismic system, were manufactured for the cyclic loading tests. As a result of the experiments, the specimen retrofitted with the WCFST system showed maximum load, effective stiffness, and energy dissipation capacity values approximately 3, 2, and 2.5 times greater, respectively, than those obtained from the existing reinforced concrete frame specimen. The experimental results indicate that the proposed WCFST system is expected to be effective at improving the seismic performance by enhancing both the strength of the existing reinforced concrete frame structures and the dissipation of the seismic energy.
Highlights
In the construction of concrete buildings without seismic details, the seismic load is not taken into account
This paper proposes a seismic retrofitting method using welded concrete-filled steel tubes (WCFSTs) that improve both the strength and energy dissipation
A base plate is installed to the existing reinforced concrete frame, and integration is ensured by welding the Concrete-filled steel tubes (CFSTs) frame to the base plate
Summary
In the construction of concrete buildings without seismic details, the seismic load is not taken into account. FEMA 547 [1] proposes methods such as adding new structural elements (e.g., a concrete or masonry shear wall and steel braced frame) and increasing the cross-sectional size of the columns or beams in order to improve the seismic performance of concrete moment frames. A base plate is installed to the existing reinforced concrete frame, and integration is ensured by welding the CFST frame to the base plate This technique has an advantage in that it is possible to utilize the space during construction and it is easy to check the status of the existing members after an earthquake. To evaluate the performance of the WCFST seismic-resistant system, both a non-seismically designed reinforced concrete frame specimen and a specimen retrofitted with the WCFST system were subjected to cyclic lateral loading tests
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