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Retrofitting Method by Connecting External Reinforced Concrete Frame with High-Strength Anchor Bolts
existing school buildings,retrofittd by RC external frames,high-strength anchor bolts,seismic preliminary evaluation,pushover analysis,retrofit of school building,
|Publication Year :||2021|
After the largest Earthquake in Taiwan’s history on September 21st, 1999, the damage of school buildings were of particular significance. Although the seismic design force of the school buildings were one-quarter higher than the general structure of buildings in Taiwan, they were still the most damaged buildings. In addition to serving as a place for education, school buildings are often used as temporary shelters for victims after a major earthquake. Therefore, they must be strengthened to improve their earthquake resistance. The National Center for Research on Earthquake Engineering proposed some complete procedures for seismic evaluation and seismic retrofit of school buildings, which we could carry out if it meets the economic benefits of reinforcement. The typical retrofit methods of buildings in Taiwan include RC jacketing, wing wall and shear wall, but the buildings were affected during the construction by those methods. This research proposes that by adding RC external frames to the retrofit method would be more effective, a technique seldom used in Taiwan.
Adding RC external frames is a retrofit method by which two external frames are added along the weak direction of existing buildings to raise the seismic resistance. In this research, RC external reinforced concrete frames were connected to existing buildings using high-strength anchor bolts. The high-strength anchor bolts transfer the seismic force from existing building to external frames. Therefore, this method would be appropriate for use in school buildings. The anchor bolts is able to dissimilate seismic force. The advantages of this construction method are: reliable jointing, improved anchoring force, reduced use of hinterland space, and furthermore increased construction stability.
To use this method, we must understand the design process of adding RC external frames. First, design the frame with cross-sectional dimensions, then from a nonlinear static pushover analysis, the capacity curve is achieved and confirmed. Second, have a detailed design of the number of high-strength anchor bolts, the T-head anchoring end plate, the depth of embedment, and then check failure modes of the anchor strength.
Finally, one of the existing school building will be taken as an example. After the retrofit, it was confirmed that the retrofit design could eliminate the problems of the poor failure mode of the existing structure. We hope the benefits would not only be used for school buildings, but also for hospitals or other public and private buildings.
Given the fact that there is little related experimental information about the capacity of the anchor bolts to dissimilate seismic force, this study has designed five reinforced concrete frame specimens, including an existing frame specimen and four new frame specimens. They were created by adding RC external frames, experimental anchor bolts to strengthen the capacity test and by using a set of steel molds as well as steel beams at the National Center for Research on Earthquake Engineering. In conclusion, when compared with the common reinforcement method of post-installed rebar, the RC External frames method was superior. From the test results, it can be found that adding RC external frames can effectively improve the lateral load, stiffness and capacity.
|Appears in Collections:||土木工程學系|
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