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Earthquakes and Structures Volume 24, Number 2, February 2023 , pages 81-90 DOI: https://doi.org/10.12989/eas.2023.24.2.081 |
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Study of using the loss rate of bolt pretension as a damage predictor for steel connections |
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Chui-Hsin Chen, Chi-Ming Lai, Ker-Chun Lin, Sheng-Jhih Jhuang and Heui-Yung Chang
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| Abstract | ||
| The maximum drifts are important to the seismic evaluation of steel buildings and connections, but the information can hardly be obtained from the post-earthquake field investigation. This research studies the feasibility of using the loss rate of bolt pretension as an earthquake damage predictor. Full-scale tests were made on four steel connections using bolted-webwelded-flange details. One connection was unreinforced (UN), another was reinforced with double shear plates (DS), and the other two used reduced beam sections (RBS). The preinstalled strain gauges were used to control the pretensions and monitor the losses of the high-strength bolts. The results showed that the loss rate of bolt pretension was highly related to the damage of the connections. The pretensions lost up to 10% in all the connections at the yield drifts of 0.5% to 1%. After yielding of the connections, the pretensions lost significantly until fracture occurred. The UN and DS connections failed with a maximum drift of 4 %, and the two RBS connections showed better ductility and failed with a maximum drift of 6%. Under the far-field-type loading protocol, the loss rate grew to 60%. On the contrary, the rate for the specimen under near-fault-type loading protocol was about 40%. The loss rate of bolt pretension is therefore recommended to use as an earthquake damage predictor. Additionally, the 10% and 40% loss rates are recommended to predict the limit states of connection yielding and maximum strength, respectively, and to define the performance levels of serviceability and life-safety for the buildings. | ||
| Key Words | ||
| damage predictor; loading protocol; loss rate of bolt pretension; moment connections; steel buildings | ||
| Address | ||
| Chui-Hsin Chen: Department of Civil Engineering, National Yang Ming Chiao Tung University, 1001, University Rd, Hsinchu 300, Taiwan Chi-Ming Lai: Department of Civil Engineering, National Cheng Kung University, 1, University Rd., Tainan 701, Taiwan Ker-Chun Lin and Sheng-Jhih Jhuang: National Center for Research on Earthquake Engineering, National Applied Research Laboratories, 200, Sec. 3, HsinHai Rd., Taipei 106, Taiwan Heui-Yung Chang: Department of Civil Engineering, National Chung Hsing University, 145, Xingda Rd, Taichung 402, Taiwan | ||