Reduction of Stress Concentration at Stop-Hole by Bolting a Crack
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International Journal of Steel Structures https://doi.org/10.1007/s13296-020-00434-1
Reduction of Stress Concentration at Stop‑Hole by Bolting a Crack Toshiyuki Ishikawa1 · Shogo Kiyokawa2 · Wataru Nakatsuji3 Received: 24 January 2020 / Accepted: 29 October 2020 © Korean Society of Steel Construction 2020
Abstract A stop-hole, which is drilling at the crack tip, is one of the famous tentative repairs of fatigue cracks in steel structures. When the crack becomes longer, the stress concentration of the stop-hole also increases. Therefore, during the tentative repair of long fatigue cracks, the chances for re-initiation of the fatigue cracks from the stop holes are high. The bolting stop-hole method is a useful technique against fatigue cracks. In this technique, bolting is applied only for the stop-holes at the crack tips. Therefore, as the crack length increases, the effect of the bolting stop-hole method decreases. In this paper, the authors propose a stress concentration reduction technique for a stop-hole by bolting the fatigue crack between stop-holes. The effect of the proposed technique was verified by tensile and bending tests of specimens as well as finite element analysis. From the tensile and bending tests, it was clarified that the stress concentration of the stop-hole was drastically reduced by bolting a crack under the condition before the slippage of bolts. Additionally, multi-bolting cracks have the advantage of improving the slippage load of the bolts in a crack. Furthermore, finite element analysis verified the reduction in stress concentration of the stop-hole by bolting a crack, and the effectiveness of bolting cracks and stop-holes was also shown. Keywords Stop-hole · Stress concentration · Slit open displacement
1 Introduction In steel bridges under heavy traffic, several fatigue cracks develop at welded joints. For the tentative repair of fatigue cracks, a stop drilled hole or stop-hole, which is drilling at the crack tip, is often used. Several studies on stop-holes have been reported in the past (Fisher et al. 1980; Yamada et al. 1986; Miki et al. 1990; Mori and Uchida 2001; Okura and Ishikawa 2002; Song and Shieh 2004; Murdani et al. 2008; Wu et al. 2010; Mori et al. 2011; Chen 2016). These studies report that when the crack between the stop-holes becomes longer, the stress concentration at the stop-hole edge also increases. Therefore, to reduce the stress concentration at the edge of the stop-hole, bolting of the stop-hole * Toshiyuki Ishikawa t‑ishi@kansai‑u.ac.jp 1
Department of Civil, Environmental, and Applied Systems Engineering, Kansai University, 3‑3‑35 Suita‑shi Yamate‑cho, Osaka 564‑8680, Japan
2
Technical Proposal Division, Yokogawa Bridge Holdings Corp., Chiba, Japan
3
Technical Proposal Division, Yokogawa Bridge Corp., Tokyo, Japan
(Mori 1996) or joining the steel plate is generally applied (JSCE 2013). However, even in these repair methods, it was reported that the cracks re-initiated from the edge of the stop-hole (JSCE 2013). As a method to reduce the stres
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