Local Strain-Based Low-Cycle Fatigue Assessment of Joint Structure in Steel Truss Bridges During Earthquakes
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International Journal of Steel Structures https://doi.org/10.1007/s13296-020-00399-1
Local Strain‑Based Low‑Cycle Fatigue Assessment of Joint Structure in Steel Truss Bridges During Earthquakes Chao Jiang1 · Takeshi Hanji1 · Kazuo Tateishi1 · Masaru Shimizu1 Received: 17 April 2020 / Accepted: 26 August 2020 © Korean Society of Steel Construction 2020
Abstract During the 2011 Tohoku Earthquake, a truss bridge joint structure was cracked due to large cyclic deformation, making us recognize the importance of assessing the seismic performance of joint structures in truss bridges from the viewpoint of low-cycle fatigue. In this study, seismic response analysis of an actual deck truss bridge was performed under different seismic waves, and local strain behavior generated at welded joints around a joint structure was clarified using a zooming analysis technique. The results revealed the possibility that welded joints for a lateral gusset-plate in a joint structure can be cracking sites during earthquakes. In addition, it was indicated that seismic isolation bearings can significantly reduce the local strain at the joint structure and improve its low-cycle fatigue performance. Moreover, as a simple countermeasure, weld toe treatment by grinding is also effective to decrease the possibility of low-cycle fatigue cracking at the joint structure. Keywords Low-cycle fatigue · Steel truss bridge · Joint structure · Seismic response analysis · Local strain
1 Introduction Steel truss bridges are widely employed in transportation networks of many countries because of their light dead load and high load-carrying capacity (Damon et al. 2017). The collapse of the I-35W Mississippi River bridge in Minneapolis in 2007 revealed that the failure of a joint structure in a truss bridge can cause a collapse of the whole bridge. In other words, the joint structure is a fracture critical member that must be protected from fracture. Previous research on structural redundancy in deck truss bridges and through truss bridges has also shown that diagonal chords or upper main chords are among the most important members and their failure can cause the collapse of the whole bridge (Nakatani et al. 2009). This research result and the experience from the I-35W accident clearly demonstrate the need to avoid the fracture of joint structures, diagonal chords, main chords, and gusset plate zones at joint structures, and the gusset plate zone has been carefully investigated in terms of
* Takeshi Hanji [email protected]‑u.ac.jp 1
Department of Civil and Environmental Engineering, Nagoya University, Furo‑cho, Chikusa‑ku, Nagoya 464‑8603, Japan
load-carrying performance against static loads (Hu 2013; Kawaguchi et al. 2015; Liao et al. 2011). Joint structures in truss bridges are typically considered to be free from fatigue. However, because various truss members are connected at the joint structure, stress fields can be complicated and high stress concentrations can occur at these connections. In high-cycle fatigue region, fatigue tests on a full-
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