The Effects of Multi-Support Earthquake Excitation on Seismic Performance of the Bosphorus Bridge

Abstract eng:
In this study, it is aimed at better understanding the response of the Bosphorus Bridge to earthquake excitation by considering the specifically produced strong ground motions for the bridge. The Bosphorus Bridge, one of the first longspan bridge in Turkey, is located on the Bosphorus Straits and has a vital function of connecting the two continents, the Asian and the European. Since opened to traffic in 1973, the bridge has been subjected to various extreme events, such as wind, truck, marathon and earthquake loads. Due to high importance of earthquake, the bridge needs to be investigated under the realistic earthquake to take required measures to no interruption in its operation. For this purpose, the multisupport earthquake analysis (MSA) of the bridge is performed and the results from the analysis are compared with those from the previous study of the uniform-support analysis and the retrofit project. Based on the project drawings, 3-D advanced finite element-FE model of the bridge is established. The developed FE model is then verified in terms of modal characteristics with the previous studies in literature. Considering the geometric coordinates of the bridge’s supports, sitespecific strong ground motions including the Mw=7.5 scenario earthquakes on the main Marmara Fault are produced. With the help of these efforts, the non-linear time-history analysis is conducted for multi-support excitation. The outcomes from the analysis is compared and the effects of multi-support earthquake excitation on the structural behavior of the bridge are identified. Based on the results from the MSA of the bridge, the tensile force of the main and side span cables noticeably increased under the MSA compared to the uniform support and retrofit project. These results directly affected the axial force of the main cable at the tower top saddle; however, balancing effect of the deck at the expansion joint level led to the decrease in the shear force at the tower top saddle. As to the sectional actions at the tower base section, the compressive axial force, shear force and bending moment were relatively increased and such increase is related to the increase in the main and side span cables. This study demonstrated that the previously obtained results for the critical components of the bridge cannot satisfy compared to the MSA. Therefore, the MSA should be considered to make reliable seismic analysis and to conduct reliable structural rehabilitation for long-span bridges. Another important result of the study is that general procedure and rules for the multi-support earthquake analysis and site-specific ground motion have to be included in the codes.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket