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J. Mar. Sci. Eng. 2018, 6(4), 148; https://doi.org/10.3390/jmse6040148

Deciphering the Tsunami Wave Impact and Associated Connection Forces in Open-Girder Coastal Bridges

1
Department of Civil and Environmental Engineering, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557-0258, USA
2
O.H. Hinsdale Wave Research Laboratory, Oregon State University, School of Civil and Construction Engineering, 3550 SW Jefferson Way, Corvallis, OR 97331, USA
3
School of Civil and Construction Engineering, Oregon State University, 350 Owen Hall, Corvallis, OR 97331, USA
*
Author to whom correspondence should be addressed.
Received: 9 October 2018 / Revised: 24 November 2018 / Accepted: 29 November 2018 / Published: 5 December 2018
(This article belongs to the Special Issue Tsunami Science and Engineering II)
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Abstract

In view of the widespread damage to coastal bridges during recent tsunamis (2004 Indian Ocean and 2011 in Japan) large-scale hydrodynamic experiments of tsunami wave impact on a bridge with open girders were conducted in the Large Wave Flume at Oregon State University. The main objective was to decipher the tsunami overtopping process and associated demand on the bridge and its structural components. As described in this paper, a comprehensive analysis of the experimental data revealed that: (a) tsunami bores introduce significant slamming forces, both horizontal (Fh) and uplift (Fv), during impact on the offshore girder and overhang; these can govern the uplift demand in connections; (b) maxFh and maxFv do not always occur at the same time and contrary to recommended practice the simultaneous application of maxFh and maxFv at the center of gravity of the deck does not yield conservative estimates of the uplift demand in individual connections; (c) the offshore connections have to withstand the largest percentage of the total induced deck uplift among all connections; this can reach 91% and 124% of maxFv for bearings and columns respectively, a finding that could explain the damage sustained by these connections and one that has not been recognized to date; (e) the generation of a significant overturning moment (OTM) at the initial impact when the slamming forces are maximized, which is the main reason for the increased uplift in the offshore connections; and (f) neither maxFv nor maxOTM coincide always with the maximum demand in each connection, suggesting the need to consider multiple combinations of forces with corresponding moments or with corresponding locations of application in order to identify the governing scenario for each structural component. In addition the paper presents “tsunami demand diagrams”, which are 2D envelopes of (Fh, Fv) and (OTM, Fv) and 3D envelopes of (Fh, Fv, OTM), as visual representations of the complex variation of the tsunami loading. Furthermore, the paper reveals the existence of a complex bridge inundation mechanism that consists of three uplift phases and one downward phase, with each phase maximizing the demand in different structural components. It then develops a new physics-based methodology consisting of three load cases, which can be used by practicing engineers for the tsunami design of bridge connections, steel bearings and columns. The findings in this paper suggest the need for a paradigm shift in the assessment of tsunami risk to coastal bridges to include not just the estimation of total tsunami load on a bridge but also the distribution of this load to individual structural components that are necessary for the survival of the bridge. View Full-Text
Keywords: tsunami; experiments; wave impact; bore; solitary wave; slamming force; bridge; deck; connections; bearings tsunami; experiments; wave impact; bore; solitary wave; slamming force; bridge; deck; connections; bearings
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Istrati, D.; Buckle, I.; Lomonaco, P.; Yim, S. Deciphering the Tsunami Wave Impact and Associated Connection Forces in Open-Girder Coastal Bridges. J. Mar. Sci. Eng. 2018, 6, 148.

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