Large-Scale Fsi Experiments on Tsunami-Induced Forces in Bridges


Abstract eng:
Recent major earthquake events that occurred in the Indian Ocean (2004), Chile (2010) and Japan (2011) generated tsunami waves of significant heights, which inundated nearby coastal cities causing extreme destruction and loss of human lives. These waves inundated a large number of bridges, damaged the connections of the superstructure to the substructure in many cases and washed away the bridge decks. In the aftermath of these events the need to understand the tsunami effects and develop tsunami-resilient bridges in coastal communities became apparent. In an attempt to cover the gap of knowledge, a series of large-scale experiments on tsunami waves impacting a bridge was recently conducted. This paper describes these experiments which were conducted in the Large Wave Flume at Oregon State University. The scale of the experiments were 1:5, which allowed for realistic modelling of an I-girder bridge with a concrete deck slab and four steel girders connected through shear studs to achieve composite behavior. The flexibility of the bridge connections and substructure was modeled explicitly using elastomeric bearings under each girder and springs at the level of the bent cap to represent the behavior of the substructure (columns). The same bridge model was tested under five different configurations of connections, switching from a flexible substructure to a rigid one and from elastomeric bearings to rigid ones, to gain insight into the physics of the dynamic fluid-structure-interaction. In this paper, results from the two first test cases are presented. In the experiments both solitary waves and bores of different heights and velocities were examined. Free-surface elevation, flow velocities and dynamic pressures were measured at certain locations along the flume as well as pressures on the bridge, connection forces, accelerations, strains and displacements. It is shown that different phases exist in the vertical tsunami force histories, indicating (i) a large moment and a distinct rotational bridge mode at the time of the first impact of the tsunami wave on the bridge that induces the maximum tension in the offshore bearings, (ii) a pure uplift of the bridge during the passage of the wave through the bridge and (iii) a downward force at the end of the inundation. The maximum pressures on the offshore girder was seen to be up to 3.0 times larger than the pressures on the other girders. Furthermore, comparisons of the measured forces with integrated pressure measurements and inertial forces calculated from recorded accelerations, demonstrated the significance of the latter in satisfying the dynamic equilibrium of the bridge. Last, the ratio of maximum horizontal forces to maximum vertical forces was in the range of 0.54 to 2.2 and it was dependent on the wave type. It is expected the data presented in this paper will be useful for evaluating the applicability and accuracy of proposed simplified equations for tsunami loads. It will also be valuable for hydrodynamic model calibration and validation and for determining the capability of existing numerical codes that simulate fluid-structure interaction effects in structures which have significant inertial effects and displacements.

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Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
Rights:
Text je chráněný podle autorského zákona č. 121/2000 Sb.



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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 2579.:
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