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UJNR Tsunami Modeling Workshop


December 10-12, 2014
Corvallis, OR USA

Many bridges in Japan were destroyed or severely damaged by the 2011 Heisei Tsunami, but not all: a few bridges survived in spite of intense tsunami loadings. Variations in the observed bridge damage lead us to make careful investigations of the failure mechanisms. Understanding bridge performance should yield methodologies for how to assess a bridge in the tsunami inundation zone and how to design a bridge effectively for its construction or retrofit.

It is common to perform numerical simulations of bridge-fluid interactions for wind loadings. While the numerical models for winds on bridges are sophisticated turbulence models that are validated, such is not the case for tsunamis. The tsunami problem is still new, and is more difficult than the wind problem because tsunami impact on a bridge is highly transient with the involvement of free surface and air-water two-phase flows interacting with a compliant solid body (bridge).

After the 2011 East Japan Tsunami, Public Works Research Institute (PWRI) performed a series of well-controlled laboratory experiments to investigate tsunami forces and pressures on a variety of bridge superstructures. Their laboratory data include the incident tsunami wave conditions and the tsunami impact processes recorded with a high-speed camera. We believe that their data are ideal to use for testing the performance of the numerical models. Furthermore, nearly complete laboratory data for bridge substructures (columns) are available from Arnason (2004).

With the reliable laboratory data in hand, we have a US-Japan collaborative workshop aimed at validating numerical models for tsunami effects on bridges. It will be a three-day workshop convened as part of the UJNR activities, and will be held at Oregon State University from December 10 through 12. The format of the workshop is designed to focus more on discussions than on presentations. To accomplish this, the following benchmark cases are selected, so that predictive models can be evaluated and discussed among the participants during the workshop.

Active workshop participants you can choose two or more benchmark problems. The models to implement can be numerical, analytical, or even experimental in different scales. Your solutions should include, but not limited to, the time-history predictions of the net horizontal and vertical forces as well as the water-surface variations. You are also encouraged to present your results in different forms, e.g. computer-graphic animation, parameterization of complex results, and production of useful prediction formulae.

If you are interested in this modeling activity, we would like to know your tentative decision on which problem(s) will be modeled, and your method of modeling. Your model results should be submitted to Michael Scott no later than December 1, 2014, so that your results can be distributed to all workshop participants prior to the workshop. Your short write-up should include the governing equations, boundary conditions, numerical scheme, input, output, presentations (graphics and animation, etc.). With this, all the information for discussions concerning the models will be available to participants before the workshop. Then, the valuable but limited workshop time will be spent in detailed discussion and clarification of the model.

PWRI Wave Flume Experiments

Four fluid-structure interaction simulations for a tsunami loading on a 1/20 model scale bridge deck are highlighted. For each case the simulation can be run using either the full flume shown below or a shortened flume section using the wave height and wave velocity recorded by a wave guage located 1 meter before the bridge deck. The dimensions of the experiment setup below are in meters


Full Flume Setup (m)

The table below highlights the cases to be investigated. For a more detailed summary, click on the case you wish to explore either in the table below or the Index.

Case 1
Case 2
Case 3
Case 4
Wave Height (cm)
15
20
15
20
Stillwater Depth (cm)
20
10
15
10
Deck Type
A
B
B
C
Deck Material
acryl
wood
acryl
wood

The bridge decks for the four simulations are shown below: Note that Deck C has the same dimensions as Deck B, except for the added fairing. The input table above contains information on which simulation uses which bridge deck. Please note that the dimensions for the bridge decks are in centimeters.


Deck Type A (cm)

Deck Type B (cm)

Deck Type C (cm)

Input

  • In addition to the water conditions and deck geometry, you should note that the gate for this setup drops down.
  • Additionally, a wave gage located 1 meter upstream from the bridge deck records the wave height and wave velocity, which can be used to check or generate the simulated tsunami wave.
  • More detailed information can be found by clicking the link to the case description page.

Output

  • For each case modeled, plot and provide the time history of the Total horizontal and vertical forces. For comparison's sake, please record the time history data between 10 (s) and 40 (s) in model scale time.
  • Please provide an animation or photographs documenting the simulation for the specified time interval.
  • You are encouraged to analyze further responses and/or phenomenon if you find it of interest. You may also wish to look at further mitigation efforts or design improvements (such as venting, etc.)

Tsunami Bore Impingement onto a Square Column
Two fluid-structure simulations of a square column are highlighted to test bridge pier loading. The simlutations will test the effects column orientation has on tsunami wave loading.


Column Testing Setup

The experiment consists of a 16.6m long, 0.6m wide and 0.45m deep tank. The bridge pier is represented by a 12x12 cm column. Since we are looking at column orientation, there are 2 Cases: (1) Column edge-facing flow & (2) Column side-facing flow.

Input

  • Please note that the gate in this experiment setup is lifted.
  • The column is located 5.2 m downstream of the gate.
  • More detailed information can be found by clicking the link to the Bridge Pier Loading description page.

Output

  • For each column case modeled, plot and provide the time history of the force exerted on the column.
  • Please provide an animation or photographs documenting the simulation.
  • You are encouraged to analyze further responses and/or phenomenon if you find it of interest (such as column displacement, etc).

For details concerning the workshop schedule, see the Agenda
Questions? Suggestions? Visit the Contact Page