Tsunami Bore Uplift Effects on Coastal Structures

Tsunami Bore Uplift Effects on Coastal Structures Computational Analysis and Experimental Comparison Ben Anderson (University of Minnesota) Huiquing Yao (University of Hawaii) Advisor: Dr. Ian Robertson (University of Hawaii) HARP REU Program 8/3/2011

Overview • Introduction • Computational Models • 2D vs. 3D • Computational data comparison with experimental data • Conclusions and Recommendations

Introduction • A blocked tsunami wave under a slab can caused a large uplift force –– piers, harbors, and building floor slabs • As a tsunami wave approaches the shore, it transform into a turbulent bore –– Turbulence model

Potential gap designs Example pier structure -- Ryan Takakura

The Samoa Tsunami on September 29, 2009 Failure of new ferry dock caused by 2009 Samoa tsunami (Robertson, et al, 2010)

In the Lab • Simulating tsunami waves with a dam break Plan drawing of wave flume -- Ryan Takakura

Dam break swing gate Dam break flume Slab and wall setup --Ryan Takakura

Experimental Video • http://www.youtube.com/watch?v=DIxqe1FSPbk-- “The Effects of Tsunamis on Coastal Structures” Back

Computer Modeling • Dimensions • Mesh Size • k-εand k-ω SST • 3D and 2D Comparison

Dimensions Total length : 12.02637m Gap : 0m 2D model extended to equate extra volume at the end of the flume 5.7404m 6.286m

Mesh Size • Area surrounding the slab and tank floor were designed with a smaller cell size Back

k-ε and k-ω SST Comparison • k-ε • based on model transport equations for the turbulence kinetic energy (k) and its dissipation rate (ε) • k-ω SST • based on model transport equations for the turbulence kinetic energy (k) and the specific dissipation rate (ω) • “Shear-stress transport” (SST) accounts for the transport of the turbulent shear stress

k-ε Side View

k-ω SST Half Speed

k-ω SST Side View -incorporates standing water

k-ω SST has a more realistic bore and pressure results • Used k-ω SST for our simulations

3D and 2D Comparison • The biggest issue with the two dimension model is the air that gets trapped under the slab • 3D may give a more realistic representation of what actually happens

3D Side View

2D Slab (k-ω SST)

3D Slab

3D View of Slab

Chose to use 2D model • 2D has a faster computational speed

Comparing Experimental and Computer Models • Software: OpenFoam • Focused on the maximum uplift force (N) • k-ωSST for all cases • 2D • Graphs: 0 cm gap

Slab height : 14cmUpstream : 60cmDownstream: 5cm

Computational and Experimental Measurement Differences • Load cell measured net load • Computational model only measured integral of the uplift load on the slab

Slab height : 5cmUpstream : 60cmDownstream: 2.5cm

Conclusions and Recommendations • Recommend making mesh finer to eliminate variances due to mesh size • Extend fine mesh out in front of the slab • Different cases use different mesh sizes • Try more simulations in 3D

"This material is based upon work supported by the National Science Foundation under Grant No. 0852082. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation."

Works Cited • Christy Allison, Taylor Dizon, Deanna Quickle . “The Effects of Tsunamis on Coastal Structures” REU, University of Hawaii at Manoa, summer 2010 • Ge, Ming. “Uplift Loading On Elevated Floor Slab Due To A Tsunami Bore.” Thesis for Master’s Degree, Dept of Civil Engineering, University of Hawaii at Manoa, December 2010 • Robertson, Ian, et al. “Reconnaissance Following the September 29, 2009 Tsunami in Samoa.” Research Report, Dept of Civil Engineering, University of Hawaii at Manoa, January 20 2010 • Takakura, Ryan. “Reducing Tsunami Bore Uplift Forces By Providing A Breakaway Panel.” Thesis for Master’s Degree, Dept of Civil Engineering, University of Hawaii at Manoa, December 2010

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Tsunami Bore Uplift Effects on Coastal Structures