tsunami resistant structure

1. SEMINAR
ON
TSUNAMI RESISTANT
STRUCTURES

2.  It is normal to say ‘nothing could resist a tsunami’, but this is not true.
In places where boats and ships were deposited on top of buildings, well
build buildings survive.
 A tsunami is the Japanese for ‘harbour-wave’ and it means a big wave
or a series of big waves. They are caused by any big disturbance in the
Ocean or other body of water, such as earthquakes, volcanic eruptions,
meteorites or landslips.
 Tsunami flooding may travel inland >1000 feet, and the "rundown"
creates continued damage as the water quickly retreats back out to sea.
INTRODUCTION

3. Why do buildings fail in Tsunamis?
• When a building stands in the path of the wave, the wall facing it tends to
block the water, and the pressure here increases. Later on the water will
swirl out again, loading the other side of the building. Water just 7 feet deep
will have pressure of 450 pounds per sq ft, 21 kN per square metre, much
more than any normal structure can withstand.

4. WHAT CAUSES THE DAMAGE?
Structures tend to be destroyed by tsunamis because of five general
causes:
1. Force of the water and high-velocity water flow
2. Impact of debris carried by the forceful water
3. Fire spread by floating debris
4. Erosion (i.e., scour) of foundations
5. Wind forces from waves

5. Hydrostatic pressure: causing imbalance
and pressure at the bottom
Buoyant forces: Upward force of the
submerged structure

6. Hydrodynamic forces : Caused by
flow of water moving
with high velocity (Drag force).
Combination of pressure from
moving mass of water and friction
generated on water flows on the
structure.

7. Debris impact forces

8. GUIDELINES FOR DESIGN:
1. Early warning systems and horizontal evacuation have been the main strategy
for many years. The current thinking, however, is to design buildings with vertical
evacuation areas (sacrificial first floor).
2. Vertical evacuation areas can be part of the design of a multi-story building,
stand-alone structure for a single purpose. Existing structures such as well-
constructed parking garages could be designated vertical evacuation areas.

9. Experts suggest these strategies for tsunami-resistant construction:
1. Reinforced concrete or steel-frame structures are recommended for vertical
evacuation structures.
2. Multi-story structures, with the first floor being open (on stilts) or breakaway
so the major force of water can move through. Rising water will do less
damage if it can flow underneath the structure. Again, this design is contrary
to seismic practices, which makes this recommendation complicated and site
specific.
3. Construct deep foundations, braced at the footings. A tsunami's force can turn
an otherwise solid, concrete building completely on its side.

10. 4. Design with redundancy, so that the structure can experience partial
failure (e.g., a destroyed post) without progressive collapse.
5. As much as possible, leave vegetation and reefs intact. They won't stop
tsunami waves, but they can slow them down.
6. Orient the building at an angle to the shoreline. Walls that directly face
the ocean will suffer more damage.
7. Use continuous steel framing strong enough to resist hurricane-force
winds.
8. Design structural connectors that can absorb stress.

12. Framed structure with shear walls

13. Wave pressure distribution in buildings

14. Fig: Building with elevated tower in Srilanka
Prototype tsunami-resistant shelter in Car Nicobar in
the Bay of Bengal, India

15. TSUNAMI PROOF STRUCTURES
1. Situated in UK.
2. Pier shaped structure rests in hollow masonry wall
(similar to aircraft wing)
3. Hydrodynamic shape will shield it from waves, structure
is located by facing the sea.
4. Allows water to pass around it and takes the impact of
tsunami load.

16. A.H.L.Swaroop et al – “Response of Coastal Structures against Tsunami Forces and
Mitigation Measures” - Vol. 5, Issue 4, April 2016
In this paper, the following three different type of structures are chosen for the
analysis and the tsunami forces imparted on these structures are worked out when
subjected to tsunamis of different heights.
Type A: An R.C. Chimney of height 30m with change in cross section at three
stages of height.
Type B: An overhead service reservoir of six lakh litres capacity with three
horizontal bracings placed each at 4m intervals.
Type C: A three storied school building with infill walls of size 32mx15m in plan
and height 3.5m each.

17. ANALYSIS FOR TSUNAMI FORCES
Different forces due to tsunami wave impact on structures are:
• When turbulent water flows hitting the structure, the hydrodynamic and impact
forces act on the structure in the direction of approaching tsunami.
• Inundation depth and flow velocity of a tsunami wave are the important
parameters for calculating the forces imparted on the structure. The above forces
are worked out for beach slopes of 1in 50 and 1in 100 as shown in fig.

18. Hydrodynamic forces: Hydrodynamic (drag) force is expressed as
proportional to the product of square of flow velocity and the projected area on
the structure. The drag coefficient CD is taken as 2.0 for rectangular column
members and 3.0 for wall members . For the given location and beach slopes,
the deign parameter is computed from equation 1 and the hydrodynamic force,
FD is calculated from equation 2 given below h = 0.125 – 0.235
------- 1
------- 2

19. The values of hydrodynamic and impact forces are calculated for type
A,B&C structures for different inundation depths and beach slopes.
The total force that is considered to act on the structure is obtained by
summing up of the hydrodynamic and impact forces at different levels
of each structure.

20. Results of tsunami loads for three different types of structures at different
slopes of 1:50 and 1:100 at different run up heights of 3m,6m ,9m and 12m.

21. TWIN WING TSUNAMI BARRIER
• It’s the ultimate passive tsunami protection solution.
• Consists of 2 steel wings with concrete foundation (made of pre-fabricated
blocks) and loaded with ballast.
• Operated only after early warning system.

22. Fig: Coastal water gets in i.e., negative tsunami wave action

23. • Water sucked in will emerge as positive tsunami waves towards the coast, were
second steel wing act as a barrier and blocks the water

24. 1. Doesn’t effect normal operations, as its build 10m under the sea.
2. Only operated after the Tsunami warnings are given.

25. MEMBRANE – TSUNAMI FLOAT BARRIER CONCEPT
• Flooding protection device.
• Designed for 20m height Tsunami waves.
• Strong membranes stop hydrodynamic forces of Tsunami.
• Curvature and tensile stresses developed in the membrane are analysed .
• Thickness of membrane is not more than 1cm, FOS is 2.5.
• Made of fabrics.

26. Tsunami waves are if larger than designed case, only few water spills out of
the membrane.

27. TSUNAMI SURVIVAL CAPSULE POT
• It’s a personal safety system, it allows for immediate isolation from
impending danger.
• Simple structural design philosophy in Aerospace industry and is “light
weight and strong”.
• Numerous software such as PATRAN, NASTRAN, DYTRAN were used.

28. This model is a combination of plate element (represents the
outer shell), and bar element (represents tubular framing).

29. 1. Designed for coastal communities with alternative form of evacuation.
2. Capsules have been dropped from height of 10ft (3.04m) for impact with hard
surface.
3. Few other load cases were conducted as below:
Small object impact Telephone pole impact
Large object impact Wall impact
Sharp penetration Rebar penetration
Damming loads Debris damming
Thermal exposure Burn test

30. Control system : A conceptual controlled design developed for coastal as
follows:
A complete protection by bio-shield having mangroves and woodlands
Proper land use planning (atleast 1km away from the coast line)
A evacuation building(EB) with salient features
A roof terrace shall be designed to provide more refuge area.

31. Appropriate single / multiple house plans for Tsunami resistance

32. An ideal plan for a reconstruction with control system

33. Proposed Model Houses: Tsunami resistance houses suitably planned and
recommended for a rural coastal rehabilitation. These houses will have
utilities as listed.
The building is designed as EQ/Tsunami/cyclone/flood resistant type of
RCC.
Corrosion free Fibre reinforced Polymer rebars are used instead of
conventional steel
The building is raised on columns to allow seawater to pass beneath the
structure (soft story) and open in other routine times to make multipurpose.
Disaster information and alert system is accessible for the people of the
house

34. The Terrace level is set above the most of the rare tsunami events.
Terrace is designed to provide additional accommodation.
Emergency power supply is made possible with the solar/wing energy.
Water supplied from elevated water tank is directly discharged in to small
capacity water tank provided at the terrace in each house.
Desalination plant is available in each housing unit.

35. CONCLUSION
• Shear wall should be in sea ward direction.
• Smaller face of building should face sea direction.
• Height of building should not be more than 30m.
• Opening should be 50-75% as per IS draft code for Tsunami resistant building
• Circular column to be preferred.
• Provide reinforcement ties around opening and window frames should be well
anchored in the wall.

36. Thank you