ASCE7-10 Breaking Wave Loads on Vertical Walls 1

[WoodDesignCat]

Hi all,

I'm designing a building for dry flood proofing and need to design concrete walls for breaking wave loads.

1. Pmax and Ft do not need to be applied simultaneously correct? My understanding is that Pmax is maximum PSF, of the distributed loads used to create Ft. If you look at the attached picture, the 1.2γwds would be the static pressure in PSF where the dynamic pressure is at a maximum in the diagram. The 2.4γwds^2 would be the total force of that hydrostatic triangular load, (γw(2.2ds)^2 )/ 2=2.44γw ds^2.

2. Does a normal hydrostatic load need to be applied at the same time as the breaking wave static force? In the text it refers to it as "static wave pressure", but in the diagram it refers to it as "Hydrostatic Pressure". I assume it doesn't need to be applied at the same time as the normal hydrostatic pressure, because it doesn't appear to be any different than a hydrostatic pressure, it is just applied from the top of the wave height.

3. Do I need to apply hydrodynamic loads at the same time as the breaking wave loads? I was going to do apply both of them for wall strength calculations, but wasn't sure if I really should be doing this or not. When checking the overall building sliding resistance I was planning on only looking at the hydrodynamic force, and not the breaking wave force.

Also a follow up concern. The building needs to be waterproofed to BFE + 1', but according to these diagrams/equations to calculate ds, the crest of reflected waves goes above that height. This seems like an issue...

 

[SlideRuleEra]

WoodDesignCat - The labeling on this figure is somewhat confusing, but the concept is fairly straight forward. Breaking waves exert two types of pressure and force - static and dynamic.

Static pressure (PSF) is based strictly on the depth of the water. At the instant shown in the diagram, water depth goes from the crest of the impacting wave to the base of the structure. This last just a brief moment, then recedes... to be repeated with the next wave.

Dynamic pressure (PSF) is the impact of the energy in the wave on the structure. Again. this lasts just a very short time, then repeats. The shape of the diagram is a simplified mathematical representation of an actual wave impact.

So, static and dynamic pressure occur simultaneously and are added together.

Static force (lb/ft) is derived from the static pressure diagram. Dynamic force (lb/ft) is derived from the dynamic pressure diagram.

Static force and dynamic force occur simultaneously and are added together.

Maximum pressure (PSF) and maximum force (lb/ft) occur simultaneously, but don't measure the same thing. Therefore, they are not (and cannot) be added together. However, two things have to be checked:

1. Will the structure withstand the maximum pressure (PSF)?

2. Will the structure withstand the maximum force (lb/ft)?

I agree with you, waterproof to 1' above the wave's impact crest.

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[WoodDesignCat]

SlideRuleEra
Thank you for your insight.
This structure is in the flood zone of a river, which produces a separate hydrodynamic force. I would need to add the dynamic wave force and the river hydrodynamic force together right?

 

[SlideRuleEra]

I would need to add the dynamic wave force and the river hydrodynamic force together right?

Don't omit the Static Wave Force. There is water of a certain depth on one side of the structure and "air" on the other side. This means there is (static) water pressure acting on the structure. And that leads directly to (static) force, also.

Three forces are acting simultaneously on the structure:

1. Dynamic Wave Force
2. River Hydrodynamic Force.
3. Static Wave Force

Add all three forces together.

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[WoodDesignCat]

Thanks for the clarification. I wasn't planning omitting the static wave force, but should have been more clear.