Wave Loads - breaking vs. non-breaking, ASCE 7 vs. Goda, finite wall height

[engjg]

I am trying to develop wave loads for a structure where I expect the wave(assumed to be depth limited) will over top the structure. Using the ASCE 7 equations and just neglecting the portion of the pressure diagram where it will be overtopped I am coming up with load much higher than anticipated. That has got me thinking about whether I need to consider a "breaking" wave load. I am looking at other equations like the Goda equations which appear to be a "non-breaking" wave loads. When is it reasonable to assume a non-breaking wave condition? Does anyone have an example using the Goda equations?

 

[WARose]

It's hard to say without some dimensions & numbers.....but I generally consider a breaking wave load on just about anything submerged. Where it gets tricky is when you have a deeply sumbmerged object or a suspended object.

Sometimes I have used the Minikin method to figure the pressure.....and if that is comparable to ASCE's wave height....I'll just defer to them.

 

[1503-44]

If your structure decreases depth below half the wave length, which it apparently does, it will cause shoaling. Breaking occurs when water depth is 1.3 x wave height. It seems that you will at least experience breaking wave loads at some time, perhaps even during a somewhat lesser than design wave height.

 

[engjg]

See sketch attached

 

[r13]

This article is excellent in explaining breaking wave calculation using ASCE7-05 equations. Link. Overtopping can be another beast that requires another tool.

 

[r13]

The linked article describes the application of breaking/non-breaking wave equations (developed by Goda). Link

 

[WARose]

engjg (Structural)(OP)23 Dec 20 19:05
See sketch attached

https://files.engineering.com/getfile.aspx?folder=34b9f38d-fbe1-4534-9922-2

Yeah, I'd say that definitely will see a breaking wave load. (Assuming there is not more of the structure not shown.)

And keep in mind: with the flood elevation higher than the top of the deck and the still water level being well below that....you need to select a worst case scenario for the wave during the flood. It may be that the controlling wave load would be with the flood stage being at a lower level than that 6' elev.

 

[struct_eeyore]

both FEMA and Army Corps of Engineers have coastal construction manuals that deal specifically with this topic. I wish I could point you to a specific document, but the # is eluding me at the moment. It might be the case that you are allowed to just use the hydrodynamic load instead of breaking wave in this situation (don't take my word for it)

 

[Simba13]

The Shore Protection Manual is my go to for wave loads. It includes pretty clear definitions of breaking and non-breaking waves as well.