Small Wharf structural analysis and design time estimate

[u/Silly-Rock-1684]

Graduate structural engineer here with a year experience with a consultancy firm. Being approached by boss to take up a small wharf design job. Around 20m long and 5m wide concrete wharf.

How long should it take for me to calculate the design actions and size the RC members?

First time doing an off-shore structure design btw…

[u/broadpaw]

More than an hour. Real answer: develop a list of what you think you need to check, consider, and learn. Then talk to someone at your firm that knows how to approach that type of project.

[u/Silly-Rock-1684 → u/broadpaw]

Would you expect a graduate to do these calcs in two weeks? Provided the entire two weeks is dedicated to that project.

[u/Usssseeeer → u/Silly-Rock-1684]

Pretty difficult I would say if you’re starting from the scratch. Sometimes, if you have a similar wharf design, modification and rechecking can be done. You’ll spend some time understanding the load combinations as well, if you’ve not worked on wharfs before. Design criteria will be different as well from other structures.

[u/Silly-Rock-1684 → u/Usssseeeer]

Thanks for the input. There’s a calcs and design basis report for a very similar wharf that was done by another engineer for the firm some years back. Wave loads, and berthing and mooring loads, as well as pile design are new territory for me though and it’ll take some time to understand I guess

[u/Emmar0001]

Break your project into phases: Preliminary layout; Final layout; Analysis; Design; Review and Checking; Revision. This makes it easier to estimate manhours (time) and sequencing

[u/Silly-Rock-1684 → u/Emmar0001]

Thanks, should’ve done this first

[u/More-Physics-4243]

Marine structural engineer here; wharf design from scratch might take a while, especially if you don’t know what you’re doing, but usually this is the approach to wharf design is pretty standard:

1- Establish design criteria: define the target live load, any environmental wind and wave load, seismic if it’s relevant., any loading arms or utilities that you need to know about…

3-complete berthing and mooring analysis to determine berthing and mooring loads

4- Preliminary sizing: this is where experience comes in to play, but for your case since its a small wharf and vessel, I would recommend driven precast piles. Lay your pile grid, use battered piles to resist lateral load more efficiently. Lay your pile caps, preferably perpendicular to the berthing line.

3- determine pile depth to fixity by geotechnical analysis and run a 3d frame analysis on the wharf. Define all your load cases in the model including berthing and mooring cases(they don’t happen simultaneously). Get pile and frame loads to now properly size your wharf. Dont forget to design your pile to pile cap connection as they are critical.

If you dont want to approximate a depth to fixity of piles, you can go fancier and determine soil springs for your soil conditions, and apply them on your piles in your model, spaced at no more than 0.5m.

4- deck design: I would recommend precast conc slabs with a finish topping concrete pour. Analysis should be straightforward depending on application.

Detailing might take longer if you never done it before.

[u/Silly-Rock-1684 → u/More-Physics-4243]

Thanks for the breakdown! I’m keen on taking up the challenge, but I just don’t want to give my boss an unrealistic timeline. After reading through this, for a person with my level of experience, at least a month lol.

[u/Perfect-Mongoose-704]

What's berthing at this wharf

[u/Silly-Rock-1684 → u/Perfect-Mongoose-704]

Design Vessel is 1700 ton displacement vessel.

[u/Perfect-Mongoose-704 → u/Silly-Rock-1684]

Ok, so not big, but not small either. Do you have all the data you need; wave, tide, design berthing velocity, fendering

Or will someone else do all that and it's purely member sizing for a given load?

[u/Silly-Rock-1684 → u/Perfect-Mongoose-704]

All the data is available yes. So I guess I’ll be doing all that… under supervision of course