psychedomination
Structural
- Jan 21, 2016
- 123
Hi there,
A marine beacon (in this case pile with a sign on it used to signal ships) has been designed by a previous structural engineer in my department in the past (he no longer works at the company). The project manager has asked me if it would be fine to alter the marine beacon design by reducing the embedment depth from 25 feet to 20 feet (this is mainly because we have left over 20’ piles from a previous project and the P.M. did not want to waste money welding another 5’ of steel on.). The marine beacon is embedded into coral reef. The pile is a 2.5’ diameter steel pile filled with concrete.
I am a graduate and not fully confident in pile design. I did approach the senior structural engineer. He initially did not want me to do this project because of the amount of geological unknowns. However, he told me to try it and if I can convince him then we will agree with the proposed changes.
I have used the rigid analysis formula for piles and posts for signs embedded in the ground, where lateral loads govern from the international building code IBC 1805.7.2 as seen in my Foundation design book by Coduto. Please let me know if I am going about this in the right way and if my assumptions are suitable.
The first thing I determined was the wind loading – See attached image of calc:
**I do not know how to determine wave loads (I do have data on the wave speeds and heights but do not know how to actually get a wave loading figure). Because of this I assumed worst case scenario hurricane force winds of 150mph with a safety factor of 1.5 acting down the length of the pile (i.e. neglecting the wave loads and assuming 150mph*1.5 winds are acting on the length pile above the reef, which is 20’. In the country where I reside, we do get hurricanes up to category 4, is this assumption reasonable?
I next used the rigid analysis formula to determine the minimum embedment depth. – See attached image of calc:
For this calculation because we did not know the condition of the reef (normally it would have the strength of sedimentary rock), I assumed that the soil conditions were sand.
With this said I ended up getting a minimum embedment depth of 15. 2 feet, which would mean that reducing the embedment depth from 25’ to 20’ should be fine.
What are your thoughts? Any guidance would be greatly appreciated.
A marine beacon (in this case pile with a sign on it used to signal ships) has been designed by a previous structural engineer in my department in the past (he no longer works at the company). The project manager has asked me if it would be fine to alter the marine beacon design by reducing the embedment depth from 25 feet to 20 feet (this is mainly because we have left over 20’ piles from a previous project and the P.M. did not want to waste money welding another 5’ of steel on.). The marine beacon is embedded into coral reef. The pile is a 2.5’ diameter steel pile filled with concrete.
I am a graduate and not fully confident in pile design. I did approach the senior structural engineer. He initially did not want me to do this project because of the amount of geological unknowns. However, he told me to try it and if I can convince him then we will agree with the proposed changes.
I have used the rigid analysis formula for piles and posts for signs embedded in the ground, where lateral loads govern from the international building code IBC 1805.7.2 as seen in my Foundation design book by Coduto. Please let me know if I am going about this in the right way and if my assumptions are suitable.
The first thing I determined was the wind loading – See attached image of calc:
**I do not know how to determine wave loads (I do have data on the wave speeds and heights but do not know how to actually get a wave loading figure). Because of this I assumed worst case scenario hurricane force winds of 150mph with a safety factor of 1.5 acting down the length of the pile (i.e. neglecting the wave loads and assuming 150mph*1.5 winds are acting on the length pile above the reef, which is 20’. In the country where I reside, we do get hurricanes up to category 4, is this assumption reasonable?
I next used the rigid analysis formula to determine the minimum embedment depth. – See attached image of calc:
For this calculation because we did not know the condition of the reef (normally it would have the strength of sedimentary rock), I assumed that the soil conditions were sand.
With this said I ended up getting a minimum embedment depth of 15. 2 feet, which would mean that reducing the embedment depth from 25’ to 20’ should be fine.
What are your thoughts? Any guidance would be greatly appreciated.
