Steel Sheet Pile Cofferdam

[hydraulicstr]

I need to design a steel sheet pile cofferdam with granular fill. It has a barge impact force of 1500 kips. All the manuals or publications talk about impact force but not about how to resolve it. The interlock tension formula can be used for internal pressure due to fill, can i use the same to resolve the 1500 kip external lateral load. Thank you.

 

[SlideRuleEra]

Could you avoid the problem by installing either free-standing fender piles or dolphins to take the impact?

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[hydraulicstr]

I was looking into dolphin design and ended up deciding on steel sheet pile. Can you point me to a reference for dolphin design. Thank you.

 

[cvg]

try
DOD MIL-HDBK-1025-1 piers and wharves

 

[SlideRuleEra]

I would not want a barge impacting a dewatered, braced cofferdam even if the cofferdam had been designed for impact.

The DOTs of US states that have coastal bridges should have detail standard drawings for dolphins. Try looking through the Florida DOT drawings. Here is a typical general arrangement:

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http://www.VacuumTubeEra.net

 

[hydraulicstr]

Thank you, I will still appreciate if someone has any ideas about my initial question.

 

[SlideRuleEra]

I may have misunderstood the question, rereading your initial post, are you asking about impact on a cellular cofferdam (with granular fill)?

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[hydraulicstr]

Yes that is correct. AASHTO vehicle collision manual uses it as a dolphin structure to protect piers. But even that document does not mention anything about how the lateral load due to vessel should be resolved.

 

[bridgebuster]

Hydraulicstr: The US Steel Sheet piling manuals on SRE's site has design examples for filled cellular cofferdams.

 

[SlideRuleEra]

bridgebuster - I looked through it, but saw nothing about barge / ship impact.

Seems like a collision with a cellular cofferdam would take place more or less a point on the circular structure and be inelastic because of the granular fill. This could damage the sheeting interlock.
Circular cofferdams, at least dewatered ones, are unstable when damaged.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[hydraulicstr]

I agree. So i should try to design a pipe pile or a group of pipe piles. I am still looking for a reference. Any guidance will help.

 

[BUGGAR]

I've designed waterfront structures and we always consider ship impact against anything solid without energy absorption of any sort to be a must-avoid failure situation. You can do a pushover analysis on a dolphin and come up with an idealized force at best, but this is usually way beyond allowable ship hull pressure anyway.

 

[BUGGAR]

There seems to be a lot of similar questions on these forums: what if this bumps into that, what are the forces? I just finished a shock absorber analysis for adapting car shocks for crashing X-Ray machines into concrete walls. I think in the Mechanical Forum. Is there a magic search index for this stuff?

 

[cvg]

this supercedes the previous reference and it gives methods to determine berthing and impact forces on dolphins and fenders. suggest fenders be installed to protect the cellular structure.

http://www.wbdg.org/ccb/DOD/UFC/ufc_4_152_01.pdf

 

[Archie264]

Wow, that was a very interesting document. Now if ever called upon to design bullrails, catwalks, breasting dolphins or aircraft carrier camels I'll know where to start. It's a zoo out there, apparently.

 

[BUGGAR]

UFC 152, The Bible.

(Along with Blodgett)

 

[hydraulicstr]

CAn i use a Steel pipe pile and design it for shear and moment like a cantilever beam?

 

[BUGGAR]

Yes, we frequently design monopiles using large (over 30 inch diameter) steel pipe. We sometimes design them to absorb energy elastically, but acting alone, they absorb little. We've used them around Long Beach Harbor to install navigation lights and warning signs but these get wiped out around every six months. Then we just add a change order to the nearest piledriving contractor working nearby to replace it. I think the biggest pipe pile we've used has been 72 inches - that was in the gulf.

 

[hydraulicstr]

As the load is lateral, can i consider the internal moment due to weight of the composite column as resistive moment ?