×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Jetty Structure _ Piles in tension

Jetty Structure _ Piles in tension

Jetty Structure _ Piles in tension

(OP)
Hello Everyone,
We (me and my other two colleages) have designed a jetty structure having 2.5 km long. Structure was composed of a combination of 2 ( battered only in transverse direction at some locations) piles connected with a RC cap beam. Longitudinally the structure is connected with 2 I girders and CIP slab on top of them ( used for access road) and oil pipe line itself.
Piles are , at max. up to 60 m in length and they are partially in air then sea water then in sand , then in clay and touching the bed rock. We had to define whole structure in our model simply because the oil pipeline was continuous almost 750 meter long and every 750 meter there was an "S" in the pipe line. We performed response spectrum analysis using Maximum credible earthquake parameters.
Since we have got some excessive pile end forces (in tension ) at some locations , piles had to be anchored to the bed rock. For this purpose, some rock anchors are designed to take care of this force. As you know this rock anchor construction at a 60 meter deep is a quite difficult task to be performed for contractor.
For the seismic effects, we made use of reduction factors only for moments.
Indeed in seismic actions, (if the ends of piles not anchored to the bed rock) some slippage will be occurring b/w piles and the surrounding soil (clay and sand) and this will cause dissipation of seismic energy by frictional forces around the piles. Eventually this effect will reduce seismic forces and also axial tensile forces.Bu this effect can not be modelled quiet precisely in any Structural analysis program.

What reasonable reduction  factor can we assume to reduce our tensile forces at the tip of piles? or Should we make the analysis using different techniques ( such as time history analysis or push over analysis )

Is there anyone who might have faced such a problem before ?

Comments will be highly appreciated.

Thanks to all.

RE: Jetty Structure _ Piles in tension

This is a bit beyond my reasoning at 0430am, but I would like to point out something regarding your piles.  You've indicated that battered piles are used.  Years ago there was some papers describing damage due to 1964 Nagata (spelling?) earthquake in Japan and they found out that with battered piles the pile cap takes a real s*&^ kicking.  Try to keep this in mind. (It was an ASCE Journal article - look in the late 60s or early 70s).  In Vancouver area they started going for only vertical piles - unless there has been a rethink on this the last number of years.

Good luck - I'll be watching this thread!

RE: Jetty Structure _ Piles in tension

(OP)
BigH

Many thanks for responding to our problem.

We had been aware of the danger you pointed out in your reply. But that was the only option in transverse direction that we can make use of to reduce the displacaments of piles longing 60 meter at most in sea water+sand+clay and ending at the bed rock. But there is a reasoning that some slipping action in the piles could absorb some seismic energy. But we could not determine how to reflect this into our calculations. We know that it is a very complicated behaviour and it should be solved in the time domain using time history analysis. For the time being, we are after some recommodations from anyone who has previously faced such a problem before. Current AASHTO or CALTRANS Seismic specifications does not tell about much of this behaviour.

What could be your suggestions under taht light.

Thanks.  






Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

White Paper - The Evolving Landscape of Commercial Battery-Powered Trucks
What’s driving the evolving landscape of truck electrification? What are the barriers, motivators and strategies for accelerating the electric transition? What insights and resources are available for today’s design engineers working to achieve industry disruption and evolution? For answers to these and other pertinent questions, read this white paper. Download Now
eBook - Rethink Your PLM
A lot has changed since the 90s. You don't surf the Web using dial-up anymore, so why are you still using a legacy PLM solution that's blocking your ability to innovate? To develop and launch products today, you need a flexible, cloud-based PLM, not a solution that's stuck in the past. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close