Tie rod anchor for sheet pile 1

[tmalik3156]

Good day.

We are designing a sheet pile anchor (see diagram below) for the first time. So, your comments on the design will be highly appreciated.

The 32 mm dia tie rod, carrying about 350 kN tensile force, will hold an AZ28 sheet pile at an angle of 45 degrees.
We have designed a Hollow Square Section stool to accommodate the angle. The waler is made of back-to-back Channels. There are stiffeners between channel flanges (not shown).

In general, does this arrangement look acceptable and efficient? How could we improve the design for easier installation (think about shop and field welding)? What is the weakest link in this design, and how could we strengthen it?


Thank you

 

[MTSOE]

A possible alternative to the base plate and HSS stool components is to use a thick, equal-leg (for 45deg tie rods) angle with a hole cut in one of the legs to allow the tie rod to pass through. You could then eliminate the bottom plate and have the channels bear directly against the angle. I suspect you are also relying on that bottom plate to hold the double channel together while assembling this connection, so if you did opt to eliminate the bottom plate, you could still keep the double channel together using some small plate tabs along the channel flanges. A drawback to my suggestion, however, is that it has some tighter tolerances for everything fitting together.

Though I haven't run any calcs for this and don't know what size channel you're using, I suspect you could get away without putting stiffeners at the channel flanges given your loading.

 

[tmalik3156]

@ MTSOE, Thank you very much for your reply. I am not able to visualize the alternative you proposed (one equal leg angle with a hole). Could you provide a hand sketch please? How would this angle attach to the sheet pile at one side, and to the channels on the other?

Yes, there will be a pair of stiffeners between the flanges of the channel, but that was shown in my diagram for clarity.

 

[MTSOE]

Below is a tieback connection detail from the Earth Retention Systems Handbook by Alan MacNab. This image is for a soldier system but the overall scheme can be applied to sheet piles.

 

[HTURKAK]

Apparently this set up will work as long as it is verified with calculations. However IMO it is not efficient .

My points are;

- The waling should be behind the sheet pile wall,

- The waling should be supported on brackets and weak axis should be paralel to sheet pile wall,

I am familiar with Eurocodes and practice and do not have any idea local practice at your region.. Just for info, i attached a possible arrangement and Thyssen Sheet Piling Handbook Design.

Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[DaveAtkins]

How does the load get from the sheet piling to the waler? Do you have the HSS stool at every sheet pile?

DaveAtkins

 

[PEinc]

Don't forget to leave sufficient space between the waler channels and through any bearing plates to accommodate the trumpet and the tendon's corrosion protection (encapsulation?).

http://www.PeirceEngineering.com

 

[tmalik3156]

@HTURKAK, thank you very much for the reply. Your design looks robust. As for the location of waler, in our project it has to be in front of the wall.
There is a thread in the forum discussing merits of waler placing in front or behind the sheet. Link below

https://www.eng-tips.com/viewthread.cfm?qid=512896

@DaveAtkins, HSS stool is located at every other crest of sheet pile (spacing 2.8 m).

@PEinc, thank you for the reply. This design does not consider any tendon or encapsulation. It's just a 32 mm dia DYWIDAG thread bar. The entire anchor will be concealed inside a concrete cap.

 

[DaveAtkins]

Don't you need the stool at every crest, not every other crest? At the crests without a stool, how does the load get to the waler?

DaveAtkins

 

[MTNClimber]

Typically shims, as needed, which can be more stools at a 45.

 

[tmalik3156]

Don't you need the stool at every crest, not every other crest?

Yes, my mistake. The tie rods are at every other crest. Stools have to be at every crest. Thank you for pointing this out.

We might replace the HSS with an angle as shown below.

@MTNClimber, yes providing shims can be an option, instead of stools.

 

[PEinc]

tmalik3156, waterfront bulkheads very often retain unsuitable fill and natural soils that can be corrosive to ground anchors, the sheet piling, and the waler system. I would expect to see encapsulated tieback tendons with trumpets. This is pretty standard for permanent anchors. If your concrete cap overlaps the tendon encapsulation behind the sheet piling, you probably could skip the trumpet.

http://www.PeirceEngineering.com