Raker design for sheetpile shoring

[jrrkar]

We are designing a single line vertical wall shoring system using PZ-22 shoring with two levels of wales and struts. Due to the orientation of the excavation and proposed footing, we have to angle the struts away from the 90 degree orientation in the horizontal direction. We were also planning on angling down the struts in the vertical direction in order to connect the struts to a brace pile a few feet above the ground. With the angled struts in both the horizontal and vertical planes, we get an eccentric loading in the strut. I have been searching for any type of design examples for something similar with no succes. Pile Buck shows the angled rakers but does not give any design information.

With even a slight angle (either horizontal or vertical), we are coming up with a large eccentric moment in the strut. We are not sure if we are not looking at something correctly, or if indeed the induced moment from a small eccentricity is that great.

Any suggestions on designs or books that discuss this would be greatly appreciated.

 

[GeoPaveTraffic]

If I'm following you, I would treat the ends of the strut as pinned, i.e. no moment. The only differences due to the strut being angled is a higher axial load and the need to make sure that the wale can take the load component(s) that are not perpendicular to the wall.

Hope this helps, if I'm not understaning your situation, please post more info.

 

[jrrkar]

Thanks. I think you are understanding the situation. The strut would be welded to the wale, and then on the other end, the strut would be welded to a vertical brace pile just above the ground. I think the whole connection type is the big question..is it pinned, fixed, etc. We have done simlar layouts and they went through the review process just fine. Another time, the reviewer insisted that the eccentricity moment be taken into account as if the ends were fixed. I tried finding information on this in various text books but could not find any detained information.

 

[csd72]

jrrkar,

If you do need to do this then this is a simple frame analysis with a few of the sheet pile columns acting as a column under lateral pressure and the other members forming the other parts of the frame.

Look up the back of the steel code to find typical I values for sheet piles.

 

[PEinc]

thread507-241474

This thread also has some information on raker braces.

 

[DRC1]

There is an ecentricity at the wale and a thrust at the pile. Although I have not done a lot of rakers, typically I will run the web flat and flanges horizotal. I weld the flanges to the web as a simple connection then I weld a knee to the sheets and the wale to resist the moment in the wale from the raker. I ussualy use footing blocks for the bottom of the rakers as it is difficult to deal with the large thrust with out significant deflection with a pile head. The construction of rakers is tricky and should only be attempted by experienced sheeting contractors. Prior to tie backs, rakers were very common, and most sheeting crews were proficent in installation. With the increased use of tie backs in the '70's, rakers are not very common anymore. Construction methods are as important as good design. Note that these walls do have more movement than tied back or horizontally braced walls.

 

[55562262626]

I think you are understanding the situation. The strut would be welded to the wale, and then on the other end, the strut would be welded to a vertical brace pile just above the ground. I think the whole connection type is the big question..is it pinned, fixed, etc.
There is an ecentricity at the wale and a thrust at the pile. Although I have not done a lot of rakers, typically I will run the web flat and flanges horizotal.
sheet pile:

http://www.china-sheetpiling.com