Tie Back Wall Design

[HighPanda]

I am going to do preliminary/conceptual design of a piled wall. Since the wall is to retain soil/fill supporting railway tracks, deflection at the top is a major concern.

The program available to me is Wallap which is said to be able to stimulate the effects of strut/anchor fixed to the wall. However, I have to input the elastic modulus of the strut/anchor; hence, my simple question is how I can work out the elastic modulus of a tie?

 

[hokie66]

200000 MPa

 

[davep043]

The various post-tensioning bar and strand suppliers can provide that information. One that I know of is diwidag, at the website:

http://www.dsiamerica.com/products/geotechnic/dywidag-bar-anchors/steel-properties.html

 

[DRC1]

Deflections for shoring systems are difficult to predict accurately. Progams that use P/Y analysis do a better job than traditional analysis. One thing to consider is that when the tie is locked off, it tends to move the pile into the soil, essentially prestressing the system. The effect of this depends the lock off percentage of the tie. Most programs do not account for this.

 

[PEinc]

HighPanda, you may be overthinking this a bit. I have designed dozens of piled walls suppporting railroad tracks for numerous rail agencies. I have never been asked by a railroad for anything more than the deflection of the soldier beam. If you use tieback anchors, they are pre-stressed enough that there is usually little or no additional elastic stretch of the tieback tendon. If your design program does not give you the beam deflection, calculate it by hand or use an appropriate, available beam deflection formula for a simplified loading diagram. Then, make sure the deflection you calculate does not exceed the maximum allowed by the railroad specs.