Rowe's moment reduction for soldier piles

[HanStrulo]

Happy Tuesday everyone.

I know this question has been asked alot, but I would like to ask add my voice to the confused crowd.

Is there any paper or reference that proves that Rowe's reduction should never be used on soldier piles with one level of supports and only be used on sheet piles?

I understand the reduction theory is empirical based on sheet piles tests but is it meanly based on flexibility of the system or we don't have enough data to say for sure?

If anyone has any successful example where it was used on soldier piles, I would greatly appreciate that.

Thanks,

 

[PEinc]

All of the references I have discuss Rowe's moment reduction being developed for and used for anchored, sheet pile bulkheads designed by the free earth method. I have never seen it used with soldier beam walls.

http://www.PeirceEngineering.com

 

[DaveAtkins]

Agree with PEinc. Although, if you assume no fixity where the soldier pile extends into the ground, it would make sense that the bending moment and deflection in the pile will be less than what calculations would predict. But I have never seen any research done on this.

DaveAtkins

 

[HanStrulo]

PEinc and DaveAtkins: Thank you!

This is a purely theoretical question, but wouldn't be beneficial if there is also research on the reduction moment for the soldier piles? The system seems to me like it's more flexible than sheet piles and it would result in more economical sections if the free earth moments would also be reduced.

 

[HanStrulo]

Another question, is the use of friction on the back of temporary soldier pile lagging walls to calculate the pressures common?

 

[DaveAtkins]

If you are referring to taking advantage of wall friction, I do not believe it is common. However, it seems like something that could be rationalized. For the active soil wedge to move outward, it would need to slide downward along the lagging.

DaveAtkins

 

[HanStrulo]

Thank you!

I have some drawings of existing shoring with very light pile sections. Under the normal rankine (no friction with the wall), the sections seem to be under designed.
I thought maybe the designer used Rowe's reduction factors but I gathered from my research that it is not used unless it's a sheet wall.
So i am just assuming it used a friction.

 

[EireChch]

Wall friction is very real think that is really overlooked to often in my opinion. For sheet piles, piled walls I think it should be considered. Check C760 the UK document for embedded retaining walls. It is one of the best publications on the matter.

For lagging walls I am not so sure on using friction. If there is ability for the lagging to move downwards then your friction is lost. I dont really think lagging should be capable of moving downards if designed properly. Solider pile and lagging wall are less common in UK so PEinc is your man on this subject.

 

[DaveAtkins]

If there is ability for the lagging to move downwards then your friction is lost.

Good point.

DaveAtkins

 

[PEinc]

I have designed thousands of SSP and soldier beam walls, both temporary and permanent, cantilevered, braced, and anchored. Unless specifically not allowed for a project or by an owner agency, I always use wall friction with Coulomb earth pressure coefficients. I have never had a problem. The key to success is to never load up simultaneously on too many load or moment reducing design "tricks." Many design manuals and texts mention some ways to lower the earth pressure or use temporary overstresses. These include things like designing the SSP or soldier beams for 80% of the empirical earth pressure envelope, using Coulomb vs. Rankine, varying the allowable percentage of steel yield stress, and using Rowe's Moment Reduction. If you use too many of these "tricks" simultaneously, the odds are good that you will have a problem. BUT, the big question is, how many are too much?

http://www.PeirceEngineering.com

 

[PEinc]

EireChch, lagging moves forward because the soil pushes it forward or a braced or tiedback soldier beam pushes back against the lagging causing the lagging to bulge, which looks like forward lagging movement. In either case there is strong contact, and therefore friction, between the soil and the lagging. I don't see how friction would be lost.

http://www.PeirceEngineering.com

 

[HanStrulo]

@PEinc/ @ EireChch: Thank you for the insights.

I never considered friction before in design and I also never considered any increase in allowable yield for steel. I always end up with higher pile sections than my peers.

for now, I will introduce these two options to my design in order to get closer to pile sections that I know work in the field but I can't make them work on paper with conservative approaches.

 

[PEinc]

HanStrulo, just make sure you have references available so that, when the reviewer questions you, you have backup.

http://www.PeirceEngineering.com