Line Load from a deck

[zahid01]

Hi there,

a timber deck has been put behind a 1m high retaining wall, I have to check the capacity of a this wall due to the new loading, I know how to get earth pressure, but how would you convert a point load from the deck post applied on the wall to a thrust? or what is the easiest way to check this wall?

 

[FixedEarth]

welcome to the site!

Use the attached equations for all applicable surcharges.

 

[born2drill]

How far behind the wall are the deck footings, and how deep are those footings? The footings ought to go at least 3ft deep, so for a retaining wall that short, I doubt the deck is imparting any load to it.

 

[zahid01]

Hi There

thanks for your attention and help.

the footings are very close close to the wall and about 300-400mm deep. the footing will cause a point load, and my from calcs the footing will induce a 3.41kN point load, how would I convert this into horizontal thrust?

your help is much appreciated

 

[msquared48]

From your information, it appears that the wall is just over 3 feet high and the bottom of the footing is about 12 to 16" deep.

If the amount of earth retained is three feet, then the effect can be ignored if the deck footing is no closer than 3 feet to the wall.

If the total height of the wall is three feet, bottom of footing to top of wall, then you could be 1 to 2 feet from the wall with little or no effect.

Can you provide a quick sketch showing the relative dimensions?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[zahid01]

Hi there

a sketch of the wall is attached. I just to know how to convert that 3.14kN point load to a horizontal thrust,


thanks for help

 

[Riggly]

I am a little late on this but I want to make an input. From looking at your sketch, and the loads, you really have nothing to worry about except your wall is made of very flexible material. Theoretically, I see your concern though, and I do understand your question. Essentially, you are concerned about the horizontal effect of the vertical load on your wall. Simply divide the load by the area of the tip of the footing, assuming it it end-bearing. You will get your applied pressure. Now, to obtain the vertical component of the footing load at at the at the wall, distribute the load at approximately 45 degrees, or use the appropriate distribution curve submitted by FixedEarth. Now that you have the vertical component of the load at the wall, multiply that by the active earth pressure coefficient (Ka). If you wall is very rigid use the at-rest coefficient (Ko), but that is unlikely. See? Similar to how you calculate lateral earth pressure by first calculated the vertical load and multiplying it by the earth pressure coefficient, treat the applied vertical footign load the same.

I did not calculate the loads, but this should be a small number, and doubt it is a concern. And remember, it will just affect a localized area on the wall. Overtuning effect on the wall due to the footing load is not a concern, because the applied force on the wall due to the footing load will affect the wall almost to the bottom.

By the way, what type of wall, and what type of soil is contained behind the wall?

Just another comment based on your wording: "I have to check the capacity of a this wall due to the new loadingf". I believe it should be worded that you have to check the effect of the timber deck footing load on the retaining wall, or re-evaluate the factor of safety of the wall against overturning due to the footing load of the deck. ie. I don't believe the capacity of the wall change due to this load.

Hope this helped.