[TowerTalk] Tower bases near basement walls

[Hank Lonberg]

     Dan:
     
     The potential problem that may occur is that you will laterally load 
     the basement wall due to the vertical load of the tower. This is 
     called surcharge horizontal earth pressure. It depends how deep your 
     basement is. In your case the surcharge vertical pressure starts at 
     the underside of the tower foundation. It will spread out (rule of 
     thumb not knowing your soils info) at a 45 degree angle from the edges 
     of the tower foundation, i.e., 1 foot out for 1 foot depth. If the 
     edge of the foundation is 2.5 feet from the outside of your basement 
     wall then the wall will not feel anything from the foundation vertical 
     load until 2.5 feet below or down 8.5 feet. If your basement is about 
     that deep or even say down to 10 feet you really will not be loading 
     the basement wall too much remember that the load is spreading out 
     both in the vertical and horizonatal directions at 45 degrees.
     
     As far as lateral loads, assuming a guyed tower, I wouldn't worry too 
     much. Kinda the same idea if the primary load is lateral and not 
     vertical. Just make sure to do a good job compacting the backfill 
     around the tower foundation. 
     
     I is always better to move the load farther away but it may not be 
     practical in your installation. If really worried expand the 
     foundation of the tower to the basement wall and drill in rebar dowels 
     and pour the tower foundation up to the basement wall.
     
     Hope this give you a feeling for this type of situation. Good luck and 
     good dx.
     
     73
     
     Hank Lonberg, P.E.
     KR7X
      
     
     


______________________________ Reply Separator _________________________________
Subject: [TowerTalk] Tower bases near basement walls
Author:  Dfmich@aol.com at ~INETMAIL
Date:    8/29/98 11:24 PM


I am in the process of installing a tower requiring a base that is 48 in dia 
and 6 feet deep. My current plan is to place it about 2.5 feet from my 
basement wall. It suddenly occurs to me that this may not be a good idea 
because of potential stress transferred to the wall when a big wind blows.
     
Anyone have thoughts or experiences to share on this issue?
     
Dan K9EA
     
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