Retaining Wall w/ HS20 Loading 1

[dheigher]

Can someone help me out with a simple procedure for calculating the additional pressure on a retaining wall from HS20 loading. Can HS20 be converted to an equivilant surcharge? The "retaining wall" is actually the wall of an open top underground tank and it is about 22' tall.

Thank You

 

[ishvaaag]

Bridge loads are properly for bridges. However there are provisions for retention walls in the AASHTO specs, and you may use these to approximate the effects of the set of point loads.

As well, Section 6 (Culverts) in the Standard same I have (15th ed, 1992) address how to treat effects of wheel loads through earth fills ... even if for vertical loads gives idea of what is reasonable to think.

The same kind of schemes you can search in geotechnical texts, for the integrated pressure coming from the loads.

 

[curvbridger]

HS20 loading is often equated to 2 feet of equivalent surcharge.

A more precise way of treating this load is to use Figure 5.52B (in 1996 AASHTO).

A mathematical treatment of this proceedure was put together by Spangler in a paper dated 1938 Published by Iowa State College.

 

[PEinc]

curvbridger is correct. AASHTO calls for a traffic surcharge equal to the uniform lateral pressure caused by an additional 2 feet of earth behind the wall. Refer to AASHTO Eq. 5.5.2-3. AASHTO says this vertical load should be based on 2 feet of dirt weighing 125 PCF unless other data is available about the anticipated surcharge load. However, some state DOT's, such as PADOT, require additional surcharge beyond the 2 feet of earth. Pennsylvania has much heavier trucks than the rest of the world so they require 3 feet of surcharge. Actually, some DOT's require designing for HS25 trucks which have axle loads that are 25% greater than HS20.

 

[BigH]

Actually, I believe that the AASHTO Bridge Code (1996 with 1997/1998 revisions) say that it is a minimum of 2ft of earh fill. They also give how to distribute - one area is for bearing and one application is for overturning and sliding.

 

[dheigher]

Thank all of you for your replies, this gives me exactly what I needeed.

DHeigher