Horizontal force on a retaining wall from a vertical point load
Horizontal force on a retaining wall from a vertical point load
(OP)
Hello there, first time post from a very new civil engineer:
I'm designing a mass concrete wall which will act as a headwall to a culvert. Farm machinery is expected to pass over the culvert within 0.5-1m. The wall is only 1.2m high.
I was thinking I should design the wall assuming the vehicle wheels will act as a point load, a distance from the wall and this is transferred to a horizontal load.
I've seen a few formula that tell me the horizontal stress, which I can see varies with depth but I guess I need the total force. Is there a formula for this? Should I be designing as a point load or is a strip load more appropriate.
Any help much appreciated.
I'm designing a mass concrete wall which will act as a headwall to a culvert. Farm machinery is expected to pass over the culvert within 0.5-1m. The wall is only 1.2m high.
I was thinking I should design the wall assuming the vehicle wheels will act as a point load, a distance from the wall and this is transferred to a horizontal load.
I've seen a few formula that tell me the horizontal stress, which I can see varies with depth but I guess I need the total force. Is there a formula for this? Should I be designing as a point load or is a strip load more appropriate.
Any help much appreciated.





RE: Horizontal force on a retaining wall from a vertical point load
The headwall should also be designed for a lateral force from an accident.
RE: Horizontal force on a retaining wall from a vertical point load
You can use a computer program called STRESS or charts in NAVFAC DM7.02 to calculated the horizontal stresses in your elastic medium (the wall backfill) at the back of your wall. You typically get a stress profile distributed in a "teardrop" shape. Combine the magnitudes of each load, draw a diagram showing the distribution of the total horizontal load, integrate it to figure out the total load, and simplify the distribution to facilitate design (sometimes an inverted triangle makes sense).
What you should think about, however, is the stresses you calculate from STRESS or the charts assume that your wall is fixed. If it is free to deflect, the actual surcharge loads will be less. Sometimes I justify using 3/5 of the calculated horizontal stresses, which is near the ratio of the active/at-rest earth coefficients. Of course, you can use the full load and know you are conservative.
RE: Horizontal force on a retaining wall from a vertical point load
Which AASHTO code and what section, thanks
RE: Horizontal force on a retaining wall from a vertical point load
Mike McCann
MMC Engineering
RE: Horizontal force on a retaining wall from a vertical point load
This according to my earth pressure professor, J. Mike Duncan.
f-d
¡papá gordo ain't no madre flaca!
RE: Horizontal force on a retaining wall from a vertical point load
RE: Horizontal force on a retaining wall from a vertical point load
f-d
¡papá gordo ain't no madre flaca!
RE: Horizontal force on a retaining wall from a vertical point load
I think that you need to increase the calculated stesses using Bousinesq in consideration of the elastic 1/2-space effect. I also read something as BigH did, and have the paper in my files somewhere, indicating that 2X may be unrealistic, and this was based on data from a rigid wall, fixed from rotation, with strain gauge instrumentation - seemed credible to me.
The point is, I believe you should increase the horizontal stresses you calculated using Bousinesq. I increased the load in my previous analyses(but forgot to mention that in my previous post).
Better yet, why bother with Bousinesq? You can us the semi-empierical chart solutions in NAVFAC that are specifically applicable to wall surcharges (which do consider the effect of the elastic 1/2-space effect - I have verified in the past). However, at that point, you should consider reducing the horizontal stresses associate with wall deflections (as I mentioned in my previous post). In fact, NAVFAC, although oversimplified, has some discussion on this topic (in the retaining wall section - 7.02). I encourage us all to review this.
In the end, I bet Duncan has the most insight on this, but that he would agree (with the discussion in NAVFAC) that you need to reduce the calculated horizontal stresses depending on your judgement regarding the effects of slight wall deflections on the stresses - assuming such deflections are tolerable.
RE: Horizontal force on a retaining wall from a vertical point load
I really haven't looked at the NAVFAC charts on this matter, but likely should.
f-d
¡papá gordo ain't no madre flaca!
RE: Horizontal force on a retaining wall from a vertical point load
Article 3.11.6.4 of the AASHTO LRFD Specification, 3rd Edition.