temporary crane loads on top of retaining wall

[Prestressed Guy]

I have an existing retaining wall that I need to analyze for a crane load. The retaining wall was designed for a 50 psf surcharge over the heel. How do you determine the additional lateral pressures on the wall for a point load? This would be the only surcharge on the wall when the crane is present. The crane will be on site less than a day. The wall can be braced with pipe braces if necessary.

 

[aeoliantexan]

See NAVFAC DM-7.2, Figure 11, Page 74

 

[Prestressed Guy]

Thanks for the info.

I do not have a copy of this document. Could you provide a PDF of that page?

 

[fattdad]

dm 7.2 is available on line. Google it. If using Bousinesq equations, you need to double the result. I'd consider two line loads (one for each track) or a series of point loads shaped in two lines (to replicate each track). I'd contrast my result with the rectangle of the 50 psf design surcharge to see if there is stress increase at some depth. Don't know beyond that, 'cause the work's not done.

f-d

¡papá gordo ain’t no madre flaca!

 

[Delijosi]

I suggest that you use Bousinesq equation for point load. Get the distance of the point load from the retaining wall and calculate horizontal loads at depth due to the point load on the wall until horizontal load is zero. You can use horizontal loads at 1m, 2m, 3m etc depth below top of wall. Input these loads into the software you intend to use.

When analysing, i.e when using the horizontal loads, use undrained soil parameters for cohesive soils and drained parameters for coarse soils.

 

[Prestressed Guy]

I used Bousinesq and it was surprising how little affect the crane had on the overall lateral force on the wall. The normal backfill was my far the majority of the horizontal resultant. Did I mention that the wall was 22’ tall restrained wall and originally designed for a max backfill of 11’ prior to the upper floor being cast. The wall was basically a “U” in plan with 15” radius curves separated by 20’ straight sections. I did a FEA and make use of the geometry. The footings are on rock so soil pressure was not a problem. I also called for monitoring the wall with plumb bobs at critical sections. The analysis showed that the wall had capacity for up to 17’ of back fill plus the crane. The crane was in and out today with zero deflection or cracks so all it well.

Thanks for the info.

 

[vulcanhammer]

Just to make it easier in the future, NAVFAC DM 7.2 can be downloaded from

http://www.vulcanhammer.net/geotechnical/foundations.php

Last year I was able to significantly upgrade the copy of DM 7.1 I offer, and am working on doing the same for DM 7.2.

http://www.pz27.net

 

[InDepth]

Also a another solution, you can provide cribbing that rests on top of the wall and then loads a section away from the influence line. Thus an additional axial load on the reatining wall (if not a building wall). See Shapiro's book on Cranes and Derricks.