crawler crane

[trivedi123]

I am looking for some guidance on crawler crane.
Customer wants to use crawler crane on 12" thick concrete slab on grade with soil bearing pressure of 3000PSF.Crane can put a load of 4000psf on concrete slab. Is there any specific design requirement to check slab for crawler crane load?

 

[JedClampett]

You'll need to check punching shear, concrete bearing and the soil pressure. If the crane has metal treads, it will likely tear up the slab. But you're a structural engineer, so you know that.

 

[oldestguy]

I suspect you mean the concrete slab strength is 4,000 PSI. Off hand I suspect no problem. You might want to run the tracks on planks however. A 12 inch thick slab sounds pretty "stout". If the tracks have to impress non uniformly as with a heavy lift, make a grillage of planks at that location for further load spread,.

 

[SlideRuleEra]

Use wooden "mats" between the crane and the concrete. Mats are typically made of large timber (say 12 x 12) that are bolted together into sections about 4' to 6' width. Length so that both tracks are on the mats. Several mats are used so that the crane can "leaf-frog" the mats as it crawls forward. Mats are used both on soft soil and to protect concrete. Without mats, the crawler tracks can wreck the finish of a concrete slab if the crane has to turn while walking on it. Walking in a straight line on adequate concrete is usually ok. For 12" thick slab with NO mats... depends on size of the crane.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[racookpe1978]

If the concrete pad is raised above the ground - and remember the crane tracks will compress the ground 1-2 inches as it crosses the ground towards the pad so there always will be some elevation difference - then there will be a leverage force as the crane tracks try to ride up onto the edge of the pad. That unbalanced force on the edge will "tip" the ground under the pad down as the crane starts on one side of the pad, then levels out when it hits the middle and stops.
However, the ground if wet or compressible under the pad may subsequently allow the whole pad to tip under an unbalanced load of crane + pad + eccentric load on the boom.

Note that only the crane weight itself is what would be crushing the edge of the pad, or tipping the pad as it climbs up that edge. You won't be moving the crane with a load attached I hope.

 

[trivedi123]

Thank you everybody for help.

 

[chicopee]

Sliderule era has the correct way of using a crawler crane at a job site. Nothing else is advisable from people who know about cranes. Also use Shapiro's cranes and derricks book for more answers.