MOVING EQUIPMENT FOUNDATION PAD

[katesENGR]

CLIENT HAS PLASTIC PIPE EXTRUSION HEAD WEIGHING 63 KIPS ON A TROLLEY WHICH RIDES ON TRACKS 4'3" C-C AND CAN MOVE 16 FEET TO ONE SIDE AND BACK AGAIN, NOT MORE THAN ONCE DAILY. ALLOWABLE SOIL BEARING PRESSURE IS YET TO BE TESTED BUT EXPECTED TO BE 1600 PSF. IF A MAT 7 FEET WIDE × 18 FOOT LONG × 16" DEEP IS USED AS THE FOUNDATION, PRELIMINARY CALCULATIONS CONSIDERING A 16" DEEP × 24"WIDE SECTION OF THE MAT AS A BEAM UNDER EACH TRACK, MINIMAL REBAR STEEL IS REQUIRED FOR FLEXURE, BUT MAY NEED REINFORCEMENT FOR DIAGONAL SHEER, TOO. IF THE EQUIPMENT WAS STATIONARY, (PER CRSI) A 12" THICK 4 ½' SQUARE FOOTING WITH ONLY 5 # 5 BOTH WAYS IN BOTTOM WOULD CARRY A COLUMN LOAD OF 28 KIPS WITH NO DIAGONAL SHEER REBAR. ANY SUGGESTIONS?

 

[oldestguy]

You don't say anything about the soil conditions there so how can anyone comment?

 

[BUGGAR]

I suppose you want to design for economy which means your soil design bearing pressure may be high. You have a cyclical load to this design soil design pressure daily. I recommend you engage a geotech.

 

[katesENGR]

. ALLOWABLE SOIL BEARING PRESSURE IS YET TO BE TESTED BUT EXPECTED TO BE 1600 PSF, adequate for the total load of the trolley if it is static. If A 16" DEEP × 24"WIDE SECTION OF THE MAT acts AS A BEAM UNDER EACH TRACK, pressure directly under the trolley exceeds the alloable 1600 psf by 150 psf - build up of soil bearing capacity will be required. With foundation considered as a beam, diagonal shear needs to be addressed as opposed to spot footings of similar load capacity in the CRSI which have no diagonal shear reinforcement.

 

[katesENGR]

seeking opinions about considering the foundation as a beam vice a spot footing