Foundation, Concrete and Earthquake Engineering

Metal Forms Integrating Dowel Brackets for Casting Deeper Concrete Aporn

Metal forms can be engineered to incorporate special features such as dowel brackets and extensions to pour deeper edges  have simplified the job of paving like 18” thickness apron.

The paving process began by aligning the forms on a four-inch asphalt base, which was laid over a limestone sub-base. Once the forms were aligned, metal stakes were driven with a jackhammer to hold them in position. The stakes were locked to the forms with two opposing wedges in a pocket, which made removal easy once a section was paved.

Another innovation is a separate dowel bracket that holds 1-1/2” diameter smooth metal dowels in alignment perpendicular to the form sections. To avoid wet-set of the dowels a special technique is applied.
Metal Forms Engineered With Dowel Brackets
The drawback of wet-set is if dowels aren’t perfectly straight, they have trouble getting the forms off. With the brackets, the dowels were placed on alternate lanes, and the concrete was poured. Two concrete pumps supplied a Gomaco C-450 cylinder finisher with a 650 flex mix that equates to an eight-sack mix.. Although the  Gomaco machine did most of the finishing Additional hand finishing is required around the structure collars. Once the concrete was cured, the forms were removed while leaving the dowels in place. Then, 2” steel tubing was placed on top of the concrete for the Gomaco machine while the remaining lanes were poured. This way, no dowels had to be wet-set, the forms were easy to remove, and the dowels were held in place by the concrete placed first while the second set of lanes was paved.

Practicle example is paving an 18” thick concrete apron that measures approximately 300 ft. x 600 ft. near the Southwest terminal of the Oakland airport. The apron, part of an expansion designed to handle UPS aircraft, consists of seven 40-ft. bays 650 ft. long, totaling approximately 10,000 yards of concrete.

Paving Contractor
M.F. Maher Construction, headquartered in Vallejo, California
18” but it is specified to be 21” thick around the perimeter to provide added strength.
Forms designer
White Cap Construction Supply, worked jointly with M.F. Maher.
Forms specifications
Metal Forms developed special forms that accommodate the 18” depth of the pavement but also include a 4-1/2” height extension to handle the 22-1/2” perimeter depth.  Brian Wear, of M.F. Maher, says, “The area has a 10-foot transition from 1” to 22-1/2” around the edge. I didn’t want to buy separate 22-1/2” forms, so they engineered an extension that fits on top.

No comments:

Post a Comment