320 W. Maple St., Suite A
Upper Sandusky, OH 43351
Phone: 419-294-5609
Fax: 419-294-6963
E-Mail: san-con1@san-con.com
Slipform is a method of construction that requires a custom-built set of forms for each project. Unlike jumpforming, slipforming usually proceeds 24 hours per day during the pouring stage of the project. Large diameter (greater than 50') silos, square or irregular configurations, or clusters of two or more silos are usually slipform silos.
In this method, a complete and unique form system is fabricated and built on site. The inside and outside wall forms are constructed of wood. These forms are held together and supported by a system of yokes and by the slipform deck. The deck is constructed of structural steel members, which are covered with plywood to provide an area to work off of. Normally, the structural steel members consist of the roof support beams for the actual structure. Once the slipform is complete, these members are attached to or supported by the wall. Theyare left in place to support the roof.
This whole system of deck and wall forms is raised, or slipped, as one intergral unit by a series of either hydraulic or electric jacks. Each jack is centered between the wall forms and climbs on a steel jackrod that is left in place in the concrete wall. The jacks are attached to the yokes to tie the whole system together.
The entire slipforming operation is usually continuous from start to finish. The rate of "slip" will be dependent on several factors, including wall thickness, complexity of structure, weather, quantity of embeds, and blockouts to be placed in the walls. Most slips will average between 10" and 15" per hour. The initial "set time" for the concrete being poured in the walls, which reinforces the jackrods that support the structure, is another critical factor.
After the slip is completed, or "topped-out", the form system is still supported by the jacks and jackrods. The finished wall is then given a day or two to gain sufficient strength. When ready, the deck structural support system is attached to the walls to support the roof to be constructed later, and the forms, yokes, jacks, etc. are removed. The balance of the work to be performed on the project can then proceed under normal construction methods and practices.
