Static structures (e.g. – buildings) – Processes – Requiring soil work
Reexamination Certificate
1997-04-09
2003-04-22
Callo, Laura A. (Department: 3635)
Static structures (e.g., buildings)
Processes
Requiring soil work
C052S294000, C249S018000, C249S034000, C249S047000
Reexamination Certificate
active
06550213
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally concerns the forming of concrete slabs with a light-gage-steel form-set that defines a given geometry upon assembly.
The present invention particularly concerns a form set made up, as much as possible, from girt members that are normally, and will normally be, used in the construction of the building atop a concrete slab foundation.
The present invention further particularly concerns hardware that interconnects foundation form members while also fixing the locations of foundation anchor bolt elements in a manner exactly corresponding to connections of the structural frames of the building.
2. Description of the Prior Art
While much prior art can be found in the field of slab foundations and related concrete work, the commercial success of contemporary proprietary systems which form a concrete-slab-on grade is limited. The primary reasons for this are that the proprietary systems tend to be expensive, contrived, and inflexible. Furthermore, forming a concrete slab on a prepared building pad is not a significant engineering feat, and so is generally endeavored with simple boards and stakes.
The board and stake concept offers design flexibility, but it does have significant drawbacks. These drawbacks include: wasted labor to define and check geometry, poor accuracy of surfaces and embedded hardware, difficulty in adjusting form locations after stakes are set, and inconsistent repeatability for multiple units. Back injury, caused by pulling a conventional stake out of the ground, is a common complaint in the foundation business. Poor foundation accuracy is always a concern, and it has a more consequential negative affect on the framing process for a structure of light gage metal members. This is because the framing assemblages of these members tolerate little dimensional error at the points of support.
Established proprietary concrete forming systems include such ones as ‘Metaform’, which are of folded sheet metal. Lengths are generally in 10′ increments, which is the length of the brake that folds the sheet metal. For a long run of perimeter form this results in frequent potential segmental kinks. Conforming to custom dimension and design requires the cutting up of relatively expensive lengths of form. Stakes must be placed only at specific holder locations provided on the forms, and no subsequent relative horizontal adjustment is possible. If a rock or obstruction happens to be at one of these specific locations, then one must compromise either form location or stake support.
Solutions addressing the need to adjust forms relative to stakes include the system disclosed in Canadian patent 1,145,179 by Breitenbach, issued Apr. 26, 1983. This apparatus allows adjustment of form location subsequent to setting of stakes, by a system of supporting yokes consisting of bars, sleeves, and brackets. This type of a solution involves one or a pair of sets of moving parts for each direction of adjustment. Each supporting assemblage is subject to unwanted lateral movement due to the fact that the each of the supporting stake pairs are required to be essentially parallel for vertical adjustment of the yoke, which attaches to them above the forms. Stakes in loose soils simply do not hold up to this kind of side cantilever loading. Even bending of the stakes can be enough of a problem, given the relatively high point of attachment. Each of these assemblages is heavy, clumsy, relatively expensive, and an obstruction to the concrete work, especially for slab-on-grade foundations. There are too many parts to buy, clean, and maintain.
A somewhat simpler proprietary forming method offers subsequent adjustment in the vertical direction only. This is disclosed in U.S. Pat. No. 3,397,494, Waring, issued Aug. 20, 1968. With this system, vertical support to a proprietary perimeter member is provided with rods having machine thread. These rods thread into bearing pads that sit upon the earth, and then support the special cast in place perimeter member directly. No allowance is provided for rod location. It must be directly at a hole in the member, regardless of what local anomaly or rock may be at the ground below that point. The rod supports offer little resistance to uplift from the buoyant forces of concrete placement, because they do not have threads capable of threading into earth, and so are not used in that manner. This support offers essentially no lateral force resistance. In fact, the system requires a redundant conventional perimeter form board with conventional stakes, et cetera, for structural stability. The main purpose of the present invention is to provide placement of a cast in-situ foundation perimeter for a proprietary wall system which requires a special recessed ledge.
For slab-on-grade foundations, most contractors prefer to continue to form with simple boards and stakes, in spite of the drawbacks, because they do not impose a lot of contrivance, have a low initial cost, and provide flexibility in geometry. Those in the trades have grown to accept the challenges of building foundations with a most primitive technology. It is generally understood that foundation construction includes performing redundant efforts at determining geometry, having a difficult time making geometrical adjustments, and then getting complaints about accuracy from the people building the structure atop anyway. In truth, all of these problems really can be solved without forcing a lot of limitations and contraptions upon the foundation builder, as the following discussion will illustrate.
In order to evaluate a new foundation construction practice, it is sensible to first examine some contemporary needs of the industry.
Tract home builders most often build slab-on-grade foundations. Normally, a building pad is created for each unit. This pad is typically graded so as to completely facilitate slab-on-grade foundation construction. Identical unit footprints, and mirrored versions, are repeated often. The foundation forming method should effectively address this circumstance.
Homes built today tend to have more seismic hardware anchored in the foundation than earlier homes did. Increasingly, post-tension slab-on-grade foundations are being built in order to achieve economy at sites having expansive soil conditions. All of the post-tension anchors must be located correctly along the perimeter form, and in conjunction with the conventional hardware embedments. In general, more connections located in a tighter space demands more accuracy of the foundation forming method which locates these items. Additionally, the task of physically locating an element of hardware is performed very often. So, the task must be made to be as easy and repeatable as possible.
A growing number homes are being framed with members of cold-formed light-gage steel. The framing of these homes requires greater accuracy than most foundation contractors will deliver, particularly for the cost effective ‘panelized’ structures (the metal stud walls are framed in a shop and erected at site). For the increasingly common ‘panelized’ structure, a very accurate foundation, to the last hardware embedment, is required for cost effective construction. For repeat units of ‘panelized’ homes, the accuracy must be such that entire buildings and foundations be considered as interchangeable parts, if true production building is to occur.
An important component of foundation accuracy is easy adjustment of location of foundation forms, so that needed adjustments are made rather than ignored. For custom built structures, provision for easy adjustment of foundation forms is significant. This is because, compared to repetitive construction, relatively far more labor tends to be expended on the custom geometry definition. So, the ability to have adjustment after forms are initially set up, provides a big labor savings for even one unit. It is best if all the foundation form support locations can be adjusted simultaneously. This way an entire lightweight forming unit, which is in
Callo Laura A.
Fuess & Davidenas
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