Static structures (e.g. – buildings) – Frangible section or means
Reexamination Certificate
1999-10-06
2001-09-18
Cuomo, Peter M. (Department: 3636)
Static structures (e.g., buildings)
Frangible section or means
C052S309100, C248S548000, C248S900000
Reexamination Certificate
active
06289638
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for creating a void under a structural concrete slab in order to protect the structural concrete slab from heaving caused by the upward movement of underlying ground.
BACKGROUND OF THE INVENTION
Structural concrete slabs often require protection from heaving caused by the upward movement of underlying ground. The preferred approach is to create a void space under the concrete slab. These concrete slabs can be supported at intervals on foundations and void forming materials are used to create void spaces between the concrete slab and the ground. Void forming materials must be able to support the weight of fresh concrete, as well as live loads provided by workmen and equipment during the course of construction. At the completion of construction, the void forming materials must begin to break down in order to protect the concrete from heaving ground.
Void spaces have been constructed using wax-coated cardboard honeycomb products that degrade when exposed to moisture. However, jobsite delays or inclement weather can result in premature strength loss of the cardboard product, causing collapse of the concrete before it is self supporting.
Foam plastic materials, such as expanded polystyrene (EPS) have been substituted for cardboard products, as EPS is not susceptible to the elements. However, used as a compressible inclusion, the stress required to deform the EPS is higher than most concrete slabs can withstand. Various attempts have been made to overcome the problem through the use of light density EPS, resulting in lower compressive strength, and also by creating various shaped voids and configurations in the EPS to reduce the cross sectional area in contact with the soil or the slab. All of these efforts have failed to reduce the pressure on the concrete slab to a level that the slab can withstand.
The industry has, therefore, been searching for many years for a serviceable void forming material for the construction of structural concrete slabs.
SUMMARY OF THE INVENTION
What is required is an alternative apparatus for creating a void under a structural concrete slab.
According to the present invention there is provided an apparatus for creating a void under a structural concrete slab which includes a body having a bottom surface with projections which deform and then collapse after a preset displacement in response to subgrade compressive stress.
The apparatus, as described above, relies on the knowledge that the uplifting forces under the slab occur slowly over a period of time. The projections on the bottom surface of the body are capable of supporting a load during the course of construction. However, in response to subgrade compressive stress the projections deform, eventually collapsing.
There are various configurations of projections that can be configured to collapse after being displaced by a preset amount. Beneficial results have been obtained through the use of bent legs which tend to deform sideways. By placing a bend in the leg, an asymmetrical distribution of the force exerted by subgrade compressive stress can be achieved to deform the legs sideways. By placing a notch at the bend on each of the legs, the legs have a tendency to fracture at the bend which accelerates the collapse of the legs in response to subgrade compressive stress. Each leg goes through an initial loading phase, a creep phase and a collapse phase, as will hereinafter be further described.
There are a variety of materials out of which the body may be made. It is preferred that the material selected be water resistant in order to avoid premature collapse in adverse weather conditions caused by excessive moisture. Beneficial results have been obtained through the use of plastic, as will hereinafter be further described.
REFERENCES:
patent: Re. 34220 (1993-04-01), Kennedy et al.
patent: 2737693 (1956-03-01), Robbins
patent: 4119387 (1978-10-01), Brown
patent: 4362428 (1982-12-01), Kerschner
patent: 4685267 (1987-08-01), Workman
patent: 4916878 (1990-04-01), Nicholas
patent: 5339578 (1994-08-01), Smerchanski et al.
patent: 5352064 (1994-10-01), Carruthers et al.
patent: 5568994 (1996-10-01), Dawson
patent: 5588262 (1996-12-01), Dawson
patent: 5699643 (1997-12-01), Kinard
patent: 5782049 (1998-07-01), Gates et al.
patent: 5799455 (1998-09-01), Gates et al.
Beaver Plastics Ltd.
Christensen O'Connor Johnson & Kindness PLLC
Cuomo Peter M.
Tran Hanh V.
LandOfFree
Apparatus for creating a void under a structural concrete slab does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for creating a void under a structural concrete slab, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for creating a void under a structural concrete slab will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2522976