Static structures (e.g. – buildings) – Processes – Filling preformed cavity
Reexamination Certificate
2002-03-08
2004-09-21
Friedman, Carl. D. (Department: 3635)
Static structures (e.g., buildings)
Processes
Filling preformed cavity
C052S742140, C175S011000, C175S213000, C175S333000, C408S059000, C408S204000
Reexamination Certificate
active
06792735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is addressed to the processes of structural retrofit of masonry buildings, including masonry of all types and degrees of hardness and consistency, from adobe or other earthen construction to the hard granites, basalts and concretes.
2. Description of Prior Art
The optimization of the Air Extraction core-drilling system design for the processes of structural retrofit use is much different from that of well-drilling or geological systems for open drilling in ground or rock strata. Construction wet drilling of short cores in concrete had been developed from these sources. However, dry, or near-dry drilling of longer cores is essential in many structures and highly desirable in nearly all buildings needing reinforcement. Accuracy and wall protection are emphasized in construction structural applications. Cost is of paramount importance. Removal of cuttings is generally more difficult and critical. Encounters with steel are frequent.
The present patent is a result of further development of the air extraction drilling system and resin grouting technology which were proven to first order in the hardware example of method U.S. Pat. No. 5,497,841 by the same inventor, working with another inventor. The U.S. Pat. No. 5,497,841 patent was entitled “Methods For Coring A Masonry Wall”, FIG.
1
. The specialized technology to accomplish core placement in a larger percentage of structures, expanding its use and efficiency, is the subject of this follow-on patent.
The entire field of structural retrofit through coring of masonry walls, placing reinforcing elements into the cores and filling the cores with a strong adhesive grout, bonding the reinforcement into the structure, has been referred to by engineers as the “Center-Core Method”.
The solvent-based resinous grouts are also an important and indispensable part of the Center Core technology. They are substantially better than cementious bonding adhesives which require wetting of surfaces with water for adequate bonding. There is a considerable quality-control problem with water-based and cementious materials in regard to this wetting requirement, especially as to uniform optimal wetting. Also, even the strongest cementious adhesives require additives and plasticizers for good retrofit bonding. The stronger mixtures of cementious grouting materials also are not liquid enough; i.e., do not have low enough viscosity to fill all the small cracks and voids left by masons in the original construction. Further, the water in water-based grouting materials is the solvent, but it does not carry the adhesive well into cracks and voids to form a network of bonding.
Properly-selected resinous grouts, on the other hand, permit use of excess low viscosity resin over that needed to saturate the grouting sand, which will therefore fill all accessible small cracks and voids, fully integrating the structure wherever the resin can run or be drawn through gravity and capillary action. The excess resin will always rapidly migrate through several feet or more of wall, even through and into the smallest cracks, dependent on the formulations and the procedural techniques used in the installation of the grout. The larger voids are readily filled with the resin-sand grouting mixture through gravity pressure. The grout can also be pumped, under pressure.
The setting resins, properly formulated, are substantially superior to cementious grouts in regard to adhesive strength and in the ability to integrate the steel and masonry, to absorb shock and deformation. The grout ductility and impact resistance may readily be adjusted through formulation variables. Thus, the dry core-drilling system, steel or other reinforcement insertion procedures and associated resin grouting system form an optimal retrofit combination. University testing has shown that this combination usually will increase the wall strength to a much greater level, as much as several times that of the wet-drilling and cementious grouting combination. It is usually stronger than the equivalent original reinforcement applied in new construction to current building codes, depending on the size and spacing of the cores.
The structural engineer should evaluate the number of cracks and voids in the wall as well as the mortar strength and other reinforcement parameters, comparing the structural retrofit being designed with that of test data and earthquake experience available for this specialized Center-Core technology. This comparison data was derived in university and National Science Foundation test reports and an actual earthquake, with the assistance of the inventor. The correlation of this data will allow the capable engineer to empirically select the proper core size and spacing for out-of-plane flexural loading or in-plane shear loading and other design details, as local government codes require.
Confirmation of the specialized Center-Core method as embodied in the earlier patent was established in the responses of the Center-Core retrofitted walls of six buildings within 12 to 20 miles of the earthquake epicenter in Northridge, Los Angeles, Calif., Jan. 17, 1994. This was a Richter 7 level earthquake. None of these Center-Cored buildings sustained even structural cracking in Center-Cored areas, while buildings around them cracked badly and structural failures with cracking and even partial collapses were common among masonry buildings in the same area. Many of the buildings around those with Center Core had received some strengthening measures, but without any type of wall strengthening.
The Center Core method applies to all masonry materials, but it is optimized more for the softer materials which are more common, worldwide, such as brick, soft sandstone and limestone, adobe, terra cotta and the like. It is less optimal, but still substantially preferable in most under-reinforced harder materials such as concrete, concrete block, or rock, including granite and basalt building materials. It has been applied in all such buildings; over 80 buildings have successfully received the method. Over 50 of these buildings were retrofitted by this inventor team with no quality control problems, whatsoever. Most of the remainder were almost certainly by U.S. Pat. No. 5,497,841 patent infringers. A few were by concrete wet drilling companies who had many problems in schedule delays, cost overruns and job failures.
The method also allows cutting of steel, including reinforcement, pipes, framing, hangers, lintels and the like, included in masonry structures and often not noted in original or present building plans, specifications and drawings.
In harder materials, use of water or other liquids in a mist as a coolant, or as coolant foams are often more efficient because of the superior cooling properties of these media, especially with the use of diamond bits. If possible, the water or foam is injected to just humidify and cool the air, but allow it to dry and keep the cuttings from caking after passing through the hot bit assembly.
The method of the basic patent in the air extraction of cuttings is employed insofar as possible in much the same way as with softer materials. Bits for harder materials usually have diamond cutting elements, while softer materials most often may be drilled with carbide elements. In all structural core-drilling applications it is highly desirable, and most often mandatory, to avoid employing water under high pressure to prevent mortar damage, masonry unit loosening and blowout, and water stains in exteriors and interiors. However, a limited use of coolants, usually water, in the Center Core air extraction method of the former patent in harder materials, as a mist or vapor in the air, or foam, can be advantageous.
The improvements and innovations herein patented are designed to illustrate and characterize, but not exhaustively record all usable configurations of the better novel hardware methods and system solutions for structural core drilling and resin grouting. The hardware applicability is primarily addressed to historic
Fischer Morland C.
Friedman Carl. D.
Horton Yvonne M.
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