Static structures (e.g. – buildings) – Openwork; e.g. – truss – trellis – grille – screen – frame – or... – Spacer-positioner; e.g. – rebar chair
Reexamination Certificate
2002-02-21
2003-06-03
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Openwork; e.g., truss, trellis, grille, screen, frame, or...
Spacer-positioner; e.g., rebar chair
C052S686000, C052S431000
Reexamination Certificate
active
06571526
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to positioning vertical reinforcement bars within concrete masonry walls. More specifically, the present invention relates to a positioning device that can be placed around a vertical reinforcement bar after the bar has been positioned within the concrete masonry wall, without having to thread the positioning device over the uppermost end of the reinforcement bar or thread a bar through a positioning device.
2. Description of the Related Art
Concrete masonry is a versatile construction system. Modular by design, concrete masonry walls can economically and readily accommodate adjustments of structural design in the field and to the final design of a construction project. For example, the masonry walls can be formed of concrete blocks that have internal, vertically extending cavities and walls made of the vertically stacked blocks are reinforced by placing rebar or other bars composed of structural grade materials through vertically aligned cavities of the blocks and filling the cavities about the bars of the walls with grout. The grout locks the bars to the blocks and this provides the wall with increased strength and ductility, providing increased resistance to applied loads.
The development of reinforced masonry has allowed the use of tall masonry walls for gymnasiums, warehouses and other like structures. Concrete masonry is well suited to wall construction utilized in load bearing applications due to its inherent durability, compressive strength, economy, and resistance to fire, termites and noise. Empirical design methodology is often used to design plain concrete masonry walls. Concrete masonry walls provide support for the structure above by transferring vertical loads to the footing. Vertical compression counteracts flexural tension thus increasing the walls resistance to flexure. In low-rise construction, these vertical loads are typically small in relation to the compressive strength of concrete masonry. Concrete masonry walls of greater height or concrete masonry walls resisting greater soil loads are typically reinforced.
A typical construction project begins with an excavation for a footing and casting concrete footings against the undisturbed soil. Preferably, reinforcement bars are mounted in the footing, by imbedding the lower ends of the bars in the footing at predetermined intervals along the length of the footing. After the footing has been set, the first course of masonry blocks is laid atop the concrete footing. The first course of masonry blocks is bonded directly to the top of the concrete footing with a full bed of mortar. If the blocks are open ended blocks, at least some of the open ends of the blocks are placed in straddling position about the bars. Otherwise, the cavities of the blocks are threaded downwardly about the bars and placed on the last course of blocks. Subsequent courses are laid on top of the first course and clean out openings are provided in the first course of blocks. Mortar is applied to the upper surfaces of the side walls and to the upper surfaces of the cross webs that extend between the side walls of the blocks to later confine the fluid grout that will be poured into the aligned cavities.
Bar positioners are placed in the internal cavities of blocks of the wall that are occupied by reinforcement bars before the grout is poured down the cavities. The bar positioners are used to make sure the reinforcement bars will be properly positioned in the aligned cavities of the blocks. As the wall increases in height, additional reinforcement bars are required and are spliced to the upper ends of the lower bars and additional bar positioning devices are utilized, as required.
After the vertical steel reinforcement bars are centrally positioned in the aligned cavities of the blocks in the wall, grout is poured into the aligned cavities about the bars and through the positioners to the desired depth. The grout lift is allowed to consolidate and then a second lift of grout is placed and consolidated, if needed. This process continues until the internal cavity to be grouted is completely filled. Grout is an essential element of reinforced concrete masonry block construction. The grout bonds the masonry units to the steel reinforcement so they act together to resist loads.
The proper positioning of the steel reinforcement bar within the grouted cell is a serious problem that goes virtually un-addressed in most field construction operations. Proper positioning of a reinforcement bar within the internal cavity requires maintaining the bar's position both prior to and during grouting operations in order to keep the bar within engineer specified tolerances. Existing products that are available to the engineer and contractor frequently are not used because the products are inefficient, complicated to use, and require time consuming efforts to install them properly.
More specifically, existing steel reinforcement bar positioning devices currently available for use are manufactured of wire and allow for movement of the bar within the internal cavities of a masonry wall. This should concern the engineer in charge of the construction of the wall because of the specified tolerances that are required to be met for reinforcement bar placement. Also, as a wall is being constructed, the typical prior art bar positioning devices have to be threaded longitudinally about a reinforcement bar or else a bar has to be inserted through a previously installed device and dropped into place. Thus, existing bar placement devices are oftentimes not used because they are cumbersome and complicated to use. Also, if the top of a reinforcement bar is too high for a worker to reach in order to thread a positioning device over it and into the desired position, the positioning device is oftentimes purposely and arbitrarily eliminated.
Another problem with the use of most existing bar positioning devices is that the ends of the bar positioning devices are embedded within the mortar joint between two adjacent blocks. This can present a problem in that the placement of the second block on top of the mortar joint that includes the positioning device can affect the position of the positioning device by moving it out of position within the mortared joint. This might cause the bar to be held in an off centered position.
As previously noted, vertical reinforcement bars are frequently required to be inserted into the internal cavities and through the previously installed bar positioners prior to grouting. This means that the bar positioning devices would have to be in place between the masonry blocks as the wall is constructed and once the wall is constructed the reinforcement bars are then blindly threaded through the bar positioning devices. This is a complicated procedure and it is difficult to guarantee that the bar is in its proper position.
The positioning of the reinforcement bars is critical to the quality and structural integrity of the masonry wall. Quality control on-site is often lacking because of labor quality and communication amongst the workforce (masons, ironworkers and laborers). What is needed is a reinforcement bar positioning device capable of holding the reinforcement bars in their proper position prior to grout placement, during the rigorous placement of the cementacious grout and capable of remaining in-place within the monolithic grout column as an integral part of the structure. With this in mind, the positioning device should be manufactured of materials, e.g., steel, plastic, or a combination thereof, compatible with the grouts, masonry block and steel reinforcement. As well, the positioning device should be easy to install, economical to manufacture, economical to ship, and be capable of being placed around and not over a previously positioned reinforcement bar.
BRIEF SUMMARY OF THE INVENTION
Briefly described, the present invention relates to a positioning device for positioning a reinforcement bar within the cavity of a masonry block. The positioning device
Friedman Carl D.
McDermott Kevin
Thomas Kayden Horstemeyer & Risley
LandOfFree
Concrete masonry unit (CMU) vertical reinforcement and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Concrete masonry unit (CMU) vertical reinforcement and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Concrete masonry unit (CMU) vertical reinforcement and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3155957