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BauGrid®  Advantages

PRECISE POSITIONING OF REBAR
Much more precise positioning of boundary reinforcement bars so that BauGrid® confinement reinforcement resists compression buckling forces uniformly throughout the full height of the cage. This is not true with less accurate bent hoops with large dimensional tolerances between adjacent bent hoops.

UNOBSTRUCTED VIBRATOR SPACE
Vertical shaft opening provides an unobstructed route for the passage of the vibrator the full height of the wall or column. Conventional bent hoops with hooks obstruct the passage of the concrete and vibrator.

LESS INSTALLATION LABOR
The continuous BauGrid® ladder ships in very neat and compact bundles as compared to the individual hoops with hooks. Installing one ladder instead of many individual hoops reduces cage assembly labor man hours very significantly.

TALLER CAGES
Because of the inherent accuracy of a welded wire product made in a jig, the cages are very straight and very rigid. Thus, in one rapid and simple operation, four-story high cages are assembled and lifted into vertical position. Because of their rigidity and precision, the rebar cages fit precisely between forms for thin walls all four floors high. Crane time and field labor time is saved because one lift serves four floors instead of traditional two-story lifts. Thus crane time for cage erection is cut in half.

GREATER ASSURED DUCTILITY
Because of the precision of the BauGrids® and the higher breaking strengths available from drawn wire, recent tests have verified that greater ductility can be assured using BauGrids® in place of large tolerance rebar with hooks.

SAVES REBAR
With greater assured ductility available to the designer, it is possible for him to design stronger cages using smaller diameter wire that is much stronger than conventional rebar hoops. This assured ductility gives the structure the ability to "roll with the punches" that is, in essence, it allows the structure to get out-of-phase with the earthquake. Eliminating harmonic resonance magnification allows the designer to use less earthquake reinforcement. These ductility induced lower response accelerations reduce the amount of needed earthquake resisting reinforcement by as much as 40%.

SAFER BUILDINGS
Thus, by assuring reliable ductility to very tight dimensional tolerances, it is now possible to design safer buildings that use much less reinforcement steel than structures designed with traditional hooked bent-hoop confinement reinforcement.

SAVES CONCRETE AND WEIGHT
In contrast to traditional large tolerance hooked bent rebar confinement ties, BauGrid® confinement cages, with their precision and dimensional accuracy, also allow the engineer to design much thinner concrete shearwalls without concern for rebar cage misalignment. The vibrator void space enables the contractor to pour and compact structural concrete in thinner walls with close spaced rebar cages. Thinner concrete shearwalls equate to less dead load and consequently less seismic force to resist which allows the safe use of thinner walls by the designer. Thinner walls not only decrease earthquake reinforcement steel but also reduce the amount of minimum wall reinforcement, which is, by code, directly proportional to the thickness of the wall.

SAVES POURING AND PATCHING LABOR
Even when thicker walls are specified to accommodate the traditional rebar ties, the turned in seismic hooks still inhibit the passage of the vibrator causing substantial increased labor cost associated with the patching of resulting honeycombing. The BauGrid® Reinforcement System, on the other hand, eliminates these patching costs and also reduces the field man hours during concrete pouring because of the greater efficiency of the vibrator used in the pre-determined vertical vibrator space as the pour proceeds, allowing more cubic yards of wall concrete to be poured with fewer field labor man hours of pouring field time.

SAVES COSTS-IN MANY WAYS
Thus, the new BauGrid® confinement reinforcement product provides a much more reliable and higher quality ductile concrete shear wall structure and, at the same time, it reduces reinforcement steel, concrete, field labor and crane time and at the same time improves the building safety.

NOW RELIABLE DUCTILE SHEARWALLS
Geological history in seismic zones around the world with existing mapped faults, make a certainty of the predictability of violent earthquakes with time. To resist these very large lateral forces, structural engineers have recognized the inherent economy of load bearing concrete shearwall buildings. The thin, fire rated concrete walls serve to support gravity forces and reduce floor slab thickness by reducing the length-floor slab span.

ECONOMICAL FIRE AND SOUND BARRIERS
These same thin concrete walls are not only excellent fire barriers but also very efficient sound barriers between rooms and living units. Their resistance to vandalism and damage in low income rental units make yearly costs of repair and maintenance much lower than, say, walls constructed of metal stud and drywall.

LESS DAMAGE TO NON-STRUCTURAL BUILDING COMPONENTS
Until recently, however, many structural engineers worldwide felt load bearing concrete shearwalls were inferior to ductile concrete frames when selecting a structural system to resist violent earthquakes. The results of continuing research and testing done by Professor V. V. Bertero, Professor of Civil Engineering, University of California Berkeley, at the Earthquake Engineering Research Center (EERC) in Richmond, California, indicate that properly reinforced thin concrete shearwalls can develop very desirable earthquake ductile responses similar to the concrete frames but with less distortion and consequently with less damage to non-structural items.

IMPROVED DUCTILITY MEANS GREATER ENERGY ABSORPTION
The factor used to measure the ductility is the mu factor. If a structure has good ductility, it will have a mu equal to three. This term means that the structure can be deformed (deflect horizontally) three times greater than deformation at yield stress in the structural members. This deformation occurs without permanent damage to the structure.

LABORATORY BREAKTHROUGH
The property of improved ductility is very desirable because it allows the structure to "roll with the punches" instead of getting into destructive harmonic resonance with earthquake vibrations. The shaker table tests at the EERC showed that concrete shearwall buildings, with closely spaced confinement ties in the boundary elements at the edges of the shear walls, could provide safer and less costly earthquake resistant multi-story buildings. However, when this laboratory breakthrough was applied in the field, it was found that the use of traditional bent confinement hooked hoops with large shop dimensional tolerances would not give reliable ductility factors above mu equal to three. In essence, as the earthquake forces attempt to burst the ends of the shearwalls during the compression cycle as the shearwall rocks back and forth, the inconsistently dimensioned hoops create an undesirable weak link where the tie is larger than the adjacent ties above and below. Consequently the shearwall will not be reliable because the designer can not count on it to keep resisting the earthquake well beyond its theoretical elastic limit.

QUALITY CONTROL ASSURES RELIABLE DUCTILITY
Close quality control during manufacturing assures the design engineer that during a violent earthquake, his concrete structure will perform at least to the level of ductility that he assumed in his dynamic analysis.

RELIABLE DUCTILITY GIVES MORE ECONOMICAL AND SAFER BUILDINGS
With the BauGrid® Reinforcement System, the structural engineer can now be assured that his multi-storied concrete load bearing shearwall building will "bend but not break". This very desirable, reliable quality of greater ductility now makes it possible to design safer buildings with less concrete, less reinforcement steel and less labor. Combining these BauGrid® generated design improvements with improvements in the construction techniques has resulted in the very important breakthrough in recent construction of multi-story load bearing shearwall buildings in Northern and Southern California.

TUNNEL FORMED DUCTILE BEARING SHEARWALLS
Using steel "tunnel forms" which are heated each night, multi-story ductile concrete shear wall buildings have recently been constructed in record time. A complete floor of an 18-story apartment tower can be constructed in just four days.

SPEED AND ECONOMY
This extremely fast construction system demands crane time management far beyond other slower methods. BauGrid® reinforcement boundary elements, because of their greater height and straightness, require a minimum of crane time. The pre-determined obstruction free vibrator void space in the BauGrid® helps the contractor to meet his very tight daily pour schedule by speeding compaction of the wall concrete as it is being placed minimizing patching labor costs after form removal.

 


Revised: 04/15/04.
Copyright © 2002, 2003, 2004 by Baumann Research and Development Corporation.
All trademarks or product names mentioned herein are the property of their respective owners.

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