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.
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.
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%.
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
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
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
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
LESS DAMAGE TO NON-STRUCTURAL
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.
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
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
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.