Note: Descriptions are shown in the official language in which they were submitted.
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System for Reinforcing Structure Using Site-Customized Materials
FIELD OF THE INVENTION
The present invention relates in general to reinforcing structures and more
particularly to materials for strengthening existing structures without
substantial
change to the appearance of the structures.
BACKGROUND OF THE INVENTION
Many existing buildings throughout the world are in need of reinforcement to
help them resist damage by earthquake, violent storms, acidic atmosphere,
vibrations due to vehicle traffic, or similar threats. Many older buildings,
especially, were designed to handle large compressive forces but are not
resistant
to lateral forces.
Buildings that are not resistant to sudden lateral force need to be reinforced
for
the safety of people who live or work in, or visit the building. Some
buildings
have considerable historical or artistic value and must be protected from
disasters
and environmental deterioration for their own sakes.
Some methods exist for reinforcing existing buildings. One that is used all
over
the world is wrapping a structure with fiberglass textile that is impregnated
with
epoxy. This method is taught in different forms in US patents 5043033,
5649398,
and 5657595. A means of connecting different components of a structure using
ductile fiber anchors is taught in US patent 7,207,149 and incorporated herein
by
reference.
The methods of patents 5043033, 5649398, and 5657595 are effective and can be
performed with little intrusion on the occupants and visitors of the building
being
reinforced. A disadvantage to these methods is that they use some specialized
materials that are not readily available in all locations. As a result, the
materials
are shipped from centralized distribution centers, sometimes to remote
locations
that are difficult to reach. The shipping and round transportation of heavy
materials adds significantly to the cost of the project.
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Another disadvantage of the wrapping methods is that the materials readily
available on the market are not good matches in color and texture with old
buildings. There are many buildings all over the world that are constructed of
native stone, brick from local clay, or that are coated with plaster made with
local
minerals. As a result, the materials of the methods mentioned above, such as
epoxy and fiberglass, may not match the color or texture of a given building.
Yet another disadvantage to the method discussed above is that some of the
materials, particularly epoxy, are less fire resistant than conventional
stone, brick,
or plaster construction. It is desirable that a method for increasing a
building's
strength should also increase its fire-resistance, or at least not degrade it.
To avoid the disadvantage of the flammability of epoxy or other organic
polymers, the textile could be coated with an inorganic hardenable paste such
as
mortar. However, this leads to a different disadvantage, which is that
inorganic
mortars are alkaline and tend to degrade ordinary fiberglass. Special alkaline-
resistant glass textile is available, but is quite expensive. This has
discouraged the
use of glass textile with mortar for reinforcement of structures. Graphite
carbon
or aramid fiber textiles would be compatible with mortar, but these textiles
are
also very expensive and not widely available in all countries.
SUMMARY OF THE INVENTION
The present invention is a system of materials and methods for reinforcing
structures using some locally derived materials. The system includes a textile
wrap attached to the structure with fiber anchors and a finishing layer of
mortar
made with grit and aggregate that was obtained from sources in the vicinity of
the
structure being reinforced.
The textile is composed of fibrous basalt, which is resistant to alkaline and
compatible with inorganic mortar. The textile is typically an open-weave
fabric
that is strong and ductile. The fabric is attached to the structure in a
ductile
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manner, such as with fiber anchors as taught in US patent 7207149. The fiber
anchors are preferably also created from basalt fiber.
A mortar finishing material is mixed, beginning with a hardenable liquid
matrix,
such as slurry of calcined mineral particles that harden to create a solid
mortar
after being mixed with water. Grit, aggregate, or both are added to the
hardenable
liquid matrix. The grit or aggregate add color and texture to the mortar
finishing
material.
The reinforcing system is intrinsically fire resistant and does not increase
the fire
risk to a structure.
By using grit and aggregate that are mined or quarried locally, it is often
possible
to match the color and texture of the original building very well. The final
appearance of the reinforced structure is relatively unchanged from the
original,
possibly historic, appearance. Further, the ability to use local mineral
materials
saves money on shipping material to a remote location.
Utilizing local minerals for the mortar finishing material is made possible by
the
use of basalt fiber textile and fiber anchors.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a top plan view, partly cut away, of the reinforcement system of
the
present invention, as used to strengthen a wall of a building.
Figure 2 is a sectional view, taken on line 2-2 of Figure 1.
Figure 3 is a top plan view of the reinforcement system of the present
invention,
as used to strengthen an expansion joint of a structure.
Figure 4 is a sectional view, taken on line 4-4 of figure 3.
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DETAILED DESCRIPTION OF THE INVENTION
Figure 1 is a top plan view of the reinforcement system 10 of the present
invention, partly cut away. Figure 2 is a sectional view of reinforcement
system
10, taken on line 2-2 of Figure 1, as used to strengthen a structure 100, for
example a wall 110 of a building.
Reinforcement system 10 include alkaline-resistant textile 20 stretched over
wall
110. Textile 20 is attached to wall 110 with a plurality of fiber anchors 30.
A
mortar 50, containing mineral products preferably obtained in the same
geographic region as structure 100, is spread over textile 20 and fiber
anchors 30.
Textile 20 is preferably a lightweight, mesh fabric, woven or knit of suitable
ductile, strong, and alkaline resistant fibers such as basalt. Conventionally,
structures have been reinforced with fabrics made of glass fibers. Ordinary
glass
fabric must be covered with a protective finishing material that is pH
neutral, that
is, neither strongly alkaline nor acidic. Many alkaline or acidic materials,
including cementitious materials such as mortar and concrete, degrade glass
and
weaken it. For this reason, structural reinforcing systems that include glass
fiber
fabric also typically include a finishing layer of epoxy or polyurethane,
which are
substantially neutral.
Of course, other alkaline-resistant fibers with good ductility and high
tensile
strength may be used to create textile 20 in place of basalt. The choice of
specific
fiber for textile 20 may be made for each application based upon availability,
strength, and cost. Basalt is found to be the preferred material at this time,
but
other materials may become available in the future.
Test results show that system 10 greatly increases the load-bearing ability of
wall
110 even if the weave of textile 20 includes openings as wide as three or four
inches across, although 1 inch across is a more typical size. A plain or twill
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weave with square or rectangular openings has been found to be convenient to
apply and to provide sufficient strength and ductility. Textile 20 is
typically
woven from yarns or bundles consisting of many individual thin filaments of
basalt fiber.
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Textile 20 is stretched over surfaces of various structural elements of a
structure
100 to be reinforced. Panels of textile 20 may be wrapped over interior or
exterior
corners so as to connect different walls 110, or to connect a wall 110 to a
ceiling,
or other combinations as appropriate. Textile 20 may be temporarily attached
to
wall 110 by suitable clips, staples, or adhesive.
In the case of structures 100 that are built of fragile materials, or that
have been
damaged by weathering or environmental degradation, it is preferable that the
mesh opening size be small, such as 0.5 inch across.
Many types of structural element can be reinforced by using textile 20 to
connect
walls 110 to floors or ceilings, columns or beams to ceilings, roofs to walls
110,
and so on.
The next step in the reinforcement method is to permanently attach textile 20
to
wall 110 or other structure using suitable ductile connecting means, such as a
plurality of fiber anchors 30, as are well known in the art. Fiber anchors 30
are
created by boring a hole through an opening in textile 20 and into the
underlying
wall 110. A length of fiber roving, preferably also composed of fibrous
basalt, is
inserted into the borehole with a free end extending above textile 20.
A backfill material, such as grout or polymeric adhesive, is pushed or
injected
into the borehole. The free end of the roving is attached to the outer surface
of
wall 110 and over textile 20, such as with adhesive or mortar. The backfill
material retains the roving within the borehole such that fiber anchor 30
forms a
sort of large pin attaching textile 20 to wall 110. Fiber anchor 30 is the
most
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preferred ductile connecting means for system 10 because fiber anchor 30
spreads
forces over a broad area and so is unlikely to pull out from wall 110 as a
mechanical fastener might, or pull off a section of wall 110 as a surface
adhesive
might.
The final process is to cover textile 10 and fiber anchors 30 with a mortar
finish
coat 50. Mortar finish coat 50 covers textile 20 so that it will not be
damaged by
weather, or snagged. Mortar 50 contacts and adheres to the original surface of
wall 110 through the openings of the weave of textile 20, embedding textile 20
and helping spread any large lateral forces such as from earthquake or wind.
Mortar 50 mechanically holds textile 20 in place near wall 110 but cannot
entirely take the place of ductile connection means such as fiber anchors 30.
Mortar finish coat 50 is largely for creating a uniformly textured and colored
surface for the reinforced wall 110. Conventional epoxy and glass fiber
textile
reinforcement typically gives a structure a smoother texture and slightly hazy
coloration. Although the epoxy can be covered with paint of other finish,
mortar
is not advised due to possible degradation of the glass fiber.
Mortar finish coat 50 works well for replicating the appearance of original
concrete, stucco, or plaster walls 110. With additional modeling and coloring
work, mortar finish 50 can even replicate the appearance of historical stone
or
brick walls 110.
Mortar 50 is customized to suit the structure to be reinforced. Typically,
mortar
50 is based on a matrix of hardenable paste, such as ductile concrete. Uncured
ductile concrete may be termed a slurry, that is, a mixture of solid particles
suspended in a liquid, with sufficient viscosity or surface tension that the
particles
remain suspended for a long time and yield a mixture that can be handled like
a
liquid or paste.
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Ductile concrete is not typically used as a finish coat for homes, historical
buildings, or other structures where appearance is important but a modern
"industrial" look is not desired. However, it is a strong, ductile material
that is
less likely to crack under lateral forces than standard concrete.
Other matrix materials such as organic polymers or other inorganic
cementitious
materials may also be used to create mortar 50.
Generally, building materials such as stone, brick, and adobe are not
transported
farther than necessary. As a result, structures in a given country or
geographic
area tend to have distinctive appearances. To customize mortar 50, it is
preferred
that mineral materials are used that are similar to those used for the
structure
originally.
In the case of historical buildings, it is often desirable to determine the
components of the original materials, such as by microscopic examination or
chemical analysis.
For example, many older public buildings in the American Midwest are of the
tan
stone call Indiana limestone. In the American Southwest, many historical
buildings are of adobe bricks, which vary in color depending upon the iron
content of the local clay.
Thus, to reinforce a structure in the Midwest it might be appropriate to
incorporate ground limestone into mortar 50 to produce a smooth tan surface on
the reinforced structure. In the Southwest, adobe clay or ground sandstone
might
be added to mortar 50 to make it resemble brick or stone.
Mineral materials obtained locally may include sand, clay, gravel, ground
stone,
or mineral colorants. Although the minerals used for customized mortar finish
coat 50 are described herein as locally obtained, it is to be understood that
the
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mineral materials are to be obtained preferably from the same source as the
materials of the original structure. For example, if an historical structure
in
Indonesia was built originally of imported Italian marble, it may be
aesthetically
desirable to obtain material from the same quarry in Italy to customize mortar
50
if reinforcing the structure in Indonesia.
An alternative embodiment of reinforcing system 10 is illustrated in figures 3
and
4. Figure 3 is a top plan view of reinforcement system 10, as used to
strengthen
an expansion joint 122 .of a structure, such as a bridge 120. Figure 4 is a
sectional
view; taken on line 4--4 of expansion joint 122 of figure 3.
Expansion joint 122 is a design feature of bridge 120. It is a gap of a few
inches
width, left between sections of bridge 120 to allow for thermal expansion of
the
bridge material. The gap of expansion joint 122 is typically filled to provide
a
smooth surface for traffic.
The filling of expansion joint 122 must be of a material that is ductile and
will
not interfere with the function of expansion joint 122. The alternative
embodiment of reinforcing system 10 as illustrated in figures 3 and 4 has been
found to be a low cost and very effective way of dressing expansion joint 122.
Expansion joint 122 has been created with a recess 125 to be filled to provide
a
smooth upper surface. To fill expansion joint 122 using system 10 of the
present
invention, a first layer of mortar 50 is laid into recess 125, filling recess
125
approximately halfway. Next, a strip of textile 20, as described above, is
laid over
mortar 50. A second layer of mortar 50 is poured or spread over textile 20 to
fill
recess 125 to the desired level. Mortar 50 may be textured as desired or left
in the
as-applied state. Fiber anchors 30 are typically not required for this
embodiment
of system 10.
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It may be noted that reinforcement system 10, as practiced for reinforcing
structures such as buildings, may be optionally installed similarly to the
method
of filling expansion joints 122. That is, a first layer of mortar 50 may be
spread
on the original wall 110 of the structure, then textile 20 attached over the
first
layer of mortar 50. Fiber anchors 30 are preferably still employed as detailed
above. Fiber anchors 30 are preferably installed after the first layer of
mortar 50.
A second layer of mortar 50 is applied over textile 20 and fiber anchors 30,
then
finished, also as described above.
This method of practicing the present invention is especially useful in the
case of
buildings that are constructed of fragile materials, or that have been
weakened by
weather, degradation by pollution, or earthquakes. Another precaution taken in
the case of fragile buildings is to create a borehole for fiber anchor 30 that
is
deeper than is typically used for a strong matrix such as undamaged concrete.
Although particular embodiments of the invention have been illustrated and
described, various changes may be made in the form, composition, construction,
and arrangement of the parts herein without sacrificing any of its advantages.
Therefore, it is to be understood that all matter herein is to be interpreted
as
illustrative and not in any limiting sense, and it is intended to cover in the
appended
claims such modifications as come within the true spirit and scope of the
invention.
