Reinforcing member for civil and architectural structures

A reinforcing member for civil and architectural structures is made up of a mixture of reinforcing fibers and thermoplastic fibers which become thermoplastic at a temperature which is lower than a temperature at which the reinforcing fibers become thermoplastic. The thermoplastic fibers may be mixed into each bundle of the reinforcing fibers. The mixture may be formed by arranging respective fiber bundles of the reinforcing fibers and fiber bundles of the thermoplastic fibers. It may also be made by mixing the thermoplastic fibers and an electrically conductive heat-generating wiring material into the reinforcing fibers.

BACKGROUND OF THE INVENTION 
This invention relates to such a reinforcing member for civil and 
architectural structures as is used for reinforcing beams and columns of a 
building, and structures such as piers of a bridge, chimneys, or the like. 
Conventionally, it is normal practice, in reinforcing existing civil and 
architectural structures such as columns and beams of a building, a 
chimney, or the like, to wind reinforcing bars or wires around the 
portions to be reinforced and, thereafter, to coat their surfaces with 
mortar or paint for corrosion prevention of the reinforcing bars or the 
wires. 
The applicants of this application previously proposed in Japanese 
Published Unexamined Patent Application No. 290150/1986, Japanese 
Published Unexamined Patent Application No. 7655/1987 and U.S. Pat. No. 
4,684,567 the following reinforcing member for civil and architectural 
structures in order to improve the disadvantages of the reinforcing bars 
and wires to be used in the civil and architectural structures in that 
they are easily subject to corrosion and are heavy. Namely, the proposed 
reinforcing member is made up by forming into braided cords or ropes 
chemical or man-made fibers having a relatively large tensile strength 
such as carbon fibers, glass fibers, aromatic polyamide fibers or the 
like, and then hardening them by impregnating them with a thermoplastic 
resin. 
However, the method of reinforcing by winding the above-described 
reinforcing bars or the like around the portion to be reinforced has the 
following disadvantages. Namely, it is not economical in that the coating 
work for corrosion prevention is time-consuming and expensive. In 
addition, since the lifetime of the coating is short, it becomes necessary 
to perform repairs again at a later date and, consequently, the structures 
are more likely to be damaged, than leaving them unrepaired, by the 
increase in weight in the repaired portion due to the weight of the added 
reinforcing bars or wires. 
Further, it was once considered to be advantageous to use the reinforcing 
members made up of the above-described chemical fibers in minimizing the 
increase in weight of the repaired structures. However, since the 
reinforcing member is in the form of a bar which is hardened by 
impregnation of a resin, it has been found difficult to wind it around the 
structures, such as columns, to be repaired. 
SUMMARY AND OBJECT OF THE INVENTION 
This invention has an object of providing such a reinforcing member for 
civil and architectural structures as will not require coating for 
corrosion prevention and is small in increase in weight. This invention 
has still another object of providing a reinforcing member which can be 
easily wound around the portion to be repaired and which does not require 
repeated repairs. 
In order to attain the above objects, this invention provides a reinforcing 
member for civil and architectural structures, the reinforcing member 
being constituted by braiding bundles of reinforcing fibers into a braided 
fiber body, wherein the braided fiber body is made up of a mixture of the 
reinforcing fibers and thermoplastic fibers the thermoplastic fibers being 
meltable at a temperature which is lower than a temperature at which the 
reinforcing fibers are meltable. 
According to a second aspect of this invention, the mixture is formed into 
a braided fiber body by mixing thermoplastic fibers into each bundle of 
the reinforcing fibers. 
According to a third aspect of this invention, the mixture is formed into a 
braided fiber body by arranging respective fiber bundles of the 
reinforcing fibers and fiber bundles of the thermoplastic fibers. 
According to a fourth aspect of this invention, the mixture is formed into 
a braided fiber body by mixing the thermoplastic fibers and an 
electrically conductive heat-generating wiring material into each bundle 
of the reinforcing fibers. 
According to a fifth aspect of this invention, the mixture is formed into a 
braided fiber body by arranging respective fiber bundles of the 
reinforcing fibers and fiber bundles of the thermoplastic fibers which is 
mixed with an electrically conductive heat-generating wiring material. 
According to a sixth aspect of this invention, the braided fiber body is 
arranged into a hollow braid having a hollow portion in the center thereof 
and an electrically conductive heat-generating wiring material is inserted 
into the hollow portion. 
When a column, for example, of a structure is reinforced, since the 
above-described reinforcing member is constituted or constructed by 
bundles of fibers, it is relatively soft and has a good flexibility. It 
can therefore be easily wound around the column. After having wound it 
around the column, both ends of the reinforcing member are fixed to the 
column. Thereafter, when the heat is applied to the reinforcing member by 
means of an appropriate heating device or through electric supply to the 
electrically conductive heat-generating wiring material which is mixed 
into the braided fiber body, the thermoplastic fibers mixed into the 
braided fiber body become molten and are impregnated or penetrated into or 
among the reinforcing fibers. If they are left as they are, they will then 
be hardened in a condition of being wound around the column, resulting in 
a stable condition in which the reinforcing member is not displaced or 
removed in position. The hardened reinforcing member performs the same 
function as that of the reinforcing bars which are wound around the 
column. In case there occurs in the column a force of expansion in the 
radial direction, the force is supported by the reinforcing fibers of 
larger tensile strength to thereby prevent the column from deforming in 
the radial direction.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
An explanation is now made about preferred embodiments of this invention 
with reference to the accompanying drawings. In FIG. 1 numeral 1 denotes a 
reinforcing member civil and architectural structures according to this 
invention. This reinforcing member 1 for civil and architectural 
structures uses eight pieces of fiber bundles 2. Each of the bundles 2 is 
formed by mixing a plurality of reinforcing fibers having a large tensile 
strength of, e.g., 100 kg/mm.sup.2 or more and a plurality of 
thermoplastic fibers and then laying them together in the longitudinal 
direction. These fiber bundles 2 are braided together as shown in FIG. 1 
to obtain the reinforcing member 1. As the above-described reinforcing 
fibers, the following can be used either singly or in combination, namely, 
for example, inorganic fibers such as carbon fibers, glass fibers, ceramic 
fibers or the like, and organic fibers such as aromatic polyamide fibers, 
polyamide fibers, or the like. As the above-described thermoplastic 
fibers, those fibers which have thermoplasticity at a relatively low 
temperature which is slightly above 200.degree. C., such as nylon, 
polyester, polyethylene, or the like can be used. Considering the 
heat-resisting temperatures of the reinforcing fibers, those thermoplastic 
fibers which become thermoplastic at a lower temperature than the 
heat-resisting temperatures are selected. Preferably, such fibers as will 
become thermoplastic at a temperature which is lower by 100.degree. C. or 
more than the heat-resisting temperatures of the reinforcing fibers are 
selected as the thermoplastic fibers. 
In more detail, carbon fibers, glass fibers, ceramic fibers and polyamide 
fibers do not normally melt until above about 400.degree. C. Therefore, 
when these fibers are used as the reinforcing fibers, any one of nylon 
which becomes thermoplastic at about 200.degree. C., polyester which 
becomes thermoplastic at about 230.degree. C. and polyethylene which 
becomes thermoplastic at about 110.degree. C. may be mixed with the 
reinforcing fibers as the thermoplastic fibers. 
The reinforcing member 1 having the above-described constitution or 
construction is relatively rich in flexibility. When a column 3, for 
example, shown in FIG. 2 is reinforced, the reinforcing member 1 is wound 
around the column 3 at an appropriate pitch while giving it a tension, and 
both ends 1a, 1a thereof are fixed to the column with a suitable means. A 
heating device 4 comprising a belt-like heater such, for example, as shown 
in FIG. 3 is wound on an external surface of the reinforcing member 1. 
When the heating device 4 is charged with electric power from an electric 
power source 5 so that the thermoplastic fibers in the reinforcing member 
1 are heated to a temperature at which the thermoplastic fibers become 
thermoplastic, the following change will occur. Namely, a condition in 
which the reinforcing fibers 6 and the thermoplastic fibers 7 are simply 
in contact with each other as schematically shown in FIG. 4 is changed to 
a condition in which the reinforcing fibers 6 around the thermoplastic 
fibers become adhered or bonded to each other as shown in FIG. 5 due to 
the thermoplastic characteristics of the thermoplastic fibers. When the 
electric power supply to the heating device 4 is stopped when the 
above-described condition has been attained, the thermoplastic fibers 7 
are cooled and hardened while keeping the reinforcing fibers adhered or 
bonded therearound. As a result, the thermoplastic fibers 7 are provided 
with rigidity and, therefore, the reinforcing member 1 will no longer be 
easily displaced or removed off the position where it is wound around the 
column 3. Needless to say, it is possible to use as the heating device 4 a 
known heating means such as an infrared lamp or the like, in place of the 
belt-like heater. 
The temperature at which the heating device 4 heats the thermoplastic 
fibers is controlled within a range in which the reinforcing fibers are 
not softened. If the temperature is controlled to a range which is within 
the above-described temperature and which yet melts the thermoplastic 
fibers, the molten resin of the thermoplastic fibers is widely spread 
among the reinforcing fibers, resulting in a favorable increase in the 
adhering or bonding characteristics of the reinforcing fibers. 
A second embodiment of this invention as shown in FIG. 6 is a reinforcing 
member 1 which is a braided arrangement of fiber bundles 8 of the 
reinforcing fibers and the fiber bundles 9 of the thermoplastic fibers. 
The reinforcing member of this arrangement can also be used in a similar 
manner as the above-described first embodiment. 
In more detail, the fiber bundles 8 of the reinforcing fibers were made by 
aromatic polyamide fibers, and the fiber bundles 9 of the thermoplastic 
fibers were made by polyethylene. Four pieces each of these fiber bundles 
8, 9 were arranged into a braided fiber body having a mixing ratio by 
weight of about 1:1, thereby obtaining the reinforcing member 1. Each of 
the fiber bundles 8, 9 had a size of 300000 denier. The reinforcing member 
1 had a diameter of 8 mm and was able to be bent into a circle having a 
radius of 10 mm. This reinforcing member 1 was wound around a test piece 
concrete column which had a diameter of 280 mm and a length of 800 mm at a 
pitch of 100 mm and both ends thereof were fixed to the concrete column. 
The reinforcing member 1 was then sequentially heated from one end thereof 
at 200.degree. C. The thermoplastic fibers were impregnated, through 
melting, into the spaces among the reinforcing fibers. With the hardening 
of the molten thermoplastic fibers, the reinforcing fibers were also 
hardened to have a rigidity while they were maintained in a predetermined 
wound position. This test piece concrete column is ordinarily expected to 
rupture under a load of 7 tons, but was able to be subjected to a load of 
up to 12 tons, where it ruptured. Since the reinforcing member 1 has a 
good flexibility before it is hardened, it can be used for reinforcing 
civil and architectural structures of concrete make which has a radius 
above the bending radius of the reinforcing member. 
A third embodiment of this invention is schematically shown in FIG. 7. The 
reinforcing member 1 is formed by further mixing an electrically 
conductive heat-generating wiring material 10 made of one or a plurality 
of electric resistance heating members such as a carbon fiber, Nichrome 
wire or the like into the fiber bundles 2 of the reinforcing fibers 6 and 
the thermoplastic fibers 7 that are shown in FIG. 4. These fiber bundles 2 
are arranged into a braided fiber body as shown in FIG. 1 to obtain the 
reinforcing member 1. This reinforcing member 1 is similarly used by 
winding around a structure as shown in FIG. 2. When the electrically 
conductive heat-generating wiring material 10 is heated through electric 
supply from a non-illustrated electric power source, the thermoplastic 
fibers 7 become either thermoplastic or molten to thereby adhesively 
combine or bond the surrounding reinforcing fibers 6, and are hardened. In 
this embodiment, the heating device 4 is not required during the 
reinforcing work as in the above-described embodiments, resulting in a 
simpler or easier reinforcing work. The heat-generating temperature of the 
electrically conductive heat-generating wiring material 10 can be 
controlled by the amount of electric power to be supplied thereto. Carbon 
fibers are normally heated to a temperature of 100.degree.-250.degree. C. 
As shown in a fourth embodiment in FIG. 8, it is also possible to mix the 
electrically conductive heat-generating wiring material 10 with 
thermoplastic fibers to obtain fiber bundles 11. These fiber bundles 11 
can thereafter be formed into a braided fiber body by arranging them with 
fiber bundles 8 of reinforcing fibers alone to obtain the reinforcing 
member 1. 
When several sets of fiber bundles are arranged into a braid, it is 
possible to arrange them while leaving a hollow portion in the center 
thereof. In this case, as in a fifth embodiment shown in FIG. 9, it is 
possible to insert one or a plurality of electrically conductive 
heat-generating wiring material 10 into the hollow portion 13. In this 
embodiment, as the fiber bundles 14, either a mixture of the reinforcing 
fibers and the thermoplastic fibers or separate bundles of the reinforcing 
fibers and the thermoplastic fibers, respectively, are used. In this fifth 
embodiment and in the above-described fourth embodiment, the reinforcing 
fibers can also be adhesively combined or bonded through the electric 
power supply to the electrically conductive heat-generating wiring 
material. Therefore, an extra heating device is not required. 
The diameters of the reinforcing fibers used in these embodiments are 6-10 
.mu.m and the diameters of the thermoplastic fibers are 6-10 .mu.m. In the 
first embodiment shown in FIG. 1, the reinforcing fibers and the 
thermoplastic fibers were made to be equal in number with a fineness of 
6000 denier. They were then bundled to make fiber bundles and 8 pieces of 
the fiber bundles were arranged into a braided fiber body of about 8 mm in 
diameter. 
According to this invention, as described hereinabove, since the braided 
fiber body of the reinforcing member is made up of a mixture of the 
reinforcing fibers and the thermoplastic fibers which are mixed into the 
reinforcing fibers, the braided fiber body can be easily wound around the 
portion to be repaired in the structures. Further, the thermoplastic 
fibers, after the winding work, can be made into a thermoplastic condition 
by heating to combine or bond the reinforcing fibers together. It is 
possible to provide the reinforcing fibers with rigidity by subsequent 
hardening to keep it in a fixed condition in a predetermined position. 
Consequently, the reinforcing work becomes easy. In addition, since the 
reinforcing member is lighter than the reinforcing bars and is free from 
corrosion, the coating for corrosion resistance becomes needless. A 
further increase in weight of the reinforcing member at a later stage is 
therefore prevented, and the repeated repair will not be required. 
Description has hereinabove been made about a round braid, but a flat braid 
can also be used as well. 
It is readily apparent that the above-described reinforcing member for 
civil and architectural structures has the advantage of wide commercial 
utility. It should be understood that the specific form of the invention 
hereinabove described is intended to be representative only, as certain 
modifications within the scope of these teachings will be apparent to 
those skilled in the art. 
Accordingly, reference should be made to the following claims in 
determining the full scope of the invention.