 |
Description  |
|
|
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of reinforcing a concrete made
construction with a reinforcement member to be secured onto a lower
surface of a beam or a floor of a concrete made construction such as a
bridge. The invention also relates to a fixture to be used in such a
method.
2. Description of the Prior Art
A floor of a bridge receives the largest load or stress among parts
constituting the bridge, because moving loads of vehicles are directly
applied thereto in repeated fashion. Thus, a crack running in a single
direction in particular on a lower surface of a floor is developed to
cracks running in many directions, which are further developed like a net,
resulting in spallation of concrete of which a bridge is made.
If such spallation is kept as it is without mending, cracks are further
developed with the result of corrosion of reinforcing steels which would
finally cause the destruction of a construction such as a bridge.
Accordingly, appropriate mending has been carried out in order to avoid
such destruction when generation of initial cracks was found.
For instance, the followings have been conventionally carried out for
mending a construction: introduction of epoxy resin into cracks of a floor
of a bride so that epoxy resin becomes integral with concrete of which the
bridge is made; formation of a layer such as a sheet and a coated film for
preventing water such as rain from penetrating a floor of a bridge;
application of fiber-reinforced plastics (FRP) to tension edges of a
floor; and filling cavities or spallation with cement mortar or resin
mortar.
Those mending methods ensure prevention of degradation of a concrete floor
made of concrete and corrosion prevention of reinforcing steels to some
degree. However, those methods as mentioned above merely ensure mending of
a concrete floor, and do not enhance the strength of a concrete floor.
In order to resolve such a problem, the inventor has suggested a method of
mending and reinforcing a construction such as a floor of a bridge in
Japanese Unexamined Patent Publication No. 61-146904. This method includes
the steps of applying a surface application material onto a surface of a
construction which has been cleaned, covering the surface with a wire
gauze and applying again a surface application material over the wire
gauze.
FIG. 1 is a cross-section illustrating a construction mended and reinforced
by the method disclosed in the Publication No. 61-146904. A floor 521 of a
concrete made construction is covered with a first impregnated layer 522,
is which is covered with a second impregnated layer 523. A wire gauze 524
is fixed over the second impregnated layer 523 with hole-in anchors 525.
The wire gauze 524 is further covered with a first application layer 526,
which is in turn covered with a second application layer 527.
In order for the wire gauze 524 covering the second impregnated layer 523
to act sufficiently as a reinforcement member, it is necessary for the
wire gauze 524 to be sufficiently fixed to the floor 521 by means of the
hole-in anchors 525. Such fixation of the wire gauze 524 to the floor 521
ensures almost the same strength as the strength of a construction
originally including reinforcing steels corresponding in amount to the
wire gauze 524.
The method disclosed in the above mentioned Publication uses the
bolt-shaped hole-in anchors 525, which sandwich an intersection of the
wire gauze 524 between a head portion 525a and a threaded portion 525b
thereof for fixing the wire gauze 524. Although this method eliminates a
risk of falling of the wire gauze 524, it cannot provide sufficient
fixation of the wire gauze 524 to the floor 521.
As mentioned earlier, repeated live loads are always applied to a concrete
floor of a bridge by vehicles passing thereon, and cause the concrete
floor to repeat vertical deflection with maximum deflection occurring at a
center of a span of the bridge. Thus, if the bolt-shaped hole-in anchors
525 are used for fixing the wire gauze 524, there will be produced a gap
between the hole-in anchors 525 and the wire gauze 24 as times go by,
resulting in that it is no longer possible to sufficiently distribute the
loads applied to the floor 521 to the wire gauze 524.
In addition, position of the hole-in anchors 525 for fixation of the wire
gauze 524 onto a lower surface of a concrete made construction is
calculated out in the above mentioned conventional methods. Thus, the
hole-in anchors 525 may be got out of position when the wire gauze 524 is
actually positioned.
SUMMARY OF THE INVENTION
In view of the above mentioned problems of the prior art, it is an object
of the present invention to improve the conventional methods to thereby
ensure the fixation of a reinforcement member. It is also an object of the
present invention to provide a method of reinforcing a concrete made
bridge and a fixture to be used in such a method. It is further an object
of the present invention to provide a reinforcement member which is
capable of easily being fixed, does not need milch of covering material,
and provides excellent reinforcement effects.
In one aspect, the present invention provides a method of reinforcing a
concrete made construction including the steps of provisionally disposing
a reinforcement member onto a lower surface of a concrete made
construction, forming holes at the lower surface of a concrete made
construction, and inserting fixtures into the holes to fixate the
reinforcement member onto the lower surface of a concrete made
construction so that the fixture imparts tension force to the
reinforcement member in a plane of the reinforcement member.
The method may preferably include the step of surface-treating the lower
surface of a concrete made construction with high-pressure water-washing
surface preparation or sand blast before the reinforcement member is
fixated onto the lower surface of a concrete made construction.
For instance, a concrete made construction is a bridge.
By fixing the reinforcement member to a concrete made construction with
tension force being imparted to the reinforcement member in a plane
thereof, there is introduced so-called pre-stress into the reinforcement
member. Thus, even if a concrete made construction to which the
reinforcement member is secured is deflected, the reinforcement member
moves following the deflection of the concrete made construction such as a
bridge, thereby a gap being never generated between the reinforcement
member and a fixture.
In addition, it is possible to insert fixtures into a concrete made
construction with higher accuracy by forming holes to which the fixtures
are to be inserted, with a reinforcement member being provisionally
secured to a concrete made construction relative to a conventional method
in which holes to which fixtures are to be inserted are formed at
positions determined by calculation. Thus, the insertion of fixtures
ensures introduction of pre-stress to a reinforcement member.
When a mesh-type reinforcing steel is to be used as the reinforcement
member, it is preferable to form a covering layer by applying covering
material onto the reinforcement member after the reinforcement member has
been fixed with a fixture such as the above mentioned one, in order to
avoid the reinforcing steels from being exposed to atmosphere and hence
prevent the reinforcing steels from being rusted. The covering material of
which the layer is made may include polymer cement mortar providing
superior adhesion to a surface of a concrete made construction. The layer
can be formed, for instance, by direct application of polymer cement
mortar to a concrete made construction, positioning a frame onto a surface
of a concrete made construction and introducing polymer cement mortar into
the frame, or spraying polymer cement mortar to a surface of a concrete
cement mortar.
It is preferable to construct the above mentioned covering layer of a
multi-layer structure including a base application layer applied onto a
lower surface of a concrete made construction, an intermediate application
layer lying over the base application layer so that the intermediate layer
covers a mesh-type reinforcing steel to be laid onto the base application
layer , and an upper application layer lying over the intermediate
application layer. The base application layer increases the strength of a
lower surface of a concrete made construction, enhances corrosion
prevention effect of reinforcing steels embedded in a concrete made
construction, and increases adhesive force between reinforcing steels and
a concrete made construction. The intermediate application layer provides
rust prevention effect to the mesh-type reinforcing steel and decreases
salt damage of the mesh-type reinforcing steel. The upper application
layer provides neutralization prevention effect, salt damage prevention
effect, alkali-aggregate reaction prevention effect and low
waterpermeability effect.
Specifically, it is preferable to use FK-A (base application) commercially
available from Kyouryo Hozen Inc. for the base application layer, FK-A
(intermediate application) for the intermediate application layer, and
FK-A (upper application) for the upper application layer.
As a reinforcement member, there may be used a mesh-type reinforcing steel
formed by welding steels in a grid or a grating member made of
fiber-reinforced resin. The fiber-reinforced resin includes continuous
fibers such as glass fibers, carbon fibers and aramide fibers. It is
preferable to use as a resin vinyl ester having superior chemical
resistance.
A grating member made of fiber-reinforced resin is available from Nefcom K.
K. under the trade mark of "Nefcom". Nefcom is composed of resin
impregnated continuous fibers such as carbon fibers, glass fibers and
aramide fibers formed in a grid having a pitch of 50 mm, 100 mm or 150 mm.
Nefcom has a specific gravity in the range of 1.3 to 1.7, which is about
1/4 to 1/6 of a specific gravity of steel, almost the same tensile
strength as that of a PC steel stranded wire, which is four to five times
greater than steel, a tensile elastic modulus which is about 2/3 to 1/4 of
that of steel, and a band of elastic deformation which is two to five
times greater than that of a PC steel stranded wire. In addition,
intersections formed by intersecting of gratings has a laminated structure
formed by alternately depositing fibers, thereby providing great bonding
force. It ensures sufficient strength for imparting tension force to the
intersections by means of a fixture. Furthermore, since the intersections
lie in a plane unlike a reinforcing steel, it is possible to make strand
thin.
The reinforcement member made of fiber-reinforced resin is able to be
readily fixed onto a lower surface of a concrete made bridge because of
its light weight. In addition, since the reinforcement member made of
fiber-reinforced resin has smaller surface hardness than steel, even if a
handy drill is accidentally made to contact the reinforcement member, the
reinforcement member is merely shaved slightly at a surface thereof. The
reinforcement member is never got out of position unlike a reinforcing
steel.
In addition, since the fiber-reinforced resin has a band of elastic
deformation which is two to five times greater than that of a PC steel
stranded wire, it is possible to impart higher tension force to the
reinforcement member in a plane thereof without plastic deformation than a
reinforcing steel. Thus, it is possible to enhance fixation of the
reinforcement member to a concrete made construction.
There may be used a reinforcement member to be fixed onto a lower surface
of a concrete made construction by means of a fixture to reinforce the
concrete made construction, which reinforcement member includes tension a
force imparting device for fixing the reinforcement member onto the lower
surface of a concrete made construction with tension force being applied
to the reinforcement member by means of the fixture. The tension force
imparting device is integral with a main body of the reinforcement member.
The tension force imparting device makes it easy to fix the reinforcement
member onto a lower surface of a concrete made construction.
In another aspect, the present invention provides a combination of a
fixture and a reinforcement member both of which are to be used in a
method of reinforcing a concrete made construction including the step of
fixing a reinforcement member onto a lower surface of a concrete made
construction with tension force being applied to the reinforcement member
in a plane thereof by means of a fixture, the reinforcement member being
formed with an inclined guide surface for imparting tension force to the
reinforcement member, the fixture including an aid a part of which makes
contact with the inclined guide surface of the reinforcement member when
the fixture is inserted into a concrete made construction, to impart
tension force to the reinforcement member in a plane thereof.
By inserting the fixture into a concrete made construction, the aid is
moved along the inclined guide surface formed with the reinforcement
member, thereby the reinforcement member being fixed onto a lower surface
of a concrete made construction with tension force being applied to the
reinforcement member in a plane thereof.
In a preferred embodiment, the reinforcement member is comprised of a
mesh-type reinforcing steel formed by welding steels in a grid or a
grating member made of fiber-reinforced resin.
In another preferred embodiment, the reinforcement member includes
vertically extending portions and horizontally extending portions both of
which lie in a common plane.
There may be used a fixture including an insertion portion to be inserted
into a concrete made construction, an arc-shaped head portion, a tapered
portion connecting the insertion portion to the head portion and having a
cross-sectional area increasing from the insertion portion towards the
head portion, and a resin layer covering said tapered portion therewith.
By inserting the above mentioned fixture into a concrete made construction
along an intersection of a mesh-type reinforcing steel, the mesh-type
reinforcing steel in contact with the fixture is made to externally move
along a surface of the tapered portion to thereby impart the tension force
to the mesh-type reinforcing steel in a direction of a plane of the
mesh-type reinforcing steel.
The resin layer covering the tapered portion therewith provides
advantageous effects in particular when fiber-reinforced resin is used as
a reinforcement member. The resin layer prevents intersections of a
reinforcement member made of fiber-reinforced resin from being damaged on
insertion of a fixture keeping in contact with intersections of a
reinforcement member, and reduces friction with intersections to thereby
enhance insertion efficiency.
There may be used a fixture including a device for applying tension force
to a reinforcement member in a plane thereof by moving at least a part of
the fixture in a direction perpendicular to a reinforcement member.
There may be used a fixture to be used for fixing a reinforcement member
onto a lower surface of a concrete made construction, the fixture
including a main body, a support member for fixing the main body to a
concrete made construction, and a device for imparting tension force to
the reinforcement member in a plane thereof by deformation of the main
body caused by pressurizing at least a part of the main body.
For instance, the device for applying tension force includes a shaft to be
fixed to a concrete made construction, and a main body having an inclined
guide surface for applying tension force therewith. The inclined guide
surface imparts tension force to the reinforcement member in a plane
thereof as the main body moves along the shaft.
For another instance, the device imparts tension force to a reinforcement
member in a plane thereof by rotating at least a part of the fixture.
As an alternative, the device for imparting tension force to a
reinforcement member includes a shaft to be fixed to a concrete made
construction, and a main body having the form of an eccentric cam and
rotatably secured to the shaft.
The device may be designed to have a support member to be fixed to a
concrete made construction and a screw being secured to the support
member.
The above and other objects and advantageous features of the present
invention will be made apparent from the following description made with
reference to the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view illustrating a concrete made construction
reinforced by a conventional method;
FIG. 2 is a front view illustrating a bridge to which the present invention
is applied;
FIGS. 3A to 3G are cross-sectional views showing respective step of the
method of reinforcing a concrete made construction;
FIG. 4 is a plan view illustrating a fixture made in accordance with the
present invention;
FIG. 5 is an enlarged view as viewed in a direction indicated with an arrow
A shown in FIG. 2;
FIG. 6 illustrates behavior of a mesh-type reinforcing steel and a fixture
made in accordance with the present invention, caused by deflection of a
floor of a concrete made construction;
FIGS. 7A to 7G are cross-sectional views showing respective step of the
method of reinforcing a concrete made construction;
FIG. 8 is a perspective view illustrating a reinforcement member;
FIG. 9 is a plan view of a fixture made in accordance with the present
invention;
FIG. 10 is a plan view illustrating a reinforcement member;
FIG. 11 is a front view illustrating a concrete made bridge reinforced by a
fixture made in accordance with the first embodiment;
FIG. 12 is an enlarged view as viewed in a direction indicated with an
arrow B shown in FIG. 11;
FIG. 13 is an enlarged view of a part of FIG. 12;
FIG. 14 is a cross-sectional view taken along the line C--C in FIG. 13;
FIG. 15 illustrates behavior of a mesh-type reinforcing steel and a fixture
made in accordance with the present invention, caused by deflection of a
floor of a concrete made construction;
FIG. 16 is a plan view illustrating a grating member fixed with a fixture
made in accordance with the second embodiment;
FIG. 17 is a cross-sectional view taken along the line D--D in FIG. 16;
FIG. 18 is a cross-sectional view taken along the line E--E in FIG. 16;
FIG. 19 is a plan view illustrating a grating member fixed with a fixture
made in accordance with the third embodiment;
FIG. 20 is a cross-sectional view taken along the line F--F in FIG. 19;
FIG. 21 is a schematic view of a fixture;
FIG. 22 is a schematic view illustrating a fixture made in accordance with
the fourth embodiment;
FIG. 23 is a cross-sectional view illustrating a grating member fixed with
a fixture;
FIG. 24 is a cross-sectional view taken along the line G--G in FIG. 23;
FIG. 25 is a plan view illustrating a grating member fixed with a fixture
made in accordance with the fifth embodiment;
FIG. 26 is a plan view illustrating a grating member fixed with a fixture
made in accordance with the sixth embodiment;
FIGS. 27A and 27B are cross-sectional view taken along the line H--H in
FIG. 26;
FIG. 28 is a plan view illustrating a grating member fixed with a fixture
made in accordance with the seventh embodiment;
FIG. 29 is a cross-sectional view taken along the line I--I in FIG. 28;
FIG. 30 is a plan view illustrating a reinforcement member made in
accordance with the present invention;
FIGS. 31A and 31B are cross-sectional view taken along the line J--J in
FIG. 30;
FIG. 32 is a front view of a concrete made bridge;
FIG. 33 is an enlarged view as viewed in a direction indicated with an
arrow K in FIG. 32; and
FIG. 34 is a perspective view illustrating a reinforcement member made in
accordance with another embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments in accordance with the present invention will be
explained hereinbelow with reference to drawings.
With reference to FIG. 2 illustrating a concrete made bridge to which the
present invention is applied, a concrete floor 101 of the bridge is
reinforced with steels and is formed at opposite edges thereof with raised
portions 102. The floor 101 is supported at a lower surface thereof with
three pillars 103. A lower surface of the floor 101 is entirely covered
with a covering layer 109 made in accordance with an embodiment, of the
present invention.
Hereinbelow is explained a method of forming the covering layer 109 with
reference to FIGS. 3A to 3G. As illustrated in FIG. 3A, deteriorated
portions are removed from a lower surface of the floor 101 by means of
water sand blast. Then, the lower surface is washed by high-pressure
water-washing surface preparation in which jet water having a pressure of
200 kgf/cm.sup.2 or greater is used.
Then, as illustrated in FIG. 3B, a mesh-type reinforcing steel 105 is
provisionally supported by a support 120 onto the lower surface of the
floor 101. The mesh-type reinforcing steel 105 is formed by arranging
steels having a diameter in the range of 6 mm to 10 mm into a mesh having
an area in the range of 1.8.times.3 to 1.8.times.4 m.sup.2, and welding
intersections of the thus arranged steels.
Then, as illustrated in FIG. 3C, holes 10a are formed at the lower surface
of the floor 101 at the intersections of the mesh-type reinforcing steel
105. As mentioned later, a fixture is to be inserted into each of the
holes 101a. It is possible to insert fixtures in to a concrete made
construction with higher accuracy by forming the holes 101a with the
mesh-type reinforcing steel 105 being provisionally secured to a lower
surface of a concrete made construction relative to a conventional method
in which holes to which fixtures are to be inserted are formed at
positions determined by calculation.
Then, as illustrated in FIG. 3D, fixtures 106 are inserted and driven into
the holes 101a by means of a vibration hammer to thereby fix the mesh-type
reinforcing steel 105 onto the lower surface of the concrete floor 101.
FIG. 4 illustrates the fixture 106. The fixture 106 is comprised of an
anchor 107 and a pin 108. The anchor 107 includes a rod-shaped insertion
portion 107b to be inserted into a concrete made construction, which
insertion portion 107b is formed at a distal end thereof with an expanding
slot 107a, an arc-shaped head portion 107c, and a tapered portion 107d
connecting the insertion portion 107b to the head portion 107c and having
a cross-sectional area increasing from the insertion portion 107b towards
the head portion 107c. There is formed a through hole 107e axially
extending through the anchor 107. The pin 108 is to be inserted into a
concrete made construction through the through hole 107e. By forming the
head portion 107c of the anchor 107 to be arc-shaped, it is possible to
decrease the projecting length of the fixture 106 from a lower surface of
the floor 101, and thus an amount of covering material to be applied to a
lower surface of the floor 101 can be decreased by about 40% relative to a
conventional hexagonal-shaped bolt.
The size is dependent on a diameter of reinforcing steel constituting the
mesh-type reinforcing steel 105. However, it is preferable that the
insertion portion 107b has a diameter in the range of 6 mm to 8 mm, and
the tapered portion 107d has a diameter in the range of 2 mm to 3 mm.
By inserting the fixture 106 into the concrete made floor 101, the tapered
portion 107d having a cross-sectional area increasing towards the head
portion 107c ensures that the tension force is imparted entirely to the
mesh-type reinforcing steel 105 in a plane thereof in a direction
indicated with arrows in FIG. 5. The tapered portion 107d additionally
ensures the fixation of the mesh-type reinforcing steel 105 onto the floor
101 even when the holes 101a are formed out of position or intersections
of the mesh-type reinforcing steel 105 are disposed out of position. In
the illustrated embodiment, the tension force is directed to outside from
a span center of the floor 101, that is, a point at which the concrete
made construction has a maximum deflection caused by loads to be applied
thereto and its own weight.
Then, as illustrated in FIGS. 3E to 3G, there is formed a covering layer
109. The covering layer 109 includes a base application layer 109a (see
FIG. 3E) applied onto the lower surface of the floor 101, an intermediate
application layer 109b (see FIG. 3F) lying over the base application layer
109a so that the intermediate layer 109b covers the mesh-type reinforcing
steel 105 to be laid onto the base application layer 109a, and an upper
application layer 109c (see FIG. 3G) lying over the intermediate
application layer 109b. The base application layer 109a increases the
strength of the lower surface of the floor 101, enhances corrosion
prevention effect of reinforcing steels embedded in the floor 101, and
increases adhesive force between the reinforcing steels and the floor 101.
The intermediate application layer 109b provides rust prevention effect to
the mesh-type reinforcing steel 105 and decreases salt damage of the
mesh-type reinforcing steel 105. The upper application layer 109c provides
neutralization prevention effect, salt damage prevention effect,
alkali-aggregate reaction prevention effect and low water-permeability
effect. The base application layer 109a is applied by spraying, and the
intermediate application layer 109b and the upper application layer 109c
are formed by direct application onto the base application layer 109a.
FIG. 6 illustrates behavior of the mesh-type reinforcing steel 105 and the
fixture 106 caused by deflection of the floor 101 after the above
mentioned mending has been completed. As illustrated, the fixture 106
imparts the tension force F to the intersection of the mesh-type
reinforcing steel 105 in a direction indicated with an arrow. Thus, the
mesh-type reinforcing steel 105 is given prestresses Fx and Fy in x- and
y-axes, respectively. Thus, when the fixture 106 is caused to move by the
deflection of the floor 101 as shown with an alternate long and short dash
line A1, the mesh-type reinforcing steel 105 follows the fixture 106 as
shown with an alternate long and short dash line A2, thereby a gap being
not produced between the mesh-type reinforcing steel 105 and the fixture
106 unlike the prior method.
A test was conducted to confirm the advantageous effects of the invention.
A reinforcing steel of a concrete made construction had the tensile stress
intensity of 20 tons, whereas a reinforcing steel reinforced in accordance
with the present invention had 0.3 times greater stress intensity than the
stress intensity of a reinforcing steel to which the present invention is
not applied. Namely, there was obtained 70% reduction in tensile stress.
Thus, it was confirmed that the method of the present invention prevents
cracking of a floor of a construction such as a bridge, and hence keeps
effective area of concrete unchanged, thereby preventing degradation of a
floor caused by shearing and fatigue failure as well as bending.
It should be noted that the method of the present invention is not to be
limited to the mending of damaged concrete made construction. For
instance, it is possible to use the present invention for increasing the
strength of a bridge up to 25 tons which bridge is originally designed to
have the strength of 20 tons. In addition, the present invention can be
applied also to reinforcement of a lower surface of a beam or pillar. In
particular, it is most effective to apply the invention to a floor or beam
which is repeatedly deflected by vehicles running thereon when a floor or
beam is being mended.
By fixing the mesh-type reinforcing steel to a concrete made construction
with the tension force being imparted to the mesh-type reinforcing steel
in a plane thereof, there is introduced pre-stress into the mesh-type
reinforcing steel. Thus, even if a concrete made construction to which the
mesh-type reinforcing steel is secured is deflected, the mesh-type
reinforcing steel moves following the deflection of the concrete made
construction, thereby a gap being never generated between the mesh-type
reinforcing steel and the fixture. Hence, the fixation of the mesh-type
reinforcing steel to a concrete made construction can be enhanced, and
thereby it is possible to maintain the reinforcing effect in a long time.
In addition, the present invention ensures the fixation of the mesh-type
reinforcing steel, in particular, to a floor of a bridge which is
deflected during the method is being carried out for reinforcing the
floor.
Furthermore, it is possible to insert the fixtures into a concrete made
construction with higher accuracy by forming the holes to which the
fixtures are to be inserted, with the mesh-type reinforcing steel being
provisionally secured to a concrete made construction relative to a
conventional method in which holes to which fixtures are to be inserted
are formed in advance. Thus, the insertion of the fixtures ensures
introduction of pre-stress to the mesh-type reinforcing steel.
Hereinbelow will be described the method of reinforcing a concrete made
construction by using a reinforce | | |
