JP3528043B2 - Bridge reinforcement method using reinforcement plate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bridge reinforcing method using a method of introducing pre-stress into a bridge constituent member to perform post tension reinforcement.

[0002]

2. Description of the Related Art In recent years, strict safety and durability standards have been demanded for bridges due to an increase in traffic volume and the weight of passing vehicles, and old bridges that do not meet the new safety and durability standards will be reinforced. There is a need.

Conventionally, the post-tension construction method has been widely used as a means for introducing prestress to a bridge to reinforce it. As shown in FIG. 10, the upper flange 50
When a dead load or a live load is applied to the bridge girder 50 having a, the lower flange 50b and the web 50c, the bridge girder 50 is deformed into an arch, a compressive stress 51 acts on the upper flange 50a, and a tensile stress acts on the lower flange 50b. 52 works. The post-tension construction method is a construction method of introducing compressive stress (pre-stress) in the column direction in the lower flange 50b to relax the tensile stress in order to improve the load bearing capacity of the member on which the tensile stress acts.

As a conventional post tension reinforcing method, for example, as shown in the schematic sectional view of FIG.
The fixing device 61 under the girder of the lower flange 60b of 0,
The external post tension reinforcement construction method in which 62 is used to tension the outer cable 65 in a tensioned state with the fixtures 63 and 64 to introduce prestress to the lower flange 60b has been mainstream. The effectiveness of this type of construction method is, for example, “reinforcement of existing steel plate girder bridge by introducing prestress”.
(Bridges and foundations, Vol 30, No. 3, March 1996 issue; published by Construction Co., Ltd.).
There is no essential difference between "pre-stress" and "post-tension" in terms of the same phenomenon seen from the side of the girder to be reinforced or the reinforcing material, so this type of reinforcement method is called "post-tension reinforcement method". ".

The external post tension reinforcement method using cable strands is also applied to the tensile members of truss girders, and the present inventor (Hironori Namiki) "reinforces the aged pin truss with the post tension method". (Bridges and foundations, Vol 28, No. 4, April 1994 issue; issued by Construction Books Co., Ltd.). In the construction method described in this document, the strand is installed in a straight or bent fan shape along the lower chord member and diagonal member that receives a tensile load from the center of the bridge, and a tensile force is introduced into the strand using a hydraulic jack. The lower chord material is post-tension reinforced.

[0006]

However, the above-mentioned external post tension reinforcement method has the following problems (1) and (2). (1) Cables and PC steel rods are used as the above-mentioned reinforcements, but since these reinforcements generally have high tensile strength but low rigidity, they do not contribute to the increase of the rigidity of the bridge girders, and therefore, they cannot be increased. (2) In addition, pipes are often installed on bridges. However, in the method using the above-mentioned reinforcing material, the installation space for installing cables and fixing devices is There is a problem that the space under the girder is narrowed due to the sacrifice or the reinforcement material is attached to the lower part of the bridge.

In view of these problems, the present invention intends to solve the problem by introducing a prestress into a constituent member of a bridge by a method different from the conventional post-tensioning method to increase the rigidity of the bridge and improve the fatigue strength. At the same time, the point is to provide a bridge reinforcement method that does not sacrifice the mounting space or the space under the girder.

[0008]

In order to solve the above problems, the present inventors have paid attention to the thermal expansion characteristics of the reinforcing plate. BACKGROUND ART Conventionally, there is a method called "shrink fitting" that is a method that utilizes the characteristic that a steel material is thermally expanded and then cooled and contracted. This method is, for example, when inserting the axle of a train into the fitting hole of the wheel and joining the two, after inserting the axle into the fitting hole that has been expanded by heating and expanded in advance, then cool to room temperature and fit. It is used when the diameter of the joint hole is reduced and the axle and the wheel are firmly connected.
The present inventors have arrived at the present invention as a result of applying the same principle to a bridge reinforcing method and promoting intensive research.

That is, in the method for reinforcing a bridge of the present invention, a post tension reinforcing plate is disposed on the surface of a girder to be reinforced on a bridge, and a temperature is maintained between the girder to be reinforced and the post tension reinforcing plate by heating or cooling operation. After the post tension reinforcing plate is fixed to the reinforced girder in a state in which the post tension reinforcing plate is relatively extended in the girder direction with respect to the reinforced girder, the reinforced girder and the post tension reinforcing plate are provided. The feature is that the post-tension reinforcing plate contracts in the girder direction in the process of reaching the service temperature to reinforce the girder to be post-tensioned. As a result, after the post tension reinforcing plate, which has been stretched by a predetermined amount relative to the reinforcing girder, is fixed to the reinforcing girder, tensile stress acts on the post tension reinforcing plate while the service temperature is reached, and Since the compressive residual stress acts on the girder, the girder to be reinforced is post-tensioned and stiffened.

The relative extension of the post tension reinforcing plate in the girder direction means that the post tension reinforcing plate and the reinforced girder have the same coefficient of thermal expansion and are positive. This is achieved by heating to a high temperature, which is a typical method when steel materials are used for both. On the other hand, when the coefficients of thermal expansion of both are the same and negative, it can be achieved by making the post tension reinforcing plate a temperature relatively lower than that of the girder to be reinforced. When reinforcing a steel or concrete reinforced girder with a post tension reinforcing plate made of a material having a different coefficient of thermal expansion from the reinforced girder such as a fiber material or a fiber reinforced resin material, the operation may be slightly different. is there. That is, in order to make it easier to extend the post tension reinforcing plate relative to the reinforced beam, if the reinforced beam of the reinforced beam is smaller than the coefficient of thermal expansion of the post tension reinforcing plate, use both of them. It is effective to set the temperature higher than the temperature or the post tension reinforcing plate to a temperature higher than the girder to be reinforced, and in the opposite case, both of them should be lower than the service temperature or post tension reinforcing. It is effective to bring the plate to a temperature lower than that of the girder to be reinforced.

Further, from the viewpoint of easily controlling the relative displacement amount of the post tension reinforcing plate with respect to the reinforcement girder, first, one end of the post tension reinforcing plate is fixed to the reinforcement girder and the other end thereof is fixed. After it is attached so that it can be expanded and contracted in the girder row direction, the post tension reinforcing plate is heated to a temperature higher than the girder to be reinforced and expanded, and then the other end of the post tension reinforcing plate is fixed to the girder to be reinforced. After that, it is preferable to cool the post tension reinforcing plate.

In the case of a general steel girder, the stresses introduced into the post tension reinforcing plate and the reinforced girder by post tension reinforcement are σ _p and σ _f , respectively, and the length of the reinforced section is L and the reinforced girder is reinforced. _Let ΔL be the relative displacement of the post tension reinforcing plate with respect to the girder in the column row direction and E _f and E _p be the elastic coefficients of the girder to be reinforced and the post tension reinforcing plate, respectively, and ΔL = L (σ _p / E _p −σ _f / It is preferable to heat the post tension reinforcing plate so as to satisfy the relational expression of E _f ).

Further, it is desirable that the heating range is set to be a range excluding the fixing portion between the post tension reinforcing plate and the girder to be reinforced. This is because when the fixed portion of the post tension reinforcing plate is fixed to the reinforced girder in a state of being heated and expanded, residual stress in the plate width direction is generated in the fixed portion after cooling,
This is to prevent it.

After heating the post tension reinforcing plate,
It is desirable that the fixing to the girder to be reinforced during the cooling process is performed from the end of the post tension reinforcing plate and gradually toward the center. The post tension load is introduced along with the cooling of the post tension reinforcing plate, so if the post tension reinforcing plate is gradually fixed toward the center from the end of the post tension reinforcing plate in line with the increase in post tension load, the load distribution inside the joint will be shared. It is effective because it becomes constant.

When the reinforcing girder is a curved girder, it is desirable that the lower surface of the curved girder be divided into a plurality of regions in the girder direction, and post tension be introduced into the curved girder for each region. When post tension is introduced by heating the post tension reinforcing plate in all areas at once, it is very difficult to control the thermal expansion displacement of the post tension reinforcing plate in the direction perpendicular to the girder direction, but the reinforcing area is divided into multiple sections. By dividing into areas, the control becomes easy.

After the post tension is introduced as described above, it is desirable that the post tension reinforcing plate and the girder to be reinforced be bonded to be integrated. As a result, not only the fixed portion of the post tension reinforcing plate described above but also the shearing force is reliably transmitted from the post tension reinforcing plate to the reinforced girder over the entire length of the reinforcing plate, and both are integrated with the live load in the reinforced section. It is possible to secure the reinforcing effect of responding by becoming.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Various embodiments of the present invention will be described below. FIG. 1 is a schematic side view of a reinforced girder for explaining a method for reinforcing a bridge according to the present invention, FIG. 2 is a bottom view of the reinforced girder shown in FIG. 1, and FIG. FIG. In each of these figures, reference numeral 1 is a reinforced girder having an I-shaped cross section (H-shaped steel), 1a is an upper flange of the reinforced girder 1, 1b is a lower flange, 1c is a web (abdominal plate), 2
Indicates a post tension reinforcing plate. Here, the lower flange 1b corresponds to the reinforced flange to which the tensile force acts.

The basic steps of this embodiment are as follows.
First, the post tension reinforcing plate 2 is arranged on the lower surface of the lower flange 1b of the H-shaped steel 1 to be reinforced, and one end 2a of this post tension reinforcing plate 2 is fixed to the lower flange 1b, and the other end is fixed. The portion 2b is attached to the lower flange 1b in a state in which it can be expanded and contracted in the girder direction. Then, the lower surface (heating range S) of the post-tension reinforcing plate 2 is heated to expand the reinforcing plate 2 and extend a predetermined amount in the column direction with respect to the lower flange 1b. Next, in this state, the other end 2b of the reinforcing plate 2 is fixed to the lower flange 1b. Then, the post tension reinforcing plate 2 is cooled and contracted in the column direction, and a compressive stress is applied to the lower flange 1b. In the present embodiment, the post-tension reinforcing plate 2 is attached to the lower flange 1b and then heated and expanded. However, the present invention is not limited to this. I do not care.

The above steps will be described in more detail below.

As shown in FIGS. 1 and 2, a post tension reinforcing plate 2 is arranged on the bottom surface of a lower flange 1b of a girder 1 to be reinforced along the girder row direction, and one end portion 2a of the post tension reinforcing plate 2 is arranged. Are joined to the lower flange 1b with high-strength bolts 3A, 3A, ... And nuts 3B, 3B ,. The other end 2b of the post-tension reinforcing plate 2 is attached to the lower flange 1b using temporary holders 4, 4, 4, 4 so that it can be expanded and contracted in the girder direction without being bolted. Specifically, as shown in FIG. 4, the temporary receiver 4 includes a tightening portion 4a that presses the upper surface of the lower flange 1b and a roller 4b that supports the lower surface of the reinforcing plate 2. is there. The temporary receiving tools are not limited to the positions described above, and are arranged at appropriate intervals so that the reinforcing plate 2 does not hang down and an error does not occur in the measurement of the relative displacement amount. Further, in the present embodiment, high-strength bolts and nuts are used as means for fixing the one end portion 2a of the reinforcing plate 2 to the lower flange 1b, but instead of this, arc welding or an adhesive such as epoxy resin is used for joining. You may.

As the post-tension reinforcing plate 2, one having a cross-sectional shape, rigidity, and thermal expansion / contraction characteristics corresponding to the shape of the girder to be reinforced and the desired post tension load is appropriately selected and used. Specifically, a steel material is preferable from the viewpoint of easy availability, and among them, an alloy containing iron or carbon, for example, a high-strength steel having a tensile strength of about 490 N / mm ² or more, a tensile strength of about 588 N / mm ² or more. Heat-treated steel or a steel material having a higher tensile strength, which is rarely used for bridges due to its low weldability, and a weather-resistant steel material having a metal element such as copper or chromium suspended therein are suitable. Further, as a material having a different coefficient of thermal expansion from the steel material, high-strength carbon fiber,
It is also effective to use a sheet-shaped or plate-shaped molding material in which an aramid fiber or the like is carried by a resin.

Next, the dial gauge 5 is attached to the lower flange 1.
b, and the tip of the gauge head 5a of the dial gauge 5 is brought into contact with the end surface 6a of the contact member 6 joined to the lower surface of the other end 2b of the reinforcing plate 2 to provide a post tension reinforcing plate for the lower flange 1b. 2. Make it possible to always observe the relative displacement in the column direction. Strictly speaking, the relative displacement amount measuring point is preferably set at the end of the reinforcing range, but if it is near the end of the reinforcing range, a large error does not occur in the measured value.

Then, as shown in FIGS. 1 and 2, the area S of the lower surface of the reinforcing plate 2 is heated to cause a temperature difference between the post tension reinforcing plate 2 and the lower flange 1b, and the dial gauge 5 While observing the value, heating is continued until the relative displacement amount of the reinforcing plate 2 in the column direction with respect to the lower flange 1b reaches a predetermined planned value. At this time, the heating range S
Is preferably set in a range in which it is difficult to transfer heat to the fixed portions (portions to be bolted) of both ends 2a and 2b of the post tension reinforcing plate 2. This is the post tension reinforcement plate 2
This is because if the fixing part of (1) is fixed to the lower flange 1b in a state of being heated and expanded, residual stress in the direction perpendicular to the girder (plate width) direction is generated during cooling. It is also effective to arrange a container containing cooling water or a sponge containing cooling water at the end of the heating range S to prevent heat transfer to the fixed portion.

As a heating means for the post tension reinforcing plate 2, a method of directly or indirectly applying a gas combustion flame to the steel plate is convenient, but as other heating means, a chemical reaction heat using an electric heater, a thermite, or the like, Heat radiator,
A high frequency heater can be used.

Next, as shown in FIG. 2, high-strength bolts are inserted into the bolt holes 2c, ..., 2c of the other end portion 2b of the post tension reinforcing plate 2 which has undergone a predetermined relative displacement, and the other end portion 2 is inserted.
B is bolted to the lower flange 1b. After that, the post-tension reinforcing plate 2 contracts in the process of cooling, and when the temperature difference with the lower flange 1b disappears, a predetermined compressive stress is applied to the relevant reinforcing range of the lower flange 1b, and the post-tension introduction is completed.

The relationship between the heating temperature of the post tension reinforcing plate and the post tension load to be introduced is as follows.

Now, when the cross-sectional area of the reinforcing plate is A _p and the post tension load introduced into the reinforcing plate is N _p , the stress level σ _p of the reinforcing plate at the time of introduction is expressed in the form of the following equation (1). To be done.

Σ _p = N _p / A _p (1)

In the above formula (1), A _p is the cross-sectional area of the reinforcing plate. The stress σ _f acting on the outermost edge of the reinforced girder of the reinforced girder is the compressive stress σ _c due to the post tension load N _p and the eccentric bending moment generated because the load N _p acts eccentrically on the bridge girder. It is expressed by the sum of bending stress σ _bc due to M _p , that is, the following expression (2).

Σ _f = σ _c + σ _bc = −N _p / A _s −M _p y _f / I _s (2)

In the above formula (2), A _s : cross-sectional area of the reinforced girder,
M _p: bending moment acting on the reinforcing spar, I _s: the reinforcement girder second moment, y _f: a distance from the neutral axis of the reinforcing digits to the reinforcing flange outermost.

The bending moment M _p acting on the reinforced girder is expressed by the following equation (3).

M _p = N _p (y _f + t _p / 2) (3)

In the above equation (3), t _p is the plate thickness of the reinforcing plate.

The relative strain amount ε of the reinforcing plate with respect to the outermost edge of the flange to be reinforced is expressed by the following equation (4-1) when the elastic coefficients of the reinforcing plate and the girder to be reinforced are E _p and E _f , respectively.

Ε = (σ _p / E _p −σ _f / E _f ) (4-1)

In this embodiment, since both the reinforcing plate and the reinforced girder are made of steel, the elastic coefficients E of the reinforcing plate and the reinforced girder are substantially equal, and the above equation (4-1) is transformed as follows. .

Ε = (σ _p −σ _f ) / E = Δσ / E (4-2)

The relative temperature difference ΔT required to generate such a relative strain amount ε is obtained by the following equation under the condition that the temperature of the reinforcing plate is kept constant while the temperature of the reinforcing plate is constant. It is expressed by (5).

[0040]     ΔT = εL / α (α: linear expansion coefficient of the reinforcing plate) (5)

On the other hand, the required relative displacement amount ΔL can be expressed by the following equation (6).

ΔL = εL (6)

Therefore, after heating the reinforcing plate to a temperature higher than the flange to be reinforced by ΔT shown in the above formula (5) or until the relative displacement amount shown in the above formula (6) reaches ΔL, If you attach it to the reinforced flange and fix it,
When the temperature difference between the reinforcing plate and the girder to be reinforced disappears, the above post tension load is introduced. In fact, it is practical to heat only the reinforcing plate to a temperature higher by ΔT so that the relative displacement amount due to thermal expansion becomes ΔL. Strictly speaking, since the linear expansion coefficient α is a function of temperature, the above expression is an approximate expression, but since the error is slight, there is no practical problem.

Now, H-section steel (H400 × 200 × 8 × 1
3) is a reinforced girder, and this H-shaped steel has a length L (= 186c).
m) relative displacement amount ΔL and relative heating temperature Δ when post tension reinforcement is performed using the reinforcing plate (208 × 13)
The results of calculating T and the stress level to be introduced are shown in Table 1 below.

[0045]

[Table 1]

The values in the table are obtained by using the above equations (1) to (6), and the cross-sectional area A _p of the reinforcing plate A _p = 27.04 cm ² ;
_s = 83.37 cm ² ; second moment of area of reinforced girder I _s = 23,5
00cm ⁴ ; Distance from the neutral axis of the reinforced girder to the outermost edge of the reinforced flange y _f = 20 cm; Elastic modulus of steel E = 2,100,000 × 9.80
6 N / cm ² ; calculated as the linear expansion coefficient of steel material α = 11.6 × 10 ⁻⁶ / ° C.

Posts that are normally introduced into the reinforced flange
Tension stress is -100N / mm ²Thought to be
Therefore, in the case of the digits of this calculation example, from Table 1 above
By heating the reinforcing plate to about 100 ° C, the desired post
It can be seen that the tension stress can be easily obtained. actually,
It is difficult to heat the entire reinforcing plate evenly, and partial heating
In addition, heat transfer causes some heat to the reinforced girder.
Therefore, it is necessary to heat the reinforced girder to a temperature higher than the above temperature.
There is a point. Still, generally, the transformation point at which the steel material changes
And post-tensioning without heating to recrystallization temperature
It can be estimated from the table above that the
The post tension reinforcement method related to Ming is a practical method.
Be understood.

By the way, the above post tension reinforcing plate 2
As the high-strength bolt used for fixing the to the reinforcing girder 1, it is common to use a high-strength hexagonal bolt or a torcia type high-strength bolt suitable for friction welding. The nominal size of the screw is preferably M16, M20, M22, M24,
The grades are F8T and F10T for high strength hexagon bolts.
In the case of the torcia type high strength bolt, those of S10T are suitable. For tightening the bolts, use a torque wrench,
An electric or hydraulic tightening machine may be used, or an electric impact wrench may be used for primary tightening.

After the post tension load is introduced into the reinforced girder 1, the reinforced girder 1 and the post tension reinforcing plate 2 may be bonded and fixed using an adhesive such as an epoxy resin. That is, after the post tension reinforcement, the adhesive is injected into the boundary surface between the post tension reinforcement plate 2 and the lower flange 1b. When it is considered that the degree of fixation between the reinforcing plate 2 and the lower flange 1b is insufficient, both can be fixed by crimping them together using a spring clip or the like. If there is a camber on the bridge girder and the gap between the reinforcing plate and the reinforced flange is large, insert a packing made of steel material or inject an inexpensive material such as mortar to measure the shear force transmission. However, if both are integrated, a material that can secure the shear strength between the reinforcing plate and the reinforced flange must be used. By such adhesive fixing, the shearing force is surely transmitted from the post tension reinforcing plate 2 to the lower flange 1b, and the reinforcing effect against the live load can be secured.

Normally, the reinforcement range is wider than the range where reinforcement is required, so there is no problem even if the same post tension load is not introduced up to the end of the fixed portion of the reinforcement plate.
If the joint of this fixed portion becomes long, a large difference will occur in the load received by the bolts constituting the joint. In order to reduce the difference in the load received by each bolt, it is preferable to fix the joint as the reinforcing plate cools and the post tension load increases, and specifically, at the end of the post tension reinforcing plate. It is preferable to fix the part from the closer part and gradually fix the part closer to the center according to the magnitude of the post tension load introduced with cooling. This makes it possible to suppress the uneven load on the joint.
This also applies to the fixed part joint at one end of the post tension reinforcing plate that is fixed to the girder to be reinforced before heating.Only the outermost end is fixed in advance, and the reinforcing plate is cooled and the post is cooled. When the tension is gradually fixed in the middle of the process, a fixed portion in which uniform post tension is introduced can be formed. It should be noted that when fixing by high-strength bolts by friction welding, it is expected that the joint will slip slightly and the load will be even, so it is unlikely that uneven load on the fixed joint will be a problem. However, in the case of welding fixation, it is considered desirable to fix the load in the joint at both ends to be constant.

Further, the time required to fix the reinforcing plate to the reinforced girder depends on the size of the reinforced girder, the reinforced range, etc., and in particular in the case of a large structure such as a bridge, a considerable time is required. . In order to accurately introduce a predetermined post tension load, it is necessary to fix the post tension reinforcing plate 2 to the lower flange 1b while keeping the relative displacement of the post tension reinforcing plate 2 constant. The relative displacement of the post tension reinforcing plate 2 is determined by the relative thermal displacement amount, and by the temperature distribution of the reinforcing plate and the girder to be reinforced. In this embodiment, when the reinforcing plate 2 is heated, heat is also transferred to the reinforced girder. Therefore, it is desirable to change the heating process of the reinforcing plate 2 in advance and measure the influence of the heat transfer to find and prepare a heating pattern that can keep the relative displacement constant.

When the post tension reinforcing plate 2 is heated and fixed to the reinforcing girder, the post tension reinforcing plate 2 is constrained by high-strength bolts so as not to slip between them.
While cooling and contracting, tensile stress is introduced into the post tension reinforcing plate, and compressive residual stress is introduced into the reinforced girder. This residual stress is introduced by the expansion and contraction of the reinforcing plate between the fixing points fixed with high-strength bolts, so when installing multiple bolts in the direction perpendicular to the bridge axis, heating the fixing part will Residual stress is also introduced in the direction perpendicular to the axis, which is disadvantageous because the load that the high-strength bolt or the like of the fixed portion must transmit increases.

In order to suppress the occurrence of such residual stress in the direction perpendicular to the bridge axis, it is desirable to set the heating range within a range excluding the fixing portion of the post tension reinforcing plate between the reinforcing plate and the reinforced girder.

When the fixing portion is heated, the reinforcing plate and the reinforced flange are subject to biaxial stress. Strength evaluation of a plate subjected to biaxial stress is more complicated than in the case of uniaxial stress, and some strength locally drops. Generally, the strength of a steel material subjected to biaxial stress can be evaluated in the same manner as in the case of uniaxial stress by using equivalent stress. The stress applied to the flange to be reinforced is examined using the equivalent stress of Mises as a representative equivalent stress. Where von Mises equivalent stress σ
_k is expressed by the following equation (7).

[0055]

[Equation 1]

In the above equation (7), σ₁Is the reinforced flange
Maximum response in the column direction received after post tension reinforcement
Force, σ₂Is the stress in the direction perpendicular to the columns and rows and is usually σ₁> 0
is there. When there is no stress in the direction perpendicular to the columns and rows, the equivalent stress is expressed by equation (7).
At σ₂= 0, σ_k= Σ ₁Becomes Digit line right angle direction
Force σ₂Since <0, when there is a stress in the direction perpendicular to the columns and rows,
−σ₁σ₂> 0, so σ in equation (7)_k> Σ₁Tona
The strength of the reinforced flange is when there is no stress in the transverse direction.
It will be lower and the reinforcing effect will be diminished. this thing
To prevent residual stress in the direction perpendicular to the columns from occurring.
It turns out that there is a need to take measures.

In the above embodiment, an example in which a post girder is reinforced with post tension is shown, but the bridge reinforcing method according to the present invention can be applied to a curved girder. 5 and 6 exemplify a curved box girder 10 which is a reinforced girder. FIG. 5 is a schematic cross-sectional view of the post-tension-reinforced curved box girder 10, and FIG. 6 is a bottom view of the curved box girder 10. still,
In each drawing, reference numeral 10a is an upper flange of the curved box girder 10, 10b is a lower flange thereof, 10c is a web (abdominal plate), 11 is a post tension reinforcing plate attached to the bottom surface of the lower flange 10b, 12A is a bolt, 12B. Indicates a nut.

The procedure for reinforcing the illustrated curved box girder 10 using the curved post tension reinforcing plate 11 is substantially the same as the above-described linear girder reinforcement procedure. The lower flange 10b of the curved box girder 10 is curved along a curve having a predetermined curvature in the girder row direction. In the present embodiment, first, a curve that defines the curvature of the curved box girder 10 is approximated by polygonal lines 13a, 13b, and 13c along the column row direction, and the bent portion of these polygonal lines is joined to the curved box girder 10 by the reinforcing plate 11. Post tension is introduced into the area defined by each fixing portion as the fixing portion. The range where the lower surface of the reinforcing plate 11 is heated is set within the heating range S1, S2, S3 in which it is difficult to transfer heat to the fixing portion that joins the reinforcing plate 11 to the lower flange 10b with the bolts 12A, ... And the nuts 12B ,. To be done.

Further, as shown in FIG. 7, since the heating range S has a fan shape having a large radius of curvature, when the heating range S is heated and expanded, a region close to the inner circumference (see the figure). It is necessary to make a relative displacement in a region closer to the outer periphery (upper part in the figure) than in a lower part. That is, when the lateral width of the outer circumference of the heating range S shown in FIG. 7 is L ₁ , the lateral width of the inner circumference is L ₂ , and the displacement amounts of the inner circumference and the outer circumference are ΔL ₁ and ΔL ₂ , respectively, ΔL ₁
/ L ₁ = ΔL ₂ / L ₂ = heating range S so as to satisfy constant
When heated and expanded, it is possible to obtain a substantially uniform reinforcing effect in the direction perpendicular to the girders. In practice, it is desirable to calculate the displacement distribution with respect to the heating distribution in advance in order to heat and expand the heating range in this way, and obtain the heating method in advance. Especially in the case of wide and long bridges, it is necessary to consider the force in the direction perpendicular to the bridge axis when post-tensioning a curved bridge, so perform a mechanical analysis of the main girder.
It is important to find in advance a heating pattern that can generate thermal deformation corresponding to the optimum reinforcing pattern.

The reinforcing range of the girder to be reinforced may be divided into a plurality of reinforcing regions in the direction perpendicular to the girder row, and post tension reinforcement may be performed for each reinforcing region. This reinforcing method is effective for reinforcing wide reinforced girders such as box girders. That is, since each reinforcing region is small, it is easy to adjust the heating temperature of each reinforcing region. Also, since a plurality of post tension reinforcing plates are used, the weight of each reinforcing plate can be small, so construction can be performed. It becomes very simple. Furthermore, the eccentric load applied to the reinforced girder can be easily reduced by adjusting the post tension load in each reinforcing region.

Specifically, as shown in FIG. 8A, the lower surface of the reinforced flange 20 is divided into two regions 21A and 21B in the direction perpendicular to the columns and rows, and the post tension reinforcing plate is provided in each region. 22A and 22B are attached to each other, and post tension is applied to the reinforced flange 20 by the above reinforcing method. Alternatively, as illustrated in FIG. 3B, the lower surface of the reinforced flange 24 has a plurality of strip-shaped regions 25A, 25B, ...
It is also possible to apply the above reinforcing method by abutting the post tension reinforcing plates 26A, ...

Next, an experimental example of the above-mentioned bridge reinforcing method according to the present invention will be described in detail.

(Experimental Method) As shown in FIG. 9, a main girder 30 of a bridge girder was prepared as a reinforced girder. 9A is a side view of the main girder 30 reinforced by the post tension reinforcing plate 34, and FIG. 9B is a sectional view of the main girder 30 taken along the line AA.
A strain gauge is attached at the cross-sectional position of FIG. Further, the main girder 30 is an H-shaped steel (H400 × 200) having a total length of 3 m.
× 8 × 13), and the lower surfaces of both ends in the column-row direction are simply supported. The conditions of the calculation example listed in Table 1 above are the same as those of this experimental example.

The post tension reinforcing plate 34 has a length of 1.
It is a strip plate (width: 208 mm x thickness: 13 mm) of 3 m, and its axial end portions are respectively provided with four bolts 35A, 35.
A, ... and nuts 35B, 35B, ..
It is fixed to the central part of the lower surface of 0b.

In the experiment, when the one end portion 34a of the post tension reinforcing plate 34 is fixed with bolts, the heating range S4 is heated by the gas burner, and when the reinforcing plate 34 thermally expands to reach a predetermined relative displacement, The end portion 34b was also bolted to the main girder 30 and then naturally cooled, during which the stress and temperature of the reinforcing plate 34 and the main girder 30 were measured.

The stress of the post tension reinforcing plate 34 (reinforcement plate stress) and the stress of the reinforced flange (inner surface stress of the reinforced flange) were measured by attaching an electric resistance wire strain gauge. As shown in FIG. 9A, the measurement position is set at a position away from the heating range while avoiding the influence of the end, and near the quadrant (fixed position AA) between the fixed points at both ends of the reinforcing plate 34. did. The stress of the post tension reinforcing plate 34 is as shown in FIG.
40m from the end of the reinforcing plate to the web side as shown in (b)
The average value by the strain gauges 36A, 36B attached at two places where m is entered, and the stress of the reinforced flange is represented by the average value by the strain gauges 37A, 37B attached at two places at 40 mm from the lower flange end to the web side.

The temperature of the reinforcing plate 34 is the same as that of the strain gauge 36.
The tip of the thermocouple temperature-measuring sensor was attached to a place within 3 mm from the attaching position of A and 36B with a heat-resistant tape for measurement. In addition, in order to prevent the strain gauge from being damaged by heat, the end of the heating range was covered with a moistened mat to carry out the experiment, so that the temperature change during the experiment was suppressed within 5 ° C.

(Experimental Results) In this experimental example, the heating range S4 of the reinforcing plate was heated substantially evenly by the gas burner, and the value of the dial gauge (not shown) attached to the end of the post tension reinforcing plate was observed. While the relative displacement amount (ΔL) due to thermal expansion was maintained at 0.5 mm, the bolts were fully tightened and fixed.
Table 2 shows the experimental results of measuring the stress during the cooling process of the reinforcing plate. It takes about 30 seconds from the start of the bolt tightening work to the completion of the bolt tightening work, that is, the measurement start time of 0 seconds.
During this time, heating was performed gently to maintain the relative displacement amount constant.
In addition, the stress measurement value includes self-temperature compensation of 11 × 10 ⁻⁶ / ° C.
The strain gauge is used and the value at the time of complete release is set to zero, and the drift amount of the measuring instrument is zero-corrected.

[0069]

[Table 2]

During the measurement, the room temperature decreased by 2 ° C., so the member also shrunk slightly, but for the stress measurement, self-temperature compensation 11 × 10 ^-6
Since a strain gauge of / ° C was used, it is considered that room temperature change is not relevant.

(Consideration) Table 3 below shows a comparison result between the calculated value in Table 1 and the magnitude of the post-tension stress actually introduced.

[0072]

[Table 3]

Here, the distance from the neutral shaft of the H-shaped steel to the strain gauge attachment position of the reinforced flange is y = 200 m.
From m−13 mm = 187 mm, the calculated stress σ _{H at} the strain gauge attachment position of the reinforced flange was calculated using the following equation (7).

Σ _H = σ _f y / y _f (7)

From Table 3, it is considered that the error between the measured value and the calculated value is within the practically acceptable range, and the effectiveness of the post tension reinforcing method according to the present invention was confirmed.

[0076]

As described above, according to the bridge reinforcing method of the present invention, the post tension reinforcing plate is provided on the surface of the bridge-supported girder, and the reinforcement girder and the post tension are heated or cooled. A temperature difference is provided between the post tension reinforcing plate and the reinforcing plate, and the post tension reinforcing plate is stretched relatively to the beam to be reinforced in the girder row direction. The post tension reinforcement plate shrinks in the direction of the girder in the process of reaching the service temperature of the reinforcement girder and the post tension reinforcement plate. Moreover, it becomes possible to increase the rigidity of the bridge and improve the fatigue strength. In addition, this reinforcing method has an advantage that the suspension space such as piping and the space under the girder are not sacrificed.

When the relative displacement amount of the post tension reinforcing plate in the girder row direction with respect to the girder to be reinforced is ΔL, ΔL
= L (σ _p / E _p −σ _f / E _f ) By heating the post tension reinforcing plate so as to satisfy the relational expression, the post tension load can be applied with high accuracy and efficiency. .

[Brief description of drawings]

FIG. 1 is a schematic side view of a reinforced girder for explaining a bridge reinforcing method according to the present invention.

FIG. 2 is a bottom view of the reinforced girder shown in FIG.

FIG. 3 is a cross-sectional view of the reinforced girder shown in FIG.

FIG. 4 is a schematic view showing a state in which a post tension reinforcing plate is attached to a lower flange by a temporary receiver.

FIG. 5 is a schematic side view of a post tension reinforced curved box girder.

FIG. 6 is a bottom view of the curved box girder shown in FIG.

FIG. 7 is a schematic diagram showing a fan-shaped heating range S of curved beams.

8A is a schematic view showing a state in which the lower surface of the reinforced flange is divided into two regions, and each region is post-tension reinforced, and FIG. It is a schematic diagram showing a state where each area is divided and each area is post-tension reinforced.

FIG. 9 (a) is a schematic side view showing a main girder having a post tension reinforcing plate fixed to an upper flange, and FIG.
[Fig. 4] is a schematic view showing an AA cross section of the main girder at a position where the strain gauge is attached.

FIG. 10 is a schematic side view showing a bridge girder deformed into an arch by a load.

FIG. 11 is a schematic side view showing a bridge post-reinforced by a conventional external post-tension method.

[Explanation of symbols]

1 Reinforced Girder (H-Shaped Steel) 1a Upper Flange 1b Lower Flange 1c Web (Abdominal Plate) 2 Post Tension Reinforcement Plate 2a One End 2b of Post Tension Reinforcement Plate 2c Other End 2c of Post Tension Reinforcement Plate Bolt Hole 3A High Strength Bolt 3B Nut 4 Temporary holder 4a Tightening part 4b Roller 5 Dial gauge 5a Dial gauge gauge 6 Contact member 6a End face of contact member 10 Curved girder 10a Upper flange 10b Lower flange 10c Web (abdominal plate) 11 Post tension reinforcement Plate 12A Bolt 12B Nut 13a, 13b, 13c Broken line 20 Reinforced flange 21A, 21B Divided area 22A, 22B Post tension reinforcing plate 23, 27 Bolt 24 Reinforced flange 25A-25F Divided area 26A-26F Post tension reinforcing plate 30 Main girder 30a Upper flange 30b Lower Flange 30c Web 34 Post tension reinforcing plate 34a Post tension reinforcing plate one end 34b Post tension reinforcing plate other end 35A Bolt 35B Nut 36A, 36B, 37A, 37B Electric resistance wire strain gauge 50 Bridge girder 50a Upper flange 50b Lower flange 50c Web (abdominal plate) 51 Compressive stress 52 Tensile stress 60 Bridge girder 60a Upper flange 60b Lower flange 60c Web (abdominal plate) 61, 62 Fixing device 63, 64 Fixture 65 External cable

Claims (7)

(57) [Claims] 1. A post tension reinforcing plate is provided on the surface of a girder to be reinforced on a bridge, and a temperature difference is provided between the girder to be reinforced and the post tension reinforcing plate by a heating operation. After the post tension reinforcing plate is gradually extended toward the center from the end of the post tension reinforcing plate in the cooling process in a state where the post tension reinforcing plate is relatively extended in the girder direction with respect to the reinforcing girder, A method for reinforcing a bridge, characterized in that the post-tension reinforcing plate contracts in the girder direction during the process in which the reinforcing girder and the post-tension reinforcing plate reach the service temperature, thereby post-tensioning the reinforced girder. 2. After the post tension is introduced, the post
Of the reinforcement reinforcement plate and the reinforcement girder
The method for reinforcing a bridge according to Item 1 . 3. The post tension reinforcing plate has a temperature higher than that of the girder to be reinforced after one end of the post tension reinforcing plate is fixed to the girder to be reinforced and the other end of the post tension reinforcing plate is extensible in a girder direction. The bridge reinforcing method according to claim 1, wherein the post tension reinforcing plate is cooled by heating the post tension reinforcing plate to expand it, fixing the other end of the post tension reinforcing plate to the girder to be reinforced, and cooling the post tension reinforcing plate. 4. The stress introduced into the post-tension reinforcing plate and the girder to be reinforced by post-tension reinforcement is σ _p and σ _f , respectively, the length of the reinforced section is L, and the stress of the post-tension reinforcing plate to the girder to be reinforced is L. _Let ΔL be the relative displacement in the column and row directions and E _f and E _p be the elastic coefficients of the girder to be reinforced and the post tension reinforcing plate, respectively.
The method for reinforcing a bridge according to claim 1, wherein the post tension reinforcing plate is heated so as to satisfy the relational expression of L (σ _p / E _p −σ _f / E _f ). 5. The method for reinforcing a bridge according to claim 1, wherein the heating range is set within a range excluding a fixed portion between the post tension reinforcing plate and the girder to be reinforced. 6. The reinforcing girder is composed of a curved girder, the lower surface of the curved girder is divided into a plurality of regions in the girder direction, and post tension is introduced into the curved girder for each region.
The method for reinforcing a bridge according to any one of 5 above. 7. The heating operation for the post-tension reinforcing plate applies a gas combustion flame directly or indirectly to the steel plate,
Alternatively, the bridge reinforcing method according to any one of claims 1 to 6, wherein heating is performed using an electric heater, heat of chemical reaction using a thermite, a heat radiator, and a high-frequency heater.