JP2020147970A - Protection facility - Google Patents

Abstract

To provide a protection facility capable of more efficiently absorbing collision energy than conventional ones.SOLUTION: A protection facility comprises a steel beam 14 with which a vehicle having a height exceeding passage limit from a presumed collision direction is presumed to collide. The steel beam 14 has a steel pipe 141. The internal part of the steel pipe 141 is divided into an upstream space and a downstream space in the presumed collision direction, and the downstream space is filled with a reinforcement material 143. The reinforcement material 143 is concrete.SELECTED DRAWING: Figure 2

Description

The present invention relates to a protective work provided with a steel beam that is expected to collide with a vehicle exceeding the traffic limit height from a predetermined collision assumed direction.

There is a bridge girder protector as a facility for protecting the bridge girder from a collision of a vehicle exceeding the traffic limit height (see, for example, Patent Document 1). The bridge girder protector is equipped with a steel beam (protection girder), which is a part where a vehicle is expected to collide. The steel beam is fixed by straddling a hollow steel pipe between the columns. When a vehicle collides, local buckling first occurs at the collision point, and then the entire steel beam bends with the fixed part with the support as a fulcrum while the local buckling progresses, and the collision occurs while increasing the amount of deformation. Absorb energy.

JP-A-2007-205046

In recent years, due to changes in vehicles and road conditions, the weight and speed of vehicles colliding with the bridge girder protector have increased more than before, and it is desired to strengthen the bridge girder protector. However, since there are various restrictions on the installation of bridge girder protectors, there is a desire to avoid strengthening that requires an increase in the dimensions of steel beams, columns, and foundations.

Focusing again on the mechanism by which the bridge girder protector absorbs impact energy, local buckling occurs at the location where the vehicle collided, and while local buckling progresses, the entire steel beam uses the fixed part with the support as a fulcrum. It bends and absorbs collision energy while increasing its deformation.

When local buckling progresses, it leads to a decrease in yield strength and destruction of the cross section. Therefore, in the conventional bridge girder protection work using a hollow steel pipe as a steel beam, even if there is a margin in the amount of bending deformation that can be tolerated for the steel beam as a whole, local buckling will lead to a decrease in strength and cross-sectional destruction. It is considered that the energy absorption actually available is lower than the energy that can be originally absorbed by the entire beam. Such an event is more remarkable in the case where the crane vehicle receives a collision such as the tip of the crane hitting the steel beam at a point than in the case where the truck receives a collision such that the front surface of the loading platform hits the steel beam. Even in the latter case, a bridge girder protector that functions sufficiently effectively and can absorb collision energy more efficiently than before is desired.

These problems and requests are not limited to bridge girder protection work, but also protect the passage of vehicles that exceed the traffic limit height, such as overhead wire protection work (more specifically, collision with the object to be protected due to the passage of the vehicle). This is common to protectors.

An object to be solved by the present invention is to provide a technique for realizing a protective work capable of absorbing collision energy more efficiently than before.

The first invention for solving the above-mentioned problems is a protective work provided with a steel beam that is expected to collide with a vehicle exceeding a traffic limit height from a predetermined collision assumed direction. It is a steel pipe, and the inside of the steel pipe is a protective work in which the downstream side divided into the upstream side and the downstream side in the assumed collision direction is filled with a predetermined reinforcing material.

In the protective work of the first invention, a hollow portion is left inside the steel pipe of the steel beam on the upstream side in the assumed collision direction, and the reinforcing material is partially filled on the downstream side in the assumed collision direction. Even if the local buckling of the steel progresses, further progress can be restricted by hitting the upstream part of the reinforcing material. Therefore, since the local buckling leads to a decrease in proof stress and a fracture of the cross section, it is possible to prevent an event in which the energy absorption actually available is lower than the energy that can be originally absorbed by the entire steel beam. That is, the collision energy can be absorbed more efficiently than before.

（ここで、hは前記鋼管の前記衝突想定方向の内法の全長、bは前記鋼管の縦方向の幅、f_syは前記鋼管の鋼の降伏強度、ｔは前記鋼管の板厚、Eは前記鋼管の鋼のヤング係数）
第１の発明の防護工である。 In the second invention, in the internal method of the steel pipe in the assumed collision direction, the length h ₂ on the downstream side is a length satisfying the following mathematical formula.

(Here, h is the total length of the inner method of the steel pipe in the assumed collision direction, b is the vertical width of the steel pipe, f _sy is the yield strength of the steel of the steel pipe, t is the plate thickness of the steel pipe, and E is. Young's modulus of steel in the steel pipe)
It is a protective work of the first invention.

According to the second invention, the development of local buckling can be allowed to near the limit of reaching the yield strength of the steel. Therefore, the bridge girder protection work of the second invention can absorb the collision energy more efficiently than the conventional one.

The third invention is the protective work of the first or second invention in which the reinforcing material is concrete.

According to the third invention, by using concrete as the reinforcing material, the load is effectively distributed over the entire steel pipe of the steel beam while receiving the load of local buckling and preventing the progress of local buckling. It is possible to efficiently absorb collision energy due to bending deformation of the entire steel pipe.

The fourth invention is the protective work of the third invention, in which the upstream side inside the steel pipe is filled with a space filler for forming the concrete casting space on the downstream side.

According to the fourth invention, the concrete placing space can be maintained regardless of the posture of the steel pipe. Therefore, since the steel pipe can be erected and the concrete can be poured at the time of placing the concrete, it is possible to easily create the steel beam and improve the thickness control and accuracy of the reinforcing material.

The perspective external view which shows the structural example of the bridge girder protection work. Longitudinal section of a steel beam. A flowchart for explaining the manufacturing and installation procedure of the bridge girder protection work. A model diagram for explaining the action and effect of the bridge girder protection work. A model diagram for explaining the principle of determining the thickness of the reinforcing material. The vertical sectional view which shows the deformation example of the structure of a steel beam.

Hereinafter, an embodiment of the bridge girder protection work will be described as a protection work provided with a steel beam that is expected to collide with a vehicle exceeding the traffic limit height from a predetermined collision assumed direction, but the forms to which the present invention can be applied are as follows. Of course, it is not limited to the embodiment of.

FIG. 1 is a perspective external view showing a configuration example of the bridge girder protection work 10 of the present embodiment.
The bridge girder protection work 10 is a protection work that prevents a vehicle (moving body) traveling on the road 4 from colliding with the viaduct 6 (protection target structure). The bridge girder protection work 10 is placed between the foundations 11 placed on both sides of the road 4, the columns 12 erected on each of the foundations, and the steel beams 14 straddling the upper part of the road 4. It has a steel beam 14 that is bridged and fixed. The assumed collision direction with the bridge girder protection work 10 is the horizontal direction (thick arrow in FIG. 1) along the road of the road 4.

FIG. 2 is a vertical cross-sectional view of the steel beam 14. The steel beam 14 has a steel pipe 141 and a reinforcing member 143 partially filled inside the steel pipe 141.

The steel pipe 141 is a steel pipe having a substantially rectangular cross section, but a steel pipe having a tubular shape may be used as long as it has a circular cross section or other cross-sectional shape.

The reinforcing member 143 is formed by partially filling the inside of the steel pipe 141 on the downstream side divided into the upstream side and the downstream side in the assumed collision direction by partially filling concrete. In other words, inside the steel pipe 141, a void 145 not filled with concrete is provided on the upstream side divided into the upstream side and the downstream side in the assumed collision direction. The reinforcing material 143 may be realized by other materials.

FIG. 3 is a flowchart for explaining a procedure for manufacturing and installing the bridge girder protection work 10.
In order to create the bridge girder protection work 10, the pipe making process is first executed (step S2). Specifically, an appropriate number of through holes for pouring concrete are provided on the surface of the steel pipe 141 on the side in the assumed collision direction. Next, the edges at both ends of the steel pipe 141 are closed.

Next, the filling step is executed (step S4). Specifically, the steel pipe 141 is laid down with the surface on the assumed collision direction side up, an appropriate amount of concrete is poured through the through hole, and the concrete is waited for hardening. Close the through holes after the concrete has hardened. When concrete flows in from the edge of the steel pipe 141, it is not necessary to provide a through hole.

Next, the support column installation step is executed (step S6). Specifically, the foundation 11 is created and the support columns 12 are erected.

Then, the assembly process is executed to attach and fix the steel beam 14 to the support column 12 (step S8), and the assembly of the bridge girder protection work 10 is completed.

FIG. 4 is a model diagram for explaining the action and effect of the bridge girder protection work 10.
FIG. 4 (1) corresponds to a view of a steel beam 14J made of a hollow steel pipe in a conventional bridge girder protection work in a cross section along an assumed collision direction, and FIG. 4 (2) shows the bridge girder protection work 10 in the present embodiment. It corresponds to a view of the steel beam 14 in a cross section along the assumed collision direction.

As shown in FIG. 4 (1), in the conventional steel beam 14J made of hollow steel pipe, when local buckling occurs at the collision point, the entire inside of the steel pipe 141 of the steel beam 14J is hollow, so that the local seat generated by the collision occurs. The bending progresses without stopping, eventually leading to a decrease in strength and a fracture of the cross section. Then, the effect of transmitting the force from the local buckling portion to the steel pipe 141 is significantly lower than that before the proof stress is lowered or the cross-section is broken. As a result, when looking at the steel beam as a whole, the absorption of collision energy after the local buckling portion reaches a decrease in yield strength or cross-sectional fracture becomes small.

On the other hand, as shown in FIG. 4 (2), the inside of the steel pipe 141 of the steel beam 14 in the present embodiment is provided with the reinforcing material 143 on the downstream side in the assumed collision direction, so that the depth of the dent due to local buckling is deep. The thickness is the thickness of the gap 145 (upstream length h1) excluding the thickness of the reinforcing material 143 (downstream length h2) from the internal thickness of the steel pipe 141 (internal length h). Limited to.

FIG. 5 is a model diagram for explaining the principle of determining the thickness of the reinforcing material 143 (length h2 on the downstream side), and FIG. 5 (1) is a view of the local buckling point from the assumed collision direction. FIG. 5 (2) corresponds to a view seen in a cross section along the assumed collision direction.

As a basic idea, it is considered that the limit state is when the stress generated in the steel material of the steel pipe 141 reaches the yield strength of the steel material due to the "dent" generated in the local buckling.

Specifically, the "dent" due to local buckling is expressed by Equation 1 when expressed by the displacement y at the coordinate x. Here, h ₁ is the dent depth, b is the dent width, and is the vertical width of the steel pipe 141.

Since the curvature φ of the plate is the second derivative of the displacement y, it is expressed by Equation 2.

The curvature φ _{0 at} the apex of the dent is expressed by Equation 3.

The degree of bending stress σ _{0 at the} apex of the dent due to the curvature φ ₀ is expressed by Equation 4. Here, E is the Young's modulus of the steel, ε ₀ is the strain value at the apex of the dent, and t is the plate thickness of the steel pipe 141.

This bending stress degree σ ₀ is generated not only in the axial direction of the member but also in the direction perpendicular to the member. Therefore, from this biaxial stress, the Mises stress _criterion σ _{Mises at the} dent apex can be expressed by Equation 5.

これを展開すると式７となる。

Equation 6 must be satisfied so that the Mises stress _criterion σ _Mises does not exceed the yield strength f _sy of the steel of the steel pipe 141.

When this is expanded, it becomes Equation 7.

From this, in order to prevent the yield of the steel material due to the dent, the dent height h ₁ needs to satisfy the following equation 8.

Therefore, the filling height h ₂ of the reinforcing material 143 may be set based on the following equation 9.

If the steel beam 14 is replaced with the concrete-filled steel pipe as it is from the hollow steel pipe in order to strengthen the bridge girder protection work 10, the effect of restraining the local buckling is high and the yield strength is increased, but the degree of restraint is too high. The amount of bending deformation is expected to be small. The amount of bending deformation of the steel beam 14 becomes smaller than before, and the support column 12 supporting the steel beam 14 is deformed. If the deformation is limited to the steel beam 14, only the steel beam 14 needs to be replaced in the repair work after the collision, but when the support column 12 is deformed, the support column 12 may be replaced or the foundation 11 may also be repaired. Not preferable.

However, as in the present embodiment, the steel beam 14 is used as a partial filler for concrete, and the filling height h ₂ of the reinforcing member 143 is set, so that the dent of the local buckling does not lead to the yield of the steel material. The collision load is transmitted to the steel pipe 141 and the reinforcing member 143 via local buckling. Then, the collision energy after the dent of the local buckling reaches the reinforcing member 143 is continuously and efficiently absorbed by the bending deformation of the whole.

That is, for example, even in a case where a crane vehicle collides the tip of a crane with a steel beam, it is possible to realize a bridge girder protection work 10 that functions sufficiently effectively and can absorb collision energy more efficiently than before.

The embodiment of the present invention is not limited to the above, and can be changed, added, or deleted as appropriate.

For example, as shown in FIG. 6, the upstream side inside the steel pipe 141 may be filled with the space filler 147 for forming the concrete casting space of the reinforcing material 143 on the downstream side.
Specifically, as the space filler 147, molded styrofoam, molded urethane foam, or the like can be used. When this configuration is adopted, it is not necessary to close one of the edges of the steel pipe 141 and provide a through hole for pouring concrete in the pipe making process. Then, in the filling process when this configuration is adopted, the space filling material 147 is inserted from the edge of the steel pipe 141 on the unclosed side and fitted toward the upstream side in the assumed collision direction to form a concrete casting space. To form. Next, concrete is poured into the casting space with the edge of the steel pipe 141 on the unclosed side facing up.

Further, in the above-described embodiment, the example of the bridge girder protection work has been described, but the technology of the above-described embodiment can be applied to other protection work such as overhead wire protection work that protects the passage of vehicles exceeding the traffic limit height. it can.

10 ... Bridge girder protection work 11 ... Foundation 12 ... Strut 14 ... Steel beam 141 ... Steel pipe 143 ... Reinforcing material 145 ... Void 147 ... Space filling material

Claims (4)

It is a protective worker equipped with steel beams that are expected to collide with a vehicle that exceeds the traffic limit height from a predetermined collision direction.
The steel beam is a steel pipe and
The inside of the steel pipe is filled with a predetermined reinforcing material on the downstream side divided into the upstream side and the downstream side in the assumed collision direction.
Protective worker. Of the internal methods of the steel pipe in the assumed collision direction, the length h ₂ on the downstream side is a length that satisfies the following mathematical formula.

(Here, h is the total length of the inner method of the steel pipe in the assumed collision direction, b is the vertical width of the steel pipe, f _sy is the yield strength of the steel of the steel pipe, t is the plate thickness of the steel pipe, and E is. Young's modulus of steel in the steel pipe)
The protective work according to claim 1. The reinforcing material is concrete.
The protective work according to claim 1 or 2. The upstream side inside the steel pipe is filled with a space filler for forming the concrete casting space on the downstream side.
The protective work according to claim 3.

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