JPH02150737A - Bridge model for wind tunnel test - Google Patents

Abstract

PURPOSE:To previously confirm the propriety of a temporary fixing method through a wind tunnel test by respectively coupling rigid rods divided into groups at every girder of a bridge to be simulated with X-shape beams. CONSTITUTION:Fittings 7 respectively having fitting surfaces formed at 45 deg. against the axis of a bridge at upper and lower ends are fixed to both edges of rigid rods 5 cut into pieces at every model block and plate spring materials 6a and 6b are fitted between the pair of fittings 7a and 7b to be connected with each other in the form of an X. The plate spring 6a is composed of two plate springs inclined leftward and the spring 6b is a plate spring having a wide with (twice as wide as that of the spring 6a) inclined rightward as shown in the figure. The springs 6a and 6b are respectively fixed to keep plates 9 with screws 8. When the plate springs 6a and 6b are fixed in the X-shaped form in such way, deformation in the direction shown by the arrow A, namely, the bend of a temporarily fixed part can be simulated easily and, in addition, the elongation of the temporarily fixed part, namely, deformation in the direction shown by the arrow B can be suppressed. Moreover, the rigidity of the transverse vibration in the direction shown by the arrow C and torsion in the direction shown by the arrow D is large.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bridge model for wind tunnel testing used for verifying the wind resistance performance of blocks in a temporary structure in suspension bridge construction.

[Conventional technology]

In wind tunnel tests to examine the wind resistance performance of bridges, the conditions required for the bridge model are the shape of the model so that the wind flow is similar, the form of vibration, and the stiffness and weight or compensatory moment that are similar. . Fig. 5 is a partial perspective view of a bridge model used for general wind tunnel testing, and the wind flow is similar in the external shape member o3 as a bridge girder model suspended from cable 01 via hanger lobe o2. The bottom of the groove is shaped like a model. The outer material 03 is composed of an upper structure 03b and a lower structure 0, as shown in the exploded view of the left end of the figure.
A rigid rod o5 is passed through the center of the bridge to simulate the bending and torsional rigidity of the model bridge girder, and a cable anchoring fitting 04 through which this rigid rod 05 passes is designed to simulate the weight of the model bridge girder. It is suspended from the hanger rope 02.

In a normal bridge model, the external member 03 that becomes the bridge girder is divided into longitudinal sections as described above, but the rigid rod O5, which is responsible for the rigidity of the bridge girder, is made by passing it through a single long object. It is made.

[Problem to be solved by the invention]

Conventional wind tunnel tests have used the above-mentioned bridge model whose configuration was studied for the purpose of investigating the wind resistance performance of a completed bridge, but when investigating the wind resistance performance of a bridge under construction, it is necessary to examine the shape and rigidity of the bridge. should be completely different from the bridge model described above.

Figure 3 shows an example of constructing a suspension bridge using the block construction method. To construct a suspension bridge using the normal block construction method, first build the main tower 40, then hang the main cable 10,
Next, the bridge girder blocks 30 constructed from the main tower 40 are successively connected by lowering the rope 20. In this case, the end faces of the bridge girder block 30b suspended from the hanger rope 20 are butted against the end faces of the already fixed bridge girder block 30a and welded, and finally both end faces of the bridge girder block in the center are welded to the adjacent bridge girder blocks. Complete by welding. This construction method has a good track record and is highly regarded as a reliable construction method, but because the bridge girder blocks 30 are welded one after another, it takes a long time to arrange all the bridge girder blocks, and during this period, work vessels such as block carriers and crane ships This is a defective construction method when constructing a bridge in a strait or other area where there is heavy ship traffic.
A review has been requested, and other temporary construction methods are being considered as an alternative construction method.

Figure 4 shows an example of a bridge block used in the temporary fixing method, which is a variation of the block construction method.

In other words, the bottleneck of the conventional construction method is that the bridge girder blocks 30 are welded one after another, which increases the time required to occupy the straits, etc. However, as shown in Fig. 4, adjacent bridge blocks 30a and 30b are temporarily welded. If the process is changed so that all the blocks are hung on the hanger rope 20 and then welded, the time required to occupy the strait where ships and the like come and go can be greatly reduced.

Each bridge girder block 30 is temporarily fastened by connecting the temporary flanges 50a and 50b at multiple locations on the upper end faces of adjacent bridge girder blocks 30a and 30b with bolts 51, and then connecting the lower part of the bridge block with an oval connecting hole 52a. and 52b are loosely fastened with hooks or U-bolts 53. This is a temporary fix until A (A), and it will be adjusted before the actual welding, and before that adjustment, it is necessary to allow one bend I at the joint of each bridge block.However, this temporary fix Even in this construction method, it takes a long time to weld between bridge blocks, and it is necessary to investigate the wind resistance performance of a temporarily fixed suspension bridge.For this purpose, it is important to consider the structure and rigidity of the model for wind tunnel tests. Although necessary, such a bridge model for wind tunnel testing has not been considered to date.

In other words, in the bridge model for wind tunnel testing, as shown in Fig. 5, the rigidity of the block-type external member 03 as a bridge girder is taken care of by the rigid rods 05, so the rigidity of the bridge girder using the temporary fixing method is To simulate this, it is possible to connect short rigid rods for each block with hinges. However, it is extremely difficult to equalize the friction coefficients of a large number of hinges, and the presence of friction loss at the joints of the blocks is a problem because it has a damping effect when examining the vibration characteristics due to wind.

In order to carry out the above-mentioned temporary fixing method, the present invention aims to investigate the wind resistance performance of each block in the process of constructing the bridge girder blocks by temporarily fixing each other, which are suspended from the main cable via hanger ropes. The purpose of the present invention is to provide a bridge model for wind tunnel tests in which short rigid rods are connected to each other in an X shape.

[Means to solve the problem]

For this reason, in the bridge model for wind tunnel testing of the present invention, in the bridge model used for wind tunnel testing to verify the wind resistance stability of the bridge, rigid rods divided into each bridge girder block of the bridge to be simulated are connected using X-shaped spring members. It is characterized by what it did.

(Function) X-shaped springs have greater tensile and torsional rigidity than bending rigidity (
Through careful calculations, it is possible to simulate the actual temporary fixing condition of the bridge blocks used in the temporary fixing method shown in Figure 4, and the wind resistance performance of the construction process in the temporary fixing method can be confirmed by wind tunnel tests. I can do it.

[Example] FIG. 1 is a sectional view of an example of a rigid rod connection fitting for a bridge model for wind tunnel testing according to the present invention, and FIG. 2 is a plan view thereof.

A mounting bracket 7 having a mounting surface whose upper and lower surfaces are machined at 45 degrees with respect to the bridge axis is fixed to both ends of a rigid rod 5 cut for each model block, and a pair of mounting brackets 7a to be connected. 7b
The leaf spring materials 6a and 6b are installed in an X shape between the two. Here, the leaf springs 6a are two leaf springs facing downward to the left in FIG. 1, and 6b is a wide leaf spring (equal to twice the width of 5a) facing downward to the right. It is fixed to the mounting bracket.

When the leaf spring is installed in an X shape like this, the arrow A in Figure 1
Deformation in the direction, ie, bending of the temporarily fastened portion, can be easily simulated, and elongation of the temporarily fastened portion, ie, deformation in the direction of arrow B, can be suppressed. In addition, the lateral vibration in the direction of arrow C in Figure 2 and the torsional stiffness in the direction of arrow '' are large, so if the temporary fixing method for a real bridge as shown in Figure 4 is decided, then the X-shaped springs will be adjusted accordingly. Can be made similar in design.

〔Effect of the invention〕

According to the above-mentioned bridge model for wind tunnel testing of the present invention, by using X-shaped springs to connect the rigid rods of the bridge model, αfi←Sasaboku Bridge 1 is made similar to αfi←to examine the wind resistance performance during the construction process of the temporary fixing method. This makes it possible to use wind tunnel tests to confirm the success or failure of the temporary fixing method when constructing a structure in a strait where there is heavy ship traffic.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a rigid rod connection fitting according to a first embodiment of the present invention, and FIG. 2 is a plan view thereof. Fig. 3 is a conceptual diagram of the suspension bridge construction method, Fig. 4 is a diagram showing the connection state of bridge girder blocks in the temporary fixing method, and Fig. 5 is a partial perspective view of a conventional suspension bridge model for wind tunnel testing. 5... Rigid rod, 6... Leaf spring, 7... Mounting bracket,
8...screw, 9...pressing plate.

Claims (1)

[Claims] A bridge model for wind tunnel testing, which is used for wind tunnel testing to verify the wind resistance stability of a bridge, and is characterized in that rigid bars divided into each bridge girder block of the bridge to be simulated are connected by X-shaped spring members.