What Are the Characteristics of Bridge Finger Expansion Joints?

characteristics of bridge finger expansion joints
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Finger expansion joint is a bridge expansion joint device composed of finger steel plate (formerly referred to as ‘comb’ or ‘tooth’ plates), stainless steel sliding plate, rubber seal sheet, anchor bolts, etc.

1. Characteristics of finger expansion joints

1) Finger bridge expansion joints have large expansion and contraction and are shallowly buried.

It is designed with an allowable expansion of 40 to 1000mm. It is suitable for various non-girder structures, new bridges of different spans, and reconstruction of old bridges. It has a large expansion and contraction and a wide range of uses.

The finger expansion joint has an overall structural height of 30 to 40 mm. It does not need to change the original beam end structure and can achieve effective anchoring strength by shallow burial.

2) The finger expansion joint has an automatic slag-cleaning function

There is a common problem with other types of expansion joints, that is the gap is blocked by ash and hard objects, which in severe cases affects the normal expansion of the beam body. Due to the special structure of the finger expansion joint device, the gap is located on the end face of the single-side beam. At the same time, there is a stainless steel slide pad on the bottom. Ash and hard objects can only stay on the surface. In this way, ash and hard objects can be automatically discharged from the expansion gap with the help of the expansion and contraction process of the finger steel plate and the action of the vehicle.

3) The finger expansion joints have excellent waterproof and dustproof properties

The finger expansion joint device is equipped with a two-layer neoprene waterproof layer, and waterproof ointment is poured into the expansion gap of the finger-type steel plate to achieve excellent waterproof and dustproof effects.

4) The finger expansion joint has good overall performance with the road surface

The finger expansion joint device adopts a rigid-flexible structure and has good overall rigidity. Therefore, the vehicle runs smoothly without impact and vibration, reducing the impact force of the bridge and reducing noise.

2. Installation of finger expansion joints

1. Place the sample and cut the concrete according to the width.

2. Clean up debris to a depth of at least H value.

3. Use the bolt hole combination template for setting out and positioning, and the screw position error is ≤1mm. When drilling, the internal structure of the beam, such as prestressed pipes, steel bars, etc., must not be damaged.

4. Bind the transition bottom steel grid, erect the formwork, and pour C40 steel fiber concrete. The elevation and flatness of the top surface must be strictly controlled, and its flatness should be 0-1mm (mm).

5. Bind the steel bars distributed in the transition area.

6. Pour C40 steel fiber concrete in the transition area.

7. Install the water-stop neoprene sheet, stainless steel plate, and toothed plate, and tighten them with nuts. In order to prevent the screw and nut from loosening, anti-loosening glue must be applied to the threads, a small amount of spot welding is performed on the screw and nut surfaces, and finally waterproof and anti-loosening epoxy resin is poured into the screw hole.

8. Concrete should be watered and maintained, and it should be protected from freezing and moisturizing in winter.

9. Fill the tooth-shaped seams with waterproof ointment.