Good bridge expansion joints should meet the following requirements: free expansion in both directions parallel and perpendicular to the bridge axis; no sudden jump and noise when vehicles drive by; prevent blockage caused by rainwater and garbage infiltration; easy construction and maintenance, etc. As a kind of advanced bridge expansion joint device,expansion joint is easy to construct and install, contraction of expansion joint is free, no sudden jump when driving, and it can meet the requirements of high-speed driving. Here is a look at the construction process expansion joints.
Bridge expansion joint: It means that in order to meet the requirements of bridge deformation, expansion joints are usually set up between the two beam ends, between the beam ends and the bridge abutment or at the articulation position of the bridge. The expansion joints are required to be free to expand and contract in both directions parallel and perpendicular to the bridge axis, firm and reliable, and the vehicles should be smooth and without sudden jump and noise when driving through; they should be able to prevent rainwater and garbage and soil from infiltrating and blocking; installation, inspection, maintenance and elimination of dirt should be easy and convenient. In the setting of expansion joints, the railing and bridge deck pavement should be disconnected.
The role of bridge expansion joints: is to regulate the displacement and linkage between the superstructure caused by the vehicle load and the bridge construction materials. Once the expansion joint of an inclined bridge is damaged, it will seriously affect the speed, comfort and safety of traffic, and even cause traffic safety accidents.
Bridge expansion joints refer to the expansion joints usually set between the two beam ends, between the beam ends and the bridge abutment or at the articulation position of the bridge in order to meet the requirements of bridge deck deformation. Expansion joints are an important part of bridge construction. Under the influence of temperature change, concrete shrinkage, live load, settlement of bridge piers and creep, the structure on the bridge span is also deformed, thus causing the displacement of the beam end again. Bridge expansion joints are also important in the preparation work before construction, the following together to understand some of the installation requirements and construction methods before installation.
Bridge expansion joint safe installation requirements.
- The construction unit is required to lift the expansion joint into position, check whether its centerline coincides with the centerline of the beam joint and whether its top surface is consistent with the road elevation, and make timely adjustment. Weld the pre-buried reinforcement and the expansion joint anchor firmly, and then cross the 12 or 16 horizontal reinforcement. Be sure to immediately remove the expansion joint positioning pressure plate, burr the positioning screws, and use the angle grinding wheel to grind away the welding scar and make up the paint. Seal the top surface of the expansion joint with adhesive paper tape or wooden board, pour concrete in the slot area; use inserted vibrating rod, fully vibrate and compact, smooth the surface of the concrete over section, check the top surface of the expansion joint and over section with a straight edge, it should be smooth with the road surface as far as possible, and do a good job of concrete regeneration before opening to traffic.
- Before the installation of the bridge expansion joint, check whether the expansion joint has the factory certificate of conformity, instruction manual, etc., and ask the supervisor, design and relevant personnel to check and accept the appearance and geometric accuracy of the expansion joint, and use it only after it is qualified. Scribing and cutting on the bridge: put out the center line of the expansion joint according to the design position, and measure the edge of the concrete protection zone of the expansion joint according to the design size from the center line position, and cut the asphalt concrete of the bridge deck with the concrete cutting machine according to the drawn edge line. To ensure that the cutting edge is not damaged, it can be cut in two times. The first cut is 5cm away from the edge line of the protection zone, and the second cut will be made along the exact edge line before concrete is poured. Cutting requirements straight, accurate, cutting care should not damage the bridge waterproof layer, the waterproof layer rolled up to protect.
- Must be timely bridge deck cleaning, filling the gap: manual with air compressor to remove the cutting range of asphalt concrete, and chisel out the loose concrete, while cleaning up the debris in the joints. The width of the joints must meet the design width requirements, and after cleaning up the expansion joints will be blocked tightly with benzene sheets. Restore the pre-buried anchor bars, the number of pre-buried reinforcement should match with the design drawings, if not, make up the welding in time. Clean up again with air compressor. In order to prevent the expansion joint installation process welding flowers burned foam board, can be covered with steel plate or iron on both sides of the foam board to protect. Point me: send engineering practical dry goods.
- When the expansion joint to be installed is in position to be lifted by crane, the hook of the crane should be checked to prevent decoupling, and the lifting should be carried out strictly in accordance with the lifting position reserved by the manufacturer, and the steel bars should be tied and rolled according to the design drawings. In the process of fixing, the centerline and straightness of the expansion device are controlled by the method of drawing a line, and the elevation is controlled by using I-beam or aluminum alloy steel with a length greater than 3m and sufficient rigidity to lap on both sides of the expansion joint. The I-beam is placed at 1m spacing along the direction of vertical expansion joint and pressed against the road surface on both sides of the joint, and the expansion joint profile is padded with wooden wedges, and then leveled section by section with 3m straightedge with self-made small gantry, and steel wedges should be used in the leveling process. After the expansion joint is in place, the centerline and elevation of the expansion joint should be adjusted, and the elevation should be determined according to the measured road elevation within 5m on both sides of the joint.
The installation methods of bridge expansion joints are as follows.
- The installation shall be carried out after the pavement is paved as far as possible, and the width and depth of the reserved slot and the pre-buried reinforcement shall be checked before the installation so that they meet the requirements for the installation of the expansion joint.
- Clean up the slot all dirt, dust and other unnecessary things are all removed.
- With the asphalt pavement on both sides as the elevation, use lifting equipment to place the expansion joint in the slot so that its top surface is the same as the pavement elevation.
- Check the position of the expansion joint so that it meets the design requirements. If individual pre-built reinforcement at this time is an obstacle to the correct installation of the expansion joint, it can be cut off with gas cutting.
- Carry out welding between the expansion joint and the reinforcement on the bridge. After the expansion joint is correctly in place, firstly connect the anchoring bars on one side of the expansion joint with the pre-buried steel bars in the reserved slot and weld them, you can weld one at an interval, then weld the anchoring bars on the other side according to the above steps. After the expansion device is confirmed to be fixed, the fixture can be removed, and then the remaining unwelded anchorage bars are completely welded with the pre-buried bars to make the expansion device reliably anchored.
- Formwork installation. Fill the foam board to ensure that the concrete is poured without leakage.
- Installation of comb-plate type expansion device should prevent unevenness of comb teeth, distortion and other deformation.
- Concrete pouring and maintenance. After pouring concrete for the last cleaning and flushing of the seam slot, cover the concrete pavement on both sides of the slot with material cloth or thatch cloth to prevent the concrete from polluting the pavement or flowing into the seam opening and control box during construction. Concrete is poured and formed, and after the concrete is finally set, the base surface is covered with sprinkling water for maintenance.
- Sealant tape embedded in the expansion joint.
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