In order to adjust the displacement and connection between the bridge superstructure, expansion joints need to be set
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After the concrete is vibrated and compacted, the cement slurry shall be rubbed out with a trowel board and troweled and leveled in 4 to 5 times
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3、 Disease and prevention measures of bridge expansion joint under the action of vehicle load and the influence of various factors, the expansion joint is easy to be damaged, such as cracking and damage of anchor concrete, jamming of expansion joint, material aging, damage of anchor and damage of rubber strip
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3.2.1 strengthen the quality control of raw materials, and the accessories such as expansion joints, special-shaped steel and rubber strips entering the site shall be consistent with the design; The length of the expansion joint shall be measured on site by the manufacturer’s personnel and processed according to the actual length to eliminate the error between the design and the actual length and facilitate installation; Special shaped steel shall be handled with care during transportation, and shall not be damaged or deformed; When stacking, it shall be padded with sleepers to avoid wind and rain
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2.4.3 after fixing, the elevation of the expansion joint shall be measured again
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1.2 bridge expansion joints are divided into the following five categories: steel support type, combined shear type (plate), module support type, butt joint and seamless expansion joints
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What are the construction methods of bridge expansion joints? What disease control measures are there? Collect it! 1、 Function and classification of highway bridge expansion joints 1.1 function of bridge expansion joints because the bridge is outdoors, the beam body will produce displacement under the action of dynamic load, temperature, concrete shrinkage and creep
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The expansion joints of the bridge are damaged, sunk and staggered, which will have a jump impact on the bridge when the two vehicles pass, produce additional loads, affect the driving comfort, and produce safety accidents in serious cases
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At the same time, canvas, plastic cloth, plastic film and straw cover for maintenance to prevent road pollution must be equipped to ensure the smooth progress of construction
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The reinforcement mesh 3mm lower than the pavement elevation shall be measured on both sides
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2.2 before construction, set out the joint according to the construction design drawings, use the cutting machine to observe the joint, pay attention to the protection of the road outside the joint line, prevent pollution, and ensure that the joint cut is intact
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The slump of the concrete shall be less than 2cm
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After the expansion joint is welded firmly, the temporary fixing fixture and positioning angle steel shall be removed to make it expand freely
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2.4.4 template installation, the template generally uses foam board, fiberboard, thin iron sheet and so on, and the installation must be firm and strict, ensure that concrete does not move during vibration, prevent mortar flow into the seam, affect the use of expansion joints
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Or the position of embedded reinforcement is inaccurate, the strength of filled concrete, curing time, adhesion and flatness fail to meet the design standards, and the prefabrication and installation of beam and slab do not meet the design requirements; 3.1.4 large traffic flow, fast speed, many loaded vehicles and the impact force of wheels cause damage, falling off, loosening and even damage to the components of the expansion device, which seriously affects the driving safety; 3.1.5 improper daily cleaning and maintenance of expansion joints
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2.4.1 before installation of expansion device, check the anchorage width of embedded reinforcement of expansion joint
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2、 Construction technology of expansion joints of highway bridges 2.1 construction preparation before construction, be familiar with relevant construction drawings and installation and operation procedures of expansion joints, and check the flatness, straightness and joint clearance of special-shaped side beams; According to the actual situation of the project, sufficient mechanical equipment and small machines and tools must be equipped, and the springboard must be of solid quality to enable passing construction vehicles to pass smoothly
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3.2 prevention and control measures: reasonably select the expansion joint device to ensure the stiffness of the expansion device and the strength and quality of the anchor; The anchorage of the expansion device shall be firm, reliable and durable, which can resist the influence of machinery, friction and collision
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2.5 before concrete pouring, the two joints shall be paved with plastic cloth to avoid concrete polluting the pavement
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Generally, it should be set at 50cm, and the width of the back wall is easy to be used on the abutment, which not only strengthens the stability of the expansion joint device, but also facilitates the construction of the bridge deck; Remove the sundries in the expansion joint groove with a high-pressure water gun and check whether it is clean
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The concrete surface shall be kept wet frequently
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However, due to improper design, poor installation quality and lack of scientific and timely maintenance, the vehicle will jump at the expansion joint, which is a common disease in China and is becoming more and more prominent
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It shall be constructed according to the specifications to make the vehicle run smoothly, strengthen maintenance and check frequently
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The center line of the expansion joint shall coincide with the center line of the beam end, and the elevation of the top surface of the expansion joint shall be lower than that of the asphalt concrete pavement (1 ~ 2mm)
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At the place where the expansion joint is set, the railing shall be disconnected from the bridge deck pavement
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In bridge engineering, it is required that the expansion joint can expand freely in two directions parallel and perpendicular to the bridge axis, be firm and reliable, and the vehicle shall run smoothly without sudden jump and noise; It shall be able to prevent rainwater, garbage and soil from penetrating and blocking; Installation, inspection, maintenance and elimination of dirt shall be simple and convenient
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In order to eliminate the phenomenon of steps and car jumping, many effective methods have been adopted in China, among which the installation of bridge expansion joint is a very important project, and the construction defects can not be ignored
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After confirming that there is no deformation and deviation, the anchor reinforcement and embedded reinforcement shall be welded firmly on both sides at the same time, and all at one time
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During the installation process, check the straightness and flatness of the section steel of the expansion joint
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The curing period shall not be less than 7 days
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2.6 curing before the initial setting of cement concrete, roughen with a brush, cover with plastic cloth, gunny bag, etc., and spray water for curing
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Vehicles are strictly prohibited from passing during the interval
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2.3 the air pick shall be used for grooving
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Before temporary fixing and spot welding, the elevation and straightness shall be adjusted to meet the design requirements, When fixing, weld a welding spot every 2-3 anchor bars from one side of the bridge width to the other side according to the anchor device of the side beam of the expansion joint and the embedded reinforcement of the reserved groove
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Pay attention to the distance between the welding point and the section steel to ensure that the section steel is not deformed
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It can only be used after passing the inspection; The on-site mix proportion, raw materials, reinforcement and other test results can be used only after they meet the requirements.
The concrete and sundries in the groove, especially the sundries in the beam end gap, shall be removed, and the embedded reinforcement in the groove shall be straightened and straightened
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If the welding is not good for construction, one side can be welded first, and then the other side
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In order to ensure that the expansion joint does not shift, weld symmetrically from both sides, and it is strictly prohibited to translate from one end
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3.1 the reasons are: 3.1.1 improper design, insufficient design quantity, improper type selection, and no clear provisions on the filling materials such as post cast concrete and pavement materials on both sides; 3.1.2 the expansion joint device itself is not rigid enough, and the anchor strength is not enough, resulting in varying degrees of damage under repeated load; 3.1.3 improper construction method, improper material selection, spacing not set according to the design requirements, incorrect position of positioning angle steel, and unstable welding of anchor reinforcement
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2.4.2 during installation and fixation, the gantry hanger and 10 * 10 angle steel shall be used as positioning angle steel
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Check the flatness of the section steel
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If the displacement is too large, it will affect driving comfort and safety
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In order to reduce the water cement ratio and improve the early strength, admixtures can be added to reduce the shrinkage of the concrete surface
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When the welder on one side has a large amount of work for a long time and the temperature difference has a great impact, the left, middle and right parts of the other side can be welded for anchoring after welding on one side, and other anchor bolts on the other side can be welded at the same time
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In order to prevent jumping, the flatness of section steel shall be controlled within 0-2mm according to the specification requirements
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If the quantity of embedded reinforcement is found to be insufficient, expansion bolts shall be made to supplement the embedded reinforcement, and the owner’s representative and supervisor shall jointly accept it to ensure the quality of the expansion joint
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The flatness shall be controlled within 2mm, the straightness shall be controlled within 3mm, and the height difference between the top surface and the road surface shall be controlled within 2mm
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Strictly control the flatness of the concrete surface to make it flush with the top surface of the expansion joint device
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The rubber sealing strip can be installed only after the strength reaches more than 50% of the design strength
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