Chinese name: building expansion joint mbth: expansion joint alias: expansion joint function: make the building expand horizontally in the long direction. Applicable to: the top of the building and above the building. Type: GQF-C, GQF-Z, GQF-E, etc. Others: expansion joints are also called temperature joints. Subject classification: civil engineering application field: main functions, types, structural requirements, design points, construction procedures, control points, safety installation, damage causes, matters needing attention, material composition, development and improvement, impact mitigation, improvement ideas, existing problems, etc. Its practice is to reserve gaps at regular intervals along the length of the building to disconnect the building from the above-ground components such as roofs, walls and floors. Because the building foundation is buried underground and is not affected by temperature changes, it is not necessary to disconnect it. The width of expansion joints is generally 20mm ~ 30mm, and thermal insulation materials are filled in the joints. The spacing between two expansion joints is clearly defined in the building structure code. If the plane size of the building is too long, it may cause excessive temperature stress in the structure due to thermal expansion and contraction. It is necessary to set a joint on a certain length of the structure to divide the building into several parts, which is called temperature joint. For different structural systems, the spacing of expansion joints is different, and the current Code for Design of Concrete Structures (GB500 10-20 10) has special provisions in Article 8. 1. GQF-C, GQF-Z, GQF-E, GQF-F and GQF-MZL bridge expansion joints are all bridge expansion joints designed by hot rolled integral steel. Among them, GQF-C, GQF-Z, GQF-L and GQF-F bridge expansion devices are suitable for bridges with expansion below 80mm, and GQF-MZL bridge expansion device is a modular bridge expansion device composed of side beams, middle beams, cross beams and linkage mechanisms, which is suitable for large and medium-span bridges with expansion below 80 mm- 1200 mm. (3) The passing vehicles should be smooth without sudden jump and noise; (4) Waterproof, preventing sundries from penetrating and blocking; (5) Installation, inspection, maintenance and removal of dirt should be simple and convenient. The key points of design are that it is extremely important to choose the appropriate telescopic gap reasonably. The bigger the gap, the easier it is for the expansion and contraction device to be damaged. The gap used is too large or too small, and the temperature is not considered when adjusting the gap during installation. Especially for the plate rubber telescopic device, it is easy to cause damage. Even on the continuous bridge deck, cracks often appear on the surface pavement. Therefore. It is necessary to cut the bridge deck in advance, set joints, or use soft pavement to absorb cracks, or install small telescopic devices to solve the problem. In the case of large longitudinal slope, if there is no structure suitable for vertical displacement, it is easy to produce defects and cause damage. The expansion device is along the longitudinal direction of the bridge deck, and even if the expansion amount is small, there is a problem of large deflection difference. Therefore, attention should be paid to the structure of the expansion device. It is undoubtedly an important means to improve the use efficiency of the telescopic device and the beam by combining the telescopic device and the beam into a whole with equal strength. Other types of bridge expansion devices, except modular expansion devices, are often not fully combined with bridge deck fixation, and the effect is not ideal. Generally, the structure size is small, the stiffness is insufficient, and the research on the characteristics and cooperation of new materials is not deep enough, so a full comparative study should be carried out when selecting the type. In order to prevent rain and water leakage, although in some steel expansion joint devices, sealing rubber is inserted in the matching part, or the drainage device or pavement is easy to clean, or the whole gap is filled with waterproof material. For the rainwater on the bridge deck, a centralized drainage outlet should generally be set near the telescopic device; For parts that are not painted many times in daily maintenance, high-quality and durable protective materials should be used for effective treatment in the design. Whether it is cement concrete pavement or asphalt concrete pavement, reverse grooving construction should be adopted: releasing reserved notches → cutting reserved slots of expansion joints → adjusting pre-embedded steel bars of expansion joints → removing impurities in notches → placing expansion devices → checking elevation → locking and binding steel bars → formwork support → checking pouring concrete. Control point 1. If the embedded steel bar on the beam slab is in the wrong position or missing, it is necessary to use the method of planting steel bar to supplement the steel bar. 2, after cutting to clean up, connect the anchorage. 3, steel weld should be enough, welding should be strong. 4, concrete surface elevation should be correct, to prevent tripping. 5. The expansion joint is firmly anchored, not loose, and its telescopic performance is effective. 6, concrete curing time should be enough, don't open traffic because of insufficient curing time. 1 Safety installation requires the construction unit to hoist the expansion joint in place, and check whether its center line coincides with the center line of the beam joint and whether its top surface is consistent with the pavement elevation, and adjust it in time. Weld the embedded steel bar firmly with the expansion joint anchor, and then pass through the horizontal steel bar of 12 or 16. Be sure to remove the positioning pressure plate of the expansion joint immediately, chisel off the positioning screw, remove the welding scar with the angular grinding wheel and touch up the paint. Seal the top joint of expansion joint with adhesive tape paper or wood board, and pour No.50 concrete at the notch; Use plug-in vibrator to fully vibrate and compact. Smooth the surface of concrete transition section. Check the top surface and transition section of expansion joint with a ruler, and try to be flush with the road surface. Do a good job of concrete curing before opening to traffic. Expansion joints with anti-collision walls and sidewalk structures shall participate in the above installation procedures. 2. Before installation, check whether the expansion joint has the factory certificate, instruction manual, etc. And invite supervisors, designers and relevant personnel to inspect and accept the appearance and geometric accuracy of expansion joints. You can only use it if you are qualified. Scribe and cut the bridge: set out the center line of the expansion joint according to the design position, measure the edge line of the concrete protective belt of the expansion joint from the center line according to the design size, and cut the asphalt concrete on the bridge deck according to the drawn edge line with a concrete seam cutter. In order to ensure that the trimming is not damaged, it can be cut twice. The first incision is 5 cm away from the edge of the protective belt. Before concrete pouring, cut a second cut along the precise edge. Cutting seam should be straight and accurate. Be careful not to destroy the waterproof layer of the bridge deck when cutting, and roll up the waterproof layer to protect it. 3. Clean the bridge deck in time and fill the gaps: manually cooperate with the air compressor to remove the asphalt concrete within the cutting range, chisel away the loose concrete and clean up the sundries in the joints. The joint width must meet the design width requirements. After cleaning, use benzene board to block the expansion joint tightly. Restore the embedded anchor bars, and the number of reserved steel bars shall conform to the design drawings. If not, it should be repaired in time. Clean again with an air compressor. In order to prevent the foam board from being burnt by welding flowers when installing expansion joints, both sides of the foam board can be covered with steel plates or iron sheets for protection. 4. When the expansion joint to be installed is hoisted in place by a crane, the hook of the crane should be checked to prevent it from being unhooked. When hoisting, it shall be carried out in strict accordance with the hoisting position reserved by the manufacturer, and steel bars shall be bound and rolled according to the design drawings. In the process of fixing, the center line and straightness of the expansion device are controlled by pulling wires, and I-beams or aluminum alloy steels with sufficient rigidity and length greater than 3m are placed on both sides of the expansion joint to control the elevation. I-beams are placed at a distance of 1m along the direction perpendicular to the expansion joint and pressed on the pavement on both sides of the joint. The expansion joint reinforcement shall be leveled with a wooden wedge, and then accurately leveled segment by segment with a 3m ruler and a self-made gantry. Steel wedge should be used in leveling process. After the expansion joint is in place, the center line and elevation of the expansion joint should be adjusted, and the elevation should be determined according to the measured pavement elevation within 5m on both sides of the joint. Damage reason 1, poor design of bridge expansion joints. The beam end is not carefully considered in the design. Under the repeated load, the beam end damage leads to the failure of the telescopic device. In addition, sometimes the deformation calculation is improper and the telescopic distance is too large, which leads to the damage of the telescopic device. 2. There is something wrong with the expansion joint device itself. The structural rigidity of the expansion joint device itself is insufficient, and the strength of the anchored members is insufficient, which leads to different degrees of damage in the operation process. 3. Improper selection of post-pouring and pressure-pouring materials of the expansion device has not been paid attention to and carefully selected, which leads to the decline of the operation quality of the expansion device and the occurrence of diseases in different degrees. 4. The construction is unscientific and unreasonable. During the construction process, the expansion joint spacing at the beam end was not completed according to the design requirements, which was artificially increased and decreased, and the positioning angle steel position was incorrect, which led to the failure of the expansion device to work normally. In this way, the following situations will occur: (1) Because the joint distance is too small, the rubber expansion joint will bump due to over-limit extrusion bulge; Because the gap is too large, the shear force under load and the inertia of the vehicle will take the loose expansion joint rubber out of the positioning angle steel, causing another bump. During construction, the welding of the anchor bar of the expansion device is not firm enough, or the embedded anchor bar is omitted, which causes hidden dangers to the expansion joint itself; The expansion device is not installed well during construction, and the expansion joint is not poured well after deck pavement. In use, the expansion joint will be damaged under repeated load. 5. The setting of continuous joint is not perfect. In order to reduce expansion joints, continuous beams or continuous bridge decks are widely used. When the bridge deck is continuous, it is necessary to set continuous joints, and the setting of continuous joints is not perfect, which leads to the damage of continuous joints and the bridge deck bumping. At the continuous joints of bridge deck, the width and depth of deformed false joints are not standardized and unified, which also affects the normal work of continuous joints to varying degrees. Note 1. Due to the limitation of transportation length, the telescopic device can be manufactured in sections and assembled on site. Telescopic devices stored in the construction site shall be placed in parallel, and shall not be stacked cross to prevent deformation. 2. When leaving the factory, the connecting fixture is only designed for convenient transportation, and the gap is not fixed. The installation of expansion device shall be approved by the supervision engineer. If there are provisions in the design documents, the provisions in the bridge design documents shall prevail. 3. Before the telescopic device is hoisted in place, the concrete in the reserved groove shall be chiseled and cleaned. During installation, the width a of the expansion device along the bridge direction should be symmetrically placed on the gap of the expansion joint, and the elevation of the top surface should be consistent with the design elevation. Then, the horizontal steel bar in the horizontal direction should be penetrated, and the anchoring steel bar on the expansion device should be welded firmly with the embedded steel bar on the beam (increase the welding point and welding length as much as possible to prolong the service life of the expansion device), and the fixture should be loosened to make it freely expand and contract. At this point, the expansion device has entered the working state. 4, after the completion of the above process, install the necessary template, in order to prevent mortar from flowing into the expansion joint, and then carefully clean with water. Pouring concrete greater than C50 in the reserved concrete tank. Necessary measures should be taken when pouring concrete, vibrating compaction. 5, after the initial setting of concrete, pull out the template, keep clear of foreign bodies in expansion joints and special-shaped steel tape groove in time. Material composition: 1, galvanized steel plate expansion joint. This is a simple expansion joint. When the deformation of the beam is within 20-40 mm, it is often used for small and medium-span assembled simply supported beam bridges. Steel expansion joint. The steel expansion joint is made of steel, which can directly bear the vehicle load, and the thickness of the steel cover plate can be adjusted according to the expansion amount. Steel expansion joints are also suitable for trial use on skew bridges. Its structure is complex, and it is only used in areas with large temperature difference or bridges with large spans. When the span is large, on the one hand, it is necessary to thicken the steel plate, on the other hand, it is necessary to adopt a more perfect comb-shaped steel plate expansion joint. 3. Rubber expansion joint. It uses rubber belt as cross-stitch material. This expansion joint has simple structure, convenient use and good effect. Expansion joints made of rubber and steel plates can be used on large-span bridges with large deformation. Develop and improve the rigid abutment structure to reduce the impact and the bump at the bridge head due to the deformation of artificial fill or the consolidation and settlement of natural soil foundation under the repeated action of traffic load. Bumping at the bridgehead not only directly affects the driving comfort and increases the driving risk, but also aggravates the damage of the pavement on both sides of the expansion joint due to the frequent braking, braking and impact of vehicles at the bridgehead. Therefore, solving the bump at the bridge head has always been a very important problem in expressway design. There are many ideas to improve the treatment of bump at the bridge head, such as changing materials, preloading, composite foundation, geogrid, reinforced abutment and so on. Bridge end transition slab is the most widely used method, and Hebei Province has basically adopted bridge end transition slab's disposal plan. In recent years, the description of bridge end transition slab and elastic joint structure follows a traditional habit, that is, elastic equipment is installed between the main beam and the back wall of abutment, bridge end transition slab is placed on the bracket behind the back wall, and structural joint is formed between the strap and the back wall of abutment. The investigation of practical engineering proves that the application effect of this structural form is not ideal, so it is necessary to improve it. There is a problem 1. There is a transverse hard joint between the abutment back wall and the plate end. Although asphalt hemp yarn is required to be filled in the joint as waterproof material during construction, in actual construction, asphalt concrete pavement is easy to be damaged due to the expansion and contraction deformation of the joint and the deformation of the plate end. The result of this damage is pavement cracking, surface water permeates down along the joint, and directly washes the abutment back fill, which makes the abutment back fill soft, deformed or lost, resulting in subgrade settlement and cavity under the slab. 2. The settlement of the tail end of the strap will cause the front end to have a corner and vertical displacement, which will cause a height difference between the two ends of the joint. Because the gap between the joint and the elastic joint is very short, when the car bumps rapidly here, it will bump twice in a row. The greater the span, the higher the fill, the more obvious the bump and the greater the vibration. 3. The impact load caused by repeated braking, braking and jumping at the bridge head aggravated the damage of the pavement and expansion device at the joint side. Solving the above problems can reduce the impact of the expansion joint and its bridge end transition slab disadvantages, realize the long-term use of the expansion joint and reduce the replacement times.