Subject:
How to make bridge (Nov 28, 2022)
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Originally published as How to make bridge expansion joints? These on-site construction workers are already worried about losing their hair! In order to meet the requirements of bridge deck deformation, expansion joints are usually set between two beam ends, between beam ends and abutments, or at the hinge position of the bridge. The expansion joint is required to be able to expand and contract freely, firmly and reliably in two directions parallel and perpendicular to the axis of the bridge. The vehicle shall run smoothly without sudden jump and noise. It shall be able to prevent the infiltration and blockage of rainwater, garbage and soil. The installation, inspection, maintenance and elimination of dirt shall be simple and convenient. At the place where the expansion joint is set, the railing shall be disconnected from the deck pavement. Overview of expansion joints Brief introduction of bridge expansion joints The function of bridge expansion joints is to accommodate the displacement and coupling between the superstructure caused by vehicle loads and bridge construction materials. Once the expansion device of skew bridge is damaged, it will seriously affect the speed, comfort and safety of driving, and even cause traffic accidents. Expansion joint function: Ensure free expansion and contraction of beam body Make the vehicle run smoothly Good water tightness and drainage Convenient for removing dirt in the groove The expansion and contraction of the bridge is exposed to the atmosphere for a long time, and the use environment is relatively harsh, which is the most vulnerable and difficult to repair part of the bridge structure. The destruction of bridge expansion joints may cause great vehicle impact load and worsen the driving condition, which will lead to vehicle jump, noise, water leakage, affect the safety of driving and sharply reduce the service life of the bridge. Hazards of loss of function or damage to expansion joints: The expansion and contraction is blocked, or the top of the pier and abutment is damaged, or the internal force of the beam body is increased The vehicle jumps and runs unstably The impact increases, causing damage to the bridge, especially at the end Water seepage endangers durability Expansion joint model The bridge expansion joint models are: GQF-C, GQF-Z, GQF-E, Gqf-F, and Gqf-MZL, all of which are bridge expansion joint products designed with hot-rolled integrally formed special-shaped steel. GQF-C, GQF-Z, GQF-L and GQF-F bridge expansion devices are suitable for bridges with expansion amount less than 80mm. GQF-MZL bridge expansion joint device is a modular bridge expansion joint device composed of edge beam, middle beam, cross beam and linkage mechanism, which is suitable for large and medium span bridges with expansion amount of 80mm-1200mm. The code representation method is consistent with the standard representation method of the transportation industry of the People's Republic of China. , taking GQF-C60, GQF-F80, GQF-MZL480, gqf-c60 (NR), gqf-f80 (CR) as examples. GQF is the code of expansion joint device specified in the traffic industry standard. Type code: -MZL means modular type, straight beam connecting rod chain type: (C, Z, F, L) indicates the shape of the profiled bar. The number indicates the displacement of the expansion device: 0-1200mm NR and CR indicate the type of rubber: NR indicates natural rubber and CR indicates chloroprene rubber Type of expansion joint Seamless type: blind joint type (continuous bridge deck, TST) Expand the full text Butt joint type: caulking butt joint type, embedded butt joint type (imitating Moeller type) Steel support type (comb plate) Combination type: rubber plate type Modular formula: Mauler formula Seamless The invention relates to a seamless expansion device, which is characterized in that when a joint structure does not extend out of a bridge deck, an expansion gap at the end part of a bridge is filled with an elastic material and paved with a waterproof material, and then a viscoelastic composite material is paved on a bridge deck pavement layer, so that the bridge deck pavement at the expansion joint and the road surface form a continuum, and the expansion of a beam body is absorbed by the deformation of materials such as asphalt concrete, elastic-plastic bodies and the like at the joint, While providing support for the wheel. The common forms are continuous bridge deck, TST gravel elastic-plastic expansion joints and so on. The main characteristics of this kind of expansion device are: ① It can adapt to the expansion deformation and small amount of rotational deformation of the bridge superstructure; ② It makes the bridge deck pavement form a continuous body, which does not produce impact and vibration during driving, and has good driving comfort; ③ The expansion device itself forms a multiple waterproof structure, which has good waterproofness; ④ In cold areas, it is easy to remove snow mechanically and maintain without damaging the joints; (5) that construction is simple and easy, and the maintenance and replacement are convenient. This type of expansion device is generally a structure formed by cutting the pavement with a cutting machine after the construction of the pavement (bridge deck) is completed and injecting caulking material into the notch, which is only suitable for parts with small expansion amount (generally < 40 mm). The service life of the seamless expansion joint adhesive installed in strict accordance with the process requirements is about twice that of the general modified asphalt pavement. Continuous expansion joint of bridge deck TST macadam elastic-plastic expansion joint TST adhesive usually does not become brittle at minus 40 C and does not flow at high temperatures up to 80 C in summer. It can be used normally throughout the country. Because of the high temperature adhesion characteristics of TST, it can be firmly bonded with the existing pavement during construction, and it is not sticky at room temperature, and it will not be taken away after cooling. TST is a kind of special material with high viscoelasticity and plasticity, which is in elastic-plastic state at normal temperature. It can be poured into gravel after melting at high temperature. After forming, it is like asphalt concrete, which can bear the load of vehicles and has elasticity. It can replace the function of small expansion joints. The construction is convenient and fast, and the traffic can be opened after the pavement is cooled. When the expansion joint needs to be replaced, it can be constructed in half. Do not interrupt traffic on busy road sections. Construction technology of TST seamless expansion joint 1) Grooving: set out and cut joints according to the notch width determined by the design requirements, remove the cut pavement materials and clean the notch. 2) Reinforcement planting: drive an expansion bolt at an interval of 25 cm in the transverse direction at a distance of 5 cm from the edge of the notch to a height of 1/2 the depth of the notch, and weld a 12 reinforcement along the seam on the nut inside the bolt. And 3) fil that sponge body, namely cleaning the notch by use high-pressure water, and then baking and drying the surface of the notch by use flame. Fill the gap between adjacent beam ends with sponge rubber strips as much as possible without leaving any gap. 4) Apply the special adhesive for TST evenly on the exposed surface of the notch, pour the melted TST after 15 minutes, and apply it evenly on the bottom and side of the notch with a scraper, with a thickness of 1 ~ 2 mnl. The cross-seam steel plate is then placed to be fixed with a positioning nail, and attention is paid to centering. 5) From one end of the notch, put in the large stones that have been fried (130 ~ 150 ℃), and the thickness is subject to the TST that can see the bottom layer. The TST is then poured in to submerge the stones. Lay layer by layer accordingly. 7) Lay heated small stones, which shall be 10 mm higher than the bridge deck, vibrate them with a plate vibrator, and then scrape them with a scraper. Generally, in order to prevent sinking, it is 1 ~ 2 mm higher than the bridge deck. At this time, it can be trimmed arbitrarily and flattened with a shovel. 8) Pour enough TST to submerge the stones, in order to prevent TST from flowing to the bridge deck on both sides. Both sides of the notch can be blocked with wooden boards to keep the edges neat. 9) Trim the edge, remove the baffles on both sides, cool for 1 ~ 2h, and open the traffic. TST macadam elastic-plastic expansion joint Docking type The filling butt type expansion device is an expansion device which uses the elasticity of the expansion body to bear the wheel load. The expansion body is made of sand, gravel, rubber products of various shapes, foam plastic plates or synthetic resin materials. The expansion body is always in a compressed state. The common types are U-shaped zinc sheet type, wood filling type, asphalt filling type, rectangular rubber strip type, tubular rubber strip type and so on. U type galvanized iron expansion joint is a kind of caulking butt joint expansion joint which was widely used in the 70's and 80's. The main characteristics of this type of expansion device are: ① low cost; ② easy processing of the required materials; ③ simple and easy construction; this type is generally applicable to the expansion amount of Bridges within 40mm are seldom used at present because of their poor durability and waterproofness and short service life. The structural principle of the embedded butt type expansion device is that rubber products with different shapes are embedded and fixed by steel components with different shapes, and then they are anchored with the beam body at the joint or the back wall of the abutment into a whole through an anchoring system. The special-shaped steel provides support for the wheels, and the deformation of the beam end is absorbed by the tension and compression of rubber strips and rubber belts. The telescopic body can be in a compression state or a tension state. This is a kind of expansion device which is widely used in the construction of highway bridges in China at present. The common types are W, SW, M, PG and so on. This type of expansion device is suitable for bridge structures with expansion amount less than 80mm, that is, the joint width is 20mm-80mm. The main characteristics of this kind of expansion device are: ① simple structure, clear stress and low cost; ② the main components of the expansion device are processed by the manufacturer and installed on the construction site, and the connection with the beam end is generally welded by steel bars, so the structure is reliable and the construction quality is easy to guarantee; ③ good durability; ④ good waterproof and drainage performance; ⑤ good driving comfort. The two design principles of Mauler expansion joint are "rigid anchorage" and "sealing and waterproofing". 1) The anchorage of rigid anchorage expansion joint directly affects the service life of expansion joint. The anchoring metal plate mainly plays the role of force transmission. The fatigue tested anchoring device is directly welded on the edge beam. At the same time, the edge beams are rigidly connected to the bridge superstructure to ensure that the expansion joints carry the maximum traffic load. Other methods of connecting expansion joints to the bridge superstructure with screws or bolts are not feasible under long-term dynamic traffic loads. In this respect, Maole expansion joint is designed to take the lead in separating the two functions of bearing and waterproofing, which is more conducive to the strengthening and improvement of the two functions. 2) Thoroughly waterproof One of the features of the Mauler expansion joint is that the neoprene sealing strip is effectively embedded in the groove of the edge beam, which ensures complete waterproofing. At the same time, it can be replaced on the bridge deck or repaired by vulcanization with simple tools. Under the protection of the edge beam, the sealing strip is not directly rolled by the wheel, and its V-shaped structure can play a role in removing sediment by itself. The sealing strip can not only resist tension, but also carry out lateral and vertical displacement. In contrast, the leakage of expansion joints will cause some damage to the bridge structure. Steel bearing type The steel supported expansion joint is a structure assembled with steel, which can directly bear the wheel load. This kind of expansion device was used in steel bridges before, but now it is also used in concrete bridges. There are many kinds, current situation and sizes of steel supporting expansion devices, and the steel comb type is widely used. The structure of the steel comb-type bridge expansion device is composed of a comb-type plate, a connecting piece and an anchoring system. Some steel comb-type bridge expansion devices are filled with synthetic rubber between the combs to play a waterproof role, and some use special drainage grooves to solve the drainage problem. Steel comb-type bridge expansion device is also a finger-shaped joint of steel plate, which can be divided into supporting type and cantilever type according to the supporting condition of combs. The main features of this type of expansion device are: ① All components are processed and assembled by steel, with high structural strength; (2) continuous support can be provided for the wheels, and the driving comfort is good; ③ Embedded steel members shall be used for connection with the beam body, and the connection shall be reliable; (4) strong impact and vibration resistance and good durability; ⑤ It can adapt to large horizontal displacement and can be used for large bridges. This kind of expansion device is suitable for bridges with an expansion amount of more than 40 mm, but its application range is not very wide due to its high cost. Comb plate type expansion joint Rubber plate The rubber plate type expansion device makes full use of the characteristic of low shear modulus of the rubber material, a bearing steel plate and an anchoring steel plate are arranged in the rubber body, bolt holes are arranged, and the rubber plate type expansion device is connected with the beam end into a whole through bolts. This structure depends on the shear deformation of the rubber body between the upper and lower grooves to absorb the telescopic displacement of the beam, and the steel plate is embedded in the rubber body to span the gap between the beam ends and bear the wheel load. This kind of device was used earlier in China, and there are many manufacturers in the country with different names, mainly used in the 1980s and 1990s. The rubber plate type expansion device has the advantages of simple structure, convenient installation, economy, applicability and the like. It is mainly suitable for highway bridges below Grade II with expansion amount of 30mm-60mm, and is widely used in China. This kind of expansion device has the following performance characteristics: (1) it relies on the shear deformation of the rubber body between the upper and lower steel plates to meet the structural deformation requirements. After the device is deformed, there is a certain deformation energy in the rubber body, which will have a certain constraint force on the structure; ② The load-bearing cross-seam steel plate is embedded in the rubber body. Compared with the steel structure expansion device, it has a certain buffer effect on the impact force of the wheel, effectively protects the expansion device and the beam body, and improves the driving conditions. ③ The angle steel of the expansion device effectively strengthens the end strength of the beam body. The horizontal deformation internal force of the expansion body of the rubber plate expansion device is relatively large, generally about 30-35 Nk per linear meter. The greater the deformation, the greater the horizontal force, and the greater the possibility of overall damage to the device. Therefore, when selecting the rubber plate type expansion device, it is necessary to consider the factors such as installation error and temperature error, and the selected deformation margin should not be less than 30 mm to ensure the normal use of such devices. Rubber plate type expansion joint Modular expression Modulus type bridge expansion device is composed of longitudinal beam (special-shaped steel), cross beam, displacement control box, rubber sealing belt and other components. Rubber sealing strip (belt) with V-shaped section or other section shapes is embedded in the special-shaped steel edge beam and center sill to form a telescopic sealing body. The special-shaped steel directly bears the wheel load and transfers the load to the beam, which then transfers the load to the beam body and the abutment. When the telescopic device absorbs the deformation of the beam end, the displacement control box ? Ensure that the gap between the special-shaped steel is kept uniform; the rubber sealing belt is used to prevent sundries from entering and is waterproof. 。 The modular expansion device can increase the number of middle beam steel and sealing body according to the actual expansion amount, and can form an expansion device with large displacement, which is generally used for bridges with expansion amount greater than 80 mm. From the single seam of 8 Omm to the multiple seam of 12 OOmm, there are 15 grades. The main characteristics of this type of expansion device are as follows: ① The whole expansion device is composed of special-shaped steel longitudinal beam, steel cross beam, control transmission mechanism, displacement box, sealing rubber strip and other components, and the structure is complex; ② The sealing performance is good, and the waterproof and drainage performance is good; ③ It is suitable for bridges with large expansion requirements; ④ The overall rigidity of the structure is high, and the durability is good; ⑤ The driving comfort is good. However, due to the complex structure of the expansion device, the maintenance and replacement require a wide range of professional and technical personnel, and the high cost, it is generally only used for large bridges with higher grades. Magba modulus type bridge expansion device Modulus type bridge expansion device Modulus type bridge expansion device is composed of longitudinal beam (special-shaped steel), cross beam, displacement control box, rubber sealing belt and other components. Rubber sealing strip (belt) with V-shaped section or other section shapes is embedded in the special-shaped steel edge beam and center sill to form a telescopic sealing body. The special-shaped steel directly bears the wheel load and transfers the load to the beam, which then transfers the load to the beam body and the abutment. When the telescopic device absorbs the deformation of the beam end, the displacement control box ? Ensure that the gap between the special-shaped steel is kept uniform; the rubber sealing belt is used to prevent sundries from entering and is waterproof. 。 The modular expansion device can increase the number of middle beam steel and sealing body according to the actual expansion amount, and can form an expansion device with large displacement, which is generally used for bridges with expansion amount greater than 80 mm. The main characteristics of this type of expansion device are as follows: ① The whole expansion device is composed of special-shaped steel longitudinal beam, steel cross beam, control transmission mechanism, displacement box, sealing rubber strip and other components, and the structure is complex; ② The sealing performance is good, and the waterproof and drainage performance is good; ③ It is suitable for bridges with large expansion requirements; ④ The overall rigidity of the structure is high, and the durability is good; ⑤ The driving comfort is good. However, due to the complex structure of the expansion device, the maintenance and replacement require a wide range of professional and technical personnel, and the high cost, it is generally only used for large bridges with higher grades. Type comparison Basis for setting bridge expansion joint The amount of beam expansion is the most important basis for the selection of expansion joints. Basic factors affecting the expansion amount of expansion device 1. Temperature change Temperature change is the main factor affecting the amount of bridge expansion, which can be divided into linear temperature change and nonlinear temperature change, and the linear temperature change is the dominant factor affecting the amount of bridge expansion. When the bridge structure is in a specific temperature environment, the temperature distribution inside the beam is not uniform, and the end of the beam produces angular displacement under the change of material thermal properties. For the bridge with small span (L ≤ 8m), the linear expansion coefficient is very small, so it can be ignored; for the bridge with large span, enough attention must be paid in the design. For general design, the linear expansion coefficient can be calculated according to the following table Temperature variation range and linear expansion coefficient 2. Shrinkage and creep of concrete Shrinkage and creep of concrete are the inherent properties of concrete components, and also a random phenomenon. Concrete's mix proportion, water-cement ratio, slump, retractable tape measure sewing , cement variety, temperature, relative humidity, concrete's loading age, load holding time and strength have great influence on concrete's shrinkage and creep. Shrinkage and creep shall be considered for both reinforced and prestressed concrete bridges. The creep volume is obtained by multiplying the elastic deformation of the beam under the action of prestress by the creep coefficient = 2; the shrinkage is converted by the temperature drop of 20 ℃. At the time of installation, the shrinkage and creep have developed to a certain extent, so the calculation should be based on the installation time, and the shrinkage and creep of concrete should be reduced. The reduction factor β can be selected by referring to the following table: 3. Longitudinal gradient of bridge The movable bearing in longitudinal slope bridge is usually made horizontal. When the bearing is displaced, the expansion joint not only has horizontal displacement, but also has vertical dislocation (Δd), which is equal to the horizontal displacement multiplied by the longitudinal slope tgθ. 4. Displacement of skew bridge and curved bridge When deflection (ΔL) in the direction of bearing displacement occurs in skew and curved bridges, deflection also occurs along the bridge end line and in the direction perpendicular to the bridge end line, that is, Δd = ΔL · SINα ΔS = ΔL · COSα, where α is the inclination angle and ΔL is the expansion and contraction amount. 5. Bridge deflection caused by various loads Under the action of live load and dead load, angular displacement occurs at the end of the bridge, which causes vertical, horizontal and angular displacement of the expansion device. If the beam body is relatively high, vibration will also occur. 6. Earthquake The influence of earthquake on the displacement of expansion device is complex and difficult to grasp at present, so it is generally not considered in the design. However, if there is reliable data to calculate the subsidence, rotation, horizontal movement and inclination of bridge pier and abutment caused by earthquake, it should be considered in the design. Calculation of expansion and contraction of beam A prestressed concrete beam bridge with a beam length of 40 m and a temperature variation range of -4. C ~42。 C; linear expansion coefficient α = 10 × 10-6; shrinkage strain ε = 20 × 10-5; creep coefficient φ = 2.0; shrinkage and creep reduction coefficient β = 0.6; average axial stress of prestressed concrete σp = 80kg/cm2; elastic modulus of concrete Ec = 3.4 × 105kg/cm2; installation temperature 20C. Defect and maintenance of expansion joint Failure form and cause analysis Under the condition of no overload, the recommended fatigue life of the expansion joint is 10-15 years. 1) For the filling butt type expansion device, if the angle steel falls off, the concrete on both sides is broken, the concrete on the abutment side is completely broken, the rubber belt is broken, and the pit is very deep, it can be judged that the service life is over. 2) For the seamless expansion device, if the jump is obvious, the concrete parts on both sides are broken, broken seriously, and wrinkled, its service life can be judged to be over. 3) For the embedded butt-joint expansion device, if the vehicle jumps obviously and the bridge deck pavement is seriously damaged, its service life can be judged to be over. 4) For the plate-type rubber expansion device, if the anchor bolt falls off, the rubber is aged and deformed, and the concrete cracks, its service life can be judged to be over. Seamless The main damage forms of the seamless expansion joint are as follows: obvious rutting and cracks appear on the surface of the elastic-plastic body, the surface of the elastic-plastic body produces washboard or partial falling off, the aggregate falls off partially or in large pieces, or the bridge deck cracks and gradually breaks at the joint with the bridge deck pavement Or the bridge deck pavement within the range of the expansion device is damaged. Cause analysis of damage: the material performance of the elastoplastic filler itself, such as the ability of the elastoplastic material to absorb the deformation of the beam end is insufficient, the material strength is insufficient, the quality of the binder can not meet the actual use requirements, and the construction is not in accordance with the requirements of the manufacturer; the displacement and rotation of the bridge caused by external temperature, load and other factors lead to cracking and damage of the elastomer; The structure of the expansion device itself, such as the insufficient strength of the cross-joint plate. Docking type The main damage forms are as follows: rubber strip bulges in hot weather and falls off in winter, local perforation and water leakage; concrete cracks and cracks in the anchorage area; bridge deck pavement is broken and falls off. Cause analysis of damage: it is difficult for the rubber strip to reach the ideal state during installation; the connection between the main anchoring parts and the embedded parts of the beam body is weak; in addition, the paving concrete is thin, the post-poured concrete surface is mostly lack of vibration, and there are certain problems in density and strength, resulting in easy damage to the concrete on both sides; The connection strength between the concrete in the anchorage zone and the bridge deck pavement is insufficient, and it develops from tiny cracks to local fragmentation and falling off. Steel bearing type The main damage forms of this type of expansion device are as follows: open welding of welded junction, due to process problems, individual welds are not easy to weld firmly, the whole steel plate falls off, the anchor is weak, resulting in loosening; fatigue fracture of individual steel toothed plate. Cause analysis of damage: this kind of expansion device is easy to deform during processing and use, and it is difficult to ensure the fit between the toothed plate and the backing plate. Once a gap is generated, it is very unfavorable to the stress on the connection part, causing noise and tripping. In addition, under the repeated load of day and night operation, the toothed plate will cause premature fatigue, loose fastening bolts, and the comb ruler plate will be exposed. Rubber plate The main damage forms of this type of expansion device are as follows: the rubber plate is peeled off, the embedded steel plate is exposed, falls off and breaks, the anchor bolt is sheared off and flies out of the hole, the concrete on both sides is cracked and broken, and potholes appear. Damage cause analysis: First of all, it is the reason of the structure itself (design reason). The principle of this kind of expansion device is to use the rubber shear deformation between the upper and lower grooves to meet the expansion of the beam. Steel plates are embedded in the telescopic body to bear the load across the gap of the beam end. There are anchoring steel plates on both sides, which are connected with the beam end through bolts, and are installed in blocks per meter, resulting in poor integrity. Because the horizontal frictional resistance of this type of expansion device is very large, the requirements for the anchoring system are extremely high. Secondly, the quality of products is not good, for example, the performance of rubber material, the material and reasonable arrangement of stiffening steel plate, the bonding strength between steel plate and rubber, the control of temperature and humidity in production and so on are very strict, a little quality problems often occur, such as whole plate fracture, degumming, rubber layer wear, steel plate exposure, anchor bolts. It is directly related to the mass, transverse width and stiffness difference of the rubber expansion device itself. Modular expression The main damage forms of this type of expansion device are as follows: the main middle beam components are welded open, shaking and noise occur; the expansion uniformity is poor; the sealing rubber belt is aging, falling off or jumping out, and serious water leakage occurs; the concrete on both sides of the device has cracks and pits, the bridge deck pavement is partially broken, and the anchorage system is not ideal, resulting in local or overall damage. Analysis of damage causes: firstly, most of the edge beams and center beams used for this kind of expansion device in China adopt the combined structure of steel plates or section steel welded into special-shaped parts, and the welding quality is difficult to guarantee; In addition, the method of tightly sealing the rubber belt with the pressing strip (or clip) and the screw buckle is adopted, so that the fastener is easy to rust and break, the structural integrity is poor, the electric welding workload is large, and the welding process is not up to standard, so that the welding quality is difficult to guarantee, and the welding is broken or the rubber belt falls off or even jumps out; Secondly, in the reserved notch for installing this kind of expansion device, there are not only anchor boxes, but also many anchor steel bars, including the main steel bars in the beam body and the embedded anchor steel bars, which make it difficult to pour concrete, and it is easy to cause problems such as cavities, difficult to guarantee the compactness and insufficient strength. There will be a serious problem of complete destruction of the anchorage. Major diseases 1. Disease analysis of too narrow expansion joint: the width of expansion joint is not appropriate during construction and installation. As a result, the reserved compression amount is insufficient, the expansion joint is squeezed, the internal stress is increased, the concrete of the expansion joint body is squeezed, and the pavement is damaged such as potholes. The expansion joint width has abnormal change compared with the normal joint width reserved in the design 2. Disease analysis of height difference of expansion joint: due to abutment subsidence, installation error, bearing pad stone fragmentation and other reasons, one side of the bridge is lower than the other side of the road surface, resulting in bridgehead bump. After inspection, the abutment subsidence did not cause serious damage to the substructure. At the same time, the two diseases of vehicle bumping at bridge-head and expansion joint damage are interrelated. Vehicle bumping at bridge-head causes large impact load directly near the expansion joint, resulting in expansion joint damage. 3. Analysis of blockage of expansion joint: due to the accumulation of sand, stone and other sundries, the expansion joint is easy to lose the ability of free expansion and contraction. When the temperature rises in summer, the main beam can not extend freely, and it is easy to generate thrust between the adjacent main beam or between the main beam and the abutment. In serious cases, the main beam is jacked up or the back wall of the abutment is cracked. 4. Analysis of damage to the rubber strip of the expansion joint: In addition to aging, due to the above three kinds of expansion joint diseases, it is very easy to cause cracking, damage and warping of the rubber strip in the expansion joint. 5. Analysis of damage in the anchorage zone: the concrete strength of the post-cast strip in the anchorage zone is not enough during construction, or the curing is not in place. Or there is a height difference with the bridge deck, which leads to jumping, and the frequent action of overloaded vehicles leads to damage. It is easy to cause damage to the steel structure of the expansion joint. 6. Water seepage of the expansion joint: This is a concomitant disease caused by the damage of the rubber strip or the damage of the anchorage area. Water erosion caused by water seepage is very harmful. Direct harm: water seepage acts on the following parts to cause corresponding harm. (1) The rubber of pier (abutment) bearing is aged and cracked, and the steel plate is rusted. (2) The pier (abutment) concrete and solid slab beam body are eroded and pitted, and the reinforcement is rusted and expanded. (3) Water accumulation in cavity of hollow slab beam (4) The end of steel structure beam is rusted. Indirect hazard: water erosion will spread to beams, slabs and hinge joints, and damage the upper load-bearing parts. If the bridge deck pavement is permeable, the following diseases will be aggravated. (5) The hinge joint leaks, and the hinge joint falls off seriously. (6) Hollow slab web cracks. (7) Single plate stress of bridge (such diseases of small and medium-sized hollow slab girder bridge are more serious). Tianzhuangtai Bridge, Panjin, Liaoning At 7 o'clock on the morning of June 10, 2004, Tianzhuangtai Bridge in Panjin City, Liaoning Province suddenly collapsed. The bridge broke 27 meters from the middle, three cars fell into the water, two agricultural vehicles fell into the water to escape, but fortunately no one died. The accident was caused by overloading. Long-term water seepage at the expansion joint at the end of the cantilever beam on the bridge deck leads to the decrease of the durability of the bracket and the sudden fracture of the heavy vehicle when it passes, resulting in the falling off of the hanging beam. Water seepage in the expansion joint Water seepage in the expansion joint Mortar shrinkage crack and water seepage of hollow slab beam head plate It is harmful to steel beams and hollow beams. There is water seepage in the expansion joint, and there are water marks on the hollow beam, so it is necessary to drill holes to drain water Waterproofing of expansion joints of steel structure bridges is particularly important Major diseases Other types Failure of continuous expansion joints on bridge deck Loose rubber expansion joint nut Expansion joint curing Section of Mingyangtan Bridge in Harbin after Collapse Completely out of control The expansion joint is completely replaced by asphalt concrete. Clean the expansion joint Repair and replace the rubber strip Maintenance anchorage area Integral replacement of expansion joint Expansion joint cleaning is the most important in daily maintenance, and it is often the most easily overlooked. Expansion joints are generally cleaned once a month, and the frequency of road sections prone to pollution needs to be increased. Sharp tools shall not be used during cleaning to prevent damage to the rubber strip. High pressure water gun, high strength fan and other equipment can be used. Once the rubber strip is damaged, it must be repaired or replaced Local small cracks and damages can be bonded with epoxy resin. The rubber strips with large damage and serious aging shall be replaced. When replacing, the old rubber strips shall be pulled out with a crowbar similar to tire replacement, and the new rubber strips shall be replaced in the same way. Cracks and damages in the anchorage area must be repaired immediately. The cracks in the anchorage zone can be treated with epoxy resin, and the cracks with wider width can be repaired with epoxy mortar. If the damage is serious, the damaged part shall be chiseled out to expose the reinforcement and section steel parts, rust removal shall be carried out, and steel fiber concrete or rapid concrete shall be poured for repair. Installation of bridge expansion joints Process flow Measure, mark out, cut the joint, remove the concrete and sundries, install and block the foam board between the beam joints, hoist the expansion joint of the Maole in place, adjust the plane position of the expansion joint of the Maole, adjust the elevation of the expansion joint and anchor and release the lock, do a good job of protection, pouring concrete, plastering, curing and opening traffic. Take Mauler expansion joint as an example. 1. Joint cutting and grooving: the installation of expansion joint device shall be carried out after the pavement is paved as far as possible, and the notch size shall meet the requirements for installation of expansion joint device. 2. Clean the notch: all dirt, dust and other unnecessary things must be removed. 3. Check whether the gap between the beams of the expansion joint device meets the requirements of installation temperature. If not, it must be adjusted under the guidance of the engineering and technical personnel of the manufacturer to make the gap between the beams of the expansion joint device meet the design requirements. After adjustment, press the fixture for installation. 4. Take the asphalt pavement on both sides as the elevation, place the expansion joint device in the notch, adjust the expansion joint device to make its top surface the same as the pavement elevation, and its longitudinal slope and transverse slope shall be consistent with the bridge pavement. 5. Check the position of the expansion joint device to ensure that the position of the expansion joint device in the direction of vertical joint and the direction of longitudinal joint meets the design requirements. If individual embedded reinforcement hinders the correct direction of expansion joint device at this time, it can be cut off by gas cutting. 6. Connect and weld the anchoring reinforcement on one side of the expansion joint device with the embedded reinforcement in the reserved groove at intervals, and then weld the anchoring reinforcement on the other side according to the above steps. When the expansion joint device is confirmed to be fixed, the clamp can be taken down, and then the rest of the unwelded anchoring steel bars are completely welded with the embedded steel bars, so that the expansion joint device is reliably anchored. 7. If the expansion joint device is installed in sections, the joint must be welded. The welded joint of the section steel has been prepared in the manufacturing plant. When the two adjacent joints are aligned, it can be installed. After all the beams are welded, they can be anchored according to the above steps. 8. Install the formwork at the beam end. The formwork shall be made according to the external dimensions of the expansion joint device and the gap of the reserved groove. The formwork shall be made very tight to prevent mortar from flowing into the displacement control box or into the gap at the beam end. 9. After the installed formwork is checked to be tight and seamless, the reserved groove shall be cleaned, and then the concrete (steel fiber concrete) can be poured and vibrated to be dense. The concrete shall have at least the same strength as the structural concrete at that location, and the top surface of the expansion joint device shall be kept clean during concrete pouring Allowable installation deviation of expansion joint Caution: Construction temperature and factory preset gap width The construction joint shall be protected by foam board, and the lower part of the bottom V-shaped rubber strip shall also be blocked by polyethylene foam board to prevent mortar leakage. Top flatness control Copyright statement: The source of this WeChat content is Zhulong Forum. Copyright belongs to the original author, if it involves copyright issues, please contact us, we will be the first time to negotiate copyright issues or delete the content! This article is the original author's personal opinion, which does not mean that this public number agrees with its views and is responsible for its authenticity. Return to Sohu to see more Responsible Editor:. tape-measure.com
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