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Lingqiao comprehensive overhaul to stay original 2013-11-08


Lingqiao has been plagued by war damage, environmental erosion, and ship impact. After a serious collision accident in 2011, Lingqiao was assessed as a dangerous bridge and needed major repairs. The large revision has been in operation for about one month, and is currently in the stage of trestle erection and door sling installation, which is equivalent to the preparation work before the operation. After the operation, Lingqiao will remove a sickness and continue to serve the people of Ningbo safely and healthily. Then, how will the bridge doctors “treat the disease” to Lingqiao in accordance with the principle of “repairing the old and repairing the land”? Let us tell you step by step. The staff is testing the Lingqiao. Step 1: Take the facility trestle and gantry crane ◎ Difficulty: ★★ The trestle erection and the gantry crane installation are equivalent to preparing the operating table before the operation, and preparing the construction platform for the next disassembly and installation. This step is not technically difficult, but due to the complexity of the working waters, the heavy shipping, and the low clearance of the navigation under the bridge, after the completion of the trestle bridge, the narrow tunnel of water formed by the Lingqiao and the bridge will be “tunneled”. Therefore, the safety risk is high. In order to ensure the safety of water operations and navigation, a warning point and a to-be-restricted point were set up in the upper and lower reaches of Lingqiao, and a water safety warning system was established. During the overhaul, the passing vessels were required to conduct orderly navigation in the operation area as required. Step 2: Demolition of the deck asphalt and installation of the rib cross braces ◎ Difficulty: ★ The conventional construction method is adopted for the removal of the asphalt concrete bridge deck and ancillary facilities. At the same time, the temporary arch ribs are installed to remove the hangers and arches for the next step. Rib lateral connection and bridge gantry preparation. This step is relatively simple, the technical content is not high, can only be regarded as warm-up, and the subsequent bridge deck and boom removal is considered a formal treatment. Step 3: Demolition of the deck system and the boom ◎ Difficulty: ★★★ The Lingqiao bridge deck system is a structure that directly bears the load of the vehicle, including the bridge deck structure, the old longitudinal beam system, the lower flat slanting bar and the bridge line. Among them, the bridge deck is an open-rib rib orthographic plate used in the overhaul in 1994. At present, the disease of the bridge deck system is more serious. The bridge deck disease is like the “skeletal fracture” of the human “five features” bone. In the test, a large number of welds are found to be welded, and there are many longitudinal cracks on the top plate. Deformation, bending and twisting, like the impact of the body's ribs on the "injury." This overhaul will replace the closed rib orthotropic plates with better mechanical properties, repair and strengthen the twisted longitudinal beams, and replace the sidewalk brackets on both sides to improve the clearance under the bridge. The main cause of the boom is local corrosion and cracks. It is like a human limb that has been traumatized. It will be partially strengthened and the war history mark on the boom will be preserved to avoid damage to its cultural relics. Before these components are replaced and reinforced, they must be dismantled first. The order of removal is: first remove the bridge deck structure - remove the old longitudinal beam - remove the lower flat slanting bar - remove the tie beam - remove the old beam - remove the hoist Rod. When dismantling, the oxygen cutting method is basically used for block cutting to meet the lifting and transportation requirements. When cutting, in order to protect the original steel components, the block-cutting scheme will be done. When cutting, semi-automatic and manual cutting should be used as much as possible to avoid damage to the steel components to be retained. The old longitudinal beams are connected by rivets. The old longitudinal beams are used after correction. Therefore, when dismantling, the construction personnel must remove the connecting rivets, and do not cut them at will, and carefully prevent the retaining holes from being damaged. Step 4: Construction platform and arch rib support frame installation ◎ Difficulty: ★★★ Lingqiao bridge has a narrow position at both ends, but the maintenance principle requires local maintenance and requires a large space. In order to solve this contradiction, the engineering maintenance personnel thought of a good way to rebuild a construction platform as the construction site at the original bridge. After the construction platform is installed, the arch rib support frame is installed on the construction platform for converting the self-heavy load of the arch rib structure to prepare for the removal of the arch rib. Step 5: Demolition and maintenance of the rib ◎ Difficulty: ★★★★★ The arch rib is the bearing frame of the Lingqiao. It is found that the upstream side is continuously skewed, the internal corrosion of the steel structure is serious, and the thickness of the arch is nearly 1mm. Rib disease is like the internal injury of the human spine and is gradually increasing. In order to cure the increasingly serious "spine disease" of Lingqiao, it is necessary to dismantle the arch ribs in sections and repair them in situ. In order not to change its cross-sectional shape and retain its cultural relic value, the designer has ingenuity and is reinforced by the method of lining the steel plate in the arch rib. The reinforcement of the inner lining steel plate has extremely high requirements on the construction process. Lingqiao has been running for nearly 80 years, during which it has undergone many maintenance, its stress state has been difficult to measure; plus the internal space of the arch rib is small, the operation space is very limited; and the most heavy piece of the inner lining steel plate is about 2.3t, the new board The rivet connection is used between the piece and the boss piece, the rivet hole group is dense, the node area is particularly complicated, and the matching of new and old components is very difficult. The construction personnel have come up with many "coups" based on technical difficulties and previous construction experience: carefully measure the original riveting holes, carefully draw tens of thousands of riveting holes and detailed components, and record their dimensional structure and position. And the metric conversion of the inch units used in the original design of Lingqiao, and accurate to 0.01mm; then, according to the original riveting position, the new board is drilled and processed, and the fitting error is strictly controlled to ensure accurate installation. recovery. Step 6: Detection of the original structural members of Lingqiao ◎ Difficulty: ★★★★ Lingqiao is a provincial-level cultural relic, and it is also an important traffic artery to protect the cultural heritage value of Lingqiao and restore its traffic capacity. This overhaul will try to preserve the original components of the Lingqiao, and only replace the components that cannot meet the requirements for use. When the steel members were built in 1936, they experienced years of environmental erosion and heavy load. They have already produced metal fatigue. The surface and interior of the steel structure have different degrees of corrosion and cracks, as well as the original construction defects and expansion cracks of the rivets. What is the disease damage of these components? It requires engineers to make accurate judgments through high-tech testing methods. In order to accurately determine the performance of the original structural members of Lingqiao, the bridge members will be tested one by one, scanned by high-tech non-destructive testing such as ultrasonic and ultrasonic phased arrays, and samples of steel members are taken for laboratory material analysis to determine the rods. The exact position and size of the internal cracks, the specific damage degree, etc., through the simulation calculation and analysis, infer how the cracks and other details of the damage under the load pressure expand and change, and finally determine whether the structural strength and remaining life can meet the Lingqiao Use requirements, in order to maintain the original steel structure of the Lingqiao by means of correction and reinforcement during the maintenance process. This step will be interspersed with the construction process for testing. Step 7: Substructure inspection and reinforcement construction ◎ Difficulty: ★★★★ The old bridge foundation of Lingqiao is pine oblique pile. Due to the lack of old basic materials, after nearly 80 years of operation, the actual situation is unknown, plus the arch The rust condition of the arch hinge is still unclear, so it is necessary to pass the inspection of the arch hinge and the foundation by the professional inspection unit to determine the current bearing capacity of the Lingqiao. If the traffic load capacity cannot be satisfied, the design will use the drill on both sides of the original abutment. The form of the bored pile is reinforced. Step 8: Structure installation after maintenance ◎ Difficulty: ★★★★★ After the repair, the structural installation sequence is basically the opposite of the removal. First install the arch ribs, then install the cross-bridge gantry to form a stable load-bearing system, and then install the boom and bridge deck system. The difficulty of the construction process is mainly reflected in the following points: 1 Since the rib width is less than 40cm and the height is 1.7m, the operation space is narrow, which greatly increases the difficulty of installation of the rib. 2 Hangers, arch ribs, and cross-links share the rivet holes. It is required that the boom and the cross-link must be installed at the same time, and the multi-members are riveted together for installation, and the technology is complicated. 3 The new bridge deck and the repaired longitudinal beam structure are transported at the factory to the bridge for lifting installation. The connection method is that the boom and the beam are interposed, and the manufacturing precision is extremely high. In order to ensure that Lingqiao “repairs the old as the old” and protects the value of its cultural relics, the steel construction will be abandoned when the steel construction is assembled, and the old-fashioned rivet connection technology at the beginning of the last century is still used, which means that the engineers can only hammer and hammer Tens of thousands of rivets on the bridge are embedded in the bridge. Before the construction, the old riveting master will lead the professional riveting workers to splicing the “warm body”. The rivet holes on the steel beam should be tested one by one with different specifications of the test rivets to ensure that the rivets can be officially installed only after they pass. When installing the rivet, it is necessary to heat the iron. The engineer first heats each steel rivet to 1000 °C. Then, when the rivet is softened, it is driven into the corresponding nail hole with a special nail. When the rivet is hammered, the force must be even, otherwise the rivet The hammer is not flat, the connection between the steel rods is easy to loose, and the overall steel truss is not stable. According to the normal riveting construction speed, the installation process of tens of thousands of rivets will take a lot of time, and the time of other processes will be counted. The construction period of dismantling and assembling the Lingqiao steel structure will be the longest in the overhaul process. Step 9: Deck Pavement Paving and Installation of Auxiliary Facilities ◎ Difficulty: ★★ After the bridge deck is installed, the bridge deck asphalt concrete and ancillary facilities will be laid and the overhaul will be completed. This maintenance will ensure that the program is safe and fast, the anti-corrosion process is advanced and reliable, and the environmental protection measures are high quality and efficient. Although it is more difficult to "treat the disease", the bridge doctor has a coup. Coup 1: Set up a closed "operating room" (factory) on the side approach road of Baizhang Road, and use the correction pedestal and the painting studio in the abutment plant to carry out the rust and anticorrosion of the arch rib, the web and the partition reinforcement. Rivet construction, etc. Coup 2: The ribs are hoisted to the pedestal by the door sling for correction, web and partition reinforcement, rivet construction, etc., which not only ensure the quality of the project and construction safety, but also prevent the pollution of the river by the rust and anti-corrosion process. You can work more and speed up the construction progress. Coup 3: The foundation reinforcement adopts the prestressed reinforcement mode to protect the old foundation while ensuring that the new and old foundations are jointly stressed. Coup 4: The use of all solid state induction heating technology to ensure the quality of hot riveting construction; at the same time special procedures for thick plate riveting, high-altitude riveting, riveting of the joint area of ​​the boom, riveting of the narrow space, riveting of the root of the rib. Coup 5: Strengthen the monitoring and monitoring of various indicators such as line shape and stress during the process of demolition of the original structure. After overhaul, Lingqiao will greatly improve the structural safety performance, effectively extend the service life, ensure the traffic capacity, and preserve the historical and cultural value of Lingqiao and preserve the attributes of cultural relics. During the “surgery” process, the old longitudinal beams, old arch ribs and old abutments under the original bridge lane will be protected to avoid damage to the components due to construction reasons. Retain the welding traces left over from the original structure during the war. Temporarily retain the original boom. Anything that can be used will be retained. The crack will be repaired and the original appearance of the bullet will be preserved during the maintenance process. The joints involved in the original structure during the repair and reinforcement process are all riveted joints in 1936, and the appearance after riveting is consistent with the original bridge. Some of the components that need to be replaced are completely processed according to the inch specifications of the original structure in 1936. The originals are imitation and the appearance is consistent with the original structure. For the partially deformed components, the mechanical deformation is used to restore the original shape and then reinstalled, and the original bridge shape is restored as much as possible. The color of the painted topcoat is the same as that before the overhaul, maintaining the current bridge width, bridge shape and line shape. As for when Lingqiao completed the maintenance project and resumed the traffic, because of the need to carry out strict inspection during the repair process of Lingqiao, and then determine whether the original structure needs to be repaired or replaced, there is more unpredictability. Therefore, everyone still needs Wait patiently.