In the long-term outdoor work, there are many quality hidden dangers in highway construction, so what are the common problems in highway bridge construction? Let's have a look!
1. Pile foundation: When binding the pile foundation reinforcement cage, it is required to spot weld at least 1/5 nodes between the stirrup and the main reinforcement, and all the rest shall be bound with double binding wires, and the binding head shall be pressed inward. The construction of cast-in-place pile and related inspection shall be carefully operated according to the requirements of design and specification.
Second, pier: negative deviation should be adopted for the cross-section size of pier reinforcement cage to ensure that the net protective layer thickness is above 4cm. If the protective layer is not thick enough, there will be traces on the pier until cracks appear in the stirrup position, which should be strictly guarded against. The pier maintenance work can not be ignored, and it must be covered for maintenance, or if the strength allows, loosen a joint of the pier template and pour water from the joint for maintenance.
3. Hoop: The tender documents require "including the bridge capping beam bracket, and no holes shall be drilled on the pier or reserved to support the capping beam template". The hoop can be used to support the cover beam and tie beam formwork.
4. Bottom formwork of precast beam and slab: the precast beam and slab shall adopt the shaped steel formwork, and the base shall also adopt the steel formwork. T-beam bottom plate thickness is not less than 4mm, box beam bottom plate thickness is 6 ~ 8 mm .. and the bottom plate is required to be smooth and shiny, and the edge is straight, and there can be no edging phenomenon. When welding, special attention should be paid not to burn the bottom die, and the steel plate can also be firmly bonded with adhesive. In addition, in order to ensure that the bottom die does not leak slurry, it is suggested that the bottom plate is 3 ~ 5 mm wider than each side of the side wall.
Verb (abbreviation of verb) expansion joint: When precast end beam, the influence of longitudinal slope on the upper and lower width of expansion joint should be considered. The vertical section of beam end must be set with inclination angle according to the requirements of design drawings to avoid the expansion joint being too wide or too narrow up and down. For cast-in-place box girder, benzene board with appropriate thickness can be placed between the end formwork and the back wall, and the formwork can be removed in time after reaching the formwork removal strength, so as to prevent the benzene board from long-term damage and slag loss, which is difficult to remove. In order to ensure the width of expansion joint and the thickness of protective layer, the positive deviation of web frame length should be prevented from exceeding the standard when processing and making frame blocks. In addition, the height of embedded U-bars at expansion joints should be strictly controlled. Too high or too low will bring problems to the later expansion joint installation.
Six, steel processing: steel processing and installation must be carried out in accordance with the relevant requirements of the specification and the tender documents. It is forbidden to place any filler such as fine steel bars in the lap weld of steel bars, and the welding quality must be guaranteed. Φ 32 and above steel bars can be mechanically connected after passing the inspection.
Seven, anchor plate and groove: negative moment anchor plate positioning should be accurate, tensioning groove should have a fixed template, to ensure that the size meets the requirements. At the same time, don't cut the beam-slab connection reinforcement.
Eight. Bellows: Pay special attention to the protection of bellows and strictly control the quality of bellows. When pouring concrete, corrugated pipe should be filled with steel wire or pe plastic pipe with equal diameter. Bellows shall not leak slurry, so as not to need to open the cavity due to the inability to penetrate the steel strand during tensioning.
9. Brushing of precast beam and slab: the top surface of precast beam and slab must be brushed, that is, after leveling with steel trowel or wood trowel, according to the growth of concrete strength, the surface laitance should be brushed with steel wire brush in time to expose pebbles. Diaphragm beam end and beam end can be treated with a haircutting hammer.
X. Sand and gravel washing: unqualified sand and gravel should be washed with water, and the bidding documents have special requirements for washing.
Xi。 Maintenance of concrete members: all concrete members such as beams and slabs must be fully covered and maintained by running water.
12. Lifting of beam and slab: When lifting beam and slab, measures should be taken to protect the edges and corners of beam and slab from damage. It is required to pad the film first, and then put the steel buckle angle to ensure that the bottom plate is not damaged.
13. Bearing installation: If the bottom plate of precast beam and bearing can't be closely attached, it is necessary to process and form a wedge, so that the upper and lower bearing surfaces are closely attached and the force is uniform. The sliding surface must be coated with silicone grease as required and cannot be replaced by butter or any other grease.
XIV. Pipe grouting: Before grouting, the anchor head shall be sealed with cement slurry. During grouting, the slurry outlet is required to be saturated to discharge the slurry. When the thick slurry with the same consistency as specified flows out, the slurry outlet valve is closed. When the pressure continues to reach the specified pressure of 0.5~ 1.0Mpa, the grouting is stopped. At this time, excess water will seep from the gap of the steel strand, and the reading of the pressure gauge will slowly decrease. Start the machine at any time and continue grouting to the specified pressure. This is repeated for several cycles until the water seepage stops and the pressure remains stable. At this time, the load can be held for 2 minutes to reach complete saturation, and then the grouting valve is closed to complete the grouting work.
15. Deck pavement: the pavement thickness should meet the design requirements, and the minimum value should be controlled above 8cm. In order to ensure that the position of bridge deck reinforcement meets the design requirements, the pad should be encrypted. It is not allowed to drive the tank car directly on the reinforcement plate, and it must be dusted by vehicles or chutes. The construction equipment must have at least three rollers, vibrators, flat vibrators, rolling rods and random trowels, and the top surfaces of the guide rails on both sides must be the design elevation of bridge deck pavement. The slump of concrete should be controlled at 70 ~ 90 mm, and cracks will occur on the bridge deck if the slump is too large. Bridge deck concrete must be washed and covered with dynamic water for maintenance.
Sixteen. Enlarged foundation: The bearing capacity of enlarged foundation must meet the design requirements, preferably located on bedrock.
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