Steel structure bridge is a form of bridge, which means that the main load-bearing part of the superstructure of a bridge is made of steel. Steel structure bridge is the same as bridge, which is the air road across rivers, lakes and marine obstacles, Among them, the long-span bridges are mostly prestressed steel concrete bridges and steel structure bridges. The structure of the steel structure bridge is composed of the main bridge along its longitudinal direction. The span between piers is called span. The main bridge crossing the main navigation hole section is called main span, and the span is side span. The main materials used for steel structure bridges are steel plate, section steel and high strength, The main types of steel beams are rib beam, box beam, truss beam and composite beam;
1) Material selection. Before processing, the factory certificate, quality guarantee, batch number, chemical composition and mechanical properties of the materials entering the site shall be accepted one by one, and the sampling test shall be carried out according to the current relevant national standards and construction specifications. The materials used for structural welding can only be used after passing the test, Moreover, it must be compatible with the welded steel members;
2) Weld welding. The main welds, especially the butt welds or the welds required by the design, shall be inspected in time after welding. The inspection methods of welds mainly include appearance inspection and inspection instrument inspection, and the inspection methods of instruments include ultrasonic flaw detection, X-ray flaw detection, magnetic particle flaw detection, etc The self inspection of the construction unit and the sampling inspection of the construction unit shall be strictly controlled. The quality of the welding seam shall be inspected to see if it meets the design requirements. The unqualified welding seam shall be reworked until it is qualified;
3) Rust removal and corrosion protection of bridge body. Moisture and condensation water are not allowed on the surface of steel when painting; The surface of steel and concrete is not allowed to have loose objects, dust, oil and other attachments; Phenolic, alkyd and oil-based paints are not allowed to be applied under the conditions of temperature below 5 ℃ and relative humidity above 80%; Inorganic zinc rich and epoxy asphalt paint is not allowed to be applied under the conditions of air temperature below 10 ℃ and relative humidity above 80%. The time interval between steel surface cleaning and painting shall not exceed 4H for outdoor operation and 80% for indoor operation. When spraying zinc and aluminum coating, it shall be carried out within 4h after steel surface cleaning, and the time interval between first coat and middle coat painting shall be applied within 2h after thermal spraying, When the current coating film is not completely dry, the second coating shall not be applied, but the interval time shall not exceed 7 days. When the interval time exceeds 7 days, the coating surface shall be polished to a fine rough surface with fine sandpaper. In the coating operation, no matter mechanical spraying or manual brushing, the coating shall have corresponding construction viscosity. Therefore, an appropriate amount of diluent can be added to the coating. The type and quantity of diluent shall be suitable for the construction method and coating system, Can not be used indiscriminately, the amount of appropriate; For the prepared coating, it is not allowed to add diluent at the construction site.
