Structural form and construction technology of railway bridges
- What are the common structural forms of railway bridges? What are their characteristics?
Girder bridges have a simple structure and clear force - bearing. The girder body bears the vertical load. For example, simply - supported girder bridges are convenient for construction and are often used for medium - and small - span bridges. Continuous girder bridges have good integrity and smooth driving, and are suitable for larger - span bridges. Arch bridges mainly rely on the compression of the arch ring to bear the load, with a large spanning capacity and beautiful appearance. Stone arch bridges have a long history, and concrete arch bridges and steel arch bridges are widely used in modern railways. Cable - stayed bridges pull the main girder on the bridge tower through stay cables. The main girder is like a continuous beam with multiple - point elastic supports, with a strong spanning capacity and unique shape, often used for large - span bridges. Suspension bridges use the suspension cable as the main load - bearing structure, with the largest spanning capacity, and can adapt to complex terrains, but the structure is complex and the cost is high, often used for extra - large - span bridges.
- What are the construction methods of railway bridge foundations? What geological conditions are they suitable for respectively?
Open - cut foundation directly excavates the foundation pit on the ground and then pours the foundation. It is suitable for the situation where the shallow soil quality is good and the groundwater level is low. Pile foundation includes driven piles, bored piles, etc. Driven piles are driven into the soil by methods such as hammering and vibration, and are suitable for soft soil foundations, sandy soil foundations, etc. Bored piles are formed by drilling holes on - site and then pouring concrete, and have strong adaptability to various geological conditions, especially in complex geological conditions. Caisson foundation sinks the pre - fabricated wellbore to the design elevation, and then pours the bottom - sealing concrete and fills the well. It is suitable for the situation where the upper load is large and the shallow geological conditions are poor, and is widely used in deep water, thick overburden and other conditions.
- What are the monitoring key points in the construction process of railway bridges?
Construction survey monitoring ensures the accurate position and elevation of each part of the bridge. High - precision surveying instruments are used and reviewed regularly. Concrete quality monitoring strictly controls from raw material inspection, mix - proportion design to concrete pouring and curing to ensure the strength and durability of concrete. Prestressing construction monitoring real - time monitors parameters such as the tension stress and elongation of prestressing tendons to ensure the accurate application of prestress. Bridge deformation monitoring observes the settlement, displacement, deflection, etc. of the bridge during the construction process, and promptly discovers abnormalities and adjusts the construction process. Structural stress monitoring monitors the stress changes of the structure during the construction process by arranging stress sensors at key parts to prevent structural damage caused by stress exceeding the limit.
- What are the differences in design and construction between high - speed railway bridges and ordinary railway bridges?
In terms of design, high - speed railway bridges require higher stiffness to reduce the impact of bridge deformation on the operation of high - speed trains, and their beam cross - section sizes are usually larger. The dynamic performance requirements of the structure are strict, and vehicle - bridge coupling vibration analysis is required to ensure the comfort and safety of trains running at high speed. The long - term settlement control in foundation design is more strict to ensure the smoothness of the track. In terms of construction, the construction accuracy requirements of high - speed railway bridges are extremely high. For example, the error control of beam prefabrication and erection is within the millimeter level. The control of environmental impacts during the construction process is stricter, reducing construction vibration, noise and other interferences to the surrounding environment. A large number of advanced construction technologies and equipment are used, such as movable formwork, segmental assembly, etc., to improve construction efficiency and quality.
- What does the maintenance and repair of railway bridges include?
Daily inspection regularly conducts visual inspections of the structural components and auxiliary facilities of the bridge, including beam cracks, scouring of pier and abutment foundations, bearing deformation, etc. Structural detection uses non - destructive testing technologies, such as ultrasonic testing and rebound testing, to detect concrete strength, steel bar corrosion, etc. Regularly conduct load tests on the bridge to evaluate the bearing capacity of the bridge. Maintenance measures clean and anti - corrode the bridge surface, and promptly repair concrete defects. Lubricate and adjust the bearings to ensure their normal operation. Clean and repair the expansion joints to ensure their normal expansion and contraction function. When the bridge has diseases or damages that affect the structural safety, take corresponding reinforcement measures, such as pasting steel plates, external prestress reinforcement, etc., to restore the bearing capacity and service performance of the bridge.