The design method of bridge reinforcement is very important. Only by starting with the details can we better solve the actual problem, and only by combining the actual situation can we solve the problem fundamentally. Zhongda Consulting will explain to you the methods of bridge reinforcement design.
1 Steps and principles of bridge reinforcement
The reinforcement of bridge projects generally refers to the structural adjustment of existing bridges or the repair of some problems that threaten the operational reliability of the bridge. The process of eliminating diseases. During the operation of bridges, diseases caused by various reasons will inevitably occur. How to carry out reasonable reinforcement design and treatment has become a key issue in bridge maintenance work. In practice, engineers have summarized the basic principles in the bridge reinforcement design process:
(1) Bridges whose structures have been damaged and cannot meet normal operating standards must be reinforced accordingly. The formulation of specific reinforcement methods and measures must be combined with the relevant provisions of our country's laws and regulations. Usually, depending on the scope, bridge reinforcement can be divided into overall reinforcement and partial reinforcement;
(2) When implementing bridge reinforcement Before designing, it is necessary to conduct a careful economic benefit analysis of the project, compare the economic costs and output of the bridge reconstruction work from the three aspects of maintenance, reinforcement and reconstruction, and choose the most scientific and reasonable operation plan;
(3) In the process of designing the reinforcement scheme, the impact on other related projects, such as connected highway projects, must be fully considered;
(4) When strengthening large-scale bridge projects, Multiple alternative construction plans should be designed, and comparative analysis should be conducted from various aspects such as economic benefits and engineering effects to determine the best reinforcement plan;
(5) In the process of strengthening the bridge , the original structure of the bridge should be maintained as much as possible without fundamental modifications to the existing structure;
(6) During the reinforcement design process, the reinforcement plan should be discussed with the bridge construction party, Ensure that the determined reinforcement plan does not cause adverse effects on the original structure of the bridge;
(7) The current use status and various diseases of the bridge should be fully considered in the bridge reinforcement design;
(8) Bridge During the implementation of reinforcement, it should be carried out as far as possible without hindering the normal operation of the bridge;
(9) If the reinforcement construction encounters various unexpected situations, such as unknown defects in the engineering structure, etc., the construction personnel Construction should be stopped immediately and the construction plan will be re-agreed with the designer and supervisor before starting;
(10) Safety protection measures should be taken to ensure the dual safety of construction personnel and the bridge structure.
2 Specific methods of bridge reinforcement
Bridge architecture is an auxiliary measure based on the existing structural form of the bridge, aiming to improve the safety and stability of the bridge operation. However, for bridges with different structural forms and operating conditions, different reinforcement methods should be adopted to obtain better reinforcement effects. Below, the author will briefly analyze several common bridge reinforcement methods.
2.1 Bridge superstructure reinforcement method
(1) External prestressed reinforcement method. This is what we usually call the external cable reinforcement method. The basic principle of this method is to adjust the original concrete beam structure in the bridge project by adding external prestressed cables to the bridge, thereby changing its stress situation. . In the process of reinforcement using this method, the selection of prestressed materials is very important, because the strength and toughness characteristics of the prestressed materials will be directly reflected in the process of pulling the bridge. Prestressed materials with insufficient strength are It is impossible to make the bridge arch and improve its structural stress condition. This method is often used in temporary reinforcement of bridges because of its relatively simple operation and obvious effect.
(2) System conversion and reinforcement method. The basic principle of this method is to achieve partial or overall structural transformation of existing bridges. The system conversion process generally involves the addition or deletion of various bridge accessories, as well as the improvement of the existing bridge technical level. Adjustment. The most significant feature of this reinforcement method is that it can greatly improve the prestress and bearing capacity of the bridge, and can reduce the deflection in the original structure.
(3) Increase the cross-section or add local component method. As the name suggests, the main effect of this reinforcement method is achieved through the area modification of some components of the bridge.
In the process of bridge reinforcement, the overall stability of the bridge is enhanced by changing the basic characteristics of each concrete component, such as cross-sectional area, stiffness, and bearing capacity. When this method is used to strengthen the bridge structure, it is often accompanied by the widening and reconstruction of the main beam body of the bridge, and the materials consumed are mainly steel bars and concrete.
(4) Steel plate reinforcement method. This method is mainly achieved by reinforcing the concrete components of the bridge with steel plates, that is, adding or bonding steel plates with a certain hardness and strength to the weak parts of the bridge structure, thereby improving its overall bearing capacity. form. In practice, this reinforcement method is mainly used to reinforce the reinforced concrete and anchor bolts of bridges. Due to the low stiffness of the anchor bolts, during the specific construction process, the thickness of the steel plate can be appropriately increased according to the engineering conditions. The steel plate fixed on the surface of the tensioned concrete can increase the bending stiffness of the concrete structure, reduce the deflection of the structure, and limit the development of cracks. The main advantage and feature of the bonded steel plate reinforcement method in practical application is that its construction is simple and fast, and it can complete the reinforcement of the bridge structure without changing the original bridge structure. However, its shortcomings are also quite obvious, that is, it cannot achieve a relatively long-lasting reinforcement effect.
(5) Carbon fiber and composite fiber material reinforcement method. This method is suitable for the reinforcement of beams, plates and concrete compression columns. Carbon and composite fibers have excellent physical and mechanical properties such as high strength, light weight, corrosion resistance and fatigue resistance, and are ideal materials for reinforcing old bridges. The performance of the bonding material in the carbon and composite fiber reinforcement method is the key to ensuring that carbon fiber and concrete work together, and it is also the weak link in the force transmission path of the two. Therefore, the bonding material should have sufficient stiffness and strength to ensure that carbon fiber and concrete work together. The transfer of shear force between composite fiber and concrete should also have sufficient toughness to prevent brittle bond failure due to concrete cracking.
(6) Bridge deck reinforcement method. The bridge deck reinforcement method is to add a layer of reinforced concrete on the top of the beam to form an integral part with the original main beam, thereby increasing the effective height and compression section of the main beam and increasing the overall stiffness of the bridge deck. A common and effective method to improve the load-bearing capacity of bridges.
2.2 Reinforcement of bridge substructure piers and foundations
Some reinforcement methods for bridge piers and abutments are similar to those of the upper structure. For example, the cap beam can be externally prestressed, enlarged in cross-section, Reinforcement by pasting steel plates or fiber materials; pier columns can be reinforced by pouring concrete into steel casings, enlarging the cross-section, pasting steel plates or fiber materials; the platform body can be reinforced by outsourcing reinforced concrete hoops, adding auxiliary retaining walls, and frame beams Reinforcement methods such as adding anchor rods and filling soil after replacing the platform are all intended to increase the stiffness of the pier, improve the bending, compression and shear resistance of the pier, and reduce the stress on the pier.
The bridge foundation can be reinforced by expanding the bottom area of ??the foundation. If the erosion of the foundation is too large, riprap, masonry, and gabions can be used for protection, or a diversion dam can be installed upstream and a sand retaining dam can be installed downstream. Dam etc.
(1) Reinforcement method by expanding the bottom area of ??the foundation. The reinforcement method of enlarging the base area of ??the bridge foundation is called the expanded foundation reinforcement method. This method is suitable for situations where the foundation bearing capacity is insufficient or the foundation is too shallow, and the pier is a rigid entity or foundation of masonry or concrete. When the structure foundation has large uneven settlement and the foundation soil is relatively solid, the expanded foundation method can be used for reinforcement. For the problem of insufficient foundation bearing capacity at the bottom of the expanded foundation, a certain number of piles can be driven under the expanded foundation to improve the foundation bearing capacity. The parameters of the piles are selected based on the calculation of foundation deformation. Its construction is relatively simple, but its disadvantage is that it must integrate the new and old foundations to bear the upper load, so the reinforcement cost is high, and the reinforcement effect is not easy to control.
(2) High-pressure jet grouting reinforcement method. High-pressure jet grouting is to first use a drill to drill a grouting pipe with a nozzle into a predetermined position in the soil layer, rotate it and lift it at a certain speed, and at the same time inject slurry or water from the nozzle in the form of a high-pressure flow to cause impact damage. The high-pressure flow cuts and pulverizes the soil layer and disperses it into particles. Part of it is brought out of the borehole by the slurry and water, and the other part is stirred and mixed with the slurry. As the slurry solidifies, the composition has a certain strength and impermeability. A method of reinforcing the foundation by using a strong consolidating body. The jet grouting reinforcement method has a wide range of uses. The quality of the reinforced foundation is reliable and the effect is good. The cost is low, the reinforcement effect is obvious, and the construction is convenient. It has gradually become one of the commonly used methods for treating bridge pier foundations in my country.
3 Conclusion
The reinforcement of bridges is a new technology that has attracted much attention today. This article only explains the methods of bridge reinforcement. In the actual reinforcement design, it should be based on the bridge structure type, A reasonable reinforcement plan should be selected based on the bridge's topography, hydrology, natural conditions, expected reinforcement effects and functions, existing construction technology, amount of capital investment, etc. It is also necessary to conduct detailed design calculations while ensuring structural requirements to ensure The reconstruction work of the dangerous old bridge is scientific, reasonable and economically safe.
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