With the rapid development of highway transportation, the volume of transportation and large-tonnage vehicles have increased year by year, which has put a lot of pressure on the bridge, which has reduced the health of the bridge and accelerated the speed of bridge damage. Therefore, the reinforcement of bridges has become increasingly important. Reasonable and effective reinforcement methods can help bridges solve their health problems while also improving their operating and carrying capacity.

Bridge reinforcement method

Carbon fiber CFRP sheet reinforcement method

Carbon fiber CFRP sheet has many advantages, such as light weight, high strength, easy to use, easy to stick, and not easy to rust. In addition, carbon fiber also has various excellent properties, such as easy bending, shearing, compression and impact resistance. Because of these advantages, the method of carbon fiber reinforcement is mainly suitable for the bending and shear reinforcement of reinforced bridge concrete. Especially when the reinforcement rate is low or the steel bar is seriously corroded, the pasting carbon fiber method is particularly effective, and the method is also very significant. It is also suitable for shearing, compression reinforcement, seismic ductility enhancement of concrete bridge piers and repair after earthquake damage. The bonding carbon fiber reinforcement method also has certain disadvantages. For example, when the carbon fiber sheets are subjected to a tensile force, they exhibit a linear elastic relationship until they break, which indicates that the brittleness performance is significantly different from that of steel. Therefore, when using the sticking carbon fiber reinforcement method, the carbon fiber sheet does not have ductility. Therefore, the ductility of the reinforced bridge structure is greatly restricted, and the stress redistribution is also restricted. Some precautions are required when using this method, such as controlling the storage conditions such as temperature and humidity when storing carbon fiber sheets. Therefore, when using carbon fiber sheet materials, it cannot be regarded as a substitute for steel bars, because the ductility and brittleness of carbon fiber materials are obviously different from those of steel bars. These factors must be taken into consideration when selecting carbon fiber sheets.

There are several design principles to follow when using the bonded carbon fiber reinforcement method. First, when the self-weight of the reinforced concrete structure of the bridge is too large, it cannot be completely unloaded during the reinforcement process. At this time, the secondary force must be considered. Secondly, when the reinforced bridge concrete structure has a larger scale, the empirical formula obtained in theory is likely to be inapplicable to the reinforcement of the bridge structure. At this time, the formula needs to be revised manually, such as the correction of the safety factor, etc. . Finally, in the reinforcement design, the loss of the carbon fiber sheet material caused by the impact and damage of accidents (floods, earthquakes, wind erosion, etc.) should be considered.

Crack arrest method

The crack arrest method can mostly be used together with other methods, so that it will have a better effect on the repair and reinforcement of the bridge. The crack arrest method means that if there are cracks in the bridge, drill holes along the crack propagation direction with a tool at the tip of the crack. The method of reducing crack propagation is achieved by changing the stress at the crack. This method is more commonly used in the repair and reinforcement of the steel structure of the bridge, and is widely used as an emergency measure in the reinforcement of the bridge. When strengthening the long-span bridge structure, this method is carried out on-site drilling operations in most cases. But we know that the construction conditions on the site are relatively harsh, and the location of the construction site is not necessarily flat, which has strict requirements on the skills of the workers. Therefore, before the formal construction, detailed inspection should be carried out on the bridge crack parameters, such as the length and width of the crack. If the crack is not detected or the detection accuracy is not enough, it will be difficult to grasp the position of the crack tip when drilling. If the stop hole is not exactly at the tip of the crack, it means that the stop hole does not have the function of stopping the crack. The crack will continue to expand along the crack tip, which means that the bridge has not been repaired, but will cause more damage to the bridge. Therefore, the position and size of crack arrest holes have been specified in some related parameters in bridge repair. Generally, it is stipulated that the aperture of the crack arrest hole is a thick plate, and the center of the crack arrest hole should be accurately in front of the crack propagation path. The distance between the center of the crack arrest hole and the crack tip is preferably 0.5 to 1 times the thickness of the plate. There are many ways to repair fatigue cracks, but the crack arrest method is the simplest one to implement. But this method is also one of the worst methods, for those that have not been accurately detected before construction, or even have no effect on strengthening the bridge. Although the effect of this method may be a bit inferior, it is also stronger than those that have obvious cracks but ignore them. Therefore, in the case of not affecting normal traffic, effective reinforcement and maintenance can be used as an emergency measure.

Gusset reinforcement method

The gusset reinforcement method refers to the method of installing the holed triangular steel plate span fillet welds under the bridge deck and stiffeners when the bridge deck between the two ribs of the bridge sinks, when repairing the cracks. The gusset reinforcement method is used for bridge reinforcement, because the biggest advantage of this method is that it can minimize the deformation of the bridge deck and reduce the stress amplitude between the two decks of the bridge stiffener and the stiffener. The principle of the gusset reinforcement method is to change the structure of the bridge to affect the location of the hot spot and cause it to change. This will transfer a part of the stress to the place where the force is small or not, and in the process will increase the rigidity of the bridge deck. However, the gusset reinforcement method should not be used alone. This is because the distance between the gusset panels is small, and the stress concentration at the lower and lower corners of the gusset is particularly prominent. If this method is used in the process of strengthening the bridge, it is best to cover the underside of the crack with steel plates. This will be more beneficial to the future use and life of the bridge than using gussets alone. When welding, it should be noted that the two links between the gusset plate and the test piece are welded. Therefore, it is necessary to ensure that the corner weld of the gusset plate does not appear to be broken when welding, and it needs to be welded continuously. .

Incremental push method to adjust the horizontal displacement of the arch foot of the arch bridge

The push method is widely used in bridges where the abutment has horizontal displacement. The horizontal displacement of the abutment will bring great harm. Because the displacement of the bridge will cause the positive bending moment of the vault section to increase, a lot of radial cracks will be generated. When such cracks are less than 0.2mm, the safety of the bridge And the impact of carrying capacity is not big. However, if there are too many radial cracks and too dense, these cracks will form hoop cracks. Compared with radial cracks, hoop cracks are more harmful and will bring great negative effects to the bridge. First, adjust the internal force of the bridge arch through the push method. After adjustment and reinforcement, the radial cracks of the original bridge will shrink or even disappear. The push method will not only reduce the radial cracks, but is also applicable to the case of the dome sinking. It will improve the subsidence to varying degrees, and the bending stiffness of the arch will also be improved after the push process. The biggest advantage is that in the process of construction and reinforcement, it will basically not have any impact on the navigation under the bridge, and the time interval for the interruption of the traffic on the bridge can be very short. Therefore, it will not affect the flow of water and land for a long time, which is another feature that distinguishes it from other methods. In summary, the jacking method is a reinforcement method that is easy to operate, economical and effective, and can work in a short time.