The construction of port projects has achieved world-renowned achievements along with the process of my country's reform and liberalization. As a key node of internal road connections, port bridges play a vital role in the normal operation of ports. With the development of economy and society, the traffic flow of bridges in port areas continues to increase, and various forms of overloading are commonplace. Early designed bridges have low safety reserves and more and more bridges need to be reinforced. This article summarizes the previous experience of bridge reinforcement in port areas, and summarizes several commonly used methods of bridge reinforcement in port areas and the points that should be paid attention to.
The method of increasing cross-section is often used to strengthen piers and pier columns in bridges, as shown in Figure 1.1. This method is generally to implant steel bars around the piers and pier columns, and then increase the main reinforcement, and after pouring the concrete, make them integrated with the original piers or pier columns.
After increasing the component section, the constant load of the component is also increased, so that the reinforced structure becomes a composite component. The key to the composite component is the combination of new and old concrete to be firm and reliable. In addition to the need to re-calculate the bearing capacity limit state and serviceability limit state of the laminated members, it is also necessary to review the bearing capacity of the foundation. The principle of this reinforcement method is relatively simple, the construction process is relatively easy, the force is reliable, and the reinforcement cost is also low. However, this reinforcement method also has shortcomings that cannot be ignored, such as a long maintenance period, which may affect the traffic flow in the early stage of reinforcement, and the clearance under the bridge will be limited to a certain extent. These unfavorable factors also affect the general applicability of this reinforcement method.
The sticking steel plate reinforcement method uses structural glue and anchor bolts to fix the steel plate at the weak position of the structure, so that the original structure and the steel plate become a whole to bear the force. This reinforcement method is often used to reinforce the main girder of a bridge. As shown in Figure 2.1, the sticking steel plate reinforcement method has the following advantages:
(1) It can not only effectively improve the bearing capacity of the beam, but also improve the later deformation capacity of the bridge.
(2) Compared with the increasing section reinforcement method, its influence on the lower space of the reinforced bridge can be ignored.
(3) The construction period is short, the material consumption is low, and the economic benefits are obvious. It is currently the most commonly used reinforcement method.
Due to the particularity of the environment in the port area, when using this reinforcement method, special anti-corrosion measures on the surface of the steel plate should be taken, and regular maintenance in the later period will increase additional maintenance costs. Since the anchor bolts must be drilled into the bridge structure, this will inevitably cause certain damage to the original structure. When drilling, it is recommended to select a place with less steel distribution.
The sticking carbon fiber sheet reinforcement method is to paste the carbon fiber sheet on the surface of the structure through gluing to make it a composite body, as shown in Figure 3.1. The tensile strength of carbon fiber sheet is about 8 times that of ordinary steel. Through the interaction between the two, the bending bearing capacity of the reinforced structure can be significantly improved. This reinforcement method has a simple construction process, a short period, and no damage to the original structure.
Although the tensile strength of the pasted carbon fiber cloth is very high, its shear strength is particularly low. This reinforcement method is not very suitable for structures that need to improve the shear resistance. Due to the high tensile strength of carbon fiber, when the general structure is broken, its strength utilization rate is less than 30%. The high price of carbon fiber also limits the development of this reinforcement method.
External prestress reinforcement is the addition of high-strength steel wire bundles, steel strands, etc., through the active external force of prestress, so that the reverse bending moment generated by the prestress offsets the internal force of part of the load. Thereby improving the bearing capacity of the original structure, and has a good control effect on the crack deflection. This reinforcement method is widely used in the field of bridge and building reinforcement.
Changing the reinforcement method of the structural system improves the bearing capacity of the reinforced structure by changing the stress state of the original structure. The following methods are mainly suitable for the reinforcement of bridges in port areas.
Conclusion
As the old bridge reaches a certain service life, more and more projects need to be reinforced. Port bridges and ordinary highway municipal bridges should pay attention to their differences during reinforcement. The selection of reinforcement methods should be based on comprehensive analysis of various aspects such as bridge evaluation categories, defects, and economic benefits. Bridge reinforcement will be an emerging discipline with huge potential in the future. It also needs the continuous improvement and summary of engineering and technical personnel. With the continuous development of engineering technology, the future bridge reinforcement technology will inevitably continue to flourish.
Language: English
