Ten Ways of Reinforcing Bridges

What Is Bridge Reinforcement

Bridge reinforcement is to improve the load-bearing capacity and performance of components and even the entire structure through certain measures to meet new requirements. That is to say, we need to deal with the situation that the bridge cannot meet the continued use.

Reasons for bridge reinforcement include poor durability and aging of the bridge, improper design or poor construction quality. After bridge reinforcement, the service life of the bridge can be extended, and a small amount of capital investment can be used to enable the bridge to meet the needs of traffic volume. It can also ease the concentration of bridge investment and prevent and avoid the loss of people and property caused by bridge collapse.

The Purpose and Requirements of Bridge Reinforcement

一、The Purpose of Bridge Reinforcement

1. Ensure the safety, integrity, applicability and durability of bridge projects.

2. Improve the passing capacity and carrying capacity of the original bridge.

二、Basic Requirements for Bridge Reinforcement

1. Understand the structural condition of the bridge. Improve basic information. Provide necessary conditions for reinforcement.

2. Economic costs. Generally speaking, the reinforcement cost is about 10% to 30% of the new construction cost. That is, reinforcement should be given priority.

3. No disruption to traffic or minimization of disruption to traffic

4. The discovered defects must be reinforced once and for all without leaving any future troubles; the reinforcement design should be carried out in accordance with specifications.

5. Damage to the original bridge structure should be minimized as much as possible

6. The technology is reliable, durable and applicable, and easy to maintain.

Ten Ways To Strengthen Bridges

Method One: Enlarged Cross-Section Reinforcement Method

Increased section method is also known as the outsourcing concrete reinforcement method. Its definition refers to the use of increasing the cross-section area of concrete structures or structures, the purpose is to improve its load-bearing capacity and meet the normal use of an effective reinforcement method. When the reinforced concrete is subjected to the compression zone of the bending member and the concrete cast-in-place layer is added, the effective height of the section can be increased, the section area can be expanded, and the normal section bending resistance of the member can be finally improved, and the oblique section also has the shear resistance and section stiffness, which plays the role of strengthening and reinforcing. This method of reinforcement can be widely used in concrete structure beams, plates, columns and other components, as well as general structure reinforcement. Under normal conditions, the main method is to thicken the bridge panel or increase the beam rib width of the main beam.

Method Two:External Prestressed Reinforcement Method

The external prestressed reinforcement method is suitable for the structure under high stress, especially for the reinforcement of large structures. It can improve the bearing capacity, stiffness and crack resistance, and occupy a small space of the bridge after reinforcement. The strengthening principle of external prestress method is that the construction party sets prestressed materials at the initial tension area of the lower edge of the beam, and generates eccentric prestress on the beam body through tension, so that the beam body overarches, offsets part of the self-weight stress, thus reducing the structural deformation and crack width, and improves the structural stress. Improve the bearing capacity, stiffness and crack resistance of the bridge and occupy a small space after reinforcement. However, the disadvantages of this method are that the local cabling effect is obvious, the anchor head is increased, the joint structure is complicated, and the construction surface requirements are high, so the overall economic benefit of the reinforced steel truss is not high. The method is mainly applicable to the structure under high stress, or to the reinforcement of large structures, or to the control of beam cracks and reinforcement fatigue stress amplitude.

Method Three :System Transformation And Reinforcement Method

System conversion method is a reinforcement method to reduce the internal stress of the beam and improve the bearing capacity of the bridge structure system. It is an effective method to convert passive reinforcement into active reinforcement. Changing the structural system reinforcement method means that additional components can be added or technical transformation can be carried out to achieve fundamental changes in the stress system and stress condition of the bridge, and can play a role in reducing the stress of its load-bearing components, and ultimately achieve the purpose of improving the bearing capacity. At present, the most commonly used system conversion methods are: beam bridge to beam arch combination system method, adding auxiliary pier method, multi-span simply-supported beams to simple supported first and continuous bridge floor system method.

Method Four:Pasted Steel Plate Reinforcement Method

Paste steel plate reinforcement method is applied to paste steel plate reinforcement. The binder and anchor bolt are used and the steel plate is attached to the tensile surface or other weak parts of the concrete structure to form a whole steel plate and reinforced concrete structure, and finally realize the purpose of improving the bearing capacity of the structure. However, the pasted steel plate reinforcement method has its own shortcomings, such as the necessary surface protection work needs to be carried out after the pasted steel plate reinforcement, such as epoxy mortar or cement mortar protective layer, the degree of rust of the steel plate is difficult to estimate, which reduces the reliability of the reinforced components and increases the later maintenance cost of the reinforced bridge. However, this method is often used in the reinforcement of Bridges, and this method still shows some good advantages. For example, the construction is simple, the technology is reliable, the short-term reinforcement effect is good and the process is mature and basically does not change the size of the original structure.

Method Five:Composite Reinforcement Technology (FRP)

It is composed of fiber and mesh resin. At present, the commonly used composite materials are E-glass fiber, carbon fiber and aromatic Lun fiber, of which carbon fiber (CFRP) material is the most widely used. The technology of using carbon fiber cloth to strengthen and repair Bridges and building structures is a new kind of structural reinforcement technology, which is based on resin cementing material as the matrix, the carbon fiber is pasted and solidified on the surface of concrete structures, and the high strength and high elastic modulus of carbon fiber are used to reinforce and reinforce concrete structures and improve the structural stress condition.

Method Six:Wire Reinforcement Method

Wire winding reinforcement method is a direct reinforcement method to wind annealed steel wire on the surface of the reinforced member to restrain the concrete of the reinforced compression member, so as to improve its bearing capacity and ductility. This method has the following advantages: first, it can improve the inclined section bearing capacity of reinforced concrete members; The second is to improve the normal section bearing capacity of axial compression members.

Method Seven: SRAP Reinforcement Method

The SRAP reinforcement method is a new bridge reinforcement method that introduces the concept of prestress. It utilizes the high-strength characteristics of SR reinforced materials and the anti-corrosion, waterproof, and strong adhesion characteristics of AP resin mortar. It uses a special method to apply prestress to the SR high-strength materials to achieve the reinforcement of the bridge. To apply prestress, anchor the expansion bolts at both ends of the beam bottom. The two ends of the soft steel wire are fixed on the expansion bolts with spiral buckles. The prestress is applied by tightening the spiral buckle with the thread in the opposite direction.

Method Eight: Bridge Deck Reinforcement Layer Reinforcement Method

To increase the effective height of the main beam and improve the lateral load distribution ability of the bridge, the bearing capacity of the single beam or the overall bearing capacity of the bridge structure can be improved.

Method Nine: Anchorage Shotcrete Reinforcement Method

The reinforcement method transformed from tunnel construction is mainly used to reinforce and repair concrete beams with insufficient shear strength due to small fulcrum cross-section sizes.

Method Ten: Add Horizontal Connection Reinforcement Method

Increasing horizontal connections is also a reinforcement method that has been used more frequently in recent years. This method is a reinforcement method that improves the lateral load distribution pattern of the superstructure by adding lateral connections to the bridge, thereby improving the overall load-bearing capacity of the structure. It is generally used for T-shaped cross-section and I-shaped cross-section beam bridges with no or few internal beams. In engineering, cast-in-place concrete beams or steel beams are often added between adjacent main beams to improve the lateral bending stiffness. The disadvantage of this technology is that it will cause a certain degree of damage to the original structure. For areas or components with complex reinforcement, it is not advisable to use this method to reinforce the design to avoid increasing safety risks after reinforcement.

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