The bridge reinforcement
Common diseases of Bridges

(1) bridge deck pavement diseases
Common bridge deck pavement diseases include asphalt concrete pavement cracking, displacement, pit slurry, car withdrawal, embrace package, etc.
(2) expansion joint disease
The common diseases of expansion joints include failure of concrete, pushing up, breaking away from bone and section steel.
(3) cracks in concrete of beam body
Concrete structure is often used in highway Bridges in China, and cracks are the most common disease of concrete structure soil structure.
Crack width to a certain extent will accelerate the location of steel corrosion, embroidery swelling may cause concrete to fall off, so that more steel exposed.
At the same time, it will reduce the stiffness of the beam body, which will seriously endanger the use of the bridge.
(4) lateral connection disease of superstructure
Common superstructure transverse contact diseases include water seepage at hinge joints of plate beam, stress on single beam, crack and failure of t-beam diaphragm plate.

Common methods of old bridge maintenance and reinforcement

Paste reinforcement method: simple construction, short cycle;
Small space occupied, do not reduce bridge clearance;
Pasting and strengthening parts, the range and strength can be set flexibly as required;
Construction may be carried out without or with little impact on traffic;
The reinforcing steel bar has good adhesion property with the structure, the steel plate plays the role of reinforcing steel bar, improves the bearing capacity and durability of the bridge;
Reinforcing steel bar processing and forming is easy, with less steel;
Reinforcing steel bar is easy to rust, it must be rust prevention treatment;
However, the quality and durability of the binder is the key factor affecting the effect of reinforcement, should be fully paid attention to, in addition, strengthening steel plate is easy to rust, must be strictly anti-rust treatment.
Strengthening method of increasing section: that is to increase the section of concrete members and increase the reinforcement, improve the bearing capacity of members and, this method can strengthen beam bridge, arch bridge.
Pasting reinforcement method: when the tensile strength of bridge structural members is insufficient and the tensile parts crack, this method can be used
Pasting steel plate reinforced method: is a series of epoxy resin adhesives to stick steel plate on the edge of the reinforced concrete structures in tension or weak areas, with thick structure form the whole common force, to improve its bending, shear capacity and poise, improving the structure of the thickness of steel bar and concrete stress state, the restriction to the further development of the cracks, so as to improve the bearing capacity and durability of bridge reinforcement method.
Pasting carbon fiber reinforcement method: the carbon fiber reinforced composite is pasted on the surface of concrete members by means of adhesive. When the structural load increases, the carbon fiber cloth is subjected to common stress due to the coordinated deformation with concrete, which improves the bearing capacity and stiffness of concrete members from the resistance, and plays a strengthening role on the members.
External prestress reinforcement method: reinforced concrete girder bridge usually includes simply supported beam, cantilever beam and continuous beam, etc., when there are structural defects, especially the lack of bearing capacity or the need to improve the load level, the bridge main stressed members need to be strengthened, can consider the use of external prestress reinforcement method.
This method is to set steel bars or steel wire bundles outside the beam body (at the bottom of the beam and on both sides of the beam) and apply prestress, so as to improve the stress state of the structure and improve the bearing capacity of the bridge.
External prestress reinforcement actually changes the stress state of the beam body's original stress system.
Different from the basic strengthening objects, the strengthening method can be divided into prestressed tie rod reinforcement and prestressed brace rod reinforcement.
There are three ways to change the reinforcement method of structural system: adding steel truss and other stiffening beam under the beam or adding bracket or piers under the simply supported beam under the composite beam or changing the continuity of simply supported piers
Adding load-bearing member reinforcement method: when the bearing capacity of the bridge cannot meet the requirements, but the beam structure is basically intact, in order to improve the load level, it can be considered to use this method, generally by adding the main beam and beam method.
External steel reinforcement method external steel reinforcement method: is in the concrete column or beam of the four corners or two corners of the package to shape steel (generally for Angle steel), a kind of internal filling binder reinforcement method.
External steel reinforcement is divided into wet and dry two methods, section steel and the original column between a certain distance, and in the process of pouring latex cement mortar, or epoxy resin binder, or epoxy mortar, so that the steel frame and the original components can work together as a whole reinforcement method is called wet external steel reinforcement method.
There is no bond between the section steel and the component or only fill the cement mortar, which can not guarantee the effective transfer of the combined surface shear force reinforcement method is called dry type external steel reinforcement method.
The external steel reinforcement method is applicable to improve the bearing capacity, stiffness and ductility of the main members under pressure (bridge piers, arch ribs, truss bars, etc.)
Reinforcement with reinforcement method: reinforcement with reinforcement method is to increase the size of concrete on the surface of members, increase the stressed steel bar, so that it forms a whole with the original structure, so as to increase the effective height of members and the area of stressed steel bar, increase the stiffness of members, improve the overall bearing capacity of the bridge a kind of reinforcement method.
This method is widely used in beam (slab) bridge and arch bridge arch rib reinforcement.
Reinforcement by adding members: refers to the reinforcement by adding members without widening the bridge deck.
When pier foundation safety performance is good, bearing capacity, superstructure is basically intact, but its bearing capacity can not meet the requirements, through the addition of longitudinal beam to improve the bearing capacity of a strengthening method.
Commonly used methods are: add longitudinal beam reinforcement, replacement of side beam, increase the reinforcement of the auxiliary beam.
Reinforcement method of changing structural stress system: strengthening old Bridges by changing structural system usually refers to adding additional members and carrying out technical transformation to change the stress system and stress state of the bridge, so as
to reduce the stress of load-bearing members, improve bridge performance, and achieve the purpose of improving bearing capacity.
Commonly used method: simply supported to continuous method;
Add auxiliary pier method;
Eight character support method;
The girder bridge is transformed into a composite system of girder and arch;
Change the bridge into culvert reinforcement;

The bridge reinforcement

What rules should bridge reinforcement follow

Bridge reinforcement should be carried out in accordance with certain laws. The general procedures of bridge reinforcement are as follows:
Investigate and determine the purpose, requirements and technical standards of technical transformation.
Inspect bridge status and damage.
Investigate the bridge's historical technical data and current traffic conditions.
To draw up and compare the maintenance, reinforcement and reconstruction plans.
Plan to determine and implement.
After the completion of reinforcement acceptance.

Bridge reinforcement requirements

The bridge technical transformation and the reinforcement project usually requests in does not interrupt the traffic or as far as possible few interrupts the traffic condition to carry on, requests the construction technology to be simple, the construction speed is quick, the construction period is short, reduces the traffic jam as far as possible.
The construction site is narrow and crowded, which is often restricted by the original structure.
Reinforcement construction often has a negative impact on the original structure and adjacent structural components, should minimize the damage to the original structure, for the use of no value of the components should be scrapped, dismantled.
Demolition, cleaning the original structure of the workload is larger, the project is more cumbersome, fragmentary, there are many unsafe factors, requires the construction personnel to pay attention to the safety of operation, strengthen the construction quality, construction management.
The formulation of technical transformation and reinforcement program should fully consider the balance between the strength, stiffness and service life of the new and old structure, so as to ensure the joint work of the new and old structure and make the strengthened structure reach the goal of safety, reliability and durability.

Key words: old bridge repair and reinforcement old bridge reinforcement bridge reinforcement