Zhuzhou Bridge reinforcement

来源：安德美    发布时间：2016年12月09日 12:43:18

1 Introduction

 Many buildings are affected by the construction age, the structural use of functional changes, technical conditions or natural disasters and other factors, there is insufficient capacity, deformation capacity, reduced capacity or anti-seismic ability to reduce the phenomenon of fatigue, can not meet the current "concrete structure Design Code "and" Code for Seismic Design of Building Structures ". Therefore, it needs to be reinforced and reinforced. China's structural reinforcement and reinforcement in a lot of research and practice, engineering commonly used structural reinforcement methods have increased cross-section method, outsourcing steel reinforcement method, prestressed reinforcement, sticky steel reinforcement and bonding carbon fiber composite material reinforcement Law and so on. The traditional method of reinforcement is relatively backward, the construction method and construction technology are complex, which have certain influence on the weight and area of the structure. The method of reinforcing carbon fiber reinforced composite has high strength, high efficiency, corrosion resistance, convenient construction and no increase of structural dimension And other advantages, in the project has been widely used [1].

 2. Carbon fiber composite material excellent performance

 Carbon Fiber Reinforced Polymer (CFRP) reinforced concrete structure technology is a new and efficient structural reinforcement technology. The carbon fiber reinforced concrete structure technology used in the project is to use the resin cementing material, the carbon fiber material to the concrete structure surface, in order to achieve structural reinforcement and improve the structure of the purpose of mechanical properties.

 Compared with the traditional reinforcement method, carbon fiber reinforcement technology has the following excellent performance [1].

 (1) high strength and high elastic modulus. Carbon fiber high strength, ultimate tensile strength of about 10 times the steel, elastic modulus and steel similar. Therefore, it can fully utilize the characteristics of high strength and high elastic modulus to improve the bearing capacity and ductility of concrete structures and components, and improve the mechanical properties of reinforced concrete structures to achieve the purpose of strengthening and repairing.

 (2) anti-corrosion ability, durability. The chemical stability of the carbon fiber is stable and does not react with the chemical substances such as acid, alkali and salt. Therefore, the reinforced concrete structure with carbon fiber has good corrosion resistance and durability, and solves the chemical corrosion problems encountered in other reinforcement methods; But also eliminates the sticky steel reinforcement required for regular anti-rust maintenance, saving maintenance costs.

 (3) thermal expansion coefficient is small. The thermal expansion coefficient of carbon fiber is very small, its coefficient of thermal expansion in the fiber direction is almost equal to zero, this characteristic is unmatched by any other material, the coefficient of thermal expansion perpendicular to the fiber direction is relatively large, but isotropic products and other materials Compared to the smallest.

 (4) construction is simple, high efficiency. Carbon fiber sheet reinforcement does not require large-scale construction machinery and heavy equipment, construction occupies less space, no wet work, carbon fiber cloth is flexible, according to the design size with scissors or blades to cut any, simple operation, construction speed. According to the statistics, paste carbon fiber reinforcement work efficiency is to paste steel plate reinforcement 4 to 8 times.

 (5) construction quality easy to guarantee. Carbon fiber cloth is a flexible material, even if the surface of the reinforced component is not very smooth, after repair, the effective paste rate can reach more than 95%.

 (6) a small impact on the structure. Carbon fiber materials, light weight, thin, reinforced repair components, basically do not increase the weight of the original structure and size, does not affect the structure of the use of space.

 (7) a wide range of applications. Can be used for different structural types (such as buildings, structures, bridges, tunnels, culverts, etc.), different structural shapes (such as rectangular, round, curved surface structure), different materials components (such as concrete structure, wood structure, steel structure ), Can also be used for different parts of the structure (such as beams, plates, columns, nodes, arch, shell, pier, etc.) and the strengthening of different weak factors. Particularly important, for some large civil engineering structures, such as large bridge piers, beams and deck panels, 3. carbon fiber reinforced concrete composite structure

 In practice, the carbon fiber used to reinforce the material is mainly carbon fiber cloth. Carbon fiber reinforced concrete technology in the application of concrete structure has been more mature, mainly concentrated in the following aspects.

 (1) to improve the shear capacity

 The contribution of carbon fiber sheet to the shear behavior of members is similar to the effect of stirrups, and shearing force is shared with concrete. In addition, the carbon fiber cloth has the restraint effect on the core concrete, and can bear the tensile stress, prevent premature yield of the main reinforcement, inhibit the occurrence and development of shear cracks. Therefore, CFRP can significantly improve the shear capacity of reinforced concrete members, enhance the deformation capacity of components. The main factors affecting the shear reinforcement effect are the material properties of CFRP sheets, the width and the number of layers of CFRP sheets, the quality of adhesive, the quality of pasting, the shear span ratio, the loading condition of the members before reinforcement, ].

 (2) to improve the flexural capacity

 Because the carbon fiber cloth has the characteristic of high tensile strength, the carbon fiber cloth can be affixed to the tensile surface of the member, so as to bear the tensile stress together with the concrete, so as to enhance the flexural bearing capacity of the members. After the carbon fiber sheet is attached, the flexural load-carrying capacity of the flexural members is obviously improved, and the development of the cracks is effectively restrained. The deformation and ductility of the members are improved significantly [4]. The main factors influencing the flexural strengthening effect are carbon fiber cloth Material properties, the width and number of layers of carbon fiber cloth, the quality of adhesive, the quality of the paste, the loading condition of the members before reinforcement, the reinforcement ratio of longitudinal reinforcement, and the cross-sectional dimension of members [4,5].

 (3) to improve seismic capacity

 As the carbon fiber cloth can restrain the crack of the component, improve the rigidity of the component and the ability to resist the deformation, when need to improve the seismic capacity of the component, can also be reinforced with carbon fiber cloth and toughening. Especially for the reinforced concrete beam-column joints and the axial force of the reinforced concrete columns, often require the seismic design of components. It can improve the ductility of concrete structures and increase the energy dissipation capacity, and have good effect of seismic reinforcement [6]. At this time, it is necessary to take into account the axial compression of the RC columns The ratio of carbon fiber cloth, the ratio of stirrup and slenderness ratio on the deformation capacity and seismic performance of CFRP strengthened members.

 (4) to improve anti-fatigue capacity

 For the members subjected to dynamic load or repeated load, it is required to have sufficient anti-fatigue performance. The size of anti-fatigue capacity is related to its cross-sectional dimension, reinforcement ratio, longitudinal reinforcement type and load level. Reinforced concrete beams and prestressed reinforced concrete beams strengthened with carbon fiber cloth will not reduce the strength and rigidity of the strengthened members after 2 million repetitive loads and will not have the phenomena of flaking and brittle fracture. [7] Prestressed CFRP sheets, the existence of prestressed CFRP sheets, the stress amplitude of the longitudinal reinforcement in the members is reduced, and the possibility of fatigue failure is reduced. While the carbon fiber cloth, which is always in high stress state, has good anti-fatigue performance. The fatigue life of the strengthened member is greatly improved and the fatigue deformation is reduced. The fatigue crack resistance of the component is improved greatly, which prolongs the service life of the component.

 4 Conclusion

 Carbon fiber composite material has good durability, resistance to acid and alkali corrosion, less impact on the original structure, convenient construction, and has the advantages that other reinforcement means do not have. The strengthening of concrete structure with carbon fiber composite material can effectively improve the bearing capacity of concrete structure, improve the structural deformation properties, enhance the seismic capacity of structure, improve the fatigue resistance of the structure, the comprehensive reinforcement effect is remarkable. However, there are still some shortcomings in the technology of strengthening the concrete structure with carbon fiber composite materials.

 (1) Carbon fiber is a kind of linear elastic brittle material, only when the component deformation occurs, can give full play to its high-strength high elastic modulus performance. The concrete structure has relatively strict control of deformation, to a certain extent, limiting the ability of carbon fiber composite materials play.

 (2) After the concrete structure is strengthened by the CFRP sheets, the peeling and stripping are easy to occur, so that the reinforced concrete structures show obvious brittle failure patterns, which have an impact on the reliability level of the structures.

 (3) At present, there is little research on the mechanical properties of concrete structures strengthened by CFRP under long - term load and impact load, and should be studied in similar applications.

 (4) As for the concrete beams strengthened with carbon fiber material, the mechanism and calculation method of shear and bending strengthening have been studied and applied successfully. However, the research of carbon fiber reinforced concrete shear wall is still lacking.

 (5) When the carbon fiber composite material is reinforced, the building structural adhesive is used as the binder of the carbon fiber composite material and the concrete structure. The adhesive is sensitive to temperature, so that the strength of the reinforcing member is greatly affected by the temperature. To further strengthen research in this area.

ShiFengQingShi road seedling across the railway bridge from now until March 30, 2017 will be reinforcement transformation. During the construction period, Shifeng traffic police brigade will take the appropriate traffic control.

 Shifeng Qingshi Road, Qingshi Road, Chongming County, was built in the 80s of last century. It is 30 meters west of Qingshi Road connecting with Shiwankou ramp. The length of the bridge is 56 meters and the width of the bridge is 17 meters. The existing structure Capacity has not fully meet the requirements of highway carrying capacity.

 【Phase 1】 October 11, 2016 to January 24, 2017, the old bridge T-beam demolition, bridge reinforcement during the main project construction, construction of the cross-railway bridge Qingshi road sections of the two-way road construction closed.

 【Phase II】 January 24, 2017 before the completion of the main cross-rail bridge, to 2017 during the Spring Festival period clear stone road across the railway bridge to suspend construction, clear stone road across the board to restore two-way traffic. 2017 March 15 to 30 temporary bridge demolition construction and completion of the inspection period, the clear stone road across the railway bridge to implement temporary semi-closed road construction.

 During the construction period, the Qingshi Road is closed to the railway bridge and the vehicles and pedestrians are prohibited. Qing Shi Road across the railway bridge 250 meters west of the box girder precast construction site, occupies the Qing Shi Road, north half of the motor vehicle lane, reserved for the southern half lane to ensure that Qing Shi Road Sinopec gas station residents travel along the west.

 [Vehicle routing is as follows]

 1, Shifeng District Qingshuitang to Xiangtan, Changsha direction: clear stone square - old strains of easy road (orchard road) - red avenue (Times Avenue) - strain junctions from the bypass.

 2, Shifeng District Qingshuitang to Tin Sum Interchange direction:

 A: The construction of North Road - ring square - Xiangtian Road roundabout.

 B: Qingshi Road - Da Chong Road - Shao Feng Road - Times Avenue South Auxiliary Road - Times Avenue detour, large red road limit, only car traffic.

 3, the Shanghai-Kunming Expressway Zhuzhou North to the Shifeng Tang Shifeng District, the direction of: Times Avenue - Tin Sum Interchange - ring Tin Road - Sapphire Square - North bypass construction.

 (Note: Times Boulevard by Zhuzhou North toll station to the direction of Shanghai-Kunming high-speed September to the end of November Shanghai-Kunming high-speed Xiangtan to Loudi section of the northern half of overhaul, Shanghai-Kunming high-speed section of the east to west traffic control, Zhuzhou North toll station entrance closed, Zhuzhou to go to Shaoyang, Huaihua direction required by Changsha to long Shao Lou high-speed, two wide high-speed bypass)

 In addition, during the closure of Qingshi Road, dangerous goods vehicles, medium and heavy-duty trucks and special operation vehicles in urban areas continued to carry out traffic control measures during the peak period. 17: 00-9: 00; 17: 00-20: 00 Prohibited the transport of dangerous goods vehicles, heavy-duty trucks, special operations vehicles through the road to the south of the road, . Not for urban areas of dangerous goods transport vehicles restricted zone permits transport of dangerous goods 24 hours a ban on traffic.

 At the same time, has been for urban areas of dangerous goods transport vehicle closed area clearance for the Qing Shi Road, Times Avenue traffic line adjustment for the construction of North Road, Sapphire Square to the north, ring road, 00 - the next day 7:00. The peak period of time forbidden line by the Qing Shi Square - old strains of Yi Road (Orchard Road) - Red Avenue (Times Avenue) U-turn - Times Avenue bypass.