Basement Of Civil Building

Prestressed Carbon Fiber Laminate Project

The reinforcement scope in a project is the reinforcement of the basement roof. Reinforcement treatment methods: basement roof steel support jacking, new reinforcement at the bottom of the slab, carbon fiber laminate at the bottom of the slab, steel plate at the bottom of the slab, crack repair and surface plastering after reinforcement, etc. As a new technology, carbon fiber reinforcement has good reinforcement effect and flexible and convenient construction, and has unique advantages. Therefore, this paper focuses on the analysis of prestressed carbon fiber plate reinforcement construction (see Figure 1).

Features of Prestressed Carbon Plate Reinforcement

1) Because of its unique physical properties, carbon fiber laminate has good tensile, corrosion resistance and shock resistance. According to the experiment, after 10,000 times of freezing and thawing under normal environment, under the action of simulating normal light and humidity, the performance of carbon fiber has no obvious attenuation. In addition, the tensile strength of carbon fiber laminate is more than 10 times that of ordinary steel bars, and at the same time, it has the advantages of high elastic modulus, and it can be effectively used for the reinforcement of concrete structures when combined with epoxy resin.

2) Under the same conditions, the weight is only 1/5 of the traditional steel, and it has excellent toughness. At the same time, it can be customized and freely cut at any length, which is more advantageous than the traditional steel strand.

3) The construction is flexible and convenient, the carbon plate does not need pre-processing and the quality is controllable, and it does not require open flames and wet operations and large-scale machinery to enter the site, economical and convenient, and short construction period.

4) Thanks to its good physical properties, it is not corroded by the environment. Among the current building materials, it is one of the best corrosion-resistant materials. The good corrosion-resistant performance makes the maintenance cost in the later period extremely low.

5) Carbon plate with active prestressing system can better exert its reinforcement effect.

6) Compared with carbon cloth, carbon plate is more straight and easy to stretch.

7) According to the experiment, a carbon plate with a thickness of 1.2 mm can achieve the same effect as 5 layers of carbon cloth.

8) Medium carbon laminate is more suitable for brick-concrete structure wall reinforcement.

9) The carbon plate significantly improves the ductility and tensile stress of the overall concrete structure.

10) Compared with the traditional prestressed reinforcement method of steel strands, the stress attenuation of carbon fiber laminate reinforcement is smaller than that of steel strands. According to relevant foreign studies, the carbon fiber laminate can still guarantee more than 75% of the strength after 10 million stress cycles at 2 000 MPa. Therefore, when 50% of the maximum stress is taken as the initial stress, the relaxation can be ignored.

Reinforcement principle of prestressed carbon fiber laminate

The prestressed carbon fiber plates are reinforced and distributed at the bottom of the basement plate, and the corresponding prestressing is applied to the carbon fiber plates by fixing the anchors with the bolts. The prestress is transferred through the carbon fiber panels to the concrete structure at the bottom of the slab connected to the anchorage. When the stress of the concrete structure is too large under the condition of external force load, it can be offset by the prestressed prestress of the carbon plate to prevent the deformation and cracks of the concrete structure. Therefore, the stability and bearing capacity of the overall structure are improved, and the resistance to deformation and cracks of the concrete structure is greatly improved. The tensile strength of carbon fiber laminate is based on the large deformation of the structure, so by applying prestress to the carbon fiber laminate, the deformation of the concrete structure can be solved, and the bearing capacity of the concrete structure can be effectively improved. But at the same time, when the concrete structure is deformed by force, the carbon fiber laminate and the anchors carried by it need to bear huge stress. Therefore, it is easy to cause peeling and damage of carbon fiber panels, anchors and concrete structures. This is also an important factor restricting the reinforcement technology of prestressed carbon plates. Therefore, a large number of scientific researchers in the engineering field are currently conducting experimental research to solve the problems of anchoring and prestressing of carbon fiber plates.

Construction Control Points

①When multiple carbon fiber boards are pasted in parallel, the gap between the two boards shall not be less than 5mm;

②The distance between the wall pier and the fixed end is required to be less than 100mm, and the distance from the end of the tension end is less than 200nun;

③ The pretensioning range is about 25kN, and it is necessary to continuously observe the deflection changes of the structure while pretensioning;

④Each row needs to be tensioned step by step, and after each stage of tension, it needs to stop for 2~3min before proceeding to the next stage of tension;

⑤For curing time requirements: when the construction environment temperature is greater than 25 degrees Celsius, the curing and curing time is 7 days. When the temperature is less than 25 degrees Celsius, the curing time should be extended accordingly. If it is lower than 5 degrees Celsius, auxiliary curing and curing measures are required for curing;

⑥ The product storage conditions of carbon board should be kept dry and avoid direct sunlight;

⑦ Do not violently roll or drag the carbon fiber board material on the ground to avoid damage;

⑧ The carbon fiber board is a brittle material. If the tensioning operation is improper, it may cause splitting, fracture, etc. Therefore, protective measures should be taken during the construction process, and it is not allowed to operate directly below the axis of the carbon board to avoid danger;

⑨ During the tensioning operation, it is necessary to ensure the site lighting, site ventilation, and open sight.