Concrete Beam Strengthened

The Farmer’s Market in Toupai Town, Jinxiu County, built in 1993, has a reinforced concrete frame structure and is still in use. In 2009, we were commissioned by the owner to conduct structural testing and reliability appraisal of the market.

The appraisal results showed that the beam reinforcement was tested by ultrasonic method combined with sampling excavation, and it was found that some frame beams were insufficiently reinforced. Among them, the beam bottom reinforcement of the axle frame beam is only 2Φ16, and the stirrup is 8@200. According to the current "Specifications for Design of Concrete Structures", the design value of the mid-span bending bearing capacity Mu is 28.9kN·m, and the design value of the bending moment M is 39.9kN·m according to the actual force combination, which cannot meet the requirements of the normal section bearing capacity. .

(1) The specification and tension control stress of the carbon fiber strip. The carbon fiber strip adopts 50-1.2 type carbon fiber strip, the tensile design strength is 2300MPa, the elastic modulus is 1.73×105MPa, the width is 50mm, the thickness is 1.2mm, Af=60mm2, and the length of the reinforced carbon fiber strip at the bottom of the beam is 3.0m. The tension control stress value of the carbon fiber strip is σcon=35%fu=805MPa.

By applying prestress, part of the cracks of the beam are closed, the rigidity is also improved to a certain extent, and the deflection of the beam in the middle of the span is reduced by 1.2mm;

The construction of the prestressed carbon fiber strip reinforcement method is convenient and fast. It does not require large-scale surface cleaning of the original structure. The reinforcement construction does not require large-scale machinery, and the construction is completed after the jack is removed after the tension is completed. The construction period is short and does not affect the use of the structure.