Reinforcement of frame beam by fiber wrapping

Project overview

The main structure of the project have been completed, it is found that during the inspection of concrete strength in the main structure of the project, 12# dormitory building four layer E-G/28 axis frame beam of the original design of concrete strength is C25, after Haining Xinye Construction Engineering Testing Center of the beam concrete strength of drill core sampling inspection found the actual concrete beam the strength of 20.0MPa, but did not appear on the surface of the crack.

After the design, it is decided to reinforce the unqualified beam. In order to ensure the flexural strength can meet the requirements of the original design and does not affect the indoor space and appearance, intends to determine the beam reinforced with carbon fiber wrap.

The parameters of the unqualified beam are as follows: the section size is 200 x 750, the reinforcement 2C18; 5C22, the beam span 7m, the main body height of 3.6m, and the design strength of the beam concrete is C25.

Applied to the beam side by sticking two layers of carbon fiber and sticking carbon fiber on the bottom of the beam. The width is 150.0mm, the net spacing is 150mm, the height is 600mm, and the U type paste is adopted.

Parameters of cfrp sheet at the bottom of the beam

Number of sticker layers: n _cf = 1

Single layer thickness: t _cf = 0.111 mm    

Modulus of elasticity: E_cf = 2.50 × 10⁵ MPa

Tensile strength: f_{c f k} = 2000.00 MPa

Cross section area of carbon fiber sheet at the bottom of the beam: A_cf = 51.10 mm²

Considering the two time force, the initial bending moment of the actual action on the section before reinforcement is calculated: M_i = 22.00 kN·m.