When fiber composite materials are used to strengthen beams, slabs and other flexural members, in addition to the basic assumptions of the current national standard "Code for Design of Concrete Structures" GB 50010 for the calculation of the normal section bearing capacity, the following requirements should also be met:
1 The stress-strain relationship of fiber composites is linear, and its tensile stress σf is equal to the product of tensile strain εf and elastic modulus Ef;
2 When considering the influence of the secondary force, the hysteresis strain of the fiber composite material should be determined according to the initial force condition before the reinforcement of the component;
3 Before reaching the limit state of the flexural bearing capacity, there will be no bond peeling failure between the reinforcement material and the concrete.
10.2.2 The height ξb,f of the relative boundary compression zone after the flexural member is strengthened shall be calculated according to the following formula, that is, it shall be 0.85 times the control value before the member is strengthened:

 
In the formula: ξb—the height of the relative boundary compression zone before reinforcement, calculated according to the provisions of the current national standard "Code for Design of Concrete Structures" GB 50010.
10.2.3 When the fiber composite material is pasted on the concrete surface of the tensile side of the rectangular section flexural member for reinforcement (Figure 10.2.3), the bearing capacity of the normal section shall be determined according to the following formula:
 
In the formula: M——Design value of bending moment after strengthening of member (kN·m);
χ—height of concrete compression zone (mm);
b, h - rectangular section width and height (mm);
ƒy0, ƒ′y0——the tensile and compressive strength design values of the original cross-section tension reinforcement and compression reinforcement (N/mm²);
As0, A's0——the cross-sectional area of the tension reinforcement and compression reinforcement in the original section (mm²);
a'——the distance from the resultant force point of the longitudinally compressed steel bar to the near edge of the section (mm);
h0—the effective height of the section before reinforcement (mm);
ƒf——The design value of the tensile strength of the fiber composite material (N/mm²), which shall be in accordance with Table 4.3.4-1, Table 4.3.4-2 and Table 4.3.4-3 of this specification according to the type of fiber composite material use;
Afe——the effective cross-sectional area of the fiber composite material (mm²);
ψf——the strength utilization factor introduced by considering that the actual tensile strain of the fiber composite material cannot reach the design value, when ψf>1.0, take ψf=1.0;
εcu—the ultimate compressive strain of concrete, take εcu=0.0033;
εf——design value of tensile strain of fiber composite material, which shall be adopted according to Table 4.3.5 of this code according to the type of fiber composite material;
εf0——The hysteresis strain of fiber composite material when the influence of secondary force is considered, which should be calculated according to the provisions of Article 10.2.8 of this code. If the influence of secondary force is not considered, εf0=0.