3.2　Concrete

3.2.1　The grade of concrete used in CFST arch ribs shall not be lower than C30，and should be Grades C40-C60.

3.2.2　The characteristic axial compressive strength fck，design axial compressive strength fcd，characteristic axial tensile strength ftk，design axial tensile strength ftd and elastic modulus Ec of the concrete shall be in accordance with those specified in Table 3.2.2.The shear modulus Gc of the concrete may be taken as 40% of the elastic modulus Ec specified in Table 3.2.2.The Poissons ratio μc of concrete may be assumed to be 0.2.

Table 3.2.2　Strengths and elastic modulus of concrete（N/mm2）