# Construction Requirements

The structural requirement parameters specified here refer to the limits of flange width thickness ratio and web height thickness ratio, as well as the section type of axial compression members. Generally, this parameter is automatically calculated by the program. However, in order to make it easier for users to design the program more flexibly, you can also set the parameters required here.

## Flange Width Thickness Ratio / Web Height Thickness Ratio

The local stability inspection of components must meet the requirements of table 3.1.5 and 7.3.1 of steel code (GB 50017-2017).

When considering earthquake resistance, it should also meet the seismic code.

For the framed structures, the width-to-thickness ratio of the elements of beam and column shall conform to the requirements in Table 8.3.2.

Table 1. Width-to-thickness ratio limit of the elements of beam and column (Table 8.3.2)
column Flange overhanging part of I-section 10 11 12 13
Web of I-section 43 45 48 52
Plates of box-section 33 36 38 40
Beam Flange overhanging part of I-section or box- section 9 9 10 11
Flanges between both webs of box-section 30 30 32 36
Webs of I-section or box- section 72-120Nb /(Af) £60 72-100Nb /(Af) £65 80-110Nb /(Af) £70 85-120Nb /(Af) £75
Note:
1. the values listed in the table is applicable to Q235 steel, other steel types shall multiply by $235/fay$
2. $Nb/(Af)$ is the axial compression ratio of the beam.

In the program, it is necessary to specify the seismic design or seismic grade to consider the restrictive provisions of the seismic code. For the members using seismic design (specified in the Chinese Steel Design dialog), their strength and stability should be reduced according to the code, and specified in the Reduction Factor of Bearing Capacity.

Note: When the circular pipe is a beam, the diameter thickness ratio is not specified, and the value shall be taken according to the column in table 3.5.1.

When the seismic option is selected, the program will check the provisions in the Table 8.3.2 and 8.4.1 of the seismic code.

When checking the seismic height thickness ratio of beam webs, when the tested load combination does not include seismic conditions, the seismic height thickness ratio limits of beam webs shall meet the requirements of grade I ≤ 60, grade II ≤ 65, grade III ≤ 70 and grade IV ≤ 75 respectively.