 # Stability Coefficient

The stability coefficient is divided into overall stability coefficient of flexural member (beam) and stability coefficient of axial compression member (truss). The program can automatically judge the coefficient according to the section type and force characteristics of the designed member. The built-in judgment principles in the program are as follows.

1. The overall stability coefficient of flexural members (beams) is calculated by the approximate calculation method in Appendix C of the code.
For I-section and λy > 120εk
$ϕb=βb4,320λyAhWx[1+(λyt14.4h)2+ηb]εk$
For I-section and λy ≤ 120εk
1. When the cross section is biaxially symmetric:
$ϕb=1.07−λy244,000fy235$
2. When the cross section is uniaxially symmetric:
$ϕb=1.07−W1z(2αb+0.1)Ahλy214,000fy235$
T-section (moment acting on the plane of symmetry axis):
1. When the flange is in compression by bending moment: double angle steel
$ϕb=1−0.0017λyfy235$
Two board combination
$ϕb=1−0.0022λyfy235$
2. When the flange is tensioned by bending moment: $ϕb=1.0$

When the value calculated by the formula is greater than 1.0, take 1.0.

2. For the axial compression member (truss), the calculation method of Appendix D in the code is used. It is related to the section type and slenderness ratio. The classification of section types is shown in table 7.2.1-1. You can also input data to specify the stability coefficient of the component. The default value of the program is automatic calculation, that is, the program automatically calculates the stability coefficient of the component according to the section type and force characteristics of the designed member.