At times, you may find you want to carry out design checks, which are different from those prescribed in the standard codes. To facilitate this, Steel Designer has an additional code named User, which lets you enter design rules and check members according to these rules.
To activate the User code,
Ø choose User from the Code menu.
Now whenever you do any checking or designing, Steel Designer will use the User code rules to determine a member's efficiency. You can view and edit the design rules in the User code by choosing the Edit User Code item from the Code menu. The rules in the User code are grouped into the four groups which appear in the Check and Design dialogs, that is Beams, Ties (or tension) Struts (or compression) and Beam-Columns (or combined).
To edit the User code
Ø Choose Edit User Code… from the Code menu
Ø Click on the button of the part of the code you wish to change
Ø Type in new rules or modify the existing design rules
The syntax of the design rules is the same as that of the Calculation sheet in Multiframe. This is very similar to the format used in most programming languages and spreadsheets. The following variables are available to help you construct your design rules. These variables are evaluated for each member as the member is checked.
|
Variable |
Value |
|
L |
Length of member* |
|
Kx |
Effective length factor in major plane |
|
Ky |
Effective length factor in minor plane |
|
Lbx |
Unbraced length for buckling about the major axis* |
|
Lby |
Unbraced length for buckling about the minor axis* |
|
rx |
radius of gyration about major axis* |
|
ry |
radius of gyration about minor axis* |
|
E |
Young's modulus of steel |
|
ft |
maximum tensile stress |
|
fc |
maximum compressive stress |
|
fbx |
maximum bending stress about major axis |
|
fby |
maximum bending stress about minor axis |
|
fy |
yield stress of the steel |
|
fu |
ultimate tensile strength of the steel |
|
y |
height of the highest end of the member above y=0* |
|
a |
web stiffener spacing* |
|
Cb |
bending coefficient |
|
Cmx |
major interaction coefficient |
|
Cmy |
minor interaction coefficient |
Note that all length variables (marked with an asterix * above) are given values in the same units as the units for deflection as specified in the Units dialog. This ensures that the dimensions of the resulting calculations will be consistent. All stresses and strengths have units as set for the Stresses option in the Units dialog.
The four different parts of the User code correspond to the four groups of checks available when using the Check and Design commands.
The bending checks can be used to check bending stresses, shear stresses and deflections. These formulas will be applied to both the major and minor axis beam calculations.
The tension checks will be used to evaluate the tensile stress on the member.
The compression checks will be used for the Slenderness and Compression check options when using the Check and Design commands.
The combined checks will be used for the Combined check options when using the Check and Design commands. The combined stress checks check the user formula against a combined stress ratio (CSR) of 1.0.
Only the calculations that have their check box checked will be used when you use the Check or Design commands.