Before performing design checks, it is necessary to enter basic design data such as effective length, grade of steel etc. This information can either be entered in the Frame window, by selecting members and using the commands under the Design menu, or it can be entered in tabular form in the Design Details tab of the Data window.
Although most of the design variables are pre-set to the most commonly used values, you will probably want to enter the design information for at least some of the members in the frame that you wish to check. You set design variables by selecting the members you wish to change and then choosing the appropriate command from the Design menu.
There are a number of design variables which are used when doing checking to the code. A summary of all of the design variables is as follows;
|
Variable Name |
Description |
Default Value |
|
Fy |
Yield strength of the section's steel |
250Mpa |
|
Fu |
Ultimate Tensile Strength of the section's steel |
320Mpa |
|
Kx |
Effective length factor for buckling about the section's strong axis |
1.0 |
|
Ky |
Effective length factor for buckling about the section's weak axis |
1.0 |
|
Lcx |
Unbraced length for preventing column buckling about the section’s strong axis. |
member's length |
|
Lcy |
Unbraced length for preventing column buckling about the section’s weak axis. |
member's length |
|
Lateral restraints |
The lateral restraints acting on the member. |
Each end of the member is fully restrained at both flanges. |
|
ds |
Length of stiffeners. Assume that all stiffeners have the same length regardless of whether they are web stiffeners or flange stiffeners |
0.0 (ie no stiffeners) |
|
s1 |
Edge distance between the first stiffener and the element edge. Assume that all stiffeners on a web or flange are symmetric to the centre line of the element. |
0.0 (ie no stiffeners) |
|
s2 |
The distance between the first and the second stiffener. Assume that all stiffeners on a web or flange are symmetric to the centre line of the element. |
0.0 (ie less than 3 stiffeners) |
|
No. of stiffeners |
Number of stiffeners. This is either the total number of stiffeners on the web(s) or the total number of stiffeners on the flange(s). eg. for a C section with 8 stiffeners on flanges, so each flange has 8/2 = 4 stiffeners. However, for a back-to-back C section with 8 stiffeners, each flange has 8/4 = 2 stiffeners. |
0 (i.e. no stiffeners) |
|
No. of Flange Holes |
The number of holes in the flanges of the section. |
0 |
|
Diameter of Flange Holes |
Diameter of holes in the flanges of the section. |
0.0 |
|
Total Height of Flange Holes |
Total height of any bolt holes in the flanges of the section. This value may be input directly or computed automatically when the number and diameter of flange holes are specified. |
0.0 |
|
No. of Web Holes |
The number of holes in the webs of the section. |
0 |
|
Diameter of Web Holes |
Diameter of holes in the webs of the section. |
0.0 |
|
Total Height of Web Holes |
Total height of any bolt holes in the webs of the section. This value may be input directly or computed automatically when the number and diameter of flange holes are specified. |
0.0 |
|
kt |
Correction factor for the distribution of forces. |
1.0 |
|
Max Depth |
The maximum depth of section which may be chosen when using the Design command |
Depth of the initial section |
|
Min Depth |
The minimum depth of section which may be chosen when using the Design command |
depth of the initial section |
|
Max Width |
The maximum width of section which may be chosen when using the Design command |
width of the initial section |
|
Min Width |
The minimum width of section which may be chosen when using the Design command |
width of the initial section |
|
Cs |
Moment coefficient. +1.0 for moment causing compression on shear centre side of the centroid while -1.0 for moment causing tension on shear centre side of the centroid. |
1.0 |
|
Cb |
Coefficient depending on moment distribution in the laterally unbraced segment. |
1.0 |
|
Cmx |
Coefficient for unequal end moment. |
1.0 |
|
Cmy |
Coefficient for unequal end moment. |
1.0 |
|
R |
Purlins' reduction factor. For channel- and Z-purlins in which the tension flange is attached to sheeting, the member bending capacity subjected to lateral buckling is calculated with clause 3.3.3.4. |
1.0 |
It is not necessary to enter all of the above information for all members. Usually you will want to check some members for bending, others for compression and so on. The items under the Design menu help you enter just the required information depending on what type of check you are doing.