Combinations Used in Combination Account

S

Sadi Özsaraç

New Member
Hello, there is a section that stuck in my mind, I would like to share with you and get engineering advice. For the combinations used in steel calculations -G+Q combination and G+0.5s combination are used for the purlin deflection calculation. -Many combinations of earthquake loads are used for beam-column strength calculations, etc. For example, the İdecad program checks the diagonals. It reflects the most unfavorable situation to the results according to the strength and slenderness ratios. In the joint calculations of the braces, the joint calculations are made according to the axial force. The first thing I want to ask is, I examined the calculations made by Idecad on a project. When I look at the section effects section, the Axial force value in the combination used for the joint calculation is not made according to the most unfavorable axial force. There are combinations that are greater than the value used in the calculation (for example, roof braces). So as engineers, which combinations should we use in the combination calculations? Is there a special section in the regulation for the combination calculation, such as the purlin deflection calculation? Or are the steel combinations we use in the general strength calculation valid for the joints? Or should the most unfavorable combination used in steel strength be used for the joint calculation values? As you know, Idecad de Guse combinations cannot be calculated. But Butt Plate joints can be solved in Idecad. I saw that the controls used for the butt plate joint calculation are similar to the Guseli joint. (controls for column body leakage, column body wrinkling, etc.) 2- Is it necessary to define the gusset joint as a long forehead plate and use the most unfavorable value among the combinations given in the design report in the joint calculation, or are there specified combinations for gusset or butt plate joints? I would like to get the opinions of you esteemed engineers, Have a nice day
 
Hello there; - The most unfavorable combination in both element and joint design is not based on only one force. The one that will give the highest rate from the control is used. For example, the design for the column is done under combined effects. Not only the greatest moment or the greatest axial force is looked at. The combination that will maximize the combined effect equation is looked at. The same is true for child controls of joins. The combination at the bottom of the combination is the combination of the value that gives the highest ratio in the checklist. If you want to design a joint that the program does not do, the ideal would be to enter a 4-bolt joint from the same group, for example instead of a gusset, and read the forces at the joint. If you want to learn in detail the combinations used in the design of elements and joints, you can refer to AISC 358-16. You can find the Turkish steel regulations in the Steel Structures Application Guide available both in the regulation and on the website of the Ministry of Environment and Urbanization.
 
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