Modeling Single Angles and their Centroids

[ENGINEER92]

Specifically what I am talking about is mounts on telecommunication towers, I attached some pictures to show what I am talking about (I apologize if the picture didn't upload, I was having trouble with the attachment). I would say the common practice for these mounts is to model them bolt to bolt and not to take into account the eccentricity of the centroids and the moment the eccentricities would produce. I feel like if I start taking into account the eccentricity I am making this much more complicated then it needs to be. I typically like to adhere to the KISS methodology and try to keep things simple. I would like to hear people opinions on this and whether they would take into the account eccentricity or not.

Thank you ahead of time for any thoughts and comments.

 

[ENGINEER92]

Link

The link to the pictures is above.

 

[WARose]

For a static analysis, I never model the eccentricity of the braces. It won't change the force it sees. The best thing to do is to get the forces from the analysis and check them with hand calcs. (With most software, I wouldn't trust it's code check for a single angle anyway.)

 

[tenguy23]

If you meet the exceptions in Chapter E5 of the AISC, you are allowed to neglect eccentricity.

When you do not meet the exceptions, technically yes you are required to analyze eccentricity. I have found this is significant if the angle is already taking axial AND flexure.

I Use McNulty's Single Angle Design Manual. It covers the wide array of eccentricity cases that are often overlooked if you HAVE to analyze eccentricity.

 

[ENGINEER92]

WARose and tenguy23, thank you for responding. It was good to see other people opinions on this.

 

[WARose]

Anytime. Keep in mind AISC (13th edition) has tables for eccentrically loaded angles. (See Table 4-12.)