Direct analysis method

[HoshangMustafa]

Hi all

Please find the attached file.

This is to model Example 3.1 of AISC design guide 28. I modeled bracing as tension member as suggested in post 4 in this thread:

https://forums.autodesk.com/t5/robot-structural-analysis-forum/steel-bracing-advanced-bar-properties...

So, how to manage Direct analysis method with this model?

Description of Framing
All lateral load resistance is provided by the tension only rod bracing. The tension rods are assumed to be pin connected using a standard clevis and pin (see AISC Manual Tables 15-3 and 15-7). Beams within the braced frame are bolted into the column flanges using double angles (see AISC Manual Figure 13-2(a)). A single gusset plate connecting the tension rod is shop welded to the beam flange and field bolted to the column flange (see AISC Manual Figure 13-2(a)). All other columns outside the braced frames are leaning columns with simple beam-to-column connections.

[Krzysztof_Wasik]

Hi @HoshangMustafa 

Refer to this tutorial

[Krzysztof_Wasik]

Hi @HoshangMustafa 

Refer to this tutorial 

[Krzysztof_Wasik]

Hi @HoshangMustafa 

You have to define ULS combinations for this model then you can run  run DAM analysis.

Refer to DAM analysis description

[HoshangMustafa]

Thanks, @Krzysztof_Wasik 

I thought that you (and help topic) meant that the two intersecting continuous bars being not divided. But the tutorial states that (it is important that they are divided) (at 0:41).

[HoshangMustafa]

Hi @Krzysztof_Wasik 

I modeled a structure as shown on the tutorial . I applied the compatible node. I can't see the continuity in the My diagram. Can you verify why?

[Krzysztof_Wasik]

Hi @HoshangMustafa 

Compatibility is defined in global system of coordinates (not in local bar system as for releases). You have not released RY in compatibility definition.

[HoshangMustafa]

Hi @Krzysztof_Wasik 

You have not released RY in compatibility definition.

But in the tutorial , it included RY as blocked direction (@ 4:11).

[Krzysztof_Wasik]

Hi @HoshangMustafa 

Your model is rotated by 90 degrees in comparing to model from tutorial. I have marked main beams directions in both models.

 

[HoshangMustafa]

Thanks, @Krzysztof_Wasik 

I'm sorry for this mistake. Another question came into mind. What are practical cases for using compatible nodes structurally?

[Krzysztof_Wasik]

HI @HoshangMustafa 

Compatible nodes can be used when some degrees of freedom are released between two continuous elements.

Some examples:

- connection between continuous purlin and continuous rafter (when continuous bending moment should be obtained for purlin).

- connection between continuous primary and secondary elements in grillage structure (when continuous bending moment should be obtained for both members)

- connection between continuous bracing when connection with pin is used (as presented in message 17)

- it can apply to effect described in message 6, when continuous beam is connected with continuous column and only vertical force should be transferred to column (support by continuous column should be regarded as pinned support)

[HoshangMustafa]

Thanks, @Krzysztof_Wasik 

I appreciate your help.

- it can apply to effect described in message 6, when continuous beam is connected with continuous column and only vertical force should be transferred to column (support by continuous column should be regarded as pinned support)

Please find the attached file. Am I modeling it correctly using compatible nodes?

[Krzysztof_Wasik · Accepted solution]

Hi @HoshangMustafa 

It is defined correctly 

[HoshangMustafa]

Thanks, @Krzysztof_Wasik for your patience. You've been very helpful.

[HoshangMustafa]

Hi @Krzysztof_Wasik again.

- connection between continuous bracing when connection with pin is used (as presented in message 17)

But this message was about continuous beam and column.

Another thought came into mind.

How compatible node is defined for bracing since compatible node is defined in Global direction? For example defining compatible node for bracing in model posted in message 1.

[Krzysztof_Wasik]

Hi @HoshangMustafa 

This answer regarded your question from message 29

[HoshangMustafa]

Hi @Krzysztof_Wasik 

Please follow the last paragraph in message 34, especially my concern is an example in the help file:

Robot Structural Analysis 2020 Help | Compatible nodes definition - example | Autodesk

[Krzysztof_Wasik]

Hi @HoshangMustafa 

Compatible nodes are defined in global system of coordinates, but if it is necessary you can define required angles (for each compatibility) so you can rotate them in respect to Z(alpha angle), Y(beta angle) and X(gamma angle ) global axis. 

[HoshangMustafa]

Thanks @Krzysztof_Wasik 

This is very helpful, especially rotating compatible nodes with respect to global axes. I'll try it.

- connection between continuous bracing when connection with pin is used (as presented in message 17)

If the bracing is defined using tension only bars, why should I use connection with pin?

[Krzysztof_Wasik]

Hi @HoshangMustafa 

I think that description in help does not regard tension only members.

[HoshangMustafa]

Hi @Krzysztof_Wasik 

I think that description in help does not regard tension only members.

Aren't these members bracings? Isn't one member of the cross will be in tension and the other in compression?

If that description doesn't regard tension only members, what members does that description regard?

I wanted to try rotated compatible node for the bracing in my model, but without succeed. Can you help with this?