Eccentricity load application

[3JC]

Dear collages from forum,

I have a question: is it possible to apply a eccentricity in the application of a puntual load? I send in attach a picture of the problem: it is a portal, and puntual loads have to be applied in the crane runway line.
Thank you very much.

https://dl.dropbox.com/u/8161370/Crane_Load.PNG

Regards,

Juan José

 

[johnbridge231]

Since frames are modelled as single lines using their centroid axis, you cannot apply such loads directly. But instead you can apply additionally the resulting moment at the center of the cross section. This would be a proper modelling in my mind.

Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis

http://www.engissol.com/cross-section-analysis-design.html

 

[3JC]

Dear John,

The method that you say, I didn´'t like to do because it is necessary to modify the geometrie and the loads when changes are performed. I have designed the column under the runway line and then I have apply a constrain with the upper columns. Results are identical. Thank you very much anyway.

Regards,

Juan José

 

[stressed]

Use of joint constraints, as you've discovered, is a convenient way to assign eccentric loading. You can rotate local axes of joints and/or frames to assign load in any direction. Frame insertion point is another modeling approach for eccentric loading.

 

[johnbridge231]

stressed suggests two right alternatives, among them I would prefer to use joint constraints.

Analysis and Design of arbitrary cross sections
Reinforcement design to all major codes
Moment Curvature analysis

http://www.engissol.com/cross-section-analysis-design.html

 

[3JC]

Dear collages: thank you very much. One adittional question: when I modify the position of a bar (when I move it) then loads apply dissapear, and the same thing with boundary conditions (supports) or constrains. Do you know anyway to avoid this, has the software any option to unvalidate this? Thank you very much.

Regards,

jJ

 

[dgerashki]

The load definitions do not disappear when you move a frame if they are assigned to the frame. Be more specific how you move it.

Anyway I prefer using replicate option instead, because you can choose which assignments to copy.