DUAL SYSTEM IN STAAD

[czar07]

Could anyone help me about dual system in STAAD

1. How can I command Staad to carry 25% OF base shear on Moment frames and 75% on Walls?
- do I need to create two models for each and anlayze?
- use change command to analyze the system separately
- or can I create separate loading for each system and apply factors (25% & 75% for frame & wall respectively)
2. In reality, do frames actually perform as it will be analyzed with 25% of base shear during earthquake? if so, how can we ensure this? specially if some beams are supported by the wall

please enlighten me.

thanks

 

[Sye123]

The lateral force will be shared by the lateral force resisting system based on their relative lateral stiffness. This would be done automatically and there is no option for the user to influence that in STAAD.Pro. For what you are looking for, the closest approximation would be to first analyze the combined model ( with walls and the moment frame ) to find out the base shear. Eventually you may create two separate primary cases one with 25% of the lateral load and the other with 75% of the lateral load and for each case, you may specify the appropriate members INACTIVE ( would be IGNORE STIFFNESS for plates if walls are modeled as plates ). Each load case would have its own ANALYSIS command followed by a CHANGE command.

 

[czar07]

Thank you very much Sye123, to sum it up, there will be two cases for each X & Y direction for Earthquake load, ( EQ-X & EQ-Y for moment frame, and another EQ-X & EQ-Y for shear wall).

just want to clarify this "would be IGNORE STIFFNESS for plates if walls are modeled as plates ", will it be the same if I use SURFACE?

Thanks again Sye123