Concrete member Design (STAAD Pro - ACI)

Question

Hi 
 Q1: I have been struggling to find out why the concrete design only look at the Load Case #1? Please see the attached screen-shots. 
 Q2: How can I assign all my load cases to design the concrete columns and beams (again plese see the attached file). 
 Q3: What is the load envelopes? Do I need to assign something there? 
 
 Thanks so much for the help.

Modestas · Accepted Answer

Hello, 
 1) The reporting of critical load case is based on the highest reinforcement requirement. In other words the load case that requires the Maximum Reinforcement is reported as the critical case. If it so happens that the reinforcement requirement is minimum for all the load cases, then only the first load case gets reported as the worst case. The reason being, no other load case that follows the first load case, requires higher reinforcement than what is required by load case 1. Most likely the same thing is happening in your case. 
 2) All load cases are assigned for the concrete design in your model now. If you would try to increase loads in LC3 significantly, you could see that critical load case has changed for some members. 
 3) See the Technical Reference manual chapter 5.40 Load Envelope. Also see information can be found here: communities.bentley.com/.../2042.aspx 
 It is not necessary to use load enevelopes. 
 Regards, 
 Modestas

Modestas · Answer

Yes, the program is not able to find suitable reinforcement arrangement (the same is reported in the Output file) as the section is too small for the applied forces. You may need to increase the column dimensions or decrease the loads in such situation. 
 I looked into your model one more time and noticed that distance between the columns and beams is very low, so frame dimensions does not seem realistic. You probably need to review this.

Modestas · Answer

You need to double click on the SEISMIC X load case and select Loading Type as Seismic instead of None. The same has to be done for the load case SEISMIC Z. You always need to select Loading Type in order that load combination generator would consider those loads.