Load Path Verification

[Refaat]

Dear Colleague

Greetings

(File 00) is a multi-story building (five floor) while (file 01) is the first floor of the building saved as substructure.

1. When I checked the reaction value (FZ) in the file (00) at nodal support no (2914), for combination load case (Ultimate), the value was (50.81 T).

Since all floors are identical then the reaction from each floor will be (50.81/5 = 10.162 T).

Whereas the reaction value (FZ) in the file (01) at the same nodal support was (8.05 T).

If you compare the obtained reaction value (FZ) of first floor from two file (00 & 01) = (10.162/8.05 = 1.26)

So, this percentage (26%) is high and can effect in the reality of calculations. Also knowing that if you increase the number of floors then this percentage will be also increased.

May I get clarification of this matter?

2. In the attached capture (00), (Fx) for each floor is approximately same value (10.19 T) except the first floor (2.52 T).

Pls any explanation?

https://www.mediafire.com/?8sc6kan38ssfkd9

Thanks in advance

Refaat

[Artur.Kosakowski]

1. I think there three reasons:

- the fact that self-weight causes shortening of columns which influences the distribution of loads from upper stories (this topic has already been discussed on the forum)

- the structure moves sideways rather than only vertically

- load distribution is based on stiffness of the elements of the model. Compare the reaction you indicated when you decrease Ig for slabs by 0.01 and then increase it 10 times

2. You need to check the "right" values 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Refaat]

Dear Artur

Thank you for your adequate response.

Could you provide me the right thread link which discusses (the fact that self-weight causes shortening of columns)?

With Regards
Refaat

[napooil]

http://forums.autodesk.com/t5/robot-structural-analysis/load-sequencing-construction-stages/m-p/4570...

[Refaat]

Thank you very much. I will take a look at it.

With Regards
Refaat