Hi!
I'm trying to run a model with seismic loads.
As I've never used the Spectrum Analysis method before (in previous models I just created the seismic loads on X, Y and Z as static loads based on the weigths involved and multiplying them by the correponding acceleration. I mean, I did it "by hand", but then I found out that I could create them as dynamic loads in a more direct way.)
In the "static way" model, I defined the loads like this:
LOAD 1 LOADTYPE Dead TITLE DEAD LOAD - D
SELFWEIGHT Y -1
FLOOR LOAD
YRANGE 1.19 1.31 FLOAD -0.313 GY
LOAD 2 LOADTYPE Soil TITLE X OPERATING EARTHQUAKE (OBE) - E0(X)
SELFWEIGHT X 0.0461
FLOOR LOAD
YRANGE 1.19 1.31 FLOAD 0.02 GX
LOAD 3 LOADTYPE Soil TITLE Y OPERATING EARTHQUAKE (OBE) - E0(Y)
SELFWEIGHT Y 0.0461
FLOOR LOAD
YRANGE 1.19 1.31 FLOAD 0.02 GY
On the other hand, I made a new model with the same structure, and defined the loads like this:
CUT OFF MODE SHAPE 30
LOAD 1 LOADTYPE Seismic TITLE EX (OPE)
SELFWEIGHT X 1
SELFWEIGHT Z 1
SELFWEIGHT Y 1
YRANGE 1.19 1.31 FLOAD 32 GX
YRANGE 1.19 1.31 FLOAD 32 GZ
YRANGE 1.19 1.31 FLOAD 32 GY
SPECTRUM CQC X 1.00 ACC SCALE 9.81 DAMP 0.05 LIN
0 0.0461; 0.0086 0.0461; 0.0255 0.0461; 0.028 0.0509; 0.0347 0.0576;
0.0469 0.0576; 0.0469 0.0458; 0.0598 0.0583; 0.1242 0.059; 0.1288 0.059;
0.1336 0.0844; 0.139 0.0864; 0.1512 0.0864; 0.2044 0.0864; 0.3344 0.0864;
0.3472 0.102; 0.3623 0.102; 0.3773 0.108; 0.3952 0.125; 0.4132 0.134;
0.4347 0.153; 0.6535 0.153; 0.6896 0.126; 0.7352 0.0968; 0.7874 0.0811;
1.0695 0.0811; 1.1764 0.0811; 1.4705 0.0746; 1.9607 0.0678; 2.3529 0.047;
4 0.0089;
The thing is, when I ask for the reactions in both models for Load 1, they are not the same. For instance, I get 31.75kg on the first one and 22.22kg for the other.
Does anyone know why I get this difference? Is any error on the input?communities.bentley.com/.../DYNAMIC_5F00_LOADS.stdcommunities.bentley.com/.../STATIC_5F00_LOADS.std