With a own simple example i have made a dynamic run with one spectrum X.
Restraints are :
Node 10 Anchor
Node 50 X-Stop
Node 60 Z- Stop (Vertical)
Node 70 Anchor
Nodes 50,60,70 in a higher floor Z > as Z node 10.
First calculation a Single Response Analysis.
That mean all restraints becomes the same spectrum X.

Input in Spectrum Load Case 1 :

Spectrum Factor Dir. Start Node Stop Node Incr.
X 1 X

Result: max DX = 1.47 mm


Input in Spectrum Load Case 2 :
Spectrum Factor Dir. Start Node Stop Node Incr.
X 1 X 10 10 1
X 1 X 50 50 1
X 1 X 70 70 1

Result: max DX = 3.59 mm
Questions :
1. For a single response analysis are the input in load
case 1 without start/stop nodes correct ?
2. Is the input in load case 2 likewise load case 1 ?
Why then different DX results ?

The backround my question is :
For a Multi Response Analysis a have different floors with different spectrums (X at node 10; X with Factor 1.5 at node 50,70).
Example :
Floor 1 Anchor Node 10
Floor 2 Anchor Node 70
X Stop Node 50


Now i have also here 2 possibiltys

Input in Spectrum Load case 3
Spectrum Factor Dir. Start Node Stop Node Incr.
X 1 X 10 10 1
X 1.5 X 50 70 20
Result: max DX = 3.79 mm


or :
Input in Spectrum Load case 4
Spectrum Factor Dir. Start Node Stop Node Incr.
X 1 X 10 10 1
X 1.5 X 50 50 1
X 1.5 X 70 70 1
Result: max DX = 4.92 mm

Here also different results ( same node).
Sometimes the restraint node numbers 123 , 167, 189, 193.
(Floor 1) what input correct ?

A.) Start node 123; Stop node 193 ; increment 1 (one line)
B.) or every node one line ?

The are different results !!!

If you invoke the ISM (Independent Support Motion) procedure (by defining restraint groups) then you must also define the "psuedo-static" anchor displacement value. If you leave this displacement value blank, CAESAR II will compute a default value based on the last spectrum value defined. So in actuality, your cases 1 and 2 above are really different.

Also note that when you specify a node increment of 1, you're still only loading the restraints in the "start - stop" range, even though you're incrementing the node numbers by 1.

In load case 2 i have set now in the 3 input lines "pseudo-static" anchor movement to 0 (zero) and not as empty field as before.
In the control Parameters i set the Include pseudo-static anchor movement to "YES". Also i did try here with "NO" i got the same results.

The results DX are the same as before (maxDX= 3.59 mm).

I think Caesar do allways a anchor movement effect, if more as on line input in the load case (see load case 2)!
Not respected Control Parameter "YES or NO" or i have only one spectrum X.

So my results !

Can you send the entire job to coadetechsupport@intergraph.com?
I'd like to look at all of it.
Add my name in the message. Loren will see that I get it.

Ernst,

Two issues play in these results – 1) spatial combination and 2) pseudostatic component

1) All four load cases define the same shock. But each separate spectrum entry (Shocks #1 & #4 each have one spectrum, Shock #2 had three and Shock #3 has two) is calculated independently. So while Shock #1 calculates response to everything happening at the same time, Shock #2 will calculate three independent events (10 wagging and 50 wagging and 70 wagging) that are then summed in some manner – either SRSS or absolute (here it’s SRSS) – to develop the total response. In my mind, the latter approach would consider node 10 deflecting to the right while node 50 deflects to the left; the former approach has everything moving in the same direction. So I would not expect your first three shock cases to produce the same results.
2) Now Shock #2 and Shock #4. When a single shock does not include the entire system, the relative deflection of different support groups (grouped by the shock spectrum) is a major contributor to the total response – usually much greater than the inertial component. Both Shock #2 and Shock #4 have the same three spectra. Shock #2 has 0 deflection defined for all supports in the group (entered in the last column) while Shock #4 has those three items undefined. Where no deflection is identified, CAESAR II will calculate the deflection. The lowest mode of vibration is controlled by displacement and this displacement is derived from the lowest frequency in the appropriate shock spectrum. You specify frequency versus acceleration. Displacement = acceleration/(2*pi*f)^2. Node 10 in Shock #4 shows a displacement of 506.6 mm; that equals 200(mm/sec^2)/(2*pi*0.1Hz)^2. The displacement report clearly indicates this total response is controlled by this pseudostatic component.

The Control Parameters tab has settings for the spatial summation and pseudostatic summation method and a pseudostatic on/off switch.

Dave,
Thank you for the answer.
But this was all clear for me.
The typical floor response spectrum beginns with a verly low frequency
about 0,1 HZ with a low acceleration.
Its clear this frequency with a low acceleration will give big
displacement (pseudostatic anchor movement).
If the user beginn his spectrum input at about 1 Hz, then the pseudo anchor movement much lower.
We to consider anchor movement from a spectrum with a frequency
at the ramp to the first big acceleration in the spectrum and not the first input cell in the spectrum.

Dave,
The importend point in this discussion are the following:
If we have two shocks
- spectrum X at the lower floor
- spectrum X1 at the higher floor

spectrum X act on the support nodes (lower floor) 10,120,150 (dependent) spectrum X1 act ont he support nodes (higher floor) 115,125 (dependent)

With this nodes numbers the user must more as one cell for the spectrum X
write in the spectrum load case.
X 1 10,120,10
X 1 150,150,1
X1 1 115,125,10
This is then a independent shock ( because 2 cell input for X and not one input cell for X)

Its clear, we can solve this with the right node numbers (support/spectrum to attach to)create in the model, but this is very circumstantial.

Ernst,

As long as you don't miss any support points, the shock definition need not be defined on one line of input. So, assuming your model has no other supports between 120 and 150, these two sets are the same:
-1-
Spectrum:X Factor:1 Start Node:10 Stop Node:150 By:1 Anc Move:0
-2-
Spectrum:X Factor:1 Start Node:10 Stop Node:120 By:1 Anc Move:0
Spectrum:X Factor:1 Start Node:150 Stop Node:150 By:1 Anc Move:0

However!
Note that I included the anchor movement. Leaving that off will have CAESAR II calculate this value based on the entered spectra.

The various combination methods defined in the Control Parameters will affect the total response in -2- above. If you leave the default directional combination method to SRSS, the response from the shocks will be the same for -1- & -2-. I cannot say -1- & -2- will be the same for absolute summation. Missing mass and anchor motion combination methods may cause differences between -1- & -2- as well.