Hello,

I am running the time history analysis in CAESAR II for steam hammer analysis of Main steam piping of coal fired boiler. For defining the force sets in time history, there are various options provided in the CAESAR II technical manual. this was working well for the piping having straight legs. however, for the piping leg having skewed (running in 2 directions), the results are not coming properly. I am getting two different results, if the directions are defined at one force set having both the directions and two separate force sets having one direction per force set.

for example, pipe is running in -X,Z axis at an angle of 45Deg. (Y axis being vertical)
Force set Case 1:
(-0.707,0,0.707) acting at node 10 with force F1
Force set Case 2:
(-0.707,0,0) acting at node 10 with F1
(0,0,0.707) acting at node 10 with F1.

kindly clarify, which one is the suitable definition and why?

thank you in advance...

Your parenthetic term sets the direction not the magnitude.
For example, (-0.707,0,0.707) is identical to (-1,0,1).
Easiest change to get the second set to match the first - the time history input provides a scale factor, change your scale for the two entries in the second set to 0.707.

thank you Dave for the response !!!

I still have some doubt, its just for my better understanding...

1. the values, whatever we define in the parenthesis will not have any effect in force?
2. in the time history input, we are defining the scale factor for steam hammer forces with respect to the maximum unbalanced forces. is this values further scaled down to the direction cosine factor? will it produce the desired results?
3. what if the pipe leg having different directional cosines in two directions i.e (0.707,0,0.5). is it correct to reduce F1 by the factor of 0.707*F1 & 0.5*F1 and define independently in the force sets itself?

thank you

Three items in time history input affect the load magnitude and the force set direction is not one of them. The load magnitude is set by the product of 1) the force entered in the time history definition 2)the Force Set Force and 3) the Time History Load Case Factor
Run a small model to test this for yourself.