I am referring to January 2000 Newsletter describing modeling of sway brace assemblies in CAESARII.
I am bit confused about the functioning of sway braces ( not about the modeling technics which are elaborated with ease in the Newsletter). The sway brace exerts zero load on pipe in cold , then there is pre-set load which is to be overcome prior to any thermal movement. Now how this pres set load is generated ?(I am aware of only way to generate load is by way of using spring stiffness ).My question has some bearing on further questions below .

The pipe after overcoming the pre set load expands and the only load acting now is thermal displacement X spring stiffness. When the sway brace is to be installed in neutral position in operating case , as per my understanding only way is to release the spring ,i.e. bring it back to position without displacement . From here when the pipe will retract to Cold case position , ideally the spring displacement X stiffness shall be the load on pipe . Then how come again the load on pipe becomes = Pre-load + operating displacement * stiffness of spring ? It is represented by LOAD CASE 2- W+P1+F1+D2 ? How again F1 comes in picture ? PLEASE ADVICE.
regards,
bag_piper

Continuing above -
One more question - I have to give solution to a situation created by one detailed Engineering consultant ,where piping is exposed to different operating conditions . Liquid phase with around 300 Deg C , gas phase with around 450 Deg C . Piping is mostly on springs with springs installed on vertical long runs. During commissioning it is observed that there is gas and temperature is high . Hence vertical expansion is more , but the springs are designed for liquid load and hence pull heavily. There are horizontal branches and trunnions can also be placed here. Is it possible to advice on following , i.e. whether the situation would be improved or would be disastrous with following option :-
Put sway braces with calculated pre loads which will account for difference between liquid and gas weights shared at spring locations. Put sway brace in vertical, during gas service the pre load of sway brace will prevent heavy pulls from springs ?
But then the sway brace would have to be locked in liquid service or else there will be pre set load of sway brace in addition to liquid weight which may be problematic?
Regards,
bag_piper

Rather than figuring out what load (e.g., F1) is necessary to get the proper sway brace load, I would approach it in the "opposite" way - with displacement (e.g., D1). Find out where the brace moves to in the operating position and add this displacement set to a CNode on the sway brace.
You can also consider the sway brace as a bilinear restraint. Use a very large K1 and the proper stiffness for K2. The FY you define will set the break point from K1 to K2.

Talking about a system where I have to eliminate a mode of vibration in the vertical direction, but I also have a spring hanger ... Is there any reason for not using a sway brace ... I mean, can the sway brace disturb the behavior of the spring hanger, making its use prohibitive?