Earthquake load vs. Thermal expansion 2

[sveinho]

Hi,
I am calculating pipes for a geothermal power plant under external load (earthquake load). The question is do I calculate the thermal expansion and the earthquake load at the same time or do I calculate it seperately?

Regards,
Sveinho

 

[CRG]

What design criteria are you using? If it is ASME B31.1 or B31.3, you need to get a copy and read it. The code is clear on allowable stress for thermal induced loads, pressure, sustained, and occasional load. The code is not as clear as to how to calculate them. Then decide with your client on static or dynamic seismic calculation.

If B31.3 is used the most relevant part for you to consider is:
301.1 Qualifications of the Designer
The Designer is the person(s) in charge of the engineering design of a piping system and shall be experienced in the use of this code. ….
Your questions said you are calculating external loads. I recommend you run this question by the Engineer of record for the piping design. From your question, it seems that you do not meet the minimum qualifications required by ASME B31.3, and you will need to work under a designer that meets the requirements. This is the person you should ask.


Not sure on the minimum qualification requirement for B31.1 without doing a code review.

If neither of these codes (B31.1 or B31.3)are the design criteria, I would still recommend them as a guideline.

 

[bvi]

Seismic loads are combined with weight, pressure and other sustained load, and the combination of those are limited to the allowable stress for occasional loads. (1.2 times basic the allowable in B31.1, 1.3 times the basic allowable in B31.3). Stresses due to thermal expansion are considered separately.

 

[robinxie]

The thermal stress is considered as Displacement stress, and seismic as Occasional stress. They are calculated separately. I guess you should us B31.1 because it is a pipe for geothermal power plant, and should check Eq. 12 from the code.