×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Static Seismic Analysis Load Cases

Static Seismic Analysis Load Cases

Static Seismic Analysis Load Cases

(OP)
Previously I've dealt with piping systems in relatively low seismic zones so horizontal acceleration by itself was considered. In a new project with much higher seismic values we'll be looking to combine the horizontal and vertical components. Based off the Caesar II user guide, the load cases (shortened/condensed here) are intended to be:
L1 = Operating
L2 = Operating + U1 (horizontal)
L3 = Operating + U2 (vertical)
L4 = Sustained
L5 = L2 - L1 (algebraic)
L6 = L3 - L1
L7 = L5 + L6 (SRSS)
L8 = L4 + L7 (abs or scalar)

My questions:
1) The Caesar II user guide has another example where the operating case as "Operating + U1 + 0.67U2". Is there any difference in stresses/restraint loads between this load case and the method shown above? If so, what drives the decision to use either method?
2) I assume the L7 SRSS case (combining U1 & U2 before adding to the sustained) is another intermediate case that can be suppressed in the output (no restraint forces, displacement, or stress values to review). Is this accurate?


Thanks,

RE: Static Seismic Analysis Load Cases

The way EQ loads are combined does depend on the local EQ loading code and the piping code. B31E has some guidance.

EQ Load values and combinations for piping stress check and the structural design of supports and foundations maybe quite different.

RE: Static Seismic Analysis Load Cases

(OP)
So with regards to pipe stress, is there a difference between using an SRSS combination like my example above or using "Operating + U1 + U2"?

RE: Static Seismic Analysis Load Cases

Why are you not using the 100/30/30 rule for combining horizontal and vertical seismic effects?

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close