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!
  • Students Click Here

*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

The Total operating weight of permanent equipment

The Total operating weight of permanent equipment

The Total operating weight of permanent equipment

Guys, As per ASCE_7-05, clause 12.7.2 "Effective Seismic Weight", The Total operating weight of permanent equipment should be considered in the earthquake analysis. My question is, in case those permanent equipment have both static weight and continues dynamic loads, should i consider those dynamic loads as part of the "Total operating weight" or neglect the dynamic and consider only the static weight of the equipment?.

RE: The Total operating weight of permanent equipment

The real driver of that provision is the mass of the equipment at the time of a seismic event. I think the reason they use total operating weight is to ensure you do not penalize your building unduly nor that you "miss" mass that will likely be in place during an event. To demonstrate the difference: suppose you have a tank and pump in your building, for overflow reasons the tank has a 1000 gallon capacity but in the normal mode of operation the take will only have 500 gallons in it. In this case the seismic analysis should have the weight of the tank, the pump, and the 500 gallons of liquid. You should design the gravity system for the 1000 gallons of liquid but the probability that the tank will overflow at exactly the same time as the earth starts to shake is very low. I would suspect in most cases the interaction between the building response to a dynamic force of equipment and the building response to ground motion is negligible, so you can ignore the equipment dynamic forces in the seismic analysis.

RE: The Total operating weight of permanent equipment

Thanks RobertHale, appreciate your help.
In fact i am thinking the same.. However, i want to be 100% sure that the interaction between the building response to a dynamic force of equipment and the building response to ground motion is negligible. i would appreciate if you can refer me to a book or code that discuss this matter.

RE: The Total operating weight of permanent equipment

The operating weight is simply that....the weight. Dynamic loads are loads generated by the equipment....not the weight of the equipment.

If the equipment requires liquid to operate, the weight of that liquid should be included in the operating weight.

The reason that dynamic loads from equipment are not included is due to a couple of things.

Low probability. This can be seen in various load combinations. The odds of the design seismic event occurring simultaneously with maximum equipment dynamic loads is probably extremely low. (You could make a case for a certain percentage of the dynamic load in addition to seismic load.)

The other reason is that considering dynamic loads could actually reduce the effects that seismic motion has on the structure. Depending on the nature of the dynamic loads, they may add damping or affect the period of the structure.

RE: The Total operating weight of permanent equipment

I'm not sure about the type of dynamic equipment you are dealing with, but most industrial equipment which generates dynamic loads is vibrationally isolated from its supports, and likely wouldn't contribute to any seismic load increase. Larger, intermittent, unintended loads, like strip cobble in a roll-forming line, are so infrequent they would almost never (in a million years?!) coincide.


RE: The Total operating weight of permanent equipment

We have had similar considerations. Consider a tank or bin that normally runs low but occasionally must run high. In our case, the conveyor below a bin keeps the bin low. However during some sort of temporary shut down, trucks are allowed to continue filling the bin. The bin is sized for a certain time length of shut down. In our case this amount of time may be perhaps an hour until the bin is filled.

Does it matter if this happens only once a year? once a month? once a week? or several times a day? At some point we had to acknowledge that this is a normal operation load. If so, then the whole contents must be considered.

Personally, I would like to find a reference which can define the difference between such an upset case and an operating load.

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


White Paper - Strategies to Secure Connected Cars with Firewalls
White-hat hackers have demonstrated gaining remote access to dashboard functions and transmissions of connected vehicles. That makes a firewall a vital component of a multilayered approach to vehicle security as well as overall vehicle safety and reliability. Learn strategies to secure with firewalls. Download Now
White Paper - Model Based Engineering for Wire Harness Manufacturing
As complexity rises, current harness manufacturing methods are struggling to keep pace due to manual data exchanges and the inability to capture tribal knowledge. A model-based wire harness manufacturing engineering flow automates data exchange and captures tribal knowledge through design rules to help harness manufacturers improve harness quality and boost efficiency. Download Now
White Paper - What is Generative Design and Why Do You Need It?
Engineers are being asked to produce more sophisticated designs under a perfect storm of complexity, cost, and change management pressures. Generative design empowers automotive design teams to navigate this storm by employing automation, data re-use and synchronization, and framing design in the context of a full vehicle platform. Download Now
eBook - Simulation-Driven Design with SOLIDWORKS
Simulation-driven design can reduce the time and cost of product development. In this engineering.com eBook, we’ll explore how SOLIDWORKS users can access simulation-driven design through the SOLIDWORKS Simulation suite of analysis tools. Download Now

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