×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Jobs

Blast load conversion -STAAD time history

Blast load conversion -STAAD time history

Blast load conversion -STAAD time history

(OP)
Hi engineers,

Can any one suggest a method for converting the blast pressure into force (Time history)

The Explosion overpressure of 10kn/m2 (0.1 barg) combined with pulse duration of 0.2s.

In STAAD time vs force how to convert the pressure into force.

Size of the frame is 3m x 3m x 8m(height) all columns/beams 250mm sq tube.It is a open steel structure.

RE: Blast load conversion -STAAD time history

I'm not sure I've ever used STAAD for this purpose. Usually the time-history function in STAAD is for sinusoidal loads (from machinery in operation). It would probably be more worthwhile to (on paper) figure the response of your structure and load it that way in a static analysis. In that regard, STAAD can be helpful (not just for the static analysis). For example, you could do a modal analysis of the frame and if the results show a great deal of the mass participating in a single mode (i.e. 90% laterally; without seeing your frame, I will just assume this is a blast load adjacent to it), you could reduce the response model to a single degree of freedom system (i.e. SDOF). With that, you could then easily figure the dynamic load factor (DLF) based on charts that are in any Structural Dynamics text book. In my favorite text: 'Structural Dynamics: Theory and Computation', 2nd Edition, by: Mario Paz, this chart (for a triangular loading) is on p. 69. And the response factor varies (for a undamped system) from as little as 0.2 to just less than 2.0. Two is the maximum DLF for any system IIRC.

Of course, this is a pretty deep topic. With blast loading one of the first questions (for the client) is: what sort of damage are you willing to take? Do you want the structure just to survive without collapsing....or do you want it to come through with it largely intact? The cost difference between the two can be enormous. That question becomes important after the steps I discussed in the previous paragraph because then you get into design.....and then the question becomes: do you go elastic or plastic in your design? So like I said: there is a lot to it. A good book I read on this once had a flow chart to get through it.

I hope this helps.

RE: Blast load conversion -STAAD time history

Assuming this is a simple pulse, the load can be broken up into very small time steps down to zero in the form of a triangle. You have to figure out the appropriate time step required for the load. This triangle will give you the positive phase of the blast load only, of course. You need to be using the reflected and side-on pressures where each is applicable.

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!


Resources