Blast Design - Pressure, Duration, Impulse

[michaelpjr]

Does a higher impulse always control blast design? Or should pressure and duration be considered more in depth?

Example: Here we have two blast scenarios. Let's assume for this case that the member in question is a simply connected wide-flange member.

Scenario 1:
p1 = 1.0 psi
t1 = 50 ms

Scenario 2:
p2 = 0.5 psi
t2 = 100 ms

Obviously, impulses for the two cases are equal. Does this mean that either is an acceptable design scenario?

What if d2 = 105 ms? Would the larger impulse control or does the longer duration (t2) have a more significant effect due to rigidity and stress-strain of the material with respect to time?

Does natural frequency play a part in choosing the design scenario?

Does material play a part?

 

[sjohnAM]

The natural frequency will play a large part. I think it's td/Tn that will tell you what will happen with the member. If that ratio is over 0.5, then the maximum displacement will occur during loading; otherwise, the maximum deflection will be the same as the member rebounds, without damping. Then the material will basically limit the maximum deformation that can be allowed.

 

[gyung]

I am still beginner of dynamics. Correct me if I wrong.

Duration of impact is related to natural frequency. The impact duration closer to the natural frequency will give the worst case, isn't it?

Various material could change the damping ratio (C), mass (M), and stiffness (K) of blast structure, they govern the dynamic properties of the blast wall?

Damping is also important, which dissipates the impact energy.