impact loading
impact loading
(OP)
I have a heavy duty door, lets say 40kN. I have to design a stopper to qualify the door for design basis earthquake. Now, lets say I use the floor response spectrum, and it is acceleration of 1 g.
I need to find the design load for the stopper.
Now, I assume a force of 40kN (40/g*1g) applied during earthquake for 0.25s. So my impact load applied is 10kNs (Ft). Then door is traveling at constant velocity = mv, so velocity is 10kNs/40kNg=2.45m/s=V2,
Now assume my door stop deflects 5mm, use V1=0, v2^2=V1^2+2ax, I get deceleratoin of a=600m/s^2. Then v2=v1+at, t=0.004s. So, I assume the door will stop in 0.004s.
Ft=10kNs t=10/0.004=2500kN.
This is a huge load, 250tonn. Which is different from impact factor of 2. Is there anything wrong with what I did? Many thanks,
I need to find the design load for the stopper.
Now, I assume a force of 40kN (40/g*1g) applied during earthquake for 0.25s. So my impact load applied is 10kNs (Ft). Then door is traveling at constant velocity = mv, so velocity is 10kNs/40kNg=2.45m/s=V2,
Now assume my door stop deflects 5mm, use V1=0, v2^2=V1^2+2ax, I get deceleratoin of a=600m/s^2. Then v2=v1+at, t=0.004s. So, I assume the door will stop in 0.004s.
Ft=10kNs t=10/0.004=2500kN.
This is a huge load, 250tonn. Which is different from impact factor of 2. Is there anything wrong with what I did? Many thanks,






RE: impact loading
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: impact loading
RE: impact loading
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: impact loading
i think you should also worry about trying to restrain a large panel at a single point, or are you restraining the entire edge ?
RE: impact loading
I will try to restrain at single point, if not feasible an entire edge.
Greglock, what should be the expected stiffness of a steel block of lets say 3" x 6"
Thanks,
RE: impact loading
TTFN

FAQ731-376: Eng-Tips.com Forum Policies
RE: impact loading
RE: impact loading
RE: impact loading
RE: impact loading
RE: impact loading
People have been assuming that the door is a swinging type access door, but is that correct? This could also be a large "garage door" type that drops or a reinforced concrete door that slides. This will make a difference.
A drawing or sketch would help considerably.
Patricia Lougheed
******
Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.
RE: impact loading
I'm not exactly sure what you are trying to accomplish without a better description and a few detailed sketches. But, consider these things in your design and analysis: if you can do something to increase the time duration and distance of travel in the stopping process, you will significantly improve your conditions. With the door hinged on one side and the stop mechanism at one of the top or bot. corners of the other side, and the center of mass about in the center of the door, you will induce a considerable torsional action on the door structure, can it take that? However that might absorb part of the energy too. Think of most heavy door stop mechanisms, they travel some distance and are pneumatically or hydraulically controlled, the flowing fluid absorbs the energy, allows time and distance of travel. A mechanical system along the same lines, assuming your stopping mechanism is mounted on the floor at the lower corner of the door, might be a set of spring loaded wedges which absorb the energy through friction and move some distance, but tighten to absorb more energy per mm trraveled, as they move. There are also some helical springs made out of flat spring steel bar stock, not round stock, wound around themselves (volutes?). They tighten upon the outer coils as they travel and absorb energy by friction. There are also, off the shelf, rubber and hydraulic energy absorbing bumpers.