accidental impact loading

[oneintheeye]

has anyone any experience of designing for the above. I am primarily looking at impact loading from large vehicles on concrete structures. I can estimate the impact force but how does this transfer through a structure (concrete). Designing as static loading is i believe conservative as it does not take in account the time dependant nature of impacts.

 

[frv]

The time of the impact is reflected in the magnitude of the load. i.e. very brief impact means a very high static load.

Others on this forum have suggested using energy methods to determine the forces on a structure in situations like these. Equate the kinetic energy of the impacting vehicle to the strain energy in the member under consideration. This should provide you with the deflection and, subsequently, design forces. Obviously, you must make several assumptions along the way (e.g. point of impact).

 

[miecz]

AASHTO Section 13 has a method for loads to highway railings, including solid concrete parapets.

 

[oneintheeye]

yeah been through the equililent in UK but it doesnt help my application. Can you explain further frv?

 

[csd72]

Two things to look at, design the structure to take a reasonable level of impact and then to make sure the building does not progressively collapse due to a larger impact.

 

[frv]

Here's one of the threads.. I think there are a few more. I direct you to these, as the energy compatibility idea is not mine.

http://www.eng-tips.com/viewthread.cfm?qid=155771&page=1

But I believe I may have been be mistaken in my previous post, the kinetic energy is converted to potential (as in spring) energy in the structure.

 

[oneintheeye]

if this changes anyones opionions this is a barrier to take impact. Much larger than traditional and a bit out of ordinary. Its to protect another structure from deliberate ramming. Dont ask!