Design of concrete foundation for impact load?
Design of concrete foundation for impact load?
(OP)
HI all.
I am looking at the design of a concrete foundation to resist a sudden "impact" load from a cable connected to the concrete. I have the load and decceleration values, so I can calculate the force applied to the concrete.
My question is is it conservative to assume a static load application of the calculated force onto the concrete foundation? the event is dynamic, but not recurring, or reversing. Once the load has peaked, it dies off very quickly to zero. The entire event lasts about 1-2 seconds maximum. Doing an assumed static analysis will obviously be much easier than some form of dynamic analysis. Oh, I forgot, this is not part of a structure, so I have no other interactions other than soil response.
Thanks.
I am looking at the design of a concrete foundation to resist a sudden "impact" load from a cable connected to the concrete. I have the load and decceleration values, so I can calculate the force applied to the concrete.
My question is is it conservative to assume a static load application of the calculated force onto the concrete foundation? the event is dynamic, but not recurring, or reversing. Once the load has peaked, it dies off very quickly to zero. The entire event lasts about 1-2 seconds maximum. Doing an assumed static analysis will obviously be much easier than some form of dynamic analysis. Oh, I forgot, this is not part of a structure, so I have no other interactions other than soil response.
Thanks.






RE: Design of concrete foundation for impact load?
RE: Design of concrete foundation for impact load?
The load I would apply would be an equivalent static load calculated from the dynamic loading. I know the mass, velocity and decceleration, so I can calculate the maximum force.
I understand your concern about the sping action of the cable. However, in this case the length of cable is short. I don't feel that spring action would have that much effect in this situation. Though I will get out some of my old dynamics texts, if I can find them, and give myself a quick refresher on the subject.
RE: Design of concrete foundation for impact load?
RE: Design of concrete foundation for impact load?
Deflection max= deflection static + deflection dynamic.
Dynamic deflection is obtained from the block with a spring attached to it (from the old dynamics class)and your values.
This is not the only method to do this. Some years back we had to look into a precast panel on a parking garage that an elderly man had rammed with a really big luxury car. I used the method above and my co-worker checked it with some kind of work dissapation method. My value was a load about 5*the weight of the car. With his method it was somewhere about 3.5*weight of car. We used his method.
I am curious, are you doing a bridge retrofit. I have seen cities beginning to strap precast stringers on bridges together over their supports since the Oklahoma barge accident.