Overhead Crane Tractive/Longitudinal Force

[pioneer09]

I am looking at AISC Steel Design Guide 7 example 18.1.1. They show that the longitudinal/tractive force is 10% of max vertical load per wheel. Then as you look into the design guide the bumper force is 2x the tractive force.

The question I have per my example if this seems correct:

Say (2) 30 ton overhead cranes in a crane bay with max wheel load of 42k

-Longitudinal/tractive load= .1*(42k/wheel)
=4.2k/wheel
= 16.8k (total due to 2 wheels per crane)

- Bumper force=2*(tractive force)
=2*(16.8k)
=33.6k

Thus the final crane x-bracing to be designed for is due to a maximum horizontal force parallel to runway equal to 33.6k.

Do you typically only design the crane wall braces for longitudinal/tractive forces or do you have to design for the the maximum bumper force.

 

[msquared48]

That's not how I read the problem since the bumper is an energy absorbing mechanism. That force will never get to the bracing.

Hence, I think the bracing should be designed for the 16.8 kips.

Mike McCann
MMC Engineering

 

[CTW]

Using the bumper force as twice the tractive force is what DG07 recommends the designer assume for wood or rubber bumper blocks in the absence of specific data. Well actually it states to use the maximum of twice the tractive force or 10% of the entire crane weight. But to answer your question, you would use the maximum bumper force provided by the crane supplier.