Spreader Beam 1

[STEVE97]

Is there a criteria or a rule of thumb on how long a spreader beam needs to be for a crane lift? I have always made the spreader beam at least 1/3 of the span of the beam being lifted as my length. I have a situation were I cannot do that and I was wondering if there is any criteria for stability and locating the C.G. of the pick. Please respond. Thanks all

 

[kslee1000]

Check with Mechanical Engineering forum, as it is usually fall under the ASME code.

 

[csd72]

This should not be based on rule of thumb but on the ability of the lifted beam to support itself.

 

[STEVE97]

The spreader beam will be able to support itself. The beam will be in compression due to the axial load induced be the rigging cables and will have a straight pull on the bottom with beam clamps. I am concerned about the stability of the member being picked. It is 128 feet long. If the spreader beam is not centered exactly about the center of gravity of the pick than the 128 foot beam could rotate causing rotation of the spreader beam and shifting weight on the briddle hitches. It seems that the longer the spreader beam the lower margin of error there is and the stability of the system increases. I was just wondering what most people use as a length on the spreader beam.

For example:

Beam to be picked is 128 feet long and weighs 55 kips. How long should the spreader beam on the rigging be?

 

[CTW]

What csd72 was referring to is the ability of the 128 ft beam to support itself when lifted. So the length of the spreader beam should be determined based on the location of the lift points on the 128 ft beam that keep the 128 ft beam from buckling under it's own weight.

 

[csd72]

STEVE97,

The whole purpose of a spreader beam is so that the cables to the lifted member are vertical and therefore do not induce additional bending/axial load into the member from their horizontal component.

Most designers will try to locate the lifting points at the location where the minimum stress is induced in the member (equating cantilever moments to mid span moments).