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(OP)
Just curious about methods to analyze fork truck loading on elevated slabs (either concrete or steel). Typically we use the AASHTO method to back calculate uniform distributed loads. We have also used finite element modeling and toyed with the idea of using yield line theory.

Westergaard, a professor at the University of Illinois, issued a comprehensive report in March of 1930 to the Bureau of Public Roads "Computation of Stresses in Bridge Slabs due to Wheel Loads".  I believe Westergaard's report is the basis for the modern day AASTHO requirements. The AASTHO spec., unfortunately, has taken Westergaard's recommendations and converted them into engineering data that works only for truck loads and bridges. Building engineers must work with varying wheel bases, axle lengths and tire contact areas. You must go back to Westegaard's original report to find useful information.  You should be able to order this report thru your Public Library.

Ignore all the theoretical equations, unless you can understand them (I can't). You will find several useful charts. One will give you coefficients for calculating the maximum bending moments for the main steel as well as the distribution steel for both simply supported and fixed edge one way slabs. Others will give coefficients to calculate the additional bending moment due to adjacent wheel loads for both parallel and perpendicular arrangements.

Another will give you the theoretical negative moment when a wheel load approaches a fixed edge condition as P divided by PI. A fixed edge condition can be approached when the wheels perfectly stradle a rigid beam, supporting wall, etc.

If the wheel load is only on one side of a rigid beam or wall support, a report by Vernon Jensen, has determined that the theoretical negative moment would be P divided by 2 PI. This makes sense.

I have found these charts to be very useful for over 30 years in building design. They will give you quick, accurate answers without having to resort to a finite element model or other approximate methods. I hope this helps.

maiorano,

One of the really big thinks to look at with forktrucks on elevated slabs is the impact forces of starting and stopping the forktruck with a load on it.  That can induce quite a load into the elevated slab and requires lateral bracing of the framing.

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