Hi, i have a small project in mechanical design with a frame that is supported i

Question

Hi, i have a small project in mechanical design with a frame that is supported in the corners, with a distributed load over the top. We have had the basic with T fillet welds and lap welds though I am having problems applying it. below is the frame.

I am thinking that I need to calculate the shear forces using a simply supported beam from the side and the front to get the relevant forces present at each weld. The entire top surface has a distributed load of 800kg instead of a point load, where the load crosses the weld. The frame is stiffened by U profiles, that have a fillet weld on the side and a lap weld over the top. Any ideas or help would be appreciated, because i just cannot see it.

Thanks

Explanation / Answer

This frame is similar to that of a ladder chassis frame used in trucks.

For this kind of problems, divide the entire load into 2 halves.. so that side frame will take a load of 400 kg each..

Maximum shear stress or maximum von-misses stress will be obtained on the side frame itself.

As you have mentioned that it is supported at corners, so it will be a case of simply supported beam.

Calculate the moment of inertia for a L shaped frame..

Then subsitute that value in the equation

sigma / y   =   M   /   I

sigma = M / Z

sigma will be the stress

Z is the section modulus,, u can find the formula for that in google

M is the maximum moment.. obtain it from bending moment and shear force diagram

sigma will be stress

at the points where welded joints are applied,, make sure that sigma should be less than the weld strength at that point..

take some factor of safety also

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