Hi dear friends. I have a big problem and I need your help, I've realized that the joint connection I've drawn (and it is made already) was (most probably) wrong. There is a plate that is bolted to two U beams and the plate is welded to a horizontal I beam at the top. Please take a look at the picture link below. Three of the bolts are for a U beam and three for the other (they are diagonal), top "dot" is the centroid of the welded I beam (there is the same plate at the other side of the I beam, so the system is symmetric wrt the I beam).(adsbygoogle = window.adsbygoogle || []).push({});

I don't have many tools at work, so I manually investigated the joint stresses at the top I beam (can anyone comment on the suitability of this method, what I did is I isolated the top beam in a complicated system because the program I use doesn't give joint stresses, then I found the joint stress and I assume this is the joint stress in the system).

Anyways, my main question is about bolts.To cut it short I'll try to show what I did for bending moment My only and for one of the bolts at the top. I found My as approx. +4500000Nmm. Then I've found the centroid of the bolted joint as (200,100). Now the tensile force due to My on the top bolt should be ((bending moment)*(distance from bolt to the y axis ))/(sum of all bolt distances to the y axis squared) which is

((4500000)*(50))/(50^2+0^2+100^2+50^2+100^2+0^2)=9000 N

Then the stress is 9000/144(bolt area)=62.5 mpa due to My.

But I didn't consider (where I did wrong) that the centroid of the I beam (where moments are applied to the plate) is not coincident with the bolt centroid. I don't know how this comes into play. There is a 180 mm distance between the bolt centroid and the I beam centroid. Frankly how does the moment from weld joint affects the bolts I can't really physically understand in my mind. Can anyone help? Thanks in advance.

http://i.imgur.com/SzgtYxy.png

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# Joint Stresses

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