|There is something wrong in this picture. Can you see the welds that are missing?|
The ever lovely and talented Mrs ERJ and I were in a very large (140,000 square feet) building yesterday. We arrived early and there was a lot of dead time between events.
Mrs ERJ caught me peering up into the steel-work. "Whatchya lookin' at?" she asked.
"Steel." I answered very truthfully.
|Source of image|
The roof trusses were designed as Fixed-Fixed beams. That means that the ends of the trusses transfer a bending moment into the supports.
|The tell-tale is that the flange-plates for the top stringer are MUCH thicker than the flange-plates for the bottom stringer.|
|Flange-plate for bottom stringer.|
The bottom stringer is in compression and nearly all of the load is transferred without creating bending loads in the flange-plates. They provide stability and ensure the ends of the butted up stringer beams do not shift.
|The metal on the left side of the flange-plate is about 50% thicker than the metal on the right side of the flange plate. The height of the vertical portion is also much taller on the left.|
Another clue is the beams are not as beefy further out on the span.
Did you find the defect?
Don't feel bad. I had all day to look at this structure.