MultiSpan Built Up Beam with Overlaps
MultiSpan Built Up Beam with Overlaps
(OP)
Not sure how to approach this. It's not 3 simple spans nor does it appear to be a multispan built up beam (Wood 2x). I'm trying to determine the loads on the posts supporting the beam. I can determine the loads based on the 3 simple spans and if the beam is continuous end to end but not sure how to go about a beam with splices over the supports as shown. Can anyone point me in the right direction to accomplish this.





RE: MultiSpan Built Up Beam with Overlaps
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: MultiSpan Built Up Beam with Overlaps
My intent is to determine the difference in reactions (load transferred to footings) of these two scenarios. For example, at Post 2 (see attached).
Thanks again.
RE: MultiSpan Built Up Beam with Overlaps
You could look at one beam system, determine the reactions from that, then reverse the reactions and add the two beam systems together. Or you could computer model it equalizing the deflections...
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: MultiSpan Built Up Beam with Overlaps
I am not sure how close to a correct answer you would get doing a double analysis and adding them together.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: MultiSpan Built Up Beam with Overlaps
RE: MultiSpan Built Up Beam with Overlaps
Thanks again.
RE: MultiSpan Built Up Beam with Overlaps
The splice at the support does affect the through-stiffness of the combined member so in effect, the splice at a support affects the distribution of moments and deflections along the span.
Think of it this way - say you have a beam made up of 10 2x members. Suppose ALL of them are continuous. You would definitely have a continuous beam and could analyze that as such.
Now assume ALL of the members are spliced at the support. Now you have nothing more than a simple span.
Now assume that you have SOME of the members spliced at the support. You now have something in between fully continuous and simple span.
The comments above are correct in that you have to assume only the through-members over the support in strength calculations.
But the number of splices, and positions of splices, create little weaker segments that affect the distribution of bending moments.
RE: MultiSpan Built Up Beam with Overlaps
RE: MultiSpan Built Up Beam with Overlaps
Summing the two systems would work if the two beamlines are not stitched together. However, if they are stitched, then an analysis based on equal deflections would have to be run to get the precise reactions.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: MultiSpan Built Up Beam with Overlaps
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: MultiSpan Built Up Beam with Overlaps