Secondary beam at lower level than primary beam.
Secondary beam at lower level than primary beam.
(OP)
Hi everyone,
Good Day,
My secondary beam is lower than my primary beam please see the sketch below if I use shear links to transfer secondary beam reactions to the top of primary, is it ok? Any other things to take into consideration?
Thanks in advance for your replies.
Good Day,
My secondary beam is lower than my primary beam please see the sketch below if I use shear links to transfer secondary beam reactions to the top of primary, is it ok? Any other things to take into consideration?
Thanks in advance for your replies.






RE: Secondary beam at lower level than primary beam.
Link
Page 42 and 43.
RE: Secondary beam at lower level than primary beam.
1) Put top steel in supported beam.
2) Run supported beam bottom steel over girder bottom steel.
3) Maybe comparability torsion reinforcement in the girder.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Secondary beam at lower level than primary beam.
RE: Secondary beam at lower level than primary beam.
1) For early stages of loading, there's torsion in the girder and some fixity in the end of the supported beam.
2) The amount of torsion will depend greatly on the supported beam's proximity to the columns supporting the girder. If the supported beam ties in at girder mid-span, there's probably considerable pre-cracking torsional flexibility available. If it ties in near a column, you'll develop large torsions in the girder.
3) With enough additional load, you'll morph away from the torsion condition and towards a pure tensile hanger situation similar to the OP's concept. At that point, the supported beam loses its fixity.
4) Getting form the torsion situation to the pure tensile hanger condition probably requires redistribution of two sorts:
4-1) Torsional cracking of the girder.
4-2) Opening up of a crack at the right face of the girder as shown below.
If this were my baby, and especially if it were in a corrosive environment, I would probably do the following:
1) See if I could deal with all of the hanger tension in just the stirrup legs adjacent to the right side of the girder. This ought to minimize crack width.
2) Put in some sleep easy minimum torsion reinforcing.
Much depends on the relative stiffness of the two beams. The greater the flexural stiffness of the supported beam relative to the torsional stiffness of the girder, the closer you'll be to a true hanger. And one nice thing about torsion is that, if you can tolerate a little torsional cracking, the torsional stiffness will diminish by something to the tune of 90% in an instant.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Secondary beam at lower level than primary beam.
Will be tough to do with the OP's primary beam BOTTOM at the same level as the secondary beams TOP.
struggle66, I am not sure of the spans and magnitudes of your loads in this, but in the past where the span/load configuration and repetitiveness justified it, I used some vertical PT bars and vertically 'stressed' the secondary beams to the primary beams.
RE: Secondary beam at lower level than primary beam.
My bad. Here, substitute carrier bar for girder bottom steel. Conceptually identical.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Secondary beam at lower level than primary beam.
RE: Secondary beam at lower level than primary beam.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Secondary beam at lower level than primary beam.
KootK,
I will provide minimum torsion bars in GIRDER. Maybe I will only use 40% or 50% yield strength of the bar and put more links close to the right face of the girder
Ingenuity,
Vertical PT is a good idea. Thanks
RAPT
Thanks I will make sure the force fullly develop.