the x is the column.. the vertical are purlins on top of the rafters with roof sheet connected to the purlins. May I know what is your meaning of "laterally restrain themselves via weak axis bending"? The column themselves support the rafter so the rafter is stable.
x---------x---------x
|...
Actually the "secondary beams" are just C-purlins welded 23.5" on top of the primary wide flange which functions as rafter of a gable joined at the middle with center ridge.. and the roofing used will be light sheeting.. but when the wind bears down on the roof sheet such as during hurricane...
I said framing at one side only. This is the same as framing in eccentricity.. because the primary wide flange would twist to the right slightly if there is only one secondary beam framing at the right side with no beam on the left. This is called eccentrically.. is it not.. what else do you...
For secondary wide flange that frames into the primary wide flange at one side only.. it sure can introduce torsion.. is it not.. so I guess the preference for larger values of Iy/Wy looked for in steel column design is also good for beam torsion resistance. Do you handle torsion by looking for...
Is the Ix or Iy axis in the moment of inertia or/and the Wx or Wy axis in the section modulus of the wide flange has more to do with torsion resistance? Which, Ix, Iy, Wx, Wy is more related to torsion resistance?
See the animation of the torsion in:
https://en.wikipedia.org/wiki/I-beam
Most...
Hoops around columns enclosing main longitudinal bars at the corners were required to have both 135 degree turns at the ends. But it's difficult to turn them both 135 degrees at construction site and for vibrator to get inside so in the Philippines. We usually have only one turn 135 degrees and...
The following is the moment frame you said to draw in Etabs.. I applied USB97 lateral load..
Fixed based:
Pinned based:
What all will be revealed. If you replaced the curved beam with straight beam. The frame would still drift. So how can beam cause drift.. Unless the following...
You mean like the non-reversing hinge on the right? So the beams must be strong flexurably to avoid more drift and lateral shear force bending it more. It's from http://www.nehrp.gov/pdf/nistgcr8-917-1.pdf
Or (don't miss above message) let's take an obvious example of a structured that is completely braced frame or the column is infinitely rigid and column can't deflect (just for sake of discussion). When the beams deflect from load.. this can cause drift, right? (or no?).. And in seismic...
We mostly are given the above image.. where the columns swaying is what rotates the joins elastically or inelastically.. can you give references or image where the beam deflections alone can contribute to plastic rotations? I just want to picture it in my mind. But when beams deflect in the...
but the contribution to plastic rotations is due to both column and beams at the joint.. so even if the beams deflect more and drift is more.. it is still the contribution of both column and beam to plastic rotations.. you said it is seismic story shear force that causes inelastic beam...
Oh.. I thought it's mostly RC column that controls the drift.. we talked about fixed bases and how making the column sizes bigger can control drift better.. how column is good for drift control.. so the beam is the hidden drift master after all...
Hmm... the consequence seems to be that in...
What? You don't mention about beam. You mean in reinforced concrete the major contributor to shear mode of drift is column... or
* in reinforced concrete, column bending is the largest contributor while beam bending is the smallest.. ?
opposite to that of steel where
* in steel, beam bending...
Thanks a lot Kootk! Many papers and references begin to make sense.
Do you know of a company outside the Philippines who can do seismic analysis by giving them the exact sizes of the members, rebars, live load.. soil condition etc.? In my country. No one even knows how to manually compute for...
forgot to ask this above
If you will see in the following https://courses.cit.cornell.edu/arch264/calculators/seismic-wind/index.html
the seismic story force of the second and third floor of a 3-storey is much more than the seismic story force of a 20-storey building. This means the beams of...
I live in the Philippines. Here we rarely use shear wall buildings.. most just moment frames.. but here's the scary parts. We don't have course in structural engineering. So almost all so called "structural" engineers are just operators of cad and some civil engineers and even plumbers who...
Remember my building has probable moment shear taken up by Vc + Vs intead of Vs (stirrup) only. It is designed for 5 storey but I only built 3. So not building it higher would maybe compensate a bit. I don't trust carbon fiber (these are installed).. but it the same carbon fiber used to retrofit...
I'm asking this because some buildings are designed for say 5 storeys but only 3 storeys built in the meantime.. so the columns are bigger than for a 3 storey. So in cases like this. The moments of the beam ends would be less. For a given seismic activity say Magnitude 7. There is less rotations...
I notice in frame analysis that if you make the columns twice larger in special moment frames.. there is lesser moments at the beam ends.. this result in higher seismic activity before reaching probable moment strength Mpr. So if money is no object like important institution like hospitals...
