Beam Displacement - End translation
Beam Displacement - End translation
(OP)
Folks,
I am trying to determine how much longitudinal translation occurs in a beam when it deflects vertically. I am doing this to see if displacement under wet weight of concrete will cause the beam to move more than the tolerance of a standard hole beam.
I tried to do a quick run in ETABS/SAP, but they would give me only end rotation and not translation.
I am trying to determine how much longitudinal translation occurs in a beam when it deflects vertically. I am doing this to see if displacement under wet weight of concrete will cause the beam to move more than the tolerance of a standard hole beam.
I tried to do a quick run in ETABS/SAP, but they would give me only end rotation and not translation.






RE: Beam Displacement - End translation
RE: Beam Displacement - End translation
On the other hand, if your calculus is up to it, you could an exact analysis
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Beam Displacement - End translation
what difference is between the hypotenuse and half the length. That's for the midspan horizontal movement since it doesn't give he movement do to end rotation. Can you build the beam out of plate elements and load it? That should give you what you want from the software.
RE: Beam Displacement - End translation
reasonable approximation with relative ease. I just a quick check for a 20' beam. Assuming 3/4" max deflection due to wet concrete, I'm coming up with a lateral translation of 0.0023" - essentially 1/400"!!!
RE: Beam Displacement - End translation
I did a shell element model of a W24x55 beam (with proper web and flange thicknesses) spanning 34'. The wet weight of concrete was 600 plf. The shell element model was supported along the centroid using pin and roller.
The mid-span deflection of a W24x55 frame element with 6" mid span kink produced a vertical deflection of 0.48" and a lateral translation of 0.0287".
A shell element model produced a vertical displacement of 0.42" and a lateral translation of 0.0395" (top), 0.000615" (centroid) and 0.038255" (bottom).
RE: Beam Displacement - End translation
RE: Beam Displacement - End translation
RE: Beam Displacement - End translation
RE: Beam Displacement - End translation
A beam with pinned ends (no lateral translation) will still elongate, right?
RE: Beam Displacement - End translation
I agree. The movement of the top and bottom of the section are due a lot more to end rotation of the beam than to actual horizontal translation. The only place that undergoes pure translation is the neutral axis, which was extremely small.
RE: Beam Displacement - End translation
RE: Beam Displacement - End translation
Unfortunately it is not. It is the real deal. I cannot, however, go into specifics.
RE: Beam Displacement - End translation
RE: Beam Displacement - End translation
You will need upper and lower bound answers for beams with high and low side rolling tolerances.
Then again, the bolt might be hard on the edge of the hole to start with.
Sorry to sound so negative, but I get worried when we speak of such small dimensions. My own view is that steel is very forgiving and will try to do the job even if we don't quite get it right.
If you divide the beam into say six or eight parts ans calculate the deflections at each, and then the reduction in horizontal distance between the points you could calculate a new horizontal length between supports.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Beam Displacement - End translation
Depending on the geometry and loads one component of longitudinal deflection could be larger. My guess is that for the beam in question the second component is more significant as StructuralEIT mentioned.
If you are using a computational software such as ETABS/SAP the first component can only be obtained if you perform a nonlinear analysis. The second component you have to calculate using the slope that the program calculates (or from beam theory).
Nagi Elabbasi
Veryst Engineering
RE: Beam Displacement - End translation