Yes, it does. You might get compressive forces where you don't want them. The flanges are shorter at the top of the T, which is positive for compressive forces. You might get unfavorable buckling or tipping. It depends on what load cases you have and how close you are to the limits for the beam.
Primarily, it's about ensuring it doesn't sag/bend downwards.
If it only concerns the deflection issue, it doesn't matter. The moment of inertia is the same in the y-direction. However, the risk of buckling is vastly different depending on how you orient the beam.
Tell me more.J justusandersson said:
Don't know how much you know, but in Eurocode 3, 1991-1-3, you can read about stability issues, it's called LT buckling (lateral torsional buckling). There you'll see that you need to check especially which side of your beam is under compression (buckling occurs in compressed parts). And since your cross-section isn't doubly symmetric for a t-beam, the load case and how you orient the beam becomes very important.ricebridge said:
But if you're only looking at deflection and you're far from any buckling limit, it's hardly critical in your case.
But the short answer is yes, it does matter, sometimes...
When testing for deflection, a very small part of the beam's capacity is normally utilized. Therefore, one can disregard a number of unpleasant issues that can occur at higher levels of utilization. The risk of buckling (deformation of the web) is greatest in association with tall and slender beams, such as in bridges and industrial buildings. The cause can be both too high shear forces and too high normal forces. High shear forces are often due to large spans. The risk of lateral-torsional buckling can be significant even in smaller constructions, depending on the type of beam and installation. T-beams are not particularly efficient in relation to their own weight; in that case, an I or H beam is better.