portal frame

[newdawnfades]

Hi there.

When a simple portal frame has a lateral load applied at the top - is this technically
an axial load into the beam? so is the longitudinal or transverse reinforcement resisting this
load?

Thanks!

 

[KootK]

This is a concrete portal frame?

It is an axial load in the beam. The magnitude of that load depends on how it is delivered to the frame. For the sake of conservatism and simplicity, I'll assume that 100% of the load shows up as axial load in the beam and may be either tension or compression.

In tension, the load is resisted by longitudinal rebar. In compression, the load is resisted by both the rebar and the concrete. In both cases, it's important to recognize that the beam is a beam-column. In addition to axial load, It needs to resist transverse loads and applied moments and shears at the ends. These forces may necessitate transverse reinforcing.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[robyengIT]

I don't agree with KootK : it depends of the base and corner restyraints (sorry, may be, for the incorrect technical words, but I am not english as mother language). A lot of cases you can find in Kleinlogel manual. In principle, for me, there are no axial load but only moment load

 

[robyengIT]

in detail : RIGID FRAMES FORMULAS - Kleinlogel (Amazon)

 

[KootK]

I'm going to refine my answer. For a symmetrical moment frame, which is most of them, I see no need to design the beam for an axial load more than 50% of the lateral load delivered to the frame.

I believe that no axial load in the beam corresponds to the case where exactly 50% of the lateral load is applied to each side of the frame. That's rare.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[paddingtongreen]

I can think of no case where a force is resisted only by moments. I don't have Kleinlogel any more but there will be an moments and an axial force to carry the load to the far side column and more moments.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin