SHEAR STRENGTH OF STIFFENED COMPOSITE BEAM

[airil]

Hi, Im Airil, doing a research on flexural strength of composite beam. Two beams were stiffened by C-channels at the lower flange to increase its ultimate strength. The beam was subjected to two point load, intentional to produce constant moment at the mid-span region. The problem was, due to the loading system, there was high moment-shear interaction at the points of each loading. It got worst as the influence of shear was high as the increase in ultimate strength was not followed by increase in shear strength (little increament in effective shear area).

QUESTIONS;
i) IS THERE ANY WAY I CAN CALCULATE THE CONTRIBUTION OF THE CHANNEL TO THE SHEAR STRENGTH OF THE COMPOSITE SECTION- the channel web was welded to the lower flange of the steel beam

ii)can I consider that the slab can carry 1/3 the applied shear stress

 

[ishvaaag]

I think a 3D model separating slab, beam and channel, then joinign by rigid links or so may give some idea of what happens. The more complex and fitting the behaviour the model, the better, but even line elements may give an idea of the behaviour.

The union between channel and beam may be modeled quite rigid to ensure common deformation, but the links representing the union through studs contrarily may need some flexibility (and slippage if feasible) be considered.

Then you can tune your model/s to the behaviour for further modeling.

How much shear the slab takes will depend on a number of parameters. I think I have seen in print to count even the 100% of the brute section of the uncracked slab. Normally won't be your case but in the continuity joint zones in continuous composite beams it the quite cracked concrete atop (in tension) will show quite poor contribution to shear capacity there.

 

[visitor]

You can find the shear at the channel using the equation,
F.A.Y/I ( where F= shear at the section, A = Area of the channel when you want to find the shear stresses at the interface, Y = distance of the centroid of channel from the centroid of composite section, I= Moment of Inertia).

There are procedures available in the British standard BS5950-Part1, for calculating the reduced flexural strength of the sections due to high shear . You can refer to that.

 

[WKTaylor]

Suggest You ask this question in the composites forum327. Regards, Wil Taylor

 

[Ingenuity]

wktaylor,

FTI....

unfortunately, "composites" for you aero's is different for us "structurals".

composites for "aero" is FRP (eg carbon, glass, aramid)

composites for "structural" can be FRP's but it most often means steel beam acting in structural action (composite action) with a concrete slab.

 

[Ingenuity]

wktaylor,

FYI....

unfortunately, "composites" for you aero's is different for us "structurals".

composites for "aero" is FRP (eg carbon, glass, aramid)

composites for "structural" can be FRP's but it most often means steel beam acting in structural action (composite action) with a concrete slab.