## CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

## CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

(OP)

Most codes cover the case of beams deficient in shear reinforcement only and usually they propose CFRP to add to the shear strength of a beam on top of shear rebar and concrete. What would be the response of a beam which has a shear force that is more than Vrd,max? usually this case is solved by jacketing the beam to increase it's depth, is there a CFRP equivalent solution?

## RE: CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

one could wrap the beam to add shear and bending stiffness/strength.

can you post a picture of the beam? is it open on all 4 sides?

is this a repair? or a retrofit for seismic?

## RE: CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

One would expect the concrete shear compression struts to crush and, thus, compromise the benefit of the FRP.

That technique should be equally effective with FRP. What you're doing with such a strategy is making it such that more stirrups cross each potential shear crack and, therefore, more smeared concrete struts contribute to the resistance of that shear. More smeared struts = lower average strut compression. This solution should be agnostic to whether your shear reinforcing is rebar are FRP so long as deformation between the two is compatible.

## RE: CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

## RE: CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

I didn't say that the strut spacing changed. What changes is the total width of smeared concrete struts that contribute to resistance at any given location where shear is considered.

## RE: CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

## RE: CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

## RE: CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

I think rapt is pointing in the wright direction.according to eurocode 2, memebers subjected to axial compression will experience enhanced level of Vrd,max. But this is if the provided axial compression is below 0.5fck. Beyond this limit the benefit start to decline gradually becoming zero at 1*fck. With externally bonded prestressed CFRP, the shear capacity can be increased while the constant moment type balanced load helping in flexure. I think this is the way.

## RE: CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

I may have misunderstood your original post. I thought that you were asking if it would be possible to improve Vrd_max by increasing the flexural shear depth of the section and jacketing it with FRP shear reinforcement. Which, of course,

wouldbe possible. Is it the case that you're actually asking for a solution that doesnotinvolve increasing the depth of the section?## RE: CFRP For beams that fail in diagonal compression of struts (Vsd>Vrd,max)

But you would never use a compression stress greater than about .45fck anyway due to non-linear creep effects.