Minimum Shear Reinforcing - Prestressed Member
Minimum Shear Reinforcing - Prestressed Member
(OP)
Folks,
I have a question pertaining to the minimum shear reinforcing requirements for prestressed concrete members with fse > 0.4 fpu.
Section 11.5.6.4:
Av,min shall not be less than the smaller value from Eq. (11-13)and (11-14)
Equation (11-13) is 0.75 sqrt(fc′) bws/fyt but not less than 50 (bw * s)/fyt.
Assuming that 0.75*sqrt(fc') is more than 50, will the minimum be based on the min [ max(Section 11.5.6.3), Section 11.5.6.4]
In other words, if 0.75*sqrt(fc') > 50, then the minimum will not be based on 50 bw*s/fyt.
Please clarify.
I have a question pertaining to the minimum shear reinforcing requirements for prestressed concrete members with fse > 0.4 fpu.
Section 11.5.6.4:
Av,min shall not be less than the smaller value from Eq. (11-13)and (11-14)
Equation (11-13) is 0.75 sqrt(fc′) bws/fyt but not less than 50 (bw * s)/fyt.
Assuming that 0.75*sqrt(fc') is more than 50, will the minimum be based on the min [ max(Section 11.5.6.3), Section 11.5.6.4]
In other words, if 0.75*sqrt(fc') > 50, then the minimum will not be based on 50 bw*s/fyt.
Please clarify.






RE: Minimum Shear Reinforcing - Prestressed Member
RE: Minimum Shear Reinforcing - Prestressed Member
What you are proposing seems to be correct. As long as 0.75*sqrt(f'c) is greater than 50 then the governing equation in 11-13 will be:
Avmin=0.75*sqrt(f'c)*bw*s/fyt
This is compared with 11-14
Avmin=Aps*fpu*s/(80*fyt*d)*sqrt(d/bw)
So...
Avmin=min(0.75*sqrt(f'c)*bw*s/fyt,50*bws*s/fyt,Aps*fpu*s/(80*fyt*d)*sqrt(d/bw))
RE: Minimum Shear Reinforcing - Prestressed Member
your last equation seems still allowing 50*bws*s/fyt become the minimum, that for the case considered seems be the contrary in (11-13), that for some cases (that quoted here as of interest, is precluding such lower value in favour of a higher one. So I think as slickdeals proposes
min [ max(Section 11.5.6.3), Section 11.5.6.4]
is a better statement,
otherwise you may be meaning that the 50*bws*s/fyt ,is always to be available as the minimum code shear reinforcement for the case
RE: Minimum Shear Reinforcing - Prestressed Member
Avmin=max(0.75*sqrt(f'c)*bw*s/fyt,50*bws*s/fyt,Aps*fpu*s/(80*fyt*d)*sqrt(d/bw))
RE: Minimum Shear Reinforcing - Prestressed Member
Avmin=min[max(0.75*sqrt(f'c)*bw*s/fyt,50*bws*s/fyt),Aps*fpu*s/(80*fyt*d)*sqrt(d/bw))]
RE: Minimum Shear Reinforcing - Prestressed Member