Joint Shear Design (For SDC B and higher)
- Adisorn O.
- May 8
- 1 min read
In all SMRF from SDC B, ACI requires to check the joint shear strength. It's sometimes overlooked and we could end up with the SMRF with weak joint.
Since the beam-column joint has finite dimension, the joint deformation due to lateral displacement induces both moment and shear in joint. The bending moment can be taken care by the longitudinal reinforment and concrete as same as end of the beam. However, shear at joint must be designed to withstand such change in bending moment along the joint. ACI 318-19 chapter 15.4.1.1 requires checking joint shear as the step below:
Joint shear for internal beam-column connection can be computed from
Vuj = T1+T2-Vcol
T1 = 1.25*As_top*fy T2 = 1.25*As_bot*fy
Vcol = sum(Mpr_beam)/Lc (shear forces at beam ends are ignored as for conservative)
For external joint,
Vuj =T1 - Vcol
It's required that Vuj < phi*Vn (Phi = 0.75)
The nominal shear strength is given in ACI 318-19 Table 15.4.2.3
In a normal case, Vn around 15 to 20sqrt(fc')Aj can be used.