I have a question about unreinforced bearing for hollowcore slabs and precast solid slabs. Typically 3 inches of bearing is provided in the slabs without any additional shear friction reinforcing (in the solid reinforced slab case). ACI section 16 gives some guidance and sets a minimum of 2 inches of bearing for for solid or hollowcore slabs. However, I wanted to calculate the capacity of the connection as well.
I usually assume a continuous wedge with a 70 degree angle to the vertical would fail in shear from the edge of bearing, and then calculate the shear resistance of the failure surface, using the equation for concrete tensile strength of a stud in tension. (phi*Ao*2.8*L*Sqrt(fc')) - using Ao = area of concrete failure surface.
The forces to consider on the connection are the vertical reaction and also some volume restraint forces (usually assumed to be 20% of vertical)
Am I doing this correctly? How does everyone else calculate the strength?
I usually assume a continuous wedge with a 70 degree angle to the vertical would fail in shear from the edge of bearing, and then calculate the shear resistance of the failure surface, using the equation for concrete tensile strength of a stud in tension. (phi*Ao*2.8*L*Sqrt(fc')) - using Ao = area of concrete failure surface.
The forces to consider on the connection are the vertical reaction and also some volume restraint forces (usually assumed to be 20% of vertical)
Am I doing this correctly? How does everyone else calculate the strength?
