This is how we calculate the bearing moments when the bearing length is smaller than the bearing distance (this case isn’t in Design Guide 1, but we are just using basic forces equilibrium):
σ= Concrete stress= 0.3541 ksi
B= 16 in
N= 22 in
H= Bearing length= 2.7956 in
D= Bearing distance= 0.95*Depth/2= 0.95*12.1/2= 5.7475 in
M= Moment=Force*dist= (B*H*σ)(N/2-D-H/2)= (16*2.7956*0.3541)*(22/2-D-H/2)= 61.0464 kip*in
M_pM= Unitary moment= M/B=61.0464/16= 3.8154 kip*in/in
Same procedure applies for the transverse bending line MpN.