DESIGN FOR LONGITUDINAL REINFORCEMENT

BOTTOM LONGITUDINAL REINFORCEMENT

AASHTO 9.7.3.2 specifies the formula when designing bottom longitudinal reinforcement:

• For primary reinforcement perpendicular to traffic:

               

• For primary reinforcement perpendicular to traffic:

               

where S = the effective span length taken as equal to the effective length, (mm)

TOP LONGITUDINAL REINFORCEMENT

The top longitudinal reinforcement focuses near concrete surfaces exposed to temperature changes for shrinkage and temperature stresses.

AASHTO 5.10.8 provides the condition to follow for top longitudinal reinforcement

                    

where:
           
                  


  = area of reinforcement in each direction and each face

b        = least width of component section (mm)

h        = least thickness of component section (mm)
     
      =  specified yield strength of reinforcing bars

In addition, the maximum spacing of temperature and shrinkage reinforcement must be the smaller of 3 times the deck thickness.