Structural Analysis
Beams designs must meet the following requirements:
- Distribute the weight of one railing to no more than three beams, applied to the composite cross section
- Use section properties given on the Prestressed Slab Beams standard drawings. For the composite section, use gross section properties.
- Composite section properties may be calculated assuming the beam and composite slab have the same modulus of elasticity (for beams with
< 8.5 ksi). When determining section properties, do not include haunch concrete placed on top of the beam. Section properties based on final beam and slab modulus of elasticity may also be used; however, this design assumption must be noted on the plans. - Live load distribution factors for shear and moment are available from the Bridge Division.
- The live load used to design the exterior beam must never be less than the live load used to design an interior beam.
- Do not take the live load distribution factor for moment or shear as less than the number of lanes divided by the number of girders, including the multiple presence factor per Article 3.6.1.1.2.
- When prestressed concrete deck panels or stay-in-place metal forms are allowed, design the beam using the basic slab thickness.