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 Concrete X-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 $f_c^{\text{'}}$
fc ́ < 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 interior beams must conform to Article 4.6.2.2.2 for flexural moment and Article 4.6.2.2.3 for shear.

Live load distribution factors for exterior beams must conform to Article 4.6.2.2.2 for flexural moment and Article 4.6.2.2.3 for shear, with the following exceptions:

When using the lever rule, multiply the result of the lever rule by 0.9 to account for better live load distribution arising from the beneficial torsional stiffness of the box girder system.
When the clear roadway width is greater than or equal to 20.0 ft., use a distribution factor for two or more design lanes loaded only. Do not design for one lane loaded.
When the clear roadway width is less than 20.0 ft., design for one lane loaded with a multiple presence factor of 1.0.

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.