This paper describes an innovative concept for assembling prestressed concrete box girders from a combination of precast, prestressed unsymmetrical sections and I-sections. This solution can provide many advantages over typical single-casting box sections. These include (1) external easily removable void forms, (2) simplified quality control and concrete surface inspection, (3) reduced weight for handling, shipping, and erection, (4) increased competition among bridge builders, and (5) possible elimination of the assembly gantry required for construction of segmental span-by-span box girders. Discussion includes implementation of the concept as a substitute for adjacent box beams assembled from standard AASHTO box sections or trapezoidal box sections. Design, production, and construction considerations are discussed. A numerical example for design of an unsymmetrical trapezoidal box girder bridge is presented.
