Computer Plotted Prestressed Concrete Design Charts

A computer-prepared and -plotted system of graphic design aids for standard prestressed concrete sections that permits an exact, immediate and complete design of any uniformly loaded simple span is described. The system, termed Speed Graphs, consists of a set of design charts that outline visually the interaction of all design parameters affecting prestressed concrete design—prestress force, camber, release strength, top tension, bottom tension, deflection at various stages of loading, ultimate strength, shear steel required at d/2 from the face and at the quarter points, and by the minimum shear steel equation. Developed initially for twin tee sections, the system has been extended to single tees and highway bridge girders and is also applicable to beams. Speed Graphs can be prepared for composite or noncomposite sections of stone or light-weight aggregate and can be made to include partial prestressing (variable allowable bottom tension).