PROPOSED EQUATIONS FOR PRELIMINARY DESIGN OF CURVED BRIDGE SYSTEMS. THE DESIGN OF CURVED VIADUCTS

THE BENDING AND TORSIONAL STIFFNESSES OF CURVED GIRDERS ARE NEEDED IN ORDER TO USE COMPUTER TECHNIQUES TO ANALYZE CURVED GIRDER BRIDGE SYSTEMS. SIMPLIFIED DESIGN EQUATIONS ARE PRESENTED WHICH WILL PERMIT EVALUATION OF INTERNAL FORCES SO THAT PRELIMINARY GIRDER PROPERTIES MAY BE ESTIMATED. THE DESIGN EQUATIONS ARE BASED ON A STRAIGHT GIRDER ANALYSIS. THE MAXIMUM INTERNAL FORCES ARE EVALUATED AND MODIFICATIONS ARE THEN APPLIED TO ACCOUNT FOR THE CURVATURE OF THE GIRDERS. DISTRIBUTION OF THE LOAD BETWEEN GIRDERS AND THE VARIATION OF LOAD EFFECT FROM THE INSIDE TO THE OUTSIDE GIRDER ARE ALSO CONSIDERED. COMPLETE DESIGN EQUATIONS AND TALBES FOR MODIFICATIONS AND REDUCTION FACTORS ARE DESCRIBED. UTILIZING TWO INDEPENDENT COMPUTER PROGRAMS WHICH WERE DEVELOPED, THIRTY-SIX DIFFERENT COMBINATIONS OF SPAN LENGTHS AND RADII FOR A LOADED SINGLE SPAN GIRDER AND 108 DIFFERENT COMBINATIONS OF GIRDER NUMBERS, SPAN LENGTH AND RADII FOR A SYSTEM OF GIRDERS WERE STUDIED. THE LIMITATIONS ARE GIVEN FOR THESE STUDIES. THE INTERNAL REACTIONS FOR VARIOUS SPACING OF GIRDERS ARE COMPARED IN A TABLE. THESE VALUES INDICATE THAT AS SPACING OF GIRDERS INCREASES, THE VALUES OF INTERNAL FORCES CHANGE SLIGHTLY. A VARIATION IN GIRDER SPACING RESULTS IN A CHANGE OF GIRDER STIFFNESS. A SPACING FACTOR WAS OBTAINED TO INCLUDE THE EFFECT OF SPACING. THE EFFECT OF CONTINUITY OF SPANS WAS STUDIED. RESULTS INDICATE THAT CONTINUITY OF THE SPANS TENDS TO REDUCE THE INTERNAL FORCES. THE MAXIMUM VALUES OBTAINED FROM THE EQUATIONS SHOULD BE MODIFIED FOR EACH INDIVIDUAL GIRDER IN THE SYSTEM AND THE FINAL DESIGN SHOULD BE CHECKED BY A COMPUTER PROGRAM. A GENERAL EQUATION FORM IS PRESENTED FOR COMPUTING A GIVEN FUNCTION.