SECONDARY STRESSES IN BRIDGES

ALL METHODS PROPOSED FOR THE COMPLETE ANALYSIS OF SECONDARY STRESSES DUE TO THE RIGIDITY OF THE JOINTS IN BRIDGE TRUSSES ARE DESCRIBED. APPROXIMATE METHODS WHICH NEGLECT THE EFFECT OF THE WEB SYSTEM ARE NOT INCLUDED. A TYPICAL THROUGH RAILROAD BRIDGE OF SIX PANELS IS ANALYZED BY EACH METHOD IN TURN, USING UNSYMMETRICAL LOADING, IN ORDER TO TEST MORE THOROUGHLY THE ADVANTAGES AND DISADVANTAGES OF EACH METHOD. INFLUENCE LINES ARE DEVELOPED FOR THE SECONDARY STRESSES IN ALL THE MEMBERS OF THE MAIN TRUSSES, IN THE TOP CHORDS AS EFFECTED BY THE TOP LATERAL SYSTEM, AND IN A TYPICAL CROSS-FRAME. THESE INFLUENCE LINES ARE THEN COMBINED FOR THE PURPOSE OF COMPUTING THE MAXIMUM SECONDARY STRESSES IN CERTAIN TYPICAL MEMBERS. THE DIRECT STRESSES, TENSILE OR COMPRESSIVE, OF THE FIBERS PARALLEL TO THE CENTERLINE OF A MEMBER ARE CONSIDERED. THIS DISCUSSION IS CONCERNED WITH THE MAXIMUM VARIATION, AT THE OUTER EDGES OF THE MEMBER, AS FAR AWAY FROM THE CENTERLINE AS POSSIBLE, FOR IT IS THERE THAT STRESSES ARE MOST SEVERE. AT ANY PARTICULAR CROSS-SECTION OF THE MEMBER IN A BRIDGE, THE AMOUNT BY WHICH THE UNIT STRESS IN ANY LONGITUDINAL FIBER DIFFERS FROM THE AVERAGE UNIT STRESS FOUND BY DIVIDING THE TOTAL DIRECT STRESS BY THE AREA, IS CALLED THE SECONDARY STRESS OF THE FIBER. IT IS CONTENDED THAT THE CALCULATION OF SECONDARY STRESSES IN ORDINARY SPANS WILL SELDOM BE NECESSARY. IT IS GENERALLY BELIEVED THAT THE STRENGTH AND ECONOMY OF ALL BRIDGES WILL BE SUPERIOR TO ANY THAT MAY BE BUILT BY INCORPORATING THE SECONDARY STRESSES INTO THE CALCULATIONS.

  • Supplemental Notes:
    • Vol 89, PapER NO 1584, PP 1-149
  • Authors:
    • Von, ABO CV
  • Publication Date: 1926

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  • Accession Number: 00208532
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 18 1994 12:00AM