PROCEDURES FOR DETERMINING THE MOST ECONOMICAL DESIGN FOR BRIDGES AND ROADWAYS CROSSING FLOOD PLAINS

HIGHWAYS CROSSING THE FLOOD PLAINS OF MAJOR STREAMS ARE COMBINATIONS OF BRIDGES AND APPROACHES EMBANKMENTS. THE DECISION AS TO WHICH PORTION OF THE TOTAL ROADWAY LENGTH SHALL BE ON BRIDGE AND WHICH ON FILL INVOLVES ENGINEERING ECONOMY AS WELL AS BRIDGE DESIGN. BRIDGES COST MORE PER UNIT LENGTH THAN APPROACH FILLS SO THAT, WITHIN REASONABLE LIMITS, THE COMBINATION OF SHORT BRIDGE AND LONG APPROACH HAS LOWER FIRST COSTS. ON THE OTHER HAND, THIS COMBINATION RESTRICTS THE CHANNEL AND DURING FLOODS RAISES THE WATER LEVEL UPSTREAM, WHICH MAY CAUSE DAMAGE FROM FLOODING. A SECOND AND INTERRELATED DECISION CONCERNS THE ROADWAY ELEVATION OF THE APPROACH FILL. LOWER FILLS ARE OVERTOPPED BY SMALLER FLOODS, WITH DAMAGE TO THE FILL AND INTERUPTION OF TRAFFIC DURING AND AFTER A FLOOD. ON THE OTHER HAND, OVERTOPPING LOWERS THE UPSTREAM WATER LEVEL, THEREBY REDUCING UPSTREAM FLOOD DAMAGE. THIS PAPER PRESENTS A PROCEDURE FOR DETERMINING THE MOST ECONOMICAL COMBINATION OF BRIDGE AND EMBANKMENT LENGTHS AND APPROACH ROADWAY ELEVATION. THE ANALYSIS TAKES ACCOUNT OF THE FOLLOWING COSTS: CAPITAL RECOVERY ON THE INITIAL INVESTMENT, MAINTENANCE, EMBANKMENT FLOOD DAMAGE, TRAFFIC DELAY AND DETOURS, AND BACKWATER DAMAGE. TWO SEPARATE EXAMPLES ARE PRESENTED CONSIDERING STREAMS IN FLOOD PLAINS 900 AND 5,000 FT WIDE. /AUTHOR/

  • Supplemental Notes:
    • No 320, pp 40-65, 20 FIG, 12 TAB, 9 REF
  • Corporate Authors:

    Transportation Research Board

    500 Fifth Street, NW
    Washington, DC  United States  20001
  • Authors:
    • Morgali, James
    • Oglesby, C H
  • Discussers:
    • Willeke, Gene E
  • Publication Date: 1962-1

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Filing Info

  • Accession Number: 00201394
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Jul 29 1994 12:00AM