BRIDGES: BIRCHENOUGH TO BOSPORUS AND BEYOND FORTY YEARS' PROGRESS IN LONG-SPAN BRIDGE ENGINEERING

FOURTEEN BRIDGES DESIGNED BY THE AUTHOR'S FIRM, NOW CALLED FREEMAN, FOX & PARTNERS, ARE DESCRIBED TO ILLUSTRATE MAJOR ADVANCES IN BRIDGE BUILDING. THESE RANGE FROM THE BIRCHENOUGH BRIDGE, COMPLETED IN 1935, TO THE HUMBER BRIDGE, DUE FOR COMPLETION IN 1977. DUE TO THE GREAT DEPTH OF SAND IN THE RIVER BED AT THE SITE OF THE BIRCHENOUGH BRIDGE, A SINGLE-SPAN ARCH WAS CONSTRUCTED BETWEEN OUTCROPPING ROCKS ON THE BANKS. SIMILAR SITE PROBLEMS EXISTED AT THE OTTO BEIT BRIDGE OVER THE ZAMBESI, BUT HERE A SUSPENSION SPAN WAS ERECTED. OTHER SUSPENSION BRIDGES DESCRIBED INCLUDE THE FORTH ROAD BRIDGE, SEVERN BRIDGE, BOSPORUS BRIDGE AND THE HUMBER BRIDGE, THE MAIN SPAN OF WHICH WILL BE THE LARGEST IN THE WORLD WHEN COMPLETED. AT THE TIME OF ITS COMPLETION IN 1963, THE MEDWAY BRIDGE WAS THE LONGEST POST-TENSIONED CONCRETE CANTILEVER SPAN IN THE WORLD. THE DEVELOPMENT OF BOX-GIRDER CONSTRUCTION IS OUTLINED AND THE WYE, ERSKIN AND AVONMOUTH BRIDGES GIVEN AS EXAMPLES. THE LIGHT WEIGHT OF THIS TYPE OF STRUCTURE ENABLED 2 ADDITIONAL TRAFFIC LANES TO BE ADDED TO THE AUCKLAND HARBOUR BRIDGE, ONE EACH SIDE OF THE EXISTING BRIDGE, SUPPORTED ON BRACKETS ATTACHED TO THE ORIGINAL PIERS.