PACESETTING CALIFORNIA SPANS GORGE WITH GERMAN BRIDGE SYSTEM

THE ARTICLE BRIEFLY DESCRIBES THE PINE VALLEY CREEK BRIDGE, 80 KM FROM SAN DIEGO IN CALIFORNIA. THE BRIDGE WORK WAS STARTED IN MARCH 1972 AND SHOULD BE COMPLETED BY NOVEMBER 1974. THE CHOICE OF CANTILEVER SEGMENTS OF PRESTRESSED CONCRETE CAST-IN-SITU, IS ESTIMATED TO COST 10 PER CENT LESS THAN THE CONVENTIONAL TYPE OF BRIDGES. THE ORIGINAL DESIGN W1S DEVELOPED IN GERMANY. THERE ARE 4 PIERS OF EACH MADE UP OF TWO RECTANGULAR CELLULAR COLUMNS STRUTTED TOGETHER AND FLARED AT THE TOP TO FORM A 'Y' SHAPE. EACH ARM OF THE 'Y' SUPPORTS A BOX GIRDER THE WIDTH OF A DUAL LANE CARRIAGEWAY WITH SHOULDERS. FOOTINGS ARE ANCHORED BY 32 MM PRESTRESSED BARS TO SOLID ROCK 6 METRES BELOW GROUND. A CONCRETE MIX WITH 510 KG OF FINELY GROUND CEMENT PER CUBIC METER IS USED TO REDUCE THE STRIPPING TIME OF FORMS. IT IS REQUIRED TO DEVELOP STRENGTHS OF 18 N/MM2 IN 24 HOURS AND 35 N/MM2 IN 28 DAYS.