THE BUMP AT THE END OF THE BRIDGE

Abstract

THE GENERAL RELATIONSHIP IS SUMMARIZED BETWEEN THE APPEARANCE OF BRIDGE APPROACH SETTLEMENT AND VARIOUS CONDITIONS AT BRIDGE SITES. DATA OBTAINED FROM A SURVEY OF EXISTING BRIDGE APPROACHES CONDUCTED IN THE SUMMERS OF 1964 AND 1968 PROVIDED GENERAL INFORMATION AS TO THE PREVALENCE OF EMBANKMENT OR FOUNDATION PROBLEMS IN KENTUCKY. THE APPROACHES WERE CLASSIFIED ACCORDING TO ONE OF THE FOLLOWING SETTLEMENT CATEGORIES: (1) GROUP 1 SETTLEMENT, NO MAINTENANCE NECESSARY AND NO APPROACH FAULT NOTICABLE, (2) GROUP 2 SETTLEMENT, NO MAINTENANCE PERFORMED, HOWEVER, AN APPROACH FAULT WAS OBSERVED, AND (3) GROUP 3 SETTLEMENT, MAINTENANCE PERFORMED ON THE APPROACH. THE CRITERION USED TO DISTINQUISH BETWEEN GROUPS 1 AND 2 WAS WHETHER OR NOT A BUMP WAS EVIDENT WHEN AN AUTOMOBILE PASSED ONTO OR OFF THE BRIDGE DECK. ADDITIONAL INFORMATION WAS OBTAINED BY VISUALLY INSPECTING EACH APPROACH. THE AGES OF THE APPROACHES WERE NOTED. FROM THESE DATA, IT IS EVIDENT THAT PRESENT DESIGN AND CONSTRUCTION PROCEDURES ARE NOT SUFFICIENT TO GUARANTEE SMOOTH BRIDGE APPROACHES. A COMPARISON OF PORTLAND CEMENT CONCRETE AND BITUMINOUS CONCRETE APPROACHES SHOWS A MARKEDLY HIGHER PERCENTAGE OF BITUMINOUS CONCRETE APPROACHES WITH PATCHING THAN RIGID APPROACH PAVEMENTS WITH MUD JACKING IN 1964. HOWEVER IN 1968, THE DIFFERENCE IN PERCENTAGE OF MUD JACKED AND PATCHED APPROACHES, AS WELL AS SMOOTH APPROACHES, WAS ALMOST INSIGNIFICANT. APPARENTLY FOR A SHORT PERIOD OF TIME THE RIGIDITY OF PORTLAND CEMENT CONCRETE PAVEMENT REDUCED THE OCCURRENCE OF THE APPROACH FAULT BY BRIDGING THE PRESUMED DEPRESSMENT BEHIND THE ABUTMENT. A COMPARISON OF THE MOST COMMONLY USED TYPE OF ABUTMENTS WITH RESPECT TO THE 3 SETTLEMENT GROUPS REVEALED THAT THE OPEN-COLUMN (OPEN-END) TYPE WAS MORE COMMONLY ASSOCIATED WITH SETTLEMENT GROUP 3 THAN EITHER THE PILE-END-BENT (OPEN-END) TYPE OR STUB (CLOSED-END) TYPE IN 1964. HOWEVER, IN 1968, THERE WAS AN INCREASE IN PERCENTAGE OF FAULTED APPROACHES FOR ALL TYPES OF ABUTMENTS WITH THE PERCENTAGE FOR PILE-END-BENT INCREASING THE MOST. THERE WERE SMALL DIFFERENCES IN PERCENTAGES BETWEEN THE PILE-END-BENT AND OPEN-COLUMN ABUTMENT. THE PERFORMANCE OF BRIDGE APPROACHES WITH AND WITH-OUT SPECIAL GRANULAR BACKFILL WAS COMPARED. NO ADVANTAGE WAS SHOWN AND THE INFLUENCE OF DIFFERENT GEOLOGICAL AND SOIL CONDITIONS WAS ONLY SLIGHTLY NOTICEABLE.