Bridge Demolition applying Principles of Segmental Concrete Box Construction in Reverse

摘要

Innovative techniques were used to demolish the existing ramp TE structure; thefirst technique mimicked balanced cantilever construction typically used in segmental bridgeconstruction but in reverse sequence. Rather than using a gantry system to support thesegments as they were erected; a strongback system centered over the single columns wasused to support the spans while they were demolished in a sequence which maintained abalanced condition.The second technique used span-to-span type support similar to that used in segmental bridgeconstruction except instead of support from the bottom with a truss, strongbacks werelaunched across the span and the structure was hung from the top to provide stability duringdemolition.Ramp TE structure is a Hollow Box Girder Viaduct made of reinforced concrete, innovative atthe time of construction (1960's), suspended by single columns supporting a horizontallycurved roadway providing a vital link for a complex traffic interchange that feeds into theGeorge Washington Bridge and spans over Interstate 95.The AHB project required removal and replacement of the entire ramp TE structure, withexception of the lower portions of several of the single columns, while maintaining traffic on avery busy interchange. Therefore, in addition to the aforementioned innovative techniques, itwas necessary to erect a horizontal and vertical shield over the interstate before demolition ofthat portion of the structure using conventional demolition techniques. However, the originaldesign used a temporary truss system which was replaced by a girder support systemdesigned by the contractor.The entire demolition scheme was completely redesigned by the contractor at a significantsavings in both time and cost.