Dynamic Response Characteristics for Repair and Strengthening Measures of theGepford Overhead Section

摘要

Experimental modal analysis prevalent within the automotive and aerospaceindustries has been rarely used for damage detection or structural rehabilitation of reinforced concrete structures. Experimental modal analysis, when used to evaluate the dynamic response characteristics, can predict the change in structural stiffness with ease and a level of confidence. A three phase repair and strengthening program of a full-scale prototype bridge was performed. Steps included: (1) repair of all flexural cracks by epoxy injection; (2) strengthening of the bridge section with external post-tensioning tendons, and; (3) investigation of a new strengthening technique for RC T-girder bridges consisting of the addition of a precase prestressed bottom soffit slab. It is the subject of the report to describe and evaluate the changes in dynamic response characteristics of the Gepford Overhead Section due to the strengthening measures outlined above as obtained from forced vibration tests and subsequent modal analyses performed at stategic states prior and subsequent to the structural modifications. Test results clearly indicate a significant change in the stuctural stiffness due to epoxy grouting of the flexural cracks in the bridge girders. These findings were substantiated by service load tests and yield limit state tests performed prior and subsequent to the epoxy grouting of all flexural cracks. An increase in the transverse stiffness of the bridge section was observed with the addition of the bottom soffit panel. Reduced forced vibration test data for all repair stages is presented.