Use of innovative anchors for composite action in rehabilitated steel structures

Of the nearly 5000 bridges in New South Wales about 17% are more than 50 years old. Most of these old bridges are considered structurally deficient by modern standards for the loads they are required to carry. These bridges will have to be replaced or strengthened by utilizing post installed shear connection systems. The advantage of a shear connection system that can be post installed is that they can also be uninstalled. This property could be leveraged to manufacture demountable structures.Two blind bolt connectors were used as shear connection systems in steel-concrete composite beams. Alongside these welded shear stud and non-composite sections were tested for comparison. Different damage states were created using a four point load system with 20%, 40%, 60%, and 80% of the calculated ultimate loads. For each loading stage a dynamic analysis was carried out on the specimen. The same tests were also conducted at initial and post failure stages. Four series of beams were planned for study these were cast simultaneously in two sets of two. The first two sets were named Short term and Long term. The purpose of these series was to determine the effects of long term loading, temperature, and humidity over the course of one year. Also, to investigate any difference in behaviour due to concrete ageing. The second two series were named Cast-in and Retrofitted. The Retrofitted series were cast as non-composite sections. They then underwent a retrofitting procedure to fit the two blind bolt types and the welded shear stud. Both these series were subjected to destruction testing to examine the suitability of the blind bolt systems for retrofitting to existing structures.It was found that the two blind bolt types make good substitutes for welded shear connectors with some provisions. Each bolt type was affected differently by environmental factors. The retrofitting procedure was found to have profound effects on the natural frequencies of undamaged specimens. Also damage accrued due to loading was fundamentally different between Cast-in and Retrofitted specimens. Well known techniques for dynamic analysis were shown to be suitable to shear connectors used