Reliability Assessment of Bolting Systems for Steel Frames Connected to Reinforced Concrete Structures

An important issue in structural engineering is improving performance and safety by retrofitting/strengthening or repairing of existing reinforced concrete structures. Attaching a steel bracing system is one of the common solutions for retrofitting or repairing of damaged structures. An efficient load transfer between existing structural members and an attached retrofit system is significant to such repairs. For steel bracing systems, the load transfer between the steel system and existing concrete structures are achieved through proper anchorage between them. A typical steel-to-concrete connection includes a steel attachment - consisting of a baseplate welded to the attached member - and the anchors that actually connect the steel to concrete as bolting system. In the present paper, the reliability method is used to assess the safety of the steel bolting system that is used to connect steel frame systems to existing reinforced concrete columns. Herein, the steel frame systems are used to retrofit/strengthen existing reinforced concrete corbel beams as a structural support system. The effect of applied loadings, bolts geometry, bolts spacing variation and concrete quality on the concrete breakout strength are examined for the current problem. Reliability is assessed by estimating the failure probability of the single bolt failure and system bolt failure. The results are used to determine the parameters affecting safety of the connection system and to improve the performance and the technique of strengthening/repairing of the steel supporting frame systems.