Modeling of longitudinal passing bars within the joint panel in poor anchorage condition

In old structures reinforced with smooth bars and poorly detailed (because of insufficient anchorage length, poor confinement within critical regions) slippages of longitudinal bars become significant and govern the global response invalidating the classical full bond condition. Due to poor bond-strength capacity within the joint panel, passing-through longitudinal bars may result in tension throughout the panel joint and anchor within the opposite convergent element. In this work the influence of anchorage loss of passing bars within joint panel is being investigated. Nonlinear analyses are being performed on an internal beam-column joint reproducing a connection of a concrete frame designed only for vertical loads and reinforced with smooth bars. The numerical investigations are compared with the experimental results of the joint that has been subjected to two consecutive tests: with and without FRP wraps applied at the columns zones near the panel joint. The sequence of the experimental tests has the aim of simulating a repairing procedure on a RC existing structure when a moderate seismic event occurs and a local strengthening at columns critical regions is designed.