Retrofit of non-code conforming moment resisting beam-to-column joints: A case study

The non-linear monotonic and hysteretic behaviour of as-built and retrofitted beam-to-column joints of an existing non-code conforming steel multi-storey building was investigated by means of finite element simulations. The building case study was originally designed to resist only gravity and wind loads without any capacity design principle. The as-built joints have continuous beam and interrupted columns that are bolted with end-plate splice to the tapered flange of the beams in the nodal zone. These joints were analysed to assess their non-linear response. The finite element analyses showed adequate resistance against gravity loads, but poor performance under seismic and column loss scenarios. Two retrofit strategies were designed in order to enhance the local and global performance in order to guarantee the weak beam-strong column condition, namely: (i) strengthening the column and its connection; (ii) weakening of the beam. Different types of interventions were designed per examined strategy and numerically analysed to assess the global and local response of both external and internal joints. A TOPSIS multicriteria analysis was also performed to identify the most suitable type of intervention.