Beam-column joint nomogram: A simple and fast-to-use tool to evaluate the joint integrity in RC structures

Beam-Column Joints (B-CJs) are crucial elements in Reinforced Concrete (RC) frame structures since their behaviour strongly affects the seismic performance of the structures. Indeed, design hierarchy principles of these kind of structures are conceived to obtain the BCJs preservation from premature failure, allowing the structural members to develop their full strength and ductility and assuring a global dissipative structural behaviour. As well known, B-CJs are the last link of the hierarchy chain and are designed in the last step; if code joint verifications are not satisfied, the B-CJ needs to be re-designed, with possible consequences on the redesign of the structural members framing into the joint and, often, on the architectural details. For these reasons, an early knowledge of the BCJs adequacy, since the early stages of the design process, can help engineers and architects to save time and to optimize the architectural and structural design of buildings. In this paper, a new graphical tool for supporting the design of B-CJs in RC frame structures is proposed. Diagrams (called nomograms) are presented, consisting in charts that lead to achieve the BCJ geometric dimensions and hoop amount so that the NTC18 B-CJ verifications are satisfied. The proposed nomograms can be used for all types of joints, and with any kind of geometry since they are dimensionless. Nomograms can simplify the RC building design since they offer an indication of the joint verification outcomes even from the early stages of the design process, i.e., at the moment in which the structure is conceived and built within a finite element model.