Exact evaluation of the location of the optimum torsion axis

The paper addresses the issue of the evaluation of a reference axis which in multistorey buildings can play the same role as the elastic centre in one-storey schemes. In this regard the authors propose an improvement to the procedure previously suggested by Makarios and Anastassiadis for the evaluation of the position of the optimum torsion axis. The above-mentioned researchers based their evaluation on a parametric analysis of asymmetric frame-wall systems and thus defined the location of the optimum torsion axis only approximately. The authors, instead, face the problem from an analytical point of view and propose mathematical expressions that rigorously define the position of the same axis. Some examples are finally reported aiming at comparing the two approaches and highlighting the improvements brought by the rigorous approach to the approximate determination of the location of the optimum torsion axis.