A simplified static analysis of the torsional effects induced by eccentric walls in one-storey frame structures

During the 2012 Emilia earthquake, several precast RC industrial build-ings were damaged or collapsed due to a strong rotational response triggered by the presence of a single or few eccentric walls within the regular mesh of columns. The objective of this work is to analyse the torsional effects induced by an eccentric wall in one-storey frame structures, and to provide formulas for a quick estimation of the displacement of the flexible side. Starting from the typical structural scheme of in-dustrial one-storey structures consisting of a regular grid of uniformly spaced col-umns, a stiff lateral shear wall has been added to make the structure asymmetric. A response parameter (displacement amplification factor), defined as the ratio be-tween the translational displacement of the irregular structure over the translational displacement of the corresponding equivalent regular structure without the added wall/s, is introduced to evaluate the torsional response of the system. An analytical formula is derived by means of a linear static analysis. The results indicate that the presence of a shear wall, even though significantly stiffer than the columns with respect to lateral action, does not always lead to a reduction of the seismic displace-ment demand in the columns.