The Importance of Plan-Wise Irregularity

Abstract

In the framework of the experimental activity of the ELSA Laboratory of the JRC, an extensive PsD testing campaign was carried out on a doubly bi-eccentric plan-wise irregular R.C frame structure representative of non-seismically designed buildings widespread in Europe. In spite of the torsional irregularity being minor, the torsional response turned out to be quite significant, as a result of the choice of the seismic input. The opportunity was thus taken of experimentally assessing the effects of irregularity on the seismic behaviour and to compare it to the effects of poor structural detailing and lack of basic seismic design requirements. Also, the effectiveness was assessed of two different retrofitting strategies, a ductility-only intervention and a strength-only one, in providing a satisfying seismic response and tackling the structural weaknesses detected by the tests in the unretrofitted configuration. Conclusions are thus drawn on the basic criteria to be taken into account when devising a retrofitting strategy for existing irregular buildings under strict time and budget constraints. Also, it is discussed if whether a reduction of torsional effects is a basic aim to be pursued in retrofitting under above said constraints or if it can be neglected in the decision making process, even though the role of torsional effects in affecting the response is indisputably acknowledged.