China MODELLING OF THE HORIZONTAL SLAB OF A 3 D IRREGULAR BUILDING FOR NONLINEAR STATIC ASSESSMENT

The manner in which the horizontal slab in 3D buildings, or better the rigid diaphragm effect, is modeled may influence the response of the structure when subjected to seismic action. In this work different ways of modelling the rigid diaphragm effect are tested and compared, through the application to the irregular 3D SPEAR building, a full-scale specimen tested under pseudo-dynamic conditions at JRC Ispra, representing typical old three-storey buildings built in the Mediterranean region in the early 1970s. The dynamic properties of the different models (periods, modes of vibration and effective modal mass percentages) are analysed, and the corresponding interaction with seismic action is studied by means of nonlinear static and dynamic analyses; different response measures, such as capacity curves, interstorey drifts and displacements are evaluated for the two orthogonal directions. The results of this study show that the most accurate and reliable way of modelling the floor’s behaviour is the Rigid Diaphragm with Lagrange Multipliers nodal constraints model.