Report - PEER - University of California, Berkeley

5.1 3D Tests on a Torsionally Unbalanced StructureA substantial improvement of the testing capabilities has been obtained by thecommissioning of a bi-directional PSD implementation.In the framework of the research activity of ELSA, PSD testing of a real-sizeplan-wise irregular 3-storey frame structure is being carried out as the core of theresearch project SPEAR (Seismic PErformance Assessment and Rehabilitation ofexisting buildings). The project is specifically aimed at throwing light onto thebehaviour of existing old RC frame buildings lacking seismic provisions. A balancedcombination of numerical and experimental activities was considered, including aseries of full-scale PSD tests on a torsionally unbalanced 3-storey RC frame structure,representing a common configuration of housing units in most earthquake-prone areasof Europe. The experimental phase focused on a real-size specimen (see Fig. 4). Thefirst tests were carried out on the structure in its original, “as built” configuration.Following these tests, a light (i.e., member-level) retrofitting intervention (FRPwrapping of columns to improve ductility) was carried out. A new round of tests willbe performed on the retrofitted configuration, so that the effectiveness of currentlyavailable guidelines for the design of retrofitting interventions will be judged. Finally,the damage inflicted by the second round of tests will be repaired and the structuremore heavily retrofitted, by means of interventions aimed at improving the globalstructural configuration.Figure 4. 3D tests on an full-scale model of a torsionally unbalanced RCstructure: view of the model at the testing site (left); actuators layout andlocation of floor centre of mass (CM) (right).The bi-directionality of the PSD test, consisting in the simultaneous applicationof the longitudinal and the transverse component of the earthquake to the structure(see Fig. 4), introduces a higher degree of complexity, from both the analytical andtechnical points of view, with respect to usual unidirectional PSD testing. In fact,three DOFs per storey need to be taken into account: two translations and one rotationalong the vertical axis, as opposed to the single degree of freedom per storey that isusually taken into account in unidirectional PSD testing. Four actuators per storeywere connected to the structure, three of which were strictly necessary. A redundant289