VALUTAZIONE SPERIMENTALE DEL CARICO CRITICO DI ISOLATORI CILINDRICI IN ELASTOMERO ARMATO

In the Laboratory of DiSGG at the Basilicata University the buckling loads of a lot of cylindrical elastomeric bearings have been evaluated experimentally. The bearings have been tested imposing an initial shear deformation and keeping it constant while increasing axial load since the reaction to the initial shear deformation becomes zero. The corresponding value of axial load has been assumed as buckling load; in fact, shear stiffness decreases when the axial load increases and it becomes zero when buckling load has been reached. After a brief description of test equipment, a comparison among experimental buckling loads (PCR LIVELLO 3), buckling loads (PCR LIVELLO 2) obtained through Haringx theory using shear and axial stiffness of bearings experimentally measured, simplified expressions (CEN /9/ and Linee Guida italiane /10/) of buckling loads (PCR LIVELLO 1) obtained via the characteristics of the elastomer, are shown. Based on the experimental results, some suggestions for design and code provisions concerning the correct evaluation of buckling load and the influence of high compressive load on the shear stiffness of seismic elastomeric bearings are proposed.