Valutazione numerica del carico critico di isolatori in elastomero armato

An iterative methodology to evaluate the buckling load of elastomeric laminated bearings, taking into account the non-linear mechanical properties of elastomers, has been set up. Based on the classical theory developed by Haringx, this methodology takes into account the variation of axial and shear stiffness due to the increase of axial load up to the buckling. At this purpose, the experimental results from compression and shear-compression tests on devices are utilised. By adopting that procedure, careful values of buckling load are calculated (evaluation of level 2). A simpler and less accurate evaluation of buckling load is also carried out, by adopting simplified expressions contained in current codes where only the shear modulus G of elastomer has to be determined from experimental tests (evaluation of level 1). By examining the results, the major role of the primary shape factor S1 and, particularly, of the secondary shape factor S2 on the buckling load values of laminated bearings is highlighted. Besides, simplified evaluation of level 1 shows satisfactory agreement with the more accurate procedure of level 2 for values of S1 up to 15 and adopting always S1 equal to 15, beyond that value.