A study on performance of natural rubber bearings with time under freeze–thaw cycles

Considering that the rubber isolation bearing of buildings is exposed to the air will be, respectively, subjected to the freeze–thaw cycles in the wintertime period, the isolation effect of the bearing is very likely to be affected. To this end, the freeze–thaw cycle tests of natural rubber (NR) materials were carried out, with the aim of investigating how the performances of NR bearings in northern China change under freeze–thaw cycles in winter and the mechanical properties of NR materials with time were studied. The results show that after the freeze–thaw cycle test, the appearance of the rubber sheet did not have an obvious change. However, the sealing plate and steel plate layer of the rubber bearing had brown rust spots and the colour of the rubber layer was still dark. After the freeze–thaw cycle, the vertical compression stiffness and the horizontal equivalent stiffness of the rubber isolation bearing showed a decreasing trend. After freeze–thawing cycles, the Mooney–Rivlin constitutive model constant C₁₀ of rubber material showed a decreasing trend with the test time while C₀₁ showed an increasing trend. Under the action of freeze–thawing cycles, the stiffness of basic mechanical properties of rubber isolation bearings will decrease as time increases. Among them, the vertical compression stiffness has decreased by 10.24% and the horizontal equivalent stiffness has decreased by 2% after 50 years under the freeze–thaw cycles based on the prediction equation of the test values, while the vertical compression stiffness has decreased by 5.73%, and the horizontal equivalent stiffness has decreased by 8.7% after 50 years under the freeze–thaw cycles based on the prediction equation of the simulation value. The above research results can provide a basis for the study of the degradation law of the rubber isolation bearing and the evaluation of the life cycle performance of the isolation projects.