ABSTRACT
Since the 1995 Hyogoken-Nanbu earthquake (Kobe earthquake) the effectiveness of bridge rubber bearing has attracted the interests of many engineers in Japan. It is because the laminated rubber bearings can not only provide satisfying vertical stiffness, but also sufficient horizontal flexibility. In recent years, the ageing problems have been realized too. It is clarified that ageing causes rubber performance to drop, causing for instance an increase of hardness, and a decrease in tensile strength as well as elongation at break. Thermal oxidation is found to be the most significant factor deteriorating the rubber materials. The heterogeneity of material properties in rubber bearing during ageing process is also studied. It is estimated that from the coldest area to the hottest area in Japan the equivalent stiffness of rubber bearings will increase by 5-25% after 100 years.
