Modal behaviour evaluation of a rubber bearing isolated structure under the effects of cold weather by operational modal analysis

Within the scope of this thesis, the modal behavior of a building with a rubber isolator under the influence of cold weather conditions was studied by the operational modal analysis method. Rubber is a material rigidity of which increases in cold weather conditions.The basic approach of seismic isolation is to increase the building period with the isolators used at the foundation level of the building and to decrease the acceleration values that the structure may be exposed to during the seismic activity. The decrease in the period of the building with the decrease in working environment temperature of the rubber isolator is an expected structural behaviour. In this regard, the study of the global behavior of seismic isolated buildings with rubber isolators in areas under severe winter conditions is important for seismic isolated building technology. In this context, the structure of Erzurum Regional Training and Research Hospital, built on 386 rubber isolators in Erzurum province, where cold weather conditions prevail for a long time, was studied. After the theoretical modal analysis was done on the structural model, operational modal analysis studies were carried out on the building. By application of this method, it is possible to determine the dynamic behavior parameters of the building on site. Within the scope of the operational modal analysis study, the sensor layout first worked, and then the building dynamic behavior parameters at different atmospheric temperatures were determined. In addition, ambient and rubber isolator temperature measurements were taken on the isolator floor. Findings showed that; in case of 10 oC drop in atmospheric temperature, there may be a 13% decrease in the first period of the structure with an increase of approximately 32.8% in the isolator stiffness.