Experimental study on the mechanical properties of nuclear reactor structures with different contact interfaces under high temperatures

The thermo-mechanical behavior of the interface zone in nuclear reactor buildings is crucial for structural safety at high temperatures. In this study, two 1:10 scale prototypes were designed and fabricated to investigate the mechanical behavior of a steel plate–concrete interface (Model-1) and a concrete–concrete interface (Model-2). The tests were conducted at temperatures of 50 °C, 100 °C, and 150 °C to evaluate the temperature distribution pattern and the interfacial friction mechanism of the bottom plate of the nuclear reactor building. The results show that the overall temperature propagation behavior of the two models was basically the same at different temperature levels, with the maximum temperature difference of 0.2∼0.6 °C. Comparison with Model-2, Model-1 showed a sudden temperature increase between the bottom plates of Building 1 and Building 2 at 150 °C, with the maximum temperature difference of 4.1 °C. This was attributed to the high thermal conductivity of the steel plate, which led to heat accumulation and non-uniform temperature distribution. The frictional response of Model-1 was higher than that of Model-2. At 150 °C, the tangential friction force and normal compressive force at the side contact interface were 1.67 and 1.71 times those in Model-2, respectively, while at the bottom contact interface they were 1.2 and 1.54 times those in Model-2, respectively. The proportion of lateral normal extrusion force decreased with increasing temperature and ultimately remained at 78%. Both models showed no signs of failure, and the steel bars did not yield. On this basis, a temperature-dependent friction coefficient model was proposed and validated, with an average ratio of predicted values to experimental values close to 1 and R 2 exceeding 0.95; the model can be used to evaluate the friction behavior of contact interfaces under elevated temperatures.