Factors Influencing Bond Properties in Concrete Encased Steel Columns at High Temperatures

This paper presents experimental results on factors governing the bond strength between steel and concrete in concrete encased steel (CES) columns at high temperatures. Push-out tests were conducted on 22 CES specimens to investigate the bond strength between concrete and steel under the temperature of 250 °C, while one specimen was tested at room temperatures for comparison. Data obtained from these tests revealed that the bond properties of CES structures between steel and concrete is influenced by a number of factors, including concrete strength, concrete cover thickness, stirrup reinforcement ratio, steel ratio and anchorage length of steel at high temperatures. The formulas for predicting the ultimate bond strength and slip between steel and concrete of CES structures are proposed based on the experimental investigations.