Pseudo-Static Test of Mixed Connections Between Steel Columns and Concrete Columns in Pudong (Shanghai) International Airport Terminal 2

摘要

Mixed columns, consisting of a steel upper portion and a concrete lower portion, were used in the construction of Pudong International Airport Terminal 2. Two types of joints were designed for connections between the steel roof and concrete columns. The first is a cast steel bearing, connecting inclined steel branches and the supporting concrete member; the second is a direct embedment of the inclined steel branch into the concrete column.In order to evaluate the mechanical behavior and reliability of these mixed connections, pseudo-static tests were carried out at Tongji University. Results and conclusions from this investigation include: 1) cracking and spalling were observed at the top of the concrete columns due to the moment applied by the upper steel columns and abrupt variation of column stiffness near the joint. Additional stirrups or an exterior steel tube are suggested to enhance shear capacity and improve confinement of the outer concrete. 2) Damage occurring at the bottom of the steel column could be attributed to the modulus of elasticity and yield strength of the steel both being decreased about 10% in the Heat Affected Zone (HAZ) as well as higher than expected strength of the cast steel. The damage observed near the butt weld showed great similarity to that of steel structures in the Kobe earthquake 1995. 3) A potentially critically damaged section was identified in the cast steel bearing based on the numerical and experimental results, however it remained undamaged in the test. Since the strength of the cast material is more inconsistent than hot rolled steel; a larger variance will be used to for the design strength. Therefore, the actual capacity of the cast steel bearing is more likely to be under-estimated and the performance of the cast steel may not be as expected in the original design. 4) Additionally, based on the analyses of loading transfer mechanism and calculation of elastic rotational stiffness with respect to cast steel bearings, mechanical behavior and deformation capacity of the bearings were investigated. A component of displacement at the top of steel columns was examined as well.