Experimental Study of Box-Shaped Steel Column Bolted Connection

Since the 2013 National Construction Conference, state and local governments have issued a serious of documents to promote the development of prefabricated buildings. It conforms to the national policies and is also the trend of construction industry to actively develop and adopt prefabricated structures, especially prefabricated steel structure and to realize standardized design, factory production, and assembly construction. Box-shaped columns are widely used in steel structure buildings because of their equal bending stiffness in the two main axis directions. At present, box-shaped columns basically use fully-penetrated welded connection technology, which has many problems such as low construction efficiency, high labor costs, environmental pollution, severe damage upon earthquakes, and poor durability of on-site welding.
Based on the above key problems to be solved, a box-shaped steel column bolted connection was proposed. In this connection, the upper and lower installation units of the box-shaped steel column are connected by flange plates with high-strength bolts. In order to enhance the performance and improve mechanical properties of the core area of the connection, a core tube is set at the key position of the upper and lower units. In order to ensure the good co-working performance of the core tube and column, it is required that the gap between the core tube and the column wall does not exceed 2 mm. When the machining accuracy is not satisfied, there are two measures to improve it. Compensation plate can be set between the core tube and the column wall, or blind bolts can be installed to reduce the gap between the core tube and the column wall to ensure the co-working performance. Two kinds of the bolted connections with blind bolts and compensation plates were designed and tested under low-cycle reciprocating loads to study the mechanical performance of the bolted connections, and to make contrast with that of the fully-penetrated welded connection to study the rigid connecting behavior of the bolted connection.
The test results indicate that the setting of the core tube can provide certain flexural and shear resistance. When the story drift is 0.005 rad (1/200), the core tube contacts the column wall and work together to make the box-shaped steel column bolted connection more excellent. As the story drift is no more than 0.04 rad(1/25), the hysteresis performance and stiffness degradation trend of the both box-shaped steel bolted column connections are close to each other. When the story drift reaches 0.05 rad(1/20), the hysteresis performance of the box-shaped steel column bolted connection with blind bolts is better than that of the box-shaped steel column bolted connection with compensation plates. In the whole loading process, both of the box-shaped steel column bolted connections have excellent ductility, and the connection with blind bolts performs better and can significantly reduce bolt tension. The box-shaped steel column bolted connection with compensation plates and the box-shaped steel column bolted connection with blind bolts are damaged at 0.05 rad and 0.06 rad, respectively and the latter one can withstand greater deformation. The box-shaped steel column bolted connections can be selected flexibly according to the actual needs as conducting engineering design. The box-shaped steel bolted column connections possess similarly static performance with that of the fully-penetrated welded connection and can be designed as rigid connection when applied in actual engineering. The box-shaped steel bolted column connection technology realizes fully-bolted rigid connection and efficient assembly of steel structure system, which has great strategic significance to promote the upgrading of construction industrialization, improve construction efficiency, reduce environmental pollution and promote ecological civilization.