Mechanical Behavior Of Prefabricated Concrete Beam-column Connections With Short Steel Box Girders

Focus on the limitations of existing prefabricated concrete beam-column connections,this paper proposes a prefabricated concrete beam-column connection with short steel box girder.In order to further understand the mechanical behavior of the new type beam-column connections and propose a reliable design method,the main contents include:Firstly,the reference to the relevant specifications about the design of the new type beam-column connections,the preliminary design method was presented.The new type beam-column connections were designed with engineering examples.Secondly,numerical simulation of the new type beam-column connections was done by ABAQUS,and the key technology,such as the materials properties,the type of unit for modeling,was verified to be applicable.Then,parametric analysis about 22 the new type connections were carried,which based on the numerical simulation.The main parameters include the strength of post-pouring concrete,the strength of the precast beam end concrete,the height of steel column,the size of hole,the position of hole,the size and the number of studs,etc.Finally,design method and recommendations for the new type beam-column connections were proposed.Based on the above analytical research,the conclusions are as follows:(I)The finite element results show that the new type beam-column connections meet two stage design principles:under the design loads,the connections are in the elastic stage;under the ultimate loads,the connections are stronger than components,which means that the concrete beam was destroyed before the destruction of short steel box girder,so the new type beam-column connections are safe and reliable.(2)The effect of improving the concrete strength of the post-pouring zone of the new type of node is better than that of the prefabricated beam end concrete.When the concrete strength of the precast components is C30,the strength of concrete which be used in the post-pouring zone is C40.(3)Increasing the height of the steel column,mechanical performance of the new type beam-column connections almost has no change in degree of compression injury of concrete columns was improved,and the most suitable height of the steel column is 1.5 times the beam height.(4)Increasing the opening of short steel box girder,the stiffness and the ultimate bearing capacity of the new type beam-column connections decreases,when the hole length is longer than 20%of short girder length,the ultimate bearing capacity of the new connections is 10%lower than that of the non-opened connections,and it can not reach the calculated ultimate bearing capacity,so the length of hole should not longer than 20%of short girder length.When the position of hole which near the column and the inner side of hole which near the column of the distance within 50%short girder length,under ultimate load,the pulling web of short steel box girder reaches ultimate strength,so the distance between the hole and the innermost distance should be longer than 50%of the length of the short steel box girder.(5)In the short steel box girder without the studs,when the bearing capacity of the connection has not yet reached the design value,the concrete beam and the short steel are squeezed,and the concrete beam cracked,while other parts are still far from the yield strength,so the studs must be placed on the inner wall of the short steel box girder.Under the premise of meeting the design and construction requirements,the new type beam-column connections with small size and a large number of studs have better mechanical performance.(6)The design method and suggestion of the new type of beam-column connections proposed in this paper can provide design guidance for the engineering application of the assembled concrete frame structure.