Research On New Connection Designs And Structures Of Prefabricated Cold-formed Steel-concrete Composite Structures

The cold-formed steel structures have the characteristics of light weight,high strength,fast construction,energy saving and environmental protection,which are in line with the development trend of green building advocated by our country.In view of China’s basic national conditions that’more people and less land’and mid-to-high-rise concrete buildings are common structural forms in China,the application of cold-formed steel structures in China is limited.In this thesis,according to the characteristics of cold-formed steel and concrete structures,four new connectors,prefabricated cold-formed steel composite wall and composite floor construction units and related connection structures were proposed.On this basis,prefabricated cold-formed steel-concrete composite structures were formed.At the same time,the mechanical properties,calculation theories and design methods of the new connectors were systematically studied.The main contents and conclusions are as follows:1、The following conclusions were obtained by solving the connection problem of cold-formed steel-various sheathing boards composite wall and cold-formed steel-ALC boards composite floor with concrete beam,and improving the current construction technology of cold-formed steel composite wall and floor:（1）Aiming at the connection problem between cold-formed steel-various sheathing boards composite wall and concrete structure,adjustable cast-in anchor channel,E-shaped connector and related structures were proposed.The adjustable cast-in anchor channel has high redundancy and reliable mechanical performance,and the E-shaped connector is easy to construct and more suitable for complex construction scenarios;（2）For the connection problem between cold-formed steel-ALC boards composite floor and concrete structure,bu-shaped and channel steel connectors were proposed.The clearance of cold-formed steel floor connected by bu-shaped connector is large,and the bearing capacity of cold-formed steel floor connected by channel steel connector is high;（3）Aiming at the problem of prefabricated construction,two kinds of distributed encapsulated cold-formed steel composite wall construction units and prefabricated cold-formed steel-ALC boards composite floor construction units with bu-shaped and channel steel connectors were proposed to facilitate the factory prefabrication and on-site prefabricated construction of structural components and improve construction efficiency.2、The calculation theories and numerical simulations of wall connectors were studied,and the following conclusions were obtained:（1）The calculation theories of adjustable cast-in anchor channel were systematically summarized and extended,and the calculation methods of E-shaped connector and its self-tapping screw were given;（2）The adjustable cast-in anchor channel has good mechanical performance.When the single anchor or double anchor is sheared,the distance between the anchor head and the edge of the concrete beam should be controlled to be greater than 50 mm,and the distance between the T-tooth bolt and the edge of the concrete beam should be greater than 75 mm.When the single anchor or double anchor is pulled,the distance between the anchor head and the edge of the concrete beam should be controlled to be greater than 50 mm,and the T-tooth bolt should be controlled between the two anchor head when the double anchor is pulled.When longitudinally arranged,the spacing of multiple T-tooth bolts should be greater than 45 mm,and the shear capacity should be superimposed by the number of T-tooth bolts.When controlling the tensile force,the anchor head spacing can be shortened to 100 mm to adapt to more complex construction scenarios.When controlling the shear force,double anchor can be replaced by single anchor to adapt to more complex construction scenarios;（3）When using the E-shaped connector to connect,the failure mode is the U-shaped cold-formed steel guide rail tearing at the self-tapping screw connection,and the structural connection have good repair,ductility and energy dissipation capacity.3、The design method and experimental study of floor connectors were carried out,and the following conclusions were obtained:（1）Under the given design basis,the floor connector and its related connection structure were designed,and the force mechanism of the bolt connection and the cold-formed steel joist with concrete boundary were obtained,and the force reliability of the floor connector and its related connection structure were preliminarily verified from the structural level;（2）Through the simplified mechanical model,the design formulas of floor connectors and their connected cold-formed steel composite floor were derived,which can be used for the design of cold-formed steel joist with different spans,section forms and steel strengths;（3）The reliability of the floor connector and its related structure were verified by the tests.When the load reached the standard value of the floor live load of the storage room in the normal use state of 5k N/m²,the force of the cold-formed steel joist connected by the two floor connectors were in the elastic section,which was far less than the ultimate load of the elastic section,and the deflection was far less than l₀/200.The bu-shaped connector and the channel steel connector have good ductility,and the connection mode of high strength bolts is safe and reliable.The innovations of this thesis are as follows:（1）The adjustable cast-in anchor channel,E-shaped connector,bu-shaped and channel steel connector were proposed to solve the connection problem between cold-formed steel and concrete structure.The distributed encapsulated cold-formed steel wall construction and prefabricated cold-formed steel floor construction units were proposed to improve the current construction technology of cold-formed steel composite wall and floor.（2）A series of construction measures of adjustable cast-in anchor channel in different construction scenarios were quantified.The force mechanism of cold-formed steel members and structures connected by floor connectors under complex boundaries and constraints were revealed,and the design method of floor connectors and their connected cold-formed steel composite floor were proposed.