| Modular steel structure buildings play an increasingly important role in modern architecture because of their highly integrated characteristics,which have obvious advantages in construction efficiency and environmental protection.As the key parts of modular steel structure buildings,modular steel structure joints still have some limitations such as no construction space,no disassembly and replacement,and only applicable to specific beam-column sections,which makes the application range of modular steel structure buildings limited.To solve the above problems,a new type of Self-lock Plug-in joints in modular steel structure is proposed in this thesis.The tensile and flexural properties of the joint are studied by means of experiment,numerical parameters and theoretical analysis.The main contents and research results are as follows:(1)A new type of Self-lock Plug-in modular steel structure joint is proposed,which has a middle column joint that can be applied to eight modules,and can be quickly disassembled after installation and adapted to a variety of beam-column joint forms.The chamfering of the contact position between the fixed ring plate and the buckle inside the joint ensures that the friction self-locking failure will not occur after the vertical connection of the joint,and also allows the error in the manufacturing and installation process of the joint.By inserting and unlocking the self-lock joint,the feasibility of the new internal plug-in self-lock joint is verified.(2)Full scale tensile tests were carried out on four groups of new Self-lock Plugin joints in modular steel structure The failure modes of weak joints M2,M3 and M4 were shear failure of the clip,tensile failure of the side wall of the clip and shear failure of the upper wall of the clip,respectively,while the equal strong joint M1 did not fail but showed shear deformation at the clip.Note Internal components of equal strength joints have good collaborative tensile performance.The initial stiffness and ultimate load of weak and strong joint M4 are 466.02 k N and 279.638 k N,and equally strong joint M1 increases by 20.46% and 78.59% respectively compared with M4.Based on the tensile test results of the joints,16 refined finite element models were established by using ABAQUS finite element software to further analyze the tensile properties of the joints.The results show that: When the design value of tensile strength of super strong joints is increased by 40% compared with that of equal strong joints,the increase of initial stiffness is less than 2%,and the increase of ultimate bearing capacity is less than 6%,indicating that the equal strong design joints have good tensile performance.The sensitivity analysis of the finite element parameters of joint tensile strength shows that the thickness of the buckle has the greatest influence on the tensile strength of the joint,followed by the thickness of the side wall of the groove,and the thickness of the upper wall of the groove has the least influence.(3)The bending test of two full-size self-lock joints was carried out.The results showed that the failure mode of T1 specimens without stiffeners was the weld cracking failure of the floor beam and the lower module column,which belonged to the brittle failure.However,the failure mode of T2 specimen with stiffeners arranged between beams and columns starts from the local buckling of the compression flange of the ceiling beam,and the final failure mode is the crack failure of the weld between the ceiling beam and the lower module column,which is a ductile failure,indicating that the existence of stiffeners causes the plastic hinge on the beam to move out,increasing the ductility and cooperative bending ability of the beam-column joints.The initial stiffness of T1 was 11288 k N·m/rad,and the ultimate load was 175.56 k N·m.Compared with T1,the initial stiffness and ultimate bearing capacity of T2 increased by 27.10%and 27.16%.(4)Based on the bending test of self-lock joints,33 fine finite element models were established by using ABAQUS finite element software to verify the accuracy of the models.Further,the parameter analysis of the flexural performance of the new Selflock Plug-in joints in modular steel structure is carried out,and it is found that increasing the rigidity ratio of the composite beam can significantly improve the initial stiffness and ultimate bearing capacity of the joints.The effect of increasing the length of stiffeners is better than that of increasing the thickness of stiffeners.For stiffeners of the same volume,the initial stiffness and yield moment of joints increased by 6.67%and 19.78%,respectively.The stress concentration of modular column is reduced by increasing the thickness ratio of inner plug to column and the length of inner plug.When the clearance between the inner plug-in and the column is less than 2mm,the reduction of the initial stiffness and ultimate bearing capacity is not more than 5%,indicating that the new self-locking machining and installation allows a certain construction clearance.(5)The structural design suggestions for the bending resistance of the new Selflock Plug-in joints in modular steel structure are given: the stiffness ratio of the composite beam should be between 1.0 and 2.5,the thickness ratio between the internal inserts and the column wall should be between 1.0 and 1.25,and the gap between the internal inserts and the column wall should not be greater than 2mm.Finally,the formula solution of the moment-rotation curve of new Self-lock Plug-in joints in modular steel structure is obtained.The results show that the error is within the acceptable range and the reliability is high,which provides a reference for practical engineering design.There are 97 figures,27 tables and 83 references in this thesis. |
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