The Mechanical Properties Analysis Of The Semi-rigid Column Base Joint Under The Cyclic Loading

With the improvement of construction industrialization degree, the prefabricated building has developed rapidly. Joint connection occupies a very important position in the prefabricated assembly steel structures. High strength bolts are widely applied in the prefabricated assembly structures with the advantages of good mechanical performance and simple construction. In the steel frame structures, column base is an important joint that connects the upper structure and foundation. The reliability of its connection directly influences mechanical characteristics of the whole frame structure. A kind of semi-rigid column base joint is proposed in this paper which uses high strength bolts to connect the column and foundation. Studying its mechanical properties has strong practical value.The base plate of this kind of column base is set with 25 mm slip hole. Under the action of the column axial load and the high strength bolt preload, Column base begins to slip when the column base shear can overcome the friction resistance. Taking this kind of column base joint as the research object, the shear and bending force analysis are carried out on the joint section. The simplified shear-slip curve and moment-rotation curve are theoretically obtained.Finite element modeling of this kind of column base is established by using ANSYS software. The simplified shear-slip curve and moment-rotation curve are obtained by applying monotonic horizontal displacement load on the model. This column base takes on the double semi-rigid characteristics of shear and rotation which is consistent with the theoretical constitutive relation curves. The influence of friction coefficient on the monotonic mechanical performance of the model is researched. The greater the friction coefficient is, the greater the shear stiffness and shear capacity of the model are; however, the friction coefficient has little influence on the moment-rotation characteristic.By applying horizontal reciprocating cyclic displacement load on the model, the shear-slip hysteretic curve and moment-rotation hysteresis curve are gained. Along with the increase of cyclic load, hysteresis curve becomes more and more full. Due to the appearance of friction energy dissipation, the energy dissipation coefficient of shear-slip hysteretic curves is significantly increased after the slip of column base. The effect of friction coefficient on the shear hysteresis performance is studied. The result shows that when the friction coefficient increases, the shear energy dissipation, shear stiffness and shear bearing capacity of column base joint also grow.With the application of semi-rigid column base on the steel frame, force-displacement hysteretic performance of the steel frame structure is researched which is compared with the steel frame of rigid column base. Under the reciprocating cyclic load, column base of the Semi-rigid frame slides first and then the material gets into the plastic state. Semi-rigid column base can improve the energy dissipation performance of the frame structure in a certain extent which is beneficial to structural seismic resistance.