Study On Bearing Capacitv Of Innovative Stiffened Tubular K-joints

Tubular joints are commonly used in long-span steel tube transmission towers.The reliability of joints is very important to the safety of transmission towers.In recent years,as transmission towers need to carry more multi-loop transmission lines and the height of the transmission tower is constantly increasing,the requirements of bearing capacity of transmission tower's joint are increasing and joint connections are necessary to be stiffened.However,at present,the research on stiffened methods of tubular joints is not enough,and the calculation method of bearing capacity of stiffened joints is not given in domestic and foreign standards.In this paper based on real engineering,a design method of the K-joint stiffened by gusset plate,saddle plates and ring stiffeners is proposed.To study the mechanical properties of the joints in this design form,the authors designed 11 specimens of scaled joints.The influence of stiffened joint parameters on the bearing capacity was studied through experiments,and finite element nonlinear analysis of the experimental joints were carried out.The effects of the thickness of the chord(T),the length of the gusset plate(B)and the center angle of the saddle plate(?a)on the ultimate bearing capacity of the joints are studied experimentally.At the same time,the strain,the load-displacement curves,the ultimate bearing capacity and the failure modes of the joints are obtained.The experimental results of 11 stiffened K-joints are in good agreement with the result of the finite element,which verifies the reliability of the finite element model.Parametric sensitivity study is then conducted via the validated finite element model.The result shows that the bearing capacity of the stiffened K-joints increases with the increase of the thickness of the chord,the length of the gusset plate and the center angle of the saddle plate.Within a certain range of joint parameters,the bearing capacity of stiffened K-joints can be equivalent to the superposition of K-joints and tube-gusset with saddle plates.In view of the above,the calculation formula for the bearing capacity of stiffened K-joints is proposed.The formula is applied to practical engineering joints.Finally,the influence of chord stress on the bearing capacity of stiffened K-joints and KK-joints is studied by experiment and finite element analysis.The formulas for calculating the influence of chord stress on the bearing capacity of stiffened K-joints is presented.On this basis,the relationship between the stiffened KK joints and the corresponding stiffened K joints is compared and analyzed.The results show that the bearing capacity of KK joints under different chord stress is less than that of corresponding planar K joints,and is greater than 0.9 times.