Mechanical Properties Of U-shaped Steel Damper And Its Application In Beam-column Joints Of Steel Structures

In the traditional design of beam-to-column joints of steel structure,the rigid joints with bolted-welded joint or fully welded joint were widely used in steel structures in the mid-20 th century.However,the investigation of the damage caused by the 1994 Northridge earthquake in the United States and the 1995 Kobe earthquake in Japan shows that a large number of brittle damages are found at the beam-column joints of steel structures with such rigid joints,the plastic deformation of steel is not expected to absorb seismic energy,which leads scholars at home and abroad to think about beam-column joints of steel structure and make extensive research.Based on this background,it is one of the improvement measures to install energy dissipation damper at beam-column joints of steel structure in recent years.On the other hand,the U-shaped metal damper is a typical representative of the first generation of metal dampers.It is composed of the upper straight line segment platform,the middle curved circular arc segment and the lower straight line segment platform,it is still one of the most widely used metal dampers.In this paper,a semi-rigid joint with energy dissipation and shock absorption property is formed by installing U-type metal damper in beam-column joints of steel structure,firstly,the mechanical properties of U-shaped metal dampers under tension and compression are studied,secondly,the U-shaped metal dampers are installed to beam-column joints of steel structure,and their mechanical responses are analyzed,the research contents are as follows:(1)Based on the relative tensile and compressive deformations at the opening of the U-shaped metal damper,the mechanical model of the damper is established,and the expression of its mechanical properties is studied,and the plastic failure mechanism is clarified,the accuracy of the expression is verified by experiment and numerical finite element analysis.(2)The U-shaped steel damper is installed in the beam column joint of steel structure to form a semi-rigid joint.The energy dissipation characteristics and mechanical response of each member are verified by the test and numerical finite element analysis.In the analysis,the number of U-shaped steel damper is single or double,and the opening direction is different.(3)Taking the portal frame as the research object,the difference of mechanical response between rigid joints and semi-rigid joints with U-shaped steel dampers is analyzed by numerical finite element method.The analysis mainly focuses on the category of component level.(4)Taking the multi-storey and multi span plane frame as the research object,the difference of mechanical response between pure rigid joints and rigid semi-rigid joints is analyzed by numerical finite element method.The analysis mainly focuses on the overall response of structural system.The results show that:(1)The U-shaped steel damper has the property of energy dissipation damper when the relative tension and compression deformation occurs at the opening.The mechanical performance expression shows that there is a coupling of vertical force and bending moment at the end of the U-shaped steel damper.The experimental results show that the mechanical performance expression derived in this paper has good accuracy and can describe the plastic failure mechanism of U-shaped steel damper.At the same time,the opening direction of the U-shaped steel damper has an impact on the mechanical response of the member;(2)The U-shaped metal damper is installed in the study of inverted T-shaped semi-rigid joints in steel structure beam-column joints.The results of quasi-static test and numerical finite element analysis show that the hysteretic curve of the semi-rigid joint is full,the stiffness degradation is small,the ductility coefficient and the equivalent viscous damping coefficient are good,and the semi-rigid joint has good hysteretic performance and damping performance.;(3)In the analysis of portal steel frame,although the initial stiffness and yield load of semi-rigid joints are lower than those of rigid joints,and the yield displacement is higher,the beams and columns do not yield;(4)In the comparative analysis of the overall response of multi-storey and multi span plane steel frame structure system,the plastic failure path of rigid semi-rigid joints first occurs U-shaped steel damper.It also shows that the U-shaped steel damper installed in the beam column joints of steel structure has good energy dissipation effect.