Experimental And Theoretrical Study Of Eccentrically Braced Structure Applying For Modern Steel Structure

According to the design ideas of associating work of two or more energy components, a new braced steel frame system—energy dissipating eccentrically brace is proposed, which adds an endergonic device in diagonal brace. Because of the shortcomings of current beam-column joint of D-type eccentrically braced frames, one new reinforced connection protocol between shear links and column—adding cover-plate is advanced, which is used to enhance moment and shear bearing capacity of beam. Major works are shown as follow:1) The quasi-static experiment on three 1/3 eccentrically braced model frames is described first. Compared with ordinary beam-column joint of D-type eccentrically braced frames, this paper primarily study the failure mechanism and seismic performance of two new type of eccentrically braced frames under cyclic loading and analyzes the energy capacity and ultimate strength of two new frames shown above.2) The finite element models are created by ANSYS Program. We can receive the result of backbone curve about eccentrically braced frames by analyzing the failure mechanism and seismic performance of two new eccentrically braced frames under cyclic loading and researching the energy capacity and ultimate strength of two new frames shown above.3) Comparison of finite element analysis and test results to verify the accuracy of finite element analysis.4) Using ANSYS Program, study the energy capacity of two new eccentrically braced frames by changing the relevant parameters and propose the improvement measures of two new eccentrically braced frames.The main results of this study according to the comparison of the test results and finite element results are listed below:1) The setup of A segment can draw the formation of shear hinges and flexural hinges away from column face, preclude yielding in the link, and relax the extreme local deformation in the link flanges. It can also avoid the appearance of lamellar tearing and reduce the mending after the earthquake according to the design purpose of the new type.2) The premise condition of the adding cover-plate protocol applying for eccentrically braced frame is that the link must be shear and the length summation of the link and A segment must be less than 1.6M_p/V_p.3) The thickness of cover-plate almost did not have any influence on carrying capacity and dissipating energy of structure. Some factors which affect resisting seismic behavior were the thickness of the connection-plate between beam and column, adding stiffeners, and the decrease of the length of A segment etc.4) The diagonal energy dissipating eccentrically braced frame: the setup of endergonic device equals the setup of a weak part in the brace. After the link yielded, the endergonic device slipped, dissipated energy along with the link and increased the ductile of the specimen. It can reduce the input energy and the rotation deformation of the link. It provided double insurance and realized the purpose of decreasing the seismic action.5) In the elastic phase, the endergonic device should not slip. The brace is the major component to resist the lateral load. After the link yielded, the endergonic device began to slip and deform to dissipate energy.6) The increase of the stiffness of the endergnic device strengthens the stiffness of the frame and enhances the carrying capacity. The rotation of link increased, and the displacement of top column decreased obviously. Finally the specimen failed because the lateral buckling of the endergnic device. In the design of energy dissipating eccentrically brace, the stiffness should be enhanced properly and some strengthen details should be introduced in C segment.