Research On Mechanical Performance Of K-joint Plane Truss Structure

Portal frame is widely used in civil engineering. The portal frame would be damaged due to some reasons in engineering. It is always been the focus of attention that whether the damaged portal frame can meet the requirements of normal use and whether it need to reinforcement or reconstruction. This thesis analyzes the mechanical behavior of the damaged beam-column connections and analyzes the mechanical behavior of the damaged portal frame structure according to the experimental study on mechanical behavior of damaged steel. The following work is done in this thesis:(1) This thesis studies the mechanical behavior of damaged steel specimens by the standard test of 8 groups of Q235 steel specimens and obtains the numerical data of the loading elastic modulus and Unloading elastic modulus.This thesis establishes the mechanics analysis model of damaged steel.(2)Beam-column joint model of the finite element analysis is established with software ANSYS. Rotational deformation of the joint applied the moment to will change with the height of the beam, the width of the beam flange, the thickness of the beam flange and the elastic modulus in damaged area. Beam-column joint rotational deformation formula is obtained by fitting the data of finite element analysis with single independent variable. The stiffness of the Beam-column joint is obtained by numerical fitting method.(3) A new calculation method is obtained by deriving the unit stiffness matrix of members, which can take the second-order effect in consideration. The FORTRAN language is used to compile the calculation process. The mechanical behavior of the damaged portal frame is analyzed by using newly compiled calculation process,which is compared to many calculation results. The analysis results show that the node damage have some effects on mechanical behavior of steel structure which cannot be ignored.