A Novel Nonlinear Link Element for Direct Second-Order Analysis of Trusses Assembled by Weak Shear Stiffness Members

摘要

The transverse shear effect and initial imperfection have significant influence on the post-buckling performance of weak shear stiffness struts such as pultruded fiber reinforced polyester (FRP) members and lattice column. A novel nonlinear link (NNL) element was proposed to perform direct second-order analysis of trusses assembled by such members. Adopting the Engesser approach to account for shear deformability, the expressions of transverse deflection under tensile and compressive load were obtained respectively. Taking the linear tension-compression deformation and bowing effect into account, the correction coefficients of axial stiffness for FRP truss member under tension and compression were obtained. Combined with ANSYS UPFs -user programmable features, the user-defined NNL element was established. Both pultruded FRP profiles and lattice column were modeled separately by standard commercial elements and the proposed NNL element. The comparison of the obtained results verified the convenience of the NNL element in modeling and computing. Moreover, the NNL element was adopted to model and calculate two FRP plane truss structures, and the calculation result was compared with test result. It demonstrated that the NNL element can accurately predict structural stiffness change and change points during successive buckling of certain truss members, showing the promising usage of NNL element in structural design of other FRP truss structures.