The Constructing And Constructed Stage’s Nonlinear Analysis Of Liu Jia Xia Suspension Bridge

The thesis mainly analyses Liu Jia Xia suspension bridge’s linear and internal force in constructing and constructed stage. The geometry nonlinear analysis theory is used to focus on the influence of load in bridge’s constructing and constructed stage. The following lists the main study’s contents:(1) Based on the analytic theory of the cable shape, the FORTRAN program is written about empty cable and constructed stage. At the same time, using MIDAS finite element software establishes the finite element model of the construction process; In comparison to two calculation results, The author concludes that the empty cable and constructed stage’s characteristics.(2) It is calculated that cable shape、the each span’s unstressed length variation、cable saddle offsets、the cable clamps installation location of empty cable、suspenders’variation at the stiff girder installation process by using geometry nonlinear finite element method.(3) The main cable saddle’s horizontal decentering generates main towers’bending moments, To ensure the main towers’safety under bending moments, using reasonable calculation to estimate the main cable saddle’s back value.(4) In order to accurately calculate the unstressed length of main cable, it is necessary to modify the unstressed length in saddles. To solve8nonlinear equations, basing on Newton-Raphson iterative procedure, the corresponding programs is written to modify the unstressed length and to calculate the actual coordinates by using MATLAB R2006a. The results show that even if the main towers’saddle has a0offsets. Actually, the main cable saddle’s center and the of the main tower’s centroid has a offset(mid-span offset). Therefore, it should be considered to the offset during the main cable saddle pre-biased.(5) The thesis detailed analyses the suspension bridge’s structural behavior under live load, focusing on the linear and the internal forces of the most unfavorable position about the main cable in the lane load and temperature load. The conclusion demonstrates that the most unfavorable position generally presents to quarter-span nearly of the main cable and stiffening beam’s linear and the internal forces. Furthermore, using the linear second-order theory and geometric nonlinear theory to analyses the structural behavior under the lane load. The results show that the linear second-order theory’s is too large by10%than the geometric nonlinear theory’s. Therefore, during suspension bridge’s design, it is safety to calculate the structural behavior in accordance with the linear second-order theory.(6) The thesis derives the cable and truss element tangent stiffness matrix, and has a brief description to how to solve the tangent stiffness matrix equations. The unit tangent stiffness matrix obviously reflects the geometric nonlinear effect, The linear superposition principle is no longer suit.In conclusion; Suspension bridges, especially the long span suspension bridges have a pretty obvious geometric nonlinear effect. Whether the construction process or the constructed stages should be analyzed in detail, using the safer linear second-order theory’s results meet the design requirements, when suspension bridges are great cross-span, In order to reduce the structure’s own weights, make the structure’s ability into full functioned. It is necessary to using geometric nonlinear analysis methods under live load.