Study On Nonlinear Mechanical Behavior Of Special-shape Arch Bridge And Analysis Of Its Dynamic Chara Cteristics

Several calculation and analysis modules are compiled in Fortran language and then against the special-shape arch bridge represented by butterfly-shape arch bridge, the geometrical nonlinearity, optimization of cable tension in construction stage and dynamic impact factors are studied based on the construction monitoring project of the butterfly-shape arch bridge in south central region of Taiyuan City. The main research contents include:1. The stiffness matrix of spatial tapered beam element in integration scheme is deduced; the program module on geometrical nonlinearity analysis of structure is compiled. Alternative managements are given to various special problems in the module, such as adopting romberg integration to count stiffness matrix of tapered beam element, transforming coordinates by three coordinate axis rotation, considering the shearing deformation on element stiffness matrix or not, calculating stiffness matrix of element with any rigid arm, releasing beam-end restraint, solving master-slave constrains with any correlation through row and rank transformation;two-stage identifiers are set in nonlinearity analysis program modules, among which, sub identifiers of main cable,stay cable and side cable are set under identifiers of cable sag, sub identifiers of arch rib elements and main girder elements are set under identifiers of beam-column effect, and sub identifiers of lateral displacement and vertical displacement are set under identifiers of large displacement effect.2. Taking the butterfly-shape arch bridge in south central region of Taiyuan City as an example, explanation to mechanical behavior of special-shape arch bridge is conducted; on the basis of nonlinear finite element program, geometrical nonlinearity character of structure in typical construction stage as well as that of arch rib, main girder and cable under dead and live load in finished bridge state are described using independent model; further research on nonlinear effects of lateral displacement and vertical displacement of nodes, beam-column effects of arch rib and girder element, and sag effects of three kinds of cables on different contents are provided; influences of angle of depression, rise/span ratio, steel ratio, stand density and arrangement form of cables on geometrical nonlinearity character of structure are discussed; through contrasts of various new bridges such as crescent-shaped arch bridge, flying-swallow-type arch bridge and arch pylon cable-stayed bridge, a summary on geometrical nonlinearity characters of various special-shape arch bridges is made.3. As with the use of stability analysis program, influencing factors of stability of butterfly-shape arch bridge and the influence degree are studied by the alteration of design parameters on the basis of original design of the bridge.4. The secant iterative method used for cable tension optimization in construction stage is put forward and put into comparison with traditional forward-analysis iterative method. According to condition monitoring, some basic principles and methods for the determination of the adjusted order and cable initial tension in view of arch-beam composite structured bridge are proposed, and those methods are proved to be effective in comparison with measured data; sensitivity of various cables in finished bridge state are analyzed, on the above basis, a new way for the adjust order of different cables is put forward in view of the complicated multi-cable bridge.5. As with the adoption of subspace iteration method, the calculation program used to analyze self-vibration characteristic of structure is compiled, and the results are brought into comparison with measured data; the road surface roughness is simulated using the numerical method and vehicle-bridge coupling vibration analysis based on coupling system model are conducted, on the basis of related calculation program, influences of running speed, unbalance loading distance, structural damping, road surface roughness, moving direction, wheelbase, vehicle gap, and arrangement form of cables on dynamic impact coefficients of the special-shape arch bridge are studied, simultaneously, effects of various design parameters such as angle of depression and rise/span ratio on dynamic characteristics of structure are presented.