Dynamic Research On Rigid-flexible Coupling System Of Bridge Inspection Truck With Lattice Structure Under Large Motion

This subject comes from the sub-topics (2008BAJ09B01-3) named large bridgeinspection and maintenance equipment which is contained in National EleventhFive-Year Technology Support Project ‘Research and industry development onscaffold-less installation equipment’. Bridge inspection truck is a type of specialvehicle to test safety of bridge. The processes of the erecting and slewing brakingare complex large-range flexible motion processes. The jib system of lattice bridgeinspection truck is a mobile flexible beam system, which is a type of rigid-flexiblecoupling system composed of rigid motions of concomitant coordinates fixed withmotive mechanisms and elastic dynamic deformations of elastic mechanisms. In theprevious analysis, attention of slight movement under the state of smalldisplacements in the inspecting condition for bridge is paid. Bridge inspection truckis analyzed with slight movement in the exciting force of acceleration and inertiaforce from starting-braking process. Rigid body dynamics analysis is used in theerecting condition, and the real elastic dynamic analysis is substituted by kinematicstatic analysis by applying contained acceleration and inertia force to constrainedelastic structure. This method does not match the actual working model. For latticebridge inspection truck, this paper applies rigid multi-body dynamic analysis to theerecting process, flexible multi-body dynamic analysis to the flexible slewingbraking process and mobile flexible dynamic analysis considered of rigid-flexiblecoupling effects. The purpose of this project is to find an effective multi-bodydynamic analysis method for lattice bridge inspection truck consisting of elasticcomponents, which is both consistent with the actual working model and convenientfor the practical analysis and calculation.This paper implements the rigid-flexible coupling dynamics analysis to latticebridge inspection truck based on the flexible multi-body system dynamics analysismethods, which considering the movement elastic dynamic analysis method onlarge-scale movement beams with the second-order effect.First, equivalent element integration method is used for rigid multi-bodydynamics analysis in the erecting condition. Considering multiple degrees offreedom, displacement, velocity and acceleration of the jib system, motion parameters of mechanism and variation of the cylinder force are obtained, whichprovide a theoretical basis for the design for lattice bridge inspection truck.Then, the deformation field of flexible element is built using cubic splineinterpolation function. The geometric nonlinear stiffness matrix of the planar andspactial Euler-Bernoulli beam element is derived in the static conditions which isconsistent with the traditional beam element in the form. Through the analysis ofplanar and spatial structure, the results show that the calculation precision of newelement from this method is much higher than traditional beam element, and themethod has a good applicability.Flexible multi-body system dynamics equations of planar and spatial motionwere established by the general principle of virtual displacement. Flexiblemulti-body system dynamics analysis with second-order effect is implemented toobtain the deformation of the end of vertical telescopic boom in the braking processwhich cannot be derived from rigid multi-body dynamics analysis method.In the aforementioned flexible system dynamics modeling of the lattice bridgeinspection truck, equivalent flexible element method is used for substructures of thelattice component, then every beam element is analyzed in strength calculationanalysis of actual structure. In the process of erecting and working of the entirebridge inspection truck, force of every beam changes due to different workingconditions, and the moment of max force is also changing. For ensuring the safetyand reliability, calculation analysis is extremely important to the whole process ofthe various conditions. Therefore, dynamics of flexible multi-body system is usedfor specific conditions of bridge inspection truck. Considering coupling terms aboutlarge motion of rigid body and elastic small deformation, an analysis method ofdynamic system is built coupling motion lattice structure and flexible mechanisms.A method of high efficient modeling and calculating solution which is suitable forengineering applications is implemented on the base of accurate theoretical analysis.For the slewing braking condition, because of its spatial structure and large quantity,finite element program for dynamic analysis based on Compaq Visual Fortran6.1iscompiled. The changing on deformation and forces of each bar with time is obtained.The effectiveness of calculating theory and analysis method from this paper isverified by compared with the test result of experimental prototype. This is not onlymeaningful for flexible mechanism with large range motion like lattice bridge inspection truck, but also large reference value for similar movement lattice system.