| Orthotropic structures are widely used in engineering practices, the combination ofthe sub-structures in the orthogonal directions based on the stiffness requirements atdifferent directions, makes the overall structure having the new capabilities, while alsohaving advantages of easy-fabricating and saving material. However, compared to theconventional structures, orthotropic structures are tend to having more details, whichwould bring new challenges to numerical modeling and analysis. Fine modeling of thewhole structure would cause very large number of system equations. In equivalent andsimplify modeling, different mechanical properties caused by structural differences in alldirections of the model also need to be fully considered. Yet in previous studies, thisproblem is often neglected. In the equation solving, especially in dynamic analyses, thefine grid of the local details often drastically reduce the simulation time step, which wouldgreatly increase the calculation amount.This work investigates the space-time domain multiscale dynamics simulation methodfor large-scale orthotropic structures based on the practical engineering background. Themain contents are as follows:The equivalent&multiscale modeling method for large-scale orthotropic structure, aswell as the high-performance asynchronous time domain integration algorithm are studied.The widely used representative volume element (RVE) method in material mechanics wasextended to the equivalent modeling of large-scale orthotropic structures. The dynamiccharacteristics of the whole structure which representing the integral dynamic propertieswere used as the objective function, the optimal nominal material parameters weredetermined by the inverse analysis and mathematical optimization methods, consideringthe structural differences in the orthogonal directions. The implementation of the method issimple, and the resulting equivalent nominal parameter can well reflect the actual dynamicproperties of the structure. In the multi-scale modeling coupling, based on perturbationtheory, the constrained equations at the interface of elements with different scales werederived using relation of equality of work. And their accuracies are verified by numericalexamples. Meanwhile, since large multi-scale FEM of orthotropic structure often has ahuge amount of system equations and small local critical time step, an improved high performance parallel solution method based on the central difference method and therecursive partitioning algorithm was proposed. The subcycling method grades the elementsof the model into groups with different critical time steps, and information of the interfacenodes was interpolated by taking a linear velocity or acceleration assumptions. Accordingto the supercomputer architecture and the subcycling central difference algorithm’sfeatures, an optimized recursive coordinate bisection method, with an impact factorconsidering the influences of the asynchronous integration algorithm, was proposed. Theproposed solving procedure can greatly save the computational resources, reduce solutiontime, while the parallel computation efficiency for processing the multi-scale model inspace&time domain is also guaranteed.Taking the West Yangtze River Road Tunnel as a case study, the multiscale seismicanalysis of large scale shield tunnel was carried out. The multi-scale analysis methods ofthe tunnel at various levels are explored and verified, including the contact surface level,segment level, the global scale as well as the mixed scales level. Fine modeling methodwas developed and validated for the tunnel lining assembly. The optimal effectiveparameters of the tunnel lining were determined using the anti-analysis idea andoptimization methods. Then, the seismic analysis model of the West Yangtze River RoadTunnel is established, and the critical sections were accessed through the comprehensiveevaluation of the integral tunnel internal forces. The multiscale dynamic model of thetunnel was established by planting the validated segmental model into the globalequivalent model, and the seismic performance of the integral tunnel, as well as the jointsdetails were analyzed and summarized.Taking the Xidu Bridge as a case study, the multiscale dynamic analysis of theship-bridge collision process was carried out. By equivalently model the upper and lowerdeck as the orthotropic plates, the multiscale model of the bridge was established. Theinitial state of the ship was established through the dynamic relaxation method, and thecable tension and deck configuration were amended and certificated with the design data.The “V” shaped bulk carrier was used as the impacting ship, and the multiscale model of itwas built by dividing the ship into impacting, non-impacting and the transition zones withdifferent element sizes. Then, the ship-bridge collision process were analyzed in detail. Theimpact forces got form the FEA and empirical formulae in technical manuals werecompared, and the reasons that where the differences came from were summarized.The present paper also introduces an arbitrarily mixed explicit-implicit asynchronous integration algorithm based on uniform Newmark discretization format, for the efficientlysolving of the large and complex dynamic systems. The overall dynamical system can bepartitioned into different parts according to the physical and mechanical properties, as wellas the requirements of solution accuracy, and the system equation can be solved inmulti-scale both at the space domain and time domain. According to the inherent messagepassing mechanisms of the explicit and implicit algorithm, a variable boundary treatmentmethod was adopted to avoid the accumulation of errors at the asynchronous boundary.The simulation time steps were dynamically determined and corrected according to theenergy balance checking, which can effectively prevent the emergence and development ofthe instability. Numerical examples show that the proposed algorithm can greatly reducethe consumption of computing resources while maintaining high accuracy, thus it has ahigh practical value. |
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