Research On Parallel Computing Of Concrete-faced Rockfill Dam

Numerically solving the concrete-faced rockfill dam is a rather complex and high nonlinear issue.Because of forming the total stiffness matrix in serial solution using FEM (Finite Element Method),element number of the model increases significantly as the structural scale enlarges,even if with variable bandwidth storages,which results in that the capacity of computer memory is insufficient,and that calculative time is long.It can't meet the needs of engineering application and research.Therefore the analysis of concrete-faced rockfill dam by FEM has increased the demand for high-performance computing.The multi-frontal method based substructure is very good for parallel computing due to adopting the strategy of "divide and conquer".Based on model features and calculation characteristics of the concrete-faced rockfill dam,the parallelization of its numerical analysis was implemented.A parallel multi-frontal code for COW was developed and applied to the numerical analysis of Xilongchi lower reservoir dam,an asphalt concrete faced rockfill dam. The work about parallel computing of the concrete-faced rockfill dam has been carried out as follows.Research on substructure parallel algorithms with multi-frontal processing technique has been performed.The structure is first divided into some substructures.Then,the independent fronts can be assembled and condensed in each processor.As a result,the condensed interface stiffness matrices and load vectors are obtained.By assembling with communication between processors and serially solving the global interface equation to get displacements and then backing to every substructure in parallel,the inter-nodal displacements and element stresses are computed.According the modeling feature of a concrete-faced rockfill dam,intrinsic parallelism that some neighbouring dam sections could make up of a substructure has been analyzed. Two parallel schemes which are the first serial and last parallel arithmetic and the full parallel arithmetic have been designed by the computation characteristic that substructures are variable in the process of filling dam by different level.On the basis of existing 3-D nonlinear FEM static serial program,the author programmed a parallel code using FORTRAN and MPI language.Parallel program can be applied to FEM numerical simulation of Xilongchi lower reservoir dam,an asphalt concrete faced rockfill dam successfully.By analyzing speedup ratios and parallel efficiency,the conclusion shows that the parallel multi-frontal method can be used to reliably analyze the concrete-faced rockfill dam.