Block diagonal and higher order mass matrices for Hermite beam elements
Received:September 09, 2023  Revised:October 20, 2023
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DOI:10.7511/jslx20230909002
KeyWord:Hermite beam element  vibration frequency  lumped mass matrix  block diagonal mass matrix  higher order mass matrix
        
AuthorInstitution
王东东 厦门大学 土木工程系 福建省滨海土木工程数字仿真重点实验室, 厦门
吴振宇 厦门大学 土木工程系 福建省滨海土木工程数字仿真重点实验室, 厦门
侯松阳 厦门大学 土木工程系 福建省滨海土木工程数字仿真重点实验室, 厦门
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Abstract:
      The lumped mass matrices of Hermite finite elements for Euler-Bernoulli beams are often constructed by the row sum technique via neglecting the rotational entries, or by the nodal quadrature.However, such lumped mass matrices of Hermite beam elements exhibit a sudden drop of accuracy in frequency calculation in case of free boundary conditions.In this study, based upon the numerical integration accuracy requirement, the gradient-enhanced nodal quadrature rules are developed for both cubic and quintic elements.These nodal quadrature rules lead to a block diagonal form of element mass matrices, while the assembled global mass matrix still preserves a desirable diagonal pattern except a few entries associated with the boundary nodes.The block diagonal mass matrices of cubic and quintic elements have an optimal convergence rate of 4 and a sub-optimal convergence rate of 6, respectively.Subsequently, through rationally mixing the consistent mass matrices and the mass matrices generated by the gradient-enhanced nodal quadrature rules with equal accuracy orders, superconvergent higher-order mass matrices are attained for cubic and quintic Hermite beam elements.The accuracy and robustness of the proposed block diagonal and higher-order mass matrices are systematically demonstrated by numerical results.