Direct stiffness method

About: Direct stiffness method is a research topic. Over the lifetime, 2584 publications have been published within this topic receiving 53131 citations.

Decomposition-Based Assembly Synthesis of a Three-Dimensional Body-in-White Model for Structural Stiffness

Abstract: This paper presents an extension of our previous work on decomposition-based assembly synthesis for structural stiffness, where the three-dimensional finite element model of a vehicle body-in-white (BIW) is optimally decomposed into a set of components considering (1) stiffness of the assembled structure under given loading conditions, (2) manufacturability, and (3) assembleability of components. Two case studies, each focusing on the decomposition of a different portion of a BIW, are discussed. In the first case study, the side frame is decomposed for the minimum distortion of front door frame geometry under global bending. In the second case study, the side/floor frame and floor panels are decomposed for the minimum floor deflections under global bending. In each case study, multiobjective genetic algorithm with graph-based crossover, combined with finite element methods analyses, is used to obtain Pareto optimal solutions. Representative designs are selected from the Pareto front and trade-offs among stiffness, manufacturability, and assembleability are discussed.

Second-Order Direct Analysis of Domelike Structures Consisting of Tapered Members with I-Sections

Abstract: A new and advanced beam-column element, namely the curved tapered-three-hinges (TTH) beam-column element, is proposed in this paper. The present element can perform large deformation analysis and explicitly simulate the initial member curvature, which is essential for the second-order direct analysis using one-element-per-member models. Another distinct feature of the element is to analytically express the flexural rigidity of tapered I-sections in the stiffness matrix through a series of tapered stiffness factors such as the αi and βi factors. Unlike the conventional models using the approximated distributions (e.g., linear, parabolic, or cubic) or stepped-elements modeling approaches in an analysis, the present study gives an accurate simulation solution on nonprismatic beam-column elements. Herein, the element derivations and formulations are given in detail. To consider the large deflection effect in the analysis, the incremental tangent stiffness method is adopted and the kinematic descriptio...

Testing the Predictive Capability of the High-Fidelity Generalized Method of Cells Using an Efficient Reformulation

Abstract: The High-Fidelity Generalized Method of Cells is a new micromechanics model for unidirectionally reinforced periodic multiphase materials that was developed to overcome the original model's shortcomings. The high-fidelity version predicts the local stress and strain fields with dramatically greater accuracy relative to the original model through the use of a better displacement field representation. Herein, we test the high-fidelity model's predictive capability in estimating the elastic moduli of periodic composites characterized by repeating unit cells obtained by rotation of an infinite square fiber array through an angle about the fiber axis. Such repeating unit cells may contain a few or many fibers, depending on the rotation angle. In order to analyze such multi-inclusion repeating unit cells efficiently, the high-fidelity micromechanics model's framework is reformulated using the local/global stiffness matrix approach. The excellent agreement with the corresponding results obtained from the standard transformation equations confirms the new model's predictive capability for periodic composites characterized by multi-inclusion repeating unit cells lacking planes of material symmetry. Comparison of the effective moduli and local stress fields with the corresponding results obtained from the original Generalized Method of Cells dramatically highlights the original model's shortcomings for certain classes of unidirectional composites.