Effectiveness of Boundary Conditions on System Stiffness of Beam-like Structure

The framework of automobile body is constructed by numbers of beam-like structural members.Besides the cross-sectional shapes and dimensions of these beams,the boundary conditions also influence the system stiffness heavily.This paper discusses the synthetic stiffness of beam system under various boundary conditions and load patterns.Based on the bending and torsion stiffness of a two-end-fixed beam with uniform cross-section,the contributions of all connection stiffnesses to system stiffness are studied and corresponding charts are plotted respectively.At the end,both the actual bending stiffness and torsion stiffness of a cross beam for automobile instrument panel are calculated by the derived analytical formulae and finite element method.The static stiffness formulae obtained in this paper are also suitable for other beam-like structure.