The paper addresses sensitivity analysis of free torsional vibration frequencies of thin-walled beams of bisymmetric open cross section made of unidirectional fibre-reinforced laminate. The warping effect and the axial end load are taken into account. The consideration is based upon the classical theory of thin-walled beams of non-deformable cross section. The first-order sensitivity variation of the frequencies is derived with respect to the design variable variations. The beam cross-sectional dimensions and the material properties are assumed the design variables undergoing variations. The paper includes a numerical example related to simply supported I-beams and the distributions of sensitivity functions of frequencies along the beam axis. Accuracy is discussed of the first-order sensitivity analysis in the assessment of frequency changes due to the fibre volume fraction variable variations, and the effect of axial loads is discussed too.

中文翻译：

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薄壁层合梁在轴向载荷下自由扭转振动频率的灵敏度分析

本文研究了由单向纤维增强层压板制成的双对称开口截面薄壁梁的自由扭转振动频率的灵敏度分析。考虑了翘曲效应和轴向端载荷。该考虑基于经典的不变形截面薄壁梁理论。频率的一阶灵敏度变化是相对于设计变量变化得出的。假定梁的横截面尺寸和材料属性的设计变量会发生变化。本文包括一个与简单支撑工字梁以及沿波束轴的频率敏感度函数分布有关的数值示例。