桁架结构损伤识别的单元模态应变差法

Identification of Damages of Truss Structures Using Elemental Modal Strain Method

从桁架结构的受力特点出发,利用两节点空间铰接杆单元有限元法,由节点模态位移推导出单元模态应变,提出采用损伤结构前后的单元低阶模态应变差作为桁架结构损伤定位的动力指纹,建立一种基于杆单元模态应变的桁架结构损伤定位方法。数值算例分析表明,该方法能在低阶模态测试自由度信息条件下,针对单处或多处损伤、支撑处损伤、轻微或严重损伤,以及多种损伤共存等不同损伤状况的桁架,均具有损伤定位的能力;并能根据损伤单元模态应变的差值确定出损伤程度;且在一定噪声水平下具有较强的抗噪能力,适用于实际观测条件下的桁架结构损伤定位。

On the basis of the stressed characteristics of space truss structures,the element modal strain can be deduced from the nodal modal displacement by the finite element method of space truss elements connected by pin between two nodes.Therefore the changes of the elemental modal strain in the low order are presented as the new dynamic fingerprints for damage locations of truss structures.A numerical example of the planar truss structure is provided to verify the practicability of the proposed method only by one lower mode.The results show that the proposed method is effective to locate the single damage,and multiple,light and severe damages.Damage degrees can be determined by the magnitudes of the damaged-element modal strain changes.Furthermore,the results indicate that the proposed method based on the modal strains of truss elements can accurately identify the damage location of truss structures with the noisy modal data.