基于应变模态差分原理的直接定位损伤指标法

DIRECT INDEX METHOD OF DAMAGE LOCATION DETECTION BASED ON DIFFERENCE THEORY OF STRAIN MODAL SHAPES

目前应变类损伤指标大多数只能利用损伤前后的模态参数进行损伤定位,但要得到损伤前的模态数据非常困难,难以在土木工程中推广应用。为此提出了无健康标准下基于损伤应变模态差分原理的直接定位损伤指标法ISMSD(Strain Mode Shape D ifference),只需利用损伤后应变模态数据即能定位损伤。推导了损伤应变模态等间距和不等间距差分格式。在综合考虑相邻两有效极值点间有效距离比、有效极值之差绝对值、有效极值绝对最大值的基础上,建立了直接定位损伤指标数学模型。根据理论推导和数值仿真统计分析,提出损伤位置判定准则:若某点的每阶指标值均最大,则该点有损伤;若某点的某阶或多阶指标值越大,则该点损伤可能性越大;对于某阶节点损伤,则可通过其余阶的指标值定位损伤。该指标能正确地判定损伤位置,尤其是损伤量较小情况。

Damage index of strain modal parameters can detect damage location,but the modal parameters of original structure and damage structure must be obtained.It is very difficult to obtain the modal parameters of the original structure.Therefore the method is seldom applied to damage detection in civil engineering.The direct index method of damage location detection I_(SMSD)(Strain modal Shape Difference) is put forward.It is based on difference theory of strain modal shapes(SMS) of the damage structure without that of the original structure.The equidistant and inequidistant difference schemes of SMS are deduced.Synthesizing the ratio of effective distance at adjacent extreme points,the absolute value of the effective extremum difference and the maximum absolute value of the effective extrema,the mathematics model of the direct index is given.According to theoretical derivation and statistical analysis of numerical simulations,the criteria of damage location detection are obtained.First,if the direct index value of every order SMS is the greatest at a certain site,there is damage at it.Secondly,greater the value of a certain SMS is,higher the probability of damage is.Thirdly,if the damage occurs at a nodal point of an order strain modal shape,the direct index values of other order ones are analyzed to detect damage location.The direct index method can accurately detect damage location.