Nonlinear Model Updating Using Ambient Responses For Damage Diagnosis In Concrete Structures

摘要：研究的重点是开发一种可靠的方法来更新混凝土结构的非线性有限元模型，以表示结构的损伤状态。环境反应，结合对结构的理解？S的基本滞回行为，将用于生成更新的非线性有限元模型。这种更新的模型对于确定这些结构的剩余寿命和确定维修/更换优先事项至关重要。目前，基于振动的全球技术能够通过环境测试准确地识别出适当定义的识别模型的线性弹性刚度参数。然而，现有的损伤诊断技术主要局限于线性模型，其中一些单元的刚度被降低，通过将其与结构模态特性的变化联系起来来表示损伤。研究工作的主要目标包括：了解这类结构的基本行为；开发经过实验验证的改进的土木工程结构非线性本构模型，可以捕捉滞回响应的显著特征；开发一种评估弹性刚度恶化时受损结构状态的方法；验证所提出的方法，将结构损伤与弹性刚度的变化联系起来，从而产生一个能够预测容量的模型。结构弹性刚度的退化将与一组减少的损伤参数有关，这些参数可以识别非线性有限元模型中本构模型的状态。根据环境响应测量值，适当地构建参数识别模型，将损伤参数与减小的初始刚度值联系起来。现有的基于环境振动响应的模态识别和参数识别技术将被用于确定弹性刚度参数。

Abstract: The focus of the research is on the development of a reliable method to update nonlinear finite element models of concrete structures to represent the damaged state of the structure. Ambient responses, combined with an understanding of the structure?s fundamental hysteretic behavior, will be used to generate the updated nonlinear finite element model. Such updated models are essential for determining the remaining lifetime of these structures and identifying repair/replacement priorities. Current global, vibration-based techniques have the ability to accurately identify linear elastic stiffness parameters for an appropriately defined identification model through ambient testing. However, existing damage diagnosis techniques are primarily limited to linear models in which the stiffness of some of the elements is reduced to represent damage by relating it to the change in the modal characteristics of the structure. The primary goals of the research efforts include: gaining an understanding of the fundamental behaviors of this class of structures; developing experimentally-verified, improved nonlinear constitutive models for civil engineering structures that can capture the salient features of the hysteretic response; developing a method for the assessment of the condition of a damaged structure when the elastic stiffness has deteriorated; validating the proposed methodology to relate structural damage to changes in elastic stiffness, resulting in a model that will be able to predict the capacity. Degradation in the elastic stiffness of the structure will be related to a reduced set of damage parameters that identify the state of the constitutive models in the nonlinear finite element model. Parametric identification models will be constructed appropriately to relate the damage parameters to the reduced initial stiffness values based on ambient response measurements. Currently available modal identification and parameter identification techniques based on ambient vibration responses will be employed and improved for determination of elastic stiffness parameters.