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

摘要：研究的重点是发展一种可靠的方法来更新混凝土结构的非线性有限元模型，以代表结构的损伤状态。环境反应，结合对结构的理解？的基本滞回性能，将用于生成更新的非线性有限元模型。这种更新的模型是必不可少的，以确定这些结构的剩余寿命，并确定维修/更换的优先事项。目前的全球，振动为基础的技术有能力准确地识别线弹性刚度参数的适当定义的识别模型，通过环境测试。然而，现有的损伤诊断技术主要局限于线性模型，其中的一些元素的刚度被降低，以表示通过将其与结构的模态特性的变化的损伤。研究工作的主要目标包括：获得这类结构的基本行为的理解;开发实验验证，改进的土木工程结构的非线性本构模型，可以捕捉滞回响应的显着特征;开发一种方法，用于评估的条件下，损坏的结构弹性刚度已经恶化;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，从而得到一个能够预测承载力的模型。结构的弹性刚度的退化将与识别非线性有限元模型中的本构模型的状态的一组减少的损伤参数有关。参数识别模型将被适当地构建，以将损伤参数与基于环境响应测量的降低的初始刚度值相关联。目前可用的模态识别和参数识别技术的基础上的环境振动响应将被采用和改进的弹性刚度参数的确定。

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.