Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08540, USA.
Sensors (Basel). 2018 Mar 1;18(3):734. doi: 10.3390/s18030734.
Temperature changes play a large role in the day to day structural behavior of structures, but a smaller direct role in most contemporary Structural Health Monitoring (SHM) analyses. Temperature-Driven SHM will consider temperature as the principal driving force in SHM, relating a measurable input temperature to measurable output generalized strain (strain, curvature, etc.) and generalized displacement (deflection, rotation, etc.) to create three-dimensional signatures descriptive of the structural behavior. Identifying time periods of minimal thermal gradient provides the foundation for the formulation of the temperature-deformation-displacement model. Thermal gradients in a structure can cause curvature in multiple directions, as well as non-linear strain and stress distributions within the cross-sections, which significantly complicates data analysis and interpretation, distorts the signatures, and may lead to unreliable conclusions regarding structural behavior and condition. These adverse effects can be minimized if the signatures are evaluated at times when thermal gradients in the structure are minimal. This paper proposes two classes of methods based on the following two metrics: (i) the range of raw temperatures on the structure, and (ii) the distribution of the local thermal gradients, for identifying time periods of minimal thermal gradient on a structure with the ability to vary the tolerance of acceptable thermal gradients. The methods are tested and validated with data collected from the Streicker Bridge on campus at Princeton University.
温度变化在结构的日常结构行为中起着重要作用，但在大多数当代结构健康监测 (SHM) 分析中作用较小。温度驱动的 SHM 将温度视为 SHM 的主要驱动力，将可测量的输入温度与可测量的输出广义应变（应变、曲率等）和广义位移（挠度、旋转等）相关联，以创建描述结构行为的三维特征。确定最小热梯度时间段为温度-变形-位移模型的构建提供了基础。结构中的热梯度会导致多个方向的曲率，以及横截面上的非线性应变和应力分布，这会极大地增加数据分析和解释的复杂性，扭曲特征，并可能导致对结构行为和状况的不可靠结论。如果在结构中的热梯度最小时评估特征，则可以最大程度地减少这些不利影响。本文提出了两类方法，基于以下两个指标：(i) 结构上原始温度的范围，和 (ii) 局部热梯度的分布，用于识别具有可变化的可接受热梯度容限的结构上的最小热梯度时间段。该方法使用从普林斯顿大学校园内的 Streicker 桥收集的数据进行了测试和验证。
