Development of a Wireless Sensor to Detect Cracks in Welded Steel Connections

0000027本研究项目的目的是开发一种无线传感器，用于检测焊接钢连接中的裂纹。1994年的北岭地震对结构钢和特殊抗弯矩框架的连接造成了广泛的破坏。震中地区200多座建筑物的关键焊缝断裂；然而，由于钢构件被防火材料覆盖，检测损坏是困难和昂贵的。拆除建筑覆层和防火材料进行检查既昂贵又耗时，还会干扰建筑物居住者的正常活动。所提出的传感器依赖于射频技术。该传感器是一个谐振电路，在设计上类似于用于控制全国零售商店库存的电子物品监控贴纸。传感器将在施工期间连接到结构钢框架上，并且是被动的。当传感器下面的焊接材料或母材中的裂纹达到给定尺寸时，传感器的频率特性将发生变化。无线发射器/接收器将用于询问传感器并获取有关裂缝存在的信息，而无需移除任何建筑饰面或防火材料。所提出的裂纹检测传感器具有价格低廉、坚固耐用、易于安装和免维护等优点。该研究分为11个任务，需要将该技术转化为结构评估。必须解决的关键问题包括：为传感器的制造选择合适的组件（聚合物薄膜、线圈和胶粘剂层），确定钢材所需的表面处理，评估基于焊接连接配置的最佳传感器位置，确定最佳线圈几何形状，以及开发无线发射器/接收器，以产生频率扫描来询问多个传感器。本项目为NSF 98-36“美日城市地震减灾合作研究”第三年竞赛项目资助项目。

0000027The objective of this research project is to develop a wireless sensor to detect cracks in welded steel connections. The 1994 Northridge earthquake caused extensive damage to the connections of structural steel, special moment-resisting frames. Critical welds fractured in more than 200 buildings throughout the epicentral area; however, the damage was difficult and expensive to detect because the steel members are covered with fireproofing. Removal of the architectural cladding and fireproofing for inspection is expensive, time consuming, and disrupted the normal activities of the building occupants.The proposed sensor relies on RF technology. The sensor is a resonant circuit, similar in design to adhesive Electronic Article Surveillance stickers that are used to control inventory in retail stores around the country. The sensors will be attached to the structural steel frame during construction, and are passive. The frequency characteristics of the sensor will change when a crack in the weld material or base metal beneath the sensor reaches a given size. A wireless transmitter/receiver will be used to interrogate the sensor and obtain information about the presence of cracks without removing any of the architectural finishes or fireproofing. The proposed crack detection sensor is attractive because it is inexpensive, robust, easy to install, and maintenance free.The research has been divided into eleven tasks need to transfer this technology into structural evaluation. Critical issues that must be addressed include selection of appropriate components for manufacturing of the sensor (polymer film, wire coil, and adhesive layer) determination of required surface treatment for the steel, evaluation of optimal sensor placement based on the configuration of the welded connection, determination of optimal coil geometry, and development of a wireless transmitter/receiver to generate a frequency sweep to interrogate multiple sensors.This project is supported under the 3rd -Year Competition under NSF 98-36 "US - Japan Cooperative Research in Urban Earthquake Disaster Mitigation"