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

0000027该研究项目的目标是开发一种无线传感器来检测焊接钢连接中的裂纹。1994年北岭地震对结构钢、特殊抗弯框架的连接造成了广泛的破坏。整个震中地区有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，因此检测损坏很困难且昂贵。拆除建筑覆层和防火层进行检查是昂贵的，耗时的，并且扰乱了建筑物居住者的正常活动。该传感器是一个谐振电路，在设计上类似于粘性电子商品监视贴纸，用于控制全国各地零售商店的库存。传感器将在施工期间附接到结构钢框架上，并且是被动的。当传感器下方的焊接材料或母材金属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得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。提出的裂纹检测传感器是有吸引力的，因为它是廉价的，强大的，易于安装，和免维护。必须解决的关键问题包括选择适当的组件来制造传感器（聚合物膜、线圈和粘合剂层）确定钢所需的表面处理，基于焊接连接的配置评估最佳传感器放置，确定最佳线圈几何形状，和无线发射器/接收器的开发，以产生频率扫描来询问多个传感器。该项目是在NSF 98-36“US -日本城市防震减灾合作研究”

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"