Non-Destructive Testing Campaign on a Steel Bridge through Acoustic Emission Sensors and Accelerometers
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An in-situ data acquisition campaign both for local structural diagnosis and vibrational system identification was conducted on a steel bowstring girder bridge with a span length of 65m and a width of 16m. The bridge was simply supported, and the deck consisted of a two-cell box girder with transversal diaphragms connected to lateral cantilever beams. These diaphragms and cantilever beams were spaced 3.6m apart. The deck included a central and two lateral reinforced concrete curbs. NDTs for local structural diagnosis were carried out using acoustic emission (AE) sensors, while accelerometers were employed to evaluate the vibrational properties of the bridge. With respect to AE acquisitions, finite element (FE) analysis identified critical stress points on the lower plate of the box girder, particularly around the welds near midspan. Due to logistical issues, testing was conducted as close to midspan as possible, specifically between the 3rd and 4th cantilever beams, along the longitudinal weld. Six AE sensors were used in total, with three placed on each side of the weld, arranged in a 20cm x 20cm grid pattern. The AE acquisition was hit-based, meaning only data exceeding a specific amplitude threshold was recorded. The monitoring lasted for 2 hours and 15 minutes. The raw data collected were automatically processed by the DAQ software, which provided the primary data that were analyzed to perform a local structural diagnosis of the weld. Results showed no significant hits exceeding 90dB for durations longer than 30ms, revealing the detail to be safe. Regarding acceleration measures, accelerometers were disposed at the four quarters of the bridge span on the central concrete curb, recording in one, two or three directions, according to the image provided. The recordings lasted 2h. The data permitted to identify the frequencies and mode shapes of the bridge. This study was supported by funding from the RELUIS-CSLLPP consortium as part of the DPC-ReLUIS 2022-2024 project.
本研究针对一座跨度65米、宽度16米的简支钢弓弦主梁桥开展原位数据采集工作，采集所得数据同时用于局部结构诊断与振动系统辨识。该桥梁为简支结构，桥面采用双室箱梁体系，搭配横向隔板与侧向悬臂梁相连，隔板与悬臂梁的布置间距为3.6米；桥面设有中央混凝土缘石及两侧侧向混凝土缘石。本次局部结构诊断的无损检测（Non-Destructive Testing，NDT）采用声发射（Acoustic Emission，AE）传感器实施，同时通过加速度计评估桥梁的振动特性。 针对声发射数据采集环节，有限元（Finite Element，FE）分析确定了箱梁底板的关键应力点位，尤其集中在跨中附近的焊缝区域。受后勤条件限制，测试尽可能贴近跨中开展，具体布置于第3至第4根悬臂梁之间的纵向焊缝处。本次共部署6台声发射传感器，焊缝两侧各布置3台，呈20cm×20cm的网格状排布。声发射采集采用撞击事件触发模式，即仅记录超过特定幅值阈值的信号。本次监测持续2小时15分钟，采集到的原始数据由数据采集（Data Acquisition，DAQ）软件自动处理，生成用于该焊缝局部结构诊断分析的核心数据。分析结果显示，未出现幅值超过90dB且持续时长超过30ms的有效撞击事件，表明该焊缝区域结构安全。 关于加速度测量环节，加速度计被部署在中央混凝土缘石上的桥梁跨度四等分点位处，依据所提供的图像，采集维度涵盖单方向、双方向或三方向。本次记录时长为2小时，采集所得数据可用于识别桥梁的固有频率与振型。 本研究由RELUIS-CSLLPP联盟提供资助，属于DPC-ReLUIS 2022-2024项目的一部分。
