火灾下钢-混凝土组合楼盖的声发射特性
Acoustic emission characteristic of steel？？concrete？？composite floor during fire

为研究火灾下钢？不炷？土组合楼盖的声发射特性，利用声发射采集仪对火灾下长跨跨中布置次梁的足尺钢？不炷？土组合楼盖进行监测。火灾模拟环境为ISO 834标准升温曲线，通过对钢？不炷？土组合楼盖的板角、周边、跨中等关键位置处的声发射数据进行滤波分析，研究典型的声发射特征参数（计数、累计计数、幅值和能量），并结合试验破坏的宏观现象，探讨了火灾下钢？不炷？土组合楼盖的传力机理及与声发射参数特征的关联。研究结果表明：火灾作用下钢？不炷？土组合楼盖的声发射参数随截面温度的非线性变化表现出不同的特征，且与混凝土板面上裂缝开展的不同阶段相吻合，这与材料和结构的力学行为密切相关；试验过程中，声发射源信号在升温初期最为活跃，这与声发射信号中计数（振铃）和累计计数曲线的转折点特征吻合，可以用来反映裂缝开展的过程、分布区域和密集程度；声发射事件在空间位置上的分布特征变化是结构失稳和内部损伤产生的重要前兆，声发射信号本身的强弱（幅值、能量等参数）需特别关注；降温时，组合结构中钢梁、混凝土板间热膨胀系数的差异使得两者之间会有错动产生，直接导致该阶段的声发射信号仍然较为活跃，建议今后建立火灾下结构倒塌的声发射预警系统时予以关注。
To study the acoustic emission (AE) characteristics of a steel？？concrete composite floor during a fire, a Micro？并？ multichannel digital AE instrument was used to conduct AE nondestructive monitoring during a fire on a full？？scale composite floor，which had a secondary frame beam arranged along the short spans in the middle of long spans. The simulated fire environment was based on the ISO 834 international standard curve. AE signal data of measuring points were collected for filtering analysis at critical locations，such as the positions of corner, perimeter, and mid？？span in the composite floor. Through analyzing typical AE characteristic parameters, such as ringing count, cumulative count, amplitude, and energy, and combining them with the experimental phenomena during the tests, the load？？transferring mechanism and damage process in the composite floor during fire were examined. The results show that the AE parameters of a steel？？concrete composite floor during a fire show different characteristics as the temperature along the slab depth changes nonlinearly, and the characteristics are in accordance with the crack stages of the slab. The phenomenon is considered to be caused by the mechanical behaviors of the material and structures. During the tests, the signal of the AE sources at early stage is most active, and it is in accordance with the inflection points in the curve of the ringing count and cumulative count with time and also the progress, distributed area, and intensity of the cracks on the slab surface. The variation of distribution characteristics for AE events in space is an important indicator of structural instability and inner damage, and its intensity (amplitude, energy, etc.) should receive more attention. During the cooling period, a certain amount of movement appeared between the steel beam and concrete slabs because of the difference coefficient of thermal expansion. Accordingly, the AE signal is still active at this stage. For this reason, AE characteristics during the cooling period should be considered sufficiently when a