【作者】 陈飞；

【导师】 东兆星； 刘书奎；

【作者基本信息】 中国矿业大学 ， 桥梁与隧道工程， 2020， 硕士

【摘要】 随着我国整个交通行业的不断发展,桥梁工程的建设力度也随之增强。但是在桥梁结构整个寿命周期内,由于存在设计缺陷、施工质量不达标以及成桥后荷载作用和结构自身老化等,桥梁结构都不可避免地产生不同程度的损伤和缺陷。桥面板作为直接承受车轮压力的承重结构,在车辆荷载以及环境侵蚀等作用下,更容易遭到破坏。因此对桥面板进行快速准确的检测,可有效降低桥梁维护成本,提高桥面结构的耐久性和可靠性,保障桥梁正常运营。由于目前桥面多设有沥青铺装层,因此本文在传统单层混凝土板冲击回波响应特性的基础上,开展基于冲击回波的沥青铺装层桥面板内部损伤快速检测的理论研究。通过理论分析、数值模拟、检测方法改进等对材料属性、缺陷深度、激励位置等进行了较为全面的分析。针对沥青——混凝土双层板,结合冲击回波响应特性以及表面波频散特性,在沥青表面和混凝土底面分别施加激励,综合识别沥青——混凝土内部缺陷。研究发现:(1)在双层混凝土板中,冲击回波可以识别不同混凝土层中缺陷;(2)在沥青——混凝土双层板中,由于沥青和混凝土的波阻抗差异较大,冲击回波只能识别单层板的缺陷,即在沥青层表面施加激励,冲击回波只能识别沥青层缺陷,无法识别混凝土层缺陷;而在混凝土层底面施加激励,冲击回波只能识别混凝土层缺陷;(3)对于浅层缺陷(深度<7cm),冲击回波频率很高,衰减很快,其在频谱图中不占主导,容易被低频信号掩盖,此时利用冲击回波无法识别浅层缺陷。因此,在沥青层表面施加激励,冲击回波只能识别深度≥7cm的沥青层缺陷。同样地,在混凝土层底面施加激励,冲击回波也只能识别深度≥7cm的混凝土层缺陷;(4)同时施加双激励可以加快单激励的检测速度,两个激励的布置距离会影响检测结果的准确性;(5)基于表面波的频散特性,当沥青层厚度在20mm～50mm之间时,表面波频散曲线“拐点”对应波长与沥青层厚度比值约为0.8。本论文有图77幅,表34张,参考文献100篇更多还原

【Abstract】 With the continuous development of the entire transportation industry in China,the construction of bridge projects has also increased.However,during the entire life cycle of the bridge structure,due to design defects,substandard construction quality,load effect after the completion of the bridge and the aging of the structure itself,the bridge structure will inevitably produce different degrees of damage and defects.As a load-bearing structure that directly bears the pressure of the wheels,the bridge deck is more likely to be damaged under the load of the vehicle and environmental erosion.Therefore,quick and accurate inspection of the bridge deck can effectively reduce the maintenance cost of the bridge,improve the durability and reliability of the deck structure,and ensure the normal operation of the bridge.Because there are many asphalt pavement layers on the bridge deck,this paper conducts a theoretical study on the rapid detection of the internal damage of the asphalt pavement deck based on the impact echo based on the impact response characteristics of the traditional single-layer concrete slabs.Through theoretical analysis,numerical simulation,improvement of detection methods,etc.,a more comprehensive analysis of material properties,defect depth,excitation position,etc.was carried out.For the asphalt-concrete double-layer slab,combined with the impact echo response characteristics and surface wave dispersion characteristics,the asphalt surface and the concrete bottom are separately stimulated to comprehensively identify the internal defects of the asphalt-concrete.The study found:(1)In double-layer concrete slabs,impact echoes can identify defects in different concrete layers;(2)In the asphalt-concrete double-layer board,due to the large difference in wave impedance between asphalt and concrete,the impact echo can only identify the defects of the single-layer board,that is,the excitation is applied on the surface of the asphalt layer,and the impact echo can only identify the asphalt Layer defects,can not identify the defects of the concrete layer;and when the excitation is applied on the bottom of the concrete layer,the impact echo can only identify the defects of the concrete layer;(3)For shallow defects(depth <7cm),the impact echo frequency is very high,and the attenuation is fast.It is not dominant in the spectrum chart and is easily covered by low-frequency signals.At this time,the shallow echo cannot be used to identify shallow defects.Therefore,when the excitation is applied on the surface of the asphalt layer,the impact echo can only identify the defects of the asphalt layer with a depth ≥ 7 cm.Similarly,when the excitation is applied on the bottom of the concrete layer,the impact echo can only identify the defects of the concrete layer with a depth of ≥7cm;(4)Simultaneous application of double excitation can accelerate the detection speed of single excitation,the arrangement distance of the two excitations will affect the accuracy of the detection results;(5)Based on the dispersion characteristics of the surface wave,when the thickness of the asphalt layer is between 20 mm and 50 mm,the ratio of the wavelength of the "inflection point" of the surface wave dispersion curve to the thickness of the asphalt layer is about 0.8This thesis has 77 pictures,34 tables,and 100 references.更多还原