Non-Contact Terahertz Inspection of Water Content in Concrete of Infrastructure Buildings

Concrete is the most widely used for construction materials in the world. Water content of concrete is an important parameter in terms durability of concrete structures. Terahertz (THz) waves, for which concrete is a porous and absorbable material, have been studied in order to establish a new non-contact inspection technology for maintenance of concrete structures. In this study, THz transmittance and reflectance of concrete in drying process were measured with a 60 GHz GUNN diode and absorption coefficient is analyzed for concrete with various water contents. It is shown that quantitative detection below 10% is possible for the water content at surface area of concrete.

Damage and deterioration mechanism and curing technique of concrete structure in main coal cleaning plants

Concrete structures in main coal cleaning plants have been rebuilt and reinforced in the coal mines of the Shanghai Datun Energy Sources Co. Ltd., the first colliery of the Pingdingshan Coal Co. Ltd. and the Sanhejian mine of the Xuzhou Mining Group Co. Ltd. In these projects, the operating environment and reliability of concrete structures in the main plants of the three companies were investigated and the safety of the structures inspected. Qualitative and quantitative analyses were made on the special natural, technological and mechanical environments around the structures. On the basis of these analyses, we discuss the long-term, combined actions of the harsh natural (corrosive gases, liquids and solids) and mechanical environments on concrete structures and further investigated the damage and deteriorating mechanisms and curing techniques of concrete structures in the main coal cleaning plants. Our study can provide a theoretical basis for ensuring the reliability of concrete structures in main coal cleaning plants.

Quality Assessment of Concrete Blocks Exposed in Nature for Eighty Years

The concrete blocks used on a jetty in Shanghai were made in 1909 and 1910. Having been exposed in nature for 80 years, now there are 4600 pieces of blocks left on the jetty. Comprehensive inspections, such as external appearance examination, core-drilling of concrete blocks, ultrasonic detection, nuclear densimeter inspection and in-door and out-door chemical analysis, show that 75% of the blocks are of the rebound number of 21 - 23, and the saturated limit compressive strength and dry limit compressive strength of 10MPa; the carbonized depth of concrete is 1 - 2 mm. Compared with the state of the jetty in 1968, already used for 60 years then, the jetty is expected to serve another 40 years or more after being repaired.

Evaluation of Reinforced Concrete Structures with Views for Rehabilitation

The increasing number of pathological occurrences is found in reinforced concrete structures, so does the demand for inspection and maintenance services in residential communities in the state of Pernambuco, which aim to detect damage to the structure in a timely manner to minimize repair costs, thus applying preventive maintenance in order to guarantee the estimated useful life of the project for the building. However, it is observed that the practice of periodic inspections is not yet part of the culture of a certain segment of the population that does not have economic means and knowledge of the importance of maintenance to ensure the integrity of the structure. It was used in this work an inspection script with use of tests and methodology to quantify damage and to check the state of degradation of two residential buildings with more than 20 years and built near the seafront where environmental aggression is strong. The deterioration found in each of the buildings has been differentiated due to different corrective maintenance performed at every building. The last maintenance, performed in Building A, was performed by corrective hand of unskilled labour guided by the community itself, which has no expertise in the field of civil engineering. In Building B, the situation is similar, compounded by the opinion of some tenants that there is no need for this routine, even the structure being in critical condition, as was confirmed with the application of the methodology employ. There should be a legislation that governs the execution of inspections and maintenance programs in addition to the existing technical standards. The methodologies presented suitable for checking the degree of degradation of the structures and performed tests confirmed the diagnosis obtained by visual inspection and quantification of damage.

Analysis on the mechanism and characteristics of concrete strength testing methods

This paper mainly described five kinds of common detection methods, including the test block method, core drilling method, rebound method, dialing out method and ultrasonic testing method and systematically analyzed the mechanism of all kinds of concrete strength detection methods as well as their advantages and disadvantages, which would provide a guide for construction personnel and research institutions to choose an economical ,accurate and safe detection method.

Bridge Condition Assessment by Visual Inspection-Croatian Experience

Most decisions relating to bridge maintenance are founded on assessments that are based on visual inspections conducted by specially trained engineers,using procedures and aids defined in the management system.Visual inspection is the main tool for bridge condition assessment,and is therefore of crucial significance for planning periodic maintenance activities.Paper shall present the study aimed at harmonizing bridge assessment activities,which was conducted in early 2012 in company Hrvatske ceste-Croatian National Road Authority.Small RC bridges were chosen for this study,since visual inspection is usually only tool utilized for their assessment.Ratings obtained by inspection were analyzed using methods of mathematical statistics.The results point to weaknesses in the current assessment system,while the study itself constitutes a good basis for further improvement of management aids,manuals and procedures for bridge inspection.

Concrete Defects Inspection and 3D Mapping Using City Flyer Quadrotor Robot

The concrete aging problem has gained more attention in recent years as more bridges and tunnels in the United States lack proper maintenance. Though the Federal Highway Administration requires these public concrete structures to be inspected regularly, on-site manual inspection by human operators is time-consuming and labor-intensive. Conventional inspection approaches for concrete inspection, using RGB imagebased thresholding methods, are not able to determine metric information as well as accurate location information for assessed defects for conditions. To address this challenge, we propose a deep neural network(DNN) based concrete inspection system using a quadrotor flying robot(referred to as City Flyer) mounted with an RGB-D camera. The inspection system introduces several novel modules. Firstly, a visual-inertial fusion approach is introduced to perform camera and robot positioning and structure 3 D metric reconstruction. The reconstructed map is used to retrieve the location and metric information of the defects.Secondly, we introduce a DNN model, namely Ada Net, to detect concrete spalling and cracking, with the capability of maintaining robustness under various distances between the camera and concrete surface. In order to train the model, we craft a new dataset, i.e., the concrete structure spalling and cracking(CSSC)dataset, which is released publicly to the research community.Finally, we introduce a 3 D semantic mapping method using the annotated framework to reconstruct the concrete structure for visualization. We performed comparative studies and demonstrated that our Ada Net can achieve 8.41% higher detection accuracy than Res Nets and VGGs. Moreover, we conducted five field tests, of which three are manual hand-held tests and two are drone-based field tests. These results indicate that our system is capable of performing metric field inspection,and can serve as an effective tool for civil engineers.

钢筋混凝土结构移动式精准检测技术开发

无损检测技术是一种在不损害材料及结构服役性能的前提下,对其性质进行评估和测量的检测技术。然而,随着无损检测技术的发展和实践,结构内部的复杂损伤检测缺乏多层次精准性成为该领域的难点和核心问题。该文旨在结合国内外的研究成果,对无损检测技术的发展、分类和挑战进行梳理和分析,并在此基础上,介绍作者研究团队建立的一套由宏观到细观,再到内部的全面精准检测系统研究成果。针对表面宏观识别与细观定量识别,作者团队开发了表观病害视觉检测技术,包括构建的空间基准点自动追踪融合和亚像素级病害分割的全景图像快速拼接及表观病害厘米级定位方法,以及提出的全景图像中0.05 mm~0.2 mm多尺寸微细裂缝同步识别及真伪判别的人工智能算法。针对结构内部损伤识别,作者团队首创了智能变频敲击声波扫描及各类损伤精准识别新原理,发明建立了自适应激励分布移动敲击声波的损伤检测评估理论方法、声波及声纹图像特征人工智能算法及智能装备关键技术。经过实验验证,裂缝检测中宽度为0.05 mm时最大深度可达40 mm,剥离检测中最大深度可达400 mm,最小识别范围为50 mm。

基于组合赋权—集对分析法的混凝土坝巡检综合评价

鉴于模糊性巡视检查记录和指标权重赋值存在主观性的问题制约着水库大坝巡视检查信息综合评价的可靠性,首先针对巡视检查部位和内容,提出了较为全面的巡视检查状况评价体系;然后划分了巡视检查状况等级并设计了各评价指标的评分标准;进而提出采用组合赋权—集对分析法的巡视检查综合评价模型;最后将该综合评价模型应用于某混凝土坝巡视检查状况评价中。结果表明,模型计算得到的巡视检查状况与实际情况基本吻合,表明该评价模型合理、可行。

预制UHPC雨污水检查井的设计与仿真分析

为了解决传统混凝土雨污水检查井易出现病害(如井体开裂)的问题,提出了一种预制超高性能混凝土(UHPC)雨污水检查井。通过结构设计和仿真分析对预制UHPC雨污水检查井的性能进行了评估研究,并对其制作和运输方式进行了介绍。结果表明:UHPC雨污水检查井的性能指标满足相关规范要求,受力性能较好,制作和运输方便,可为后续预制UHPC雨污水检查井的设计与应用提供参考。

Enhanced air-coupled impact echo technique by phase analysis of signals from multiple sensors

This paper presents an air-coupled impact echo(IE)technique that relies on the phase spectrum of the collected data to find the frequencies corresponding to the reflections from delaminations.The proposed technique takes advantage of the fact that the IE compression wave is not a propagating wave,but it is the 1st order symmetrical(S1)mode Lamb wave at zero group velocity(S1-ZGV).Therefore,it searches the phase spectra of the data collected by multiple sensors to locate the frequency corresponding to the lowest phase difference.As a result,the technique reduces the effect of propagating waves,including the direct acoustic wave and ambient noise.It is named the Constant Phase IE(CPIE).The performance of the CPIE is experimentally compared with the regular amplitude spectrum-based IE technique and two other multisensor IE techniques.The CPIE shows a performance advantage,especially in a noisy environment.

混凝土中离散分布的游离氧化钙潜在危害的检测推断

常用于测试游离氧化钙(f-CaO)对混凝土潜在危害的方法包括薄片和芯样试件沸煮测试等,但由于试件体量较小,对离散分布在混凝土中的f-CaO潜在危害测试存在较大偶然性。以某项目实体混凝土墙、板为研究对象,通过沸煮实验,从外观、厚度、超声波声时、抗压强度多方面对实体混凝土中混入过烧石灰对混凝土质量影响进行测试推断。结果表明:采用沸煮前后外观、厚度、超声波声时、抗压强度多方面测试的结果更全面、准确,对相关事故的防控以及质量检测具有一定参考意义。

基于机器视觉的混凝土3D打印几何特征自动提取方法研究

近年来,随着混凝土3D打印技术的不断发展,打印成品的质量受到越来越多的关注。打印成品的几何特征已成为评估打印质量的重要指标。针对当前3D打印混凝土几何特征提取中存在的诸如流程复杂、精度有限及缺乏评价指标等问题,本文设计了基于机器视觉的混凝土3D打印几何特征自动提取方法。首先,采用摄像头阵列部署方法获取打印成品的原始图像,并对原图像正畸以提高图像质量;其次,通过语义分割模型U-Net提取打印成品的几何特征,并对得到的结果进行优化;最后,通过量化的指标值,对其进行了可视化并评价打印结果。实验证明,本文提出的几何特征自动提取方法具有速度快、精度高等显著优势;此外,系统化的打印评价指标可为混凝土3D打印质量评估提供借鉴参考。

预制混凝土剪力墙尺寸偏差检验指标研究

为解决现有预制混凝土剪力墙构件尺寸偏差检验指标体系针对性差、部分指标过严、部分指标缺失等问题,系统梳理了现行标准体系中关于预制混凝土剪力墙构件的尺寸偏差检验指标要求,并在此基础上,结合不同种类预制混凝土剪力墙构件的特点,以及尺寸偏差质量检验指标与主体结构质量的关系,给出了尺寸偏差检验指标建议要求。

游离氧化钙对混凝土构件质量的影响研究

以某建筑工程项目为主要研究对象,对该项目混凝土框架结构实体构件进行检验,判断游离氧化钙对混凝土质量的影响程度,整体分析其芯样抗压强度检验结果。经过试验数据显示,在工程检验过程中要根据实际情况,全面调查混凝土外观质量,确定游离氧化钙对混凝土质量产生的影响;当检验数据和建筑结构检测技术标准差异较小,要综合考虑检验中人为因素影响。同时,如果抽取样本数量较少,很难确定实际结论时,要提高现场取样数量,从而实现平行验证。

基于一次计数抽样检验的现场混凝土强度特征值推定方法

回弹法检测现场混凝土强度具有对结构构件完全无损伤、可抽样数量多、测区布置灵活的优点,但其检测强度的均值和方差均可能存在较大偏差,故采用计量抽样检验方法推定的检测批强度特征值的准确性较差。根据一次计数抽样检验原理,在分析比较抽检特征曲线的基础上,以不合格品率为0.1时的接收概率为50%(置信水平为0.5)为原则,建立了检测批混凝土强度特征值的推定方法。通过抽检特征曲线对比和实例分析表明,该方法的推定结果与基于贝叶斯方法的计量抽样检验推定结果基本相当。提出了评定检测批混凝土强度时回弹测区的优化布置建议,并提出了回弹法计数抽样检验结果的钻芯修正方法。本文建议方法具有概率定义准确、避免强度分布类型假定和方差计算、减少钻芯校核数量等特点,可在工程质量符合性评定和既有结构安全性评定时采用。

某大型钢筋混凝土工程项目质量检测效果分析

现阶段房地产开发市场中存在“烂尾楼”停工复建项目,为对拟复建的建筑物进行全面质量检测,并及时发现钢筋混凝土工程质量问题点,以便在后期施工中予以修复,论文以某广场复建前检测项目为例,论述了项目质量检测过程,综合使用取芯法和回弹法等两种方法对混凝土的抗压强度进行检测,既降低了取芯法对现有建筑物结构体的损坏,又减少了回弹法的理论误差。

Python在混凝土结构实体强度监督抽检中的运用

以2023年上海市建设工程巡查现浇混凝土结构实体强度监督抽检的工作内容与检测数据为切入点,通过计算机Python数据分析工具,应用系统工程方法论并对比传统合格率统计方法,对现浇混凝土结构实体强度监督抽检结果的评价方式进行研究与优化,本研究为建设工程监督管理机构混凝土实体强度检测结果的评价提供了可量化且严谨的参考方法。

堆石混凝土拱坝整体浇筑质量检测分析

为了评价堆石混凝土拱坝整体浇筑质量,结合已建成的5座(其中蓄水4座)整体浇筑堆石混凝土拱坝,从高自密实混凝土配合比、堆石混凝土施工工艺、坝体质量检测及试验、大坝建成后运行情况等方面进行综合分析。结果表明:各项试验指标均满足设计要求,坝体浇筑质量总体较好,同时各工程均未发现裂缝等异常情况,大坝运行正常。堆石混凝土拱坝采用整体浇筑,不仅充分发挥了新型筑坝材料的优势、同时也减少了坝体分缝带来的施工干扰,提升了大坝浇筑速度,验证了整体浇筑施工设计是可行的,可为类似工程提供参考。

某初轧厂均热炉混凝土烟囱可靠性鉴定及数值模拟研究

依托某初轧厂均热炉混凝土烟囱实例,详细介绍了混凝土烟囱检测与可靠性鉴定的方法和程序,并运用有限元分析软件SAP2000,采用分层壳单元建立相应的非线性分析模型,考虑烟囱受P-Δ效应的影响,分析烟囱在风荷载及地震作用下筒壁的应力反应,验算烟囱考虑损伤后的承载能力,验证加固方案的加强效果,为该烟囱后续使用和改造提供建议和技术依据。