钢筋混凝土地层透视雷达无损检测技术

钢筋混凝土的无损检测技术一直是岩土工程界厄需解决的难题。本文将地层透视雷达技术引入到该领域中来 ,从而对混凝土的内部结构与质量作出准确的评价 ,结合工程实例介绍其实际应用效果。     

探地雷达技术在公路隧道衬砌质量检测中的应用研究

对混凝土二次衬砌中的底界厚度、空洞、漏水、钢筋网变形等问题进行检测 ,是公路隧道工程施工中的关键技术。本文通过理论分析和工程试验 ,研究确定了利用探地雷达技术检测所需的有关参数选择方法和测线布置原则 ,同时验证了检测方法的精度和可靠性。研究表明 ,利用探地雷达检测公路隧道衬砌质量具有无损、快速、广泛、精确等优点。     

探地雷达在斜坡震裂变形探测中的应用研究

5.12汶川大地震造成了大量山体震裂变形,形成了众多次生潜在灾害。这类震裂变形的深部特征是控制斜坡稳定性和发展演化规律的关键。本文以探地雷达为主要手段,结合探槽开挖验证对比,选择实例震裂边坡,对震裂变形的深部特征及探地雷达图像显示特点进行了研究。研究结果认为,斜坡震裂变形破坏深度一般不超过2m,裂缝近垂直向下发育,少数微倾坡外,探地雷达反射图像显示为双曲线特征,总体构成封口状"八"字形。研究成果为快速、有效探测震裂裂缝,尤其是垂向裂缝的深部扩展特征提供了有效参考方法,同时也为防灾减灾提供了技术支撑。     

Weighting ensemble least-square method for flutter derivatives of bridge decks

In this paper, a reliable but simple identification method, here called the weighting ensemble least-square method (WELS), has been developed to extract all eight flutter derivatives of bridge deck from free vibration records. For every wind speed, free vibration test of section model is generally repeated several times in order to obtain more reliable parameter estimates. In the WELS method, many free vibration records at the same wind speed are regarded as an ensemble. The common mode parameters are then identified simultaneously from the ensemble data. The parameter fit is obtained by a nonlinear least-square method. Weighting factors are proposed to make each experiment record with the same weight in total residual error analysis. The ensemble composed of many records can reduce the effect of the colored noise of few records on the convergence of least-square iteration process. The flutter derivatives of two section models are identified to indicate the reliability and effectiveness of the WELS method.     

探地雷达在北京市城市道路无损检测中的应用

简要介绍了探地雷达的工作原理及方法,论述了其在城市道路普查和掘路检测中的应用。多年的检测经验表明,探地雷达在城市道路检测中应用效果明显。     

高层建筑石灰岩基底的雷达探测研究

基岩在地下空间的起伏分布是石灰岩地区高层建筑基础设计施工前必须准确了解的关键信息,以马来西亚吉隆坡某拟建高层建筑为例,利用探地雷达对石灰岩基底进行探测试验,并进行数据处理及雷达图像解释分析。雷达探测剖面的解释结果与验证钻孔所揭示的数据基本一致;结果表明,在石灰岩地区,利用该方法可有效地获取石灰岩基底的起伏分布。为基础设计和施工提供依据。     

地质雷达在隧道塌方空腔探测中的应用

基于地质雷达的工作原理,讨论了探测隧道塌方空腔的理论和方法,并阐述了使用地质雷达系统对浙江省某两条高速公路隧道进行塌方空腔探测的情况,最终表明地质雷达法可应用于隧道塌方空腔规模的预估。     

探地雷达无网格法正演模拟研究现状及展望

在无损检测技术高速发展的今天,检测技术不断完善,检测设备不断更新。探地雷达就是无损检测的一种重要工具。对于雷达检测的正演模拟,目前大多集中在有限元模拟,技术相对较成熟,解决了工程中很多问题。但是随着研究的深入,有限元摸拟在解决网格畸变和移动方面十分困难,同时在模拟前处理过程中也稍显复杂。由此,将无网格法引入探地雷达的正演模拟研究中来,解决了网格划分中复杂的问题。     

基于地质雷达法的钢绞线定位模拟分析与应用

通过建立预应力钢绞线模型及高频地质雷达探测效果的模拟分析,从理论上论证地质雷达探测定位钢绞线的可行性;结合厦门市某工程实例的应用效果,论证地质雷达对钢筋钢绞线的探测定位直观、可靠优势。     

Simplified method of analysis accounting for shear-lag effects in composite bridge decks

This paper proposes a simplified method of analysis for the design of twin-girder and single-box steel-concrete composite bridge decks. Its main advantages rely on (i) the use of the real width of the slab for the whole bridge length when performing the global analysis, i.e. without modifying the deck geometry based on the effective width method, and (ii) its ability to evaluate the normal longitudinal stress distribution on the slab by means of a cross-sectional analysis considering the internal actions obtained from the global analysis. In the latter cross-sectional analysis the properties of the concrete component are based on an effective width calculated using new analytical expressions presented in this paper. The proposed approach is capable of handling different loading conditions, such as constant uniformly distributed loads, envelopes of transverse actions due to traffic loads, support settlements and concrete shrinkage. These analytical expressions have been obtained based on the results of an extensive parametric study carried out by means of the finite element formulation described in the first part of the paper. The accuracy of the proposed approach is validated for a typical four-span bridge with constant cross-section throughout its length against the results obtained based on the finite element method. Finally, a realistic case study of a bridge with varying cross-section is considered to show the robustness of the proposed methodology.     

超声法、雷达波法在剪力墙检测中的应用研究

剪力墙结构是承受水平荷载和竖向荷载的主要构件,其混凝土浇筑质量直接关系到整个结构体系的安全。超声法可检测出混凝土中空洞、不密实、裂缝等缺陷,雷达波解译为彩色图可清楚反应混凝土内部状况。文章先分别介绍超声法和雷达波法的工作原理,然后以实际工程案例说明结合两种方法可在剪力墙混凝土质量检测中取得理想的效果。     

探地雷达在岩质隧道施工超前预报中的应用

在隧道施工中,隧道周围及工作面前方的工程地质和水文地质情况与施工的质量和安全关系密切,若充分应用先进的地球物理技术预报隧道前方工程地质情况,就可以有效地避免事故的发生。在广贺高速公路隧道施工期间,为确保隧道施工安全,使用瑞典RMAC探地雷达对隧道掌子面前方地质情况进行了及时准确的预报,并以此为依据进行动态设计,提前采取预防措施,确保了工程安全,达到了较好的预报效果。     

地质雷达超前预报在厦门海底隧道中的应用

首先对地质雷达的基本工作原理和方法进行了分析,然后介绍了需要注意的测线布置和数据采集需进行的参数设置等问题,指出其功能和适用条件,其次对地质雷达探测图像进行了研究、分析,以地质雷达在厦门海底隧道施工中的应用为例,说明地质雷达是短期超前地质预报的一种安全、有效的方法,具有良好的应用前景。     

Method for developing and updating deterioration models for concrete bridge decks using GPR data

This study presents a workable procedure for developing and updating deterioration prediction models based on the results of a Non-Destructive Evaluation (NDE) technique, Ground Penetrating Radar (GPR). To this end, a system reliability based deterioration model was developed for a simply-supported reinforced concrete bridge deck, designed according to the Canadian Highway Bridge Design Code (CHBDC-S6). The superstructure element-level deteriorated conditions for different time intervals were applied in the non-linear finite element model developed for the entire bridge deck, and the system level reliability indices were estimated accordingly. The salt contamination was assumed to affect the top surface, soffits of the deck, and beams due to infusion of de-icing salt material. The resulting primary deterioration model was updated based on a GPR test localized defect map that was obtained for an existing bridge with similar plan dimensions. The results indicate that the assumed conservative uniformly defected superstructure is reliable in this case, that is, the estimated reliability indices for the uniform and localized defect plans do not differ considerably.     

高速公路隧道支护结构的雷达无损探测技术

通过对地质雷达进行衬砌质量无损检测的基本原理和技术流程分析,主要分析了探测过程中技术参数的设置、滤波处理、数据分析和结果评定等详细的实施方法,并通过实际的隧道工程应用对雷达探测技术的有效性进行了检验。结果表明,采用雷达探测技术能有效地检测出隧道初期支护拱背空洞、混凝土厚度不足和型钢间距不达标等常见质量问题。     

探地雷达在油竹山隧道施工超前地质预报中的应用

以贵广高速铁路中的油竹山隧道超前地质预报探测工作为例,将探地雷达预报成果与超前地质钻孔成果进行对比,显示了预报结果的准确性,指出探地雷达作为一种快速高效、高分辨率的无损探测技术,在隧道超前地质预报中得到了广泛应用。     

基于探地雷达技术的道路检测探究及应用

结合采用探地雷达技术进行道路检测的工程实例,分析了探地雷达技术的具体工作原理,阐述了道路路面下方土体密实性及路面面层厚度检测中的测线布置原则,同时通过对探地雷达检测结果进行对比分析形象客观地说明了道路的现状,为今后类似工程检测提供了参考及借鉴。     

探地雷达测试技术及其在岩土工程中的应用

综述了探地雷达测试技术的研究概况,介绍了探地雷达技术的基本理论和测试方法,讨论了探地雷达测试技术在岩土工程领域中的实际应用情况和使用效果,以期探地雷达技术在各类岩土工程中更加广泛地应用.     

新型钢-UHPC组合桥面板抗弯承载力模型试验与理论分析方法

为综合解决正交异性钢桥面板疲劳开裂和桥面铺装易损两大难题,提出一种由波形顶板、超高性能混凝土(ultra-high-performance concrete,UHPC)结构层和改进螺旋线(modified clothoide,MCL)形组合销所构成的新型波形顶板-UHPC组合桥面结构.设计2类共12个足尺模型,对所提出...     

Shrinkage and cracking studies of high performance concrete for bridge decks

Restrained shrinkage cracking is a critical issue that raises the concern of widespread use of high-performance concrete (HPC) in bridge deck. Present studies were undertaken to compare the different HPC and propose concept to use local field data to define a threshold for cracking potential. We developed 18 HPC mixtures, suitable for bridge decks in shrinkage-prone locations, using supplementary cementitious materials - fly ash, slag, silica fume, and metakaolin; and local aggregates with three different w/cm: 0.40, 0.35, and 0.30. Basic properties as well as shrinkage and cracking properties were evaluated. In addition to comparing among HPC performance, a correlation was made between commonly measured parameters such as strength, shrinkage, and modulus of elasticity with cracking onset obtained from ring tests. Finally, field data from no-crack and well performing bridges were used to define a threshold safe limit. This concept can be used for design of HPC mixtures to reduce cracking potential from materials point of view for any other locations.