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谈对混凝土裂缝的处理 总被引：2，自引：0，他引：2
工程结构出现裂缝是比较普遍的现象;而结构裂缝大部分是能够通过设计阶段、施工措施来避免的,本文对构件裂缝的成因、预防及处理进行了详细探讨。 相似文献
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本文谈了两类沥青路面裂缝维修方法。常用维修方法有:灌油维修法;乳化沥青稀浆封层;沥青混合料罩面法。现场再生维修法有:裂缝处的再生;大面积裂缝油面的再生。 相似文献
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本文对民用建筑物裂缝的产生及其发展进行了科学的分析，讨论了变形变化与荷载变化对建筑裂缝产生的影响，并着重讨论了变形变化对建筑物裂缝产生的影响，指出了各部位裂缝产生的原因及其特征，并从设计、施工及管理维修的不同角度提出了预防和处理裂缝的方法。 相似文献
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混凝土裂缝自动愈合机理研究 总被引：4，自引：0，他引：4
通过对混凝土裂缝渗水量影响因素的研究,确定了单位渗水量与裂缝宽度等的关系曲线,以及混凝土裂缝可能产生自愈合的时间及裂缝宽度;还对混凝土裂缝自愈合机理进行了研究。 相似文献
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Successive temperature distribution images around the notch tips during fracture toughness testing of paper were obtained by means of an infrared thermography system. Analysis of the images gave the critical times when the temperature significantly rose at the notch tip and when the distance between two maximum temperature spots started to decrease during the testing. Other successive microscopic images around the notch tips showed the relation between crack opening and displacement and the transitional point of the relation. The onset of stable or unstable crack growth as indicated in these critical times and the point agree with each other. For the specimen with a small width, an unstable crack starts to grow at the maximum load point without the stable crack growth period. On the other hand, a stable crack grows before the maximum load point unless the specimen width is small.The period of the stable crack growth increases with an increase in width. Differing from the methods based on thermal images to determine the onset of crack growth, the microscopic method is applicable at a wide range of strain rates and is thus suitable for quasistatic fracture toughness testing.This work was presented in part at the 8th annual meeting of the Society of Packaging Science and Technology, Japan, Tokyo, June 1999 相似文献
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We examined the applicability of end-notched flexure (ENF) tests for measuring the mode II fracture toughness of wood. Western hemlock (Tsuga heterophylla Sarg.) was used for the specimens. The fracture toughness at the beginning of crack propagationG
IIc and that during crack propagationG
IIR were calculated from the loadloading point compliance and load-crack shear displacement (CSD) relations. The obtained results were compared with each other, and the validity of measurement methods were examined. The results are summarized as follows: (1) The value ofG
IIc increased with the increase in initial crack length. When measuringG
IIc by ENF tests, we should be aware of the dependence ofG
IIc on the initial crack length. (2) The value ofG
IIR initially increased with the crack length, and it reached a constant value. (3) Measurement of the CSD is recommended when obtainingG
IIR because the crack length, which has a great influence on theG
IIR calculation, is implicitly included in the CSD. (4) We found that the crack length during its propagation should be evaluated by the final crack length. 相似文献
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The effects of the location of the crack tip in an annual ring and the direction of crack propagation on the fracture toughness of the TR crack propagation system of coniferous wood (T, direction normal to the notch plane; R, propagation direction) were analyzed by the finite element method in regard of the changes in elastic modulus and strength within an annual ring. The critical point of the fracture was defined as the state where the stress of a square element (0.125 × 0.125 mm) in contact with the crack tip equals the tensile strength. The distribution of specific gravity was measured by soft X-ray densitometry. The elastic moduli in the T and R directions were estimated by the sound velocity. The tensile strengths in the T and R directions were measured by the tensile test using small specimens of l mm span length. Regarding the variability of fracture toughness (K
IC), the experimental and calculated results had the same tendency. Therefore, it was concluded that the variability ofK
IC is caused by the (1) heterogeneity of the elastic modulus and strength within an annual ring; and (2) changes in the degree of stress concentration at the crack tips, according to the direction of crack propagation.Part of this work was presented at the 40th annual meeting of the Japan Wood Research Society, Tsukuba, April 1990 and at the 6th International Conference on Mechanical Behavior of Materials, Kyoto, July 1991 相似文献
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混凝土内出现的裂缝按深度的不同,分为贯穿裂缝、深层裂缝及表面裂缝三种。为了保证出现最少的裂缝,就必须在混凝土施工时掌握它的基本性能,并根据实际应用情况采取有效措施,以确保施工质量。 相似文献
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The paper deals with the experimental characterisation of damage evolution within the radial (R)–tangential (T) growth plane of softwood loaded in tension perpendicular to the grain. The reported investigations comprise in-situ monitoring of crack propagation by means of Confocal Laser Scanning Microscopy (CLSM) and evaluations of crack patterns of broken specimens. Three types of notched specimens, representing different crack propagation systems, were tested; for all configurations, both, loading and crack propagation direction were located within the RT plane of wood. The CLSM pictures of broken specimens show distinct differences among the regarded configurations with respect to crack paths. Two different damage mechanisms were identified being rupture of earlywood cell walls in the case of crack propagation in tangential direction and debonding of wood fibers, i.e. rupture of the interface zone between adjacent tracheids, in case of crack progression in radial direction. In the case of an intermediate crack system with an angle of 45° between initial notch direction and radial direction the crack evolution was monitored in-situ during the tension test, whereby the combined action of both basic fracture mechanisms was observed. 相似文献
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本文对现浇混凝土楼板产生裂缝的各种原因进行了分析,并论述了产生裂缝所带来的各种危害;同时提出了一些相应的控制措施,以防止现浇板产生裂缝,保证工程质量。 相似文献
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In this paper, an experimental analysis of the fracture parameters via the invariant J-integral for a cracked specimen made of wood is presented. The experimental test is realized using a sample made of Douglas fir loaded in opening mode. The sample geometry is a mix between the single edge notch and wedge splitting specimens, and the crack advances in the radial-longitudinal system, parallel to the wood rings. By using the optical mark tracking method, the displacement field evolution close to the crack tip is recorded during the test. The stress and strain fields are calculated using a finite element model generated from the experimental displacement fields. Further, the energy release rate is evaluated for different circular paths or crowns defined around the crack tip and for different loading values. 相似文献