共查询到19条相似文献，搜索用时 171 毫秒
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开展了5根锈胀开裂钢筋混凝土梁疲劳试验并实时记录了梁表面的钢筋压磁信号,研究锈胀开裂混凝土梁的疲劳特性和压磁信号演化规律。结果表明梁疲劳寿命随钢筋锈蚀率增大而急剧减小,梁破坏时混凝土剥落,纵筋发生疲劳断裂;磁信号时变曲线随疲劳进程不断演化,在临近疲劳破坏时曲线形态发生明显畸变,能够反映梁疲劳损伤信息;磁感应强度变化幅值的发展符合三阶段特性,在疲劳初期和破坏前增长明显;磁感应强度变化幅值对钢筋锈蚀敏感,随锈蚀率增加而增大,因此建立了疲劳作用不同阶段磁信号幅值和梁内钢筋锈蚀率的相关关系。 相似文献
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高桩码头锈蚀破损面板残余承载力评估方法 总被引：6，自引：0，他引：6
高桩码头长期工作在具有腐蚀介质的潮湿环境中，因钢筋的锈蚀会使构件表面砼胀裂而破损，目前我国大部分的高桩码头进入了锈蚀破损的高峰期。通过研究指出：以往国内外用构件蚀破损表面积大小或顺筋裂缝大小的标准来确定维修方案的方法是不正确的。根据一般构件为等截面，而沿跨度分布的弯矩不均匀的事实，指出构件在控制断面以外的部位强度有富裕，允许钢筋适当的锈蚀仍能满足设计强度的新见解。提出了锈蚀破损面板的强度安全性评估准则、强度因子新概念及其具体计算式，可以量化评估犭蚀破损面板的残余承载力，为科学制定锈蚀破损面板的维修方案提供参考，在保证码头结构安全的同时，大大节省维修费用。 相似文献
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氯盐干湿环境下受弯横向裂缝对钢筋混凝土耐久性影响 总被引：1，自引：0，他引：1
为了研究持续开裂状态下横向裂缝对钢筋混凝土结构耐久性的影响特性,开展了8根受弯开裂钢筋混凝土梁构件的盐溶液干湿循环试验;借助无损检测技术和破损实测方法,分别对氯离子侵入量、钢筋半电池电位、腐蚀电流密度以及平均锈蚀率等进行了对比分析。研究结果表明,裂缝的存在将提高混凝土的渗透性,裂缝处及周围混凝土内的氯离子含量明显增大;对于一定裂缝分布状况的钢筋混凝土试验梁,内部钢筋的腐蚀电位、腐蚀电流密度以及平均锈蚀率均高于裂缝自愈及无裂缝的试验梁,并受到保护层厚度与裂缝开展状态的影响,其影响规律可用单位长度内的平均裂缝宽度与保护层厚度的比值wm/c来进行综合评价。综合试验结果,初步建议海洋干湿侵蚀环境下钢筋混凝土构件的最大裂缝宽度wmax宜小于0.003 3 c,相关结论可为海洋混凝土结构的耐久性设计提供参考。 相似文献
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氯化物是钢筋混凝土结构在使用寿命期内可能遇到的一种最危险的侵蚀介质,混凝土中钢筋表面的氯离子浓度超过一定的限值,钢筋就可能会发生锈蚀,锈蚀的钢筋会导致混凝土构件的承载力下降.通过分析国内外研究者所做的大量工作,讨论了氯离子侵入引起的锈蚀钢筋混凝土构件的抗力计算方法,为氯化物环境条件下混凝土结构的耐久性评估提供参考. 相似文献
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为分析海洋混凝土结构在波浪及海流等荷载作用下的疲劳特性,基于试验结果分析,我们建议了一个用弹塑性增量变刚度法分段跟踪疲劳应力-应变关系曲线及应力循环次数与疲劳应变关系曲线相结合的非线性有限元分析法。混凝土的本构模型采用内时损伤模型。该分析方法的特点是利用较少的机时,就可分析得出结构经过任一疲劳次数(包括上百万次)高周疲劳全过程后的应力、应变状态。这在国内外尚属少见,从而为海洋混凝土结构疲劳特性的有限元分析及用分析法部分代替冗长、昂贵的疲劳试验提供了条件。为验证分析方法的可靠性,我们对海洋平台中经常遇到的钢筋混凝土板的疲劳特性进行了分析,所得计算结果与试验结果符合较好,证明了本文所建议方法的可行性。 相似文献
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为分析海洋混凝土结构在波浪及海流等荷载作用下的疲劳特性,基于试验结果分析,我们建议了一个用弹塑性增量变刚度法分段跟踪疲劳应力-应变关系曲线及应力循环次数与疲劳应变关系曲线相结合的非线性有限元分析法.混凝土的本构模型采用内时损伤模型.该分析方法的特点是利用较少的机时,就可分析得出结构经过任一疲劳次数(包括上百万次)高周疲劳全过程后的应力、应变状态.这在国内外尚属少见,从而为海洋混凝土结构疲劳特性的有限元分析及用分析法部分代替冗长、昂贵的疲劳试验提供了条件.为验证分析方法的可靠性,我们对海洋平台中经常遇到的钢筋混凝土板的疲劳特性进行了分析,所得计算结果与试验结果符合较好,证明了本文所建议方法的可行性. 相似文献
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复杂应力状态下混凝土的变形和强度特性 总被引：3，自引：0，他引：3
为解决混凝土平台设计中遇到的复杂应力状态下混凝土的变形和强度特性,本文利用自制的多轴混凝土的变形和强度试验装置,对混凝土在平面应力状态下的变形和强度特性进行了试验研究,并根据试验结果,建立了相应的内时损伤本构模型及破坏准则,编制了相应的计算机程序,并进行了实例分析,其结果与试验值符合较好。 相似文献
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动荷载作用下海底粉土的孔压响应及其动强度 总被引：5，自引：0，他引：5
本文选用近海分布较广的粉土为研究对象 ,利用室内动三轴试验结果 ,找出动荷载作用下粉土的动应力应变关系 ,分析模拟波浪荷载作用下粉土中的孔压响应、临界循环次数 ,确定波浪作用下粉土的应力状态、破坏临界循环次数 ,判断不同深度处的粉土发生液化的可能性及发生液化所需要的时间 ;研究粉土在动荷载作用下的强度降低 ,为海上工程设计和施工提供科学依据。 相似文献
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A novel method for prediction of the load carrying capacity of a corroded reinforced concrete beam (CRCB) is presented in the paper. Nine reinforced concrete beams, which had been working in an aggressive environment for more than 10 years, were tested in the laboratory. Comprehensive tests, including flexural test, strength test for corroded concrete and rusty rebar, and pullout test for bond strength between concrete and rebar, were condueted. The flexural test results of CRCBs reveal that the distribution of surface cracks on the beams shows a fractal behavior. The relationship between the fractal dimensions and mechanical properties of CRCBs is then studied. A prediction model based on artificial neural network (ANN) is established by the use of the fractal dimension as the corrosion index, together with the basic intbrmation of the beam. The validity of the prediction model is demonstrated through the experimental data, and satisfactory resuits are achieved. 相似文献
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含有腐蚀缺陷海底管道极限载荷分析 总被引：8，自引：0，他引：8
利用有限元弹塑性分析方法,对含有腐蚀缺陷的海底管道进行材料非线性和几何非线性分析,探讨了确定管道极限载荷的准则。在此基础上,给出含有腐蚀缺陷的海底管道的极限载荷,研究腐蚀长度、深度和宽度对海底管道极限载荷的影响,提出了含有腐蚀缺陷的受内压的海底管道的极限载荷计算公式,并与试验结果进行了比较,证明该方法是有效的。 相似文献
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针对构件外表面局部区域遭受随机点蚀损伤的圆管截面,考虑点蚀随机特性的影响,建立包含点蚀坑细节的精细有限元模型;在多种腐蚀强度下,研究局部腐蚀的点蚀区分布位置(沿轴向和周向分布位置变化)及其形状(点蚀区长度和宽度独立或联合变化)影响轴压极限强度退化的规律;并比较局部随机点蚀与局部均匀腐蚀引起构件极限强度退化的差异。研究结果表明,尽管局部随机点蚀与最大初始几何缺陷的耦合作用会使极限强度的退化趋于严重,但是总体而言点蚀区分布位置变化对圆管极限强度的退化没有显著的影响。此外,同等腐蚀体积和腐蚀面积下,相比于长窄式局部腐蚀,短宽式局部腐蚀会引起更严重的极限强度退化,在严重腐蚀情形下后者导致的强度退化会高出25.5%;相比于局部均匀腐蚀,局部随机点蚀会导致更剧烈的极限强度退化,其不利影响可高出20.7%。 相似文献
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It is well known that pitting corrosion occurring on surface of hull structural plate will surely result in a significant degradation of the ultimate strength of the hull structural plate. This report aims at development of an assessing formula for ultimate strength of hull plate with pitting corrosion damage under the biaxial in-plane compression loading. The ultimate strength assessment model that is in terms of the corroded volume loss was deduced in theory, and which was then completed through numerical experiment by employing nonlinear finite element analyses for series of corroded plate models. Meanwhile, pitting corrosion in actual ship hull was analyzed and simulated, which ensured that all the assumptions for the finite element model parameters were in accord with the actual hull plate with pitting corrosion damage. Furthermore, the effects of plate slenderness, the linear factors at the plate edges and the ratio between the transverse and the longitudinal in-plane stresses on the ultimate strength reduction related to the corroded volume loss were discussed. The ultimate strength assessment formula being in terms of corroded volume loss developed in this research is expected to be applicable to assess the ultimate strength of the hull structural plate with pitting corrosion damage. 相似文献
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An experimental research was conducted to determine the corrosion and bearing capacity of a reinforced concrete (RC) slab at different ages in a marine environment. Results show that the development of corrosion-induced cracks on a slab in a marine environment can be divided into three stages according to crack morphology at the bottom of the slab. In the first stage, cracks appear. In the second stage, cracks develop from the edges to the middle of the slab. In the third stage, longitudinal and transverse corrosion-induced cracks coexist. The corrosion ratio of reinforcements nonlinearly increases with the age, and the relationship between the corrosion ratio of the reinforcements and the corrosion-induced crack width of the concrete is established. The flexural capacity of the corroded RC slab nonlinearly decreases with the age, and the model for the bearing capacity factor of the corroded RC slab is established. The mid-span deflection of the corroded RC slab that corresponds to the yield of the reinforcements linearly increases with the increase in corrosion ratio. Finally, the mechanisms of corrosion morphology and the degradation of the mechanical properties of an RC slab in a marine environment are discussed on the basis of the basic theories of steel corrosion in concrete and concrete structure design. 相似文献
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In jacket-type offshore structures, corrosion damage affects the structural performance under compressive loading, which is created by the working and design loads of the main system. In this study, the effects of corrosion damage on the compressive structural behavior and strength of steel tubular members were investigated. Artificial corrosion damage was applied to the tubular specimens via mechanical processing and hand drilling to replicate the inclined nature of jacket-type offshore structures. The damage was applied to either half or all of the circumference of the specimens. The compressive failure modes of the artificially corroded tubular members were affected by the corrosion conditions. The compressive strengths were also affected by the level of corrosion. From the results of this study, the residual compressive strengths of corroded tubular steel members can be estimated based on the condition of the damaged sectional areas. 相似文献
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In this work, we focus on assessing the group effect of localized corrosion on the ultimate strength of the marine structural plates and study the load-deformation behaviors of plates of various slenderness and uniaxial compression. Meanwhile, we investigate different corroded patterns from a single circular pit to 25 circular pits distributed over the plate and carry out hundreds of nonlinear finite element simulations by combining the number, depth, distribution of pits with imperfections and slenderness of plate. The distribution of multiple pits causes scattering of stress concentration on the plate, then the plastic section of plate changes with wider distribution of damage simultaneously. The ultimate strength arises when un-loading zone comprised of the yielding strips and holes extends across the plate. It can be concluded that the corroded condition defined as group effect of pits manipulates the deformation state and the loading capacity of plate at the ultimate strength mode that coincides with the proportion of effective loading area and section in the process of post-buckling. To validate the effect of pits group, we perform the numerical experiments of the post-buckling of steel plates containing pits in a row with different orientation. 相似文献