Seismic resilience of concrete structures under corrosion

A probabilistic approach to lifetime assessment of seismic resilience of deteriorating concrete structures is presented. The effects of environmental damage on the seismic performance are evaluated by means of a methodology for lifetime assessment of concrete structures in aggressive environment under uncertainty. The time‐variant seismic capacity associated with different limit states, from damage limitation up to collapse, is assumed as functionality indicator. The role of the deterioration process on seismic resilience is then investigated over the structural lifetime by evaluating the post‐event residual functionality and recovery of the deteriorating system as a function of the time of occurrence of the seismic event. The proposed approach is applied to a three‐story concrete frame building and a four‐span continuous concrete bridge under corrosion. The results show the combined effects of structural deterioration and seismic damage on the time‐variant system functionality and resilience and indicate the importance of a multi‐hazard life‐cycle‐oriented approach to seismic design of resilient structure and infrastructure systems. Copyright © 2015 John Wiley & Sons, Ltd.     

海洋微生物在船舶用结构钢表面附着成膜过程及其腐蚀研究

通过紫外分光光度计测定了海洋微生物需钠弧菌 Vibrio natriegens 的生长曲线,通过扫描电镜和原子力显微镜观测了该细菌在船舶用结构钢(DH32)钢样表面成膜过程及试样腐蚀形貌,探讨了生物膜的形成过程及其对材料表面腐蚀的影响。结果表明,生物膜的形成过程与微生物生命活动关系密切。根据对比暴露在菌液和无菌培养基中的试样表面形貌,发现细菌的附着及成膜过程的不均匀性,改变了DH32钢样表面的物理和化学状态。细菌附着区与周围形成的氧浓差电池,以及细菌新陈代谢主要产物对金属离子的络合,共同促进了试样局部腐蚀加速。     

温度与侵蚀对沥青混凝土冻融疲劳寿命的影响

为了提高盐渍土地区沥青路面的疲劳性能, 对SBS改性沥青混凝土进行了清水与饱和氯盐溶液的冻融劈裂疲劳试验, 研究了温度与氯盐侵蚀共同作用下, 沥青混凝土冻融疲劳寿命衰减规律. 结果表明: 温度与氯盐侵蚀是影响沥青混凝土冻融疲劳寿命的重要因素. 当冻融次数相同时, 沥青混凝土冻融疲劳寿命随冻融温度降低而不断减小; 当冻融温度相同时, 其冻融疲劳寿命随冻融次数增加而不断减小. 饱和氯盐溶液中沥青混凝土冻融疲劳寿命明显低于清水条件, 说明氯盐能够加速沥青混凝土冻融疲劳寿命衰减, 冻融温度越低, 盐冻破坏越严重. 通过对试验数据回归分析可知, 沥青混凝土冻融疲劳寿命与冻融循环次数之间具有较好的相关性, 可以利用两者之间的指数函数关系来预测沥青混凝土冻融疲劳寿命.     

南日岛海域海上自立型测风塔设计施工技术探讨

为获得南日岛海域的风能资源数据,在该海域设计建造了一座自立型测风塔。在测风塔的基础设计、施工过程中,分析计算了海上特殊施工环境中的基础受力、设计参数及荷载组合,因地制宜地采用多种基础施工工艺、防腐处理等技术;在塔体安装时采用了整体吊装技术,并设计了引导装置保证了塔体准确就位。该工程可为海上风电场开发及类似海上工程提供参考。     

某水库库区侏罗系钙质砾岩对水库渗漏的影响

某拟建水库地层中存在溶孔和溶洞等溶蚀现象,可构成潜在渗漏通道。在对水库库区地质、水文地质条件调查、分析基础上,重点研究了库区钙质砾岩溶蚀的发育机理、特点和空间发育规律。由此,初步认为：库区钙质砾岩条带溶蚀不甚发育,不存在贯通性的渗漏通道,不会引起水库严重渗漏。     

化学侵蚀下硬脆性灰岩变形和强度特性的试验研究

 通过硬脆性灰岩在不同pH值、0.1 mol/L和Na2SO4和CaCl2溶液以及蒸馏水浸泡后的的常规三轴压缩试验,分析了受化学腐蚀作用的灰岩在不同围压下的变形及强度特性,探讨了三轴强度参数及变形参数的变化规律,并对浸泡岩石的化学溶液进行水质检测,得到了化学溶液中各离子浓度的变化规律,初步分析了化学溶液对灰岩力学特性影响的机制和规律。试验表明：化学溶液浸泡后,灰岩有从脆性向延性转化的趋势;灰岩的强度参数 , 值及弹性模量E均有不同程度的下降,而泊松比则增大;在相同的化学溶液侵蚀下,弹性模量和凝聚力降低幅度最大;灰岩力学参数劣化的程度与从灰岩中溶出的离子浓度的大小具有一定的对应关系：从灰岩中溶出的离子浓度越高,其力学参数劣化程度越大。     

考虑水化学损伤的砂岩流变损伤本构模型

通过对已有的水化学溶液腐蚀作用后红砂岩三轴蠕变试验结果的分析,可知水化学作用能够加快岩石损伤的发展,增强红砂岩的蠕变效应。根据水岩化学作用的动力学理论,将红砂岩中可溶解胶结物的流失作为水化学腐蚀作用下岩石力学性能劣化的根本原因。通过化学反应速率方程和测定浸泡过程中溶液pH值的变化,定义了考虑初始pH值和时间的化学损伤因子。考虑流变过程中的应力损伤,基于广义Kelvin模型,提出了考虑水化学作用的砂岩流变损伤本构模型。通过对水化学作用下红砂岩流变试验结果进行模拟,对该模型进行了参数辨识和验证。结果表明,所提出的模型能够较好地反映水化学作用下砂岩的流变特性,具有有效性和合理性。     

Preparation and Properties of Embeddable Ag/AgCl Gelling Reference Electrode for Rebars Corrosion Monitoring in Concrete

Reference electrodes are a key part for corrosion monitoring and measurement of rebars in concrete. A reference electrode that can be buried in concrete is fabricated by using Ag/AgCl electrode and methyl cellulose gelling electrolyte. The stability, repeatability and anti-polarization of the reference electrode are investigated; the influences of the inner electrolyte loss, exterior OH? contamination, and temperature on the potential of the reference electrode are also investigated in this paper. The results show that the reference electrode has good stability, repeatability, and anti- polarization. The influences of inner electrolyte loss, exterior OH? contamination, and temperature on the potential of the reference electrode are minimal. Therefore, it can be used for corrosion monitoring and measurement of rebars in concrete.     

ELECTROCHEMICAL STUDIES ON THE CATHODIC REACTION OF MARINE ATMOSPHERIC CORROSION

Electrochemical studies on the cathodic reaction of marine atmospheric corrosion using Kelvin probeas reference electrode showed that the rate of cathodic reaction-oxygen reduction first increases then de-creases, with the reaction maximizing at a certain thickness as the electrolyte film decreases duringevaporation. It was indicated that with decreasing electrolyte thickness by drying, the oxygen reduction ratewas accelerated by the faster oxygen diffusion due to the thinner electrolyte layer on the metal surface. Theresults also revealed that although the oxygen salting out effect has great influence on the rate of oxygenreduction, it is not the main causative factor for the decrease in cathodic limiting current in the case of avery thin electrolyte layer.