Reliable evaluation method of quality control for compressive strength of concrete

INTRODUCTION In recent years, devastating disasters in whichreinforced concrete structures collapsed have causedmajor loss of life and property damage around thworld. Investigation of these incidents showed thathe collapses were mainly due to the poor concretquality (NCREE, 1999; SECL, 1999; Watabe, 1995)Therefore, high quality assurance in reinforced concrete (RC) structure design and manufacturing is onof the most important safety factors. To promote threliability of structure, co…     

Effect of chloride content on bond behavior between FRP and concrete

For reinforced concrete structures located along the seaside, the penetration of chloride ions into concrete may be a threat to the durability of the structures. Experimental investigations were carried out to study the effect of chloride content on the bond behavior between concrete and fiber reinforced polymer (FRP) plates. Direct shear tests were conducted on the FRP strengthened concrete members. Before testing, the specimens were immersed in NaCl solutions with concentrations ranging from 3%—15% for different time (0—120 d). Then, the specimens were dried and tested to obtain the initial and ultimate debonding loads, together with strain distributions along the FRP plates of different load values. The correlations between chloride content and debonding parameters are established. Test results show that the debonding parameters are closely related to the immersing time rather than the chloride content of the solution.     

不同水中氯离子含量的对比分析研究

采用紫外—可见分光光度法和莫尔法对不同水样中氯离子含量进行测定。紫外—可见分光光度法通过加入丙酮做保护剂,在最大吸收波长附近测得不同水样中氯离子的吸光度,测得自来水、湖泊水和饮用水中氯离子的含量分别为19.97mg·L-1,8.02mg·L-1,2.00mg·L-1,相对平均误差均小于1,加标回收率在98.9%-100.8%,说明实验结果比较可靠;莫尔法通过控制溶液的酸度以及指示剂的用量测定氯离子含量,测得自来水、湖泊水和饮用水中氯离子的含量分别为20.41mg·L-1,8.31mg·L-1,2.70mg·L-1,相对平均误差较大,加标回收率在91.4%-101.2%,说明实验结果较可靠,同时也说明采用该实验方法测水中氯离子的准确度较高。从实验数据的准确性和实验的简易程度,紫外—可见分光光度法都优于莫尔法。     

Simultaneous determination of fluoride, chloride, sulfate, phosphate,monofluorophosphate, glycerophosphate, sorbate, and saccharin in gargles by ion chromatography

Simple, reliable and sensitive analytical methods to determine anticariogenic agents, preservatives, and artificial sweeteners contained in commercial gargles are necessary for evaluating their effectiveness, safety, and quality. An ion chromatography (IC) method has been described to analyze simultaneously eight anions including fluoride, chloride, sulfate, phosphate,monofluorophosphate, glycerophosphate (anticariogenic agents), sorbate (a preservative), and saccharin (an artificial sweetener)in gargles. In this IC system, we applied a mobile phased gradient elution with KOH, separation by IonPac AS18 columns, and suppressed conductivity detection. Optimized analytical conditions were further evaluated for accuracy. The relative standard deviations (RSDs) of the inter-day's retention time and peak area of all species were less than 0.938% and 8.731%, respectively,while RSDs of 5-day retention time and peak area were less than 1.265% and 8.934%, respectively. The correlation coefficients for targeted analytes ranged from 0.999 7 to 1.000 0. The spiked recoveries for the anions were 90%～102.5%. We concluded that the method can be applied for comprehensive evaluation of commercial gargles.     

数学试卷质量分析的数理统计方法浅议

本文主要应用数理统计方法,通过探讨试卷的难度、区分度、信度、效度和覆盖度等质量指标分析数学试卷的质量,并用实例来说明对试卷质量分析的方法。     

Fire's effect on chloride ingress related durability of concrete structure

This paper describes the effects of fire on durability of reinforced concrete structures, and points out that fire not only damages the chemical composition and physical structure of concrete by high temperature, but also leads to an additional risk due to the generation of polyvinyl chloride (PVC) combustion gases. A mathematical model is proposed to calculate chloride ingress profiles in fire damaged concrete, so as to explore the service life prediction of the structure. Rapid Chloride Migration (RCM) test was carried out to determine the chloride diffusion coefficients for the application of the mathematical model. Finally, the detected results of a reported case testified to the validity of the mathematical model.     

Fire＇s effect on chloride ingress related durability of concrete structure

This paper describes the effects of fire on durability of reinforced concrete structures, and points out that fire not only damages the chemical composition and physical structure of concrete by high temperature, but also leads to an additional risk due to the generation ofpolyvinyl chloride （PVC） combustion gases. A mathematical model is proposed to calculate chloride ingress profiles in fire damaged concrete, so as to explore the service life prediction of the structure. Rapid Chloride Migration （RCM） test was carried out to determine the chloride diffusion coefficients for the application of the mathematical model. Finally, the detected results of a reported case testified to the validity of the mathematical model.     

基于Debye-Hückel-Onsager理论的混凝土中离子扩散系数的计算

将Debye-Hckel理论和Onsager电导理论用于研究混凝土孔溶液中离子的扩散规律.首先,建立了饱和混凝土中离子扩散系数的计算模型,该模型考虑了离子的种类、孔溶液中离子的浓度、环境温度等因素对离子扩散系数的影响.其次,以孔溶液中氯化钠的浓度变化为例分析了离子氛半径、松弛效应、电泳效应等对孔溶液中氯离子扩散系数的影响规律,发现氯离子的扩散系数随氯化钠溶液浓度的增加而减小,离子氛半径和电泳效应是影响氯离子扩散性能的重要参数.最后,通过RCM法测定了不同水灰比混凝土的氯离子扩散系数,并将模型的计算结果与实测结果进行了对比,以验证模型的合理性,结果表明所建立的模型与实测结果较为符合.     

Science Letters： Simultaneous determination of fluoride, chloride, sulfate, phosphate, monofluorophosphate, glycerophosphate, sorbate, and saccharin in gargles by ion chromatography

Simple, reliable and sensitive analytical methods to determine anticariogenic agents, preservatives, and artificial sweeteners contained in commercial gargles are necessary for evaluating their effectiveness, safety, and quality. An ion chromatography （IC） method has been described to analyze simultaneously eight anions including fluoride, chloride, sulfate, phosphate, monofluorophosphate, glycerophosphate （anticariogenic agents）, sorbate （a preservative）, and saccharin （an artificial sweetener） in gargles. In this IC system, we applied a mobile phased gradient elution with KOH, separation by IonPac AS18 columns, and suppressed conductivity detection. Optimized analytical conditions were further evaluated for accuracy. The relative standard deviations （RSDs） of the inter-day＇s retention time and peak area of all species were less than 0.938% and 8.731%, respectively, while RSDs of 5-day retention time and peak area were less than 1.265% and 8.934%, respectively. The correlation coefficients for targeted analytes ranged from 0.999 7 to 1.000 0. The spiked recoveries for the anions were 90%-102.5%. We concluded that the method can be applied for comprehensive evaluation of commercial gargles.     

基于物元分析的地下水质量综合评判

由于地下水中含有多种离子,若仅通过单项离子来评判水质等级,势必有很大的缺陷。因此,本文采用一种基于物元分析理论的综合评判方法,建立多种指标的评判模型,运用关联函数来进行地下水质量等级的评判。     

Strength and Toughness of Steel Fibre Reinforced Reactive Powder Concrete Under Blast Loading

The blast resistance of structures used in buildings needs to be investigated due to the increased threat of a terrorist attack. The damage done by Composition B or Powergel to steel fibre reinforced reactive powder concrete (SFRPC) panels and ordinary reinforced concrete (RC) panels of equivalent static flexural strength is compared. A 0.5 kg charge was detonated at a distance of 0.1 m from the 1.3 m×1.0 m×0. 1 m (thick) panels, which were simply supported and spaning 1.3m. Dynamic displacement measurements, high-speed video recording and visual examination of the panels for spall and breach were undertaken. The SFRPC panels withstood the bare charge blast better than the reinforced ordinary concrete panels. Neither type of panel was breached using a 0.5 kg charge. The RC panel exhibited more spalling when Composition B was used. Under successive Composition B loading conditions, the RC panel was breached. In comparison the SFRPC panel was not breached. Exposure to fragmenting charge loading conditions confirmed these performance differences between the SFRPC panel and the reinforced ordinary concrete panel.     

高层建筑结构转换层大梁的施工

本文根据现场施工实践,介绍了转换层钢筋混凝土梁的模板支撑、钢筋制作、安装和混凝土浇筑等主要施工技术过程.     

Unified expression for failure of reinforced concrete members in bridge

INTRODUCTION Reinforced concrete elements with box section are commonly used in horizontal subsystems and in vertical support of bridge structures. The horizontal structural members normally have box section and top flange. The vertical supports of the bridge usually have a box section also. To simplify the deduction of such structural member under combined forces, the box sections without top flange are discussed here. Fig.1 shows the typical section types of reinforced concrete members.…     

Chloride content and pH value in the pore solution of concrete under carbonation

Chloride content and the pH value of the pore solution in the neighborhood of steel reinforcement are decisive parameters for initiation and rate of corrosion. The pore solution of cement mortar and hardened cement paste has been expressed from the pore space by high pressure in the investigation. The influence of the water-cement ratio, age, and addition of chloride to the fresh mix on chloride content in the pore solution has been determined by ion chromatography. At the same time the pH value of the pore solution has been determined. The dissolved chloride content decreases with increase in the water-cement ratio. The amount of bound chloride increases with time, but it decreases with decreasing content of dissolved chloride in the pore solution. A significant influence of carbonation on the dissolved chloride content of the pore solution has been observed. With complete carbonation, the dissolved chloride content in cement mortar and hardened cement paste increases by a factor between 2 and 12. The bound chloride decreases by 27%-4%. As expected, the pH value decreases from around 13.2 to as low as 8.0 due to carbonation. It can be concluded that carbonation not only lowers the pH value but liberates bound chloride. This is one obvious reason why the combined action of chloride penetration and carbonation accelerates steel corrosion and shortens the service life of reinforced concrete structures.     

面向OBE的课程目标达成度评价方法——以《工程制图》为例

针对OBE教育模式中课程目标达成度的定量化评价问题,首先阐述OBE定量化评价对教学大纲编写、形成性评价实施、考试题目设计的要求;然后结合实例详细论述课程目标达成度的计算方法。教学实践结果表明,OBE定量化评价方法能根据具体数值给出学生个人、教学班整体各项课程目标的达成度,从而能有效评价学生的学习结果、教师的教学效果,有利于课程教学持续改进。     

Numerical Determination of Shear Strength of Steel Reinforced Concrete Column Strengthened by CFRP Sheets

The earthquake-resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree,In this paper a general system aimed at dealing with the failure analysis of reinforced concrete columns strengthened with carbon-fiber-reinforced plastic(CFRP) sheets including bond-slip of the anchored reinforcing bars at the foot of the columns is presented.It is based on the yield design theory with a mixed modeling of the structue,according to which the concrete material is treated as a classical two-dimensional continuum ,whereas the longitudinal reinfocing bars are regarded as one-dimensional rods including bond-slip at the foot of the columns,In shear reinforced zones both the shear CFRP sheets and transvers reinforcing bars are incorporated in the analysis throuth a homogenization procedure and they are only in tesion ,The approach is then implemented numerically by means of the finite-element formulation,The numerical procedure produces accurate estimates for the loading-carrying capactiy of the shear members taken as an illustrative application by correlation with the experimental results,so the proposed approach is valid.     

财经高校学位授权点评估的困境与出路——基于评估实践的思考

学位评估机制可以说是与学位制度相伴而生的, 是监督保障研究生教育质量的重要举措。选取财经高校作为样本,通过分析财经高校的学科特点及现状,探讨学位评估过程中的现实困境,进而探求学位点评估机制的优化选择,以期为深化研究生教育改革、提升学位授予水平和研究生教育质量提供帮助。     

碳纤维布与钢构套复合加固锈蚀钢筋混凝土柱抗震性能研究(英文)

为改善锈蚀钢筋混凝土柱的抗震性能, 利用碳纤维布与角钢对锈蚀柱进行复合抗震加固. 试验共对12根试件进行了低周反复加载试验, 研究参量包括钢筋锈蚀程度、轴向荷载、碳纤维布层数和角钢用量. 试验结果表明, 利用碳纤维布和角钢复合加固锈蚀柱可以显著改善锈蚀柱的承载能力、延性和耗能能力. 复合加固后, 加固柱的强度和延性与锈蚀柱相比, 可分别提高0.9倍和1倍以上. 基于试验结果, 提出了计算加固构件屈服荷载、最大荷载和位移延性系数的简化公式, 计算结果与试验结果极为吻合.     

Electrochemical study on semiconductive properties of the passive film on rebar in concrete

INTRODUCTION Steel rebar embedded in concrete is protectedagainst corrosion by the thin passive film on its sur-face and the physical protection from concrete. Thealkaline environment (pH≥12.5) of the concrete poresolution triggers passivation on the rebar surface andformation of the protective oxide film. The physicaprotection of concrete coverage hinders the invasionof aggressive agents. However, this passivity can bebroken down by local pH loss as a result of concretecracking or the…     

蔬菜中氧化乐果残留的检测

本文介绍一种检测蔬菜中氧化乐果残留的简便方法。以生菜为样品 ,通过其准确度、灵敏度和精密度分析 ,并与国家标准方法———气相色谱法进行比较和实验学评价 ,结果表明 :该方法对氧化乐果的回收率达 80 %以上 ;最低检测限量为 0 .5mg·kg- 1;多次平行测定变异系数小于 6 % ,其可以满足半定量分析的要求。