现有建筑物结构抗力退化计算

针对钢筋混凝土结构，在假定结构抗力退化为阶跃式模式下，从结构构件材料截面减小和材料性能退化两方面分析计算结构抗力退化，给出了以现有建筑物钢筋混凝土结构构件的混凝土截面、钢筋截面、钢筋强度、钢筋与混凝土共同作用个指档的抗力退化简化计算公式。     

如此载货让人忧!

5月15日下午，大田交警在省道306线查获一部违法装载的农用车，车上所载钢筋一字排开，仅靠一根细小的铁线固定，加之钢筋又长又重，导致其严重弯垂车前，挡住车辆视线，像一扇未挂起的窗帘。     

碳纤维布加固技术在结构安全隐患工程的应用

安全隐患的工程概况 某制药厂提取车间建于1984年，由于建成时间较久，结构老化，无论抗震能力还是承载能力已不能满足安全使用要求。因长期受腐蚀性气体的侵蚀，三根薄腹梁下弦混凝土与钢筋均遭受严重腐蚀，导致保护层混凝土开裂、酥松、剥落，造成混凝土梁有效截面减少，使结构构件断面刚性降低、挠度增加，久之混凝土作用会失效，存在一定的工程安全隐患。另外由于下弦钢筋锈蚀、剥落，钢筋受力截面削弱，     

植筋锚固技术在ESP扩建改造工程中的应用

通过工程实例，介绍植筋锚固技术在建筑结构改造加固中的运用。     

C50混凝土环氧涂层钢筋粘结滑移性能与强度计算研究

对环氧涂层钢筋C50混凝土试件进行轴心拉拔试验,分析钢筋直径（12 mm、14 mm）以及粘结长度（5d、8d、12d）对试件粘结性能的影响。试验结果表明：环氧涂层钢筋C50混凝土试件有钢筋拔出破坏和混凝土劈裂破坏2种破坏形式;试件粘结-滑移曲线的发展趋势受试件钢筋直径与钢筋粘结长度的影响;增大钢筋直径可以提高21.4%～86.1%的粘结力,但会使极限粘结应力先增大后减小;增大钢筋粘结长度可以提高115.0%～147.5%的粘结力,但会明显降低粘结长度较大试件的粘结强度。最后,根据试验结果提出适用于环氧涂层钢筋C50混凝土的极限粘结强度计算公式,为其工程应用提供一定参考。     

混凝土中钢筋锈蚀的研究

钢筋腐蚀对混凝土耐久性和安全性有很大影响。笔者阐述了研究钢筋锈蚀的原因、目的和意义;研究了钢筋在未开裂和裂缝状态下的锈蚀机理,钢筋的腐蚀过程实质上是一个电化学反应过程;影响钢筋锈蚀的主要因素有混凝土的密实度、混凝土碳化、环境湿度、氯离子侵入等;对钢筋腐蚀过程中的4个阶段进行了研究;从锈后钢筋截面面积损失率对结构受力的影响进行讨论;从正常使用寿命和承载能力使用寿命两方面对在役混凝土结构剩余寿命进行预测;并提出了钢筋锈蚀应采取的预防措施,以提高结构的耐久性和安全性,减少耐久性破坏造成的损失。研究的成果在工程上具有一定的理论意义和实用价值。     

钢筋套筒灌浆接头抗拉性能影响因素试验研究

通过对54根钢筋半套筒灌浆接头进行单向拉伸试验,分析灌浆料强度、钢筋锚固长度及钢筋直径对套筒灌浆接头抗拉性能的影响。在此基础上,寻找满足安全使用条件下抗拉性能最弱的接头试件,分析早期振动荷载中振幅和频率变化对接头试件抗拉性能的影响。结果表明:同一钢筋直径灌浆接头试件,抗拉性能随灌浆料强度和钢筋锚固长度的提高而增强;钢筋直径越大,接头抗拉性能越强;早期振动荷载中振幅的增大对试件极限承载力及钢筋与灌浆料之间的锚固性能产生不利影响;频率的变化对试件抗拉性能影响很小;由振动荷载引起的钢筋偏心情况对接头抗拉性能影响微弱。     

工业建筑可靠性检测鉴定技术讲座(十一)

1 检测目的 混凝土中的钢筋通常由于混凝土的碱性保护而免遭腐蚀。但由于碳化作用,空气中酸性气体(CO_2、SO_2等)的侵入,腐蚀性介质的侵蚀和混凝土中氯化钙的侵蚀等,会造成钢筋锈蚀。钢筋锈蚀使钢筋有效截面减小,并降低钢筋与混凝土之间的粘结力,从而减弱钢筋混凝土构件的承载能力和耐久性。对于旧工业建筑物,检测钢筋混凝土结构构件中钢筋的锈蚀程度,是查找安全隐患,鉴定其可靠性和耐久性的重要指标之一。 2 检测范围 当存在以下情况之一时,应检测钢筋的锈蚀程度: (1)当混凝土保护层已完全碳化时。 (2)当混凝土构件出现沿钢筋方向的纵向裂纹时。 (3)当环境中存在腐蚀性介质并侵入到混凝土构件中,或者施工时混凝土中掺入了氯盐时。     

锅炉用麻石水膜式除尘器的几项改进措施

目前，我国锅炉使用的水膜式除尘器，从结构上来看，已有原砌砖结构、水泥钢筋结构、钢制圆筒结构基本都被麻石结构代替。     

都是超载惹的祸……

4月26日18时许，福建省武平县城马头山公园附近一辆运钢筋的农用车超重发生仰翻。     

Evaluation of a responsible beverage service and enforcement program: Effects on bar patron intoxication and potential impaired driving by young adults

Objective: Studies of alcohol-related harm (violence, injury, illness) suggest that the most significant risk factors are the amount of alcohol consumed and whether obviously intoxicated patrons continue to be served. This study's objective was to investigate the effects of a responsible beverage service (RBS)/enhanced alcohol enforcement intervention on bars, bar patrons, and impaired driving.

Method: Two communities—Monroe County, New York, and Cleveland, Ohio—participated in a demonstration program and evaluation. The intervention applied RBS training, targeted enforcement, and corrective actions by law enforcement to a random sample of 10 identified problem bars in each community compared to 10 matched nonintervention problem bars. Data were collected over 3 waves on bar serving practices, bar patron intoxication, drinking and driving, and other alcohol-related harm from intervention and control bars and treatment and comparison communities.

Results: In Monroe County, New York, of the 14 outcome measures analyzed, 7 measures showed statistically significant differences from pre- to postintervention. Six of those measures indicated changes in the desired or positive direction and 2 measures were in the undesired or negative direction. Of note in the positive direction, the percentage of intervention bar patrons who were intoxicated decreased from 44 to 27% and the average blood alcohol concentration of patrons decreased from 0.097 to 0.059 g/dL pre- to postintervention. In Cleveland, Ohio, 6 of the 14 measures showed statistically significant changes pre- to postintervention with 6 in the positive direction and 4 in the negative direction. Of note, the percentage of pseudo-intoxicated patrons denied service in intervention bars increased from 6 to 29%.

Conclusions: Of the 14 outcome measures that were analyzed in each community, most indicated positive changes associated with the intervention, but others showed negative associations. About half of the measures showed no significance, the sample sizes were too small, or the data were unavailable. Therefore, at best, the results of these demonstration programs were mixed. There were, however, some positive indications from the intervention. It appears that when bar managers and owners are aware of the program and its enforcement and when servers are properly trained in RBS, fewer patrons may become intoxicated and greater efforts may be made to deny service to obviously intoxicated patrons. Given that about half of arrested impaired drivers had their last drink at a licensed establishment, widespread implementation of this strategy has the potential to help reduce impaired driving.     

Biomechanical Assessment of Three Rebar Tying Techniques

The National Institute for Occupational Safety and Health (NIOSH) conducted a study of ironworkers to evaluate their risk for developing back and hand injuries from hand-tying reinforcing steel bar and to investigate whether power tying tools can be an effective intervention for the prevention of work-related musculoskeletal disorders. A field investigation of biomechanical loading when using 3 techniques to tie together rebar was conducted. Researchers measured employees ‘ wrist and forearm movement with goniometers and videotaped and analyzed trunk postures. Manually tying rebar at ground level involved sustained deep trunk bending and rapid, repetitive, and forceful hand-wrist and forearm movements. Using a power tier significantly reduced the hand-wrist and forearm movements and allowed the ironworkers to use one free hand to support their trunk posture while tying. Adding an extension handle to the power tier allowed the ironworkers to tie rebar while standing erect, minimizing sustained trunk flexion.     

热应力对混凝土结构的影响及其处理方法

对广钢轧钢厂厂房环境及结构不同区段、不同部位的温度情况,对结构损坏现状及混凝土的强度和碳化情况进行了检测鉴定,并对其缺陷进行了分析,提出了加固处理方法.     

对水工构筑物设计的几点看法

探讨了水工构筑物设计中的地下水位确定、伸缩缝设置、总体布置及设计与施工配合等问题。设计在满足国家有关政策、规范要求的同时,要做到技术先进、安全适用、经济合理。     

Combustion characteristics of pure aluminum and aluminum alloys powders

In this work, the explosion and combustion characteristics of aluminum and some aluminum alloys AlSi7Mg0.6, AlSi10Mg, AlMg5 under powders conditioning were studied. The idea was to compare the combustion of pure aluminum and aluminum alloys. The Minimum Ignition Energy (MIE) and explosion severity ΔP_max and (dP/dt)_max which represents the dust explosion parameters were measured for all powders using Hartman tube and 20 L spherical bomb. The particles temperature and flame temperature were determined by using IR pyrometer and spectroscopy respectively. The results showed that pure aluminum was more sensitive and severe than its alloys. MIE were: 4 mJ for pure aluminum, 13–23 mJ for aluminum alloys. For severity parameters, the overpressure ΔP_max were around 7–8 bars with maximum rate of pressure rise at 1170 bar/s for aluminum and 5–7 bars with 250–360 bar/s for alloys. However, it has been observed that flame temperatures were similar for aluminum and alloys and vary around 2800–3300 K as a function of concentration.     

Experimental and computational fluid dynamic (CFD) simulation of leak shapes and sizes for gas pipeline

In this paper, a parametric study has been carried out to predict the exit velocity of air through the leakage in the pipe with the help of CFD software ANSYS Fluent. The effect of air pressure in the pipe and the shape of leakage have been studied. Further experiments were also carried out to determine the exit velocity for the defined shape of leakage by varying the air pressure in the pipe. Experimentally, the velocity at a distance of 8 cm from the location of a leak in the horizontal plane was obtained with the help of differential pressure transducers. Using the experimental results, the computational results were validated. The results of the parametric simulation study showed that even for a pressure of 2 bars the velocity profile at the leak location indicates the supersonic state where the Mach number is greater than 1. The study is useful because it may be used as a foundation for risk assessment and safety management in the case of flammable gas leaks through gas pipes.     

Application of CFD on the sensitivity analyses of some parameters of the modified Hartmann tube

The aim of this work is to determine the influence of operating parameters such as the dispersion pressure, the ignition delay and height on the dust flammability. A Computational Fluid Dynamics (CFD) simulation, based on an Euler–Lagrange approach, was developed with Ansys Fluent™ and validated experimentally. Such analysis will facilitate the choice of the most conservative conditions for a flammability test. This paper is focused on a case study performed on wheat starch with the modified Hartmann tube. The dispersion process of the powder was studied with granulometric analyses performed in situ and high speed videos. Tests were performed with injections at gas pressure ranging from 3 to 6 bars and the evolution of the particle size distribution (PSD) was recorded at different ignition heights (5, 10 and 15 cm over the dispersion nozzle). The observations highlighted the presence of agglomeration/deagglomeration processes and dust segregation. Besides, a CFD simulation analysis was aimed at evaluating the impact of a set of parameters on the PSD and the local turbulence, which are closely linked to some flammability parameters. For this computational analysis, the CFD simulation was coupled with a collision treatment based on a Discrete Element Method (DEM) in order to consider the cohesive behavior of the combustible dust. Thus the results suggest performing the injection of the gases at approximately 5 bars for the flammability tests of wheat starch in order to obtain the finest PSD at a given ignition height. It is also shown that the finest PSD are obtained at 5 cm over the dispersion nozzle. However, the local instabilities and turbulence levels are so high during the first stages of the dispersion that the flame growth can be disturbed for short ignition delays. Moreover, the stabilization of the bulk of the dust cloud requires longer periods of time when the ignition sources are located at 15 cm. As a result, the recommended height to perform a flammability test is 10 cm in this case. Finally, this study proposes some tools that might improve the procedure of dust flammability testing.     

农产品和食品领域可追溯系统的研究现状

可追溯系统是产品质量安全管理控制的有效手段,能够对产品的全部生产和销售过程进行无疏漏的跟踪,以确保产品质量。通过对可追溯系统概念的阐述,介绍可追溯系统的关键技术之一——标识技术的发展状况。着重给出条码自动识别技术和无线射频识别技术(RFID)的发展,并对未来标识技术研究的新方向,生物识别技术进行展望。在对国内外农产品和食品领域可追溯系统研究和分析的基础上,针对我国在该方面的现状,提出了相应的对策及建议。     

基坑开挖引起邻侧盾构隧道开裂特性研究*

为探究基坑开挖导致邻侧既有盾构隧道出现开裂破损而带来的不利影响,采用地层-结构法与荷载-结构法相结合的计算方法,同时考虑内置钢筋对混凝土的加强作用,精细化地模拟基坑开挖影响下,非连续盾构管片结构接头处裂缝的扩展过程,揭示其开裂机制。研究结果表明:基坑开挖过程中,管片衬砌“横鸭蛋”变形模式决定了其开裂范围,即左、右拱腰附近为主开裂区;管片的裂损特征为纵向裂缝,初始裂缝由左、右拱腰外弧面逐渐向两侧接头处延展,右拱腰接头处裂缝扩展连接为沿厚度方向的环状裂缝。