装配式厂房曲线预应力构件施工技术

1 概况 浦沅工程机械厂结构车间为7连跨排架结构单层厂房，厂房轴线长240m，宽168.45m，建筑面积40.632m2。厂房柱距：中柱12m×24m；边柱6m，屋盖结构由12m跨托架、24m跨屋架、钢支撑和6m×1.5m混凝土屋面板组成。厂房沿纵向和横向各设有2条和1条变形缝，厂房内共设有起重量为5～15t桥式起重机18台。 该工程在现场预制的构件有屋架、托架、吊车梁等共计三大类600余件，其中主要受力钢筋为曲线预应力筋的构件有两类338件，详见表1。……     

大跨度部份预应力混凝土门架结构的施工实践

一、工程概况珠海玻璃纤维厂联合厂房建筑面积18600m~2,采用了新型的部份预应力混凝土、多跨连续、大跨度门式刚架结构,如题头图,其跨度分别为31.5m、33m、3L5m、14m,柱距6m。兹分述如下:1、门架系由“Y”形、“Г”形柱、“人”字梁等预应力构件经吊装拼接而成,梁柱之间为刚接,柱与杯口之间为铰接。构件截面为矩形,宽30cm,截面高度随结构内力增加而沿轴线变化,柱与其悬臂拐角处设计为直线加腋,其外形如图1a-d,构件混凝土等级 C40。     

超大跨度过河管廊吊装施工方案浅析

在某钢厂高炉建设中,高炉的油、水、气等多种介质的输送管线跨河道敷设,设计通过长约56 m的钢结构管廊横跨河道。过河管廊由型钢制作,截面尺寸5m×4.42m,总重82.5t。今主要介绍利用"浮船"作为河道内的临时可移动支撑点,合理使用多机抬吊,解决大跨度构件尤其是跨河道构件的整体吊装难题。     

控制剪力墙连梁构件失效模式的实用设计方法

为了满足对结构抗震设计的更高要求或实现基于性能的抗震设计方法,对连梁构件的受力和破坏机理进行了分析,提出了连梁构件失效模式判断系数fλm,它既能考虑连梁构件的外部因素(剪切反力和弯曲反力)又能考虑截面的内部因素(极限承载力)。选取了对连梁构件失效模式起主要作用的跨高比作为参数,设计了不同跨高比的四个连梁构件,并采用有限元中的实体单元进行了弹塑性数值模拟,计算结果证实了采用提出的连梁构件失效模式判断系数对连梁失效模式判断是合理且可行的,并根据计算结果给出了不同跨高比连梁构件失效模式系数的界限值。从而可对一般工程中的剪力墙连梁构件进行设计或校核。     

钢筋混凝土梁设计经济性分析

对一钢筋混凝土简支梁在不同截面设计中的经济性进行了比较分析,根据构件设计用料关系,分析了该构件的跨高比,得到一个接近数值11的跨高比较优设计值,从而提高了钢筋混凝土梁的经济效益。     

结构设计新规范讲座 第三十六讲——钢筋混凝土结构受扭构件例题

例题 例1 设有均布荷载作用下的矩形截面梁,其承受的内力有:弯矩设计值M=120kN·m,剪力设计值V=100kN,扭矩设计值T=9kN·m。试设计此梁。 解 此题为钢筋混凝土受弯剪扭构件的计算题。 一、选定构件的截面尺寸和材料强度等级     

轴心受压钢构件稳定系数的讨论

1轴心受压钢构件d类截面稳定系数的解析表达式在高层建筑钢结构中,受力很大的受压构件往往由厚度t≥40mm的厚钢板组成。此类厚钢板的残余应力不但沿板宽变化,在板厚方向也有显著变化。在板件表面常以残余压应力为主,对构件稳定的影响较大。为了对此类厚板组成的受压构件进行准确设计,国家规程[1]、规范[2]在原有a,b,c三类截面的基础上,增加制定了稳定承载力更低的轴心受压钢构件d类截面的稳定系数曲线。在文[1],[2]中,d类截面的稳定系数φ曲线均采用与a,b,c三类截面相同的公式描述,但系数α1,α2,α3取值不同,即正则化长细比λn=λπfyE(1)…     

钢结构五连跨桁架吊装技术

1工程概况及结构特点日立环球存储硬盘驱动器装配厂房钢结构工程位于深圳市大工业区,钢结构由中建二局深圳分公司承建。厂房采用全钢结构单层框架 支撑体系,长度方向共277.5m,分为1～20轴线,最大跨度为15m。宽度方向上连续五跨,分为A～J轴线,五连跨跨度分别为30m、30m、30m、16m和14m;总吊装工程量为5789t。屋面为单坡,A轴高,J轴低,因此在J轴设计有天沟和排水管。厂房由钢柱、桁架、梁、支撑、平台、楼梯、猫道、次结构等组成。采用、。,焊接和高强螺栓连接,主要构件截面为H型钢、焊接H型钢和箱形截面。柱间支撑采用双T型钢,屋面水平支…     

腹板开孔复杂卷边冷弯薄壁槽钢受弯构件稳定性试验研究

为了研究腹板开孔对不同截面形式冷弯薄壁型钢受弯构件稳定性能的影响，对腹板开孔的复杂卷边槽钢(B1截面)、Σ形复杂卷边槽钢(B2截面)共计8个简支梁试件进行稳定性试验研究，其中研究纯弯的试件4个，非纯弯的试件4个。试验结果表明：B2截面试件的受弯承载效率均高于B1截面试件，B1截面试件受开孔的影响较大，而B2截面试件由于腹板加劲肋的设置减弱开孔对截面的影响，两者在开孔处均发生明显的剪切变形。与相同条件下不开孔试件的试验结果对比表明：开孔试件的极限荷载均有不同程度的降低，非纯弯状态的下降幅度大于纯弯状态的；开孔试件的失稳模式基本不变，但破坏位置多发生在孔洞截面处。对试验进行有限元模拟分析，计算结果与试验结果吻合良好。在此基础上，利用有限元模拟对比相同截面腹板开孔和不开孔受弯构件的应力分布云图，结果表明，孔洞的存在改变了构件的应力分布，使孔洞周边区域发生应力集中现象，B1截面开孔受弯构件最大应力主要集中在弯剪段孔洞附近，而B2截面开孔后最大应力则主要集中在荷载作用点附近的受压翼缘上。     

冷弯薄壁型钢开口三肢拼合立柱轴压性能有限元分析

建立了考虑材料、几何和接触非线性的有限元模型,利用ANSYS有限元程序分析了长细比、螺钉连接间距、截面板件最大宽厚比对冷弯薄壁型钢开口三肢拼合立柱轴压性能的影响。结果表明:立柱长细比对A、B两类截面拼合立柱轴压承载力和轴压性能有很大影响,随着立柱长细比的增大,立柱轴压极限承载力逐渐降低;当螺钉连接间距为450、300、150mm时,A、B两类截面拼合立柱轴压极限承载力和刚度变化均不大;由于基本构件板材厚度不同引起截面板件最大宽厚比的不同,对A、B两类截面3种长度的拼合立柱的承载力和刚度影响很大;对于A、B两类截面立柱,当立柱长度和截面厚度相同时,基本构件腹板高度由89mm增加到140mm,拼合截面轴压立柱轴压极限承载力变化不大。     

Ecological succession in mountain lake ecosystems of Southern Siberia after the introduction of the peled – Coregonus peled (Gmeli, 1778)

Abstract

This article summarizes a long-standing study of the process of introduction of the peled to the Southern Siberian mountain lake ecosystems. The peled has adapted to changes in food supply. Pressure of the euryphagous peled caused the substitution of larger forms of zooplankton by smaller ones. Similar changes occurred in the content of phytoplankton. Succession of zoobenthos in the littoral part of the lakes manifested itself as the decrease in the total biomass, in its part of zoobenthos (Gammarus) and as the increase in the biomass of other groups. The opposite changes were encountered in the profundal zone of zoobenthos (the decrease in the total biomass owing to the existence of larger forms of alpha-polysaprobes). The restructuring observed in various communities signifies the substantial changes in the whole process of generation and transformation of organic substance in the mountain ecosystems with the dominance of the introduced peled.     

The effects of changing water flow velocity on the formation of biofilms and water quality in pilot distribution system consisting of copper or polyethylene pipes

We studied the effects of flow velocity on the formation of biofilms and the concentration of bacteria in water in copper and plastic (polyethylene, PE) pipes. The formation of biofilms increased with the flow velocity of water. The increase in microbial numbers and contents of ATP was clearer in the PE pipes than in the copper pipes. This was also seen as increased consumption of microbial nutrients in the pipeline system. This indicates that the mass transfer of nutrients is in major role in the growth of biofilms. However, the increased biomass of biofilms did not affect microbial numbers in the water. Rapid changes in water flow rate resuspended biofilms and sediments which increased the concentrations of bacteria and copper in water. The disturbance caused by the changing water flow was also seen as an increase in the particle counts and water turbidity recorded with online instrumentation.     

Alteration of arsenopyrite in soils under different vegetation covers

The weathering of arsenopyrite (FeAsS) has been monitored in soils using an in situ experimental approach. Arsenopyrite in nylon experimental bags was placed in individual horizons in soils in spruce (litter, horizons A, B, and C), beech (litter, horizons A, B, and C) and unforested (horizons A, B, and C) areas and left in contact with the soil for a period of 1 year. The individual areas on the ridge of the Krušné hory Mts., Czech Republic, had the same lithology, climatic and environmental conditions. Scorodite (FeAsO₄·2H₂O) was identified as a principal secondary mineral of arsenic (As) formed directly on the surface of the arsenopyrite. Scorodite was formed in all the areas in all soil horizons. The amount of scorodite formed decreased in the series beech, spruce and unforested areas. In forested areas, there was a larger amount of scorodite on arsenopyrites exposed in organic horizons (litter, A horizon). The greater rate of arsenopyrite alteration in organic horizons in the beech stand compared to spruce stand is probably a result of faster mineralization of organic material with resulting production of nitrate and better seepage conditions of soil in this area. Speciation of As determined using the sequential extraction technique demonstrated that As was bonded in the soils primarily in the residual fractions prior to the experiment. The As content in the mobile fractions increased in the organic horizon in the forested areas after the experiments.     

未来高校图书馆建筑空间构成及设计特点初探

从高校图书馆发展的外部动因,使用主体的心理、行为特征和现代化设备对图书馆的影响三个方面来分析研究图书馆建筑发展的趋势和特点,归纳出未来高校图书馆建筑的功能布局及空间组织结构特点,总结出设计中要考虑的诸多因素,以期更好地指导高校图书馆的设计与建设。     

探究“虚实”空间关系，创造个性化的城市空间场所

作者利用空间的“虚、实”概念,结合格斯塔心理学的“图底”关系,类比分析中国水墨画的留白艺术手法及生态系统中的细胞繁衍规律,通过张家界城市绿化广场周边地段的概念设计的创作实践,提出创造个性化的城市空间场所工作中虚实空间的理念与原则目标。     

钢结构的应用前景及教学思考

本文根据钢结构的特点 ,重点介绍了钢结构在欧洲、美国和日本等广泛应用的情况。我国改革开放以来 ,钢产量持续增加 ,已经达到了约 1.6亿吨 ,钢结构产业政策 ,也从上世纪中叶的“节约用钢” ,发展到本世纪初的“推广用钢” ,这是我国钢结构政策的重大转变。结合我国部分高校中对钢结构教学认识滞后的情况 ,提出了在土木工程专业的技术基础课中设置钢结构设计原理的参考教学内容和在对应专业方向中设置相应钢结构设计的教学思路。     

Polycyclic aromatic hydrocarbons (PAHs) in agricultural soil and vegetables from Tianjin

Several types of vegetables were collected from two contaminated sites in Tianjin, China. The bulk soil and the rhizosphere soil samples were also collected from the same plots. Sixteen PAHs in the samples were measured. The total concentrations of PAH16 in the bulk soil from the two sites were 1.08 and 6.25 microg/g, respectively, with similar pattern. The concentrations of PAH16 and individual compounds in the rhizosphere were significantly higher than those in the bulk soil with mean values of 2.25 and 7.82 microg/g for the two sites, respectively. The contents of both total and dissolved organic matter in the rhizosphere were also higher than those in the bulk soil. Almost all PAH compounds studied were detected in both roots and aerial parts of the vegetables studied. Abundance of higher molecular weight PAHs in vegetable, however, was lower than that in soil. Concentrations of PAH16 in vegetable were higher than those reported in the literature for other areas. It appears that agricultural soils and vegetables in Tianjin, especially those from the site located immediately next to an urban district and irrigated with wastewater for several decades, are severely contaminated by PAHs. Among the eight types of vegetable studied, the highest concentration of PAHs was found in cauliflower. By average, the concentration of PAH16 in the aerial part of vegetables was 6.5 times higher as that in vegetable root, suggesting that foliar uptake is the primary transfer pathway of PAHs from environment to vegetables.     

氡在破碎花岗岩巷道及围岩中的运移机制解析

依托某破碎花岗岩巷道工程,以多孔介质中气体的渗流理论为基础,综合考虑影响氡在破碎花岗岩山体及巷道中运移和析出的多种因素,构建了氡的数值计算模型,给出了山体和通风巷道中的氡浓度计算公式,模拟并比较了自然状态和微正压通风状态下山体中氡浓度分布的变化情况,并对微正压通风状态下巷道中氡浓度的变化情况进行模拟和验证。研究结果表明:扩散作用和渗流作用是巷道围岩中氡运移的主要机制;微正压通风条件下巷道中氡的运移主要受通风作用、围岩的射气作用和氡的衰变作用共同影响;微正压通风能够改变围岩中氡的渗流方向,是巷道降氡的有效手段。     

Biomonitoring of mercury in polluted coastal area using transplanted mussels

The Kastela Bay is heavily polluted with inorganic mercury originated from direct discharges from the chlor-alkali plant, which operated in the period from 1950 to 1990. Even though the plant was closed 15 years ago, elevated levels of total mercury are still evident in surface sediments of the bay. In order to assess the availability of remobilized mercury to marine organisms, cultured mussels (M. galloprovincialis) were transplanted from pristine area to Kastela Bay, in the period from September 2000 to March 2001. Mussel samples were collected for the analysis of THg and MeHg in whole soft tissue, gills and digestive gland. Surface sediments and suspended matter were collected for the analysis of THg. Digestive gland was the target organ for the accumulation of THg, while concentrations of MeHg were similar in all analyzed tissues. The percentage of MeHg in mussel tissues (4-27%) was characteristic for the areas contaminated with inorganic mercury. A significant negative correlation was observed between the THg concentration in the tissues and the percentage of MeHg. Concentrations of THg in mussel tissues, which were decreasing from the source of contamination in an anticlockwise direction towards the exit of the bay, were significantly positively correlated to THg content in sediment and suspended particles. Spatial distribution of mercury species (THg and MeHg) in different environmental compartments was in accordance with the prevailing circulation in the bay. Data obtained through 6 months of biomonitoring experiment indicated that digestive gland was more sensitive indicator of THg concentrations in the environment than the whole organism or gills. As for MeHg, all tissues were equally suitable as biomonitors of MeHg concentrations in the environment.     

Heterotrophic and mixotrophic growth of Micractinium pusillum Fresenius in the presence of acetate and glucose: effect of light and acetate gradient concentration

The main objective of this study was to determine the importance of secondary mechanism of organic carbon utilization (mixotrophic and heterotrophic modes) in addition to CO2 fixation (photoautotrophic mode) in the green alga, Micractinium pusillum Fresenius (chlorophyta), isolated from a waste stabilization pond. The growth was studied in the presence of acetate and glucose. The incorporation rate of 14C- acetate was measured in the light and in the dark at different concentrations. Finally, in order to underline the role of photosynthesis and respiration processes in the acetate assimilation, the effect of two specific metabolic inhibitors, a specific inhibitor of photosystem II (DCMU) and an uncoupler respiratory (DNP), has been studied. The obtained results showed that M. pusillum grows in the presence of organic substrates, i.e., glucose and acetate, in the light (mixotrophic growth) as well as in the dark (Heterotrophic growth). The growth was much more important in the light than in the dark and more in the presence of glucose than of acetate. In the light, the presence of acetate led to a variation of growth parameters mumax, iotaopt, and beta. The effect of acetate gradient on the growth of the microalga was severe as soon as its concentration in the medium was higher. The acetate uptake followed a Michaelis-Menten kinetic in the light as well as in the dark. The capacity of assimilation was slightly higher in the dark. The utilization of DNP and DCMU indicates that acetate incorporation is an active process depending on both anabolic (photosynthesis) and catabolic (respiration) metabolisms, corroborating the model of the Michaelis-Menten kinetic.