全国农业展览馆中西广场展厅张弦桁架屋盖设计

全国农业展览馆新建中西广场展厅平面为150.5m×91m矩形,高度16.0m,主体为钢筋混凝土框架,上部钢屋盖为77m跨张弦桁架结构。对屋盖设计中的几种可行结构方案进行了比较,对张弦桁架整体控制尺寸的确定进行了研究。介绍了屋盖的结构平面布置,张弦桁架的受力分析及设计,撑杆上下端及支座等较为复杂的节点设计。索穿下弦杆及索端头锚固处等受力较复杂的节点采用了铸钢节点,进行了两类铸钢节点设计与受力分析。并对屋架的施工过程进行了简要介绍。     

广州盾构始发和到达端头加固方法浅析

从端头加固的目的着手,就端头加固设计及方法进行了详细阐述,并对端头加固效果检测方法作了介绍,最后分析了端头加固事故多发因素,以降低端头加固风险,确保盾构施工的顺利进行。     

卷板式护栏端头正面碰撞分析

为了解卷板式护栏端头安全性能,本文建立有限元仿真模型,运用碰撞试验对仿真模型进行可靠性验证后,对卷板式护栏端头进行正面碰撞分析。结果表明:仿真与碰撞试验结果相符,验证了仿真方法的可靠性;不同速度正面中心碰撞,端头卷板吸能效果良好,但加速度峰值随速度增加有较大增加;不同角度正面碰撞,车辆姿态良好,加速度峰值变化不大;不同位置正面碰撞端头,端头吸能效果良好,加速度峰值变化不大;卷板器质量是加速度峰值产生的最主要因素。卷板式端头可有效降低事故严重程度,保护乘员安全。     

盾构区间端头加固的设计探讨

结合工程实例，探讨了端头加固方案的选取，详细介绍了素混凝土墙端头加固的设计计算方法，并对结果进行了分析，经实践证明该加固方法效果显著，确保了工程质量。     

盾构井端头加固方案及加固范围计算研究

为满足盾构始发接收的需要、研究富水软土地区盾构端头的加固方案、探寻盾构端头加固范围的准确计算方法,以宁和中黄区间盾构端头加固为例,用对比研究、理论计算相结合的方法,研究盾构端头加固方案的适用性、选取最适合本工程项目的加固方案,对加固范围进行了理论计算。研究表明:(1)端头加固方式的选择主要受周围环境和工程地质条件制约;(2)将盾构端头加固地层简化为四周简支的弹性圆板,根据加固土体的强度反算加固范围,计算结果能满足工程需要;(3)现场施工显示端头加固体与盾构井围护桩之间的间隙是加固的簿弱环节,端头加固时须采取有效措施进行补强。本工程采用搅拌加固与冷冻法补缝的措施,达到了良好的加固效果。     

悬挑式脚手架在凯恒中心工程中的应用

通过凯恒中心外檐悬挑加钢丝绳卸载式脚手架的施工实例,针对结构的设计特点,着重介绍了悬挑式脚手架在工程施工中的搭设方法和利用锚环固定、工字钢端头拉钢丝绳等节点处理方法。     

盾构进出洞时端头土体纵向加固范围研究

为研究盾构进出洞时端头土体纵向加固范围的问题,本文基于极限平衡理论,建立盾构进出洞时端头加固土体二维稳定性分析的理论模型,推导了相应的端头土体纵向加固尺寸的计算公式,进而对一工程实例进行了计算分析得到其端头土体纵向加固长度至少应为7.43 m,最后讨论了端头加固土体粘聚力、内摩擦角、隧道直径等重要参数对端头土体纵向加固范围影响。研究结果表明:端头加固土体的粘聚力、内摩擦角对端头土体纵向加固范围影响显著,随着端头加固土体的粘聚力和内摩擦角增大时,端头土体纵向加固长度都将会减小。隧道直径越大,端头土体纵向加固长度也越长。     

地铁盾构在圆砾层端头加固设计

盾构端头加固是盾构始发、到达技术的重要环节,圆砾层进行盾构端头加固的设计及施工有其特殊性,介绍了在圆砾层采用连续墙加袖阀管注浆工法进行端头加固的工程设计实例,为盾构在类似地层进行端头加固设计提供借鉴。     

浅谈盾构法施工中端头加固的设计

结合具体的工程实例，探讨了端头加固方案的选取，详细介绍了端头土体加固的设计方法，并对其计算结果和效果检查进行了分析，经实践证明该加固方法效果显著，确保了工程质量。     

有粘结预应力大跨度及超长梁施工

结合具体的工程实例，阐述了有粘结预应力施工工艺流程和具体的施工方法，并介绍了预应力筋端头锚具处理以及梁端头节点及磨损处理方法，从而确保工程的使用功能和使用寿命。     

Alkalinity measurements within natural waters: towards a standardised approach

A discussion on the measurement of alkalinity in bicarbonate bearing and acidic waters is presented as a move towards developing a standardised approach within the aquatic sciences. The discussion is based on theoretical and practical considerations. Practical illustrations are provided from measurements of calcium bicarbonate bearing waters (River Thames) and acidic to near neutral waters from acidic soil systems with calcium bearing groundwater sources (the mid-Wales region and the Scottish Dee basin). A comparison of single endpoint and Gran procedures is made and the various error terms assessed. It is concluded that single endpoint and Gran methodologies are applicable in the standard pH titration used in aquatic research (pH 4.5-4.0). However, analytical errors increase, particularly for the single endpoint titration, the lower the endpoint/endpoint-range in pH. For the Thames, the value of a single endpoint over a Gran procedure is illustrated. The Thames results show that some buffering components may still be titrated out within the Gran titration range used: this leads to an underestimate in the alkalinity. Indeed, by making a comparison between single endpoint and Gran alkalinity measurements, the Thames results indicated the presence of unexpected buffering components: the interrogative nature of this type of analysis is highlighted. A standardised approach is outlined.     

Estimation of demographic toxicity through the double bootstrap

Toxicity to organisms is usually expressed in terms of an observable effect on individuals from which a summary endpoint (such as the NOEC or ECx) is derived for risk assessment and environmental quality standards. However, toxicity evaluated in terms of a demographic endpoint may be more relevant to such regulatory applications. In this paper the effect of toxicity on population growth rate r is explored in tandem with a 'double bootstrap' to incorporate uncertainty. Exemplifying the approach with a set of individualized life table response data obtained for Daphnia magna exposed to zinc sulphate solution, the influence of increasing concentrations is assessed. A demographic-based metric for r, the ErCx (effect on r concentration percentage), is defined to permit alternative population level estimation of a 'safe effect' concentration.     

A study of the effect of partial loss of protection on the fire resistance of steel columns

Missing fire protection material on steel structural members is generally recognized as a problem, though little information is available to quantify the effect. A finite element heat transfer analysis is used to compare the thermal response of steel columns with lost protection material when exposed to the ASTM E-119 furnace environment. Based on the predicted thermal response and using thermal endpoint criteria specified in ASTM E-119, estimates are made of the fire resistance of each column with varying amounts of missing protection. Relatively small proportional losses of fire protection material are required before significant reductions in fire resistance are realized. The degradation in fire resistance is most significant for light-weight columns and for cases where the fire protection material is missing from the flange rather than web.     

Integration of bioavailability, ecology and ecotoxicology by three lines of evidence into ecological risk indexes for contaminated soil assessment

A Weight of Evidence approach was applied to define three integrated effect indexes estimating the impairment on terrestrial ecosystems caused by the stressor(s) of concern. According to a Triad approach, the integrated effect indexes combined the information provided by the measurement endpoints of each line of evidence (chemistry/bioavailability, ecology and ecotoxicology) and allowed to analyse the impairment degree highlighted by each measurement endpoint as difference from the reference condition. Multi-Criteria Decision Analysis (MCDA) was used for the aggregation of the complementary Triad information, including expert judgement and a weighted procedure based on the endpoint sensitivity and the sensitivity of the test for ecosystem effects. The developed methodology was implemented in the DSS-ERAMANIA, Module 2, and is presented in this paper as "Integrated Effect Indexes" (IEI) sub-module. The latter has been preliminary applied to the Acna di Cengio (Italy) contaminated site; the results of this application are presented and discussed.     

竖向荷载作用下单桩三维模型参数分析

运用大型数值分析软件GTS,通过设置摩擦接触单元来模拟桩与土之间的共同作用,对桩-土进行三维有限元模拟;分析了桩-土模量比、桩的最终剪力、剪切模量、法向刚度、桩端承载力等因素对桩荷载-沉降(p-s)曲线的影响。分析结果表明:在竖向荷载作用下考虑桩-土间接触与非接触对桩顶竖向位移影响较大;接触面最终剪力、剪切模量、桩端弹簧刚度及土体的弹性模量都会对单桩在竖向荷载作用下荷载-沉降曲线产生显著的影响,而桩端承载力和接触面法向刚度不会对桩荷载-沉降(p-s)曲线产生影响。     

Laboratory tests of ammonium and barley straw extract as agents to suppress abundance of the harmful alga Prymnesium parvum and its toxicity to fish

Prymnesium parvum is a harmful alga whose blooms can cause fish kills in brackish waters. Two potential suppressants of this alga were tested, ammonium and barley straw extract (BSE), at temperatures of 10, 20 and 30 degrees C. Laboratory batch cultures were grown for 3 weeks at each temperature, with weekly doses of ammonium or BSE at either low or high levels, or a no-dose control treatment. The growth rate of P. parvum during exponential phase was highest at 20 degrees C and lowest at 10 degrees C, and was stimulated by the highest ammonium dose. Only cultures grown at 20 degrees C were toxic to fish. The highest ammonium dose abolished such toxicity and reduced the endpoint population density of P. parvum. BSE did not reduce the exponential growth rate, endpoint density, or toxicity to fish of P. parvum. The results support the use of ammonium additions, but not BSE, to suppress harmful blooms of P. parvum in those circumstances where the possible disadvantages can be managed.     

薄膜复合结构界面端热应力分布研究

以类金刚石（DLC）薄膜／基体建立理论计算模型,以粘结界面端点为顶点,采用Airy函数,建立应力随r变化的函数关系,得到界面表面的应力表达式,从而计算出膜／基结合体系在热应力下的应力分布,并采用有限元软件ABAQUS对计算结果进行了验证,证实了理论模型的可行性。     

膨润土吸蓝量测试的研究

针对膨润土行业中频频出现的吸蓝量检测纠纷,笔者提出了一种膨润土吸蓝量测试标准样的思路,同时提出另一种判断终点的方法,希望能得到行内从业人员的宝贵意见,使吸蓝量测试方法更加完善,促进行业的健康发展。     

Industry experience in the identification of the immunotoxic potential of agrochemicals

During recent years immunotoxicity has been increasingly recognized as an important endpoint in rodent short-time studies. This has been documented by FDA, OECD, and just recently in a new EPA guideline. This guideline is confined to the immunosuppressive effects of chemicals. Various parameters to detect immunotoxic effects exist, including cell counts, cell subpopulation analysis, functional tests, and/or advanced pathology. Their validity in detecting immunotoxic effects has been demonstrated to different degrees. Our experience with some of these parameters is reported here. Due to the recommendation of the guideline, it is necessary to differentiate from the context of the study data between primary and secondary immunotoxicity, the latter being an unspecific sequel of toxicity to other organs. In our studies, we found examples for both mechanisms. For primary immunotoxic substances, immunosuppression is markedly more frequent than immunostimulation, although primary effects, on the whole, occur relatively seldom during toxicological screening. In both cases, we found a good correlation between cell analysis and functional parameters on one hand and pathology on the other, thus warranting that overt immunotoxicity would not remain undetected in routine studies with high dose levels. However, the higher predictivity of functional parameters and the analysis of special subpopulations is necessary for the determination of the no-effect level and for fine differentiation during the screening of comparable immunotoxic compounds. Cyclosporin A is an example for the former, and the screening of different agrochemicals is an example for the latter aspect. As verified by the collaboration studies, an advanced histopathology of lymphoid organs, combined with flow cytometry of immune competent cells and a functional assay, is able to discriminate between primary and secondary effects as well as immunosuppression and immunostimulation, and thus to identify an immunotoxic hazard.     

琯头岭隧道下穿控制爆破技术

介绍了铁路头岭隧道下穿高速公路琯头岭隧道的工程概况,对开挖方法的选择进行了探讨,从降震措施、爆破设计及爆破施工过程监控等方面阐述了爆破控制措施,以确保公路隧道的结构安全。