超大型陆上沉井封底施工技术

泰州大桥北锚碇沉井封底总方量超过30 000 m3,为目前国内立方量最大的水下封底混凝土施工工程,其施工难度大,现场组织要求高。从沉井清基、封底设备布置、封底混凝土施工工艺等方面概略介绍泰州大桥北锚碇沉井封底施工技术。     

陆上特大型沉井施工技术

泰州大桥主桥采用主跨2×1080m三塔两跨两锚碇悬索桥,其中南、北锚碇基础为特大型沉井,矩形平面尺寸为67.9m×52.0m,高度分别为41m,57m。针对锚碇基础覆盖层深厚、基础尺寸巨大、沉井下沉深度深等特点,通过施工技术的攻关,顺利完成了砂桩复合地基处理、沉井制作和拼装、钢壳沉井混凝土填充、混凝土沉井接高施工、水力机械冲吸式排水下沉和空气吸泥机吸泥下沉等多项施工工序,为今后陆上特大型沉井施工提供了借鉴。文章简要介绍了南、北锚碇陆上特大型沉井的施工技术。     

润扬大桥悬索桥北锚碇基础接触应力仿真分析

针对润扬大桥悬索桥北锚碇基础的浇筑施工、运行过程，基于大型有限元分析软件Marc进行二次开发，建立了锚碇基础和土体共同作用的三维有限元仿真计算模型。考虑锚碇基础浇筑过程中地下水位改变引起基底水压力的变化对锚碇基础接触应力分布的影响，对锚碇体浇筑到运行的全过程进行了仿真数值计算，揭示了岩层地基上悬索桥重力式嵌岩锚碇基础接触应力在施工到运行过程中的变化规律。工程实例数值计算结果表明，在不同施工浇筑阶段，尽管锚碇基础不同部位的接触应力呈现出不同的变化特征，北锚碇基础在施工到运行全过程中基础接触应力总体满足设计要求。     

万州长江二桥锚固系统的计算分析与选型

万州长江二桥是一座大型悬索桥,其锚固系统的质量直接控制了大桥能否正常运行。本文根据铁道部第一设计院提供的设计方案和有关资料,对该桥锚固系统的各种工况进行了力学计算与分析。作者在此基础上,突破常规,提出了一种新型锚固系统,并对其进行了力学计算。通过两种锚碇的对比分析,为设计部门对锚固系统的进一步设计与选型提供了依据。     

水下嵌入式混凝土锚体锚碇力试验研究

在分析国内外现有嵌入锚锚碇力计算方法和大量物理模型试验的基础上,采用正交试验设计分析方法,定量地研究了土质、埋深、拉力角度、锚型等因素对水下嵌入式混凝土锚体锚碇力的影响程度和规律,在此基础上提出了一套更为合理的锚碇力计算公式。研究成果与已有的工程实例相吻合,并且作为国家军用标准的编制依据之一,已成功地用于实际工程中。研究的锚型和推荐的公式可用于浮码头、单点系泊系统等非临时性浮式设施的水下锚体设计。     

钢筋混凝士结构物保护层厚度控制技术研究

文章以在建的马鞍山长江公路大桥为依托,结合工程实际,在塔柱、墩柱、锚碇沉井、箱梁等混凝土结构物施工过程中采取一系列的保护层控制措施,通过检测验证,相关结构物保护层厚度得到了很好控制,确保了混凝土结构中受力钢筋的有效锚固和构件的耐久性,达到了提高了混凝土结构物质量的目的,并为今后？昆凝土保护层厚度控制提出参考和建议。     

一种新型悬索桥主缆锚固系统设计概念综述

区别于预应力锚固系统,在传统钢框架后锚梁锚固系统的基础上,南京长江第四大桥采用一种新型悬索桥主缆锚固系统——分布传力式锚固系统。钢框架后锚梁锚固系统依靠后锚梁刚性承载,应力集中明显,有一定的结构和安全风险。分布传力式锚固系统锚固区域通过布置多排钢筋混凝土榫剪力键(PBL),变刚性承压承载为柔性承载,索力渐次传递至锚体混凝土;变集中承载为分布传力式承载,扩大了传力区域,减小应力集中,降低结构风险;利用PBL良好的延性,同时通过设置末端承压板,为结构整体提供足够的安全储备。本文对这种新型锚固系统的设计作了简要介绍。     

空气幕辅助沉井下沉施工工艺浅析

本文结合了马鞍山长江公路大桥北锚碇沉井下沉施工,简要的分析了利用空气幕辅助大型沉井下沉的施工工艺。     

超大型沉井降排水下沉施工

泰州大桥北锚碇沉井基础长67.9m、宽52m、高57m,在沉井下沉的初期,采用降排水下沉。降排水下沉施工成本相比不排水下沉低,且下沉效率高,易控制,可形成良好的下沉导向,并确保沉井的下沉速度和精度,适宜在粉细砂、软塑性亚黏土等地质条件下采用。文章以泰州大桥北锚碇沉井基础为例,介绍了超大型沉井降排水施工的降排水下沉施工工艺。     

岱山大桥重力式锚碇大体积混凝土裂缝控制研究

大体积混凝土在现阶段已经占据了桥梁施工中的关键地位,尤其是涉及到规模较大的桥梁建造而言。某些大体积混凝土之所以会呈现裂痕的状态,其中根源应当在于材料固有的抗拉强度没能超出外在的拉应力。具体在全过程的桥梁施工中,针对上述的混凝土裂缝有必要着眼于及时控制,避免其表现为程度较重的桥梁施工损失。在此前提下,关于控制混凝土裂缝选择了岱山大桥作为其中的施工控制对象,从而针对重力式锚碇构造的桥梁建筑物予以必要的裂缝控制。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.