上跨高速公路无铰拱桥控制爆破拆除

介绍了兰海高速公路广元至南充段K119+429上跨钢筋混凝土无铰拱桥爆破拆除案例,为实现桥体充分解体,并确保下部高速公路结构完整及实现高速公路的快速畅通。根据桥梁结构特点及要求,采取桥梁拱圈及横墙爆破解体的原地坍塌拆除方案。在关键受力部位拱圈上设置8个爆破切口,拱脚处切口长度为1.92m,其余切口长度为3.02m³.15m;两侧边跨横墙上对称设置6个爆破切口,切口长度依次为8.75m、3m和2m。桥梁正下方沿桥纵向铺设4.5mm厚度钢板,中央隔离带位置钢板铺设厚度9.0mm,钢板上部铺设厚度为2m的砂土垫层。在精细的施工组织和严密的安全防护措施下,取得了理想的爆破效果,可为类似工程提供参考。     

上跨高速公路无铰拱桥控制爆破拆除

介绍了兰海高速公路广元至南充段K119+429上跨钢筋混凝土无铰拱桥爆破拆除案例,为实现桥体充分解体,并确保下部高速公路结构完整及实现高速公路的快速畅通。根据桥梁结构特点及要求,采取桥梁拱圈及横墙爆破解体的原地坍塌拆除方案。在关键受力部位拱圈上设置8个爆破切口,拱脚处切口长度为1.92m,其余切口长度为3.02m~3.15m;两侧边跨横墙上对称设置6个爆破切口,切口长度依次为8.75m、3m和2m。桥梁正下方沿桥纵向铺设4.5mm厚度钢板,中央隔离带位置钢板铺设厚度9.0mm,钢板上部铺设厚度为2m的砂土垫层。在精细的施工组织和严密的安全防护措施下,取得了理想的爆破效果,可为类似工程提供参考。     

复杂环境下334m钢筋混凝土刚架拱桥爆破拆除

待拆除大桥长334m,主跨为钢筋混凝土刚架拱桥,引桥为圆柱形桥墩简支梁桥。由于桥体主结构承载力不能满足安全要求,需要爆破拆除。结合切口设计和"移位偏角"方式为圆柱形桥墩、拱肋确定了合理的爆破切口高度及有关参数,采用毫秒分段延时技术降低一次性齐发药量,运用逐点起爆非电起爆网路确保桥体逐垮塌落,通过立体式防护挡墙防止爆破飞石的扩散。结果表明,移位偏角法、逐点起爆非电起爆网路、立体式防护挡墙的运用,实现了桥梁按设计要求倒塌,有效控制了爆破冲击波、桥体塌落振动、爆破飞石及飞溅物、浪涌等爆破危害效应,爆破取得了理想效果。     

立体交叉石拱桥爆破拆除振动危害控制

纳雍维马石拱桥与简支梁新桥水平方向呈41°斜交,全长为68 m,从新桥第5跨下28.5 m穿过,距新桥4#立柱仅0.8 m。为确保紧邻既有桥梁顺利的爆破拆除,采用原地缓冲塌落控制爆破技术来确保紧邻既有桥梁安全。根据石拱桥自身结构特点,爆破拆除石拱桥对周围环境的破坏,尤其是对4#立柱和墩基础的危害,我们进行了爆破和塌落振动分析,工程中采取了喇叭型爆破切口、上移东西拱脚爆破切口至第二腹拱、增加靠近4#立柱破碎切口、采用起爆网路时差“由西向东、由南向北”顺序,调整靠近4#立柱炮孔抵抗线、各个爆破切口采用不同的炸药单耗等方法,来实现石拱桥爆破拆除有向南倾倒的趋势的同时,满足塌落体最小化以及减小爆破对周围环境的影响,并利用渣石和软土堆码缓冲减振堤、搭设防护排架等安全防护措施,确保了石拱桥爆破拆除的可靠性和安全性。利用塌落振动公式计算新桥4#立柱对应桥面振动速度为3.9～5.2 cm/s,与测振仪测得该点最大振动速度3.879 cm/s相近,验证了爆破拆除石拱桥设计思路及相关参数的选取是科学、合理的。爆破拆除取得理想的效果。     

复杂环境下334m钢筋混凝土刚架拱桥爆破拆除

待拆除大桥长334m,主跨为钢筋混凝土刚架拱桥,引桥为圆柱形桥墩简支梁桥。由于桥体主结构承载力不能满足安全要求,需要爆破拆除。结合切口设计和"移位偏角"方式为圆柱形桥墩、拱肋确定了合理的爆破切口高度及有关参数,采用毫秒分段延时技术降低一次性齐发药量,运用逐点起爆非电起爆网路确保桥体逐垮塌落,通过立体式防护挡墙防止爆破飞石的扩散。结果表明,移位偏角法、逐点起爆非电起爆网路、立体式防护挡墙的运用,实现了桥梁按设计要求倒塌,有效控制了爆破冲击波、桥体塌落振动、爆破飞石及飞溅物、浪涌等爆破危害效应,爆破取得了理想效果。     

6层砖混结构楼房折叠爆破拆除

介绍了1栋6层砖混结构楼房的单向折叠爆破拆除实例.由于环境限制,必须控制爆堆范围.采用双切口、自上而下延时起爆的单向折叠爆破方案;下部切口布于第1层,上部切口布于第4层,2切口间延时取0.31 s;对非爆楼层的承重墙体进行了预处理;并对保护目标采取了合理的安全保护措施;爆破达到了预期的效果.介绍了爆破参数选择、起爆网路、预处理、安全防护及空心砖墙的钻眼爆破方法等内容,可供类似工程参考.     

高速公路无铰拱天桥爆破拆除

为了沈海高速公路开平至阳江段K110+254无铰拱钢筋混凝土(C30混凝土)跨线天桥顺利爆破拆除,针对该天桥为中承式等截面悬链线无铰肋拱桥,净跨39 m,净高约6.83 m,桥面净宽10.2 m的结构特点,根据施工要求,采取拱圈钻孔爆破的原地坍塌方案。由于施工作业不能影响桥下高速公路的运营,因此在高速公路路面铺垫缓冲减振层,保护路面不受损坏;拱圈上共设置10个爆破切口,拱脚处爆破切口长3.8 m,其他切口长3.0～3.2 m,两侧桥台及立柱在不影响桥下高速公路通行的前提下使用机械破碎。采用计算机软件模拟切割后桥面和拱圈的受力情况,以选择合理的切割位置和合适的钻孔布置。对拱圈钻孔装药位置使用密目网和密竹栅栏进行爆破飞石近体防护,拱顶堆载沙包防护。使用多段毫秒延时导爆管雷管起爆网路,逐渐对称地形成爆破切口,确保桥体按预定的倾倒方向整体坍塌,由此实现了运营中高速公路的无铰拱天桥爆破拆除。     

高速公路无铰拱天桥爆破拆除

为了沈海高速公路开平至阳江段K110+254无铰拱钢筋混凝土(C30混凝土)跨线天桥顺利爆破拆除,针对该天桥为中承式等截面悬链线无铰肋拱桥,净跨39 m,净高约6.83 m,桥面净宽10.2 m的结构特点,根据施工要求,采取拱圈钻孔爆破的原地坍塌方案。由于施工作业不能影响桥下高速公路的运营,因此在高速公路路面铺垫缓冲减振层,保护路面不受损坏;拱圈上共设置10个爆破切口,拱脚处爆破切口长3.8 m,其他切口长3.0～3.2 m,两侧桥台及立柱在不影响桥下高速公路通行的前提下使用机械破碎。采用计算机软件模拟切割后桥面和拱圈的受力情况,以选择合理的切割位置和合适的钻孔布置。对拱圈钻孔装药位置使用密目网和密竹栅栏进行爆破飞石近体防护,拱顶堆载沙包防护。使用多段毫秒延时导爆管雷管起爆网路,逐渐对称地形成爆破切口,确保桥体按预定的倾倒方向整体坍塌,由此实现了运营中高速公路的无铰拱天桥爆破拆除。     

复杂环境下钢筋混凝土双曲拱桥爆破拆除

在四周建筑物较多较近的情况下,采用控制爆破技术成功拆除一座长175 m、三跨钢筋混凝土双曲拱桥.介绍了该桥的爆破方案和主要的爆破参数,根据大桥的特点,分别在桥墩、拱肋和立墙上布置炮孔,对两边桥面预切割;采用孔内外微差起爆网路,并加强炮孔四周覆盖,成功实现了对大桥一次性坍塌拆除,并做到了附近的建筑物安然无恙的目标.     

复杂环境下双曲拱桥的控制拆除爆破

为确保桥梁顺利拆除，保证新桥安全，结合现场环境条件，采用原地坍塌的爆破方案，对拱桥的主拱肋和承重立墙进行钻孔爆破。针对双曲拱桥的特点，精细设计，精心施工。采用数码电子雷管延时起爆技术和筑减震坝等措施降低桥体塌落振动。采用覆盖防护、近体防护和保护性防护等安全防护措施。确保了新桥的安全，取得了理想的爆破效果，可为类似爆破工程提供参考。     

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.     

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.     

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.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.