框-筒结构楼房折叠爆破拆除数值模拟研究

待拆除建筑物为框-筒结构，结构强度高，稳定性好，且位于建筑物和人口密集区，周边环境复杂。为确定合理的爆破拆除方案，提出“立体化渐变起爆”方法，即爆破缺口水平面和垂直平面的相邻爆破立柱炮孔延期时间差异化，实现空间上延时的一种起爆方式。然后利用ANSYS/LSDYNA有限元软件，对V形起爆、对称起爆和“立体化渐变起爆”三种不同起爆方式的爆破方案进行模拟分析，通过对比爆堆形态、爆堆范围和结构触地时能量变化等方面，最终确定了延期时间为0.50 s的立体化渐变起爆的爆破方案。结果表明：立体化渐变起爆与对称起爆相比，结构触地时动能降低50%,内能提高47%,与V形起爆相比，结构触地时动能降低36%,内能提高31%;采用立体化渐变起爆降低了结构的塌落触地振动，结构解体完全，减小了爆堆的范围；起爆方式相同，延期时间为0.50 s时的爆堆宽度和长度及结构的塌落触地振动均比0.25 s时小；数值模拟上部结构触地时刻为3.8 s,实际上部结构触地时刻为4.0 s,而最终爆堆形成均为6.0 s,数值模拟楼房的倒塌过程和爆堆范围与实际爆破效果基本吻合。     

复杂环境61m高双曲线冷却塔拆除爆破

为成功拆除复杂环境下1座61 m高的冷却塔,根据其周边环境及结构特点,采用定向倒塌方案.首先采用机械方法开设定向窗和减荷槽,随后对19对人字柱进行爆破,使用毫秒延时爆破技术,控制单段起爆药量,成功完成拆除爆破.对拆除爆破后冷却塔的倒塌情况进行分析,冷却塔按照设计方向倒塌,解体完全,爆破振动以及触地振动控制在合理范围之内...     

复杂环境下10层不规则六边形商业楼爆破拆除

针对复杂环境下某市待拆37.8m高的商业楼呈东南—西北方向不规则六边形,具有完整性好、重心低、高宽比小、配筋多、倒塌难度大的特点,重点采取增加长轴上承重柱的爆破高度,整体形成梯形爆破切口。分3个爆区,总延时为975ms,选择合理的爆破参数进行爆破拆除;对墙、柱实施"切梁断柱"的预处理措施和可靠的防护措施,实现了商业楼按照设计范围内倒塌,严格控制了塌落振动和触地飞石,取得了良好的爆破效果,可为同类拆除爆破工程提供借鉴。     

复杂环境下10层不规则六边形商业楼爆破拆除

针对复杂环境下某市待拆37.8m高的商业楼呈东南—西北方向不规则六边形,具有完整性好、重心低、高宽比小、配筋多、倒塌难度大的特点,重点采取增加长轴上承重柱的爆破高度,整体形成梯形爆破切口。分3个爆区,总延时为975ms,选择合理的爆破参数进行爆破拆除;对墙、柱实施"切梁断柱"的预处理措施和可靠的防护措施,实现了商业楼按照设计范围内倒塌,严格控制了塌落振动和触地飞石,取得了良好的爆破效果,可为同类拆除爆破工程提供借鉴。     

复杂环境下150 t倒锥形水塔定向爆破拆除

在倒塌场地狭窄的条件下,采用定向爆破方法成功拆除了一座150 t倒锥形水塔,通过选择合理的爆破参数和起爆方式,实现了水塔瞬间后坐,达到缩小倒塌范围的目的.通过开挖减振沟、铺垫缓冲层等安全防护措施,降低了触地振动和爆破飞石的危害,确保了附近建筑物安全.     

复杂环境下12层框剪结构楼房爆破拆除

介绍了复杂环境下一栋12层框剪结构楼房的爆破拆除工程实例。采用10.4m高的复合梯形爆破切口、楔形半秒孔内延时,分3个爆区三响总延时1 020ms,实现了楼房的整体定向倒塌;通过确定合理的爆破参数、充分的预处理、间隔装药结构、双回路起爆网路等技术措施确保了安全准爆和精确定向倒塌;通过铺设缓冲垫层、炮孔包裹防护、搭设防护屏障等措施有效控制了爆破塌落振动及飞石的危害。楼房按照设计方向倒塌在设计范围内,周围建(构)筑物均没受到影响。该爆破拆除工程在精确定向,控制塌落振动及飞石等方面取得了较好的效果,可为同类工程爆破施工提供参考。     

分段控制爆破技术在210m烟囱拆除中的应用

根据国家相关政策,某电厂现有一座高210 m烟囱需要进行爆破拆除。介绍了分段控制爆破技术在实际工程中的具体应用。通过在烟囱100 m处和底部开设倒梯形爆破切口、梅花形布孔,确保烟囱倒塌方向;爆破采用毫秒延时起爆、在烟囱倒塌方向开挖减震沟、烟囱触地地面铺设松软黄土缓冲层、倒塌方向三面搭设防护屏障等措施有效地控制了爆破振动和飞石危害,达到了比较理想的效果。     

复杂环境61 m高双曲线冷却塔拆除爆破

为成功拆除复杂环境下1座61 m高的冷却塔,根据其周边环境及结构特点,采用定向倒塌方案。首先采用机械方法开设定向窗和减荷槽,随后对19对人字柱进行爆破,使用毫秒延时爆破技术,控制单段起爆药量,成功完成拆除爆破。对拆除爆破后冷却塔的倒塌情况进行分析,冷却塔按照设计方向倒塌,解体完全,爆破振动以及触地振动控制在合理范围之内。爆破后周边民房、办公室等设施未损坏,证明本次拆除爆破效果良好,达到了预期效果,可为类似工程提供参考。     

大型连体筒仓拆除爆破技术

3 2个钢筋混凝土筒仓相互连接 ,结构稳定 ,因高宽比较小 ,难以整体向同一方向倾倒。通过预处理将其分割成 4组独立的结构体 ,并使每组顺序延时起爆 ,实现了连体筒仓定向倒塌。实践证明 :要使多排筒体向同一方向倾倒 ,前排筒体的爆破切口应向上张开 ,后排爆破切口在支点抬高后应向下张开 ,同时前、后排起爆时差设为 2s、连接柱爆破的炸药单耗取 2kg/m3是合适的。此外 ,采用分组延时爆破、铺设减震垫层和开挖减震沟 ,显著降低了大型连体筒仓的触地震动     

复杂环境下薄壁式倒锥形水塔爆破拆除

通过理论计算和经验类比等手段,解决复杂环境下1座薄壁钢筋混凝土倒锥形水塔的爆破拆除,因倒塌场地小,筒壁薄、钢筋密、重心高,易产生后坐甚至爆而不倒的问题,设计了合理的爆破切口和定向窗尺寸、爆破技术参数、起爆网路等;根据倒塌失稳计算和预留支撑筒壁的强度校核,验证了爆破切口高度及长度的合理性;对爆破振动、飞石和塌落振动等爆破危害进行了校核。结果显示,起爆后水塔缓慢倾倒,2 s后水塔出现下坐,下坐高度约5 m;倒塌趋势形成后,下坐并未影响倒塌方向;爆破未造成周边民房损坏,未发生安全事故,可为类似工程提供借鉴。     

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.……     

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...     

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.……     

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.     

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.     

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