A simplified approach for negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge

A simplified approach was proposed to analyze the negative skin friction calculation of special-shaped pile considering pile-soil interaction under surcharge. Based on the concentric cylinder shearing theory, considering the changes of pile shape(such as, taper angle and diameters of pile base, etc.), the load-transfer of special-shaped pile was built. The accuracy of the developed simplified approach was verified by numerical simulation model with the same condition. Then, the influence factors, such as, taper angles, the diameter of pile base, surcharge, and pile-soil interface parameters were analyzed and discussed. The results show that the developed simplified approach can calculate NSF of special-shaped pile under surcharge effectively. A limited parametric study indicates that in many practical situations special-shaped piles(such as belled wedge pile shown in this work) offer a design option that is more economical than traditional uniform cross-section piles.

Surface quality of extruding metal special-shape products and frictional behavior in optimized die cavity

With the help of Complex Function Mapping theory, the complicated three-dimensional deformation problems are transferred into two-dimensional problems, and the function of strain ratio field is analyzed in the metal plastic extruding deformation. Taking the strain-hardening effect of metal deformation into account, the relationship between friction behavior and optimized mathematical model is analyzed by the numerical analysis friction energy dissipation function. As a result, the method of lowering the material hardening and decreasing the reduction ratio over multi-procedures can be used to improve the surface quality of metal special-shape extrusion products.

Experimental Study on Seismic Behavior of Exterior Joints of Special-shaped Columns with Different Lengths of Limbs

Four exterior joints with special-shaped columns which have different lengths of limbs are tested under low cyclic loading. Speeial-shaped columns adopted are L- and T-shaped in section. It can be concluded that crack pattern, failure mode and shear strength of joints are affected by the length of limb, and that shear strength and ductility increase with the length of limb; the joints with the flexural failure of the beam have better seismic behavior than those with the shear failure of the joint core.

Design of Special-shaped Interchange between Expressway and Urban Road in Mountainous Cities

Driven by the rapid economic development,the development of transportation in China has begun to move towards mountainous areas.The climate environment,topography and landform of mountainous cities are different from those of plain areas.In mountainous cities,the area of opposite interchanges between expressways and urban roads is generally large,which has a certain contradiction with the topographic conditions of mountainous cities.Therefore,it is necessary to reasonably design the opposite interchanges between expressways and urban roads in mountainous cities.The author explores and analyzes the factors restricting the special-shaped interchange between expressway and urban road in mountainous cities and the main fbnns of special-shaped interchange,and puts forward a reasonable design scheme,hoping to make a smooth development of the special-shaped interchange in mountainous cities.

Conformal mapping modeling of metal plastic deformation and die cavity in special-shaped extrusion

With the help of Complex Function Mapping studied results, the analysis function of Conformal Mapping is set up. Since the complicated three dimension’s deformation problems are transferred into two dimension problems, both the stream function and strain ratio field are analyzed in the metal plastic deformation. Using the upper-bound principles, the theory of metal deformation and die cavity optimized modeling is established for random special-shaped product extrusion. As a result, this enables the realization of intelligent technique target in the die cavity of CAD/CAM integration.

Similar extrusion and mapping optimization of die cavity modeling for special-shaped products

Aimed at the modeling issues in design and quick processing of extruding die for special-shaped products, with the help of Conformal Mapping theory, Conformal Mapping function is determined by the given method of numerical trigonometric interpolation. Three-dimensional forming problems are transformed into two-dimensional problems, and mathematical model of die cavity surface is established based on different kinds of vertical curve, as well as the mathematical model of plastic flow in extruding deformation of special-shaped products gets completed. By upper bound method, both vertical curves of die cavity and its parameters are optimized. Combining the optimized model with the latest NC technology, NC Program of die cavity and its CAM can be realized. Taking the similar extrusion of square-shaped products with arc radius as instance, both metal plastic similar extrusion and die cavity optimization are carried out.

Study on a probabilistic algorithm for the forming and 3D characterization of special-shaped surfaces under profile grinding

Profile grinding is the most crucial method for the ultra-precision machining of special-shaped surfaces.However,profile grinding produces a unique machining profile,and many random factors in the machining process lead to complex surface characteristics.In this study,the structural and probabilistic characteristics of the profile grinding of a special-shaped surface were analyzed,and a probabilistic algorithm for the forming and 3D characterization of special-shaped surfaces under profile grinding was developed.The forming process of a GH738 blade tenon tooth surface was considered as an example to demonstrate the algorithm.The comparison results showed that the simulation results had similar surface characteristics to the measurement results,and the relative error range of the 3D roughness parameter was 0.21%–19.76%,indicating an accurate prediction and characterization of the complex special-shaped surface under the action of multiple factors.

Investigation on performance of special-shaped 8-quadrature amplitude modulation constellations applied in visible light communication

Light-emitting diode(LED)-based visible light communication(VLC) has become a potential candidate for nextgeneration ultra-high-speed indoor wireless communication. In this paper, four special-shaped 8-quadrature amplitude modulation(QAM) constellations are investigated in a single-carrier VLC system. It is numerically verified and experimentally demonstrated that circular(7,1) shows obvious superiority in the performance of the dynamic range of signal voltage peak-to-peak(vpp) value and bit error rate(BER). Next best is rectangular, followed by triangular; circular(4,4) has the worst performance. A data rate of 1.515 Gbit/s is successfully achieved by circular(7,1) employing a red chip LED over 0.5 m indoor free space transmission below a BER threshold of3.8 × 10^(-3). Compared with circular(4,4), the traditional 8-QAM constellation, circular(7,1) provides a wider dynamic range of signal vpp, a higher data rate, and a longer transmission distance. To the best of our knowledge,this is the first investigation into the performance differences of special-shaped 8-QAM constellations in a highspeed, single-carrier VLC system, and the results comprehensively demonstrate that circular(7,1) is the optimal option.

Seismic behavior experimental study of frame joints with special-shaped column and dispersed steel bar beam

To overcome the problem that steel bars are put too close at a flame joint with special-shaped beam and column,mechanical performance of three groups of six RC flame joints with special-shaped(L,T and+)column and dispersed-steel bars-beam on the top floor under cyclic loads were studied.Experimental comparison was conducted between special-shaped(L,T and+)column and normal beams.The cracking load,yielding load,ultimate bearing capacity,failure patterns,and hysteretic properties at joint core area were investigated.The seismic behaviors of the joints with different proportions of dispersed-steelbar beams were analyzed.The results of experimental analysis indicate that the mechanical and seismic behaviors of frame joints with T-shaped and+-shaped column are nearly not changed when suitable proportion steel bars are dispersed to flange plane.Stiffness degeneration of flame joint with L-shaped column is rather serious due to concrete damage stiffness.Theoretical result indicates that distributing area of the dispersed steel-bar beams in the flange plate should be strictly controlled to avoid anchor destroy.

双工位针刺机器人系统设计

针对单工位针刺成型系统中人和机器无法高效协同生产,预制体生产效率较低;现有的直线型双工位针刺机器人设备需要2个外部回转轴带动双工位参与织物针刺,系统编程难度较高,且工位切换时需要占据的空间大的问题。提出一种混合切换双工位针刺机器人系统,并开展了双工位针刺成形系统的机械结构设计、异型预制体模具和针刺工艺设计、控制系统设计、运动仿真以及预制体制备的实验验证。结果表明:系统成功实现了大尺寸异型曲面预制体的高效针刺成形,直线/旋转混合切换的双工位使得实现预制体的自动换装的同时又能保证系统空间占用量小;双工位中只有针刺工位上的外部回转轴与6关节机械臂联动,系统较为简单,编程方便;同时提高了数控回转工作台的承载力且将针刺末端执行器的布针数量增加至25针,满足了大尺寸预制体的针刺成形,并使得针刺成形效率直接提高2倍。本文系统可应用于批量化制备大尺寸异型曲面复材预制体。

异形孔筒形锻件成形表面不平整度分析及验证

针对异形孔筒形锻件成形过程中金属在反向流动中流速不均匀导致的锻件上表面产生不平整缺陷的问题,以椭圆孔筒形锻件为例,采用数值模拟与试验相结合的手段,探究了锻件上表面不平整现象的成因。分别从一维、二维、三维建立了异形孔筒形锻件上表面不平整度的评判准则,进一步揭示了成形工艺参数对异形孔筒形锻件上表面不平整度的影响规律。结果表明:异形孔筒形锻件上表面不平整度随模具预热温度的升高而降低,随坯料始锻温度的升高而增大,始锻温度比模具预热温度对上表面不平整度的影响更大;提高成形速度可以降低金属的流动阻力,减小坯料的温降,改善坯料变形和温度分布的均匀性,从而降低异形孔筒形锻件上表面的不平整度;异形孔筒形锻件上表面不平整度还受椭圆孔短长轴比值的影响,凸模横截面积恒定时,随短长轴比值增大,不平整度评价指标均呈下降趋势;凸模短轴值恒定,长轴值超过锻件外径的2/3时,随短长轴比值增大,不平整度评价指标呈现先增大后减小的趋势,长轴值小于锻件外径的2/3时,不平整度评价指标随短长轴比值增大呈现下降趋势。

铰接方钢管组合异形柱框架抗震性能研究

为解决村镇住宅体系存在的装配式程度及标准化程度较低、现场焊接工作繁多、室内建筑面积浪费等问题,提出了一种铰接方钢管组合异形柱框架体系。该体系中异形柱采用3根空钢管通过钢板与加劲肋组合而成的L形柱,梁柱节点为腹板螺栓连接的铰接节点。通过拟静力试验对该体系的抗震性能进行研究。研究结果表明:相比于铰接钢管混凝土组合异形柱,铰接空钢管组合异形柱框架体系先于梁端出现转角,最后破坏模式为柱脚破坏,具有更优良的抗震耗能和更缓慢的强度与刚度退化,并通过对比刚接节点和铰接节点的骨架曲线,发现节点刚接程度对结构整体的抗侧刚度影响较大。

分段式排风系统异形构件阻力特性分析及优化

铝冷轧过程产生大量油雾,危害工人健康、破坏厂房环境,分段式排风系统虽可高效捕集油雾,但因含阻力特性未知的异形构件,导致系统风量无法精确按需分配。本文针对分段式排风系统中的环吸式排风罩和缝吸式半密闭罩,通过数值模拟方法研究其阻力特性,并进行减阻优化。研究发现,影响环吸式排风罩和缝吸式半密闭罩局部阻力系数的关键因素为进出口面积比,且二者呈指数关系;针对2种构件中涡产生的主要位置,采用结构优化的方式使阻力分别降低了28.6%和22.1%。本文可为铝冷轧排风系统管路设计提供参考。

冻融循环对十字形型钢混凝土柱轴压性能影响分析

为探究十字形型钢混凝土(SRC)柱经冻融作用后力学性能的演变,考虑混凝土强度、配筋率及长细比三个影响因素,采用ABAQUS软件对十字形SRC柱进行冻融和压缩模拟研究,对比分析冻融循环对十字形SRC柱荷载-应变曲线及承载力退化规律的影响,并归纳总结其承载力退化系数表达式.结果表明:SRC试件极限承载力与冻融循环次数呈负相关趋势,冻融循环导致混凝土劣化,使构件轴压承载能力降低,100次冻融循环后,SRC柱的极限承载力最大下降8.48%;而构件轴压承载能力与配筋率呈正相关趋势,因此适当提高混凝土强度及配筋率可有效抵御构件的冻融损伤;此外,极限承载力与长细比成反比,长细比过大,构件易发生弯曲失稳破坏;所提出轴压承载力退化系数计算值与模拟值吻合度较好.

窄翼缘异形柱-波纹钢板剪力墙体系的抗震性能

针对钢结构住宅凸梁、凸柱和抗侧刚度不足的问题,提出一种新型窄翼缘异形柱-波纹钢板剪力墙体系;通过与传统H形钢柱-平钢板剪力墙体系进行对比,确定内嵌波纹钢板布置方式,采用ABAQUS软件建立所提出体系的有限元模型,对所提出体系的抗震性能进行分析,探讨外部框架截面形式与布置方式、波纹钢板厚度与剪跨比等对所提出体系的抗侧承载力、耗能能力和塑性变形能力的影响。结果表明:所提出的体系具有较大的抗侧承载力和较强的耗能能力、塑性变形能力,极限抗侧承载力为设计值的1.73倍,具备一定的安全储备;横向布置的波纹钢板能有效减小其作用于框架梁柱的荷载;采用十字形异形柱使所提出的体系有更强的塑性变形能力;所提出体系中的异形柱偏肢宜沿剪力墙面内方向布置,内嵌波纹钢板厚度宜取为3~5 mm,剪跨比宜控制在1.25左右。

超高层异形爬架综合施工技术研究

杭州西站TOD项目超高层建筑外立面轮廓线先外扩再内收,为此采用了异形爬架,通过两阶段垂直爬升和内收俯爬进行作业。本研究介绍了异形爬架的主要特点,明确爬架断面分区、机位布置,分析解决爬升流程技术要点和难点。给出爬架附着支座在悬挑板上的计算校核;结合爬架外扩内收的结构变形,通过定型化防护网搭接解决扇形空隙防护区域,并设置防倾构造保障架体安全,可为同类工程施工提供参考。

小型高效气动立式预混装置异形桨叶工作特性研究

为解决某交联剂在预混时溶解慢、易挥发、对操作人员危害大等问题,开发了一套采用单轴异形桨叶的可远程控制的小型高效立式气动预混装置。通过有限元方法计算了四种搅拌叶片的流场特性,分析了异形桨叶和其他三种常用桨叶的总体流型、速度流线分布。结果表明,在预混转速为45 rpm时,异形叶片可实现交联剂径向流动,使旋转中心的交联剂充分混合,有效防止中心死区的出现,展现出良好的预混性能,预混时间由人工预混的6 h缩短为2 h,乙腈溶液挥发量减少了60.8%,有效解决了交联剂挥发和挂壁析出问题,提高了交联剂的预混效率。

“两墙合一”深基坑工程设计与技术创新

北京CBD核心区某项目基坑深度36m,因受场地空间限制,采用“两墙合一”+内支撑支护体系,在实现基坑挡土、止水功能的同时完成了地下结构外墙施工。为提高工程质量和施工效率,针对地连墙与主体结构的连接、槽段接头处理方式、有限空间导墙结合近接建筑物预换撑等方面进行了技术创新,取得了较好的工程效果,可供类似工程参考。

基于锥形回转体多孔毛坯的异型面结构加工工艺研究

为研究在锥形回转体多孔毛坯基础上加工出异型面结构,论文首先对产品进行了工艺分析,通过基础试验,对比了铣削加工、电火花加工、电解加工后试片的表面形貌以及渗透性。在此基础上,制定了产品的加工工艺,通过流量试验,验证了工艺方法的有效性,为该类产品的加工提供了有益的参考。