Hysteretic behavior of special shaped columns composed of steel and reinforced concrete(SRC)

This paper describes a series of experimental investigations on seventeen specimens of steel reinforced concrete special shaped(SRCSS) columns under low cyclic reversed loading using parallel crosshead equipment. Nine T-shaped SRC columns, four L-shaped SRC columns and four +-shaped SRC columns were tested to examine the effects of shape steel confi guration, loading angle, axial compressive ratio and shear-span ratio on the behavior(strength, stiffness, energy dissipation, ductility, etc.) of SRCSS column specimens. The failure modes and hysteretic performance of all the specimens were obtained in the tests. Test results demonstrate that the shear-span ratio is the main parameter affecting the failure modes of SRCSS columns. The specimens with small shear-span ratio are prone to shear failure, and the primary failure planes in SRCSS columns are parallel to the loading direction. As a result, there is a symmetry between positive and negative loading directions in the hysteretic curves of the SRCSS columns. The majority of displacement ductility coeffi cients for all the specimens are over 3.0, so that the SRCSS columns demonstrate a better deformation capacity. In addition, the equivalent viscous damping coeffi cients of all the specimens are greater than 0.2, indicating that the seismic behavior of SRCSS columns is adequate. Finally, the superposition theory was used to calculate the limits of axial compressive ratio for the specimens, and it is found that the test axial compressive ratio is close to or smaller than the calculated axial compressive ratio limit.

Calibration of split Hopkinson pressure bar system with special shape striker

In order to present basic guidance for system calibration of split Hopkinson pressure bar(SHPB) with the special shape striker,wave characteristics and dynamic responses of SHPB under striker impact were analyzed.Stress generated by the special shape striker tends to have a half-sine waveform and has little wave dispersion during its propagation.Impact velocities of the special shape striker and peak values of generated stress still have linear relation but with a different coefficient from that of cylindrical strikers.From stress histories on the surfaces of the input bar impacted by the special shape striker off-axially and obliquely,it is found that the misalignment impacts usually trigger wave distortion and amplitude decrease,which can be used to identify the poor system adjustment.Finally,the system calibration of SHPB with the special shape striker can be classified into four steps:system adjustment,wave distortion identification,measurement calibration and transmission calibration,where the measurement calibration factor and transmission calibration factor are elaborated and redefined.

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.

Seismic Behavior of Specially Shaped Column Joints with X-Shaped Reinforcement

To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement,two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading,which imitated low to moderate earthquake force.The seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity,displacement,ductility,hysteretic curve,stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core region.With the damage estimation model,the accumulated damage was analyzed.The shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple form.The test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior,ductility and hysteretic characteristic.All specimens were damaged with gradual stiffness degeneration.In addition,X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated damage.The good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering applications.The test value is higher than the calculated value,which indicates that the formula is safe for the design of specially shaped column joints.

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.

Interfacial stress transfer behavior in a specially-shaped fiber/matrix pullout test

Specially designed fibers are widely used in engineering practice because the specially-designed shape can help to improve the bonding strength of the fiber and the interface. Studied in this paper is the interfacial shear stress transfer behavior on both sides of the specially designed fiber when it is being pulled out; in which automatic analysis of three-dimensional photoelasticity is employed and the finite element method is adopted. The results show that the stress transfer occurs mainly in the region near the fiber＇s embedded end where the stress reaches its critical point, leading to debonding of the interface. Before debonding, as the pullout loading increases, the peak value of shear stress transfers along the fiber from the embedded end to the interior of the matrix, and then stops at the hooked part of the fiber because of its impediment. When the interface begins to debond as the load increases, the shear stress can be transferred to the hooked part.

Frame property of unequal storey height with specially shaped columns under cyclic loading

A 1/3-scale reinfored concrete(RC) frame of unequal storey height with specially shaped columns was tested under low frequency cyclic loading.The damage characteristic,bearing capacity,deformation capacity and ductility were analyzed.The restoring force model of the frame was obtained based on the study of the hysteresis curve measured in experiment,and the stiffness degeneration characteristics of every storey of the frame were analyzed.Finally the accumulated damage was analyzed with the damage assessment model.It is shown that the seismic behavior of this frame of unequal storey height with specially shaped columns is generally good,but the bottom of first floor column is a weak part,which should be paid more attention in design,and the restoring force model derived from this experiment can be seen as a valuable guide for design and non-linear finite element analysis for this kind of structure.

Improved design of special boundary elements for T-shaped reinforced concrete walls

This study examines the design provisions of the Chinese GB 50011-2010 code for seismic design of buildings for the special boundary elements of T-shaped reinforced concrete walls and proposes an improved design method. Comparison of the design provisions of the GB 50011-2010 code and those of the American code ACI 318-14 indicates a possible deficiency in the T-shaped wall design provisions in GB 50011-2010. A case study of a typical T-shaped wall designed in accordance with GB 50011-2010 also indicates the insufficient extent of the boundary element at the non-flange end and overly conservative design of the flange end boundary element. Improved designs for special boundary elements ofT-shaped walls are developed using a displacement-based method. The proposed design formulas produce a longer boundary element at the non-flange end and a shorter boundary element at the flange end, relative to those of the GB 50011-2010 provisions. Extensive numerical analysis indicates that T-shaped walls designed using the proposed formulas develop inelastic drift of 0.01 for both cases of the flange in compression and in tension.

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.

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.

Catalyst Pellet Shape Specialization for Ethylene Acetoxidation to Vinyl Acetate

ＣａｔａｌｙｓｔＰｅｌｌｅｔＳｈａｐｅＳｐｅｃｉａｌｉｚａｔｉｏｎｆｏｒＥｔｈｙｌｅｎｅＡｃｅｔｏｘｉｄａｔｉｏｎｔｏＶｉｎｙｌＡｃｅｔａｔｅＪｕＭｅｎｇｊｏｅ；ＸｕＫｅ；ＷａｎｇＳｈａｎｇｄｉ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｃａｌＥｎｇｉｎｅｅ...

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。

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。

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。

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。

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。

异形塔混合结构斜拉桥设计参数对成桥状态的影响研究

为研究异形塔混合结构斜拉桥相关设计参数对成桥状态的影响,进而支撑该类桥梁优化设计及施工质量控制,以某跨径组合为(2×30+2×60+2×30)m的异形塔混合结构斜拉桥为依托,建立空间有限元模型,研究主梁容重、主梁刚度、环塔刚度、拉索弹性模量、拉索初拉力、温度等参数对主梁线形、环塔线形、成桥索力的影响规律。结果表明:主梁容重、温度、拉索初拉力对成桥主梁线形的影响明显,其中,主梁容重对成桥主梁线形影响最大,其次为温度、拉索初拉力;温度、环塔刚度、拉索初拉力对环塔线形的影响明显,温度的影响最大,环塔刚度、拉索初拉力次之;拉索初拉力、温度对成桥索力的影响最为明显。