装配式圆钢管约束混凝土柱的轴压性能

为了研究钢套管及套筒连接装配式圆钢管约束混凝土柱轴压性能，基于试验研究结果，对钢套管及套筒连接装配式圆钢管约束混凝土柱轴压性能进行了有限元分析. 首先通过有限元建立了现浇式和装配式圆钢管约束混凝土柱模型；然后从承载力-平均纵向应变关系曲线、钢管应力、钢筋应力和混凝土应力方面对比了现浇式与装配式柱的轴压性能；其次分析了装配式柱变形形态及受力机理；最后提出了装配式柱轴压承载力计算方法. 研究结果表明:与现浇式柱相比，装配式柱也具有良好的轴压性能和延性性能，钢管及钢套管对核心混凝土的约束作用更强，轴压承载力提高幅度为1.94%～6.17%；增加钢管厚度对提高装配式圆钢管约束混凝土柱轴压承载力最有效，提高幅度达59.15%，增加箍筋间距对其轴压承载力影响较小，减小幅度为2.91%；钢管纵向应力在靠近钢套管与钢管连接处较大，钢管环向应力在钢管通缝上、下附近区域较大，在钢套管装配处也较大；所提装配式柱轴压承载力公式计算值（N_uc）与有限元值（N_uf）、试验值（N_ut）的比值均值分别为0.964、1.014，方差分别为0.003 5、0.002 9.      

熔融石英砂动力特性动三轴试验

为探究振动荷载作用下熔融石英砂液化破坏过程中动变形和动强度变化规律, 促进透明土技术在岩土工程动力特性可视化模型试验中的推广和应用, 对构成透明砂土骨架结构的典型粒径(0.5~1.0 mm)熔融石英砂开展饱和试样动三轴试验; 研究了不同围压、加载频率和动应力比等试验条件下熔融石英砂试样的累积轴向应变、动孔压发展模式、动应力衰减、动弹性模量和阻尼比的变化规律, 并将试验结果与相同级配的标准砂进行了对比。分析结果表明: 熔融石英砂累积轴向应变随动应力比的增大呈现出由稳定型向破坏型转变的趋势, 加载频率为0.5~1.5 Hz时, 临界动应力比为0.150~0.175, 小于标准砂的0.200~0.225;升高围压、增大动应力比、降低加载频率会加快试样塑性应变累积, 缩短液化破坏时间; 熔融石英砂孔压发展模式随围压增大逐渐由Seed孔压模型向指数型过渡, 增大加载动应力会加剧液化破坏后孔压的振动幅度; 相同动应力比下, 熔融石英砂与标准砂的动应力与动应变呈现线性相关, 在围压大于200 kPa时, 二者动应力衰减幅度随围压的增大而逐渐减小; 熔融石英砂的动弹性模量和阻尼比表现为线性关系, 动弹性模量随动应变的增大呈现出双曲线型减小的趋势, 并随围压的增大而增大; 阻尼比随动应变的增加先增大后基本稳定在0.22, 发展曲线受围压影响较小。      

Mechanical properties of perfect and defective zigzag single-walled carbon nanotubes under axial compression

Axial buckling behavior of perfect and defective zigzag single-walled carbon nanotubes(SWCNTs) is studied by molecular dynamics(MD) simulations.Different effects of three typical categories of defect on the axial buckling properties of SWCNTs are investigated.MD simulation results show that the buckling behavior of defective tubes is quite different from the perfect tube.The critical buckling load of zigzag SWCNTs is significantly reduced with different defect appeared in the tube wall,and the effective elastic modulus are also slightly but distinguishingly influenced by individual defect.It is revealed that an Stone-Thrower-Wales defect could induce greater decrease of the rigidity a single vacancy defect or a double vacancies one.The harmful effects of defects do not depend simply on the size of the defective area,but related strongly to the buckling modes of the defective SWCNTs which specifically differ from each other due to the different defect structures.     

圆钢管H型钢再生混凝土短柱的轴压承载力分析

为了研究圆钢管H型钢再生混凝土短柱轴压力学性能，对此类构件轴压承载力计算公式进行了理论推导，基于极限分析法，运用双剪统一强度理论，并依据H型钢和钢管对核心区再生混凝土约束效果的不同，分别计算H型钢约束区再生混凝土和钢管约束区再生混凝土承载力，提出一套圆钢管H型钢再生混凝土短柱轴压承载力计算公式，考虑了钢管内径厚比、套箍系数、H型钢配钢指标以及再生粗骨料取代率对短柱轴压承载力的影响, 同时也适用于无H型钢的圆钢管再生混凝土短柱轴压承载力计算. 将推导得到的钢管有效约束力代入承载力计算公式所得结果与相关试验结果对比误差在10%以内，吻合较好，验证了承载力计算公式的有效性和精确度.      

轴心受压方形截面钢管混凝土叠合柱耐火性能

为探讨轴心受压方形截面钢管混凝土叠合柱的耐火性能,对4根轴心受压方形截面钢管混凝土叠合柱进行了试验研究,并对火灾荷载比、截面含管率和截面边长等对耐火性能的影响进行了有限元分析.研究结果表明:当火灾荷载比减小、截面含管率和截面边长增大时,火灾作用下试件的轴向膨胀变形增大,轴向压缩变形减小;在相同的升温曲线和火灾时间作用下,截面边长增大时,柱内温度降低;含管率变化对柱内温度场影响较小.火灾荷载比、截面边长和长细比是影响轴心受压方形截面叠合柱耐火性能的主要因素;含管率、纵筋配筋率和材料强度变化对轴心受压方形截面叠合柱耐火性能的影响较小.      

纵向初应力作用下圆钢管混凝土轴压短柱受力机理

应用连续介质力学,确立钢管在纵向初应力作用下的圆钢管混凝土同心圆柱体钢管和混凝土受压时的计算模型,推导了初应力作用下的钢管混凝土组合弹性模量计算公式和组合应力-应变关系全曲线的表达式,分析了不同初应力系数下钢管混凝土加载过程中的钢管轴向应力-应变关系、环向应力-应变关系以及核心混凝土的轴向应力-应变关系、径向应力-应变关系的变化情况,探讨了初应力系数对钢管混凝土力学性能的影响。分析结果表明:随着钢管纵向初应力的增大,核心混凝土的纵向刚度、径向压应力、纵向强度与钢管环向拉应力也有所降低,而相应的钢管纵向压应力有所增加,套箍约束作用和极限承载力也有所降低,但对组合弹性模量影响不大。     

非稳态载荷对二维轮轨纯滚动接触应力和变形的影响

为了揭示轮轨波状表面与非稳态载荷的内在联系,利用有限元法,建立了二维弹塑性轮轨纯滚动接触计算模型,分析法向接触载荷波动值对钢轨残余应力、应变和变形的影响。模型中材料本构采用考虑棘轮效应的Jiang-Sehitoglu模型,非稳态仅考虑法向接触载荷的简谐变化,用弹塑性无限半空间表面上重复移动赫兹法向压力分布模拟反复纯滚动接触过程。发现非稳态法向接触载荷作用下产生同样波长的波状接触表面;随滚动次数的增加,残余应力增大,但很快趋于稳定,而残余应变也增大,但增大速率衰减;载荷波动值越大,波谷和波峰处的纵向残余应力越大,波谷处的轴向残余应力、残余剪应变和表面纵向位移越大,而波峰处的轴向残余应力、残余剪应变和表面纵向位移越小,波深越大。     

A new model for simulation of cold roll-forming of tubes by using spline finite strip method

A new model,called object model,for the simulation of cold roll-forming of tubes is presented.The model inherits the advantages of old models and is the embodiment of forming process that the strip is rolled step by step from feed rollers to last rolling pass.The elastic-plastic large deformation spline finite strip method based on updated Lagrangian method has been developed by improving the stiffness and transition matrix.Combined theory formulas and new analytical model,the forming process of a tube has ...     

Multi-scale simulation for the forming of a heavy vessel head considering the evolution of defects and microstructure

The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production, due to the huge size of the ingots from which the head is manufactured, coarse grains and voids are common defects existing in the material. Furthermore, cracks may appear in the forming process. It is highly demanded that the forming process must be properly designed with suitable parameters to compact the voids, to refine and homogenize the grains and to avoid cracks. Therefore, the research on the evolution of internal voids, grain size and cracks is very important to determine the forming process of huge components. SA508-3 steel is the material to manufacture the head of pressure vessel in the nuclear island. In the previous studies, we have separately built models to evaluate the evolution of internal voids, grain size and cracks during the hot forming process for SA508-3 steel. This study integrates the models for multi-scale simulation of the forging process of the head of nuclear pressure vessel in order to control the quality of the forgings. Through the software development, the models are integrated with a commercial finite element code DEFORM. Then, the extended forging and final forging processes of the head are investigated, and some appropriate deformation parameters are recommended.     

基于桁梁实桥试验的钢管混凝土界面传力机制

为分析钢管混凝土桁梁桥的承载性能和钢-混凝土组合作用机理,进行了桁梁上、下弦钢管混凝土界面传力行为实桥试验和全桥板壳-实体有限元参数分析;以主跨71 m的简支半穿式钢桁梁桥为依托,沿其上、下弦杆节间长度范围内共布设102个应变测点,测试并分析了加载车作用下钢管轴向应变分布和钢-混凝土界面传力特征;采用ABAQUS软件建立了试验桥板壳-实体有限元模型,经实测挠度与应变数据验证模型的可靠性后,进行了界面连接状态、界面抗剪刚度、钢管厚度、管内混凝土强度等对钢管混凝土界面传力性能的参数影响分析。分析结果表明:钢管轴向应变分布规律可反映钢管混凝土界面传力的基本特征;钢管混凝土桁架上、下弦杆节点区域均出现界面剪力不均匀分布现象,钢-混凝土界面有效传力范围内钢管轴向应变呈负指数函数分布,其他区域钢管轴向应变保持不变;完全脱黏的钢管混凝土桁架弦杆的钢管轴向应变在节点一定范围内呈二次抛物线函数分布;钢管轴向应变因界面连接状态所表现出的不同应变分布规律和剪力传递长度可用于评价钢管混凝土组合作用强弱和界面工作状态;桁架弦杆的剪力传递长度随钢管厚度和管内混凝土强度的增加而增大,钢管厚度的影响更显著;在钢管混凝土桁架弦杆内设置抗剪连接件可缩短剪力传递长度。      

Preliminary design of pressure torque separation sensor for drilling bit

The working state of drilling bit is a critical issue in the drilling process. The preliminary design of pressure and torque separation sensor for drilling bit is expatiated herein. The sensor unit is composed of the elastic unit and the Wheatstone full bridge. Under composited load, the theoretical analysis about separating the axial force and torque of drilling bit is discussed firstly. The separation has been achieved by using the Wheatstone full bridge pasted onto the elastic unit. Then the transversal and axial strains distribution of elastic unit has been calculated and analyzed by ANSYS software, when the bit is under axial force and torque. Based on the calculation and analysis results, the sensitivity and accuracy of the sensor’s whole measurement chain can be reckoned. Meanwhile, the calculation and analysis results can also give good suggestion about the positions where the strains gauge should be pasted. Finally, it has been proved that this solution can meet the preset requirements very well.     

深埋隧洞突发性高压涌水预测及对策研究

文中介绍了几种典型高压涌水形成的地质条件,为了防止在隧洞掘进过程中出现突发性高压涌水,采用宏观地质预报、微观地质预报及探地雷达预报提前预测可能存在高压涌水的位置、水量和水压等,并且对一些富含高压水构造提出了一些相应的施工对策。     

Numerical analysis of unconventional forging process of hollowed shaft from Ti-6Al-4V alloy

This paper presents theoretical analysis of unconventional forging process of hollowed shaft from Ti-6Al-4V alloy in a three-slide forging press. This method in comparison with other metal forming methods allows for obtaining of hollowed products. The designed process is verified theoretically by means of numerical simulations based on finite element method with assumption of 3D state of strain. The following factors are considered in the analysis: material flow kinematics, strain distribution, temperature distribution and force of process. On the basis of results, it is stated that the application of designed technology allows for obtaining of a product of assumed quality. A comparison is made between material consumption in analyzed process and material consumption in typical metal forming methods, also in used at present technology of shaft manufacturing by machining only. It is stated that the application of forging in the three-slide forging press allows for a considerable decrease of manufacturing costs due to material savings and decrease of labor consumption of operations at finishing.     

方中空不锈钢管混凝土短柱轴压承载力性能

为促进方中空不锈钢管混凝土构件在土木工程中的应用，以不锈钢外管厚度和混凝土强度为变量的6组试件为研究对象，首先，进行轴压试验，得到了不同试件在轴压荷载作用下的破坏模式、荷载-位移曲线、荷载-应变曲线，并进一步分析了不锈钢方管宽厚比、核心混凝土强度以及不锈钢方管约束效应系数对方中空不锈钢管混凝土短柱极限承载力的影响；然后，初步讨论了倒角对强度和延性的影响，提出了避免内管先于外管屈曲的最小厚度计算方法；最后，基于试验结果以及已有文献数据，采用拟合方法推导了方中空不锈钢管混凝土短柱的抗压承载力计算式，并与已有文献的简化模型及国外主要规范的计算结果进行对比.研究结果表明：试件宽厚比由34.9降至20.9，极限承载力的提升率平均为98.5%，核心混凝土强度由C40提升至C60时，试件极限承载力的提升率平均为7.3%；短柱的轴压极限承载力随约束效应系数近似呈线性增加，约束效应系数ξ越大，短柱的承载力越高；本文得到的计算式可以较好地预测方中空不锈钢管混凝土短柱的轴压承载力.     

钢管混凝土叠合柱高墩的概率抗震能力模型

为评估钢管混凝土叠合柱高墩的抗震性能,以曲率为性能指标,采用拉丁超立方抽样方法,对截面样本偏心受压进行了全过程数值模拟.根据破坏形态,将叠合柱截面损伤划分为轻微损伤、中等损伤、严重损伤和完全损伤4种极限状态并进行量化.将曲率指标的统计特征值与轴力进行三次多项式回归分析,建立了以轴力为变量的钢管混凝土叠合柱高墩的概率抗震能力模型.结果表明:以外围箍筋约束混凝土破坏为分界,叠合柱分别表现出钢筋混凝土和钢管混凝土的破坏特征;不同轴力作用下4种极限损伤状态的曲率指标均服从对数正态分布,其均值随轴力增大而减小.      

Experimental Study on the Compressive Behavior of CFRP/ECCs

In this study, nine square concrete columns, including six CFRP/ECCs and three plain concrete control specimen columns, were prepared. The CFRP tubes with fibers oriented in the hoop direction were manufactured with 10, 20, or 40 mm rounded corner radii at vertical edges. A 100 mm overlap in the direction of fibers was provided to ensure a proper bond. Uniaxial compression tests were conducted to investigate the compressive behaviors including the axial strength, stress-strain response, and ductility. It is evident that the CFRP tube confinement can improve the compressive behavior of concrete core, in terms of axial compressive strength or axial deformability. Based on the experimental results and some existing test database attained by other researchers, a design-oriented model is developed. The predictions of the model for CFRP/ECCs show good agreement with test results.     

基于试验的型材冷弯成形线型特征研究

船舶型材冷弯成形加工过程中,逐段进给弯曲加工方式下塑性变形区的成形线型对于整体加工质量和效率的提高具有重要意义.针对成形线型的特点,采用正交多项式最小二乘拟合方法,分别拟合成形线型中的直线和曲线部分,分析两部分线型的特征.进一步,采用椭圆和抛物线逼近线型的曲线段,分析塑性变形区的线型特征,取得了有意义的结论.     

关于我国发展真空管道高速交通的思考

论述了我国发展真空管道高速交通的必要性和可行性．就管道压强、遮挡系数及其关键技术等基本问题展开讨论．重点论述我国发展真空管道高速交通的战略方针和技术方案．提出采用高温超导磁浮导向，同步线性电机牵引和低压强管道所组成的系统．建议立即开始研究试验，以期能于2030年前实现600—1000km／h超高速真空管道磁浮列车的商业运行．     

矩形钢管高强混凝土框架抗震性能分析

为研究地震作用下矩形钢管高强混凝土框架的破坏机理和抗震性能,进行了单跨两层矩形钢管高强混凝土框架低周反复荷载试验和有限元分析. 考察结构试件在试验过程中塑性铰出现的位置、顺序及塑性发展程度,研究其破坏机制和破坏模式. 研究结构滞回曲线与骨架曲线,分析其承载能力、变形能力、耗能能力以及强度和刚度退化情况. 在此基础上,采用有限元软件Perform-3D对矩形钢管高强混凝土框架试件进行参数分析,研究了轴压比、钢材屈服强度及静力弹塑性分析水平侧向力加载模式等对结构抗震性能影响. 结果表明:矩形钢管高强混凝土框架试件呈梁铰破坏形态,并具有承载能力高、变形能力和耗能能力强的特点. 试件平均峰值荷载较屈服荷载提高了1.68倍;顶层和底层最大层间位移角分别为1/30和1/27,分别超过了规范规定限值的66.7%和85.2%. 延性系数分别超出了规定限值的58.5%和60.0%;轴压比对结构抗震性能影响显著. 当轴压比大于0.6时,结构承载能力与变形能力明显降低;水平侧向力加载模式对结构承载能力影响大. 均匀加载模式下结构承载能力最大,顶点加载模式下最小,倒三角形加载模式居于二者之间. 研究成果可为矩形钢管高强混凝土框架结构抗震设计提供参考.      

Mechanical Behaviors of Submerged Floating Tunnel under Current Effect

Introduction Submerged floating tunnel ( SFT) provides acomplete new option for crossing of waterways, andcan connect both lands and channels where appropri-ate[1-5]. Being a structure not buried deeply in theground, but suspended in a certain depth below…