铁塔典型构造杆件承载力试验研究

依据模型塔和真型塔试验的结果 ,分析了国内外相关文献计算输电铁塔典型构造中角钢压杆承载力的差异 ,并针对平行轴支撑斜材破坏内力低于计算承载力的问题 ,推荐了关于角钢平行轴的长细比修正公式。使用我国新实施的DL/T5 15 4- 2 0 0 2《架空送电线路铁塔结构设计规定》计算大长细比杆件时 ,可适当提高杆件承载力。     

大长径比细长颗粒的沉降实验和曳力系数的关联

引　言对球状颗粒的研究已取得丰硕的成果[1] ,但对其他形状颗粒的研究则较少 ,特别是细长颗粒 .形状的特殊性使细长颗粒的曳力系数与球状颗粒明显不同 ,仅有的文献[2～ 4] 将研究重点放在静止液体中颗粒沉降时的取向和终端沉降速度 ,且一般采用球形度表示曳力系数 ,颗粒长径比     

苏州工业园区国际大厦转换层设计

苏州工业园区国际大厦转换层就其双向大跨度、下部空间高度及上部负荷而言 ,尚不多见。设计提出了一种新型转换结构形式———“双向预应力转换梁体系”和支承细长柱临界荷载的计算方法。另外 ,对大楼的抗震概念设计、空间电算分析及试验分析作了介绍     

钢管超高强混凝土长柱及偏压柱的性能与极限承载能力的研究

本文报导了钢管超高强混凝土长柱和偏压柱的试验研究工作。长柱试验研究结果表明,钢管超高强混凝土长柱的承载能力和极限纵向变形率随长细比Ｌｅ／ Ｄ的增大而下降,在所研究的 Ｌｅ／ Ｄ范围内,所有的钢管超高强混凝土长柱都有一定的延性,但延性随Ｌｅ／Ｄ的增大而降低。普通钢管混凝土长柱的承载能力考虑长细比影响的折减系数计算公式也适用于钢管超高强混凝土长柱。偏压柱试验研究结果表明,在偏心率为０．２２～０．６５范围内,加载后所有偏压柱试件横向无明显的外形变化。在相同的长细比下,随着偏心率的增加,试件的承载能力降低,极限纵向变形率降低,但总体来说,偏压短柱的纵向变形率比轴压短柱的极限应变要大一些。在相同的偏心率下,长细比越大,试件的承载能力和纵向变形率也越低。钢管超高强混凝土耐偏压能力等于或优于普通钢管混凝土偏压柱。经过适当修正的普通钢管混凝土偏心率折减系数可以用于钢管超高强混凝土偏压柱承载能力计算。     

Generalized differential quadrature analysis of MHD mixed convective motion of Casson fluids past an isothermal irregular slender geometry via Cattaneo–Christov's approach

Classical Fourier's theory is well-known in continuum physics and thermal sciences. However, the primary drawback of this law is that it contradicts the principle of causality. To explore the thermal relaxation time characteristic, Cattaneo–Christov's theory is adopted thermally. In this regard, the features of magnetohydrodynamic (MHD) mixed convective flows of Casson fluids over an impermeable irregular sheet are revealed numerically. In addition, the resulting system of partial differential equations is altered via practical transformations into nonlinear ordinary differential equations. An advanced numerical algorithm is developed in this respect to get higher approximations for temperature and velocity fields, as well as their corresponding wall gradients. For validating our numerical code, the current outcomes are compared with the available literature results. Moreover, it is revealed that the velocity field is more prominent in the suction flow situation as compared with the injection flow case. It is also found that the Casson fluid is hastened in the case of lower yield stress. Larger values of thermal relaxation parameters create a lessening trend in the temperature distribution and its related boundary layer breadth.     

Predicting shear strength of slender beams without reinforcement using hybrid gradient boosting trees and optimization algorithms

Shear failure of slender reinforced concrete beams without stirrups has surely been a complicated occurrence that has proven challenging to adequately understand. The primary purpose of this work is to develop machine learning models capable of reliably predicting the shear strength of non-shear-reinforced slender beams (SB). A database encompassing 1118 experimental findings from the relevant literature was compiled, containing eight distinct factors. Gradient Boosting (GB) technique was developed and evaluated in combination with three different optimization algorithms, namely Particle Swarm Optimization (PSO), Random Annealing Optimization (RA), and Simulated Annealing Optimization (SA). The findings suggested that GB-SA could deliver strong prediction results and effectively generalizes the connection between the input and output variables. Shap values and two-dimensional PDP analysis were then carried out. Engineers may use the findings in this work to define beam's geometrical components and material used to achieve the desired shear strength of SB without reinforcement.     

Slender reinforced concrete shear walls with high-strength concrete boundary elements

Reinforced concrete structural walls are commonly used for resisting lateral forces in buildings. Owing to the advancements in the field of concrete materials over the past few decades, concrete mixes of high compressive strength, commonly referred to as high-strength concrete (HSC), have been developed. In this study, the effects of strategic placement of HSC on the performance of slender walls were examined. The finite-element model of a conventional normal-strength concrete (NSC) prototype wall was validated using test data available in extant studies. HSC was incorporated in the boundary elements of the wall to compare its performance with that of the conventional wall at different axial loads. Potential reductions in the reinforcement area and size of the boundary elements were investigated. The HSC wall exhibited improved strength and stiffness, and thereby, allowed reduction in the longitudinal reinforcement area and size of the boundary elements for the same strength of the conventional wall. Cold joints resulting from dissimilar concrete pours in the web and boundary elements of the HSC wall were modeled and their impact on behavior of the wall was examined.     

细长体倾斜入水时的非平衡态超空泡气液两相流研究

采用高速摄影技术观察高速细长体倾斜入水后超空泡气液两相流形态发展变化过程并对其结果进行研究。分析48mm长的细长体在50m／s左右的入水速度工况下,分别以几种不同入射角度进入水中后相关的流体动力学特性过程。实验结果表明,当细长体倾斜入水时,其与水自由面接触产生的力矩改变了细长体的初始运动方向,使其偏转并产生有多重褶皱的非规则空泡体,细长体尾部也更容易在入水时与产生的空泡边界接触而打断超空泡,致使部分超空泡留在近自由面处。根据速度拟合曲线,验证了细长体倾斜入水情况下依旧有超空泡减阻作用。     

超细长轴车削加工工艺

文章分析了在切削力、重力和顸尖顸紧力的作用下，超细长轴车削加工中常见的工件缺陷的产生原因。在车削中采用各种车削装置：如三只支承块跟刀架、弹性活络顸针、垫块、托架支承等，采用反向进给车削，配合以最佳的刀具几何参数、切削用量、等一系列有效措施。提高了超细长轴的刚性，满足了加工要求。该方法操作简单，加工精度高，且大大提高了工效。     

基于芯轴交换的圆柱齿轮复动挤压成形

根据对圆柱齿轮成形特点的分析，介绍了基于芯轴交换的圆柱齿轮复动成形原理，成形过程，成形设备与模具结构。