Analytical formulation of the elastic-plastic behaviour of bi-symmetrical steel shapes

This paper presents the analytical relationships of a non-linear model for the in-plane elastic-plastic analysis of bi-symmetrical steel shapes bent about one of their main axes. The basic variables are the cross-section global deformations, from which it is possible to evaluate the internal loads and the cross-section stiffness matrix components by means of simple expressions. Furthermore, the values of stresses and strains at any point of the cross-section may be determined, knowing the values of the internal loads, in the elastic and elastic-plastic domains. The effects of progressive yielding spreading, as well as those of material strain-hardening, are taken into account in the evaluation of the cross-section resistance capacity in the elastic-plastic domain. This analytical model represents an efficient, simple and accurate alternative to the elastic-plastic models based on numerical methods.     

Determination of the Nusselt versus Graetz correlation for heat transfer in channels of sinusoidal cross-section

Metallic catalytic converters are composed of monoliths through which pass hundreds or thousands of parallel channels. Their mode of manufacture is such that each channel has the cross-section of a sinusoidal curve closed off by a nearly straight edge. During the operation of such converters, heat generated at the channel walls is transferred to the gases flowing through the channels. To understand the overall heat transfer characteristics of the monolith, it is necessary to understand the heat transfer rate between the channel walls and the fluid contained within them. With the use of the computational fluid dynamics package FIDAP, a three-dimensional model of a single channel was used to determine the local Nusselt number (Nu) versus Graetz number (Gz) correlation for heat transfer between the fluid and the walls of the channel. Flow through the channel was laminar and developing from a flat velocity profile at the channel inlet to the fully developed flow towards the outlet. Three different models were developed which corresponded to sinusoid height to width aspect ratios of 5 : 2, 3 : 2, and 1:1, respectively. The Nu vs. Gz correlations for the straight edge, curved sinusoidal edge and entire perimeter were calculated and are reported.     

An empirical formula for L line X-ray production cross-section of elements from Ag to U for protons below 3.5 MeV

When computing element concentration from proton induced X-ray emission analysis, an important parameter is the X-ray production cross-section. There have been numerous experimental and theoretical works in this field. Nonetheless, although there is a simple analytical formula to compute K X-ray cross-sections, there is no such ones for the L lines. We present here analytical formulas for the cross-section of the three main X-ray lines L, L_β and L_γ based on experimental data. So far, nearly 3000 values of cross-sections for elements from Ag to U and proton energy ranging from 0.5 to 3.5 MeV have been collected from various references. This experimental data set has been fitted for each X-ray line with an exponential function depending on the proton energy and on the element atomic number. These fitted values have then been compared to the experimental data and with theoretical values obtained by the ECPSSR theory and Coster–Kronig fluorescence yields.     

Cross-section adjustment methods based on minimum variance unbiased estimation

On the basis of the minimum variance approach, the unified formulation for three types of the cross-section adjustment methods has been derived in a straightforward way without assuming the normal distribution. These methods are intended to minimize the variances of the predicted target core parameters, the adjusted cross-section set, and the calculated integral experimental values. The first and the second methods are found to be slightly different from the extended and the conventional cross-section adjustment methods based on the Bayesian approach with the normal distribution assumption, respectively. However, they become equivalent in some cases and results. The third method is a new method, which is necessary from the viewpoint of the symmetry of the formulation. In addition, it is verified by numerical calculations that the derived formulation gives the minimized variances as intended. The derivation procedure proposed in the present paper is potentially applicable to developing more sophisticated cross-section adjustment methods because of the less assumptions on the probability density function.     

Bending strength of hot-rolled elliptical hollow sections

The recent emergence of hot-rolled elliptical hollow sections (EHS) within the construction industry has attracted considerable interest from structural engineers and architects. Comprehensive structural design rules are now required to facilitate their wider application. This paper focuses on the bending strength of hot-rolled elliptical hollow sections; the results of detailed experimental and numerical studies are presented and structural design rules for EHS in bending about the major and minor axes are proposed. A total of 18 in-plane bending tests in three-point and four-point configurations have been performed. All tested specimens had an aspect ratio of two. Full moment-rotation and moment-curvature histories were derived, including into the post-ultimate range. The experimental results were replicated by means of non-linear numerical modelling. Following careful validation of the models, parametric studies were performed to assess the structural response of EHS over a wider range of aspect ratios (between one (CHS) and three) and cross-section slendernesses. For design, cross-section slenderness parameters have been proposed and a set of classification limits in harmony with those given in Eurocode 3 for circular hollow sections (CHS) has been derived. A new Class 3 limit has also been proposed for both EHS and CHS. An interim effective section modulus formula for Class 4 (slender) elliptical hollow sections based on BS 5950-1 has also been developed. Further investigation into effective section modulus formulations is currently underway.     

Discrete and continuous treatment of local buckling in stainless steel elements

Cross-section classification is an important concept in the design of metallic structures, as it addresses the susceptibility of a cross-section to local buckling and defines its appropriate design resistance. For structural stainless steel, test data on cross-section capacity have previously been relatively scarce. Existing design guidance has been developed based on the limited experimental results and conservative assumptions, generally leading to unduly strict slenderness limits. In recent years, available test data for stainless steel cross-sections have increased significantly, enabling these slenderness limits to be re-assessed. In this paper all available stainless steel test data have been collected and additional moment-rotation curves have been presented. The study covers both cold-formed and welded plated elements as well as CHS. Following analysis of the test results, new slenderness limits for all loading conditions have been proposed and statistically validated. In addition to re-assessment of the current slenderness limits, a new approach to the treatment of local buckling in structural elements-the Continuous Strength Method-has been outlined. The Continuous Strength Method (CSM) is based on a continuous relationship between cross-section slenderness and deformation capacity and is applied in conjunction with accurate material modelling. The method enables more rational and precise prediction of local buckling than can be achieved with the traditional cross-section classification approach, thus allowing better utilization of material and more economic design.     

Analytical formulation for the deformations of I-shapes and RHS at the plastic strain ultimate limit state

The development of “full plastic hinges” in the most stressed cross-sections is a common hypothesis considered in the elastic-plastic design of steel structures. The equations for the internal forces at the plastic limit state are then based on equilibrium conditions only, and they do not allow the global deformations corresponding to each combination of internal forces at this ultimate limit state to be estimated.This paper presents a simplified analytical model for the elastic-plastic analysis of rectangular hollow sections and bisymmetrical I-sections bent about their strong axis. This model states the relations between the global deformations (axial deformation and bending curvature) and the corresponding internal forces (axial force and bending moment) at the cross-section plastic strain ultimate limit state. It allows a realistic evaluation of the cross-section ductility, based on a relevant strain limitation at the most strained cross-section fibres.     

基于欧洲规范3的钢结构部件的强度设计优化

为了设计出受弯矩和轴向荷载作用的钢结构部件,有很多关于工型钢和H型钢的解决方案,而双对称方法只是其中一个。介绍了从多个可行的解决方案中获得最佳钢构件截面的步骤。该过程基于应用于钢筋混凝土设计的加固标准图表,也用于寻求任何关于紧凑型钢截面或非紧凑型钢截面的解决方案。需要考虑到所有关于局部失稳的方面,并要特别注意细长型钢构件的整体失稳。     

JCZY-252凿岩钻车推进梁截面的优化设计

JCZY-252凿岩钻车在井下的凿岩工作条件比较恶劣,要求导轨结构简单、质量小、耐磨性好、有足够的强度和刚度.分析该型凿岩钻车的推进器的结构,计算比较不同极限工作状态下推进梁的受力情况,确定受力最恶劣的情况,求出最小抗弯截面模量,校核推进梁危险截面的强度,从而达到理论设计的最优效果、延长凿岩机的使用寿命,使得凿岩机在工作时,能获得最优的轴向力和推进速度.     

Velocity distribution of liquid phase at gas-liquid two-phase stratified flow based on particle image velocimetry

Horizontal gas-liquid flows are commonly encountered in the production section of the oil and gas industry. To further understand all parameters of the pipe cross-section, this paper use particle image velocimetry to study the circular pipe cross-section liquid velocity distribution rule. Firstly the focus is on the software and hardware combination of image correction system, to solve the influence of different refractive indexes of medium and pipeline curvature caused by image distortion. Secondly, the velocity distribution law of the corrected stratified flow (the range of liquid flow of 0.09-0.18 m³/h, and gas flow range of 0.3-0.7 m³/h) cross-section at different flow points of the pipeline cross-section at x=0 and in the Y direction at the maximum liquid velocity is studied. It is found that these distribution laws are caused by the influence of the interphase force of the gas-liquid interface and the resistance of the pipe wall. The current measurements also produce a valuable data set that can be used to further improve the stratified flow model for gas-liquid flow.