Stiffness and Shear Stress Distribution of Glulam Beams in Elastic-Plastic Stage:Theory,Experiments and Numerical Modelling

Traditional methods focus on the ultimate bending moment of glulam beams and the fracture failure of materials with defects,which usually depends on empirical parameters.There is no systematic theoretical method to predict the stiffness and shear distribution of glulam beams in elastic-plastic stage,and consequently,the failure of such glulam beams cannot be predicted effectively.To address these issues,an analytical method considering material nonlinearity was proposed for glulam beams,and the calculating equations of deflection and shear stress distribution for different failure modes were established.The proposed method was verified by experiments and numerical models under the corresponding conditions.Results showed that the theoretical calculations were in good agreement with experimental and numerical results,indicating that the equations proposed in this paper were reliable and accurate for such glulam beams with wood material in the elastic-plastic stage ignoring the influence of mechanic properties in radial and tangential directions of wood.Furthermore,the experimental results reported by the previous studies indicated that the method was applicable and could be used as a theoretical reference for predicting the failure of glulam beams.

Ideal Drift Response Curve for Robust Optimal Damper Design for Elastic-Plastic MDOF Structures under Multi-Level Earthquakes Dedicated to Professor Karl S.Pister for his 95th birthday

A new method of robust damper design is presented for elastic-plastic multi-degree-of-freedom(MDOF)building structures under multi-level ground motions(GMs).This method realizes a design that is effective for various levels of GMs.The robustness of a design is measured by an incremental dynamic analysis(IDA)curve and an ideal drift response curve(IDRC).The IDRC is a plot of the optimized maximum deformation under a constraint on the total damper quantity vs.the design level of the GMs.The total damper quantity corresponds to the total cost of the added dampers.First,a problem of generation of IDRCs is stated.Then,its solution algorithm,which consists of the sensitivity-based algorithm(SBA)and a local search method,is proposed.In the application of the SBA,the passive added dampers are removed sequentially under the specified-level GMs.On the other hand,the proposed local search method can search the optimal solutions for a constant total damper quantity under GMs’increased levels.In this way,combining these two algorithms enables the comprehensive search of the optimal solutions for various conditions of the status of the GMs and the total damper quantity.The influence of selecting the type of added dampers(oil,hysteretic,and so on)and the selection of the input GMs on the IDRCs are investigated.Finally,a robust optimal design problem is formulated,and a simple local search-based algorithm is proposed.A simple index using the IDRC and the IDA curve of the model is used as the objective function.It is demonstrated that the proposed algorithm works well in spite of its simplicity.

Elastic-plastic contact force history and response characteristics of circular plate subjected to impact by a projectile

A new elastic-plastic impact-contact model is proposed in this paper. By adopting the principle of minimum acceleration for elastic-plastic continue at finite deformation, and with the aid of finite difference method, the proposed model is applied in the problem of dynamic response of a clamped thin circular plate subjected to a projectile impact centrally. The impact force history and response characteristics of the target plate is studied in detail. The theoretical predictions of the impact force and plate deflection are in good agreements with those of LDA experimental data. Linear expressions of the maximum impact force/transverse deflection versus impact velocity are given on the basis of the theoretical results.

An elastic-plastic analysis of short-leg shear wall structures during earthquakes

Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. To analyze the elastic-plastic response of a short-leg shear wall structure during an earthquake, this study modified the multiple-vertical-rod element model of the shear wall, considered the shear lag effect and proposed a multiple-vertical-rod element coupling beam model with a new local stiffness domain. Based on the principle of minimum potential energy and the variational principle, the stiffness matrixes of a short-leg shear wall and a coupling beam are derived in this study. Furthermore, the bending shear correlation for the analysis of different parameters to describe the structure, such as the beam height to span ratio, short-leg shear wall height to thickness ratio, and steel ratio are introduced. The results show that the height to span ratio directly affects the structural integrity; and the short-leg shear wall height to thickness ratio should be limited to a range of approximately 6.0 to 7.0. The design of short-leg shear walls should be in accordance with the ＂strong wall and weak beam＂ principle.

Harten-Lax-van Leer-contact(HLLC)approximation Riemann solver with elastic waves for one-dimensional elastic-plastic problems

A Harten-Lax-van Leer-contact （HLLC） approximate Riemann solver is built with elastic waves （HLLCE） for one-dimensional elastic-plastic flows with a hypo- elastic constitutive model and the von Mises＇ yielding criterion. Based on the HLLCE, a third-order cell-centered Lagrangian scheme is built for one-dimensional elastic-plastic problems. A number of numerical experiments are carried out. The numerical results show that the proposed third-order scheme achieves the desired order of accuracy. The third-order scheme is used to the numerical solution of the problems with elastic shock waves and elastic rarefaction waves. The numerical results are compared with a reference solution and the results obtained by other authors. The comparison shows that the pre- sented high-order scheme is convergent, stable, and essentially non-oscillatory. Moreover, the HLLCE is more efficient than the two-rarefaction Riemann solver with elastic waves （TRRSE）

ELASTIC-PLASTIC CONSTITUTIVE RELATION OF PARTICLE REINFORCED COMPOSITES

In this paper, a systematic approach is proposed to obtain the macroscopic elastic-plastic constitutive relation of particle reinforced composites (PRC). The strain energy density of PRC is analyzed based on the cell model, and the analytical formula for the macro-constitutive relation of PRC is obtained. The strength effects of volume fraction of the particle and the strain hardening exponent of matrix material on the macro-constitutive relation are investigated, the relation curve of strain versus stress of PRC is calculated in detail. The present results are consistent with the results given in the existing references.

Numerical Simulation and Experimental Studies on Elastic-Plastic Fatigue Crack Growth

A elastic-plastic fatigue crack growth(FCG)finite element model was developed for predicting crack growth rate under cyclic load.The propagation criterion for this model was established based on plastically dissipated energy.The crack growth simulation under cyclic computation was implemented through the ABAQUS scripting interface.The predictions of this model are in good agreement with the results of crack propagation experiment of compact tension specimen made of 304 stainless steel.Based on the proposed model,the single peak overload retardation effect of elastic-plastic fatigue crack was analyzed.The results shows that the single peak overload will reduce the accumulation rate of plastic energy dissipation of elements at crack tip plastic zone,so that crack growth will be arrested.The crack growth rate will not recover until the crack tip exceed the affected region.Meanwhile,the crack growth rate is mainly determined by the amplitude rather than the mean load under the condition of small scale yielding.The proposed model would be helpful for predicting the growth rate of mode I elastic-plastic fatigue crack.

Demand Elasticity for China's Major Imported Agriculture Textile Material Based on Restricted Version of Source Differentiated Almost Ideal Demand System Model

By comparing China's import of major imported agriculture textile material( cotton and wool),the characteristics of import are concluded. On this basis,a restricted version of source differentiated almost ideal demand system( RSDAIDS) is used to estimate the income and price elasticity of major imported agriculture textile material from the major sources based on the data from 1992 to 2015. The results are shown as follows.( 1) Although the dependency on imported cotton is lower than wool, the fluctuation of cotton import is much more drastic; China's demand for cotton is relatively price elastic with higher expenditure elasticity compared with wool; besides,the existence of complementarity is proved between imported cotton and wool.( 2) According to the import elasticity of cotton,demand for cotton imported from India shows priority over cotton from other sources; demand for cotton imported from America is the most price-sensitive one; substitution among cotton from different sources is weak.( 3) According to the import elasticity of wool,wool imported from Uruguay has bright market prospects. In addition,wool imported from Australia has irreplaceable advantage than that from New Zealand.

Study of the Influence of Nanoparticles on the Molecular Model of an Ideal Fluid

In the article a molecular model of oil with nanoparticles on the basis of the model of ideal fluid is considered. It is assumed that the molecular model of the oil can be represented as a homogenous distribution of identical molecules in space. It is assumed that the central interaction between the oil molecules and nanoparticles, results in a change of the model parameters. It is shown that for an ideal fluid the effect of nanoparticles is reduced to a change of the coefficient at the pressure.

A Finite-Mode Model of Ideal Fluid Dynamics on the 2-Sphere

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A Numerical Simulation of Air Flow in the Human Respiratory System Based on Lung Model

The lung is an important organ that takes part in the gas exchange process. In the study of gas transport and exchange in the human respiratory system, the complicated process of advection and diffusion (AD) in airways of human lungs is considered. The basis of a lumped parameter model or a transport equation is modeled during the inspiration process, when oxygen enters into the human lung channel. The quantitative measurements of oxygen are detached and the model equation is solved numerically by explicit finite difference schemes. Numerical simulations were made for natural breathing conditions or normal breathing conditions. The respiratory flow results for the resting conditions are found strongly dependent on the AD effect with some contribution of the unsteadiness effect. The contour of the flow rate region is labeled and AD effects are compared with the variation of small intervals of time for a constant velocity when breathing is interrupted for a negligible moment.

基于理想过程模型的探究学习评价——探究学习评价的新思路

在教育情境下,探究学习被定义为旨在达到特定高阶能力目标的学习过程。因此,其评价应侧重于过程取向,而非结果取向。为刻画理想的探究学习过程并保留情境信息,特别是学习目标信息,需对特定的探究学习设计进行理想过程建模,所生成的理想过程模型可作为评价实际发生的探究学习的标尺。探究学习的理想过程建模包括以下五个步骤:(1)完成探究学习的详案设计;(2)绘制探究学习活动所蕴含的知识建模图;(3)具体描述探究学习的整体过程;(4)将探究学习整个过程划分为多个环节,并绘制探究环节图;(5)将所有环节图按照探究学习的一般过程连接成一个整体,形成理想过程模型。对实际发生的探究学习也应进行上述操作,并在完成预处理后,生成探究学习的真实过程模型。通过比较真实过程模型与理想过程模型,找出差异点,依此可以评估实际发生的探究学习。这种评价方法不仅有助于了解探究学习的质量,还能为探究学习设计的改进提供反馈,更为重要的是,它可以使探究学习成为日常教学的一部分。

高压氢气泄漏过程中气体参数计算的新方法

基于气体等熵喷射过程和绝热变化过程分析氢气泄漏的热力学过程,建立理想气体状态方程、Abel-Noble状态方程和基于NIST(National Institute of Standards and Technology)的真实气体状态方程的计算模型,利用MATLAB对稳态/非稳态泄漏过程进行计算。结果显示,建立的稳态泄漏模型能够精确计算泄漏口处的相关参数,在保证计算精度的前提下与数值模拟相比,误差可以忽略不计;非稳态泄漏模型中,与基于理想气体状态方程和Abel-Noble状态方程相比,基于NIST的真实气体状态方程误差更小;非稳态泄漏过程中,罐内气体温度高于理论预测值,泄漏质量流量小于理论预测值。真实气体模型在一定程度上体现了热力学模型的局限性,但与数值模拟等计算方法相比,该模型计算更加快捷精准,对实际气体泄漏事故的预测具有理论指导意义。

共享制造环境下基于Z-RIM的QoS多方异质评价方法

为解决共享制造环境下决策信息异质、候选服务数量动态变化的制造服务QoS评价问题,基于平台、服务需求方、服务提供方的三方决策信息,提出一种符合共享制造特点的QoS多方异质制造服务评价方法。通过精确数、语言变量和Z-number处理异质信息;基于共识最大化计算决策方权重向量,利用TrFWAA算子集结多方信息,依据离差最大化模型计算属性权重;在此基础上,采用RIM对各服务进行评估。结合共享制造环境下的制造业服务优选案例对提出的方法进行验证分析,结果表明该方法具有较好的实用性和优越性。

基于知识工程的面向船体结构总体振动的计算网格生成方法

根据结构总体振动计算网格生成的工程需求,分析其具体使用要求与实现难点,结合知识工程的理论,开展基于3DExperience三维设计软件中的知识工程工具的分析,主要包括基于三维模型的知识表达、知识推理技术,提出具体的生成面向结构总体振动网格的实施方案,并通过某客滚船项目进行验证,结果表明,知识工程具有普适性、与设计模型强关联、开发成本低等特点,在船舶领域有极大的应用前景。

基于云-TOPSIS法的应急物流供应商综合评价

为实现应急物流降本增效的目标,从供应商层面出发,运用云-逼近理想解排序法(TOPSIS)评价应急物流供应商综合能力;根据应急物流特点,从应急响应能力、物资质量、成本控制、应急响应柔性、企业内外部条件等5方面,构建应急物流供应商综合评价指标体系;借鉴博弈论思想,将用改进熵权法求得的客观权重和用层次分析法(AHP)求得的主观权重作为博弈对手,确定最优组合权重;运用云模型量化指标决策云和加权云对供应商的模糊定性评价语义;采用TOPSIS法构建正负理想解集合,计算备选方案与正负理想解的距离确定相对贴近度,确定最优备选方案。研究结果表明:指标决策云能准确地将评价语言量化,云-TOPSIS法的评价结果更合理;在供应商相对贴近度排序中,采用云-TOPSIS法计算的最优与最劣者差值为0.3315,而TOPSIS法为0.0882,两者相差0.2433,表明云-TOPSIS法的评价结果区分度更大,能更直观地辅助决策者做出最优选择。

住宅小区理想规模的模型探究——基于共有空间社会密度的视角

住宅小区内共有空间的社会密度会对居民间的邻里交往产生显著影响。为保证住宅小区共有空间资源的数量和品质,在第Ⅲ建筑气候区条件下建立小区模型,对不同类型小区的共有空间进行分析。结果显示,随着小区内建筑平均层数的增加,户均共有空间资源的数量逐渐减少,共有空间的品质在空间尺度、围合度、私密性等维度上显著降低。基于模型研究结果和城市对土地利用的要求,进而提出住宅小区的理想规模为3~4 hm2,住宅平均层数宜为5~8层,而当确有需要建设高层住宅时,住宅平均层数也不宜超过14层。

旋转爆震火箭发动机推进性能分析

针对旋转爆震发动机(Rotating Detonation Engine,RDE)燃烧室简化二维流场,采用流场分区,建立了一种适用于RDE工作特性的性能分析模型,可快速准确地估算RDE的推进性能。模型考虑了燃烧室内气流膨胀过程中的气流角度匹配,可准确描述存在单个爆震波时的基本流场结构特征,包括爆震波倾斜角度、斜激波角度、滑移线角度等,结果与已有文献的研究结果一致性较高。根据模型流场中所取控制体的进出口参数,可得理想膨胀状态下RDE的推进性能,估算结果与已有性能估算模型吻合较好,与已有实验数值偏差为8%。经验证推导,模型亦可用于多波模态。采用该性能分析模型对比研究了不同反应物当量比、进气总压和总温下火箭式RDE的推进性能。研究表明,性能分析模型可准确反映RDE燃烧室的非稳态流场特征,且可快速准确地估算RDE的推进性能,为RDE推进性能的评估提供了简便可靠的方法。

IDEAL模型的研究

首先介绍了软件过程能力成熟度模型 (SW CMM)及其实施方法论IDEAL模型的概念 ,接着阐明了IDEAL模型各个阶段的目的、任务和软件过程改进的管理 ,举例说明了用PDCA周期实施软件过程改进 ,并对ICASE模型进行了简单说明。最后结合中国传统文化和信息时代的特点对SW CMM实施方法论进行了若干讨论。