Nonlinear Finite Element Analysis of RC Deep Flexural Simply Supported Beams Using Disturbed Stress Field Model

A nonlinear finite element analysis of 4 RC deep flexural simply supported beams with the program VT2 is presented. Crack development and failure modes , longitudinal reinforcement strain distributions and load -deflection curves were compared as a result in order to evaluate the validity of the disturbed stress field model to analyse such deep simply supported beam.     

Analyses of Interlayer Stresses and Strain Transfer in Smart Laminated Structures

A new model is proposed to analyze the strain/stress transfer relation between host materials and piezoceramic sensors/actuators under bending and axial stress loading. The finite thickness of the adhesive is taken into account. The physical layers of the piezoceramic, adhesive and structure material are further subdivided into thinner layers as fine as necessary in order to improve the accuracy of stress analysis. In each thin layer the in-plane stresses are assumed to vary linearly across the thickness. By satisfying equilibrium equations, constitutive equations and displacement-strain relations, all components of stress, strain and displacement can be expressed as functions of the in-plane forces and the moments of the thin layers. The differential equations governing the in-plane forces and the moments are obtained. Then, this analytical model is used to predict strain transfer from the structure material to the sensor. It is found, both experimentally and theoretically, that the axial strain of the host material is considerably larger than the strain of the sensor, which is directly related to the output voltage. By introducing the so-called strain transfer factor, a relationship between the output voltage of the sensor and the strain of the measured material is derived. The model is used to predict interlayer stress distributions and strain transfer, which are induced by actuator strain. The result was compared with existing experiments and FEM. There is stress concentration between the actuator and adhesive around the edge of the smart structures, which may cause debonding under high stress loading.     

Fiber Fabry-Perot Sensor and Its Application for Monitoring Bridge Strain

The strain is an important parameter that reflects the bridge health status, the fiber Fabry-Perot sensor is embedded in the concrete structure as the intelligent sensing element for the bridge strain. The strain measuring system is made up of the fiber Fabry-Perot sensor,light switch,fiber strain gauge and the comput- er; it can be used to monitor automatically the bridge strain. At present,the system has been installed in the Dafosi Bridge over the Yangtze River in Chongqing. The monitoring data show that the fiber Fabry-Perot sensor has good stability and reliability; it can be used to monitor the bridge strain for a long time.     

Degradation of Geogrids under Cyclic Tensile Load

The degradation characteristics of geogrids have important influence on the stability of reinforced embankments and retaining walls. A series of unidirectional cyclic load-extension tests under stress control were carried out on plastic geogrids. The influence of cyclic tension, pretension and load frequencies on strain and degradation characteristics of geogrids was studied. It is observed that, with the increase of cyclic tension and pretension and the decrease of load frequencies, the accumulative plastic strain and degradation index of geogrids increase, and the stiffness of geogrids decreases. Based on experimental data, the empirical equation for softening of geogrids was proposed. A modified Iwan model was put forward to describe the stress-strain relationship of the geogrids subjected to cyclic tensile load. The proposed model was proved to be reasonable by comparing the experimental data with the numerical results.     

Study and Application of High Precision Nonlinear Plane Stress Element

A tangent stiffness matrix for quadrilateral plane stress element under large rotation with small strain is proposed in this paper,The corresponding program based on this theory has been worked out;The computation of examples with analytic values has verified that the element's formulation, its program given in this paper have strong nonlinear computation ability;A nonlinear whole-course analysis of stone arch bridge has been done in this paper.The computations presented preferably a comprehensive understanding of nonlinear characteristics of stone arch bridge with small span and could be beneficial for the engineer designers.     

Deformation Transfer in Smart Structures with Integrated Piezoceramic Sensors

The deformation transfer from the loaded material to the piezoceramic sensor bounded on the surface of structures is investigated. The strain transfer factor, k , is proposed for the characterization of the deformation transfer from the material measured to the sensor. A three layer model, which consists of the sensor, the adhesive and the material measured, is used for modelling of the deformation within the structure/sensor system. Using a shear lag stress analysis method, the strain field within the three layer structure is analyzed. The closed form expression for the strain transfer factor is derived by using the strain field obtained. The influences of the thickness and the elastic modulus of the sensor and the adhesive on the k are predicted and illustrated.     

On the Type of Stress-strain Relation Curves and the Critical State for Soils

In order to discuss the influence of stress history on the constitutive relations for soils,a series of drained conventional triaxial compression tests for normally consolidated and overconsolidated clays have been carried out.It is found through comparing the stress-strain relation curves under the different stress histories that the overconsolidated ratio is the determining factor for volumetric strain.The volumetric strain is less sensitive to consolidation pressure,however.For the shear capacity,the consolidation pressure is the determining factor,but the influence of the overconsolidated ratio can not be neglected since it determines whether there will be strain hardening or strain softening as well as the grade of strain softening.Despite that,the soil specimens will finally reach a unified critical state and approximately the same residual strength.According to the principle of interaction between plastic volumetric and shear strains,the mechanism of generating two types of stress-strain relation curves for clays is explained.It is shown that the critical state is a pure process of shearing deformation in which the interaction between plastic volumetric and shear strains completely disappears.The critical state is independent of the previous stress history.     

红层泥岩桩岩接触面本构模型试验及数值模拟

桩-岩（土）接触面力学特性的研究是桩基承载机理研究的基础。通过红层泥岩桩岩接触面大型直剪试验,研究了红层泥岩桩岩接触面的力学特性,结果表明：接触面剪应力先随剪切位移增大而增大,在达到峰值后,剪应力随着剪切位移增大而降低,并最终趋于稳定值,应力应变曲线呈现出应变软化的特征。根据剪切试验结果,推导出桩岩接触面应变软化本构方程。利用fish语言对FLAC^3D中自带的理想弹塑性接触单元进行二次开发,并应用开发的模型对桩岩接触面直剪试验进行了数值模拟,分析剪应力与剪切位移之间的关系,证明了该本构能够较好地模拟接触面间的应变软化特性。     

Nonlinear Stiffness Matrices of Plane Beam Element Including Initial Stress and Strain Item

There were often happened cases for beam elements with initial stress or initial strain while the geometrically nonlinear analysis was performed for the plane structure. The deduction of stiffness matrices was awfully difficult because the nonlinear stiffness matrices included node displacement vectors and extensive matrix operations. Based on the nonlinear geometric equation of plane beam element and general elastic relationship of stress-strain including initial stress and initial strain,the tangent stiffness matrix was derived. All explicit formula of stiffness matrices including initial stress and strain item have been developed by use of the MATLAB Mathematical Tools. The results are of great significance to the nonlinear finite element programming for plane beam elements.     

Parameters design of powertrain system of electric vehicle with two-speed gearbox

The Brilliouin optical time domain analysis (BOTDA) is a newly developed technique adopted to measure and monitor the strain and temperature generated along optical fibers. The BOTDA has the characteristics of distributed measurement, long distance, high precision and durability, so it is suitable to structural health monitoring. Then a new optical fiber sensor embedded method based on air-blowing and vacuum grouting is introduced. It can lay the long distance distributed optical fiber into the concrete easily in short time. An experiment has been set up to study the validity of the new method, which shows that the embedded optical fiber can measure the concrete strain accurately, and it can realize the comprehensive, long-term, stable and real-time health monitoring to the civil structure.     

Flow Stress Behavior of 3104 Aluminum Alloy

According to different deformation conditions required in working process for manufacturing of 3104 aluminum alloy, the authors design the simulation experiments of hot rolling process at different deformation temperature and strain rates, analyze the relationships of deformation resistance, flow stress and strain rate, deformation temperature when alloy deformation. Based on experimental data analysis, it was concluded that the dominant factors affecting flow stress were the strain rate and deformation temperature, and the two parameters were also important for deforming process control.     

Analysis of ultimate load and mechanismsof failure in large cast steel joints

Based on a project of pipe truss roof framing in Chengdu, the ultimate limit state analysis is performed on cast steel joints by using FEM, in which Linear hardening elastic-plastic constitutive model is considered. The results show that, the joint has a great accumulation of plastic strain in ultimate loads, and the point of maximum stress is different from that in elastic with the development of the yielding zone. The paper propoes to use rate-type tensor for the large strain geometric nonlinear problem, shows the criterion of failure formation , and indicates that its essential to apply limit state analysis to the determination of the weakest location on cast steel joint design, which provides basis for understanding the failure modes and failure mechanism of cast steel joint and the cast steel joint design.     

微生物发酵产生他汀类化合物的研究进展

他汀类化合物作为有效的降脂类药物得到广泛的研究。目前他汀类产品主要来自于微生物发酵的次级代谢产物以及化学合成。从菌种选育、发酵条件、他汀类化合物的微生物转化、组合生物合成技术的应用等方面,对微生物生产他汀进行综述。     

Elasto-plastic analysis on surrounding rock of roadways based on seepage, strain softening and dilatancy

According to seepage body force, strain softening and rupture expansion of rock mass, elastic-plastic mechanics theory, distribution laws of stress and displacement of surrounding rock in seepage field are derived, and relationships between different zonation range of the surrounding rocks, pore water pressure, strain softening and rupture expansion are established. The results show that the pore water pressure and rupture expansion rock mass have a more obvious impact on the surrounding rock rupture area than the plastic zone. Both the plastic zone and the rupture area are larger when the seepage field is considered. The impact of strain softening on both the plastic zone and the rupture zone of surrounding rock is very significant, and both seepage and strain softening rupture expansion affect deformation of surrounding rock of roadways obviously. It provides certain reference values for the roadway support engineering in seepage field.     

苹果斑点落叶病研究

对北京地区苹果斑点落叶病研究得出,病原菌Alternaria mali Roberts强毒菌系是苹果斑点落叶病严重发生的主要原因.各果园病原菌强毒菌系发生率和致病性有差异.室内毒力测定和田间药剂防治试验结果表明,50%扑海因、70%代森锰锌、1.5%多抗霉素和10%宝丽安均有很好的抑菌效果.多抗霉素和宝丽安加入1%硼酸可以显著提高药效,并且硼酸本身对菌落生长有一定抑制作用.提出“重点保护春梢叶片,兼顾秋梢叶片”的防病原则.     

基于微卫星标记的中华鳖淮河品系遗传多样性分析

为了解中华鳖淮河品系的遗传多样性和遗传结构。本研究利用25个微卫星DNA标记分别对淮河品系中华鳖（淮河鳖）、黄河品系中华鳖（黄河鳖）和日本品系中华鳖（日本鳖）3个品系的遗传结构和系统进化进行分析。淮河鳖、黄河鳖和日本鳖的平均等位基因数(N_A)分别为5.08、5.44和6.20,平均有效等位基因数(N_E)分别为2.696、2.733和3.221,淮河鳖期望杂合度(H_E)为0.572高于黄河鳖(0.556),低于日本鳖(0.603),日本鳖遗传多样性最高,淮河鳖次之,黄河鳖最为贫乏。25个微卫星位点多态性均较高,淮河鳖、黄河鳖、日本鳖平均PIC为0.513、0.498和0.558,淮河鳖和日本鳖均属高度多态(PIC>0.5),黄河鳖为中度多态(0.25<PIC<0.5)。遗传分化指数(F_ST)分析显示,淮河鳖与黄河鳖之间属于中度分化(0.05 <F_ST< 0.15),淮河鳖与日本鳖、黄河鳖与日本鳖之间均属于高度分化(0.15<F_ST<0.25)。淮河鳖与黄河鳖遗传距离较近,与日本鳖遗传距离较远。表明目前中华鳖淮河品系有较高遗传多样性水平,遗传潜力较好。     

Exact Calculation for Measuring Electric Intensity with Ellipsoid Gauge

Based upon the anisotropy of electric polarization,the nonolinear oscillation equation of the ellipsoid in electric field is constructed by considering the rotative moment between electric field and the induced dipole moment on metallic ellipsoid of field intensity gauge. The oscillation period relative to the amplitude and electric intensity is calculated.An expression of exact computation to measure the electric field intensity is achieved.The impact of the amplitude parameter upon the experiment calculation is analyzed and the method to determine the amplitude is contributed.A contrast to the computed resuls by means of linear oscillation is undertaken to show the raising effect to the calculation precision by considering nonlinearity in oscillation.     

生防菌ANTI-8098A对青枯雷尔氏菌不同致病力菌株抑制作用的差异性

采用共培养法测定了生防菌ANTI-8098A对青枯雷尔氏菌强致病力菌株F-01-V和无致病力菌株F.1.3-010602-01-A的抑制作用,并以链霉素作参照。结果表明,生防菌ANTI-8098A对F-01-V的抑制作用较强,抑制率与生防菌培养液菌体数成正相关;对F.1.3-010602-01-A的抑制作用则较弱,菌体数为20.0×108 cfu/ml的生防菌液对F.1.3-010602-01-A的抑制率为14.7%,而对F-01-V的抑制率高达99.5%。链霉素对F-01-V和F.1.3-010602-01-A都具有较强的抑制作用,抑制率与浓度成正相关,但是对F.1.3-010602-01-A的抑制作用更强：浓度为0.25 U/ml的链霉素溶液,对F.1.3-010602-01-A的抑制率为50.0%,而对F-01-V的抑制率仅为3.3%。应用生防菌ANTI-8098制剂进行田间防治茄子青枯病的试验结果表明,生防菌制剂的防治效果达92.11%,显著地比农用链霉素的防效（72.81%）高。研究结果为阐述生防菌ANTI-8098对青枯雷尔氏菌的致弱现象提供了依据。     

各向异性砂土剪切带角度的理论分析

针对平面应变条件下各向异性砂土剪切带角度的试验规律,采用传统的3种理论和分叉理论进行对比分析。将平面应变条件下剪切带角度的试验结果按照传统3种理论整理发现,尽管传统3种理论可以估算同种砂剪切带角度的极小、中间和极大值,但无法解释其各向异性规律。砂土在平面应变条件下破坏时会产生明显的剪切带,当剪切带方向和砂土沉积面方向接近时,会较早诱发剪切带的产生,使材料强度降低,造成了平面应变条件下各向异性强度规律明显不同于常规三轴条件下的试验规律,采用分叉理论结合各向异性模型则可以有效解释这个规律。随砂土沉积面角度的变化,模型可以从细观角度解释常规三轴条件下剪切带角度的单调变化的试验规律,结合分叉理论可以描述平面应变条件下其先减小然后增大的规律。通过几种理论对比分析表明,模型结合分叉理论不但能够描述多种应力状态下的平面应变和常规三轴应力条件下剪切带角度表现的不同规律,而且能够从细观角度解释其各向异性成因。     

a rational method for defining damage variables in one dimension

To address the issue of whether it is rational to define damage variables through the degradation of elastic modules, we essentially clarified which material module should be used to describe the damage variables in unidimensional cases, and pointed out that the reference undamaged working state of material was needed firstly in order to measure the degree of damage if the strain equivalence hypothesis was used. We maintained it was baseless to consider the linear stress strain working state as an undamaged reference state. We deduced a rational definition of elastic and elasto plastic damage variables. We stated that the degradation of an unloading module can be used to define the damage variables. To illustrate the definition of damage variables, we presented an example of establishing a damage constitutive equation of concrete in compression, validate the elastic strain equivalence hypothesis, and provide an appropriate approach for establishing a damage constitutive model.