Experimental Research on Mechanical Behavior of High-strength Concrete Short Columns Confined with Stirrups

Based on the test of high strength concrete (HSC)short columns confined with stirrups 8 under axial loads and 6 under small eccentric loads, the influence of stirrups confinement on stressstrain relationship and related parameter under monoaxial compression are studied, and the effect of the type of stirrups, stirrup ratio, etc. on the HSC columns ductility is analysed. Besides, the strength and deformation behavior of HCS columns under small eccentric compression are explored.Based on the experimental study, the complete stress-strain curves of confined HSC and the formula for calculating the related parameter are presented in this paper.     

Rut resistance Properties of a Large stone Flexible Base under Heavy Loads

The rut resistance properties of large stone flexible bases are studied, taking into consideration heavy loads and using computer simulation and numerous indoor tests. In computer simulations of large stone flexible bases, a calculation method was formulated for predicting asphalt pavement rut under dynamic loads. The method was based on the coupling of vehicle dynamic loads and pavement surface unevenness. The results of indoor testing and three dimensional numeric calculation under dynamic loads are confirmed by tracking observation results of a test road. We conclude that the rut resistance properties of large stone flexible base asphalt pavement built using low grade asphalt and low crush value high performance aggregate with reasonable gradation is no worse than that of the semirigid base asphalt pavement, and that ruts mainly are caused by the lateral shear.     

Analysis on Effect of Traffic Loads on Landslide Stability

In the design of landslide control engineering,the effect of traffic loads has not been taken into account.The authors simplified the traffic loads as mobile dead loads and traffic dynamic load.The mobile dead load ranges from 2.34 to 6.41 kPa.The impact coefficient was chosen to denote the traffic dynamic load and ranges from 0.1 to 0.4.Using several stability analysis methods widely accepted by engineers,combining two analysis samples,by the contrast of stability tests with and without consideration of the mobile dead load or the traffic dynamic load,the authors found that when the traffic load is not taken into account,the stability coefficient of shallow layer landslide(<8m) is overrated by 4.3-11 percent or 5.8-12.1 percent in comparison with the case when the mobile dead load or traffic dynamic is taken into account respectively,that is,the influence of mobile dead loads and traffic dynamic load is cannot be neglected.In case of medium deep layer landslide or the road is passing through the anti sliding section,the influence of the traffic load is a little and can be neglected.     

落锤冲击气囊施加均布动荷载的试验方法

在结构构件上施加均布冲击(爆炸)荷载一直是动力试验领域的难题。提出了一种落锤冲击气囊施加均布动荷载的试验装置,和一个双自由度弹簧阻尼冲击加载简化分析模型;给出了该模型的基本力学方程、边界条件和求解方法,并进行了有限元验证;建立了所提出冲击加载试验装置的精细化有限元模型,分析了构件上各受荷区域的荷载均布情况,验证了所提出装置的可行性。基于所建立的简化分析模型,讨论了刚度、荷载作用时间和阻尼比等关键参数,对构件上动荷载的影响,并给出了基本规律。计算结果表明,在选定合适的参数后,落锤冲击气囊试验装置能够较好地模拟构件上的均布动荷载,为实验室中进行爆炸冲击试验提供了一种可能。     

Galerkin Approximate Solutions of Displacement Including the Effect of Dead Loads for Two Kinds of Rectangular Plates

Based on the strain energy considering the effect of dead loads, the general form static equilibrium differential equations were formulated by means of the potential energy principle. The approximate solutions of live load or later load displacement including the effect of dead loads for the clamped rectangular plate and the simply supported rectangular plate were generated by the Galerkin method. These formulas are simple and clear, and their physical concepts are explicit. The correctness of these formulas was verified by the finite element method. The dead loads and other factors that influence the effect of dead loads are shown by these formulas. The effect of dead loads on the two different boundary condition rectangular plate were analyzed by these approximate solutions. The effect of dead loads improves the bending stiffness of plate and minimizes the displacement of live loads or later loads. The key physical factors governing the effects of dead loads on plates are the dead load, the ration of span to thickness and boundary condition etc. This effect of dead loads is not negligible, especial in thinner plates or plates with smaller stiffness, more attention should be paid to the effect of dead load in the calculation and analysis for plates.     

近爆作用下压型钢板组合楼板动力响应及影响因素数值分析

利用有限元软件ANSYS/LS-DYNA,采用流固耦合的计算方法,对压型钢板组合楼板在近爆炸荷载作用下进行了不同工况的数值模拟,得出其受力形态,分析其动力响应及破坏过程,找出影响楼板动力响应的主要因素。数值分析结果表明：适当增加混凝土厚度和提高压型钢板强度,可以显著降低组合楼板的跨中最大位移,提高组合楼板的延性和抗爆性能;组合楼板中钢筋间距的变化,对组合楼板抗爆性能影响较小。     

CALCULATION OF THIN PLATES BENDING EEFORMATION AND CRITICAL PRESSURE BY THE TCHEBYCHEV''S POLYNOMIALS

In this paper trial functions of the second Tchebychev's polynomials is used with Cantorovich variational method in energy functional of thin plate. Bending deformaion of rectangle plate under even loads or concentrate force with several bearing and critical pressure in buckling is resolved. Though the first similar is used but calculations indicate that this method is simple and exact in engineering.     

G324牵引车车架弯曲工况强度分析及改进

为了对G324牵引车的车架进行强度分析及改进,根据牵引车的实际工况,选择对车架影响较大的弯扭工况进行分析,利用HyperMesh有限元软件建立了某牵引车车架结构有限元分析计算模型。通过计算得出该车架在这两种工况下的应力分布云图,对车架进行改进并分析增加L板和将鞍座瓦轮板改为平板以及取消加强板3种模型的实际情况,得出满足车架强度要求的具体模型,为牵引车车架的设计及改进提供参考依据。     

Aerostatic stability analysis of long span half-through arch bridges

The main arch of a long-span arch bridge is a compression member. The static wind loads on the bridge not only causes changes of dynamic characters, but also leads the structure to collapse or buckling. Especially, when the arch bridge has longer span and less lateral braces,its stability is much different from the long span cable-stayed bridges and suspension bridges. This paper takes Chongqing Caiyuanba Yangzi River Bridge as a typical example and conducted the wind section tunnel tests. The displacement response of the bridge is obtained and its yield and static stability mechanism under static wind is analyzed. The results show that those factors, such as initial attack angle of the static wind, material yield strength and the static forces coefficients, have great effects on the aerostatics stability of a long span half-through arch bridge.     

Experimental Research on Concrete Strength under Freeze-thaw Recycle Action with Ultra-low Temperature

The concrete structure has been used in low and ultra-low temperature environment. But few researches are experienced on its properties under freeze-thaw recycles with ultra-low temperature. Based on the standard for test methods of long-term performance and durability of ordinary concrete, considering the influence of the times and minimum temperature of recycles, water-cement ratio and the external environment humidity, compressive and tensile strength of cubic concrete and scanning electron microscopy on the residual sample are experimented to explore the impact of freezing and thawing cycles under ultra-low temperature on its strength and microstructure. The results show that the role of cryogenic temperature for freeze-thaw cycles has a greater effect on concrete performance. With the temperature decreasing and water-cement ratio increasing, the damage tends to grow up. Consistent with the results of the strength tests, electron microscopy tests show that the pore size of mortar increases and the material becomes looser.     

Study on Effect of Longitudinal Reinforcement Ratio on Shear Behavior of Restrained Beams with Web Reinforcement

In this paper, five restrained beams with web and different longitudinal reinforcement ratio as well as above longitudinal reinforcement truncated were tested under static point loads. On this basis, the overall process of cracking development under shear and the effect of longitudinal reinforcement ratio on shear strength was investigated     

An efficient laser sensor system for apple impact bruise volume estimation

Fruit are subjected to several external loads during processes from the orchard to the market, which result in bruising and therefore, quality loss. In this study, we developed a system based on a line laser light source and light detector for a rapid and efficient estimation of the bruise volume of apples (Malus domestica Borkh L. cv. Starking Delicious) dropped from a certain height onto a steel impact plate. We measured two parameters, namely rise time and dwell time, extracted from response signals generated by the proposed system during the impact test. These parameters are related to contact time, showing how long the fruit remains in contact with the impact plate. The experiments were conducted at six different drop heights and two different temperatures. It was found that there was a strong relation with coefficients of determination of more than 0.93 between bruise volume and dwell/rise time, in which the bruise volume decreased with the increasing rise time/dwell time as a power function. Furthermore, the results showed that warm apples developed greater bruise volume than cold fruit, and the estimated regression lines and curves for cold fruit had higher coefficients of determination than those of warmer fruit.     

THE EVALUATION OF SHEAR STRENGTH TAKING ACCOUNT OF SPAN-TO-HEIGHT RATIO OF SIMPLE BEAMS UNDER UNIFORM LOADS

By introducing the span-to-height ratio,this paper deduces wo evaluating equations of shear strength of simple reinforced concrete beamwith stirrups and under uniform loads.This makes the shear stressing concept consistent with the evaluating equations,thus improves the evaluating equationsof shear strength of the New Code.Two equations are provided with auto-regulating function on shear strength for a cross section of beam.They aresimple and convenient in evaluation.The working time used for design is not increased and 10% of stirrups is economized in frequent conditions of span-to-height ratio.     

Numerical Simulation of Dynamic Response of Suspension Insulator String

Finite element method is applied to analyze the windage of suspension insulator strings under dynamic wind loads. The dynamic response of a suspension insulator string of 500 kV high voltage transmission line is numerically simulated with ABAQUS software, and results demonstrate that the windage angle of suspension insulator string is larger than that calculated by the conventional design code, which might be one of the main reasons of the frequently happened windage flashover accidents.     

Numerical Simulation for B900FD-1 Bulletproof Armor Plate Against Penetration

ANSYS/LS-DYNA is used to simulate the penetration process of B900FD - 1 bulletproof armor plate, Comparisons and analysis were made between numerical simulation and experiment results. The numerical simulations shows that the Johnson-Cook constitutive model could simulate the physical and mechanical behaviors of ductile materials under shock-loaded. The ultimate-thickness of B9OOFD-1 bulletproof armor plate under 500m/s impact velocity is analyzed by more numerical simulations.     

Factors Affecting the Ultimate Bearing Capacity of Cold-Formed Steel Portal Frames

The FEM simulation analysis method was studied to identify the ultimate bearing capacity of cold-formed steel portal frames.In this study,the beam-spring system was used to simulate the performance of joints.The initial imperfection of frame components was considered.The deformation performance and failure features of portal frame structures under vertical loads also were studied.The analytic results of the FEM simulation analysis method are close to the values obtained by experimentation.The ultimate bearing capacity of portal frames were computed by changing parameters such as the web plate thickness,the flange width,the plate thickness of brackets,the portal frame roof inclination,and the column footing stiffness.The analytic results indicate that the ultimate bearing capacity may be improved when the parameters mentioned above are increased.     

谷物储藏中动态载荷的研究与进展

概述了粮仓中谷物动态载荷的研究与进展.论述了粮仓的装仓压力、卸仓压力、热量变化引起的载荷、谷物水分变化引起的载荷和振动引起的载荷的主要研究成果和研究现状;并简述了未来的研究方向.     

Experiments on heat loss characteristics in a fully opened cylindrical cavity receiver

The climate has a great impact on highway bridge rubber bearings than on building rubber bearings. In order to study the change of the mechanical properties during the life of the plain chloroprene rubber bearings of highway bridge under freeze-thaw cycle condition, the plain chloroprene rubber bearings were processed 25, 50, 75, 100 times by freeze-thaw cycle in the standard freeze-thaw chamber, then the axial compression tests were carried. The changes of the performance indicators in the bearing capacity , the ultimate compressive strength, vertical stiffness, elastic modulus under different freeze-thaw cycles were analyzed comparatively. The results show that the plain chloroprene rubber bearings are more prone to brittle failure after the freeze-thaw cycle, and the failure phenomena of steel plate exposing or cracks is more serious than the phenomena of the standard specimen. With the increase of the number of freeze-thaw cycle, the ultimate bearing capacity, ultimate compressive strength and compressive elastic modulus of the plain chloroprene rubber bearings decrease. The attenuation formula and decay curve in 50 years of ultimate compressive strength and elastic modulus of compression are analyzed by least square method, the trends of change are both in line with the exponential function. The mechanical properties of plain chloroprene rubber bearings of highway bridge significantly decreased under freeze-thaw cycle condition. therefore, the temperature ranges of plain chloroprene rubber bearings of highway bridge should be strictly controlled, and some suggestions, such as increasing its minimum applicable temperature, usng the natural rubber bearings as much as possible in cold regions, have been given.     

陆海杂种高代回交自交系纤维细度性状相关性分析

 利用陆地棉34B与海岛棉Giza70杂交所得的稳定的高代回交自交系BC₂F_4:6 、BC₂F_4:7家系,开展了三个环境下纤维细度等品质性状的相关分析。结果表明：1)纺纱均匀指数与长度、整齐度、比强度呈极显著正相关,与伸长率呈极显著负相关。纤维长度和比强度间均存在极显著的正相关,与伸长率呈极显著负相关。2) HVI 900测定的麦克隆值与比强度和纺纱均匀指数呈极显著负相关;成熟度比率与麦克隆值呈显著或极显著正相关,与线密度呈极显著负相关,与其它性状间的相关性三个环境下都不一致;线密度与纺纱均匀指数呈极显著正相关,与长度、比强度均达到极显著或显著负相关,与整齐度不相关,与伸长率为负相关。相对而言,线密度与各性状的相关性要比HVI 900测定的麦克隆值和成熟度比率稳定,受环境影响小,有必要进一步加强对线密度的选择及深入研究。     

Dynamic Properties of Yangla Copper Tailings Material

Tailing sands, coarse tailing sands and fine tailing sands all were prepared by artificial partitioning experimentation in accordance with the requirements of central line damming. DDS 70 electromagnet kinetic equipment was used to study the dynamic strength, stress strain relationship, dynamic modulus and damping ratio of three tailing sand types. The dynamic strength and parameters were determined, and some influential factors, such as particle composition, confining pressure, consolidated stress ratio and dynamic stress, were discussed. The test results provide basic data for the stability evaluation of the Yangla copper tailing dam under a magnitude 8 earthquake.