Strain rate effects on dynamic behavior of reinforcement concrete columns with various reinforcement ratio

The mechnical characteristics of concrete is sensitive to the strain rate and it is crucial to consider the effect of load rates on the behavior of reinforced concrete (RC) structures subjected to dynamic loads such as severe earthquakes. In this study, numerical simulations on the dynamic behavior of typical RC column specimens under dynamic loadings with different load rates were performed. Concrete constitutive model considering the strain rate effects proposed by the CEB code was employed with a fiber model to characterize the nonlinear strain rate dependent behavior of RC columns. The developed dynamic fiber element model was validated by comparing the simulated results of four RC column specimens with the fast loading test results. Results show that the developed fiber element model can predict the behavior of RC columns with acceptable accuracy. After valiating the proposed fiber elemen model considering the strain rate effect, the load carrying capacity of different RC columns with various longitudinal reinforcement ratios and volumetric stirrup ratios were simulated. Results show that the trends of the influences of longitudinal reinforcement ratios and volumetric stirrup ratios on the load carrying capacity of the RC columns under dynamic loadings are different.     

Mechanical Properties of Regional Confined Rectangular Concrete Columns under Axial Loads

Based on experimentthatal results,we conclude that confinement in regional confined concrete(RCC) columns is more efficient than that in normal confined concrete(NCC) columns.As loads increase,NCC column sections tend to become round;the corner concrete in the core area may break;and,the strains of external stirrups tend to drop slightly after the peak load.RCC columns,however,remained thoroughly rectangular and the stirrup strain increased steadily.The failure mode of RCC columns was totally different from that of NCC columns.While NCC columns tended to fail in shear,followed b a rapid drop in load carrying capacity,the RCC columns developed gaps in their midsections and the columns separated into several slender columns.After a long deformation period,the RCC columns retained approximately 40% of their load carrying capacity.It can be expected that this characteristic may benefit the anti-seismic capacity of structures.     

Shear Performance of Steel Plate with Trilateral Constrained

The load carrying test for four steel plate shear walls specimens with various ratio of width thickness are carried out so as to test the failure mode and the shear strength of steel plate with trilateral constrained, and the lateral stiffness and the buckling mode are investigated in the test. The result indicates that the ratio of width thickness of steel plate exerts effects on the shear carrying capacity and failure mode; the buckling of steel plate does not have lateral stiffness. Based on the failure mode of steel plate, the computation model of lateral performance is presented by theoretical analysis. The restraining stiffness of double angle and the buckling restrained stiffness of steel plate are the important design conditions. Formulae to determine the elastic lateral stiffness and the angle type is proposed, which can be used in the preliminary design of steel plate with trilateral constrained.     

NONLINEAR RESPONSE STUDIES OF TALL STEEL FRAMES

Considerable eftects of geometric nonlinearity upon tallsteel frames and flexibly jointed steel frames are recognized.Systematicanalysis philosophy of geometric nonlinearity under various coordinatesystems and its corresponding explicit expression of tangent stiffness matrices are comprehensively embodied.The entries in tangent stiffnessmatrices with its nonlinear behavior and its abstrusely implied physicmeanings are expounded and a straight forward derivation technique ofnonlinear matrices is given.A computer algorithm which can performwhole range studies of steel frames by considering geometric and materialnonlinearities up to the ultimate load carrying capacity is implemented.     

异程管网热湿负荷分配次优解群及适应性

提出了一种基于次优解群统计分析的异程管网热湿负荷分配方法,采用变步长+随机走步的寻优计算方法,获得空调季不同负荷率下热湿负荷再分配的次优解群,分析次优解群的随机行为和统计规律,以此探索复杂变量约束下的冷冻水系统负荷分配的优化控制策略及其适应性。根据计算结果,在40%、60%、80%、100%这4种负荷率下末端人数次优解重叠率最高达到24%。研究表明,次优解群随机行为与管网热湿负荷分配策略存在相关性,离冷源侧越近,末端人数次优解重叠率越高,分配策略的负荷适应性越好,其权重越大。     

Contact analysis of a new style planetary reducer with a double crank and internal gear board

To address the problems of low carrying capacity and short life of bearings in current ring reducers, a new type of ring reducer is proposed which consists of a two stepped transmission. One is a planetary transmission, and the other is an N type planetary transmission with a low tooth number difference. Based on the analysis of structural features, the transmission principle, and a transmission load situation, a contact finite element model of the new type of ring reducer is set up, and the stress value and the actual pairs of meshing teeth are derived by calculation. Based on gear modification research theory, the second stage transmission gear pairs of the new reducer are modified on its teeth profiles. Results demonstrate that the load capacity of transmission gear pairs have been enhanced greatly.     

The Hysteretic Performance Analysis and Experiment on K-type Overlap Joints of Circular Steel-tubes

Joints are the most important parts of the space structure, the load-derormation curve (hysteretic curve) under repeated loading is the comprehensive reflection of their mechanical properties such as ductility, energy dissipation capacity, strength, stiffness and so on. By the simulation experiment analysis and the finite element simulation between the two models of hidden welding and no-welding hidden in K-type node in the chord axial reciprocating load resulted in the failure modes and hysteretic curve, the result of comparative analysis about finite elements is consistent with that of experiment study. The results show that the destroyment at hidden welding seam node is partly, the take-over is broken down at the welds finally. The welding line is destroyed overall when facing the destroyment of no-welding node. The carrying capacity of the hidden welding is obvious. Through the finite element simulation analysis instead of phase through node hysteretic performance test is feasible.     

Load-carrying Capacity Calculate and Analysis of Staging Stake

Falsework is a kind of scaffoldwork using load bearing. It has widely use in scaffoldwork and bridgework and steel construction. For assuring falsework safety on structure construction, it is very important to quickly and accurately calculate falsework. Load - carrying capacity of staging of should be calculate by special design, which is from common used single row or double rows falsework. The authors analyze all kinds of factor and failure mode related to carrying capacity and find the result of numerical list by ANSYS program and code when the parameter of staging is determinated. It has important gaidance role in erection of falsework pole.     

陕西省粮食生产中存在的问题与对策研究

依据统计资料分析了陕西省目前粮食生产的现状,指出我省粮食生产存在的主要问题是: 资源短缺、粮食播种面积减少、生产投入不足,连年干旱和粮食价格等;提出了加强农业基本建设是稳定粮食生产的保证,依靠科技进步是挖掘粮食增产潜力的主要途径,依靠政策调动各方面的积极性则是我省粮食持续稳定增长的重要因素。     

Stochastic Response Surface Method Based on Radial Basis Functions

For non-ideal interpolation results of complex implicit nonlinear functions between non-normal distribution response and standard normal distribution inputs using stochastic response surface method, radial basis functions was used to replace Hermite polynomials so as to solve complex implicit nonlinear function interpolation problem for its excellent performance on scattered data interpolation. A few nonlinear analytical functions and uncertainty problems of the load carrying capacity of single circular concrete filled steel tubule (CFST) arch were used as examples to test and verify the precision of proposed method in non-normal distribution response interpolation and its engineering applicability. The results show that stochastic response surface method based on radial basis functions performs well in fitting highly nonlinear input implicit functions, and can achieve high precision on multi-parameters CFST arch load carrying capacity uncertainty problems. Meanwhile, the method has less sample points compared to the Hermite polynomials method.     

A Design Method for Composite Ply Containing Preformed Hole

A iteration method for the orientation and the distribution of fibers in a composite ply with a pre-formed hole is proposed, which is based on the FEM analysis and the corresponding criterion of strength and continuous condition of fibers. It is shown that, there is marked increase of the load carrying capability compared with that of the ply with a drilled hole. The obtained result can further be extended to the design of composite laminate with pre-formed holes.     

Human simulated intelligent control for dynamic walking of biped robot

A human simulated intelligent control scheme based on sensory-motor schema for dynamic walking of biped robot is presented to solve the complex controller design.The dynamics model of a five-link planar biped is established. By imitating human walking movement and apprehending the posture change of the legs, the complex process of dynamic walking for biped robot is divided by four sequence phases. The multi-mode control law and the group of sensory-motor schema are designed based on the analysis of quality-quantity combination to the phase plane. Simulation results show that the proposed control strategy is effective to ensure continuous dynamic walking of biped robot and the control method is simple and easy to be realized.     

Analysis of Quality Problems and Their Traits of Main Structure in Construction Engineering

The main structure in construction engineering is the organic part of the load - carrying system of construction engineering. Its quality is the core for realizing the value of construction engineering quality. The essence of its quality problems is that the quality behavior, intermediate output or final product of the construction body cant meet the requirements of national laws, regulations and obligatory criteria during construction work. Its quality problems have the following eight traits such as complexity, frequent occurrence, potentiality, chain effect, heavy damages, multiple responsibilities, difficulties of treatment and high expenditure for treatment.     

Development and application of continuouslyvariable transmission test facilities

Basic structure and speed control principles of rubber V belt continuously variable transmissions (CVT) are analyzed. A test bench on which the governing characteristics, carrying capacity, pulley diameters, and transmission efficiency of CVTs can be tested is developed. This test rig permits the measurement of speed, torque and axial displacements of moveable flanges. The experiment not only verifies the results of the theoretical analysis but also reveals the trend of governing characteristics and efficiency affected by the operating condition changes. These conditions include the speed ratio, rotational speed, and external load. Based on this investigation, a method for improving CVT efficiency is proposed. The feasibility of the test bench is demonstrated by the experiment, which has a guiding role for design and parameter matching of CVTs.     

A Sampling Theorem with Compact Support for Wavelet Subspaces

The development of enterprise system undergoes mainly three forms: the system of private business, system of co-operative business and company system. Nowadays, the company system has become the main form for organization of the company property because of its two main features-the multiple principal of the company property right and the position of independent corporate make it more effective than other ones. In this paper, the following is discussed: how a national construction enterprise fulfills the objective of revising and improving the structure of the company ownership by carrying out its reform and standardization with company system.     

凡纳滨对虾高位池能量收支与养殖容量

研究了凡纳滨对虾高位池生态系统的能量转化效率与养殖容量,结果表明：实验虾池浮游植物数量变化范围为3.45×107～1.71×108 cell?L-1。虾池水柱毛初级生产量变化在1.28～11.38 g?m-2?d-1之间。虾池生态系统中毛初级生产量为11573.30 MJ、投饵能为32663.62 MJ、施肥能量为229.71 MJ、放养虾苗折合能量为1.43 MJ,总投入能量为44468.04 MJ;虾池对虾收获能为5269.12 MJ;凡纳滨对虾高位池能量转化效率为11.85％。以氮负荷量估算虾池养殖容量为157万尾?hm-2。     

基于滤食鱼类天然产力的安康库区生态负荷量测定

为厘清汉江水体鱼类集约养殖与生态负荷量的关系,测定安康库区滤食性鱼类天然鱼产力,测算Ⅱ类水质限定条件下的安康库区生态负荷量,并与以水体磷含量为标准的计算结果比较。结果表明,设定网箱深度3 m,单位水体生态负荷量为193.44 g/m³,总产量控制为10.47×10⁴ t。库区网养单产为100 kg/m³时,网箱养殖面积控制为1.93‰,网箱生态养殖面积与单位面积产量呈反比。     

Experimental Technology on Dynamic Wind Loads on a Tall Building

The wind load is a major load on tall buildings from side directions. It is of considerable necessity to building engineering that the static and dynamic wind load and the dynamic wind response can be achieved accurately. Therefore, the model of a tall building in Chongqing is made and tested in wind tunnel by using the high frequency balance used widely home and abroad at present. The characteristics of wind load are studied. This paper gives the coefficients of base force of the building produced by wind load in different wind directions, and offers reference for wind-resistant design of the building.     

Experimental Investigation on Buckling Behaviors of Irregularly Shaped Aluminum Alloy Structural Components Under Axial Compression Load

The experimental and numerical investigations on buckling behaviors of aluminum alloy components with different irregularly shaped sections were carried out. The buckling load carrying capacity obtained through experiments, numerical simulations, and equations described in the design code were compared. Results obtained through experiments and numerical simulations in good agreement, which shows the validation of the numerical model. And the validated FEM model will be used for parametric analysis of buckling behavior of irregularly shaped aluminum alloy structural component. Equations in the design code do not include effects of the buckling type and need to be improved further.     

Analysis and Research on VVT System Control Strategy for Motorcycle Engine

An original variable valve timing mechanism with two-mode intake timing parameters is developed according to the structural characteristics of small-medium displacement motorcycle engine. Based on cycle simulation, a cycle simulation model of VVT mechanism for motorcycle engine is created. The control strategy of variable valve timing and lifting running-model are carried out at idle speed low negative load, middle negative load, low speed high negative load and high speed high negative load. It has been proved that the performance of JH125 motorcycle engine can be effectively improved by loading the new type VVT system.