Papers by Keyword: Time-Effect

Abstract: The management structure that the paper discussed is from the equipment maintenance unit. The structure is the base and support system of the unit. The optima design of the structure possess the basal position in unit management .Based on the theory of entropy, this paper analyses the influence of system management structure on the system information flow. It evaluated the order degree of system management structure in view of information, introduced two concepts: time- effect and quality of information flow and established the Time Effect-Quality Model (TEQM). With TEQM, it is possible to optimize and quantitatively evaluate the system management structure. In addition, the paper also supplies detailed calculating steps of order degree of system management structure, and provides an example at the end.

Abstract: The mechanical behavior of prestressing, temperature ,creep & shrinkage in construction procedure are studied, then construction analysis are integrated into structural nonlinear analysis by defining construction procedure as state nonlinear. The “time effect” and “route effect” are defined in large-scale structure, and their essences are studied with a general format of displacement method.

Abstract: The dissipating of pore water pressure caused by pile sinking is one of the main factors resulting in time effect of ultimate bearing capacity of pile.The pore water pressure is monitored at each observing point during pile sinking and after that. With the pore pressure plan embedded in advance, by means of spot test in the process of pile sinking, under this geological conditions of the pile foundation by referring to the second phase project of the free port logistics processing zone in Dongjiang, Tianjin.The change law of the distribution and dissipation of excess pore water pressure with time, depth, radial distance and permeability coefficient of soil was also discussed. It’s found that the excess pore water pressure attenuates approximately linearly with the increase of the distance from the pile heart and the scope influenced is around 10d. As the numerical simulation accord with the test results effectively, promote the results then get the change rule of pile bearing capacity with time.The formula of pile bearing capacity about time effect in dredge fill was deduced for engineering reference.The effect of soil internal friction angle on the ultimate bearing capacity of pile was discussed. Numerical simulation shows that the ultimate bearing capacity of pipe pile increases over time and keeps stable after 20d.The ultimate limit bearing capacity is 1473kN with increase of 12.3%, the time when it reaches the stable state is in accord with the excess pore water pressure dissipation monitored at each observing point. The larger the internal frictional angle of soil becomes, the more the ultimate bearing capacity is. The angle exceeding 20°,the bearing capacity would not increase as internal frictional angle of soil increases.

Abstract: More detailed information about the bearing capacity and integrity of the pile can be obtained by high strain dynamic test than by dead-load test [1]. Engineering examples show that the bearing capacity of the prestressed pipe pile gradually increase with the growth of the resting time, and the ultimate bearing capacity of the pile can reach up to 2 times more than the initial bearing capacity. Through the study of the time effect mechanism, it is found that the increment of ultimate bearing capacity of the single pile is mainly caused by side soil resistance. The end resistance has little influence on the time effect of bearing capacity of pile.

Abstract: The effects of creep and shrinkage of concrete is non-ignorable to strength of steel and concrete composite beams under sustained load, and the relative slippage should be considered for internal force. Time-dependent modulus method is presented, formulas of the stress and strain at any time are deduced considering creep, shrinkage and the relative slippage. The variational stress is analysed of the steel and concrete composite beams under sustained load.

Abstract: Through the study on the characteristics of bearing capacity of jacked pile in soft soil, it is found that the increment of ultimate bearing capacity of the single pile is mainly determined by pile side resistance. The end resistance has little influence on the time effect of bearing capacity of pile. The relationship between ultimate bearing capacity and time can be expressed with logarithmic curve. According to penetration mechanism of jacked pile, the expansion of a series of spherical cavities in semi-infinite space is used to simulate the process of pile installation. Soil is assumed as Mohr-Coulomb material. Based on the theory of spherical cavity expansion, estimating formulas were proposed to calculate the ultimate side frictional resistance. Then the ultimate bearing capacity of single pile in different time can be obtained. Analyses show that the calculation results are close to the measured data and the error between computed and measured value is little. So it is acceptable for the formula to forecast bearing capacity of jacked piles.

Abstract: Coal char combustion under the O₂/CO₂ atmosphere is one of the prospect cleaner coal technologies, its combustion characteristics and dynamics research are the foundations of project application. In this paper, the results of a study on the combustion characteristics of three coal chars ( Liupanshui lignite, Zhungeer bituminous ,Qinhuangdao anthracite) under different oxygen volume content （21%、25%、30%、35%）are presented by TGA, the effect of oxygen volume content to coal-char reaction were analyzed. Simultaneously classical dynamics and time effect fractal dynamics had carried on the analysis separately to the coal char combustion. The results showed that, with higher the oxygen content, the lower the ignition、burnout temperatures are, the char combustion time shorten, activation energy reduces slightly whether use classical dynamics or time effect dynamics analysis, and the activation energy obtained by the former is smaller than the latter.

Abstract: The static load test of 34 jacked-in PHC pipe piles of medium length are performed in the cohesive soil area, the relationship between the vertical ultimate bearing capacity and the final pressure, and the time effect of vertical bearing capacity of the jacked-in PHC pipe pile are studied. The data of static load test is analyzed statistically with software SPSS, the regional empirical coefficient about the vertical ultimate bearing capacity and final pressure, and the time effect formula about vertical bearing capacity of the jacked-in PHC pipe pile in the cohesive area are obtained. According to the regional empirical coefficient, the pile pressing machine and counterweight can be chosen reasonably and the vertical ultimate bearing capacity of single pile can also be estimated rapidly, then we can instruct the design and construction of the jacked-in PHC pipe pile. According to the time effect formula, the vertical bearing capacity at different periods of the jacked-in PHC pipe pile can be obtained, the cost of the foundation engineering can be reduced by considering the time effect influence to the vertical bearing capacity of the jacked-in PHC pipe pile.

Abstract: This paper presents the monitoring records of the deformation on the North Slope of Lishan Mountain in Lintong County, Shanxi, China. On the basis of the monitoring results on the site and the creep tests on the soil samples, the mechanism of the potential dangerous landslide was analyzed. The existence of lock segment in the slope and its time effect are regarded as the important controlling factors in the development process of Lishan potential landslide which has the possibility of becoming a rapid disastrous landslide.

Abstract: In the re-pressed tests of jacked pipe piles in soft clay, it was observed that the re-pressed starting pressure can reach to more than 2.5 times of the final pressure for 25 days after finishing the installation; and it increased more rapidly in early period than later. Through the study of the time effect mechanism, it is found that the increment of ultimate bearing capacity of the single pile is mainly caused by side soil resistance. The end resistance has little influence on the time effect of bearing capacity of pile. According to the simulation result of the test data, the relationship between pile side resistance and time can be described with logarithmic curve. By this new computing model, the side frictional resistance in different resting time can be obtained, and then the ultimate bearing capacity. It is proved that this method is feasible because the values of side soil resistance calculated by the computing model with software are well consistent with the field tests results.