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Life-Cycle Bearing Capacity for Pre-Stressed T-beams Based on Full-Scale Destructive Test

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Structural Durability & Health Monitoring 2025年第1期19卷 145-166页

作者： Yushan Ye Tao Gao Liankun Wang Junjie Ma Yingchun Cai Heng Liu Xiaoge Liu China construction Seventh engineering Division Corp. Ltd.Zhengzhou450004China School of water conservancy and Transportation Zhengzhou UniversityZhengzhou450001China

To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concrete T-beams,destructive tests were conducted on full-scale pre-stressed concrete *** on the measurement and ana-lysis of beam deﬂection,strain,and crack development under various loading levels during the research tests,combined with the veriﬁcation coefﬁcient indicators speciﬁed in the codes,the veriﬁcation coefﬁcients of bridges at different stages of damage can be *** results indicate that the T-beams experience complete,incom-plete linear,and non-linear stages during the destructive test *** the complete linear elastic stage,both the deﬂection and bottom strain veriﬁcation coefﬁcients comply with the speciﬁcations,indicating a good structural load-bearing capacity no longer adheres to the code’s *** the non-linear stage,both coefﬁcients exhi-bit a sharp increase,resulting in a further decrease in the structure’s load-bearing *** to the pro-visions of the current code,the beam can be in the incomplete linear stage when both values fall within the code’s speciﬁed *** strain veriﬁcation coefﬁcient sourced from the compression zone at the bottom of theﬂange is not recommended for assessing the bridge’s load-bearing capacity.

关键词： Pre-stressed T-beams whole process destructive test bearing capacity veriﬁcation coefﬁcient

Ski-jump trajectory based on take-off velocity

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Journal of Hydrodynamics 2016年第1期28卷 166-169页

作者：吴建华许准姚莉马飞 college of water conservancy and Hydropower engineering Hohai University college of water conservancy and Ecological engineering Nanchang Institute of Technology

The theoretical method estimating ski-jump trajectory was paid attention to and modified. The present method is based on the effects of the take-off velocity and the angle in the sensitivity analysis of parameters. The experiments are conducted for a triangular-shaped flip bucket in order to reveal the relationships between the take-off velocity and its influencing factors. The results show that, the take-off velocity has a much larger effect on the impact point than the take-off angle. The take-off velocities of both upper and lower trajectories are all functions of the approach flow Froude number, the deflector height and the deflection angle, especially, the results of the deflection angle of 25° could be directly used when this angle is larger than 25° Meanwhile, this method is checked and the maximum relative errors of both U calx and L_（calx） are 5.1% and 5.6%, respectively.

关键词： trajectory triangular-shaped flip bucket take-off velocity sensitivity analysis of parameters

Fin characteristics of aerator devices with lateral deflectors

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Journal of Hydrodynamics 2013年第2期25卷 258-263页

作者：吴建华李丹马飞钱尚托 college of water conservancy and Hydropower engineering Hohai University

The fins will be formed if the lateral deflectors in the side-walls with a bottom aerator device are improperly designed, and the flow regime downstream of the aerator device will be worsened. In this paper, the height and the length of the fins induced by the lateral deflectors are theoretically analyzed along with their influencing factors, and the fin characteristics are experimentally investigated on the basis of the theoretical analysis. It is shown that the intensities of the fins are strongly dependent on the ratio of the lateral cavity length to the bottom cavity length, and other factors, like the working head, the height and the angle of the lateral deflector, the flow Froude number around the aerator device, affect the fins indirectly through the changes of the lateral cavity length. When an aerator device with lateral deflectors is designed, it is crucial to match the above mentioned ratio, and to make the ratio of the two cavity lengths less than 1.0 in order to avoid the generation of the fins.

关键词： aerator cavity length fin lateral deflector

Influence of flow field on stability of throttled surge tanks with standpipe

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Journal of Hydrodynamics 2013年第2期25卷 294-299页

作者：安建峰张健俞晓东陈胜 college of water conservancy and Hydropower engineering Hohai University

The steady-state flow field characteristics have important effects on the stability of the throttled surge tank with the standpipe. This paper analyzes these effects on the basis of the numerical simulation of the flow field by using the Computational Fluid Dynamics （CFD） method. It is shown that the anticlockwise recirculation zone is formed in the standpipe, which affects the local head loss at the junction of the standpipe with the pipeline. The variation of the head loss coefficient at the junction is linearly related with the diameter ratio of the standpipe to the pipeline. The dimensionless recirculation flow rate is proportional to the square of the diameter ratio. Considering the effects of the recirculation zone, an empirical expression of the critical stability area is obtained. Comparing with the Thoma critical area, the area obtained by the present method is smaller, and the reduction depends on the diameter ratio and the ratio of the velocity head to the head losses in the tunnel. words：

关键词： critical stability area throttled surge tank Computational Fluid Dynamics (CFD) simulation turbulence model flow field

Inception point of air entrainment over stepped spillways

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Journal of Hydrodynamics 2013年第1期25卷 91-96页

作者： WU Jian-hua ZHANG Bin MA Fei college of water conservancy and Hydropower engineering Hohai University

The location of the inception point of the air entrainment directly affects the energy dissipation ratio, the cavitation damage control, and the training wall height designs for a stepped spillway and a stilling basin. In this paper, the boundary layer theory of plates is used to predict the location of the inception point of the air entrainment over the stepped spillways by assuming the steps on the spillways as a kind of roughness. An empirical formula is presented based on the physical model experiments, with the maximum error less than 1% except at one point where the error is 1.6%, as compared to the experimental data. Meanwhile, it is shown that the location of the inception point of the air entrainment for the stepped spillway is much nearer to the top of the spillway than that for a smooth spillways, which explains why the high ratio of the energy dissipation is provided for the stepped spillway.

关键词： air entrainment cavitation energy dissipation inception point stepped spillway unit discharge

Large-eddy simulation of suspended sediment transport in turbulent channel flow

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Journal of Hydrodynamics 2013年第1期25卷 48-55页

作者： ZHU Hai WANG Ling-ling TANG Hong-wu college of water conservancy and Hydropower engineering Hohai University

The numerical simulation of the non-cohesive sediment transport in a turbulent channel flow with a high concentration is a challenging but practical task. A modified coherent dynamic eddy model of the Large Eddy Simulation （LES） with a pick-up function is used in the present study to simulate the sediment erosion and the deposition in a turbulent channel flow. The rough wall model is used instead of the LES with the near-wall resolution to obtain the reasonable turbulent flow characteristics while avoiding the high costs in the computation. Good results are obtained, and are used to analyze the sediment transport properties. The results show that the streamwise vortices play an important role in the riverbed erosion and the sediment pick-up, which may serve as guidelines for the sediment management and the water environment protection engineering.

关键词： Large Eddy Simulation (LES) sediment suspension pick-up function turbulent channel flow

Investigation of fluid flow-induced particle migration in granular filters using a DEM-CFD method

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Journal of Hydrodynamics 2014年第3期26卷 406-415页

作者：黄青富詹美礼盛金昌罗玉龙速宝玉 college of water conservancy and Hydropower engineering Hohai University

In embankments and earth dams, the granular filter used to protect the base soil from being eroded by the fluid flow is a major safety device. In this paper, the migration mechanism of the base soil through this type of filters with a fluid flow in the base soil-filter system is studied by using the coupled distinct element method and computational fluid dynamics（DEM-CFD） model. The time-dependent variations of the system parameters such as the total eroded base soil mass, the distribution of the eroded particles within the filter, the porosity, the pore water pressure, and the flow discharge are obtained and analyzed. The conceptions of the trapped particle and the trapped ratio are proposed in order to evaluate the trapped condition of the base soil particles in the filter. The variation of the trapped ratio with time is also analyzed. The results show that the time evolutions of the parameters mentioned above are directly related to the gradation of the filter, which is defined as the representative particle size ratio of the base soil to the filter using an empirical filter design criterion. The feasibility of the model is validated by comparing the numerical results with some experimental and numerical results.

关键词： base soil-filter system distinct element method trapped ratio representative particle size ratio

Stochastic simulation of fluid flow in porous media by the complex variable expression method

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Journal of Hydrodynamics 2013年第2期25卷 215-225页

作者：宋会彬詹美礼盛金昌罗玉龙 college of water conservancy and Hydropower engineering Hohai University

A stochastic simulation of fluid flow in porous media using a complex variable expression method （SFCM） is presented in this paper. Hydraulic conductivity is considered as a random variable and is then expressed in complex variable form, the real part of which is a deterministic value and the imaginary part is a variable value. The stochastic seepage flow is simulated with the SFCM and is compared with the results calculated with the Monte Carlo stochastic finite element method. In using the Monte Carlo method to simulate the stochastic seepage flow field, the hydraulic conductivity is assumed in three different probability distributions using random sampling method. The obtained seepage flow field is examined through skewness analysis, and the skewed distribution probability density function is given. The head mode value and the head comprehensive standard deviation are used to represent the statistics of calculation results obtained by the Monte Carlo method. The stochastic seepage flow field simulated by the SFCM is confirmed to be similar to that given by the Monte Carlo method from numerical aspects. The range of coefficient of variation of hydraulic conductivity in SFCM is larger than used previously in stochastic seepage flow field simulations, and the computation time is short. The results proved that the SFCM is a convenient calculating method for solving the complex problems.

关键词： seepage flow field complex variable expression method (SFCM) stochastic seepage flow Monte Carlo method skewed distribution

Transient air-water flow patterns in the vent tube in hydropower tailrace system simulated by 1-D-3-D coupling method

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Journal of Hydrodynamics 2018年第4期30卷 715-721页

作者：王希晨张健俞晓东陈胜 college of water conservancy and Hydropower engineering Hohai University

The vent tube is commonly used for the water hammer protection in the hydropower tailrace system. In transient processes, with air entering and exiting the vent tube, one sees complex hydraulic phenomena, which threaten the station＇s safe operation. It is necessary to investigate the transient mechanisms in the tailrace system with vent tube. In this paper, a 3-D, two-phase numerical model of a vent tube on the connection of the tailrace tunnel and the diversion tunnel, is developed based on the FLUENT with the volume of fluid（VOF） algorithm to investigate the transient air-water flow patterns and the complex hydraulic phenomena in the vent tube of the tailrace system. A 1-D and 3-D unidirectional adjacent coupling（1-D-3-D-UAC） approach with a linear interpolation method is adopted to adjust the timesteps between the 1-D model and the 3-D model on the tunnel inlet and outlet boundaries through the user defined function（UDF）, to transmit the data from the 1-D model to the 3-D model. The model is verified by comparing the results obtained by using the 1-D model alone and from the experiments in literature. The transient flow processes under the full load rejection consist of four stages： the water level dropping stage, the air entering stage, the air pocket collapsing stage, and the air exiting stage. Detailed hydraulic phenomena in the air pocket collapsing process are also discussed.

关键词： Vent tube tailrace tunnel two phase volume of fluid (VOF) 1-D-3-D coupling