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Experimental study on bed-load sediment transport under irregular wave and current combined flow

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Acta Oceanologica Sinica 2001年第2期20卷 271-280页

作者： Wu Yongsheng,Qin Chongren (1. Department of Hydraulic engineering, Tsinghua university, Beijing 100084, china 2. school of civil engineering, tianjin university, tianjin 300072, china) Department of Hydraulic engineering Tsinghua University Beijing 100084 China

Using an irregularly oscillating tray and flume, a series of experiments are completed to evaluate bed-load sediment transport rate under irregular wave -current coexistent field. Testing conditions include three interaction angles 0', 45', 90' and two kinds of median sizes (0.38 and 1.10 mm). The results of transport rate show that the net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress of waves, mean shear stress of current and the grain size.

关键词： Irregular wave-current bed-load transport rate

Effect of Water and Sediment Regulation on Lower Yellow River

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Transactions of tianjin university 2009年第2期15卷 113-120页

作者：徐国宾司春棣 school of civil engineering Tianjin University school of Mechanical engineering Shijiazhuang Railway Institute

According to the results of the water and sediment regulations of the Yellow River in year 2002—2007,the effect of erosion and deposition on the lower reaches,the amount and distribution of erosion and deposition in the river mouth area,the adjustment of river regime,the effect of river regulation projects and changes of flowing capacity of the channel are *** is revealed that the water and sediment regulation is efficient to reduce deposition and improve the flowing capacity and the conditions of sediment transport.

关键词： Yellow River water and sediment regulation river control sediment transport

Vertical Upheaval Buckling of Submarine Buried Heated Pipelines with Initial Imperfection

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Transactions of tianjin university 2011年第2期17卷 138-145页

作者：王武刚刘润闫澍旺徐余 school of civil engineering Tianjin University tianjin Architecture Design Institute

In this paper,a theoretical solution of vertical buckling is proposed with regard to the typical initial imperfection cases of submarine *** tools are applied to predicting the occurrence and consequence of inservice buckling of a buried heated pipeline in Bohai *** evaluation is performed to ensure the pipeline structural integrity during operation under loading *** protection measures are proposed and their validities are *** show that for the same magnitude of initial imperfection,the upheaval buckling of pipeline with isolated prop model is the most likely to *** empathetic model represents a special sub-case of continuous prop model,and the calculated buckle temperature is between the first stage and the second stage of post-upheaval buckling of continuous prop *** the larger the initial imperfection,the less the axial force required for the upheaval ***,it can be seen that a peak point appears on the curves of temperature difference against buckling amplitude for small initial ***,trenching-burial is one kind of protection measures preventing the pipeline from thermal *** covered depth-to-diameter ratio depends on the design conditions and subsoil *** the given pipeline in this paper,the covered depth-to-diameter ratio is recommended to be 5.

关键词： submarine buried pipeline thermal stress initial imperfection upheaval buckling protection measure

Mesh Size Effect in Numerical Simulation of Blast Wave Propagation and Interaction with Structures

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Transactions of tianjin university 2008年第6期14卷 396-402页

作者：师燕超李忠献郝洪 school of civil engineering Tianjin University school of civil and Resource engineering The University of Western Australia

Numerical method is popular in analysing the blast wave propagation and interaction with ***,because of the extremely short duration of blast wave and energy trans-mission between different grids,the numerical results are sensitive to the finite element mesh *** numerical simulations show that a mesh size acceptable to one blast scenario might not be proper for another case,even though the difference between the two scenarios is very small,indicating a simple numerical mesh size convergence test might not be enough to guarantee accu-rate numerical ***,both coarse mesh and fine mesh were used in different blast scenarios to investigate the mesh size effect on numerical results of blast wave propagation and interaction with *** on the numerical results and their comparison with field test re-sults and the design charts in TM5-1300,a numerical modification method was proposed to correct the influence of the mesh size on the simulated *** can be easily used to improve the accu-racy of the numerical results of blast wave propagation and blast loads on structures.

关键词： mesh size effect numerical simulation sensitivity blast wave propagation blast load structures

WPT-Based Modal Control on Distributed Structures with MRF-04K Damper

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Transactions of tianjin university 2011年第6期17卷 397-403页

作者：林伟李忠献张根明黄鹏云 school of civil engineering Fuzhou University school of civil engineering Tianjin University

The magnetorheological （MR） fluid damper-based semiactive control systems have received considerable attention for protecting structures against natural hazards such as strong earthquakes and high winds. In this paper, a novel modal controller using wavelet packet transform （WPT） is proposed for the vibration control of distributed structures. In the proposed control system, the WPT method is utilized to decompose the acceleration measurement and select the modes containing most of the WPT energy component as the dominant modes. Then, a modal controller is designed to control the dominant modes and the optimal active control force is solved. Finally, Clipped-optimal con- trol law is adopted to determine the voltage applied to each MR damper. A Kalman-filter observer, which estimates the full controlled modal states from local accelerometer feedbacks, is designed for rendering the controller to be more applicable to distributed structures with a large number of degrees of freedom. A numerical example of a stadium root structure installed with MRF-04K damper is presented. The effectiveness of the controller is evaluated under both tianjin and E1 Centro earthquake excitations. The superior performance and adaptability of the controller for versatile loading conditions are demonstrated through the comparison with traditional truncated modal controller.

关键词： distributed structure modal control semiactive control wavelet packet transform magnetorheological (MR) damper Kalman-filter

Simplified Computation of Reflective Overpressure in Closed Cuboid Space Due to Internal Explosion

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Transactions of tianjin university 2010年第6期16卷 395-404页

作者：田力李忠献周清 school of civil engineering Tianjin University Binzhou Urban Planning and Design Institute

A simplified method is proposed for analyzing the overpressure history of an optional point on the walls of a closed cuboid due to its internal optional point-explosion. Firstly, the overpressure histories of all nodes on the walls of a cube with a side-length of 2 m are computed under a reference-charge explosion at each node of its inner space using the LS-DYNA software, and then are collected to form a reference database. Next, with the thought of the isoparametric finite element, an interpolating algori...

关键词： closed cuboid space reference database reflective overpressure charge weight

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应用蒙特卡罗方法求解一类随机微分方程

天津大学学报（自然科学与工程技术版） 2003年第4期36卷 430-433页

作者：张华练继建刘嘉焜天津大学建筑工程学院天津300072 天津大学理学院天津300072

建立一类随机微分方程初值的概率模型,应用蒙特卡罗(Monte Carlo)法对其抽样产生一组伪随机数,应用四阶龙格库塔(Runge Kutta)法求解随机微分方程.给出了一个实例,求得其解析解和数值解,在计算次数大于50和小于100的条件下,数值解的最... 详细信息

建立一类随机微分方程初值的概率模型,应用蒙特卡罗(Monte Carlo)法对其抽样产生一组伪随机数,应用四阶龙格库塔(Runge Kutta)法求解随机微分方程.给出了一个实例,求得其解析解和数值解,在计算次数大于50和小于100的条件下,数值解的最大相对误差为3.600.

关键词：随机微分方程蒙特卡罗方法四阶龙格—库塔法解析解数值解概率模型

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预应力施加过程中混凝土的徐变变化

天津大学学报（自然科学与工程技术版） 2003年第2期36卷 210-214页

作者：亢景付彭小平天津大学建筑工程学院天津300072 天津住宅建设发展集团有限公司天津300050

结合工程实测资料,对预应力施加过程中混凝土的徐变变化规律进行了探讨和分析.研究结果表明,混凝土在预应力施加过程中产生的徐变应变与应力σ和持荷时间t成直线关系.对于需要数天时间才能完成预应力施加的大型混凝土结构,在进行预应力... 详细信息

结合工程实测资料,对预应力施加过程中混凝土的徐变变化规律进行了探讨和分析.研究结果表明,混凝土在预应力施加过程中产生的徐变应变与应力σ和持荷时间t成直线关系.对于需要数天时间才能完成预应力施加的大型混凝土结构,在进行预应力效果分析时可把整个张拉过程划分为若干个张拉时段和停置时段,分别记录每个时段观测仪器的读数变化,按ε0=α∑σiti来近似计算预应力施加过程中徐变应变.

关键词：预应力结构徐变应变变化

Test on Sensor Effect of Cement Matrix Piezoelectric Composite

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Transactions of tianjin university 2005年第2期11卷 133-136页

作者：杨晓明李忠献丁阳李宗津 school of civil engineering tianjin university tianjin 300072 china Department of civil and Environmental engineering Hong Kong university of Science and Technology Hong Kong

A novel cement matrix smart piezoelectric composite and its application as sensing element are presented.A cement matrix smart piezoelectric composite piece encapsulated in a cement mortar formed a practical sensor, and it was tested on material test system with cyclic *** to the theoretical analysis, the function of the cement matrix piezoelectric sensor output voltage was expressed in terms of the magnitude of the input cyclic loading amplitude and *** curve fitting of gain function that is defined as sensor′s gain factor under different frequencies of input loading was carried out. From the results of curve fitting, it is found that the cement matrix smart piezoelectric composite has a simple relationship between input loading and output *** the cement matrix piezoelectric composite sensor is suitable to be applied in structural health monitoring.

关键词： piezoelectric composite cement matrix sensor structural health monitoring