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Damage and progressive failure of concrete structures using non-local peridynamic modeling

Science China(Technological Sciences) 2011年第3期54卷 591-596页

作者： HUANG Dan1,2, ZHANG Qing1,2 & QIAO PiZhong1,3 1 state Key Laboratory of Hydrology-water Resources and Hydraulic engineering, Hohai University, Nanjing 210098, China 2 department of engineering Mechanics, Hohai University, Nanjing 210098, China 3 department of civil and environmental engineering, washington state University, pullman, wa 99164-2.10, usa 1. state Key Laboratory of Hydrology-water Resources and Hydraulic engineering Hohai University Nanjing 210098 China2. Department of Engineering Mechanics Hohai University Nanjing 210098 China3. Department of Civil and Environmental Engineering Washington State University Pullman WA 99164-2910 USA

Peridynamics (PD), a recently developed theory of solid mechanics, which employs a non-local model of force interaction and makes use of integral formulation rather than the spatial partial differential equations used in the classical continuum mechanics theory, has shown effectiveness and promise in solving discontinuous problems at both macro and micro scales. In this paper, the peridynamics theory is used to analyze damage and progressive failure of concrete structures. A non-local peridynamic model for a rectangular concrete plate is developed, and a central pairwise force function is introduced to describe the interior interactions between particles within some definite distance. Damage initiation, evolution and crack propagation in the concrete model subject to in-plane uni-axial tension, in-plane uni-axial compression and out-of-plane impact load are investigated respectively. The numerical results show that discontinuities appear and grow spontaneously as part of the solution to the peridynamic equations of motion, and no special failure criteria or re-meshing techniques are required, which proves the potential of peridynamic modeling as a promising technique for analyzing the progressive failure of concrete materials and structures.

关键词： concrete damage progressive failure peridynamic model discontinuities

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Self-centering seismic retrofit scheme for reinforced concrete frame structures:SDOF system study

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Earthquake engineering and engineering Vibration 2010年第2期9卷 271-283页

作者： Yunfeng Zhang and Xiaobin Hu department of civil and environmental engineering,University of Maryland,College Park,MD 20742,usa department of civil and environmental engineering University of Maryland College Park 20742 USA

This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.

关键词： earthquake reinforced concrete frame structure nonlinear analysis SDOF system seismic retrofit self-centering

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Effects of Reducing River Flow on Pulse Residence Time in Little Manatee River,usa

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Transactions of Tianjin University 2009年第2期15卷 95-100页

作者： HUANG Wenrui,LIU Xiaohai(department of civil engineering,Florida state University,Tallahassee,Florida 32.10-6046,usa) department of civil engineering Florida State University Tallahassee Florida 32310-6046 USA

Residence time is an important indicator for river environmental *** this paper,a 3D hydrodynamic model has been successfully applied to Little Manatee River to characterize the mixing and transport process and residence *** model employs horizontal curvilinear orthogonal grids to represent the complex river system that consists of branches and *** model has been satisfactorily calibrated and verified by using two continuous data *** data sets consist of hourly observations of all forcing boundaries,including freshwater inputs,tides,winds,salinity and temperatures at bay boundary,and air temperatures for model *** data sets also consist of hourly observations of water levels,salinity,and temperature at several river *** calibrated and verified hydrodynamic model was used to predict residence time in the Little Manatee *** the minimum flow of 0.312.m3/s,the pulse residence time(PRT) is 108 *** simulations were also conducted for 17 flow *** regression equations have been satisfactorily derived to correlate PRT to freshwater *** coefficient R2 is 0.982 for PRT.

关键词： hydrodynamic modeling estuary residence time tidal river

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TWO MODELS FOR ROLL waVES IN A MUD LAYER

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Journal of Hydrodynamics 1995年第2期7卷 1-16页

作者： Chiang C. Mei Ko-fei Liu Chiu-on Ng(department of civil and environmental engineering Massachusetts Institute of Technology,Cambridge,MA usa) Massachusetts Inst of Technology Cambridge United States

As has been extensively reported by hydraulic engineers in China, the flow of hyperconcentrated fluid mud in rivers is often pulsating and appears as roll waves. We report here two theories for such pulsating flows besed on two constitutive laws: the power law and Bingham plastic law. In order to account for the nonlinear bores convective inertia is kept in the approximate long wave equations. Kar man's momentum integral method with an assumed velocity profile is then employed. Results of the linearized instability analyses are *** bores are obtained either as stationary wave solutions or as the long- time limit of unstable disturbances which are initially infinitesimal. Implications on ho scour is examined.

关键词： hyperconcentrated fluid mud pulsating flow power law Bingham plastic Law

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COMPARISON OF SCOURS IN FRONT OF VERTICAL BREAKwaTERS DUE TO REGULAR AND IRREGULAR waVES

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Journal of Hydrodynamics 2000年第1期12卷 1-7页

作者： Gao Xue ping department of civil and environmental engineering, Faculty of engineering, Ehime University, 3 Bunkyo cho, Matsuyama 790 77, JapanKunimitsu Inouchi Center for Cooperative Research and Development, Ehime University, 3 Bunkyo cho, Mats Ehime Univ Matsuyama Japan

In this paper the scours of sand bed due to regular and irregular waves in front of vertical breakwaters, such as scouring patterns, scouring mechanisms, etc., are investigated. Thereby, the scours under the action of... 详细信息

关键词： scours regular waves irregular waves

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Effect of Limestone Powder and Fly Ash on Magnesium Sulfate Resistance of Mortar

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Journal of Wuhan University of Technology(Materials Science) 2010年第4期25卷 700-703页

作者：刘数华 state Key Laboratory of water Resources and Hydropower engineering Science Wuhan University

The effect of limestone powder and fly ash on magnesium sulfate resistance of mortar was studied by testing on the strength, expansion and hydration products of the specimens stored in MgSO4 solution at certain periods. The experimental results show that the strength of mortar stored in MgSO4 solution increases a little before 28 d, but decreases fast subsequently. The more the contents of limestone powder and fly ash, the less the strength losses. Mortar swells in the MgSO4 solution with the soaking time. And the more the contents of limestone powder and fly ash, the less the expansion rate is. The expansion or strength loss of mortars results from the expansion of gypsum, as well as the loss of Ca（OH）2 and other hydration products of cement. The magnesium sulfate resistance of the mortars containing limestone powder and fly ash is high.

关键词： limestone powder fly ash mortar magnesium sulfate resistance

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A land surface model incorporated with soil freeze/thaw and its application in GAME/Tibet

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Science China Earth Sciences 2006年第12期49卷 1311-1322页

作者： HU Heping1, YE Baisheng2, ZHOU Yuhua3 & TIAN Fuqiang1 1. department of Hydraulic engineering, Tsinghua University, Beijing 100084, China 2. Cold and Arid Regions environmental and engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China 3. department of civil engineering, Massachusetts Institute of Technology, usa 1. department of Hydraulic engineering Tsinghua University Beijing 100084 China 2. Cold and Arid Regions environmental and engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China 3. department of civil engineering Massachusetts Institute of Technology USA

Land surface process is of great importance in global climate change, moisture and heat exchange in the interface of the earth and atmosphere, human impacts on the environment and eco- system, etc. Soil freeze/thaw plays an important role in cold land surface processes. In this work the diurnal freeze/thaw effects on energy partition in the context of GAME/Tibet are studied. A sophisti- cated land surface model is developed, the particular aspect of which is its physical consideration of soil freeze/thaw and vapor flux. The simultaneous water and heat transfer soil sub-model not only reflects the water flow from unfrozen zone to frozen fringe in freezing/thawing soil, but also demon- strates the change of moisture and temperature field induced by vapor flux from high temperature zone to low temperature zone, which makes the model applicable for various circumstances. The modified Picard numerical method is employed to help with the water balance and convergence of the numerical scheme. Finally, the model is applied to analyze the diurnal energy and water cycle char- acteristics over the Tibetan Plateau using the Game/Tibet datasets observed in May and July of 1998. Heat and energy transfer simulation shows that: (i) There exists a negative feedback mechanism between soil freeze/thaw and soil temperature/ground heat flux; (ii) during freezing period all three heat fluxes do not vary apparently, in spite of the fact that the negative soil temperature is higher than that not considering soil freeze; (iii) during thawing period, ground heat flux increases, and sensible heat flux decreases, but latent heat flux does not change much; and (iv) during freezing period, soil temperature decreases, though ground heat flux increases.

关键词： land surface model,soil freeze/thaw,GAME/Tibet,simultaneous liquid,vapor and heat transfer.

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A NEW METHOD IN GROUNDwaTER FLOW MODELING

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Journal of Hydrodynamics 2009年第2期21卷 245-254页

作者： MA Xiu-yuan LI Shu-guang ZHU Wei-shen School of civil engineering Shandong University Jinan 250061 China department of civil and environmental engineering Michigan State University East Lansing Michigan 48834USA

One of the challenges in groundwater modeling is the prediction of hydraulic head related to local stress fluctuations with a regional scale model. Typical applications of numerical models require extensive field information for input data and for calibration If we can model the change directly, we may not have to know all the modeling parameters because sometimes the changes only depend on fewer parameters. In this article, we present an improved methodology for groundwater modeling related to local stress fluctuations using a perturbation approach. Our results demonstrate that this approach is capable of matching an exact solution for drawdown in both confined and unconfined aquifers. The results suggest that this perturbation method can provide an accurate representation of head in a large-scale hydrogeological system.

关键词： groundwater modeling local stress fluctuations perturbation method iteration scheme

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One-dimensional numerical models of higher-order Boussinesq equations with high dispersion accuracy

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Acta Oceanologica Sinica 2003年第2期22卷 287-300页

作者： ZouZhili wangTao ZhangXiaoli DarrenSpratt stateKeyLaboratoryofCoastalandOffshoreengineering DepartmentofCivilEngineeringDalianUniversityofTechnologyDalian116024China civilandenvironmentalengineering UniversityofIllinoisatUrbana-ChampaignChampaignUSA

Nonlinear water wave propagation passing a submerged shelf is studied experimentally and numerically. The applicability of the wave propagation model of higher-order Boussinesq equations derived by Zou (2000, Ocean engineering, 27, 557 - 575) is investigated. Physical experiments are conducted; three different front slopes (1:10, 1 = 5 and 1:2) of the shelf are set-up in the experiment and their effects on the wave propagation are investigated. Comparisons of the numerical results with test data are made and the higher-order Boussinesq equations agree well with the measurements since the dispersion of the model is of high accuracy. The numerical results show that the good results can also be obtained for the steep-slope cases although the mild-slope assumption is employed in the derivation of the higher-order terms in the higher-order Boussinesq equations.

关键词： water waves Boussinesq nonlinear dispersion

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FROM YELLOW RIVER MODELSTO MODELING OF RIVERS

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International Journal of Sediment Research 1999年第2期14卷 85-93页

作者： Ben Chie YEN (water Resources engineering, department of civil and environmental engineering, University of Illinois at Urbana-Champaign, 205 North Mathews Avenue, Urbana, IL 61801 usa)

The Yellow River in China is a heavily sediment-laden river that challenges the best minds to understand its hydraulic behavior. Scientific scale modeling of the river was first carried out in Germany, separately by Engels and Franzuis, in the early 1930s. It was the major river modeling at that time, and the disagreement between their results had profound effect on the regulations of the river and on later physical river hydraulic modeling. The background leading to the Yellow River models and the conditions of the experimental results are reviewed in this paper. Finally, issues related to numerical and physical modeling of rivers are discussed.

关键词： River modeling Yellow River Physical models Numerical models

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