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| 1 | Numerical simulation of mechanisms of deformation,failure and energy dissipation in porous rock media subjected to wave stresses显示文摘The pore characteristics,mineral compositions,physical and mechanical properties of the subarkose sandstones were acquired by means of CT scan,X-ray diffraction and physical tests.A few physical models possessing the same pore characteristics and matrix properties but different porosities compared to the natural sandstones were developed.The 3D finite element models of the rock media with varied porosities were established based on the CT image processing of the physical models and the MIMICS software platform.The failure processes of the porous rock media loaded by the split Hopkinson pressure bar(SHPB) were simulated by satisfying the elastic wave propagation theory.The dynamic responses,stress transition,deformation and failure mechanisms of the porous rock media subjected to the wave stresses were analyzed.It is shown that an explicit and quantitative analysis of the stress,strain and deformation and failure mechanisms of porous rocks under the wave stresses can be achieved by using the developed 3D finite element models.With applied wave stresses of certain amplitude and velocity,no evident pore deformation was observed for the rock media with a porosity less than 15%.The deformation is dominantly the combination of microplasticity(shear strain),cracking(tensile strain) of matrix and coalescence of the cracked regions around pores.Shear stresses lead to microplasticity,while tensile stresses result in cracking of the matrix.Cracking and coalescence of the matrix elements in the neighborhood of pores resulted from the high transverse tensile stress or tensile strain which exceeded the threshold values.The simulation results of stress wave propagation,deformation and failure mechanisms and energy dissipation in porous rock media were in good agreement with the physical tests.The present study provides a reference for analyzing the intrinsic mechanisms of the complex dynamic response,stress transit mode,deformation and failure mechanisms and the disaster mechanisms of rock media. | JU Yang1,2,WANG HuiJie1,YANG YongMing1,HU QinAng3 & PENG RuiDong1 1 State Key Laboratory of Coal Resources and Safe Mining,Beijing Key Laboratory of Fracture and Damage Mechanics of Rock and Concrete,China University of Mining and Technology,Beijing 100083,China 2 Department of Mechanical and Manufacturing Engineering,University of Calgary,Calgary,Alberta,T2N 1N4,Canada 3 School of Environment and Civil Engineering,College of Engineering,Oklahoma State University,Stillwater,OK 74078,USA | 2010 | Science China(Technological Sciences)2010，53，4： | 32 |
| 2 | Energy analysis for damage and catastrophic failure of rocks显示文摘The development history and current state of studies on the characteristics and mechanisms of deformation and failure of rock materials were briefly reviewed from the viewpoint of energy.The main scope and the achievable objectives of the energy-based research system were expatiated.It was validated by experiments that the damage process of rocks can be well described by the rock damage evolution equation established based on energy dissipation.It was found from the uniaxial compression and biaxial compression tests that only a small proportion of the total input energy in hard rocks is dissipated before peak load and a large proportion in soft rocks is dissipated before peak load.For both hard and soft rocks,the energy dissipated after peak load accounts for a greater proportion.More energy would be required for rock failure under equal biaxial compression than under unequal biaxial compression.The total absorbed energy is different for rock failure under high-rate loading and low-rate loading.More fragmented failure pattern usually corresponds to higher energy absorption.The mesoscopic analysis on the damage and failure of bedded salt rocks showed that the energy dissipation is prominent and the total absorbed energy for rock failure is low when cracks propagate in the weak mud interlayer while it is contrary when cracks propagate in the salt rock.The energy accumulation,transfer,dissipation and release during the failure process of tunnel with impending failure under disturbance were analyzed theoretically based on the elastoplastic mechanics theory.Furthermore,the spatial distribution of energy dissipation and energy release of fractured rocks under unloading was simulated numerically.It was demonstrated that energy is likely to be released from the weakest surface under compression,which triggers the global failure of rocks. | XIE HePing 1,2,LI LiYun 2,1,JU Yang 2,PENG RuiDong 2 & YANG YongMing 2 1 Sichuan University,Chengdu 610065,China 2 State Key Laboratory of Coal Resources and Safe Mining,Beijing Key Laboratory of Fracture and Damage Mechanics of Rock and Concrete,China University of Mining and Technology,Beijing 100083,China | 2011 | Science China(Technological Sciences)2011，54，S1： | 29 |
| 3 | Smart Behavior of Carbon Fiber Reinforced Cement-based Composite显示文摘The electrical characteristics of cement-based material can be remarkably improved by the addition of short carbon fibers.Carbon fiber reinforced cement composite (CFRC) is an intrinsically smart material that can sense not only the stress andstrain, but also the temperature. In this paper, variations of electrical resistivity with external applied load, and relationof thermoelectric force and temperature were investigated. Test results indicated that the electrical signal is related to theincrease in the material volume resistivity during crack generation or propagation and the decrease in the resistivity duringcrack closure. Moreover, it was found that the fiber addition increased the linearity and reversibility of the Seebeck effect inthe cement-based materials. The change of electrical characteristics reflects large amount of information of inner damage andtemperature differential of composite, which can be used for stress-strain or thermal self-monitoring by embedding it in theconcrete structures. | Wu YAO, Bing CHEN Keru WUState Key Laboratory of Concrete Materials Research, Tongji University, Shanghai 200092, China | 2003 | Journal of Materials Science & Technology2003，19，3： | 13 |
| 4 | Structural condition assessment of long-span suspension bridges using long-term monitoring data显示文摘这份报纸集中于用监视系统的结构的健康测量的长期的监视数据开发一种联机结构的条件评价技术。为 Runyang 暂停桥的频率温度和横梁结束排水量温度的季节的关联首先被执行。然后,用一个六顺序的多项式的一种统计建模技术进一步被使用提出频率温度和排水量温度,测量频率和排水量的反常变化用吝啬的价值控制图表从被检测的关联。分析结果证明更高的颤动模式和排水量的形式的频率与环境温度和建议方法展览有显著季节的关联为检测形式的频率和排水量的微导致损坏的变化的一个好能力。结果证明建议方法能有效地从频率和排水量时间系列消除温度复杂并发症并且很好适合长跨度的暂停桥监视的联机状况。监视的关键词结构的健康 - 形式的频率 - 横梁结束排水量 - 温度 - 季节的关联 - 暂停桥牌旁边支持了:在资助号码下面的中国的国家自然科学基础 50725828 与号码 50808041;不到资助号码 200802861011 的中国的教育部的博士节目基础;东南大学在下面的研究生院的科学研究基础资助没有。 | Deng Yang~+,Ding Youliang~(++) and Li Aiqun~§Key Laboratory of Concrete & Prestressed Concrete Structures of Ministry of Education,Southeast University,Nanjing 210096,China PhD Student ++ Assistant Professor ~§Professor | 2010 | Earthquake Engineering and Engineering Vibration2010，9，1： | 12 |
| 5 | Study on correlations of modal frequencies and environmental factors for a suspension bridge based on improved neural networks显示文摘By using of long-term monitoring data of Runyang Suspension Bridge,the improved back-propagation neural networks (BPNNs) are formulated for modeling the correlations between modal frequencies and environmental conditions including wind,temperature and vehicle load.Then,with the correlation models the environmental effects on modal frequencies are quantified and the abnormal changes of measured frequencies are detected by means of the hypothesis tests.Analysis results reveal that BPNN-based correlation models improved by both early stopping and Bayesian regularization techniques exhibit excellent generalization capability.And the developed correlation models can effectively reduce the environmental variability in modal frequencies.The t-test method provides a good capability to detect the damage-induced 0.16% and 0.12% abnormal changes of the 5th and 6th modal frequencies,respectively.Hence,the proposed method is suitable for real-time monitoring of suspension bridge conditions. | DING YouLiang,DENG Yang & LI AiQun Key Laboratory of Concrete and Prestressed Concrete Structure of Ministry of Education,Southeast University,Nanjing 210096,China | 2010 | Science China(Technological Sciences)2010，53，9： | 9 |
| 6 | Experimental study of dynamic mechanical properties of reactive powder concrete under high-strain-rate impacts显示文摘The dynamic mechanical properties of reactive powder concrete subjected to compressive impacts with high strain rates ranging from 10 to 1.1×102 s-1 were investigated by means of SHPB (split-Hopkinson-pressure-bar) tests of the cylindrical specimens with five different steel fiber volumetric fractions.The properties of wave stress transmission,failure,strength,and energy consumption of RPC with varied fiber volumes and impact strain rates were analyzed.The influences of impact strain rates and fiber volumes on those properties were characterized as well.The general forms of the dynamic stress-strain relationships of RPC were modeled based on the experimental data.The investigations indicate that for the plain RPC the stress response is greater than the strain response,showing strong brittle performance.The RPC with a certain volume of fibers sustains higher strain rate impact and exhibits better deformability as compared with the plain RPC.With a constant fiber fraction,the peak compressive strength,corresponding peak strain and the residual strain of the fiber-reinforced RPC rise by varying amounts when the impact strain rate increases,with the residual strain demonstrating the greatest increment.Elevating the fiber content makes trivial contribution to improving the residual deformability of RPC when the impact strain rate is constant.The tests also show that the fiber content affects the peak compressive strength and the peak deformability of RPC in a different manner.With a constant impact strain rate and the fiber fraction less than 1.75%,the peak compressive strength rises with an increasing fiber volume.The peak compressive strength tends to decrease as the fiber volume exceeds 1.75%.The corresponding peak strain,however,incessantly rises with the increasing fiber volume.The total energy Edisp that RPC consumed during the period from the beginning of impacts to the time of residual strains elevates with the fiber volume increment as long as the fiber fraction is not larger than 2%.It turns to decrease if the fiber volume exceeds 2%.The added fibers make various contributions to enhancing the capability of RPC to consume energy at different loading stages.If the fiber fraction is not larger than 2%,the added fibers make more contribution to enhancing the energy consumption ability of RPC in the period before the peak strain than in the period after the peak strain.The impact strain rate,however,distinctively affects the total energy that RPC consumed and the energy consumed in the different loading periods.The higher the impact strain rate,the more the energy consumed in the stages and therefore the higher the dynamic impact toughness.The empirical relationships of the peak compressive strength,corresponding peak strain,residual strain,total consumed energy and the energy consumed in the varied periods with the impact strain rate and the fiber fraction are derived.Four generalized forms of the dynamic impact stress-strain responses of RPC are formulated by normalizing stresses and strains as the generalized coordinates and by taking account of the influences of impact strain rates and fiber volumetric fractions. | JU Yang1,2,LIU HongBin1,SHENG GuoHua1,3 & WANG HuiJie1 1 State Key Laboratory of Coal Resources and Safe Mining,Beijing Key Laboratory of Fracture and Damage Mechanics of Rocks and Concrete,China University of Mining and Technology,Beijing 100083,China 2 Department of Mechanical and Manufacturing Engineering,University of Calgary,2500 University Drive,AB T2N 1N4,Canada 3 School of Resources and Civil Engineering,Northeastern University,Shenyang 110004,China | 2010 | Science China(Technological Sciences)2010，53，9： | 8 |
| 7 | A numerical study on fire endurance of wood beams exposed to three-side fire显示文摘To investigate the fire endurance of wood beams exposed to three-side fire, we conducted bearing capacity tests of two wood beams and experiments of five wood beams exposed to three-side fire. The finite element software ANSYS was also used to predict the fire endurance of those beams with the indirect order coupling method. It was found that the fire endurance decreases as the load level increases, and the reduction ratio tends to decrease. In the case of a certain load level, the fire endurance is improved if the section size is increased or covered by the fire protection coating. The central deformation increases as the fire duration increases, and the ratio of increase tends to rise. On another note, an increase in the density of wood leads to a rise in the fire endurance of a given beam. From the finite element method (FEM) calculation results, the fire endurance decreases as the load level increases, and the reduction ratio tends to decrease. When the load level is greater than 0.5, the fire endurance is significantly reduced, and it does not change significantly when the load level changes. Lastly, for a load level magnitude below 0.5, the fire endurance and load level are proportional to one another. | Jin ZHANG 1, Qing-feng XU2, Yi-xiang XU3, Bin WANG1, Jing-xiang SHANG1 (1Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, Southeast University, Nanjing 210096, China) (2Shanghai Key Laboratory of New Technology Research on Engineering Structure, Shanghai Research Institute of Building Sciences, Shanghai 200032, China) (3Department of Civil Engineering, Strathclyde University, Glasgow G12 8QQ, UK) | 2012 | Journal of Zhejiang University-Science A(Applied Physics & Engineering)2012，13，7： | 5 |
| 8 | 2nd edition, Surry University Press 显示文摘 | FIP Manual of Lightweight Concrete | 1983 | England1983，3132，： | 1 |
| 9 | Guidelines for design of joints between steel beams and reinforced concrete columns 显示文摘 | The ASCE Task Committee on Design Criteria for Composite Structures in Steel and Concrete | 1994 | Journal of Structural Engineering1994，120，8： | 1 |
| 10 | Phase I report on folded plate construction显示文摘 | Task Group of the Subcommittee on Masonry and Reinforced Concrete of the Structural Division | 1963 | Journal of Structural Division1963，89，： | 1 |
| 11 | Laboratory Tests to Correlate Galvanic Current with Actual Damage显示文摘 | Yoo J Park Z Kim J Chung L Development of a Galvanic Sensor System for Detecting the Corrosion Damage of the Steel Embedded in Concrete Structures: Part 1 | 2003 | Cement and Concrete Research2003，133，12： | 1 |
| 12 | Part 1 Tension显示文摘 | SHIRVANI M KLINGNER R E GRAVES H L Breakout Capacity o{ Anchors in Concrete | 2004 | ACI Structural Journal2004，101，6： | 1 |
| 13 | Construction considerations for composite steel - and - concrete floor systems 显示文摘 | Subcommittee on composite steel and concrete floor systems of the committee on composite construction of the technical administrative committee on metals | 2002 | ASCE2002，128，9： | 1 |
| 14 | Proposed specification and commentary for composite joists and composite trusses显示文摘 | The ASCE Task Committee on Design Criteria for Composite Structures in Steel and Concrete | 1996 | Journal of Structural Engineering1996，122，4： | 1 |
| 15 | Guide-lines for design of joints between steel beam and rein-forced concrete columns显示文摘 | The ASCE Task Committee on Design Criteria forComposite Structures in Steel and Concrete | 1994 | Journal of StructuralEngineering1994，120，8： | 1 |
| 16 | FRP - con- members: Axial compression experiments modelling 显示文摘 | Rousakis T C fined concrete and plasticity 2007 29 (7) : Karabinis A I Kiousis P D | 2007 | Engineering Structures2007，，： | 1 |
| 17 | A procedure to develop scalable models for the transient response of sleepers in conventional and high-speed railway lines and implementation to the vertical vibration mode显示文摘 | situ railway concrete sleeper to Journal of Sound and Vibration Leon E Rizos D C Caicedo J M | 2011 | Soil Dynamics and Earthquake Engineering2011，31，3： | 1 |
| 18 | Analysis of complex grounding systems consisting of foundation grotmding systems with external grids显示文摘 | Ground resistance of concrete IEEE Transactions on Power Kostic M B | 1998 | IEEE Transactions onPowerDelivery1998，13，3： | 1 |
| 19 | Design Guide for Partially Restrained Composite Connections显示文摘 | ASCE Task Committee on Design Criteria for Composite Structures in Steel and Concrete | 1998 | Journal of Structural Engineering1998，，8： | 1 |
| 20 | Performance of building 显示文摘 | Iverson J K prestressed Northridge (2): 38-55 Hawkins concrete eardlquake N M | 1994 | PCI preeast during Journal1994，39，： | 1 |
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