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Analytical theory of flexural behavior of concrete beam reinforced with textile-combined steel

Science china(Technological Sciences) 2010年第6期53卷 1700-1710页

作者： xu shilang & {2. shiping department of civil Engineering,dalian university of technology,dalian 11602.,china 1. department of civil Engineering Dalian University of Technology Dalian 116024 China

Textile-reinforced concrete (TRC) is a new high performance cementitious composite material,which not only has superior corrosion resistance but also can effectively limit the development of concrete cracks and make the crack width and spacing of concrete become ***,due to the brittle feature of fiber materials,the TRC structural member has no distinct failure symptom when it arrives at its ultimate *** the same time,ordinary reinforced concrete (RC) elements have large dead weight and can not efficiently restrict the expansion of the main crack of structures because of the restriction of their special cover *** order to overcome the disadvantages of both the TRC and the RC,a new architecture reinforced with textile-combined steel is proposed in this study,making full use of the advantages of the above two *** cover concrete at the tension zone of an RC element is partially replaced with TRC and thus the steel reinforcements replaced with textiles are *** with the old one,the new structure has less dead weight and has the merits of service safety and good *** flexural development process of the proper beam with this new structure is investigated in this paper and based on the plane section assumption,analytical equations are derived by using nonlinear analysis theory,including the load-carrying capacity at different stages and moment-curvature relationship and mid-span deflection during the entire loading *** between the calculated and the experimental results reveals satisfactory agreement and thus verifies the feasibility of the equations.

关键词： textile-reinforced concrete limiting the crack beam reinforced with textile-combined steel flexural behavior analytical theory

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Analysis on cohesive crack opening displacement considering the strain softening effect

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Science china(Physics,Mechanics & Astronomy) 2006年第1期49卷 88-101页

作者： WANG Limin1, xu shilang2.& ZHAO Xiqiang3 1. Mechanics {2., Shandong university of technology, Zibo 2.5049, china 2. civil Engineering {2., dalian university of technology, dalian 11602., china 3. Mathematics {2., Ocean university of china, Qingdao 2.6071, china Mechanics department Shandong University of Technology Zibo 255049 China civil Engineering department Dalian University of Technology Dalian 116024 China Mathematics department Ocean University of China Qingdao 266071 China

In order to investigate the crack propagation in quasi-brittle materials like rock, ceramic and concrete, Hillerborg and his co-researchers abstracted the fracture process zone in front of a stress free crack in terms of a “fictitious crack zone”. On the fictitious crack zone, cohesive stresses distribute following a given softening relationship of stress vs. crack opening. Based on the polynomial or power series expression of cohesive crack opening displacement, the relationship of the cohesive stress vs. the crack opening displacement is established using elastic theory and integral equation, and some unknown physics variables are obtained using variation approach. The calculation results gained in this paper are close to the experimentally test ones.

关键词： cohesive crack, softening, dissipation work, variation approach.

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Dynamic Properties of Concrete under Severe Environmental Condition

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Journal of Wuhan university of technology(Materials Science) 2010年第5期25卷 877-882页

作者：闫东明 department of Hydraulic and Environmental Engineering Zhengzhou University department of civil and Hydraulic Engineering Dalian University of Technology

Exposure to environmental conditions can significantly influence the mechanical behavior of concrete structures in civil engineering. In this study, the effect of environmental factors, such as moisture and temperature, on the strain-rate sensitivity of concrete mixtures was systematically investigated. The strain rate varied from 10^-5s^-1 to 10^-2.^-1. From the investigation it was concluded that moisture content had a significant influence on the strain-rate sensitivity of concrete. With regard to concrete with low moisture content, temperature had little influence on the rate-dependent behavior; while for fully saturated specimens, a significant influence was observed. These phenomena were attributed to the meso-scale bonding properties of the concrete matrix. Equations were derived to characterize the ultimate strength increment of concrete with strain rate under different environmental conditions. An explanation to the dynamic failure mechanisms of concrete based on the experimental findings was proposed.

关键词： concrete strain rate moisture content temperature failure mechanism

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Tensile and Flexural Properties of Ultra High Toughness Cemontious Composite

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Journal of Wuhan university of technology(Materials Science) 2009年第4期24卷 677-683页

作者：李贺东徐世烺 State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology

The tensile and flexural properties of polyvinyl alcohol （PVA） fiber reinforced ultra high toughness cementitious composite （UHTCC） were investigated. The composite, tested at the age of 14 d, 2. d and 56 d, shows extremely remarkable pseudo strain hardening behavior, saturated multiple cracking and ultra high ultimate strain capacity above 4% under uniaxial loading. Also, the corresponding crack widths are controlled under 50 um even at 56 days age. In the third point bending tests on thin plate specimens, the composite shows ultra high flexural ductility and multiple cracking on the tension surface. The high ultimate flexural strength/first tensile strength ratio of about 5 verifies the pseudo strain hardening behavior of UHTCC. SEM observation on fracture surfaces provides indirect evidence of optimal design for the composite.

关键词： pseudo strain hardening cementitious composite multiple cracking ductility SEM

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Impact of well placement and flow rate on production efficiency and stress field in the fractured geothermal reservoirs

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Deep Underground Science and Engineering 2024年第3期3卷 358-368页

作者： Xinghui Wu Meifeng Cai xu Wu Ketong Zhang Ziqing yin Yu Zhu School of City and Architecture Engineering Zaozhuang UniversityZaozhuangChina School of civil and Resource Engineering University of Science and Technology BeijingBeijingChina Beijing Municipal Engineering Research Institute BeijingChina department of civil and Environmental Engineering University of StrathclydeGlasgowUK

Geothermal energy has gained wide attention as a renewable alternative for mitigating greenhouse gas *** advancements in enhanced geothermal system technology have enabled the exploitation of previously inaccessible geothermal ***,the extraction of geothermal energy from deep reservoirs poses many challenges due to high‐temperature and high‐geostress *** factors can significantly impact the surrounding rock and its fracture formation.A comprehensive understanding of the thermal–hydraulic–mechanical(THM)coupling effect is crucial to the safe and efficient exploitation of geothermal *** study presented a THM coupling numerical model for the geothermal reservoir of the Yangbajing geothermal *** proposed model investigated the geothermal exploitation performance and the stress distribution within the reservoir under various combinations of geothermal wells and mass flow *** geothermal system performance was evaluated by the criteria of outlet temperature and geothermal *** results indicate that the longer distance between wells can increase the outlet temperature of production wells and improve extraction efficiency in the short *** contrast,the shorter distance between wells can reduce the heat exchange area and thus mitigate the impact on the reservoir stress.A larger mass flow rate is conducive to the production capacity enhancement of the geothermal system and,in turn causes a wider range of stress *** findings provide valuable insights into the optimization of geothermal energy extraction while considering reservoir safety and long‐term *** study deepens the understanding of the THM coupling effects in geothermal systems and provides an efficient and environmentally friendly strategy for a geothermal energy system.

关键词： geothermal exploitation performance geothermal reservoir mass flow rate stress field well placementa

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Research on nonlinear constitutive relationship of permanent deformation in asphalt pavements

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Science china(Physics,Mechanics & Astronomy) 2006年第6期49卷 671-682页

作者： PENG Miaojuan1 & xu Zhihong2.1. department of {2. Engineering,Shanghai university,Shanghai 2.0072.china 2. School of Transportation Engineering,Tongji university,Shanghai 2.0092.china 1. department of civil Engineering Shanghai University Shanghai 200072 China 2. School of Transportation Engineering Tongji University Shanghai 200092 China

To predict correctly the rut depths in asphalt pavements,a new nonlinear viscoelastic-elastoplastic constitutive model of permanent deformation in asphalt pave-ments is presented. The model combines a generalized Maxwell model with an elasto-plastic one. Then from the creep theory,the linear and nonlinear constitutive equations of the generalized Maxwell model are obtained. From the nonlinear finite element method for the rutting of the asphalt pavement,the rut depths of 4 asphalt-aggregate mixtures are obtained. And the results are compared with the ones from the finite element method by SHRP and the experiments by SWK/UN. The results in this paper are better than the ones by SHRP,and agree with the ones of the experiment by SWK/UN. This shows that the nonlinear viscoelastic-elastoplastic constitutive model,which is presented in this paper for the rutting of the asphalt pavement,is effective. The properties,such as nonlinear elastic-ity,plasticity,viscoelasticity and nonlinear viscoelasticity,which affect the rutting of an asphalt pavement,can be shown in the model. And the characteristics of the permanent deformation of the asphalt pavement can be presented entirely in the model.

关键词： asphalt pavement,permanent deformation,nonlinear viscoelastic-elastoplastic constitutive relationship,generalized Maxwell model,creep compliance.

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纤维编织网增强混凝土加固钢筋混凝土梁受弯性能研究

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土木工程学报 2011年第4期44卷 23-34页

作者：徐世烺尹世平蔡新华浙江大学浙江杭州310058 大连理工大学辽宁大连116024 中国矿业大学江苏徐州221116

从改善纤维编织网增强混凝土(TRC)加固层中纤维束和精细混凝土的界面粘结及新老混凝土的界面特性入手,研究TRC增强钢筋混凝土(RC)梁的弯曲性能。试验结果表明:纤维编织网的表面黏砂处理能更好地发挥其有效约束能力,从而充分发挥TRC增强... 详细信息

从改善纤维编织网增强混凝土(TRC)加固层中纤维束和精细混凝土的界面粘结及新老混凝土的界面特性入手,研究TRC增强钢筋混凝土(RC)梁的弯曲性能。试验结果表明:纤维编织网的表面黏砂处理能更好地发挥其有效约束能力,从而充分发挥TRC增强层的限裂和增强作用;新老混凝土的界面植入U型抗剪销钉可以提高增强后RC梁的整体受力性能,而涂抹界面剂对其几乎没有影响。此外,精细混凝土中掺加聚丙烯纤维有助于提高构件的起裂荷载;在RC梁配筋率一定的情况下,提高TRC层中的配网率可以有效地延缓结构主裂缝的发展,减小裂缝的宽度和间距,明显地提高梁的屈服荷载和极限承载力。最后,基于RC结构的抗弯设计理论,模拟TRC增强RC梁的荷载与跨中位移曲线,计算值与试验结果吻合得较好,证明了计算方法的可行性。

关键词：钢筋混凝土梁纤维编织网增强混凝土加固受弯性能界面粘结

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Real‑time detection of aging status of methylammonium lead iodide perovskite thin flms by using terahertz time‑domain spectroscopy

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Frontiers of Optoelectronics 2024年第3期17卷 39-50页

作者： Jinzhuo xu yinghui Wu Shuting Fan xudong Liu Zhen yin Youpeng Yang Renheng Wang Zhengfang Qian Yiwen Sun department of Biomedical Engineering School of MedicineShenzhen UniversityShenzhen 518060China Guangdong Provincial Key Laboratory of Durability for Ocean civil Engineering College of Civil and Transportation EngineeringShenzhen UniversityShenzhen 518060China Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Physics and Optoelectronic EngineeringShenzhen UniversityShenzhen 518060China

The inadequate stability of organic–inorganic hybrid perovskites remains a signifcant barrier to their widespread commercial application in optoelectronic *** phenomena profoundly afect the optoelectronic performance of perovskite-based *** addition to enhancing perovskite stability,the real-time detection of aging status,aimed at monitoring the aging progression,holds paramount importance for both fundamental research and the commercialization of organic–inorganic hybrid *** this study,the aging status of perovskite was real-time investigated by using terahertz time-domain *** analysis consistently revealed a gradual decline in the intensity of the absorption peak at 0.968 THz with increasing perovskite ***,a systematic discussion was conducted on the variations in intensity and position of the terahertz absorption peaks as the perovskite *** fndings facilitate the real-time assessment of perovskite aging,providing a promising method to expedite the commercialization of perovskite-based optoelectronic devices.

关键词： Perovskite Terahertz spectroscopy Ageing Real-time detection

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A two-dimensional study on natural convection and heat transfer in the enclosure with heat transfer and radiation coupled in natural convection

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Science china(Technological Sciences) 2010年第4期53卷 991-999页

作者： ZHAN NaiYan1,2.YANG Mo1 & xu PeiWei2.1 College of Power Engineering,university of Shanghai for Science and {2.,Shanghiai 2.0093,china 2.department of Environmental Engineering,Jilin Architectural and civil Engineering Institute,Changchun 13002.,china 1. College of Power Engineering University of Shanghai for Science and Technology Shanghiai 200093 China2. Department of Environmental Engineering Jilin Architectural and Civil Engineering Institute Changchun 130021 China

Numerical investigation using SIMPLE algorithm with QUICK scheme for natural convection and heat transfer in the enclosure bounded by a solid wall and with heat transfer and radiation coupled in natural convection has been *** various parameters are:Rayleigh number(from 103 to 105),dimensionless conductivity of bounding wall(from 0 to 100),dimensionless wall thickness(from 0 to 0.6) and radiation emissivity of all surfaces(from 0 to 1).The results suggest that flow and heat transfer are influenced by *** is a dominant action on flow and heat *** increase of the thermal conductivity of wall,flow and heat transfer turn *** temperature distribution changes *** the thermal conductivity of wall is over a certain critical number,the increasing trend of flow and heat transfer may *** increase of enclosure wall thickness,flow and heat transfer turn *** the enclosure wall thickness is over a certain critical number,the flow and heat transfer will turn slow.

关键词： conduction natural convection radiation couple numerical simulation

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Experimental study on performance of spring damping support structure system for large deformation tunnel in soft rock

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Underground Space 2024年第2期15卷 221-243页

作者： Jinfeng xu Xiongyao Xie Zhou Shi Wuqiang Cai Dinglun xu Chen xu department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai 200092China Key Laboratory of Geotechnical and Underground Engineering Ministry of EducationTongji UniversityShanghai 200092China Zhaotong City Zhaolu Expressway Investment and Development Co. ZhaotongYunnan Province 657000China Institute of Rock Mechanics Ningbo UniversityNingboZhejiang 315211China

According to the convergence confinement theory,it is an effective measure to control the large deformation of high ground stress in fractured soft rock tunnels by using yielding *** yielding support can be classified as either radial or circumferential yielding *** yielding support is achieved by transforming radial displacement into circumferential tangential closure without compromising the support capacity of the primary lining support *** on this,and inspired by the design principle of dampers,a yielding support structure system with spring damping elements as its core was developed,based on the connection characteristics of steel arches in highway tunnel,which can provide increasing support resistance in the yielding deformation *** the mechanical properties of spring damping elements were obtained through indoor axial pressure and flexural *** addition,according to these results with numerical calculations,the yielding support structure system with embedded spring damping elements can reduce the internal force of the support structure by approximately 10%and increase the area of the plastic zone of the surrounding rock by 11.2.%,which can fully utilize the self-bearing capacity of surrounding rock and verify the effectiveness of circumferential yielding ***,the spring damping support structure system was designed with reference to the construction process of the tunnel excavated by drilling and blasting method,and the transformation of the spring damping element to spring damping support structure was *** on field test results,surrounding ground pressure for the yielding support optimization scheme was reduced by 40%and more evenly distributed,resulting in the successful application and a reduction in the construction cost of large deformation tunnels in soft rock.

关键词： Soft rock Highway tunnel Convergence confinement method Circumferential yielding support with spring damping element Numerical calculations Field test

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