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1.
Dynamic tests of three bonded and two unbonded full-prestressed concrete beams were carried out.The purpose was to seek the relation between prestressing force and natural frequency.Test results indicate that the frequency of prestressed concrete(PSC)beam increases with the increase in prestressing force approximately.The results are different from the dynamic characteristics of isotropic material beam subjected to compressive axial force which were put forward by Clough et al.The reason is that the beams were considered as isotropic,homogeneous,linear elastic material in the traditional analysis method.However,more accurate results are required in the analysis of frequency of PSC beam.The constitutive mode of PSC member is analyzed based on microstructure of concrete in this paper.The orthotropic linear elastic mode is used to analyze the relation between dynamic frequency and prestressing force of concrete beam,at the same time the equivalent stiffness of prestressed tendon relating to the prestressing force is added to the bending deformation stiffness of the beam.The analytical value agrees well with the test result,indicating that the current analysis method in this paper is feasible to full-prestressed concrete beam. 相似文献
2.
Long tunnel excavation with tunnel boring ily affected by uncertainties and needs to be adjusted machine （TBM） is a complex and stochastic process. It is eas- according to specific geological conditions in different tunnel sections, which makes the construction scheduling and management difficult. Based on the rock mass classification, this paper estimates the penetration rate. Using the rate, a cyclic network simulation （CYCLONE） model of TBM boring system is established, and the advance rates under different geological conditions are determined. Then, the impact of different cutter head thrust, which is chosen in reasonable range according to previous experiences, on pro- ject schedule is analyzed. Moreover, the simulation model of mucking system is built to determine the number of muck trains and rail intersections reasonably, regarding the efficiency of muck loading and material transporting. Based on the interaction and interrelation between TBM boring system and mucking system, the combined CY- CLONE model for the entire tunneling process is established. Then reasonable construction schedule, the utilization rate of working resources, and the probability of project completion are obtained through the model programming. At last, a project application shows the feasibility of the presented method. 相似文献
3.
In the past ten years, many exemplar projects are completed in China to encourage the sharing of knowledge and experience of sustainability. Many of these projects are landmark buildings, and because they can attract more public attentions, they raise more awareness of sustainable development. However, school projects are rarely mentioned in the news and annual inspirational project lists. The fundamental point of this paper is to challenge the common concept in China that school buildings are only used exclusively by children in formal education. According to the paper’s review of the school schemes in England and Wales, not only the inspirational sustainable schools created the opportunities and responsibilities to accelerate positive changes, but also they developed a vision of an asset that supports lifelong learning and sustainable lifestyles for the whole community. In this paper, the definition of a ‘sustainable school’ is summarised by comparing the statements and concepts in England and Wales. Moreover, a wide range of benefits gained by project stakeholders and communities are also demonstrated through case studies. In the end, lessons and innovations which can be learnt by Chinese school projects are concluded. The illustrations provided by this paper do not aim to solve all issues of promoting a sustainable school in China, but to open people’s minds to the impacts of their actions, and to build the knowledge and cooperative framework to promote public sustainable projects. 相似文献
4.
IT Project Evaluation and Investment Decision 总被引：2，自引：0，他引：2
There are many kinds of real options, which are valuable, in each phase of the lifetime of an information technology(IT) project. However, in the current IT investment decision theory, real options that embedded in IT projects are not considered. In this paper, the process of IT project decision and implementation is fully analyzed, the real options that may be embedded in an IT project are identified, and a real option analysis (ROA) method is proposed for evaluation of an IT project under uncertain business environment. ROA employs BlackScholes expansion model and cancels the assumption that the cost of project is certain. The numerical example manifests that the ROA can better evaluate IT project and select the IT investment alternative. Finally, a road map is provided to help selecting the suitable evaluation method to make IT investment decision. 相似文献
5.
郑永保 《重庆大学学报(英文版)》2003,2(2)
1. Introduction In order to meet the demands of developing west zone of China and utilization of urban underground space, tunnel construction is increasingly paid more attention to in China. As is known, concrete is the main building material used in civil engineering, which is always affected and eroded by various ions in underground water, so the durability of concrete structure which is the main part of tunnels and underground projects, has been a hot subject for investigation in civil engi… 相似文献
6.
Test and Analysis of an Existing Tunnel Vibration Induced by Blasting Construction of Diaphragm Wall
YU Guangxi YU Haitao LIU Xian YUAN Yong WANG Qingguo CHENG Guorong WU Xiaofeng 《天津大学学报(英文版)》2008,(Z1)
According to the blasting construction of the diaphragm wall of Puxi approaching section of East Fuxing Road river-crossing tunnel, the monitoring project of the vibration of the existing tun-nel induced by the blasting construction is put forward, which includes the sensors’ location, moni-tor method and the vibration monitoring system. Based on the monitoring data of the explosion vibration, the vibration wave forms, velocities, acceleration responses, main frequencies and fields of measure points are analyzed under the conditions of three locations and different charge quanti-ties. According to the safety-judging standard of explosion vibration, the conclusion that the exist- ing tunnel is safe under the explosion vibration is then drawn. Furthermore, the spectrum character-istics of three explosion vibrations and the spectrum changing properties of explosion vi-bration wave transmitting in different directions are concluded, which can provide reference to similar projects. 相似文献
7.
Yadolla Saeednia Mariani MD NOR 《美中教育评论》2010,7(5):94-100
Almost all schemes that have been issued by scholars or researchers to present Maslow＇s hierarchy of basic needs include a pyramid （triangle） in which the physiological needs are in the base and the self-actualization needs are in the top of the triangle. Although this scheming is inspiring to some results, basic needs have more characteristics that are significant however, this scheming is not able to inspire. Based on elaborating Maslow＇s theory and research＇s findings, this study aims to disclose weaknesses and strengths of traditional scheme （triangle）, and develop two innovated schemes of basic needs, which are more close to Maslow＇s ideas and more inspiring to realize the actuality of this hierarchy. 相似文献
8.
Spallation mechanism of RC slabs under contact detonation 总被引：2，自引：0，他引：2
The spallation of the concrete slabs or walls resulting from contact detonation constitutes risk to the personnel and equipment inside the structures because of the high speed concrete fragments even though the overall structures or structural members are not destroyed completely.Correctly predicting the damage caused by any potential contact detonation can lead to better for-tification design to withstand the blast loadings.It is therefore of great significance to study the mechanism involved in the spallation of concrete slabs and walls.Existing studies on this topic of-ten employ simplified material models and 1D wave analysis,which cannot reproduce the realistic response in the spallation process.Numerical simulations are therefore carried out under different contact blast loadings in the free air using LS-DYNA.Sophisticated concrete and reinforcing bar material models are adopted,taking into account the strain rate effect on both tension and com-pression.The erosion technique is used to model the fracture and failure of materials under tensile stress.Full processes of the deformation and dynamic damage of reinforced concrete (RC) slabs and plain concrete slabs are thus observed realistically.It is noted that with the increase of quantity of explosive,the dimensions of damage crater increase and the slabs experience four different damage patterns,namely explosive crater,spalling,perforation,and punching.Comparison be-tween the simulation results of plain concrete slabs and those of RC slabs show that reinforcing bars can enhance the integrity and shearing resistance of the slabs to a certain extent,and mean-while attenuate the ejection velocity and decrease the size of the concrete fragments.Therefore,optimizing reinforcement arrangement can improve the anti-spallation capability of the slabs and walls to a certain extent. 相似文献
9.
The current study is concerned with the integration of English reading and writing in a program which is delivered jointly by Henan University(HU) in Kaifeng and Victoria University(VU) in Melbourne.Currently,English writing and reading have irrelevant teaching contents.In order to make better use the Chinese and Australian teachers’ English expertise to enhance students’ English proficiency in the joint program,VU and HU initiated this case study of coordination and cooperation at a curriculum and delivery planning level for reading and writing.By analyzing research data,this paper aims to measure the effectiveness of integration of writing and reading,to identify students’ acceptance of the collaboration of writing and reading and also to explore alternative ways of designing the teaching materials in an Australia-China English course.The main findings of the research project relate to student confidence,knowledge,motivation which are greatly improved when reading and writing materials are closely-related;trial groups’ writing proficiency showed twice greater improvement than that of control group;integration of reading and writing better uses Australian and Chinese teachers’ English expertise;over 90% of the students comment that the specially-designed materials are useful and would like to continue learning in this way if possible. 相似文献
10.
Rozalina Popova-Koskarova 《美中教育评论》2010,7(8):73-77
The most significant aspects within this taking place in the educational system regarding to paper are overcoming the stereotypes and prejudices that are Roma children. In addition to this, there are couples of explorations which explain the way of how the Roma children are integrated and socialized within the school borders and more concrete within a class. In that context, it gives the marks, at the same time, the visions of the Roma students in creating a comfortable atmosphere where they would find themselves to be motivated and show their best optimal school results, as well as support and encouragement for their increased activity, motivation and initiative within the school. Also, the author presented some project experiences from Sweden and Macedonia. As a pattern of an informal education from Faculty of Pedagogy in Skopje, which is very interesting, offers possibilities for development of capabilities and awareness of unity, mutual respect, tolerance ethnic harmony and building up of the consciousness of the existence of the other, especially for Roma students. The human ideas like being the first to love and taking initiative without wanting to be loved are accessible to everyone and are especially useful for youngsters. 相似文献
11.
Floods result in many problems, which may include damage to cross-river tunnels. The cross-river tunnel, as a new style of transportation, deserves a large amount of attention. In this paper, a large-scale cross-river tunnel model is proposed based on discrete element method (DEM). Micro parameters used in the model are calibrated by proposing a triaxial numerical model. Different in situ strata, high water pressures of normal flood-water levels and random vibration levels induced by running trains are taken into account to evaluate the dynamic characteristics of a high-stress tunnel in deformation and stress analysis. The results show that the upper half of the tunnel, including the concrete lining and the surroundings, is at higher risk than the lower half. Vibration waves transferring into the surroundings undergo an amplification process. The particles of the surroundings at the vault of the tunnel separate and move downward and then reassemble during the dynamic vibrations. The vibration levels, represented by particle accelerations, are lower under flood conditions than those under normal conditions. As train speed increases, the acceleration of the track and particles in the foundation increases, accompanied by a decrease in deformation. 相似文献
12.
娄金亮 《石家庄铁路职业技术学院学报》2021,(1):73-77
结合张吉怀高速铁路项目工程,阐述了三维全断面自动扫描技术在隧道施工中的应用。该技术能够有效地控制隧道超、欠挖,隧道初支、二衬混凝土方量,确保隧道开挖、初支及二衬断面均满足设计要求。该技术为今后类似工程施工提供一些可借鉴的经验。 相似文献
13.
利用派生成组性质相同的小断裂判断主断层的性质 总被引：3，自引：0，他引：3
丁宽 《雁北师范学院学报》2006,22(5):55-57
同煤集团公司四台矿406采区建井期间首采工作面布置过程中,运输顺槽掘进至520m时,出现了一条落差超过煤层厚度的断层,落差和性质不明,只知道产状.在可利用的地质构造资料很少的情况下,仅利用本巷已接露的一组性质都为正断层、倾向近270°、倾角较大、落差很小的小断层组的性质、产状等要素来推断与之相距约15m左右的主断层的性质.然后提出用钻机向上打孔来探煤的方案,一次性地找到了煤层断失翼的位置,抢回了工期,节省了钻探费用.成功地解决了巷道在掘进过程中遇断的问题. 相似文献
14.
白明举 《贵阳学院学报(自然科学版)》2007,2(2):13-15
鉴于贵州喀期特地质特点,尤其是溶洞位于隧道顶面且土石不断掉落的情况,采用泵送混凝土回填拱顶溶洞的方案,既不会造成人员伤害,又不影响后续工序的正常进度,无疑为山区公路隧道施工积累了又一成功的经验. 相似文献
15.
深部地层的煤岩都处在地层压力作用下,其本身存在一定的内部应力。如果对这样的煤岩进行开挖,煤岩的破坏特征往往是卸荷破坏,而不是加载破坏。为了研究煤岩在卸荷破坏条件下的力学特征,提取煤岩试件,在三轴试验机上完成卸荷破坏试验,得到大量试验数据,并进行分析,推导其本构关系和破坏准则解析表达式。 相似文献
16.
通过对晋城矿区由于采煤沉陷导致建筑受损的具体情况的介绍,对沉陷区的建筑破坏特征进行了总结分析。在此基础上,针对不同类型、不同破坏情况的建筑的具体分析及研究,对采煤沉陷区受损建筑的加固处理方案进行了探讨。 相似文献
17.
叶海松 《淮南职业技术学院学报》2005,5(3):19-20
分析了一起特厚煤层沿巷道底板掘进巷道的钻场因进行顺层钻孔抽采导致煤层自燃事故的原因,提出了防治该类自燃发火隐患的技术措施：抽采钻孔抽入口必须位于巷道周围的破碎区以外;定期监测顺层抽采钻孔内气体变化情况;严格控制在巷道的冒落区、阶段煤柱内布置钻孔抽采瓦斯. 相似文献
18.
对钢筋混凝土裂缝产生的原因进行分析，提出钢筋混凝土裂缝的处理与防治措施。控制混凝土的收缩和内外温差变化以及提高其抗剪强度是防止裂缝产生的关键技术。 相似文献
19.
徐端宁 《淮南职业技术学院学报》2006,6(1):13-16
通过对淮南矿区瓦斯治理的分析,阐述了汇集瓦斯抽放巷在矿井瓦斯综合治理和“煤与气共采”两方面中的重要意义,讨论了汇集瓦斯抽放巷的优势和具体应用、在抽放巷内进行钻场和钻孔综合施工的技术要求以及在选用汇集瓦斯抽放巷时需要注意的问题。 相似文献
20.
朱占虎 《河北能源职业技术学院学报》2004,4(3):64-64,71
通过架棚巷道支护结构分析，架棚巷道破坏原因多是由于巷道的侧压力和底鼓引起，造成棚子相对下沉，使巷道变形、断面变小，采取在巷道两墙打锚杆和棚脚穿钢筋混凝土鞋后巷道围岩对侧压力减小了，支架支承能力增强，提高了巷道的稳定性。 相似文献