首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 78 毫秒
1.
本文通过试验.研究了大悬挑圆板基础的破坏图形及破坏机理.并对此类板的极限承载 力的计算方法进行了探讨.发现板的实测极限荷载比按极限平衡法计算求得的极限荷载约低28% 左右,且随着板的r1/r3的增大,其差值越大,从而认为目前对烟囱、简体水塔的圆板基础的承 载力计算普遍采用的极限平衡法不适用于大悬挑圆板基础,偏于不安全.对于大悬挑圆板基础, 仍以采用弹性理论计算为宜.  相似文献   

2.
从极限分析理论出发,就翼缘削弱型节点(简称RBS节点)对结构破坏模式与极限承载力的影响进行研究.首先对美国FEMA提出的RBS节点设计方法进行分析,并讨论了该设计方法中的不足.针对上述不足,将极限荷载的唯一性定理推广到同时承受比例荷载与固定荷载的结构;对于满足强柱弱梁要求的框架结构,进一步论证了其横梁极限内力状态的唯一性.以此为基础,提出了针对美国FEMA RBS节点设计步骤的补充验算公式;针对组合破坏机构,提出了RBS节点设计新方法.其次,对RBS节点钢框架的极限承载力进行了理论推导,得到了极限承载力理论计算公式,同时明确了极限承载力的影响因素.最后,利用Abaqus有限元分析软件验证了上述理论研究结果的正确性.  相似文献   

3.
提出了一种利用荷载传递的双曲线模型计算单桩荷载-位移曲线的方法.该方法将桩划分为若干计算桩段,充分利用工程地质资料可以较好地计算出单桩荷载-位移曲线,并求得单桩极限承载力.计算结果与实测值比较吻合.  相似文献   

4.
负载钢筋混凝土梁钢筋锈蚀及使用性能试验研究   总被引:17,自引:1,他引:17  
通过对负载下锈蚀、不负载锈蚀梁和一组参考梁的对比试验,研究了荷载对钢筋混凝土结构中钢筋锈蚀及钢筋混凝土梁变形性能和剩余承载力的影响.整个锈蚀试验过程中施加的持续荷载为极限荷载的0%、25%、45%和65%.通过交替喷洒3.5%的盐水来模拟海洋潮汐环境.采用外加电流来加速钢筋锈蚀.整个试验过程中检测梁的挠度,达到预定的时间后进行剩余承载力试验.结果表明,荷载对钢筋锈蚀有明显影响,荷载作用使梁锈蚀加速,梁的挠度增大,剩余承载力减小.由于钢筋混凝土结构一般都是负载工作的,所以对钢筋混凝土结构使用寿命进行预测时,应考虑使用荷载和暴露环境对结构耐久性能的影响.  相似文献   

5.
为提高混凝土单个试件抗折强度的预测精度,分析了弯曲应力下变形曲线和弯曲比例极限的特性,阐述了基于弯曲比例极限预测单个试件抗折强度的原理和方法.弯曲应力-应变曲线具有在比例极限荷载处由线性向非线性转变的特征,在不破坏试件的前提下,对试件进行逐级加载至比弯曲比例极限荷载大1~2kN,根据应变增量的变化可确定该试件的弯曲比例极限荷载,且该试验不会对试件造成损伤.相同配合比混凝土的弯曲比例极限基本为常数且其变异性比抗折强度小,同配合比混凝土的弯曲比例极限平均值可作为每个试件弯曲比例极限的预估值,将弯曲比例极限荷载除以比例极限平均值即可预估试件的抗折强度.该方法能显著提高单个试件抗折强度的预测精度,可用于预测弯曲疲劳试件的抗折强度.  相似文献   

6.
建筑结构用钢丝束拉索的抗力分项系数研究   总被引:1,自引:0,他引:1  
为了使用概率极限状态法对拉索进行设计,收集了由高强度钢丝扭绞形成的钢丝束拉索的试验数据,采用概率方法研究了拉索的抗力分项系数取值,提出了建筑结构设计中考虑长期荷载效应和短期荷载效应时拉索的设计计算方法及建议.  相似文献   

7.
提出用上限法对c-φ材料进行三维极限分析的原理和方法.分析过程基于非线性规划和线性有限元法,通过求解一个非线性规划问题,使外荷载消耗的功率最小,求得结构的极限荷载.算例分析表明,该方法是正确可行的.它避开了传统的有限元法中c-φ材料复杂的本构关系,直接得到结构的极限荷载的上限.  相似文献   

8.
本文应用广义阶梯函数对承受边缘弯矩局部均布荷载和线性分布荷载的简支圆板进行塑性极限分析.文中考虑了荷载的三种可能分布形式,给出了圆板极限荷载的计算公式.  相似文献   

9.
密肋轻铜龙骨复合墙体是密肋结构体系中的一种新型墙体构件形式,具有现场施工连接方便,易于工厂成批化加工等优点.为了研究其墙体的承载性能,对1/2比例密肋轻钢龙骨复合墙体与普通密肋复合墙体进行了低周反复荷载试验,对比研究了密肋轻铜龙骨复合墙体的破坏形态、铜骨应变变化规律、抗剪承载力影响因素及其实用计算公式等试验结果表明,两者的破坏形态基本一致,轻钢龙骨复合墙体的承载力明显高于普通密肋复合墙体.最后结合试验数据给出了密肋轻铜龙骨复合墙体的开裂荷载与极限抗剪承栽力的建议计算公式.  相似文献   

10.
在试验的基础上,对均布荷载作用下钢筋混凝土圆、环形板式基础的极限承载力进行了研究.考虑环梁的约束作用,采用了不同于传统计算方法中的破坏机构,使板式基础的极限承载力得到较大的提高。通过试验分析,提出了三种破坏机构及相应的极限承载力计算公式,公式的计算值与实测值进行了比较,吻合良好.  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

15.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

16.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

17.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

18.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

19.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

20.
1 Rise of studies on climate change's effects on biodiversity
Until the 1980s, climate change and biodiversity were studied as two independent disciplines for more than a century. In 1992, the Ecological Society of America's annual report named climate change, biodiversity, and the sustainable ecological system as the three major global environmental issues of the twenty-first century [1].  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号