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1.
为研究升温和降温过程中混凝土梁不同位置处的升温、降温速率及温度场的分布规律,通过8根混凝土梁在高温炉中的加热和冷却试验,测定了4种温度工况(400、600、700、800℃)下混凝土梁内不同位置处温度随时间的变化规律。通过试验数据的分析,得到了加热和冷却过程中混凝土梁内不同位置处升温、降温速率的特点及温度场的变化规律,为混凝土高温或火灾试验中确定合理的加热时间提供了参考依据。  相似文献   

2.
由大跨度钢结构和钢筋混凝土框架组成的大剧院建筑,过火后不同结构部分损毁情况大不相同.介绍了某大剧院遭受火灾后,结构剩余强度的检测和鉴定.通过对火灾现场进行详尽的调查后,根据现场火灾损毁及构件表观情况温度调查,结合《火灾后建筑结构鉴定标准》[1](CECS 252-2009)进行了不同区域结构受热温度的判断及划分;根据《火灾后建筑结构鉴定标准》[1]和现场检测结果,对不同温度区域结构构件的混凝土、钢筋材料的强度进行折减,运用PKPM软件对火灾区域结构进行了承载力分析和安全性鉴定,并提出了该结构火灾后的处理建议.  相似文献   

3.
采用ANSYS软件模拟C60混凝土试件加热过程中的温度场,确定不同温度组试件的加热时间.利用高温SHPB试验装置进行不同加热长的高温后混凝土冲击压缩试验,分析了高温和加热时间对混凝土动态压缩力学性能的影响.结果表明:经历高温后且不同加热时间的混凝土材料,在自然冷却后表现出明显的温度软化效应和时间效应;在不同高温后,随着加热温度的升高混凝土动态抗压强度逐渐减小,峰值应变先增大而后略微降低且始终大于室温条件下的峰值应变;在相同温度且不同加热时间的条件下,混凝土随着加热时间的增加,其动态抗压强度不断降低,峰值应变总体上先增大后减小,弹性模量减小.  相似文献   

4.
混凝土高温后进行粘结劈拉强度试验研究   总被引:5,自引:1,他引:5  
为了研究混凝土结构建筑物在高温(火灾)损伤后进行混凝土粘结修补的粘结性能,对经历高温混凝土与新混凝土的粘结试件进行了劈拉强度试验。温度从常温到900℃分为9个温度段,采用空气中自然冷却和喷水冷却两种降温方式,考虑了新混凝土强度和界面剂的影响,系统地研究了各种参数对新老混凝土粘结性能的影响规律,指出高温后粘结机理主要是由老混凝土的损伤程度所决定的。  相似文献   

5.
为研究高强混凝土遭遇火灾后产生的损伤破坏情况,根据红外热像检测原理,对高温作用后的素混凝土和聚丙烯纤维混凝土进行红外检测,并进行了抗压强度试验。通过对试验结果的分析计算,建立了掺聚丙烯纤维前后的高强混凝土试块红外热像平均温升与受火温度和抗压强度损失率的关系。分析结果表明,随受火温度的升高,素混凝土和聚丙烯纤维混凝土的红外热像平均温升基本上处于上升趋势,而抗压强度降低,500℃时强度损失率达到50%,600℃以后,聚丙烯纤维混凝土的强度损失率更是达到75%左右,表明试块损伤趋于严重。通过建立平均温升与受火温度、抗压强度比之间的回归方程,可鉴定火灾后混凝土的火灾温度、结构损伤程度,有利于及时修复灾后建筑物。  相似文献   

6.
混凝土构件在火灾中的高温耐火性能对建筑结构的安全性具有重要意义.根据混凝土柱构件在火灾中承受恒压荷载和高温双重作用的特征,设计出一种混凝土柱高温性能测试方法:将混凝土柱置于恒压荷载下,对其进行加热并恒温,测试加热至不同温度的混凝土构件的性能变化.根据混凝土柱在加热过程中的初始爆裂温度、高温后的爆裂程度、裂缝形态和力学性能等指标,评价其高温耐火性能.通过对3组高强混凝土棱柱体进行测试,结果表明:该方法能反映出受压混凝土柱构件的耐火性能,并且具有对测试仪器要求不高、测试方法简便和结果可靠的特点.  相似文献   

7.
火灾对建筑物的破坏主要是高温作用,要确定遭受火灾后钢筋混凝土构件的受损伤程度必须确定构件的受火温度。该文介绍了火灾后混凝土结构的检测,采用了岩相分析等方法准确地判定受火温度,并通过多种手段结合对结构受火后混凝土和钢筋的强度进行推定,评定结构受损程度。  相似文献   

8.
张雷顺  赵建立  张剑 《河南科学》2004,22(4):515-518
采用非线性有限元方法对火灾时混凝土构件的温度场进行了仿真计算,计算结果与试验数据吻合较好,在此基础上计算了多种火灾情况下混凝土受压柱的温度分布情况,为灾后建筑物的检测评定与加固设计提供了一定的依据。  相似文献   

9.
火灾后混凝土构件耐久性损伤评估与鉴定   总被引:1,自引:0,他引:1  
根据正常环境作用对混凝土结构耐久性的计算方法,建立了火灾后混凝土构件的耐久性失效时间的计算和评定方法。并以工程背景为例,对火灾后建筑物构件的耐久性损伤评定进行了计算和分析。  相似文献   

10.
张博  何沛祥 《工程与建设》2010,24(3):298-300,303
对高温(火灾)下预应力混凝土简支板利用Ansys数值模拟板的温度场及应变,与已有试验对比得出高温下预应力构件温度场及力学性能通过Ansys软件有限元分析的可行性;对一预应力混凝土板进行数值模拟,得出板在单面受火过程中温度场变化的规律及其跨中应变随时间一温度的变化。  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.
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   

14.
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   

15.
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   

16.
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   

17.
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   

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   

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