预应力FRP布加固混凝土桥墩的力学性能研究

通过对FRP(Fiber Reinforced Polymer)布加固混凝土桥墩时预应力施加方法的研究和分析,给出了预应力FRP布加固混凝土桥墩的施工方法;以某铁路桥梁中的大尺寸混凝土桥墩为例,比较分析了预应力FRP布加固混凝土桥墩的优点和优势,参照中美两国规范给出了预应力FRP布加固混凝土墩柱的承载力和延性分析方法。结果表明,与未施加预应力的FRP布加固混凝土墩柱相比,采用预应力FRP布加固混凝土墩柱可以有效提高其承载能力和延性;与AFRP布相比,CFRP布更适用于预应力FRP加固工程。     

体外预应力辅助张贴FRP布加固钢筋混凝土梁

针对外贴FRP布加固混凝土存在的不足,提出了体外预应力体系辅助外贴FRP布加固钢筋混凝土T形梁的方案,并从施工工艺、内力和整体性等方面作了分析,指出该方案对克服单独外贴预应力ERP布或者体外预应力加固混凝土开裂梁存在的不足具有明显的效果.     

纤维复合材料布加固混凝土梁受剪性能的试验研究

本文介绍了8根GFRP布、1根CFRP布加固混凝土梁以及1根未加固对比梁的受剪试验,研究了FRP布受剪加固形式、加固量、剪跨比、FRP材料类型等对受剪性能的影响,着重研究了U型FRP布受剪加固的剥离破坏性能和承载力。根据FRP布应变的试验实测结果,分析了剥离破坏时FRP布的有效发挥程度及其对受剪承载力的贡献,提出了U形FRP布受剪加固混凝土梁剥离承载力的计算公式。     

预应力FRP板加固混凝土结构研究进展

介绍预应力FRP板加固混凝土结构的国内外研究现状 ,FRP板的力学特性及预应力的施加方法 ,预应力FRP板加固混凝土、板梁的试验研究成果 ,FRP板加固混凝土梁的承载力计算方法等。     

预应力芳纶纤维布加固混凝土梁抗弯性能试验及理论分析

预应力技术是充分发挥FRP复合材料高强性能的一条有效途径。通过对预应力芳纶纤维布加固混凝土梁抗弯的试验,对预应力水平对梁抗弯承载力、刚度、延性的影响进行分析。结果表明:预应力水平为55%~65%时,预应力芳纶纤维布加固梁的开裂、屈服、极限荷载比非预应力芳纶纤维布加固梁分别提高约147%~165%、28%~50%、13%~31%,表明预应力芳纶纤维布能显著地提高混凝土梁的抗弯性能。承载力极限状态时,预应力梁为纤维布的断裂破坏,非预应力梁发生布与混凝土间局部脱粘破坏。在试验研究的基础上,采用弹塑性截面分析法计算梁的承载力,理论计算值与试验值吻合良好。     

预应力芳纶纤维布加固混凝土梁的受剪承载力试验研究

通过7根芳纶纤维布加固钢筋混凝土梁的抗剪性能试验,研究了芳纶纤维布的预应力水平及加固形式对混凝土梁抗剪承载力的影响。试验结果表明,带永久锚具的预应力芳纶纤维布加固混凝土梁与非预应力芳纶纤维布加固混凝土梁相比,其开裂荷载显著提高,屈服荷载与极限荷载明显提高;预应力芳纶纤维布加固混凝土梁的抗剪承载力随着纤维布预应力水平的提高而增大。     

预应力FRP布加固混凝土梁的承载力计算

预应力FRP布加固混凝土梁可充分发挥材料高强度,又能有效抑制构件裂缝和变形的发展,使其在混凝土结构工程加固领域中得到了广泛的研究和应用。虽然国内外对预应力FRP加固混凝土梁的抗弯、抗剪承载力、预应力损失、弯曲疲劳性能、粘结滑移性能、施工工艺、机具、锚固方式等方面进行了研究,但由于组合结构材料本身受力性能的复杂性,仍然有很多问题没有很好地解决。例如：方便快捷的预应力锚具的开发应用,预应力损失的进一步试验研究,温度应力对预应力损失的影响,截面形状对受弯承载力的影响,预应力纤维布加固混凝土梁的刚度计算等问题。     

预应力碳纤维布加固钢筋混凝土T形梁试验研究

近年来,预应力碳纤维布加固混凝土梁技术以其碳纤维布强度利用程度高、能改变被加固梁正常使用阶段性能的显著优点成为粘贴类加固研究的一个热点。通过3根预应力碳纤维布加固钢筋混凝土T形梁的试验研究,对比分析了预应力碳纤维布、非预应力碳纤维布加固梁和未加固混凝土梁的性能区别,试验结果进一步验证了预应力碳纤维布加固技术的显著优点。试验研究可为后续同类研究提供参考。     

预应力张拉过程中出现问题的探讨

本文在参考了一定的试验研究的基础上,对预应力加固张拉过程中若干问题及FRP布加固混凝土梁的破坏类型进行了讨论分析,并提出了应对措施。     

预应力碳纤维布加固混凝土梁弯曲疲劳性能试验研究

目前,对预应力碳纤维布加固梁的疲劳性能研究甚少。通过对7根预应力碳纤维布加固混凝土T形梁弯曲疲劳性能的试验研究,考察了预应力碳纤维布加固量、钢筋配筋率、等幅变幅疲劳以及加固前疲劳损伤对加固梁疲劳性能的影响。试验结果表明,与非预应力碳纤维布加固梁相比,预应力碳纤维布加固后混凝土梁中受拉钢筋应力幅显著降低,混凝土梁疲劳寿命明显延长。     

Water movement in porous building materials—XII. Absorption from a drilled hole with a hemispherical end

The water absorption characteristics of cylindrical and hemispherical cavities are compared. The absorption from a drilled hole with a hemispherical end is analysed in terms of cylindrical and hemispherical components. Water absorption data from a cylindrical cavity with a hemispherical end are analysed to provide values of sorptivity for various brick and mortar samples. The values of sorptivity are compared with those obtained from one-dimensional absorption data as well as from absorption data from cylindrical and hemispherical cavities. It is shown that the same two term equation may be used to analyse the water absorption data from all three geometrics.     

船闸边坡断续节理岩体强度特性分析

根据断续节理岩体模型试验得到的岩桥贯通机理，建立起表征岩桥初裂强度和不同破坏模式下的贯通强度计算公式。计算结果表明，所建立的强度计算模型和模型试验结果基本吻合。因此，本研究成果对正确认识断续节理岩体的强度特性，具有较高的理论和工程应用价值。     

Gas temperature measurements using fibre Bragg grating during fire experiments in a tunnel

Gas temperature measurements with thermocouples are affected by radiation. This effect means that the temperature measured by a thermocouple can be far from the actual gas temperature. To study this effect and to compare the thermocouple readings with the readings of a fibre Bragg grating (FBG) sensor, fire experiments were performed in a model-scale tunnel. In this paper the results from two such fire experiments are presented. The temperatures measured using thermocouples with different diameters and the FBG sensor are compared and discussed. The “true” gas temperature, corrected for radiation effects from the thermocouples, was calculated from the results from the thermocouples with different diameters. The results show that the temperature measured by the FBG sensor is closer to the “true” gas temperature than is the case for any of the thermocouples used in these tests.     

花岗岩残积土基床系数的求取——以深圳华润、地铁2号线等工程为例

基床系数是隧道、基坑设计的重要参数,一般要求采用K_(30)载荷板试验求取,但受场地、安全等因素制约,K_(30)载荷板试验往往很难进行,本文通过取土室内试验、标准贯入试验、重型动力触探试验、旁压试验、螺旋板载荷试验等较易实现的手段求取基床系数,并与现场K_(30)试验值进行对比,验证了各种原位测试求取基床系数的有效性,对花岗岩残积土基床系数的求取有一定借鉴作用。     

Emissions from Fires Part I: Fire Retarded and Non-Fire Retarded TV-Sets

The results of detailed measurements of the emissions from simulated fires with TV-sets are presented in this article. Results from both small- and full-scale fire experiments with flame retarded and non-flame retarded TV-sets are discussed. The measurements cover a broad range of chemical species including specific fire retardant agents and both chlorinated- and brominated dibenzodioxins and furans. The results from similar measurements, but in this case from simulated room fires, can be found in part II in this series of articles.The methodology applied for the measurement of this large range of fire gases is presented in this article. Further, the sampling and analysis methods common for both the TV fires and the simulated room fires are described in detail in conjunction with the experimental results from the TV fires. Additionally, recommendations are made concerning good practice when conducting fire gas determinations of similar complexity.     

A review of the role of bed deposits in the phosphate eutrophication of lakes and rivers

The distribution of phosphates in fresh waters is briefly discussed and the different phosphorus cycles are mentioned. The chemistry of phosphorus in lakes is reviewed with special reference to the extraction methods used for the fractionation of phosphorus in soils and sediments. The models of the sediment‐water exchange are also discussed together with their environmental implications. The relevant publications on the adsorption by and desorption from sediments, especially clays, are reviewed with special reference to the adsorption mechanism on clays and the oxides of Fe and Al. The important topic of the desorption of phosphate from the relevant minerals and soils is presented with special reference to the effects of the sediment and water parameters affecting the release of phosphate from sediments.     

普通全玻幕墙玻璃肋失稳临界荷载

建立了全玻幕墙玻璃肋失稳临界荷载的解析式.以三边简支板为分析模型,运用能量法,推导得到了玻璃肋受面内荷载作用时发生失稳的临界荷载解析式.将该解析式计算所得到的临界荷载与ANSYS分析的结果进行比较.结果表明,解析式计算的结果是可靠的,该解析式是准确的,给玻璃肋失稳临界荷载的求解提供了参考.     

软土循环扭剪应力应变响应的弹塑性分析

为了分析笔者提出的增量弹塑性模型对描述一般应力状态土单元循环应力应变响应的适用性,进行了软土不排水循环三轴压缩试验与无初始轴向偏应力的循环扭剪试验,得到了两种应力状态土单元的循环应力应变响应。进而依据循环三轴压缩试验结果确定模型参数,再利用模型预测软黏土循环扭剪试验土单元的应力应变响应,并与试验结果进行对比分析。结果表明,预测出的无轴向静偏应力作用的循环扭剪土单元环向剪应力应变滞回曲线与试验结果相比偏小,但是总变化趋势与试验结果较为一致;预测出的循环扭剪土单元环向累积剪应变随循环次数的变化与试验结果基本一致。研究工作表明,该增量弹塑性模型能够较好描述不同应力状态土单元的不排水循环应力应变响应,特别是循环累积应变响应。     

Outdoor Air Contaminants and Indoor Air Quality under Transient Conditions

The indoor concentrations of contaminants originating from outdoor sources have been measured and calculated under transient conditions. The results show that contaminants that are supplied to an office building via the ventilation system can reach considerably high concentration levels. The indoor/outdoor concentration ratio and time lag are dependent on the air change rate. In buildings with low air change rates the indoor concentration variations are smoothed out compared to buildings with high air change rates. The results from the theoretical model are compared to the results from both laboratory and field measurements and the model is verified for well mixed conditions in a 20 m³ test chamber. The model can be used to simulate different control strategies for reduction of indoor contaminant concentrations related to outdoor sources. One such control strategy is based on reduction of the outdoor air change rate during periods with peak outdoor contaminant concentrations.     

柱脚固接有吊车厂房门式刚架柱的计算长度

有吊车厂房中框架柱轴力和截面都阶型变化 ,对于柱脚固接的阶型柱 ,规范只给出了顶端铰支或固支时的计算长度系数 ,没能考虑梁对柱的约束作用。通过对柱脚固接阶型的弹性屈曲分析 ,得到了框架柱平面内、平面外计算长度系数的表达式和计算表格 ,结果与有限元分析符合较好。在此基础上 ,对计算长度系数公式进行了简化