常规检测快速推定水泥标准强度的研究

分别对水泥雷试夹试件强度、水泥3天强度和水泥28天标准强度中的二者建立关系曲线,通过数理统计建立快速测定水泥强度关系式,从而用雷试夹试件强度和水泥3天的标准强度来预测、推定水泥28天强度。试验检测证明,此方法预测、推定强度值准确,有应用价值。     

木材强度准则的研究进展

木材的强度准则是木结构理论分析和数值模拟的重要基础。根据国内外的研究进展,对木材单轴、双轴以及多轴应力状态下的强度准则进行系统地介绍,包括最大应力准则、最大应变准则、Hill屈服准则、Hill型强度理论、Tsai-Wu准则、van der Put强度理论和木材剪切强度理论。通过与文献中木材强度实测值的比较,验证木材斜纹强度公式的有效性。对比木材强度准则在多轴应力状态下的强度包络线,总结各强度准则间的差异和适用范围,并讨论张量系数对强度包络线的影响。通过综述木材强度准则在木结构数值模拟中的应用,简要分析各强度准则的优缺点。最后提出木材强度准则需要进一步研究的问题。     

常规检测快速推定水泥标准强度的研究

分别对水泥雷试夹试件强度、水泥3天强度和水泥28天标准强度中的二者建立关系曲线,通过数理统计建立快速测定水泥强度关系式,从而用雷试夹试件强度和水泥3天的标准强度来预测、推定水泥28天强度。试验检测证明,此方法预测、推定强度值准确,有应用价值。     

钻芯-回弹综合法检测混凝土强度的应用

结合回弹强度判定混凝土的匀质性的优势和芯样强度推定结构混凝土强度的特点,将这两种方法综合运用,对回弹强度进行了修正,得出能全面又相对比较真实的反映混凝土强度质量的综合检测法。工程实例表明：通过测区回弹强度与同部位芯样强度值的修正,证实了用钻芯-回弹综合法检测混凝土强度的必要性。     

再生骨料特性对再生混凝土强度和碳化性能的影响

为了评价再生骨料表面砂浆的强度及附着率对再生混凝土性能的影响,以再生骨料表面不同的砂浆强度及附着率为变量,配制了不同强度等级的再生骨料混凝土,通过对比性强度试验和碳化试验评价了再生混凝土内部存在的2个界面过渡区与混凝土性能的关系.结果表明:以高强度原生混凝土为再生骨料配制相对较低强度等级的再生骨料混凝土时,其强度与普通混凝土几乎相同,再生骨料表面砂浆的强度及附着率对再生骨料混凝土强度影响不大,但碳化深度有所增大;以相对较低强度原生混凝土为再生骨料配制同强度等级以上的再生骨料混凝土时,其强度与普通混凝土相差较大,再生骨料表面砂浆的强度及附着率对再生混凝土强度影响较大,碳化深度也相应增大.     

泵送混凝土实体强度检验的试验研究

结构中的混凝土实体强度与标准养护强度是有差别的,施工质量验收规范已提出了用同条件养护试件强度检验实体强度的要求.通过对唐山地区同条件养护混凝土试件强度的系统试验研究,探讨了其增长规律,并在此基础上建议了反映实体强度的同条件养护试件强度检验的等效养护龄期及强度折算系数.     

有限差分强度折减法求解边坡稳定性

在比较传统的极限平衡法和有限元强度折减法的同时,介绍了有限差分强度折减法的原理和具体步骤.基于有限差分FLAC程序,通过算例研究了有限元强度折减法与有限差分强度折减法的计算结果,验证了有限差分强度折减法的可靠性.分析了有限元强度折减法与有限差分强度折减法计算结果的差异性,并指出了有限差分强度折减法的优点为能够对具有复杂...     

不同养护条件对火灾后混凝土抗压性能的影响

对强度等级为C40掺粉煤灰和C70掺硅灰的两种混凝土进行了模拟火灾的一定时间的高温加热,研究了两种混凝土在高温后不同养护条件下84 d内的强度变化和微观结构的变化。结果表明:C40混凝土高温后强度提高,在养护一段时间后强度会持续下降,之后强度又出现回升,基本上能到达到为加热前的强度水平;C70混凝土高温后强度下降,在养护后强度持续的升高,最后能达到加热前强度的90%以上。外部水进入混凝土内部的速率对混凝土的强度变化有重要的影响,特别是对C40混凝土强度下降的速率以及最低强度影响显著。     

磷酸盐修补材料粘结强度影响因素研究

研究了养护条件、界面处理、旧混凝土表面不同湿态及基材种类等因素对磷酸盐修补材料粘结强度的影响。试验结果表明,养护条件对粘结强度有较大的影响,室温养护下强度高,水养护不利于强度的发展。界面处理对粘结强度有很大的影响,粘结面凿毛有利于提高粘结强度。基材为磷酸盐修补材料的粘结强度要明显高于基材为混凝土的粘结强度。     

泵送混凝土实体强度检验的试验研究

结构中的混凝土实体强度与标准养护强度是有差别的,施工质量验收规范已提出了用同条件养护试件强度检验实体强度的要求。通过对唐山地区同条件养护混凝土试件强度的系统试验研究,探讨了其增长规律,并在此基础上建议了反映实体强度的同条件养护试件强度检验的等效养护龄期及强度折算系数。     

Zustandsuntersuchung und Instandsetzung am Hauptdach des Hauses der Kulturen der Welt in Berlin

The main roof of the ”Haus der Kulturen der Welt“ in Berlin Which is very well‐known on account of its history and striking structural design – was to be inspected by the author to determine its condition and analysed with regard to the durability of the existing liquid synthetic sealant. The roof structure consists of a biaxial, curved area‐covering structural element with circumferential edge beams of pre‐stressed lightweight concrete. This is the result of the reconstruction between 1984 and 1987 following a partial collapse of the then Berlin Congress Hall in 1980. The very thin roof shell is also made of lightweight concrete and, like the edge beams, has a polyurethane‐based spray‐on seal that was specially developed for this purpose as protection against the ingress of moisture. The reason why this, at the time, novel type of seal was chosen was that it should take into account the fact that the roof design urgently needed some kind of protection against moisture that had to compensate the expected changes shape and crack movements of the roof with no damage. The following article reports on the nature, scope and main results of the analysis of the condition of the roof seal, edge beams and abutments. It will also describe the repair recommendations resulting from the investigations, which form the basis of the execution of work at the present point in time. Apart from presenting the technical principles and special features of the building that have to be taken into account during any repairs, the special features of the execution will also be addressed.     

Magnetoelastische Spannkraftmessung in Bauwerken

Magnetoelastic Measurement of Prestressing Force in Civil Structures The knowledge of the tensile force of prestressing steel elements and its reliable and non‐destructive determination are of essential importance for the assessment of the structural health condition of prestressed concrete structures and tie‐back systems in terms of structural safety, serviceability and durability. For the evaluation of the prestressing force in steel tension members, the measurement technique presented in this contribution is using the magneto‐elastic effect (ME‐effect) of ferromagnetic materials. This effect describes the reverse‐proportional correlation between the mechanical stress and the magnetic properties of ferromagnetic materials. The cylindrical coiled sensors pushed over the tendon and the measuring device developed and practically optimized at the iBMB/MPA of the TU Braunschweig enable a fast and reliable measurement of the prestressing steel force after an initial calibration. In this contribution first the state of the art of prestress measurement techniques for steel tension members is presented. Afterwards, the ME‐measuring method with the basics and merits of magneto‐elastic prestressing force identification is shown. Further recent research results as well as several building applications will be discussed.     

Ecological succession in mountain lake ecosystems of Southern Siberia after the introduction of the peled – Coregonus peled (Gmeli, 1778)

Abstract

This article summarizes a long-standing study of the process of introduction of the peled to the Southern Siberian mountain lake ecosystems. The peled has adapted to changes in food supply. Pressure of the euryphagous peled caused the substitution of larger forms of zooplankton by smaller ones. Similar changes occurred in the content of phytoplankton. Succession of zoobenthos in the littoral part of the lakes manifested itself as the decrease in the total biomass, in its part of zoobenthos (Gammarus) and as the increase in the biomass of other groups. The opposite changes were encountered in the profundal zone of zoobenthos (the decrease in the total biomass owing to the existence of larger forms of alpha-polysaprobes). The restructuring observed in various communities signifies the substantial changes in the whole process of generation and transformation of organic substance in the mountain ecosystems with the dominance of the introduced peled.     

Alternative Methods of Procurement for Works of Water and Environmental Management

The paper considers methods of procurement for the construction of water- and sewage-treatment works other than the traditional use of the ICE 5th Edition Conditions of Contract and Bills of Quantities. This is as a consequence of the speed at which schemes are currently required within the water industry.
The paper particularly focuses on the use of target contracts, using the Institution of Chemical Engineers'Green Book form, and considers various types of target. It also discusses the form which tender documents may take, and how targets may be calculated.
Tendering procedures, including the use of two-stage tenders and negotiated targets, are considered, as are the procedures for cost monitoring and the financial management of the contract. Finally, the role of the engineer and quantity surveyor is considered.     

基于点云的钢筋数量和间距自动检查算法

为改进钢筋骨架质量自动检查方法,提出了基于点云的钢筋骨架中钢筋数量和钢筋间距的自动检查算法。该算法在获取钢筋骨架实际点云和设计点云的基础上,首先对这两片点云分别进行降采样,以得到空间密集程度相同的钢筋骨架实际点云和设计点云; 其次,对降采样后的钢筋骨架实际点云和设计点云使用基于主成分分析(PCA)的方法进行粗配准。由于粗配准后的钢筋骨架实际点云和设计点云的配准精度较低,无法直接用于钢筋数量和钢筋间距的检查,对粗配准后的钢筋骨架实际点云和设计点云进行精配准。最后,基于精配准得到的钢筋骨架实际点云和设计点云,依次对钢筋骨架中的钢筋数量和钢筋间距进行检查。结果表明:精配准后的钢筋骨架实际点云和设计点云的配准精度较高,可以用于钢筋数量和钢筋间距的检查; 该算法对钢筋数量检查的准确率为100%,对钢筋间距检查的准确率为80%; 应用该算法可以有效提高复杂钢筋骨架中钢筋数量和钢筋间距检查的效率,降低人工成本。     

Application of sonic and radar tests on the piers and walls of the Cathedral of Noto

The authors applied systematically sonic tests, radar tests and other diagnostic techniques on the remaining walls and piers of the Cathedral of Noto. The experimental survey was carried out by the Laboratory of the DIS, Politecnico of Milan (Person in Charge: Prof. Binda, Prof. Baronio) in collaboration with the designers (Ing. R. De Benedictis, Arch. S. Tringali) and the experts working on the reconstruction. The Prefettura of Siracusa founded the research. The right aisle and most of the dome of the Cathedral collapsed in 1996. The aim of the research was to verify the state of damage and the possibility of conservation of the walls and piers in view of the reconstruction of the damaged part of the Cathedral. Furthermore, the sonic tests were used to control the effect of grout injection used as a possible technique for repair of the damaged masonry (Proceedings of the Conference on Nondestructive Evaluation of Civil Structures and Materials, Boulder, Colorado; (1992) 329; Proceedings of the Sixth Conference on Structural Faults and Repair, 3 (1995) 195). In the following the results will be reported and the reliability of the tests will be discussed as it was confirmed by the use of other complementary diagnosis techniques (Proceedings of the Sixth International Conference on Structural Studies, Repairs and Maintenance of Historical Buildings, STREMAH 99, Dresden, Germany, (1999) 323).     

机制砂在隧道耐久性混凝土运用中的质量控制

从母岩的选料、级配控制、石粉和泥土含量控制三个方面阐述了控制机制砂质量的重要性，并提出了可将隧道混凝土机制砂的石粉含量限值放宽到10％的建议，以促进耐久性混凝土的研究。     

土体干缩开裂过程的边界效应试验与离散元模拟

为了探究土体干缩开裂过程的边界效应问题,采用不同底面粗糙度的容器开展了多组干燥试验,发现干缩裂隙存在从顶面向下和从底面向上两种典型的发育形式。并且,裂隙发育程度与土样/容器界面接触条件密切相关,从而验证了裂隙发育过程的边界效应。通过理论分析,阐明了上边界的蒸发条件及下边界的接触条件对裂隙发育形式的控制作用。为了能更深入地理解土体干缩开裂边界效应的内在机制,在试验的基础上建立离散元模型,创新性地引入了沿深度的失水速率梯度参数,模拟土样上边界的蒸发条件变化。通过设置底面摩擦系数,模拟土样下边界的接触条件变化。将模拟结果与试验结果进行了对比分析,发现二者具有较好的吻合度。总体上,土体干缩裂隙的发育过程是顶面蒸发失水与底面摩擦两种边界条件共同作用的结果。当底面摩擦系数相对较小时,裂隙发育由蒸发失水主导,大部分裂隙由顶面向下发育。随着底面摩擦系数的增加,底面接触条件对裂隙发育过程的主导作用逐渐增强,由底面向上发育的裂隙数量所占比重也相应增加。     

堆土加卸载与基坑开挖叠加对既有隧道变形的影响研究

针对堆土加卸载与基坑开挖叠加效应导致既有地铁隧道变形较大的问题,建立考虑加卸载叠加效应影响的三维空间分析模型,研究不同堆土加卸载叠加基坑开挖卸载模式对邻近地铁隧道变形规律的影响,探讨隧道在堆土加载、移土卸载再叠加基坑开挖下的变形规律。结果表明:正上方堆土加卸载对隧道的竖向位移影响较大,是侧向堆土加卸载的3倍～5倍; 在经历堆土加卸载后,隧道会残留不可忽视的变形,其残留竖向位移约为加载后位移的62%; 堆土加卸载叠加侧方基坑开挖时,隧道变形受基坑开挖深度的影响较大,大于隧道埋深的开挖阶段会加剧隧道变形; 4种叠加模式中,正上方堆土加卸载-侧方基坑开挖卸载隧道最终竖向位移最大,约17 mm,侧方堆土加卸载-异侧基坑开挖卸载隧道最终水平位移最大,约8 mm,邻近隧道施工时应充分考虑叠加效应的影响,尽量避免这两种情况。     

项目临时性组织性质的研究

指出从组织论角度看项目具有临时性组织的性质，对项目的定义进行了思考，从生产功能、代理机构、代理不确定性事务及项目管理者角度论述了作为临时性组织的项目，以促进对项目的理解和研究。