粉煤灰掺量和龄期对砼碱骨料反应的因素分析

针对混凝土的新病害——碱骨料反应这一问题,对配制的高性能混凝土原材料进行了岩相法测试和快速砂浆棒试验,得出了该骨料具有碱活性。通过掺加不同比例粉煤灰代替水泥制作的砂浆棒试验,得出了砂浆棒膨胀率与粉煤灰的掺量及龄期有关。粉煤灰的掺量(质量分数≤30%)越多,龄期越短,砂浆棒膨胀率越小。结合数理统计分析方法,研究了粉煤灰和龄期两种因素对混凝土碱骨料反应的影响程度。研究结果表明:粉煤灰掺量和龄期均对混凝土碱骨料反应有非常显著的影响。在混凝土施工中,掺入适量的粉煤灰对抑制碱骨料反应是有效的。     

粉煤灰对混凝土中碱-骨料反应的影响

影响混凝土中碱-骨料反应的主要变数,是水泥中碱金属的数量.粉煤灰在减轻混凝土中碱-骨料反应损坏的效率方面,则取决于粉煤灰中有效碱的含量、水泥的取代百分率和水泥中碱的含量.对于有劣性极限的拌合物,水泥的含碱量越低,劣性极限就越高.粉煤灰中的有效碱金属,是影响混凝土中碱-骨料反应的一个因素.     

高性能混凝土碱骨料反应试验研究

碱骨料反应是影响混凝土耐久性的主要因素之一。对雨季处于潮湿环境和冬季处于除冰盐环境中的高性能混凝土桥梁板,根据其混凝土配比计算其碱含量超过国家规定限值,根据岩相法和快速砂浆棒法判断其骨料具有碱活性,具有发生碱骨料反应的条件。采用掺加30%等量水泥的粉煤灰可有效降低混凝土中单方碱含量,并能有效抑制碱骨料反应。     

浅变质岩骨料碱活性特征及抑制措施

针对黔东南不同地区浅变质岩的岩性和骨料碱活性,研究了混凝土碱含量对碱骨料反应(AAR)的影响,并分析了试样的微观表面形貌及化学组成.结果表明:黔东南地区浅变质岩饱和抗压强度的离散性较大,各组岩石均为硅酸盐类岩石;未经粉煤灰抑制处理的浅变质岩骨料砂浆试件14d膨胀率全部超过0.1%,均存在潜在的碱-硅酸反应(ASR)危害;粉煤灰对碱骨料反应的抑制作用明显,经粉煤灰抑制处理的浅变质岩骨料砂浆试件14d膨胀率均有所降低,且大部分未超过0.03%;混凝土碱含量越大,碱骨料反应越快速,反应周期越长,膨胀率越大,最佳碱含量应控制在1.0%以内.扫描电子显微镜-X射线能谱(SEM-EDS)结果显示:与未发生碱骨料反应的砂浆试件相比,已发生碱骨料反应的砂浆试件中骨料表面有蜂窝状的碱-硅酸凝胶产物生成,骨料表面有细裂纹,并出现了Si和Na元素富集现象.     

初探混凝土成分与碱骨料反应产物性能之间的关系

本文指出:可以通过分析混凝土中 N/S、C/S、N/C与膨胀值间的关系,调整C、N、S间的配比,使碱骨料反应主要生成钙—碱—硅酸凝胶,从而达到抑制碱骨料反应对混凝土破坏的目的。在此基础上,探讨了粉煤灰抑制混凝土碱骨料反应破坏的两种作用。     

掺加粉煤灰预防公路工程混凝土碱-骨料反应技术经济分析

碱-骨料反应是影响混凝土耐久性的主要因素之一。掺加粉煤灰能有效抑制碱-骨料反应。掺加不同比例粉煤灰代替水泥制作砂浆棒,测试其14 d膨胀率均小于规定数值,且掺加30%粉煤灰时膨胀率最小。对掺加不同比例粉煤灰制作不同混凝土强度进行了经济分析表明:混凝土强度越高,经济效益越明显。     

混凝土骨料的碱活性检验及抑制试验研究

采用岩相法、砂浆棒快速法进行混凝土骨料的碱活性检验及掺加粉煤灰的碱-硅酸反应活性抑制试验.结果表明,漕河渡槽混凝土中掺入20%～50%的粉煤灰,能有效抑制碱-硅酸反应.     

粉煤灰混凝土与碱——骨料反应若干问题的探讨

本文首先介绍了国外有关粉煤抑制碱——骨料反应的研究情况。通过对含活性骨料的粉煤灰混凝土的水化及反应过程分析,作了若干推论,认为粉煤灰抑制碱——骨料反应是有条件的。最后,提出了有待进一步研究的若干问题。     

矿物掺合料对碱骨料反应的抑制效果研究

活性掺合料取代部分高碱水泥,不仅可减少混凝土的有效含碱量,还能产生物理化学作用,抑制碱-骨料反应。本文利用快速砂浆棒试验方法,探讨粉煤灰、矿渣粉、沸石粉在本地区预防混凝土碱硅酸反应中各掺合料的适宜量。粉煤灰或沸石粉取代水泥20%以上,高炉矿渣粉取代水泥为50%以上就可以有效预防混凝土碱硅酸反应。     

碱-石英霏细岩反应的控制

本文采用X射线衍射、岩相观测和骨料碱活性检验方法对工程拟将使用的石英霏细岩骨料进行了碱活性检验和抑制碱骨料反应的措施研究.得到在该霏细岩中含有很少量微晶和雏晶的石英,该岩石为弱碱活性骨料.根据砂浆棒快速法检验骨料碱活性的结果,由28 d的膨胀率可最终确定该岩石骨料仍可定为非碱活性骨料.为了提高混凝土的耐久性防止碱骨料反应的发生,掺入25%粉煤灰能有效地抑制碱与石英霏细岩骨料之间的反应.     

Untersuchungen zur Genauigkeit von magnetisch induktiven Betondeckungsmessungen

Assessment of the accuracy of concrete cover measurements using Eddy Current devices The use of non‐destructive testing in civil‐engineering (NDT‐CE) is well established to assess as‐built drawings for existing structures as well as for quality assurance of new buildings or in case of concrete repair. To gain reliable results the choice of the appropriate testing method in combination with the correct data assessment is essential. Hence this article starts with the basics of the two typical testing methods for concrete cover measurement with high precision. Methods based on Eddy Current and based on Radar are different. The strengths and limitations of both methods are presented. In the second part the achievable accuracy of concrete cover measurements using Eddy Current will be assessed for the most important parameters that have been varied in a wide range. It is shown how results are influenced by an improper input of the diameter or by the effect of neighbored rebars. At the end of the article it is shown how the deviation of the results can be minimized using the internal neighboring rebar correction of some of the devices. This article does not intend to be a product test rather the influence parameters of measurements close to reality will be identified and quantified how the accuracy of concrete cover measurements is affected.     

The dilution of waste in the wake of a ship

This paper considers the problem of predicting the dilution of waste which has been discharged into the wake of a moving ship. A theoretical model is developed which relates the dispersion of the effluent field to the intensity of the turbulence created by the movement of the vessel. Specifically, the model describes the dependence of the dilution on the speed, dimensions and specific resistance coefficient of the ship.The new theory predicts that the rate of dilution decreases with time after discharge and, as with the empirical IMCO formula, indicates that dilution is more sensitive to the speed of the ship than the volume rate of discharge of waste.     

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.     

Untersuchungen der Auswirkungen eines Vollbrands auf eine Sporthalle

Research of Fire Effects on a Gymnasium An arson attack committed in August 2015 on the gymnasium of the Oberstufenzentrum Nauen school facility built in 2007 led to a full fire and to the complete destruction of the hall. The effects of this fire were recorded with measuring technologies as well as through sampling on‐site. In the course of this, the wooden roof structure was particularly examined and demonstrated a residual load‐bearing capacity in spite of the intensive fire exposure and the resulting significant damage. The remaining support structure of the hall was completely recorded by means of Terrestrial Laser Scanning (TLS) and evaluated in September 2015. Inclinations, cross‐sectional shifts and deformations in the building were able to be calculated with the geodetic measurement method. The results from the laser scanning in combination with the sampling served as a comparison of the theoretical structural evidence with the effects of an actual fire event. In the case of the fire at the Nauen gymnasium, the damage to the load‐bearing capacity was particularly significant in the area of the joining means. The goal of the investigations is a comparison of the technical engineering fire prevention certifications and their theoretical protective effects with the effects of actual fires. This is also a subject of current research projects in the Beuth Hochschule für Technik Berlin, University of Applied Sciences.     

对“建筑”内涵的重新审视与诠释

“建筑”现行内涵的功利与暧昧,是当代建筑粗糙、乏味的主要根源之一.为解决这一问题,首先分析了“architecture”、“营造”与“建筑”三者的内涵.通过将“建筑”与“architecture”及“营造”分别比较,审视了“建筑”的现行内涵;并对其内涵提出了新诠释.     

基于HSS模型隧道近接群桩基础施工影响分析

依托盾构隧道近接侧穿群桩工程建立三维数值分析模型,土体采用小应变硬化(HSS)模型,参数取值借鉴已有研究成果并根据监测位移数据反演,同时考虑土体开挖、衬砌拼装以及盾尾同步注浆等一系列施工工艺措施,并将模拟结果与监测数据进行对比验证,研究了不同工况下地表沉降的形态分布、群桩桩基变形及基桩结构受力,同时考虑地表位移对等代层厚度的敏感性。结果表明:HSS模型能有效预测隧道近接侧穿高架桥桩引起的变形,模拟结果与监测值较吻合; 隧道开挖引起土相对桩产生了滑移,地表沉降及桩身竖向位移在中心线前后各1D(D为管片外径)范围内随推进步数的增加而不断增大,且增加幅度明显减小; 两线推进地表沉降具有叠加效应,最大沉降量增幅达76.8%; 隧道与基桩水平距离越近,引起基桩沉降变化越大,两线推进基桩桩顶沉降增幅达134%; 群桩中各排桩的水平位移变化趋势基本相同,且同排桩的水平位移值相差不大,由于群桩遮挡效应,水平位移值由大到小依次为前排桩、中排桩、后排桩; 桩身水平位移主要在盾构中轴线2.5D范围内,桩身最大水平位移均出现在隧道中轴线附近; 群桩中同排桩桩身附加弯矩及附加轴力沿桩身分布规律相同,桩身最终附加受力与其距离隧道远近有关; 随着注浆充率β的增大,等代层厚度及地表沉降呈线性减小; 穿越段采取的施工工艺方案是有效的,经估算附加弯矩及轴力对桩基承载力的影响在容许范围内。     

采空区隧道二衬受力特性模型试验与耦合分析

由于采空区地层的非连续特征,下穿隧道衬砌往往处在偏心受压的不利状态,后期运营病害相对严重。为了查清不同采空区条件下的衬砌结构受力特性,采用室内物理模型试验和基于连续-非连续耦合数值模拟相结合的方法,开展了相关研究。结果表明:(1)采空区的存在会使二衬结构受到偏压荷载,远离采空区侧总体受力大于近侧,且倾角越大偏压越严重;(2)采煤层厚度、冒落带与初支距离的增大会引起围岩压力的降低,二衬内力减小,安全性提升,当采煤层厚度大于1.8 m时或冒落带与初支间距大于0.8倍隧道洞跨后,采空区对二衬安全性的影响很小;(3)喷层厚度的增加阻碍了围岩变形,引起围岩压力增加,不利于二衬受力和安全性。研究结论对于完善采空区隧道围岩压力计算理论和支护结构设计方法具有理论指导意义。     

论电梯的安全、质量与标准

论述了电梯的特殊性、电梯安全的重要性;分析了政府主管部门、公众和媒体对电梯事故（故障）高度关注的原因;讨论了电梯安全与故障、可靠性的关系,电梯安全标准与安全、质量、运行性能的关系,以及电梯现行标准的性质;界定了安全标准与设计、制造规范的不同及关系;分析了行业及政府主管部门对公众普及电梯知识,客观、冷静地看待电梯故障与安全的重要性;说明了业内专业人员和政府主管部门应引导媒体和公众正确看待作为新型机电运输设备的电梯,认识不同档次电梯产品其质量和可靠性不同的必然性。     

ÖBB Steyrtalbrücke – Belastungsprobe und Langzeitmessungen

ÖBB Steyrtalbridge – Load test and long term measurements At km 65,621 of the railroad track between Linz and Selzthal the Steyrtalbridge was rebuilt in the years 2013 and 2014. The essential design criterion from the client ÖBB Infrastruktur AG was the endeavor of an optimized bridge under consideration of life‐cylce‐cost, which among other things despite a bridge length of 182 m can be designed without high‐maintenance breather switches. Based on the current standards and certain design flexibilities, which are allowed in the codes special ways and techniques were used to calculate the rail tension. With this results of the rail‐structure‐interaction it was possible to design without breather switches. As consequence of the assumptions in the planning process it was necessary to make comprehensive measurements which shall give information of the real behavior of the bridge and compare them with the assumptions and results of the static calculation. Therefor static and dynamic load test were performed before opening to regular traffic. In addition long term measurements were carried out to evaluate the load‐bearing behavior over time and to confirm the calculation approaches for the verification of the rail‐structure‐interaction. In this article the planning of the monitoringsystem, the implementation and results of the load test and the following long term measurements are illustrated.