围压和固结应力比对砂卵石土动力特性的影响

通过砂卵石土室内动三轴试验，对砂卵石土的动力特性进行了较为深入的研究，得到了在不同围压、不同固结下砂卵石土的动强度和动模量的变化规律。试验结果表明，围压对动强度和动模量都有明显的影响，不同的固结应力比条件下，动强度及动模量变化也较大。     

围压和固结应力比对砂卵石土动力特性的影响

通过砂卵石土室内动三轴试验，对砂卵石土的动力特性进行了较为深入地研究。得到了在不同围压、不同固结下砂卵石土的动强度和动模量的变化规律。试验结果表明，围压对动强度和动模量都有明显的影响，在不同的固结应力比条件下动强度及动模量变化也较大。     

砂卵石土动本构关系的试验研究

通过砂卵石土室内动三轴试验,对饱和砂卵石土的动本构关系动力特性进行了较为深入的研究,主要分析了围压、固结比和动荷载振动频率对砂卵石土的动本构关系影响的变化规律.试验结果表明,饱和砂卵石土的动本构关系可用双曲线表示,围压、固结比参数对其影响较大,随着围压或固结比的增大,动本构关系曲线逐渐偏向应力轴,而动荷载振动频率对砂卵石土的动弹模量影响很小.     

砂卵石土动强度与动弹性模量试验分析

通过砂卵石土动三轴试验,深入研究了砂卵石土动力特性,得到了砂卵石土的动强度和动模量在不同围压及固结应力比条件下的变化规律。试验结果表明,围压是动强度提高的重要影响因素,固结应力比不同的条件下,动强度及动模量变化也较大。     

砂卵石土动强度的试验研究

通过对砂卵石土室内动三轴试验,对饱和砂卵石土的动力特性进行了较为深入地研究。主要分析不同围压、不同固结比和不同振动频率对砂卵石土的动荷载影响的变化规律。试验结果表明,砂卵石土呈现出动弹性模量随动应变的增大而非线性地降低,动荷载频率对动弹性模量影响很小,动弹性模量随着固结比的增大而显著增大的规律。同时,砂卵石土的阻尼比具有随动应变增大而增大,随着围压或固结比的增加而减小的变化规律。     

砂卵石土在动荷载作用下的阻尼比研究

通过对砂卵石土的室内动三轴试验,对饱和砂卵石土的阻尼比动力参数进行深入的研究。主要分析不同围压、不同固结比和不同振动频率对砂卵石土阻尼比影响的变化规律。试验结果表明,动应变对阻尼比有显著影响,阻尼比随着动应变的增大而增大,但随着围压或固结比的增加而减小,同时,阻尼比具有随振动频率的增大而减小的变化规律。     

饱和砂卵石土液化特性的试验研究

通过动三轴试验,对饱和砂卵石土在循环荷载下的液化特性进行了系统研究.在饱和砂卵石土的振动时程曲线分析基础上,得到饱和砂卵石土的动应力幅值随振动时间推移有衰减且衰减速率逐渐增大的规律特性;依据孔压演化理论,结合试验结果,对饱和砂卵石土的液化规律进行了系统分析,归纳出砂卵石土发生液化时含水量限制条件,与液化状态中的土样动应变状态的规律.此结论可为基础工程等土工构筑物抗液化措施提供参考.     

砂卵石土在动荷载作用下的动弹性模量研究

通过砂卵石土室内动三轴试验,对饱和砂卵石土的动弹性模量动力参数进行了较为深入的研究.主要分析不同围压、不同固结比和不同振动频率对砂卵石土的动弹性模量影响的变化规律.试验结果表明,动应变影响动模量成倍增减,同时,动模量随着固结压力的增大而增大,固结应力比对动模量有着和固结压力一样的影响规律,而频率对饱和砂卵石土动弹模的影响较小.     

邓肯—张模型对砂卵石土适用性的试验研究

通过三轴试验,本文针对邓肯—张模型对砂卵石土的适用性进行了分析研究。试验结果表明,砂卵石土的体变在经历初始的体缩段后,随着轴向应变增加变为以体胀为主,并且随着围压增大,体胀逐渐减弱;砂卵石土的强度和切线弹性模量可以根据邓肯—张模型来较合理地确定;邓肯—张模型不能够较好地描述砂卵石土的体变特性与泊松比参数,切线泊松比应优选本文所拟合公式。     

砂卵石-砂土复合试样大三轴数值试验及验证

基于北京地下直径线典型砂卵石地层试样的大型三轴排水试验结果,利用通用有限元软件ABAQUS采用Mohr-Coulomb本构模型对复合土样三轴试验的破坏过程进行了数值模拟,基本上再现了土样三轴试验的偏应力-应变关系,说明数值计算能够有效地模拟土样的三轴试验。在此基础上,通过不同砂层厚度试样的数值试验,探究了砂层对复合试样强度和破坏规律的影响。计算结果表明:试验围压,试样中砂土的位置及厚度对于砂卵石-砂土试样的强度及破坏模式有显著的影响。     

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.     

基坑开挖对邻近任意角度建筑物影响的有限元分析

实测结果表明,邻近基坑的建筑物与基坑边互不垂直时,基坑开挖将导致墙体同时发生挠曲变形与扭转变形。三维有限元分析表明,对与基坑边成一定角度的建筑物,当其跨越坑外沉降槽最低点或沉降曲线上凸区域时,建筑物所产生的扭转变形最为显著。随着建筑物与基坑距离的变化和建筑物纵墙与基坑边之间夹角的变化,当建筑物位于天然地面沉降挠曲程度较大的位置时,建筑物的挠曲变形对墙体拉应变起主要作用,墙体最大拉应变发生在建筑物纵墙垂直于基坑边,即纵墙与基坑边相互垂直时是建筑物的最不利位置;而当建筑物位于天然地面挠曲程度较小的位置时,墙体的拉应变源于挠曲变形与扭转变形的共同作用,纵墙墙体的最大拉应变将发生在与基坑边成一定角度的建筑物纵墙上,此时纵墙与基坑边垂直并不是建筑物的最不利位置。     

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.     

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.     

Beurteilung der Tragfähigkeit von geschädigten Stahlbetonbrücken auf der Grundlage der Ergebnisse einer Bauwerksprüfung

Structural Reliability Assessment of Damaged Reinforced Concrete Bridges on the Basis of the Results from a Bridge Inspection The regular bridge inspection is of high importance for the reliable use of the infrastructure. This paper describes and explains a method with supports the engineers of a bridge inspection in the assessment of the damaged bridges during or directly after the inspection. Based on this initial estimate the urgent measures i.e. a lower permitted bridge class can still be carried out before more detailed inspections and calculations have been done. The reliability analyses for the damaged bridges are carried out using first order and second order reliability method (FORM and SORM). The probability of failure, p_f or the safety index, of the system respectively are the main results of the calculation procedure. This paper shows the approach and the application with an example. Particularly in the communal sector the method can be helpful, because it can not be assumed that in all cases the regular bridge inspections and the appropriate maintenance have been carried out.     

Bewertung einer alten genieteten Stahlbrücke – Die Bösebrücke in Berlin

Evaluation of an old riveted steel bridge – The Böse‐Bridge in Berlin, Germany. This report is about the recalculation of the Böse‐Bridge in Berlin which was built between 1912 and 1916. A special feature of this three‐bayed truss arch bridge is the nickel steel used in the main bay. Different models have been used to recalculate the main structure, the truss nodes and the carriageway slab. The static analysis is based on the semi‐probabilistic concept. As a result of this recalculation the construction was classified to have the bridge capacity 30‐30 according to DIN 1072. Finally, this report concludes by determining the remaining lifetime depending on the concept of the Wöhler curves.     

Feldversuche mit dem Brückenklappverfahren

Field Tests with the Balanced Lift Method As a counterpart to the lowering arch construction method the “balanced lift method” for bridge girders is suggested. The bridge girders can be built in combination with the pier using climbing forms in a vertical position. Therefore, during the production no bending stresses are generated in the girders. Thus, the balanced lift method allows lower costs and a shorter construction time than the traditional balanced cantilever method. The span of the bridge girders is reduced by the compression struts or tension ties which results in substantial savings in construction materials compared to the balanced cantilever method for bridge construction. The proposed method will be especially advantageous for bridges with high piers. The range of the span length for the application of the balanced lift method ranges between 50 m and 250 m.     

捕捉“光线”——解读葡萄牙“梅莉德斯周末住宅”

本文以阿雷斯·马特乌斯兄弟设计的梅莉德斯周末住宅的院子为线索,通过其与冈卡罗·伯内设计的“阿维罗大学的校长楼”进行比较,揭示了“光线”是其设计的核心。这为我们研究葡萄牙建筑提供了更为全面的视野。但更为重要的是,文章表明了类型学的方法论在中国大规模快速建造的今天更具现实意义。     

Entwicklung eines baupraktischen Näherungsverfahrens zur Beurteilung der Zuverlässigkeit von Massivbrücken auf der Grundlage der Ergebnisse von Bauwerksüberprüfungen

Im vorliegenden Teil 2 des Beitrags wird die Entwicklung des baupraktischen Näherungsverfahrens für die Beurteilung der Zuverlässigkeit von Massivbrücken im Rahmen der RI‐EBW‐PRÜF vorgestellt. Wesentlicher Inhalt ist dabei die Modellierung der Modellunsicherheit Bauwerksprüfer, da die Bewertung der Mängel und Schäden an einem Brückenbauwerk durch den jeweiligen Bauwerksprüfer einen entscheidenden Einfluss auf die Zustandsbewertung hat. Zudem wird auf die Dimensionsanalyse von Grenzzustandsfunktionen näher eingegangen, da damit bei geschickter Normierung eine allgemein gültige Anwendung des Verfahrens erreicht werden kann. Die Anwendung des Verfahrens erfolgt mit einem Software‐Tool, das abschließend vorgestellt wird. In Teil 1 des Beitrags wurden die Grundlagen des Verfahrens sowie die Entwicklung der veränderten stochastischen Material‐ und Geometrieparameter infolge Schädigung behandelt. Development of an Approximation Procedure for a Structural Reliability Assessment of Reinforced Concrete Bridges on the Basis of the Results from Bridge Inspection Part 2 of the paper shows the development of the approximation procedure for the reliability assessment of reinforced concrete bridges according to RI‐EBW‐PRÜF. An essential part of this is the development carried out by the model uncertainty bridge inspector, as the respective bridge inspector's individual assessment of the damage of a bridge has a decisive influence on the condition evaluation. Furthermore, the dimensional analyses of ultimate limit states are shown, as the general use of the developed methodology can be achieved with an ingenious standardization. The application of the procedure with the developed software tool is presented in conclusion. Part 1 of the two papers describes the basics of the methodology and shows the development of the stochastic models for the material and geometry parameters which have changed as a result of damage.     

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.