Zum nachträglichen Kürzen und Verankern von glatten Spanngliedern im Verbund

Investigations on the Cutting and Anchoring of Existing Prestressed Concrete Beams Post Tensioned with Smooth Bars SSB has planned to provide a new lift arrangement for an underground tram station in its existing structural system. For implementing this proposal, it is required to cut existing prestressed concrete beams which presently carry a 3‐lane road. The challenge is that tendons without ribs have to be anchored by bond strength of concrete. Therefore, first of all the bond behavior had to be studied and alternatively a new anchorage device was developed. Besides laboratory tests on bond behavior, one of the prestressing cables in the existing structure was cut at midspan, on which a number of strain gages were pasted in the anchorage zone near the cutting point in advance. Hence, a long‐term monitoring of strain release was carried out under service traffic load as well as under a special static load (48t crane). It was also possible to show, that, under non static loading the anchorage of the prestressing force could be ensured only by bond. Using the results obtained from the push‐in tests for the bond behavior, the results of the field test could be predicted very well. Furthermore, laboratory tests for the new anchorage device under static and cyclic loading were performed. The results show the feasibility of the proposed procedure. The test programme was rounded off by numerical investigations on the stresses in the anchorage zone.     

Schubsteifigkeit zweiseitig gelagerter Stahltrapezbleche

Shear stiffness of trapezoidal steel sheets with two edges fastened. Profiled sheeting is often fastened only at the two edges which are normal to the span of the profiles according to its uniaxial load bearing behaviour for transverse loading and due to high effort in achieving all‐sided fastening. According to available design codes it is not possible to use the shear stiffness of this kind of diaphragms to stabilise beams against lateral torsional buckling. Therefore the effect of unsupported edges parallel to the span is investigated numerically and experimentally. This nonlinear investigation includes the flexibility of the fasteners. The numerical results agree well with the test results up to failure load. A knock‐down‐factor depending upon the a/b‐ratio and the shear stiffness of the diaphragm supported along 4 edges is obtained from the parametric investigations. The application of this knock‐down‐factor to the shear stiffness of the diaphragm supported along 4 edges gives that for the diaphragm supported along 2 edges. All this applies for the design load according to [6]. The ultimate loads of the diaphragms are much higher than these design loads.     

Umgelenkte Lamellen aus kohlefaserverstärktem Kunststoff für freistehende Spannglieder im Konstruktiven Ingenieurbau

Behaviour of Deviated CFRP‐Strips Carbon fiber reinforced plastic (CFRP) has a number of excellent properties with a wide range of application possibilities in structural engineering. In the last two decades, the use of CFRP‐Strips as a reinforcement for concrete members has emerged as one of the most exciting and promising technologies in structural engineering. These strips could also be used for external prestressing of bridges or for unstrained ceilings in high building structures. Therefore the problematic of the end‐anchorage and the deviation of the strips, due to the sensitivity of the carbon fibers to transverse loads, has to be solved. Several research institutions have already suggested solutions for CFRP‐strip anchorage. In this paper the results of an experimental program of deviated CFRP‐strips at deviation saddle are introduced. The effects of the different parameters on the load bearing capacity, strain responses up to failure and the failure mode of the CFRP‐strip at the deviation saddle are investigated.     

Verbundverhalten von Vollgewindeschrauben in Brettschichtholzbauteilen

Bond behaviour of self‐tapping screws being used as reinforcement in glue‐laminated timber elements – Part 2: Analytical and numerical investigations as well bond model derivation for the calculation of anchorage length In favor of the investigation of bond behaviour, force transfer and anchorage length of self‐tapping screws, several tests have been realized at the Chair of Structures and Structural Design in cooperation with the Institute for Building Material Research of the RWTH Aachen University. The experimental investigations comprise more than 160 pull‐out tests of screws with long embedment length and over 84 load distributions tests. Additionally, several tests displaying the effect of longitudinal cracks in the surrounding wood as well as the effect of the screw tip have been conducted. Through various analyses of the bond behaviour, the experimental investigations form the basis for the calibration and evaluation of the numerical models and allow a prediction of the force transfer of the screws in glue‐laminated elements. Design rules that enable the application of the self‐tapping screws as reinforcement in timber elements have been derived from the knowledge obtained in the experimental and numerical investigations. This paper, which results from a research project funded by the German Research Foundation [1], presents the results of investigations on the bond behavior of self‐tapping screws in glue‐laminated timber elements. Part 1 elaborates on the experimental investigations [2] whereas part 2 illustrates the numerical analyses and presents a bond model, which enables the design of the anchorage length and the safe application of the screws as reinforcement in timber elements.     

Tragverhalten und Bemessung windbelasteter Kreiszylinderschalen mit diskreter Verankerung

Structural behaviour and design of wind‐loaded cylindrical shells with discrete anchorage. Stubby cylindrical shells are often used as storage tanks. Because of their large diameters, in general they are not anchored continuously, but discretely. Nevertheless, the previous investigations of the stress and strain state of the shell were done almost exclusively by assuming a continuous anchorage. In the contribution, it is analyzed for the critical load case wind on the emptied tank, how the internal forces and the buckling strength verification are changed, if the discrete anchorage is realistically taken into consideration at the tensile zone of the base cross section. The differences are quantified. From it, it can be concluded, that a continuously anchorage may be used in the mechanical model, if the interaction buckling strength verification of the stress design is only exploited up to 90%.     

蒙皮效应考虑开洞影响的研究

应用有限元分析方法对闭口和开口蒙皮体及整体轻钢结构的抗剪性能及受力状态进行了研究,分析了蒙皮效应对整体结构的影响.最终确定了轻钢结构中最佳的门窗洞口位置. .     

自攻螺钉、拉铆钉连接的受力蒙皮抗剪性能试验研究

本文对111个自攻螺钉、拉铆钉连接及14块由这种连接件连接的蒙皮板进行了抗剪性能试验,并分析了其抗剪强度、抗剪刚度、工作特点、破坏模式以及变更连接件布置方式、压型板跨度对受力蒙皮性能的影响。试验结果与国外的试验和理论分析结果符合较好。文中还提出了将压型钢板等效为正交各向异性板,用有限元法分析蒙皮的抗剪性能,所得蒙皮连接件内力分布规律,有助于进一步研究建立我国的蒙皮设计计算方法。     

蒙皮板整体剪切屈曲分析

随着蒙皮板与周边构件连接的加强以及复合楼板或复合墙体中压型钢板的使用,蒙皮板在面内剪力作用下的整体屈曲有可能成为控制破坏形式。另外,目前很少有研究者对多种边界条件下蒙皮板的整体屈曲问题进行系统的研究。利用有限元方法对至少每波相连的蒙皮板的弹性屈曲进行分析,分别考虑了压型钢板的截面形状、波高和钢板厚度对整体屈曲性能的影响;采用矩形截面的压型钢板对常见的焊接和自攻螺丝连接形式包括点焊、槽焊、波谷连续施焊、波峰自攻螺丝连接、波谷自攻螺丝连接以及波峰波谷自攻螺丝连接在不同的波高和波距影响下的整体屈曲进行考察,并对简化公式的应用予以探讨,给出小波距低波板的建议边界影响系数。     

冷弯薄壁型钢门式刚架蒙皮效应研究

采用ANSYS软件对冷弯薄壁型钢门式刚架的蒙皮效应作了探讨性研究.对比分析了无蒙皮门式刚架和有蒙皮门式刚架的顶点竖向位移与柱顶水平位移.计算结果表明,蒙皮效应对刚架整体竖向和水平位移都有很大的限制作用.设计时,可以考虑适当放松按平面刚架计算的刚架柱顶水平位移值,来考虑蒙皮效应.     

Untersuchungen zu dynamischen Eigenschaften verkleideter Stahlskelette

Experimental research on dynamic properties of steel skeleton sheating. Results of dynamic experimental investigations of two‐span steel frame with metal diaphragms filling the walls were presented. Vibration frequencies, vibration form and vibration damping for six types of structure have been determined. First approach of conclusion shows the increase in dynamic stiffness and the increase of frequencies in cased structures in comparison with steel frames without sheathing.     

Kurze Verankerungslängen mit Rechteckankern

Rectangular Anchors with short Anchorage Length The technical approval Z‐15.6‐204 [1] of the Deutsches Institut für Bautechnik gives design rules for the use of Halfen HDB‐E‐headed studs in exterior‐beam‐column‐joints and corbels. The anchorage with headed studs is characterized by a negligible slippage of the reinforcement and is advantageous regarding the load bearing capacity, the detailing and the handling on site. This paper describes the design rules, devided from comprehensive experimental and numerical investigations [2].     

轻钢结构蒙皮效应的应用探讨

初步探讨了轻钢结构中蒙皮效应的作用机理及其应用中的问题 ,讨论了板与檩条的连接构造对蒙皮效应的影响 ,分析了蒙皮效应对檩条抗侧向弯扭的约束作用及对整个建筑抗水平荷载的作用等。     

Experimental study of plate‐reinforced composite deep coupling beams

An experimental study was conducted to investigate the behavior of deep coupling beams of span‐to‐depth ratio (1·17) fabricated according to the newly proposed plate‐reinforced composite (PRC) coupling beam design. Three PRC coupling beams of small span/depth ratio fabricated based on different approaches for load transfers between steel plates and reinforced concrete (RC) were tested under reversed cyclic loading. This paper presents the experimental results and compares the overall performance of these three specimens with two geometrically identical RC coupling beam specimens, one with diagonal reinforcement and the other with conventional reinforcement details, tested by previous researchers. It was found that the performance of PRC deep coupling beams of small span‐to‐depth ratio with properly designed plate anchorage in the wall regions can be comparable to that of diagonally reinforced coupling beams while being able to achieve a higher shear capacity without causing the problem of steel congestion. The proper design approach for the plate anchorage of PRC coupling beams was also identified. Copyright © 2007 John Wiley & Sons, Ltd.     

Seismic behavior of connections composed of CFSSTCs and steel-concrete composite beams — finite element analysis

Based on the experimental results of connections composed of concrete-filled square steel tubular columns (CFSSTCs) and steel-concrete composite beams with interior diaphragms, exterior diaphragms, or anchored studs, 3-D nonlinear finite element models were established to analyze the mechanical properties of these three types of connection using ANSYS. Finite element analyses were conducted under both monotonic loading and cyclic loading. The load-displacement and shear force-deformation curves of the finite element analyses are in agreement with those of the tests in terms of strength and unloading stiffness. Parametric analyses were conducted on the connections with exterior diaphragms under monotonic loading to investigate the influences of axial load ratio, width to thickness ratio, and dimensions of exterior diaphragms on the connection behavior. It was found that the strength and stiffness are less influenced by the axial load ratio and the dimensions of the exterior diaphragms, but more influenced by the width to thickness ratio of the steel tube under shear failure mode.     

蒙皮板整体剪切屈曲性能试验及有限元分析

在蒙皮体的各种破坏形式中,整体剪切屈曲破坏是具有控制作用的破坏形式之一。对目前国内常用的YX20-166-830型压型钢板组成的6个不同边界连接的蒙皮板进行了抗剪试验研究,探讨边界连接形式对整体屈曲荷载的影响。在试验的基础上进行了有限元分析,将试验结果、有限元计算结果和理论结果进行了比较。屈曲荷载的试验值与有限元计算值相差较小,可见有限元计算模型可以作为进行蒙皮体抗剪性能分析的辅助手段。另外,通过屈曲荷载的试验值和简化公式值比较,得到了边界连接形式对整体屈曲荷载的影响,进一步完善了蒙皮板整体剪切屈曲的计算公式。     

自攻螺丝连接受力蒙皮体抗剪性能试验研究

受力蒙皮是考虑房屋屋面、墙面的压型钢板与框架、檩条进行可靠连接而共同工作的结构体系。本文对国内常用的V-840型压型钢板采用自攻螺丝连接的受力蒙皮体进行了抗剪试验研究,分析了不同间距自攻螺丝连接的受力蒙皮体的破坏形式及抗剪性能,并提出了不同间距布置的连接件对蒙皮体抗剪性能的影响,以及此类蒙皮体考虑蒙皮效应的条件。     

Measurement of the geometric initial imperfections in diaphragms

A method, using a new surveying technique, is used for the measurement of the geometric initial imperfections in box girder diaphragms. The method, accurate to ±0·1 mm, may be used on diaphragms contained in a box girder where contact with the surface of the diaphragm is difficult or impossible or inadvisable due to the presence of strain gauges.     

深基坑嵌岩支护技术应用研究

嵌岩地连墙近几年开始应用到深基坑的支护中,通过工程实例介绍了其发展概况。分析了传统的m法应用于嵌岩支护结构设计的难点,并提出了相应办法;介绍了嵌岩地下连续墙的成槽工艺、连接节点构造以及封水措施并以实际工程为背景介绍了嵌岩深基坑的信息化施工,得出了一些可供工程应用的结论。     

方钢管混凝土柱内隔板式节点的抗弯承载力研究

为了研究方钢管混凝土枉内隔板式节点的抗弯受力性能，完成了3个方钢管混凝土柱内隔板式节点的低周反复荷载试验。在此基础上，研究了轴压作用对方钢管混凝土柱内隔板式节点抗弯承载力的影响，提出了3块内隔板情况下节点抗弯承载力的计算方法。同时对梁柱翼缘等宽情况下节点的抗弯受力性能进行了分析，建立了相应的计算公式，计算结果与试验结果进行了对比，吻合良好。试验结果及理论分析对现行规程中的节点抗弯承载力计算公式进行了补充，拓宽了内隔板式节点的适用范围。     

地震作用下锚固参数对岩体边坡锚固界面剪应力分布影响分析

基于FLAC3D软件,以含软弱层的锚固岩质边坡为研究对象,通过修正的cable单元建模和改进剪应力提取方法,利用数值模拟方法系统地分析研究了地震作用下锚固参数对含软弱层岩体边坡锚固界面剪应力分布的影响。研究发现:随砂浆层厚度增加,砂浆–岩体界面脱黏增长,杆体–砂浆界面脱黏减小;随锚杆横截面积增大,锚固界面剪应力向锚头和锚根转移,脱黏增长;适当增加锚固段长度和减小锚杆间距均有利于边坡稳定;一定的锚固段长度下宜适当增大锚杆倾角。揭示了地震作用下锚固参数对边坡锚固界面剪应力分布和锚固机理的影响,对边坡锚固的设计施工具有重要参考价值。