Tragverhalten von dünnen Bauteilen aus ultrahochfestem Faserfeinkornbeton

The Structural Behaviour of Thin Structural Members made of Ultra‐High Performance Fibre Reinforced Concrete Ultra‐high performance fibre reinforced concrete (UHPFRC) is especially suitable for thin structures or members due to its fine aggregates and high strengths. Based on own test results and theoretical assumptions the load bearing behaviour of UHPFRC under tension, compression and bending is examined. Thereby, the influence of fibre orientation is considered. The validity of the material laws used is checked by recalculating tests. A diagram for the interaction of bending moments and normal forces is presented for UHPFRC. Supplementary, plates and shell structures under combined bending and axial forces are examined using the Finite Element Analysis. The crack patterns and the capacities are compared with results derived from the yield line theory and the possible load redistribution is discussed. In order to demonstrate the practical application, a hot‐water tank for the seasonal storage of heat is analysed. For that the design procedure for nonlinear analyses of concrete structures according to DIN 1045‐1 is taken as a basis and is adapted to structures made of UHPFRC.     

Non‐Waste‐Wachsschalungen: Neuartige Präzisionsschalungen aus recycelbaren Industriewachsen

Non‐Waste wax formwork‐technology Today's possibilities to realize complex free‐form reinforced concrete shapes, curved walls and filigree details require a formwork technology which meets these challenges. High precision with maximum freedom of form is therefore an essential requirement for the formwork of this new, so‐called freeform architectures. Preconditions for this are the 3D digital design and manufacturing technologies, with their help formwork can be designed and manufactured in high precision and with many degrees of freedom in form. This paper describes a research approach using industrial waxes as formwork materials. Due to the nearly 100 % recyclability of the wax, this approach is an economical and ecological manufacturing process for customized free‐form‐members made of concrete.     

Tragverhalten von Verbundbauteilen aus bewehrtem UHFB und Stahlbeton

Ultra‐Hochleistungs‐Faserbetone (UHFB) eignen sich aufgrund ihrer hohen Festigkeiten, des hohen Verformungsvermögens und der geringen Permeabilität zur Verbesserung und Instandsetzung bestehender Betonbauten. Mit dünnen Schichten von bewehrtem UHFB, die auf bestehende Stahlbetonbauteile aufgetragen werden, können der Tragwiderstand und die Gebrauchstauglichkeit deutlich gesteigert werden. In einer umfangreichen Versuchsreihe wurden die Eigenschaften von mit zusätzlich zu den Fasern auch mit Stabstahl bewehrtem UHFB untersucht. Die Bewehrung des UHFB mit Stabstählen ist vorteilhaft, um den Verfestigungsbereich des UHFB zu erweitern, seinen Tragwiderstand zu erhöhen und die Streuung seiner mechanischen Eigenschaften zu reduzieren. Zur Bewehrung können hoch‐ oder niederfeste Stähle mit unterschiedlichen Oberflächenstrukturen zum Einsatz kommen. Abschließend werden zwei Anwendungen vorgestellt. Structural Behaviour of Composite Elements Combining Reinforced Ultra‐High Performance Fibre‐Reinforced Concrete (UHPFRC) and Reinforced Concrete Due to their high strengths, high deformability and low permeability Ultra‐High Performance Fibre‐Reinforced Concretes (UHPFRC) are suitable for the improvement and rehabilitation of existing concrete structures. Thin layers of reinforced UHPFRC that are applied to existing concrete members, increase both the load bearing capacity and the serviceability. By comprehensive experimental studies the behaviour of UHPFRC with additional bar reinforcement was investigated. The reinforcement of UHPFRC is advantageous in order to increase the strain hardening capacity of UHPFRC, its load bearing capacity and to reduce the scatter of its mechanical properties. Low or high strength steel grades with various surface characteristics can be used as reinforcement of UHPFRC. Finally two on site applications are presented.     

Zur Entwicklung der Steifigkeitsmatrizen für dünnwandige Stäbe

On the development of stiffness matrices for thin‐walled members. A glance into the early development of element stiffness matrices for thin‐walled members is given in the present paper and their most mature shapes are shown. Those shapes, the most general and later reduced to two particular forms, refer to the specifics of the classical Vlasov theory of thin‐walled bars [1] as well as to the Bornscheuer systematics of the cross‐sectional properties involved [2]. Appropriate modifications of the relevant matrices are performed and their coordinate system dependence is demonstrated.     

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

In this study, ultrahigh-performance fiber-reinforced concrete (UHPFRC) used in a type B70 concrete sleeper is investigated experimentally and parametrically. The main parameters investigated are the steel fiber volume fractions (0%, 0.5%, 1%, and 1.5%). Under European standards, 35 UHPFRC sleepers are subjected to static bending tests at the center and rail seat sections, and the screw on the fastening system is pulled out. The first cracking load, failure load, failure mode, crack propagation, load–deflection curve, load–crack width, and failure load from these tests are measured and compared with those of a control sleeper manufactured using normal concrete C50. The accuracy of the parametric study is verified experimentally. Subsequently, the results of the study are applied to UHPFRC sleepers with different concrete volumes to investigate the effects of the properties of UHPFRC on their performance. Experimental and parametric study results show that the behavior of UHPFRC sleepers improves significantly when the amount of steel fiber in the mix is increased. Sleepers manufactured using UHPFRC with a steel fiber volume fraction of 1% and a concrete volume less than 25% that of standard sleeper B70 can be used under the same loads and requirements, which contributes positively to the cost and surrounding environment.     

钢纤维形状对超高性能纤维混凝土力学性能的影响

钢纤维通常加工成端部扁平(简称"端平")或端部弯起(简称"端弯")形状以增强纤维与混凝土的粘结锚固,不同纤维形状对超高性能纤维混凝土力学性能影响差异有待试验验证。对纤维体积率分别为1%、2%、2.5%和3%,端平或端弯两种钢纤维制成的超高性能纤维混凝土的性能差异进行了试验研究。试验结果表明:纤维体积率为2%时,端平纤维超高性能混凝土的工作和力学性能最佳;体积率在2%～2.5%时,端平钢纤维混凝土的抗弯强度和断裂能都优于端弯纤维混凝土;由于端弯纤维的端部锚固效果好,端弯纤维混凝土梁在超过峰值荷载后的延性好于端平纤维梁。     

Vom Werkstoff zum Produkt dank innovativer Produktionstechnologie

From Material to Manufacturing thanks to innovative Production Technology There is a very strong need for thin walled elements manufactured out of textile reinforced concrete. These elements can be used as standalone products or they will be used as auxiliary elements in combination with ordinary concrete elements. The success of these products will strongly be influenced by their good functional behaviour and by the costs for the manufacturing. The main focus during the design stage for those products must be to achieve a maximum of efficiency by absolutely minimum material costs. This optimization can only be achieved in combination with a suitable production technique. Especially the manufacturing must be as flexible as possible to fit the always changing demands from the product side. If these requirements can be ensured, then there will be no limits to develop new products and to establish them within the daily market. The range of innovation for those new products will mainly be influenced by innovative production techniques.     

Ganzfertigteile bei der Verbundfahrbahnplatte der Bahretalbrücke – Eine Revision nach Ausführung und baubegleitender messtechnischer Überwachung

Fertigteilbauweisen für die Herstellung der Fahrbahnplatten von Verbundbrücken konnten sich bei kleineren Brücken bereits durchsetzen. Verschiedene Bautypen wurden entwickelt: die VFT‐Bauweise, die Halbfertigteilbauweise, die Ganzfertigteilbauweise. Im Großbrückenbau ist die Anwendung, zumindest in Deutschland, bisher auf einzelne Fälle beschränkt geblieben und eine abgeschlossene Stufe der Entwicklung noch nicht erreicht. Die Ganzfertigteilbauweise, wie sie bei der Bahretalbrücke eingesetzt wurde, stellt eine Möglichkeit dar, die Vorteile der deutlich schnelleren Herstellung der Fahrbahnplatte im Großbrückenverbundbau effektiv zu realisieren. Besonderes Augenmerk ist bei der Bemessung und Konstruktion auf die Rissproblematik zu legen. Die hier aufgetretenen Rissbildungen begründen sich durch die unterschiedlichen Materialeigenschaften und Herstellungszeitpunkte der Fertigteile und der Ortbetonergänzungen. Mit Hilfe des baubegleitenden Messprogramms für die Bahretalbrücke konnten die Rissbildungen sowie insbesondere die Spannungen in den Anschlussbewehrungen der Fertigteile gut nachvollzogen werden. Letztere liegen aufgrund des “Sammelrisseffektes” deutlich über den Spannungen der Ortbetonbewehrung und können nicht einfach am Zustand II‐Querschnitt berechnet werden. Zusammenfassend kann für die Bahretalbrücke eine gute Beurteilung der Bauweise gegeben werden. Prefabricated elements for the floor system of Bahretalbridge. The construction of floor systems of composite bridges, using prefabricated elements in concrete, could already achieve acceptance for smaller bridges. Different types were developed: VFT‐types, semi‐precast construction, precast construction. So far there are only a few cases of prefabricated elements in concrete for bigger bridges in Germany. Using the precast construction presents a possibility to produce floor systems faster and more effective, as done with the Bahretalbridge. Special attention is to be turned to the calculation and construction of the crack formations. The crack formations seen in this particular construction happened because of the different material property and the production time of the prefabricated elements as well as the addition of floor systems. During the construction progress several measurements helped to understand the appearance of the crack formations. The stresses of the reinforcement between prefabricated elements and the in‐situ concrete are much higher due to the effect of accumulated cracks. Summarizing the construction of the Bahretalbridge was done in a decent way and deserves a positive evaluation.     

钢筋超高性能混合纤维混凝土梁力学性能试验研究

超高性能纤维混凝土具有高强度（抗压、抗拉）、高延性和高耐久性的优势,但其抗拉强度仍远低于抗压强度。将端钩型和哑铃型钢纤维按不同比例混合,采取自密实成型和常温标准养护方法,试验研究了配置440MPa纵向钢筋的超高性能纤维混凝土梁。通过12根梁的静载试验,研究了钢纤维体积率为2.0%和2.5%时,不同纤维混合比例的钢筋超高性能纤维混凝土梁的力学性能。试验结果表明：加入钢纤维后梁的极限荷载和延性显著提高;在纤维体积率2.0%时,钢筋超高性能纤维混凝土梁比配筋相同的钢筋混凝土梁承载力提高20%~41%,延性系数提高3.9~6.7倍。钢筋端钩纤维混凝土梁的承载力和延性较钢筋混凝土梁分别提高39%和5.1倍,钢筋哑铃纤维混凝土梁的承载力和延性分别提高20%和3.9倍;钢筋混合纤维混凝土梁的承载力介于钢筋端钩和钢筋哑铃纤维混凝土梁之间。参照现行规范提出了钢筋超高性能纤维混凝土梁正截面极限弯矩的计算方法,计算结果与试验结果吻合较好。图11表6参17     

Dünnwandige,mikrobewehrte Betonbauteile unter Querkraftbeanspruchung

Shear strength of thin‐walled, micro‐reinforced concrete members Within the second funding period of the DFG Priority Programme 1542 ”Concrete Light“ investigations on the load‐bearing behavior of ”Ultra‐lightweight, Thin‐walled Tubular Concrete Members“ are carried out at the IBMB, division of concrete construction of the TU Braunschweig. Due to the currently insufficient amount of investigations dealing with the shear strength of micro‐reinforced concrete (ferrocement) members, fundamental studies had to be performed. These include experimental and theoretical investigations on the shear strength of profiled, thin‐walled concrete beams with micro‐reinforced webs. The performed tests showed the improved cracking behavior and failure notice of micro‐reinforced specimens, when compared to conventionally reinforced specimens. Furthermore, the conservative and thus secure estimation of the shear strength of micro‐reinforced beams using the design approaches provided by EC2+NA or ACI 318 is proven.     

Interactive instabilities of thin‐walled laminated composite pultrusion box columns

The problem of interactive buckling and post‐buckling of intermediate length thin‐walled columns built of laminated plate elements subjected to compressive load has been proposed and solved analytically. Pultrusion columns have wide‐range applications in high‐rise building due to their low weight and high load carrying capacity. Classic stability theory and laminate theory were implemented to prove the existence of mixed‐mode buckling in thin‐walled pultrusion columns. Interactive stability modes can result in lower loading capacity of most compressive members and affects their post‐buckling behaviour in major proportions. Interactive buckling load analysis has been performed by means of a simplified theoretical model and verified by means of numerical analysis. The calculations were carried out for commonly used square section thin‐walled composite columns dimensions. The post‐buckling performance of selected sections has been investigated and an optimum layup configuration criterion for each section has been extracted according to pre‐ and post‐critical behaviour. Copyright © 2010 John Wiley & Sons, Ltd.     

Seismic collapse analysis of high‐rise reinforced concrete frames under long‐period ground motions

Structural damages associated with buckling of longitudinal reinforcing steel and crushing of concrete induce strength and stiffness degradation in reinforced concrete (RC) beams and columns. This paper presents a numerical investigation on earthquake‐induced damages and collapse of typical high‐rise RC buildings model incorporating strength degradation (SD) effects. In a simple finite‐element analysis program with the generalized stress fiber discretization, hysteretic constitutive models primarily dominate the inelastic behavior. Buckling of reinforcing steel and crushing of confined concrete are taken into accounted to the stress–strain relationship of fiber elements. The SD effect in components with small hoop ratio tends to amplify the seismic responses high‐rise RC moment‐resisting frames when the intensity of ground motions exceeds the design level. Buckling of steel rebar and crushing of concrete should be fully considered together with the P‐Δ effect for collapse simulations.     

Bauteile aus ultrahochleistungsfähigem Faserbeton (UHPFRC) und traditionellem Stahlbeton: Eine innovative Lösung zur Instandsetzung und Veränderung bestehender Betonbauten

Structural Elements combining Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) and Concrete: An innovative solution for rehabilitation and modification of existing concrete structures Ultra-High Performance Fibre Reinforced Concretes (UHPFRC) are ideal materials for rehabilitation and modification of existing concrete structures due to their outstanding material properties. Experimental, analytical and numerical studies show that resistance and stiffness are significantly improved in composite “UHPFRC-concrete” elements. No localized cracks are formed due to internal UHPFRC deformations and under service conditions leading to a significant extension of durability. Reinforcement bars in the UHPFRC layer increase significantly the resistance and delay the formation of localized cracks. The structural response under bending can be determined with an analytical cross-sectional model. Three typical configurations are proposed for composite “UHPFRC-concrete” elements for rehabilitation projects.     

超高性能纤维增强混凝土板的受弯性能试验研究

为研究超高性能纤维增强混凝土(ultra high performance fiber-reinforced concrete, UHPFRC)板的受弯性能,进行了10块UHPFRC板的弯曲试验,研究了板的破坏形态、破坏过程、开裂弯矩、极限弯矩以及混凝土和钢筋的应变。在试验结果基础上,建立了考虑受拉区混凝土抗拉强度和应变硬化效应的UHPFRC板受弯承载力计算式。研究结果表明：UHPFRC板的弯曲破坏形态表现为一条主裂缝并伴有多条微裂缝出现,其破坏过程可分为线性变形、微裂缝发展、主裂缝发展和承载力下降四个阶段;UHPFRC板首次出现裂缝时的弯矩为极限弯矩的50%~55%;在设计板时应以变形作为控制指标,且可以少配或不配钢筋以发挥UHPFRC的材料优势;UHPFRC板在受力过程中表现出显著的应变硬化特性。给出了UHPFRC板的弯曲承载力计算式,可以反映受拉区UHPFRC的应变硬化特性。     

Leichte Dachschalen aus Carbonbeton

Light‐weight precast shell elements made of textile reinforced concrete: production, experimental investigations and application potential For single curved barrel‐vault shells made of textile reinforced concrete (TRC) a manufacturing process has been developed that comprises the production of the precast parts as well as tailored solutions for transport and mounting of the filigree shells at the construction site. Furthermore, the load‐bearing capacity of the shells could be verified experimentally using large‐scale tests of prototypes. Saw cuts document the high production quality of the precast parts.The developed methods were successfully applied within the research project by constructing a large‐scale roof structure consisting of five barrel‐vault shells. The cross‐sectional thickness of the 10 m2 large elements amounts to only 2 cm emphasizing the high strength and application potential of TRC.     

Sandwichelemente mit UHPC‐Deckschichten und geschäumten PUR‐Kernschichten

Sandwich Elements Made of UHPC and Foamed Polyurethane Modern building envelopes are sustainable and integral building constructions, which conserve resources, hold favourable physical properties, carry loads, are modular and feature a high freedom of design. Innovative sandwich constructions with concrete facings can meet this demands. The combination of high performance concrete and corrosion resistant reinforcement made of fibre‐reinforced polymers for the outer layers in combination with foamed in pack polyurethane as core material can lead to efficient sandwich elements. The production method is tested with planar sandwich beams and sandwich plates in the first step, which additionally are the basis for sandwich elements with various cross‐sectional shapes. The test results are presented within this paper.     

薄壁空心钢箱混凝土墩抗震性能参数分析

为了研究薄壁空心钢箱混凝土墩的抗震性能,借助OpenSees软件建立有限元模型进行分析计算,将计算结果与试验结果进行比较以验证模型的有效性。在此基础上,建立薄壁空心钢箱混凝土桥墩模型,分析了不同轴压比、长细比、截面空心率、截面含钢率、混凝土抗压强度以及钢材屈服强度对该类型桥墩滞回曲线、刚度退化曲线以及滞回骨架曲线的影响规律。结果表明:薄壁空心钢箱混凝土墩具有良好的抗震性能;轴压比和长细比对薄壁空心钢箱混凝土墩的抗震性能影响较大,建议薄壁空心钢箱混凝土墩轴压比控制在0.5左右,并且在合理范围内尽量减小长细比;截面空心率和截面含钢率对薄壁空心钢箱混凝土墩的抗震性能有一定影响;在一定范围内,增大空心率与含钢率可提高桥墩抗震性能;材料强度等级对薄壁空心钢箱混凝土墩的抗震性能影响相对较小,削弱混凝土强度并增大钢材屈服强度可小幅提高其抗震性能;研究成果对薄壁空心钢箱混凝土墩在工程实践中的应用具有一定的指导意义。     

Langzeitverhalten geklebter Bauteile aus Holz und hochfestem Beton bei natürlichem Klima

Longterm‐behavior of glued full‐scale specimens made from wood and high performance concrete at natural climate conditions The advantages of the construction materials wood and concrete could be used effectively in wood‐concrete‐composite constructions. The composite structure shows optimized load carrying capacity, a better vibrational behavior, higher noise protection and a higher thermally activatable mass in comparison to constructions that are entirely made from wood. Mechanical fasteners or form fitting connections are state‐of‐the‐art for connecting timber to concrete. This leads to more or less flexible bond. By using the adhesive technology a ”rigid bond“ can be achieved and it is possible to combine the advantages of a ”dry construction method“ with the advantages of the prefabrication. The questions of the production technology and the short‐term behavior of glued wood‐concrete composite constructions were answered yet at the department of timber structures at the University of Kassel. Knowledge of long‐term behavior was missing for an application in construction practice. This was studied in the last three years in detail. The experimental und numerical investigations on full‐scale specimens and the conclusions for a practical application are reported in the following article.     

Untersuchungen zur Anwendung von UHPFRC‐Tübbingen bei der zweischaligen Tunnelbauweise

Faserbewehrter Beton wird heute zunehmend auch bei Tunnelbauwerken (Tunnelinnenschalen, Tübbinge) eingesetzt. Wesentliche Vorteile sind das hohe Tragvermögen, das daraus entstehende Einsparungspotential an herkömmlicher stabförmiger Bewehrung (Biegebewehrung, Bügelbewehrung in der Randzone), die Aufnahme von Spaltzugbeanspruchungen durch die Fasern, Rissbreitenbegrenzung, erhöhte Dauerhaftigkeit, verbesserter Brandwiderstand (insbesondere bei Verwendung von Kunststofffasern), Optimierung der Arbeitsabläufe etc. Neue Entwicklungen in der Betontechnologie haben in den letzten Jahrzehnten den faserbewehrten ultrahochfesten Beton (engl. UHPFRC – Ultra High Performance Fibre Reinforced Concrete) hervorgebracht. Im Rahmen dieser Arbeit wird der Einsatz des ultrahochfesten, stahlfaserbewehrten Betons beim zweischaligen Tübbingausbau untersucht. Als Referenzobjekt dient die derzeit im Bau befindliche Tunnelkette Perschling, die im Zuge des viergleisigen Ausbaus der Westbahnstrecke der Österreichischen Bundesbahnen (ÖBB) in Niederösterreich errichtet wird. Ziel der statischen Untersuchung ist es, unter der Randbedingung, dass die maximalen Verformungen des C 40/50‐Normalbetontübbings gemäß Ausschreibungsstatik nicht überschritten werden, herauszufinden, inwieweit die Schalendicke durch Einsatz einer alternativen UHPFRC‐Tübbingschale reduziert und dadurch wirtschaftliche Vorteile generiert werden können. Investigations on the application of Ultra‐High‐Performance‐Fibre‐Reinforced‐Concrete (UHPFRC) tunnel segments at the double shell lining construction. Today fibre reinforced concrete is increasingly applied for tunnel construction (tunnel linings, tunnel segments). The essential benefits are e.g. the higher load bearing capacity, savings potential on the conventional bending and binder reinforcement, the absorption of splitting forces by the fibres, crack width limitation, higher durability, improved fire resistance, optimization of the workflow, etc. Beside the steel fibres carbon or glass fibres and polypropylene fibres are being added increasingly. Recent developments in concrete technology have produced the Ultra‐High‐Performance Fibre‐Reinforced‐Concrete. This work examines the use of UHPFRC at the double shell segmental lining system. As reference object serves the currently constructed tunnel chain Perschling which is part of the four track west railway route extension in Lower Austria. The aim of the analysis is the design of an alternative UHPFRC shell with minimum thickness while maintaining the constraint that the deformations are not exceeding those in the tender design with its C 40/50 reinforced concrete segments.     

Fuß‐ und Radwegbrücke aus Carbonbeton in Albstadt‐Ebingen

Pedestrian bridge made from carbon‐concrete in Albstadt‐Ebingen – First entirely carbon‐reinforced concrete bridge worldwide The bridge erected in Albstadt‐Ebingen in October 2015 is realized without any steel reinforcement or pre‐tensioning, making it the world's first entirely carbon‐reinforced concrete bicycle and pedestrian‐bridge. The trough section with material thicknesses of 70 mm (trough walls) and 90 mm (slab) respectively has been fabricated as monolithic pre‐cast element. With a span length of 15 m and a width of 3 m, the bridge‐deck requires no further coating and has a total weight of just 14 tons (approximately 310 kg/m2); this is about 50 % of comparable conventional reinforced concrete bridge‐decks. Besides material and weight savings, an exceptionally long service life with minimal maintenance can be expected, as the steel corrosion that is typical in reinforced concrete structures can be entirely avoided. Since the use of carbon‐reinforced concrete (carbon concrete) is not yet approved in Germany, the client had to obtain approval based on individual cases (ZiE).