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M Empelmann - One of the best experts on this subject based on the ideXlab platform.
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Druckstrebentragfähigkeit von vorgespannten UHPFRC-Hohlkästen unter Torsion und kombinierter Beanspruchung
Beton- Und Stahlbetonbau, 2014Co-Authors: Vincent Oettel, M EmpelmannAbstract:Aufgrund der hohen Druckfestigkeit von ultrahochfestem Faserbeton (UHPFRC) lassen sich sehr dunnwandige und innovative Bauelemente herstellen. Durch eine Vorfabrikation von transportgerechten und gewichtsoptimierten Segmenten, die spater auf der Baustelle zu komplexen Bauteilen, wie z.B. Segmentbrucken, Fertigteilturmen oder Fertigteilmasten zusammengespannt werden, konnten neue Anwendungsfelder fur Betonbauteile erschlossen werden. Neben der Einwirkung aus Biegung und Querkraft treten in der spateren Nutzung auch Torsionsbeanspruchungen auf. Am iBMB, Fachgebiet Massivbau der TU Braunschweig, wurden experimentelle und theoretische Untersuchungen zur Druckstrebentragfahigkeit von monolithischen und segmentaren extern vorgespannten Balken mit Hohlkastenquerschnitten aus UHPFRC unter Torsion sowie unter kombinierter Biege-, Querkraft- und Torsionsbeanspruchung durchgefuhrt. Auf Basis der Versuchsergebnisse und unter Beachtung der Rechenansatze fur normal- und hochfeste Betone wurden bestehende Bemessungsmodelle zur Beschreibung der Druckstrebentragfahigkeit fur UHPFRC erweitert. Bearing capacity of the Compression Strut of prestressed UHPFRC box girders under torsion and combined loading Due to the high compressive strength of ultra-high performance fiber reinforced concrete (UHPFRC) thin-walled and innovative components can be produced. In order to gain new fields of application for concrete elements it would be useful to prefabricate weight-optimized and transportable segments, which could be mounted to complex components such as segmental bridges, precast towers or precast poles directly on site. As such components are not only stressed by bending and shear, but also torsion, the iBMB, Department of Concrete Structures of the TU Braunschweig, has conducted experimental and theoretical research works on the bearing capacity of the concrete Compression Strut of monolithic and segmental externally prestressed UHPFRC box girders under torsion and combined loading of bending, shear and torsion. Based on the experimental results and the approaches of normal- and high-strength concrete the existing design models have been extended to describe the bearing capacity of UHPFRC Compression Struts.
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druckstrebentragfaehigkeit von vorgespannten uhpfrc hohlkaesten unter torsion und kombinierter beanspruchung bearing capacity of the Compression Strut of prestressed uhpfrc box girders under torsion and combined loading
Beton- Und Stahlbetonbau, 2014Co-Authors: M EmpelmannAbstract:Ultrahochfeste Faserbetone (UHPFRC) lassen sehr duennwandige Bauteile zu, deren Bemessung massgeblich durch die Druckstrebentragfaehigkeit bestimmt wird. Zu diesem Themenkomplex werden die im Rahmen des DFG-Schwerpunktprogramms SPP 1182 durchgefuehrten Untersuchungen und Ergebnisse an monolithischen und segmentaeren Spannbetonbalken mit duennwandigen Hohlkastenquerschnitten aus UHPFRC unter reiner Torsion beziehungsweise kombinierter Querkraft- und Torsionsbeanspruchung vorgestellt. Die Untersuchungen wurden am Institut fuer Baustoffe, Massivbau und Brandschutz (iBMB) des Fachgebiets Massivbau der technischen Universitaet Braunschweig durchgefuehrt. Alle experimentellen Untersuchungen erfolgten an 2,0 Meter langen bewehrten Versuchskoerpern aus UHPFRC mit Wanddicken von 5 Zentimetern im Versagensbereich. Die Einleitung des Torsionsmoments geschah an den beiden Balkenenden. Das Versuchsprogramm erstreckte sich auf zwei monolithische und einen segmentaeren Spannbetonbalken unter reiner Torsion sowie auf je einen monolithischen und segmentaeren Spannbetonbalken unter kombinierter Beanspruchung. Die Versuchskoerper waren so ausgelegt, dass immer das Druckstrebenversagen massgebend wurde. Versuchsaufbau und Versuchsdurchfuehrung werden im Einzelnen beschrieben. Die Versuchsergebnisse zeigen, dass das Versagen, trotz des hohen Stahlfasergehalts, immer ohne Vorankuendigung explosionsartig erfolgte. Die zahlenmaessigen Versuchsergebnisse werden in Tabellen und Diagrammen angegeben und diskutiert. Auf der Grundlage der Versuchsergebnisse und unter Beachtung der Regelungen fuer normal- und hochfesten Beton wurden bestehende Bemessungsmodelle zur Beschreibung der Druckstrebentragfaehigkeit auf UHPFRC erweitert. Dazu wird zunaechst auf die relevanten Regelungen mit Angabe der massgebenden Bemessungsformeln bei reiner Torsionsbeanspruchung und bei kombinierter Torsions- und Querkraftbeanspruchung eingegangen. Es schliesst sich ein Vergleich der Versuchsergebnisse mit den vorhandenen Bemessungsansaetzen an. Dabei wird eingegangen auf den Abminderungswert fuer UHPFRC-Balken, die Interaktion zwischen Torsion und Querkraft sowie auf den Druckstrebenneigungswinkel. Der Vergleich der Traglasten zeigt, dass die Tragfaehigkeit bei einigen Balken bei Ansatz des rechnerischen Druckstrebenwinkels um bis zu 15 Prozent ueberschaetzt wird. Bei unguenstiger Wahl der frei waehlbaren Druckstrebenneigung kann sich somit eine zu hohe Tragfaehigkeit ergeben, sodass die Bemessung auf der unsicheren Seite liegt. Die Festlegung der ansetzbaren Druckstrebenneigung erfordert weitere Untersuchungen. ABSTRACT IN ENGLISH: Due to the high compressive strength of ultra-high performance fiber reinforced concrete (UHPFRC) thin-walled and innovative components can be produced. In order to gain new fields of application for concrete elements it would be useful to prefabricate weight-optimized and transportable segments, which could be mounted to complex components such as segmental bridges, precast towers or precast poles directly on site. As such components are not only stressed by bending and shear, but also torsion, the iBMB, Department of Concrete Structures of the TU Braunschweig, has conducted experimental and theoretical research works on the bearing capacity of the concrete Compression Strut of monolithic and segmental externally prestressed UHPFRC box girders under torsion and combined loading of bending, shear and torsion. Based on the experimental results and the approaches of normal- and high-strength concrete the existing design models have been extended to describe the bearing capacity of UHPFRC Compression Struts. (A)
Vincent Oettel - One of the best experts on this subject based on the ideXlab platform.
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Druckstrebentragfähigkeit von vorgespannten UHPFRC-Hohlkästen unter Torsion und kombinierter Beanspruchung
Beton- Und Stahlbetonbau, 2014Co-Authors: Vincent Oettel, M EmpelmannAbstract:Aufgrund der hohen Druckfestigkeit von ultrahochfestem Faserbeton (UHPFRC) lassen sich sehr dunnwandige und innovative Bauelemente herstellen. Durch eine Vorfabrikation von transportgerechten und gewichtsoptimierten Segmenten, die spater auf der Baustelle zu komplexen Bauteilen, wie z.B. Segmentbrucken, Fertigteilturmen oder Fertigteilmasten zusammengespannt werden, konnten neue Anwendungsfelder fur Betonbauteile erschlossen werden. Neben der Einwirkung aus Biegung und Querkraft treten in der spateren Nutzung auch Torsionsbeanspruchungen auf. Am iBMB, Fachgebiet Massivbau der TU Braunschweig, wurden experimentelle und theoretische Untersuchungen zur Druckstrebentragfahigkeit von monolithischen und segmentaren extern vorgespannten Balken mit Hohlkastenquerschnitten aus UHPFRC unter Torsion sowie unter kombinierter Biege-, Querkraft- und Torsionsbeanspruchung durchgefuhrt. Auf Basis der Versuchsergebnisse und unter Beachtung der Rechenansatze fur normal- und hochfeste Betone wurden bestehende Bemessungsmodelle zur Beschreibung der Druckstrebentragfahigkeit fur UHPFRC erweitert. Bearing capacity of the Compression Strut of prestressed UHPFRC box girders under torsion and combined loading Due to the high compressive strength of ultra-high performance fiber reinforced concrete (UHPFRC) thin-walled and innovative components can be produced. In order to gain new fields of application for concrete elements it would be useful to prefabricate weight-optimized and transportable segments, which could be mounted to complex components such as segmental bridges, precast towers or precast poles directly on site. As such components are not only stressed by bending and shear, but also torsion, the iBMB, Department of Concrete Structures of the TU Braunschweig, has conducted experimental and theoretical research works on the bearing capacity of the concrete Compression Strut of monolithic and segmental externally prestressed UHPFRC box girders under torsion and combined loading of bending, shear and torsion. Based on the experimental results and the approaches of normal- and high-strength concrete the existing design models have been extended to describe the bearing capacity of UHPFRC Compression Struts.
Bing Li - One of the best experts on this subject based on the ideXlab platform.
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Study on Dynamic Shear Resistance of RC Beams
Applied Mechanics and Materials, 2014Co-Authors: Amornthep Somraj, Kazunori Fujikake, Bing LiAbstract:The aim of this study was to investigate the dynamic shear failure behavior of RC beams under rapid loading through an experimental study and also to set up a Strut-and-tie model with loading rate effect to predict the dynamic shear resistance of RC beams. Thus, rapid loading test with 24 RC beams with a shear span-to-deep ratio of 1.9 was performed, in which shear reinforcement ratio and loading rate were variable. All of the RC beams exhibited shear Compression failure. Although the shear resistance increases with increasing loading rate, the influence of loading rate on the shear resistance clearly depends on shear reinforcement ratio. The Strut-and-tie model with loading rate effect was finally developed, in which the thickness of the Compression Strut was formulated to be increased with an increase in loading rate. The developed Strut-and-tie model was good agreement with the experimental results.
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Influence of Loading Rate on Shear Capacity of Reinforced Concrete Beams
International Journal of Protective Structures, 2013Co-Authors: Amornthep Somraj, Kazunori Fujikake, Bing LiAbstract:This study aims to investigate the dynamic shear failure behavior of reinforced concrete (RC) beams under rapid loading through an experimental study and set up a Strut-and-tie model with loading rate effects to predict the dynamic shear capacity of RC beams. Thus, rapid loading test for 48 RC beams was performed, in which shear span-to-depth ratio, shear reinforcement ratio and loading rate were variable. The RC beams exhibited diagonal tension failure, shear Compression failure and flexural failure depending on the shear span-to-depth ratio and the shear reinforcement ratio. The influence of loading rate on the maximum resistance is more significant for the RC beams failed in shear than for those failed in flexure. The Strut-and-tie model with loading rate effects was developed, in which the thickness of the Compression Strut was formulated to be increased with an increase in loading rate. The developed Strut-and-tie model was in good agreement with the experimental results.
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Determination of inclination of Strut and shear strength using variable angle truss model for shear-critical RC beams
Structural Engineering and Mechanics, 2012Co-Authors: Bing Li, Cao Thanh Ngoc TranAbstract:This paper attempts to determine the inclination of t he Compression Strut within variable angle truss models for RC beams loaded in shear-flexure through a pr oposed semi-analytical approach. A truss unit is used to analyze a reinforced concrete beam, by the principle of virtual work under the truss analogy. The inclination of the Compression Strut is then theoretically derived. The concrete contribution is addressed by utilizing the compatibility condition within each truss unit. Comparisons are made between the predicted and published experimental results of the seventy one RC beams with respect to the shear strength and the inclined angle of the Compression Strut at this state to investigate the adequacy of the proposed semi-analytical approach.
Apostolos Psaros-andriopoulos - One of the best experts on this subject based on the ideXlab platform.
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Strength, stiffness and cyclic deformation capacity of RC frames converted into walls by infilling with RC
Bulletin of Earthquake Engineering, 2016Co-Authors: Dionysis Biskinis, Michael N. Fardis, Apostolos Psaros-andriopoulosAbstract:In seismic retrofitting of concrete buildings, frame bays are converted into reinforced concrete (RC) walls by infilling the space between the frame members with RC of a thickness of not more than their width. The cyclic behavior of the resulting wall depends on the connection between the RC infill and the surrounding RC members. The paper uses the results from 56 cyclic tests on such composite walls to express their properties in terms of the geometry, the reinforcement and the connection. Properties addressed are: (a) the yield moment at the story base; (b) the secant-to-yield-point stiffness over the shear span of the wall in a story; (c) the deflection at flexural failure in cyclic loading; (d) the cyclic shear resistance, including a sliding shear failure mode. Separate models are given for squat walls failing in shear and for those where the top of the column shears-off. The proposals are modifications of models developed in the past for monolithic RC walls from several hundred cyclic tests; blind application of these latter models as though the walls were monolithic gives, in general, unsafe predictions. By contrast, the diagonal Compression Strut approach in ASCE41-06 is safe-sided, but gives unacceptably large prediction scatter.
Xue Jianyang - One of the best experts on this subject based on the ideXlab platform.
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Shear capacity of joints between concrete-filled square steel tubular special-shaped columns and steel beams
Journal of Building Structures, 2020Co-Authors: Xue JianyangAbstract:According to the experimental research of the joints between concrete-filled square steel tubular specialshaped columns and steel beams,the factors which influence the failure features of the joints were analyzed. The results indicate that the typical failure mode is shear diagonal Compression in the core of the joint. The shear mechanism is the combination of steel truss mechanism,the main Compression Strut mechanism and the confined Compression Strut mechanism of concrete. Based on the model,the shear capacity of the connection is divided into three parts: the contribution of steel tube webs,the contribution of the main Compression Strut in the concrete core,the contribution of the confined Compression Strut in the concrete core. Based on the analysis of the experimental results, the calculation model of the shear strength of web in panel zone was established. The formula for calculation of the shear capacity of the confined Compression Strut in the concrete core was proposed based on the principle of virtual work. Through regression analysis of the test data,formulas for shear capacity of the main Compression Strut in the concrete core were put forward. The calculation formulas of the yield and ultimate shear capacities of the connection were established. Not only the effect of axial compressive force of column,but also the confinement provided by steel tube for concrete was taken into account in the formulas. The formulas agree well with experiments data.