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Shear Resistance (shear + resistance)
Selected AbstractsEngineering Strong Intergraphene Shear Resistance in Multi-walled Carbon Nanotubes and Dramatic Tensile ImprovementsADVANCED MATERIALS, Issue 5 2010Mehdi Estili Strong intergraphene shear resistance is engineered in multi-walled carbon nanotubes (MWCNTs) by embedding the nanotubes into a compressive-stressing ceramic environment to exploit the exceptional strength of its inner graphene walls during tensile loading. A dramatic enhancement in the tensile failure load of MWCNT is achieved in the ceramic environment and a new "multi-wall" failure mechanism is discovered. [source] Querkrafttragfähigkeit von Fahrbahnplatten ohne QuerkraftbewehrungBETON- UND STAHLBETONBAU, Issue 10 2009Günter Rombach Prof. Dr.-Ing. Versuche; Berechnungs- und Bemessungsverfahren Abstract Es wird über Versuche zur Querkrafttragfähigkeit von Brückenfahrbahnplatten aus Stahlbeton berichtet. Diese zeigen, dass die bekannten Rechenansätze für Bauteile ohne Querkraftbewehrung nach DIN 1045-1 bzw. DIN-FB 102 für Fahrbahnplatten auf der sicheren Seite liegen, die tatsächliche Tragfähigkeit aber weit unterschätzt wird. Weitere Ansätze zur Berechnung der Querkrafttragfähigkeit von Stahlbetonbauteilen ohne Querkraftbewehrung werden erörtert. Während die Modelle bei der Auswertung einer Datenbank von Balkenversuchen eine gute Übereinstimmung aufweisen, zeigt der Vergleich mit den Modellversuchen, dass die meisten Rechenverfahren die Tragfähigkeit der Platten unterschätzen. Zur Berechnung der Querkrafttragfähigkeit von Platten ohne Querkraftbewehrung unter Punktlasten wird ein Modell vorgeschlagen, welches die Querkrafttragfähigkeit mit der Zugbeanspruchung der Biegezugzone im kritischen Bereich verknüpft. Shear Resistance of Bridge Decks without Transverse Reinforcement The design of concrete bridge deck slabs is of major concern since the introduction of the Eurocodes as the calculated shear capacity of slabs without stirrups and staggered reinforcement according to the new design standards is often considerably smaller compared to the former regulations i.e. DIN 1045:88. This raises the question whether the existing structures are still save. A series of 12 tests on 4 different specimens representing a bridge deck was performed to examine the real load bearing behaviour of a slab with and without shear reinforcement under a wheel (point) load. The evaluation of the test results revealed, that the current design formula with an assumed elastic shear force distribution leads to rather conservative values of shear capacity for bridge deck slabs. Various approaches for shear design are discussed and the accuracy is checked by means of a shear database and the test results. A new model to calculate the shear capacity is proposed which shows a better agreement with test data than the known approaches. [source] Investigation of the sliding behavior between steel and mortar for seismic applications in structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2009Jason McCormick Abstract The friction developed between a steel base plate and a mortar base contributes shear resistance to the building system during a seismic event. In order to investigate the possible sliding behavior between the base plate and the mortar, a shake table study is undertaken using a large rigid mass supported by steel contact elements which rest on mortar surfaces connected to the shake table. Horizontal input accelerations are considered at various magnitudes and frequencies. The results provide a constant friction coefficient during sliding with an average value of approximately 0.78. A theoretical formulation of the friction behavior is also undertaken. The theoretical equations show that the sliding behavior is dependent on the ratio of the friction force to the input force. The addition of vertical accelerations to the system further complicates the sliding behavior as a result of the varying normal force. This results in a variable friction resistance which is a function of the amplitude, phase, and frequency of the horizontal and vertical input motions. In general, this study showed a consistent and reliable sliding behavior between steel and mortar. Copyright © 2009 John Wiley & Sons, Ltd. [source] Engineering Strong Intergraphene Shear Resistance in Multi-walled Carbon Nanotubes and Dramatic Tensile ImprovementsADVANCED MATERIALS, Issue 5 2010Mehdi Estili Strong intergraphene shear resistance is engineered in multi-walled carbon nanotubes (MWCNTs) by embedding the nanotubes into a compressive-stressing ceramic environment to exploit the exceptional strength of its inner graphene walls during tensile loading. A dramatic enhancement in the tensile failure load of MWCNT is achieved in the ceramic environment and a new "multi-wall" failure mechanism is discovered. [source] Empirical Modeling of Butyl Acrylate/Vinyl Acetate/Acrylic Acid Emulsion-Based Pressure-Sensitive AdhesivesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2004Renata Jovanovic Abstract Summary: Butyl acrylate/vinyl acetate/acrylic acid (BA/VAc/AA) emulsion latexes were produced in a semi-batch mode. The objective was to generate polymers with properties favoring their application as pressure-sensitive adhesives. The influence of the individual monomer concentrations on final properties such as glass transition temperature (Tg), peel strength, shear strength and tack was investigated. To obtain the maximum amount of information in a reasonable number of runs, a constrained three-component mixture design was used to define the experimental conditions. Latexes were coated onto a polyethylene terephthalate carrier and dried. Different empirical models (e.g. linear, quadratic and cubic mixture models) governing the individual properties (i.e. Tg, peel adhesion, shear resistance and tack) were developed and evaluated. In the given experimental region, no single model was found to fit all of the responses (i.e. the final properties). However, in all models the most significant factor affecting the final properties was the AA concentration, followed by the VAc concentration. Shear strength contour lines over the investigated region. [source] Verbundverhalten von vorgespannten Litzen in UHPCBETON- UND STAHLBETONBAU, Issue 6 2010Teil 1: Versuche zur Verbundfestigkeit und zur Übertragungslänge Spannbeton; Versuche; Bewehrung; Baustoffe Abstract Ultra-Hochfester Beton (UHPC = Ultra-High Performance Concrete) ist hervorragend geeignet für vorgespannte Bauteile. Um eine sichere und dennoch wirtschaftliche Bemessung von vorgespannten Trägern mit sofortigem Verbund vornehmen zu können, muss das Verankerungsverhalten der Litzen bekannt sein. Die hohen Verbundfestigkeiten führen zu kurzen Übertragungslängen und verbessern dadurch die Querkrafttragfähigkeit. Bei Vorspannung mit sofortigem Verbund ist eine Mindestbetondeckung entscheidend, um Längsrisse im Verankerungsbereich zu vermeiden, die einen erheblichen Verlust an Verbundfestigkeit und im Extremfall ein Verankerungsversagen zur Folge haben. In diesem Beitrag, der im Rahmen des von der Deutschen Forschungsgemeinschaft geförderten Schwerpunktprogramms SPP 1182 entstand, werden die Untersuchungsergebnisse zum Verbundverhalten von Litzen in UHPC vorgestellt. Teil 1 behandelt die experimentellen Untersuchungen und Teil 2 die Herleitung eines Verbundmodells zur Berechnung der Übertragungslänge. Bond Behavior of prestressed Strands in UHPC. Part 1: Tests on Bond Strength and Transfer Length Ultra-High Performance Concrete (UHPC) is an appropriate construction material for pretensioned girders. To ensure an economic and safe design a detailed knowledge of the behavior of pretensioned strands in the anchorage zone is essential. The dimension of the bond anchorage zone favors the cost-effective design of pretensioned girders, especially when the shear resistance is decisive. However, a minimum concrete cover has to be maintained to avoid splitting cracks in the transmission zone, since they lead to an uncontrolled increase in transfer length and may cause a premature anchorage failure. This paper, which resulted from the priority program SPP 1182 funded by the German Research Foundation, presents the results of investigations on the bond behavior of strands in UHPC. Part 1 deals with the experimental investigations and in part 2 a bond model is derived to design the transfer length. [source] Querkraftbemessung von bügel- oder wendelbewehrten Bauteilen mit KreisquerschnittBETON- UND STAHLBETONBAU, Issue 7 2010Michél Bender Dr.-Ing. Berechnungs- und Bemessungsverfahren; Bewehrung; Versuche Abstract Für bügel- oder wendelbewehrte Stahlbetonbauteile mit Kreisquerschnitt , mit oder ohne zusätzlich drückenden Normalkräften , werden aus dem speziellen inneren Schubfluss die Spannungen in Bügeln und im geneigten Druckfeld abgeleitet und in Widerstandsgleichungen zur Querkraftbemessung umgesetzt. Die Gleichungen besitzen die bekannte Form aus DIN 1045-1 bzw. EC2 und sind erweitert durch einen so genannten Wirksamkeitsfaktor, welcher die Widerstände gegenüber Rechteckquerschnitten auf rund 75% herabsetzt. Alternativ zur bekannten Gleichungsart wird eine additive Widerstandsform aus Betontraganteilen, Fachwerkwirkung und Sprengwerk für die maßgebende Zugstrebentragfähigkeit vorgeschlagen. Eine umfangreiche Versuchsserie verifiziert die Ansätze und zeigt Einzeleffekte von Bügelspannungen, Bewehrungsgrad und Bügelaktivierung sowie Wendel- und Normalkrafteinflüsse. Shear Design of Members with Circular Sections Reinforced by Stirrups or Spirals For RC members with circular sections the stresses within stirrups or spiral reinforcements as well as within the inclined compression field are derived from the specific inner shear flow and elaborated to gain equations for the shear resistances. The equations use the established scheme of DIN 1045-1 or EC 2 extended by an efficiency factor reducing resistances compared to rectangular sections to about 75%. Alternatively, an additive approach for the resistance of the tensile strut is proposed. It sums up from concrete contributions, strut-and-tie actions as well as arch contributions introduced by axial forces. Both approaches are verified to experimental data taken from extensive test series. The characteristics of stirrup stresses and stirrup activation as well as effects from the shear reinforcement ratio, the use of inclined spirals and axial forces are presented. [source] | |||||||||||||