Investigation of Stress Transfer Behavior in Textile Reinforced Concrete with Application to Reinforcement Overlapping and Development Lengths

Die kontinuumsmechanische Untersuchung der Lastübertragungsmechanismen zwischen den Rovings im textilbewehrten Feinbeton trägt wesentlich zum Gesamtverständnis des mechanischen Verhaltens des Verbundmaterials bei. Neben der Erfassung der gegenseitigen Beeinflussung sich kreuzender Rovings erfordert insbesondere die mechanische Modellierung und numerische Simulation von Bewehrungsstößen und Endverankerungen die Kenntnis dieser Übertragungsmechanismen. Die numerischen Simulationen sollen u. a. zeigen, welche Endverankerungslängen und welche Übergreifungslängen an Bewehrungsstößen erforderlich sind und wie die Querbewehrung die Rissbildung beeinflusst.This paper concerns with the investigation of stress transfer mechanisms between yarns and concrete matrix and their influence on the overall behavior of textile reinforced concrete (TRC). This investigation considers textile reinforcement splices and textile reinforcement development lengths and carried out by means of Finite-Element simulations and fracture mechanic approaches. A first modeling procedure is made towards analyzing and investigating the damage mechanisms in TRC specimen under tension loading which are mainly characterized by matrix cracking and yarn pullout. This modeling approach allows for considering the yarn crack bridging which is a main characteristic behavior of TRC. In the same manner, 3D Finite-Element models are conducted for calculating the required reinforcement development lengths and the reinforcement overlapping lengths. The conducted approach takes into account different damage mechanisms observed in the corresponding experimental investigations which are also used for calibrating the modeling procedures. Moreover, the presented approach covers a wide range of required textile reinforcement overlapping lengths and development lengths and provides the corresponding ultimate loads

Entwicklung mechanischer Modelle zur analytischen Beschreibung der Materialeigenschaften von textilbewehrtem Feinbeton

The aim of this work is the development of mechanical models on a mesoscopic level for the analytical description of the material properties of textile reinforced concrete (TRC). For the modelling of the heterogeneous structure of TRC the concept of representative volume elements (RVE) is used. RVEs are representative for the mesoscopic structure. The overall material behaviour on the macroscopic level is obtained by means of homogenisation of the heterogeneous material behaviour on the mesoscopic level. Based on the micro mechanical solution of the elastic field of an ellipsoidal inclusion according to Eshelby a model for the determination of the material behaviour for multi-directional reinforced finegrained concrete is developed. An effective field approximation considers the interaction of the differentially orientated reinforcements in an averaged sense. Microcracks are included by additional strains in the representative volume element. The average interaction between the microcracks and the reinforcements is considered by an effective field approximation. As a criteria for the initiation of the macro cracking a critical microcrack density parameter is implemented in the mechanical model. The microcracks accumulate to macrocracks if the microcrack density parameter in the RVE exceeds this critical value. For the mechanical modelling of the bond behaviour between roving and matrix after macro cracking a multiple linear shear stress-slip relation is used. This shear stress-slip relation considers adhesion, damage and failure of the interface between roving and matrix. Hence experimentally measured pullout force-displacement curves can be simulated realistically.Gegenstand dieser Arbeit ist die Entwicklung mechanischer Modelle auf der Mesoebene zur analytischen Beschreibung des makroskopischen Materialverhaltens von textilbewehrtem Feinbeton. Für die Modellierung der heterogenen Struktur wird das Konzept der repräsentativen Volumenelemente (RVE), die für die Mesostruktur des betrachteten Verbundwerkstoffes repräsentativ sind, verwendet. Der Übergang von dem heterogenen Materialverhalten auf der Mesoebene zum mittleren Materialverhalten auf der Makroebene erfolgt mittels Homogenisierung. Auf Basis der mikromechanischen Grundlösung für ellipsoidförmige Einschlüsse nach Eshelby wird ein Modell entwickelt, das die Ermittlung des Materialverhaltens von multidirektional bewehrtem Feinbeton ermöglicht. Durch die Anwendung einer Effektive-Feld-Theorie wird die gegenseitige Beeinflussung der unterschiedlich orientierten Bewehrungen in einem gemittelten Sinn betrachtet. Die ab einer bestimmten makroskopischen Beanspruchung entstehenden Mikrorisse berücksichtigt das mechanische Modell über einen durch die Mikrorisse hervorgerufenen zusätzlichen Verzerrungsanteil im RVE. Mittels der verwendeten Effektive-Feld-Theorie kann eine mittlere Beeinflussung zwischen den Mikrorissen und der Rovingbewehrung erfasst werden. Für den Übergang von der Mikrorissbildung zur Makrorissbildung wird für das mechanische Modell der Begriff einer maximalen Mikrorissdichte eingeführt. Überschreitet die Mikrorissdichte im RVE diesen maximalen Wert, vereinigen sich die Mikrorisse zu Makrorissen. Zur Beschreibung des mechanischen Verbundverhaltens zwischen Roving und Matrix beim Rovingauszug am Makroriss wird eine multilineare Schubspannungs-Schlupf-Beziehung verwendet, welche die Schädigung des Roving-Matrix-Verbundes bis hin zum vollständigen Versagen erfasst. Damit lassen sich experimentell ermittelte Kraft-Verformungskurven an Zugproben wirklichkeitsnah abbilden

Unique nesting biology of Osmia ( Melanosmia) uncinata, a Palaearctic osmiine bee specialized on thick-barked conifers (Hymenoptera, Megachilidae)

Osmia (Melanosmia) uncinata Gerstäcker is a Palaearctic megachilid bee distributed from temperate and northern Europe eastwards to the Russian Far East. The discovery of over 80 nests in Switzerland, southern Germany and Scotland enabled for the first time a closer investigation of its nesting biology and prompted the assessment of the species’ phenology, distribution and habitat. O. uncinata nested in self-excavated burrows inside the bark of both living trunks and dead stumps of Pinus sylvestris. The nests were excavated at a height of 10–220 cm above ground either on the underside of prominences of longitudinal bark ribs or inside beetle borings and extended more or less vertically upwards. They consisted of a single straight to slightly curved burrow with rarely one to three side burrows, had a total length of 1.2–12.0 cm and contained 1–6 brood cells. The brood cells, which faced downwards with the larval provisions being located in the upper cell half, were separated from each other by one-layered walls of chewed leaves (“leaf pulp”). The nests were sealed with a plug of 2–4 closely adjacent walls of leaf pulp. DNA metabarcoding of cell and plug walls revealed that Potentilla and Fragaria (Rosaceae) served as leaf pulp sources. Pre-imaginal mortality amounted to 77%, partly caused by brood parasites such as Sapyga similis (Sapygidae) and Cacoxenus indagator (Drosophilidae) or predators such as snakeflies (Raphidioptera). At low elevations, O. uncinata needs one year for its development and overwinters as imago inside the nest, whereas in the subalpine zone of the Alps it has a two-year cycle passing the first winter as prepupa and the second winter as imago. O. uncinata starts to emerge between the end of March at low elevations and the end of May at higher elevations qualifying as an early flying bee like the other European O. (Melanosmia) species. The distribution of O. uncinata in Central Europe and Scotland largely coincides with the occurrence of P. sylvestris. As in the pine, it extends over a wide altitudinal range from below 100 m up to 1900 m a.s.l. and encompasses dry and wet as well as warm and cold habitats including open pine forests, inner and outer forest edges dominated by pine and isolated pine groups. At a few locations in the subalpine zone of the Alps, O. uncinata occurs in the absence of P. sylvestris; here, the thick bark of Larix decidua serves as a substitute nesting substrate

Numerische Simulation des mechanischen Verhaltens von Textilbeton unter Berücksichtigung mehrerer Strukturebenen

The failure mechanisms of textile reinforced concrete (TRC), which is a composite of bundles of long fibers and fine concrete, are complex. Most important for the ductility is the successive debonding of the fibers from the surrounding matrix when the brittle matrix is cracking. Therefore, one of the main issues is the simulation of the bond behavior between the reinforcement and the matrix. By introducing a hierarchical material model for TRC the mechanical behavior is simulated by means of representative volume elements modelled on the meso scale. Finite element analysis is used to determine the effective properties of TRC within a periodic homogenization framework. Further, a multiscale finite element technique is suggested, where constitutive equation are formulated only on the meso level

Öko-Buchführungsergebnisse - Auswertung der Buchführungsergebnisse ökologisch wirtschaftender Betriebe im Wirtschaftsjahr 2005/2006

In Fortführung des im Jahr 2003 ins Leben gerufenen Gemeinschaftsprojektes der ostdeutschen Bundesländer zur Auswertung der Buchführungsergebnisse ökologisch wirtschaftender Betriebe liegen nunmehr die Ergebnisse des Wirtschaftsjahres 2005/06 vor. Hintergrund dieser länderübergreifenden Analyse ist die unzureichende Anzahl auswertbarer BMELV-Jahresabschlüsse in den einzelnen Bundesländern. Die Zusammenführung der zur Verfügung stehenden Datensätze zu einer Gesamtstichprobe gestattet demgegenüber die Ableitung allgemeingültiger Aussagen zur Situation und Entwicklung der Öko-Betriebe. Darüber hinaus wird die Wirtschaftskraft der Betriebe insgesamt sowie einzelner Rechts- und Betriebsformen auch im Vergleich zu Betrieben mit konventioneller Bewirtschaftung dargestellt und beurteilt

The Grizzly, April 6, 1984

Loyalty Fund Phon-a-thon, Successful • Parsons Re-elected VP of Historical Society • Nagy\u27s Stellar Lecture • McQuaid Presents Views on Candidates • Letters to the Editor: Fraternities Help to Combat Apathy; Bubble World ; UC Social Life Needs Help; Pledging Not Destructive; Pledging Enhances Development; To Ban Pledging not a Positive Aspect; In Memory of Zeta Chi; Pledging to Expand Socially • Patrol Pattern Changed, Woman is Assaulted • The Limerick Syndrome: What Would UC do? • Mardi Gras Ball Declared Success • Changing Picture of Health in \u2780\u27s • Ride for Your Life! • Two Views on the Bussing Situation • Women\u27s Tennis Splits in Opening Matches • Softball Undefeated at 6-0 • Tennis Team Nets Two Victories • Denning Captures Fencing Title • Strizke, Rosenberg Qualify for Gymnastics Championship • Men\u27s Track Kicks off \u2784 Season • Men\u27s Lacrosse Thumps Bloomsburg • Hot Hitting Leads Bears Batsmen to Victories • Baseball Team Raises Record to 6-3 • Women\u27s Track Promisinghttps://digitalcommons.ursinus.edu/grizzlynews/1116/thumbnail.jp

Prevalence of oral and oropharyngeal human papillomavirus in a sample of South African men: A pilot study

Background. Human papillomavirus (HPV) infection is well known to be associated with head and neck cancers (HNCs). HPV-associated HNCs are related to sexual behaviour, particularly the lifetime number of oral sex partners, but the epidemiology of oral and oropharyngeal HPV in South African men has not yet been studied.Objectives. To determine the oral and oropharyngeal HPV strain prevalence and associated factors in a selected male population in Pretoria, South Africa (SA).Methods. Male factory workers were recruited. Oral rinse and gargle samples were tested for 37 HPV types using the Linear Array HPV Genotyping Test (Roche Molecular Systems). A questionnaire was used to obtain information regarding age, medical conditions, substance and alcohol use and sexual behaviour. HIV testing was optional.Results. The HPV prevalence was 5.6% among men (N=125) aged 17 - 64 years. High-risk HPV (hrHPV) types 16 and 68 were found in two men. Oral sex seemed to be an uncommon practice in the majority of respondents, but the two respondents with hrHPV did practise oral sex. There was a statistically significant association between HPV infection and an increased number of sexual partners (p=0.027), but not between HPV and substance use, HIV status or clinical mucosal pathology.Conclusion. The prevalence of oral and oropharyngeal HPV was lower than reported in other countries. An association between oral HPV and having multiple sexual partners was found. A larger nationwide study would give a more representative view of the burden of oral and oropharyngeal HPV infection in SA

“A very orderly retreat”: Democratic transition in East Germany, 1989-90

East Germany's 1989-90 democratisation is among the best known of East European transitions, but does not lend itself to comparative analysis, due to the singular way in which political reform and democratic consolidation were subsumed by Germany's unification process. Yet aspects of East Germany's democratisation have proved amenable to comparative approaches. This article reviews the comparative literature that refers to East Germany, and finds a schism between those who designate East Germany's transition “regime collapse” and others who contend that it exemplifies “transition through extrication”. It inquires into the merits of each position and finds in favour of the latter. Drawing on primary and secondary literature, as well as archival and interview sources, it portrays a communist elite that was, to a large extent, prepared to adapt to changing circumstances and capable of learning from “reference states” such as Poland. Although East Germany was the Soviet state in which the positions of existing elites were most threatened by democratic transition, here too a surprising number succeeded in maintaining their position while filing across the bridge to market society. A concluding section outlines the alchemy through which their bureaucratic power was transmuted into property and influence in the “new Germany”

The VMC survey - XVII : The proper motions of the Small Magellanic Cloud and the Milky Way globular cluster 47 Tucanae

In this study we use multi-epoch near-infrared observations from the VISTA survey of the Magellanic Cloud system (VMC) to measure the proper motion of different stellar populations in a tile of 1.5 deg sq. in size in the direction of the Galactic globular cluster 47 Tuc. We obtain the proper motion of the cluster itself, of the Small Magellanic Cloud (SMC), and of the field Milky Way stars. Stars of the three main stellar components are selected from their spatial distribution and their distribution in colour-magnitude diagrams. Their average coordinate displacement is computed from the difference between multiple Ks-band observations for stars as faint as Ks=19 mag. Proper motions are derived from the slope of the best-fitting line among 10 VMC epochs over a time baseline of ~1 yr. Background galaxies are used to calibrate the absolute astrometric reference frame. The resulting absolute proper motion of 47 Tuc is (mu_alpha cos(delta), mu_delta)=(+7.26+/-0.03, -1.25+/-0.03) mas/yr. This measurement refers to about 35000 sources distributed between 10 and 60 arcmin from the cluster centre. For the SMC we obtain (mu_alpha cos(delta), mu_delta)=(+1.16+/-0.07, -0.81+/-0.07) mas/yr from about 5250 red clump and red giant branch stars. The absolute proper motion of the Milky Way population in the line-of-sight (l =305.9, b =-44.9) of this VISTA tile is (mu_alpha cos(delta), mu_delta)=(+10.22+/-0.14, -1.27+/-0.12) mas/yr and results from about 4000 sources. Systematic uncertainties associated to the astrometric reference system are 0.18 mas/yr. Thanks to the proper motion we detect 47 Tuc stars beyond its tidal radius.Peer reviewe

Prevalence of oral and oropharyngeal human papillomavirus in a sample of South African men : a pilot study

BACKGROUND. Human papillomavirus (HPV) infection is well known to be associated with head and neck cancers (HNCs). HPV-associated HNCs are related to sexual behaviour, particularly the lifetime number of oral sex partners, but the epidemiology of oral and oropharyngeal HPV in South African men has not yet been studied. Objectives. To determine the oral and oropharyngeal HPV strain prevalence and associated factors in a selected male population in Pretoria, South Africa (SA). METHODS. Male factory workers were recruited. Oral rinse and gargle samples were tested for 37 HPV types using the Linear Array HPV Genotyping Test (Roche Molecular Systems). A questionnaire was used to obtain information regarding age, medical conditions, substance and alcohol use and sexual behaviour. HIV testing was optional. RESULTS. The HPV prevalence was 5.6% among men (N=125) aged 17 - 64 years. High-risk HPV (hrHPV) types 16 and 68 were found in two men. Oral sex seemed to be an uncommon practice in the majority of respondents, but the two respondents with hrHPV did practise oral sex. There was a statistically significant association between HPV infection and an increased number of sexual partners (p=0.027), but not between HPV and substance use, HIV status or clinical mucosal pathology. CONCLUSION. The prevalence of oral and oropharyngeal HPV was lower than reported in other countries. An association between oral HPV and having multiple sexual partners was found. A larger nationwide study would give a more representative view of the burden of oral and oropharyngeal HPV infection in SA.The Dental Research Education and Development Trust of the South African Dental Associationhttp://www.samj.org.zaam201