Bolted connections for rectangular hollow sections under tensile loading [online]

SUMMARY The static strength of bolted, spliced connections for rectangular hollow sections under tensile loading is the topic of the presented study. A very common spliced connection type, the bolted flange-plate connection as well as a more recent connection type, the hidden joint connection have been studied. For clarity of presentation, the presented thesis has therefore been divided into two parts: Part I: Bolted flange-plate connections; Part II: Hidden joint connections. Prying forces are the main concern with bolted flange-plate connections. Prying forces occur if the flange-plates lever against each other due to deformations of the plates under tensile loading. Depending on the bolt layout and flange-plate thickness, these prying forces can differ very significantly. Additionally, the formation of a complete yield line mechanism can also result in the collapse of connections with flexible flange-plates and strong bolts. Within the framework of the presented work, an experimental investigation with square and rectangular hollow sections has been carried out. State-of-the-art equipment has been used to record the load in the bolts. The subsequent non-linear Finite Element analyses (using 3D solids as well as contact elements), verified by the results of the experimental investigations, extended the database. A parallel analytical study, inter alia using yield line analysis, served as the basis for the derivation of specific design rules. Part II of the presented thesis deals with so-called hidden joint connections, which are a modification of the more typical gusset plate connection with slotted hollow sections. In contrast to the more common gusset plate connections where the gusset plate protrudes beyond the width of the slotted member, the gusset plate of the hidden joint connection is fitted into the inside width of the unslotted hollow section. The aim of this research has been the derivation of a design model for shear lag failure, in particular the rupture of the hollow section due to shear lag. A limited number of tensile tests on hidden joint connections for square hollow sections has been carried out. Technical feasibility of welding inside the hollow section has been of special interest. The tests have been used to verify the numerical investigation, which again has been used as a basis for a new calculation method for shear lag failure of the hollow section. KURZFASSUNG Die vorliegende Arbeit beschäftigt sich mit der statischen Tragfähigkeit von geschraubten Stoßverbindungen für rechteckige Hohlprofile unter Zugbelastung. Eine weit verbreitete Stoßverbindung, die geschraubte Kopfplattenverbindung, sowie auch eine eher neuere Verbindung, der verdeckte Knoten, sind untersucht worden. Die vorliegende Arbeit wurde zur besseren Übersicht deshalb in zwei Abschnitte geteilt: Teil I: Geschraubte Kopfplattenverbindungen; Teil II: Verdeckte Knotenverbindungen. Das Hauptproblem bei der Verwendung von Kopfplattenverbindungen besteht in den Abstützkräften. Diese Zusatzkräfte entstehen, wenn sich die Kopfplatten aufgrund der Verfor-mungen unter Zugbelastung gegenseitig abstützen. Die Abstützkräfte können in Abhängigkeit von der Schraubenverteilung und Kopfplattendicke stark variieren. Andererseits kann die Bil-dung eines kompletten Fließlinienmechanismus für Verbindungen mit flexiblen Kopfplatten und sehr festen Schrauben auch zu einem Versagen führen. Im Rahmen der vorliegenden Arbeit ist eine experimentelle Untersuchung mit quadratischen und rechteckigen Hohlprofilen durchge-führt worden. Modernste Ausrüstung wurde zur Messung der Kräfte in den Schrauben ver-wandt. Die nachfolgenden nichtlinearen finiten Elementuntersuchungen (mit 3D Volumen- sowie Kontaktelementen) wurden mit den Ergebnissen der experimentellen Studie verifiziert und dienten der Erweiterung der Datenmenge. Eine parallel durchgeführte analytische Studie, die unter anderem Fließlinientheorie verwendet, diente als Basis zur Herleitung spezieller Bemessungsregeln. Teil II der vorliegenden Arbeit behandelt sogenannte verdeckte Knoten, welche eine Abwandlung der gängigeren Knotenblechverbindungen mit geschlitzten Hohlprofilen darstellen. Im Gegensatz zu der verbreiteteren Knotenblechverbindung, bei der das Knotenblech über die Breite des Hohlprofils hinausragt, wird das Knotenblech bei verdeckten Knoten in die Innenseite des ungeschlitzten Hohlprofils eingepaßt. Ziel der Forschung war die Herleitung eines Bemessungsmodells gegen ein Versagen durch die örtlich begrenzte Lasteinleitung, insbesondere eines plötzlichen Risses des Hohlprofils durch die lokalen Spannungsspitzen. Eine begrenzte Anzahl von Zugversuchen an verdeckten Knoten für Quadrathohlprofile ist durchgeführt worden. Die technische Umsetzung der Schweißarbeiten im Innern des Hohl-profils war von speziellem Interesse. Die Versuche wurden zur Verifizierung einer numerischen Untersuchung verwendet, welche wiederum als Basis für neue Bemessungs-formeln gegen ein Versagen des Hohlprofils durch örtlich begrenzte Lasteinleitung diente

Investigation of the Phosphorylation of theC-terminal domains of the cardiac MyosinBinding Protein C by the 5-AMP-activatedProtein Kinase

The existence of MyBP-C in striated muscle has been known for over 35 years and about 150 mutations in the gene encoding cMyBP-C have been found to be a common cause of hypertrophic cardiomyopathy. Despite this, the structure and function of MyBP-C remains less well understood than most other sarcomeric proteins, with roles in both regulation of contraction and thick filament formation/stability being proposed. In addition to the well known interactions of MyBP-C with other proteins of the sarcomeric apparatus (LMM, titin, actin) and with PKA, CaMKK and PKC at the N-terminal end of the protein, the aim of this study was to investigate interactions of MyBP-Cs C-terminus with the 5-AMP-activated protein kinase. This enzyme came in the focus of research during the last decade as it appears to function in a plethora of cell processes. Further, it has been elucidated that mutations in PRKAG2, encoding for the γ2 subunit of AMPK, causes left ventricular hypertrophy associated with conduction system diseases (e.g. Wolf-Parkinson-White syndrome). Important questions that have to be answered for a better understanding of this issue are, beside others, the identification of the full repertoire of cardiac protein targets. My project aimed at identifying the site or sites of AMPK phosphorylation within the C-terminal three domains of cMyBP-C as suggested by earlier yeast-two-hybridscreen data and biochemical work. The latter hinted that the C8 domain was most likely the target, and it is this fragment that my work began with. Having optimised the expression and purification of recombinant wild type MyBP-C C8 domain and a number of mutated C8 domains as discussed in Chapter 3, it was possible to disprove the hypothesis of phosphorylatable residues being in this domain. In contrast, it was revealed that a phosphorylatable serine moiety was present in the N-terminal leader of the recombinant protein, encoded by the vector pET-28a. This serine lies in the thrombin recognition sequence itself and its phosphorylation inhibits cleavage. However, it was shown in vitro that a phosphorylatable serine residue is located in the C10 domain of the protein and this further confirms the association of the C8-C10 fragment of MyBP-C with AMPK, first observed in the yeast two-hybrid assay. The hypotheses that arise from these results will be discussed in this chapter. Additionally, I showed that the N-terminal domains of cMyBP-C (C0-C2), which contain the well characterized PKA and CaMII sites, are not a good substrate for AMPK in vitro

The Application of Signature Character Strengths and Positive Experiences at Work

We hypothesized that the amount of positive experiences at work (job satisfaction, pleasure, engagement, meaning) is a function of the extent to which the situational circumstances at the workplace allow for the application of an individual's signature character strengths. For the description of the individual a reliable and valid instrument already exists, but not for the environment. Hence, the newly developed Applicability of Character Strengths Rating Scales (ACS-RS) with information on its reliability and validity were also presented. A sample of 1,111 adults filled in the ACS-RS and measures for possession of character strengths and positive experiences at work. The ACS-RS was reliable by means of internal consistency and inter-rater reliability. It proved to be valid in several ways being sensitive to: (a) the differences in the applicability of trait-relevant behavior in formal versus informal situations by showing higher applicability of the character strengths in the latter; (b) the differences between traits regarding their applicability across situations; (c) people's disposition to choose situations fitting their dispositions by showing positive relationships between the degree of possession and applicability. Moreover, correlations between applicability of strengths and positive experiences increased with the individual centrality of the strengths. The more signature strengths were applied at the workplace, the higher the positive experiences at work. This study showed that character strengths matter in vocational environments irrespective of their content. Strengths-congruent activities at the workplace are important for positive experiences at work like job satisfaction and experiencing pleasure, engagement, and meaning fostered by one's jo