Nonlinear Behaviour and Design of Steel Built-up Columns under Axial and Transverse Loading

392 σ.Στόχος της παρούσας διδακτορικής διατριβής είναι η μελέτη της συμπεριφοράς σύνθετων υποστυλωμάτων με ράβδους δικτύωσης και τυχαίες συνοριακές συνθήκες υπό αξονική και εγκάρσια φόρτιση και η διατύπωση οδηγιών για το σχεδιασμό τους. Για την επίτευξη αυτού του στόχου ακολουθείται συνδυασμένη πειραματική, αριθμητική και αναλυτική προσέγγιση. Αρχικά, παρουσιάζεται ο σχεδιασμός και η εκτέλεση μιας σειράς πειραματικών δοκιμών με βάση τις οποίες εξάγονται ποιοτικά και ποσοτικά συμπεράσματα. Εν συνεχεία, πραγματοποιούνται αριθμητικές αναλύσεις που δείχνουν πως η αστοχία εκδηλώνεται συνήθως ως τοπική ελαστοπλαστική αστοχία του κρίσιμου φατνώματος. Τέλος, προτείνεται μια αναλυτική μέθοδος για τον προσδιορισμό του φορτίου λυγισμού, της στατικής απόκρισης και του φορτίου αστοχίας ατελών σύνθετων μελών με ράβδους δικτύωσης με τυχαίες συνοριακές συνθήκες υπό αξονικά και εγκάρσια φορτία βασιζόμενη στη θεωρία δοκού Timoshenko. Η προτεινόμενη αναλυτική μέθοδος βρίσκεται σε καλή συμφωνία με αποτελέσματα πλήρως μη γραμμικών αναλύσεων σε αριθμητικά προσομοιώματα μεμονωμένων υποστυλωμάτων και μονώροφων βιομηχανικών πλαισίων.The present doctoral thesis aims at investigating the behaviour of laced built-up beam-columns with arbitrary boundary conditions and providing practical guidance for their design. To that effect, a combined experimental, numerical and analytical approach is adopted. Initially, the design and execution of a series of experimental tests is presented, based on which qualitative and quantitative conclusions are drawn. Afterwards, numerical analyses are used which show that failure usually takes place due to local elastoplastic failure of the critical panel. Finally, an analytical method for the evaluation of the elastic critical buckling load, structural response and collapse load of imperfect laced built-up members under axial and transverse loads based on Timoshenko beam theory is proposed. The proposed analytical method is in good agreement with results obtained with the use of geometrically and materially nonlinear imperfection analyses (GMNIA) in numerical models of both individual laced columns and single-storey industrial frames.Κωνσταντίνος Ε. Καλοχαιρέτη

A proposal for a convertible stadium roof structure derived from Watt-I linkage

In this paper, a novel convertible stadium roof structure is introduced, which has been derived from a special geometric configuration of Watt-I linkage, a 1-DoF mechanism used in robot technologies as anthropomorphic fingers. The proposed structure can offer a wide range of different shape configurations according to the environmental conditions and spatial needs, thus offering several aesthetic and functional advantages over existing solutions. This paper serves as a feasibility investigation of this concept, mainly from geometric and structural point of view. To that affect, first kinematic analysis and geometric design of this linkage are introduced. Then, structural analyses of the proposed structure with realistic dimensions and loading conditions are performed in three different geometric configurations, in order to discuss strength and stiffness limitations. Finally, potential cover materials and actuators are briefly discussed

A novel concept of convertible roofs with high transformability consisting of planar scissor-hinge structures

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Schoolboys reaching for the ball, in the Paddle Shoes commercial, Melbourne, ca. 1965 [picture] /

Title devised by cataloguer from acquisitions documentation.; Part of the collection: Australian life, 1960-1990.; Inscriptions: Signed in ink on verso.; Also available online at: http://nla.gov.au/nla.pic-vn6001103; Purchased 2012

A proposal for a convertible stadium roof structure derived from Watt-I linkage

In this paper, a novel convertible stadium roof structure is introduced, which has been derived from a special geometric configuration of Watt-I linkage, a 1-DoF mechanism used in robot technologies as anthropomorphic fingers. The proposed structure can offer a wide range of different shape configurations according to the environmental conditions and spatial needs, thus offering several aesthetic and functional advantages over existing solutions. This paper serves as a feasibility investigation of this concept, mainly from geometric and structural point of view. To that affect, first kinematic analysis and geometric design of this linkage are introduced. Then, structural analyses of the proposed structure with realistic dimensions and loading conditions are performed in three different geometric configurations, in order to discuss strength and stiffness limitations. Finally, potential cover materials and actuators are briefly discussed