Master of Science / Department of Civil Engineering / Asadollah Esmaeily / The shear and combined shear and torsion provisions of the AASHTO LRFD (2008) Bridge Design Specifications, as well as simplified AASHTO procedure for prestressed and non-prestressed reinforced concrete members were investigated and compared to their equivalent ACI 318-08 provisions. Response-2000, an analytical tool developed based on the Modified Compression Field Theory (MCFT), was first validated against the existing experimental data and then used to generate the required data for cases where no experimental data was available. Several normal and prestressed beams, either simply supported or continuous were used to evaluate the AASHTO and ACI shear design provisions In addition, the AASHTO LRFD provisions for combined shear and torsion were investigated and their accuracy was validated against the available experimental data. These provisions were also compared to their equivalent ACI code requirements. The latest design procedures in both codes propose exact shear-torsion interaction equations that can directly be compared to the experimental results by considering all ϕ factors as one. In this comprehensive study, different over-reinforced, moderately-reinforced, and under-reinforced sections with high-strength and normal-strength concrete for both solid and hollow sections were analyzed. The main objectives of this study were to: • Evaluate the shear and the shear-torsion procedures proposed by AASHTO LRFD (2008) and ACI 318-08 • Validate the code procedures against the experimental results by mapping the experimental points on the code-based exact interaction diagrams • Develop a MathCAD program as a design tool for sections subjected to shear or combined shear and torsion

The purpose of this research is to examine the behaviour of elliptical concrete-filled steel tubular stub columns under a combination of axial force and bending moment. Most of the research carried out to date involving concrete-filled steel sections has focussed on circular and rectangular tubes, with each shape exhibiting distinct behaviour. The degree of concrete confinement provided by the hollow section wall has been studied under pure compression but remains ambiguous for combined compressive and bending loads, with no current design provision for this loading combination. To explore the structural behaviour, laboratory tests were carried out using eight stub columns of two different tube wall thicknesses and applying axial compression under various eccentricities. Moment-rotation relationships were produced for each specimen to establish the influence of cross-section dimension and axis of bending on overall response. Full 3D finite element models were developed, comparing the effect of different material constitutive models, until good agreement was found. Finally, analytical interaction curves were generated assuming plastic behaviour and compared with the experimental and finite element results. Ground work provided from these tests paves the way for the development of future design guidelines on the member level.

Limitações de altura são frequentemente impostas à edificações de múltiplos pavimentos por regulamentos de zoneamento urbano, aspectos econômicos e considerações estéticas. Um pé-direito alto é normalmente requerido para se permitir a passagem de tubulações e dutos de grande diâmetro sob vigas de aço, conduzindo muitas vezes à alturas inaceitáveis entre pavimentos de edificações. Várias são as soluções possíveis para se resolver tal inconveniência, dentre elas pode-se citar: Vigas com inércia variável, stub girders , treliças mistas e vigas misuladas. Outra solução frequentemente utilizada é a abertura de furos na alma das vigas d e aço para a passagem das tubulações de serviço. A presente dissertação tem por objetivo avaliar e descrever o comportamento estrutural de vigas de aço com aberturas de diferentes tamanhos e formas na alma. Outro propósito deste trabalho de pesquisa é a avaliação dos parâmetros que influenciam diretamente a capacidade de resistência das vigas com diferentes tipos de abertura na alma, tais como: Tipo de furo, localização do furo ao longo do vão, altura do furo em relação à altura do perfil, esbeltez da alma, localização da carga solicitante ao longo do vão, entre outros. Também é objetivo deste trabalho, a avaliação dos diferentes mecanismos de ruína para as vigas com aberturas na alma e as causas que conduziram o colapso das mesmas. Finalmente, apresenta-se um estudo da eficácia de enrijecedores longitudinais nos locais de abertura da alma das vigas de aço. A metodologia empregada para tal estudo baseou-se em uma análise paramétrica com o auxílio do método numérico dos elementos finitos. / Height limitations are frequent in multi-storey buildings due to zoning regulations, economic requirements and esthetical considerations . In order to provide the passage of large pipes and ducts beneath steel beams, huge spaces are normally required, leading many times to unacceptable heights between storeys. There are many possible solutions to solve these problems, such as: Tapered beams, stub girders, composite trusses and haunched beams. Another frequent solution is the opening of holes in the web beam steel to enable the passage of the services. This dissertation has the objective of evaluating and describing the structural behavior of steel beams with web openings of different shapes and sizes. Another aim of this research work is the evaluation of the parameters that directly influence the load carry capacity of the beams with different web openings, such as: Holesh ape, the location of the opening throughout the span, the height hole to height profile ratio, the web slenderness and the location of the load point throughout the span. The evaluation of the different failure mechanisms of steel beams with web openings and the reasons that conducted the collapse of them are also focused on the present work. Finally, a study of the efficiency of the use of longitudinal stiffeners at web openings locations is also presented. The methodology employed for such study was based on a parametric analysis based on the finite elements method.

Limitações de altura são frequentemente impostas à edificações de múltiplos pavimentos por regulamentos de zoneamento urbano, aspectos econômicos e considerações estéticas. Um pé-direito alto é normalmente requerido para se permitir a passagem de tubulações e dutos de grande diâmetro sob vigas de aço, conduzindo muitas vezes à alturas inaceitáveis entre pavimentos de edificações. Várias são as soluções possíveis para se resolver tal inconveniência, dentre elas pode-se citar: Vigas com inércia variável, stub girders , treliças mistas e vigas misuladas. Outra solução frequentemente utilizada é a abertura de furos na alma das vigas d e aço para a passagem das tubulações de serviço. A presente dissertação tem por objetivo avaliar e descrever o comportamento estrutural de vigas de aço com aberturas de diferentes tamanhos e formas na alma. Outro propósito deste trabalho de pesquisa é a avaliação dos parâmetros que influenciam diretamente a capacidade de resistência das vigas com diferentes tipos de abertura na alma, tais como: Tipo de furo, localização do furo ao longo do vão, altura do furo em relação à altura do perfil, esbeltez da alma, localização da carga solicitante ao longo do vão, entre outros. Também é objetivo deste trabalho, a avaliação dos diferentes mecanismos de ruína para as vigas com aberturas na alma e as causas que conduziram o colapso das mesmas. Finalmente, apresenta-se um estudo da eficácia de enrijecedores longitudinais nos locais de abertura da alma das vigas de aço. A metodologia empregada para tal estudo baseou-se em uma análise paramétrica com o auxílio do método numérico dos elementos finitos. / Height limitations are frequent in multi-storey buildings due to zoning regulations, economic requirements and esthetical considerations . In order to provide the passage of large pipes and ducts beneath steel beams, huge spaces are normally required, leading many times to unacceptable heights between storeys. There are many possible solutions to solve these problems, such as: Tapered beams, stub girders, composite trusses and haunched beams. Another frequent solution is the opening of holes in the web beam steel to enable the passage of the services. This dissertation has the objective of evaluating and describing the structural behavior of steel beams with web openings of different shapes and sizes. Another aim of this research work is the evaluation of the parameters that directly influence the load carry capacity of the beams with different web openings, such as: Holesh ape, the location of the opening throughout the span, the height hole to height profile ratio, the web slenderness and the location of the load point throughout the span. The evaluation of the different failure mechanisms of steel beams with web openings and the reasons that conducted the collapse of them are also focused on the present work. Finally, a study of the efficiency of the use of longitudinal stiffeners at web openings locations is also presented. The methodology employed for such study was based on a parametric analysis based on the finite elements method.

Στην παρούσα διδακτορική διατριβή αναπτύσσεται μια νέα τεχνική ενίσχυσης υποστυλωμάτων οπλισμένου σκυροδέματος με βάση τη χρήση συνθέτων υλικών, τα οποία αποτελούνται από πλέγματα ινών σε ανόργανη μήτρα (π.χ. κονίαµα µε βάση το τσιμέντο), αποσκοπώντας στην επίλυση προβλημάτων που χαρακτηρίζουν τα Ινοπλισμένα Πολυμερή (ΙΟΠ) σχετικά µε τη χρήση εποξειδικών ρητινών. Τα Ινοπλέγματα σε Ανόργανη Μήτρα (ΙΑΜ) δοκιμάζονται στη μορφή μανδύα µε στόχο την περίσφιγξη και την αύξηση της πλαστιμότητας υποστυλωμάτων παλαιού τύπου, σχεδιασμένων δηλαδή χωρίς τις νέες αντισεισμικές λεπτομέρειες όπλισης. Εξετάζονται διάφορες παράμετροι, που περιλαμβάνουν τη χρήση ράβδων λείων ή με νευρώσεις, την πιθανή ένωση των ράβδων με υπερκάλυψη στον πόδα των υποστυλωμάτων και το μήκος υπερκάλυψης. Έτσι προσδιορίζεται η αποτελεσματικότητα των μανδυών ΙΑΜ και συγκρίνεται με αυτή τον ΙΟΠ ως μέσου περίσφιγξης στις κρίσιμες περιοχές υφισταμένων υποστυλωμάτων για όλες τις περιπτώσεις καμπτικών αστοχιών στην περιοχή της πλαστικής άρθρωσης. Το πειραματικό πρόγραμμα που ακολουθείται για την απόκτηση δεδομένων γύρω από τη συμπεριφορά υποστυλωμάτων οπλισμένου σκυροδέματος, ενισχυμένων με μανδύες ανόργανης (ΙΑΜ) ή οργανικής (ΙΟΠ) μήτρας, περιλαμβάνει συνολικά 28 δοκιμές επί δοκιμίων υποστυλωμάτων δύο τύπων: (α) 15 πρισματικά δοκίμια οπλισμένου σκυροδέματος που δοκιμάζονται σε κεντρική θλίψη και (β) 13 δοκίμια υποστυλωμάτων πλήρους κλίμακας, τα οποία δοκιμάζονται σε ανακυκλιζόμενη κάμψη με σταθερό αξονικό φορτίο. Καταδεικνύεται ότι η αποτελεσµατικότητα των µανδυών ΙΑΜ είναι υψηλή και γενικώς παρόµοια µε αυτή των µανδυών ΙΟΠ για όλες τις περιπτώσεις που εξετάστηκαν. Επιπροσθέτως, τα πειραματικά αποτελέσματα των 13 υποστυλωμάτων πλήρους κλίμακας που υποβλήθηκαν σε ανακυκλιζόμενη κάμψη (με σταθερό αξονικό φορτίο), συμβάλλουν στη διερεύνηση δύο ακόμα “θολών” μέχρι σήμερα πεδίων, όπως: (α) Ο λυγισμός των διαμήκων ράβδων σε περισφιγμένο με μανδύες ΙΑΜ ή ΙΟΠ σκυρόδεμα. Ιδιαίτερη έμφαση δίνεται στη μελέτη της αλληλεπίδρασης μεταξύ του μανδύα ΙΑΜ ή ΙΟΠ και των διαμήκων ράβδων, κατά την έναρξη και εξέλιξη του λυγισμού των τελευταίων. (β) Η αντοχή σε συνάφεια μεταξύ των ενωμένων με παράθεση ράβδων και του περισφιγμένου με μανδύες ΙΑΜ ή ΙΟΠ σκυροδέματος. Ιδιαίτερη έμφαση δίνεται στην πειραματική και αναλυτική μελέτη του μηχανισμού με τον οποίο η περίσφιγξη με μανδύες ΙΟΠ και ΙΑΜ συνεισφέρει στη βελτίωση των συνθηκών συνάφειας μεταξύ ράβδων οπλισμού και σκυροδέματος. Ακόμα στην παρούσα διδακτορική διατριβή διεξάγεται η πρώτη συστηματική μελέτη καμπτικής ενίσχυσης υποστυλωμάτων υπό ανακυκλιζόμενη κάμψη (και σταθερό αξονικό φορτίο) με Πρόσθετους Οπλισμούς νέου τύπου σε Εγκοπές (ΠΟΕ). Εξετάζονται υποστυλώματα που έχουν ενισχυθεί με πρόσθετο οπλισμό ινοπλισμένων πολυμερών (ελάσματα άνθρακα ή ράβδους γυαλιού) καθώς και με ράβδους ανοξείδωτου χάλυβα τοποθετημένων σε εγκοπές. Άλλη μια καινοτομία που εισαγάγει η παρούσα διατριβή είναι ο συνδυασμός του ΠΟΕ με τοπικούς μανδύες ινοπλεγμάτων σε ανόργανη μήτρα (IAM), οι οποίοι αποτελούν ένα εξαιρετικά αποτελεσματικό και πολλά υποσχόμενο σύστημα περίσφιγξης, όπως αναπτύσσεται και περιγράφεται λεπτομερώς στην παρούσα διδακτορική διατριβή. Η έρευνα που υλοποιείται για την απόκτηση δεδομένων γύρω από τη συμπεριφορά υποστυλωμάτων οπλισμένου σκυροδέματος ενισχυμένων σε κάμψη με ΠΟΕ, περιλαμβάνει τη διεξαγωγή 11 δοκιμών επί υποστυλωμάτων πλήρους κλίμακας, τα οποία υποβάλλονται σε ανακυκλιζόμενη κάμψη υπό σταθερό αξονικό φορτίο. . Καταδεικνύεται ότι μέσω ενός κατάλληλου σχεδιασμού, στα πλαίσια του οποίου ο ΠΟΕ συνδυάζεται με τοπικό μανδύα στα άκρα του υποστυλώματος (κορυφή και πόδα), είναι εφικτό η αύξηση της καμπτικής αντίστασης των υποστυλωμάτων να μην συνοδεύεται από μείωση της διαθέσιμης ικανότητας παραμόρφωσης. Τα χρήσιμα πειραματικά ευρήματα από τα ενισχυμένα με ΠΟΕ υποστυλώματα, συμπληρώνονται με την ανάπτυξη ενός αναλυτικού και υπολογιστικού προσομοιώματος, το οποίο έχει διττή συμβολή, καθώς επιτρέπει: (α) την εκτέλεση παραμετρικών αναλύσεων ώστε να μελετηθεί σε βάθος και χωρίς κόπο (πειραματικές δοκιμές) η επίδραση όλων σχεδόν των παραμέτρων, στην καμπτική αντίσταση των ενισχυμένων με ΠΟΕ υποστυλωμάτων. (β) Τη χρήση του ως πολύτιμου υπολογιστικού εργαλείου από το Μηχανικό για το σχεδιασμό καμπτικών ενισχύσεων υποστυλωμάτων με ΠΟΕ και / ή μανδύες συνθέτων υλικών. Η αξία της συμβολής του εν λόγω προσομοιώματος μεγιστοποιείται αν ληφθούν υπόψη ορισμένα χαρακτηριστικά του όπως: (1) Η μείωση των ροπών αντοχής ως προς τους δύο κύριους άξονες (ισχυρός και ασθενής), η οποία οφείλεται στην έντονη σύζευξή τους, για τα ενισχυμένα σε κάμψη υποστυλώματα που υποβάλλονται σε διαξονική κάμψη. (2) Η εφαρμογή ενός τραπεζοειδούς στερεού τάσεων για το σκυρόδεμα σε θλίψη, το οποίο σε σύγκριση με το κλασικό ορθογωνικό στερεό, προσομοιώνει με αρκετά μεγαλύτερη ακρίβεια τον όγκο του σκυροδέματος της θλιβόμενης ζώνης, ιδιαίτερα για τις ενισχυμένες διατομές. (3) Η ταυτόχρονη δράση της εξωτερικής περίσφιγξης με μανδύες συνθέτων υλικών στις ενισχυμένες σε κάμψη διατομές. / The effectiveness of a new structural material, namely Textile-Reinforced Mortar (TRM), was investigated experimentally in this PhD Thesis as a means of confining old-type reinforced concrete (RC) columns with limited capacity due to bar buckling or due to bond failure at lap splice regions. Comparisons with equal stiffness and strength fiber-reinforced polymer (FRP) jackets allow for the evaluation of the effectiveness of TRM versus FRP. Tests were carried out on nearly full scale non-seismically detailed RC columns subjected to cyclic uniaxial flexure under constant axial load. Thirteen cantilever-type specimens with either continuous or lap-spliced deformed longitudinal reinforcement at the floor level were constructed and tested. Experimental results indicated that TRM jacketing is quite effective as a means of increasing the cyclic deformation capacity of old-type RC columns with poor detailing, by delaying bar buckling and by preventing splitting bond failures in columns with lap-spliced bars. Compared with their FRP counterparts, the TRM jackets used in this study were found to be equally effective in terms of increasing both the strength and deformation capacity of the retrofitted columns. From the response of specimens tested in this study, it can be concluded that TRM jacketing is an extremely promising solution for the confinement of RC columns, including poorly detailed ones with or without lap splices in seismic regions. Moreover this PhD Thesis presents the results of a large-scale experimental program aiming to study the behavior of RC columns under simulated seismic loading, strengthened in flexure (of crucial importance in capacity design) with different types and configurations of near-surface mounted (NSM) reinforcing materials. The role of different parameters is examined, by comparison of the lateral load versus displacement response characteristics (peak force, drift ratios, energy dissipation, stiffness). Those parameters were as follows: carbon or glass fiber-reinforced polymers (FRP) versus stainless steel; configuration and amount of NSM reinforcement; confinement via local jacketing; and type of bonding agent (epoxy resin or mortar). The results demonstrate that NSM FRP or stainless steel reinforcement is a viable solution towards enhancing the flexural resistance of reinforced concrete columns subjected to seismic loads. With proper design, which should combine compulsory NSM reinforcement with local jacketing at column ends, it seems that column strength enhancement does not develop at the expense of low deformation capacity.

[pt] Estruturas cada vez mais esbeltas têm sido usadas para otimizar edifícios de grande porte e reduzir custos, inclui-se nisto o pé-direito das edificações e portanto a altura das vigas. Grandes vãos são cada vez mais comuns, principalmente quando se utiliza aço em edificações, gerando então amplos espaços de serviço em uma direção, mas obstáculos na outra pela continuidade das vigas. A utilização de aberturas na alma das vigas para passagem de tubulações de ar-condicionado, incêndio, etc., evita um acréscimo na altura. Em consequência há uma grande diminuição da capacidade resistente nestes elementos estruturais que dependem diretamente da forma, do tamanho e da posição destas aberturas. A presente dissertação descreve alguns métodos construtivos de aberturas em almas de vigas de aço, cálculos de dimensionamentos e normas relacionadas. Alguns estudos numéricos com aplicações do método dos elementos finitos foram realizados investigando: angulação de aberturas hexagonais, vigas com três aberturas nos terços médios, vigas casteladas (tipo Litzka, com quantidades diferentes de aberturas), vigas expandidas em altura e uma viga Litzka Expandida. Para tal, utilizou-se de seis perfis de uso prático e comparando-os entre estas alternativas descritas. A viga Litzka Expandida se destacou em resistência quando comparada com outros métodos de fabricação, como também pelo menor peso linear, praticidade na fabricação e posicionamento das aberturas. / [en] More slender structures are used in order to reduce costs, floors depht and floor to ceiling clear heights. Steel construction and composite construction for buildings often employs long spans for beams and girders, offering service room between beams in one direction only. The use of web openings for passage of service ducts avoids increasing the depth of construction. Beams with web openings have reductions on flexural and shear resistances depending on the geometry, size and position of such openings on the beam. This dissertation presents some construction methods of beam web openings, analysis and design recommendations, related standards and codes. Some numerical studies by the finite elements method were carried out and results are presented for: type of openings, number and spacing of openings, castelled beams (Litzka type and nonuniform distribution of openings) and expanded in depth beams. For this purpose, six commonly used profiles were used for testing the described web openings solutions. Some comparison results are presented. The Litzka type of web expanded beam presented the best performance in terms of strength, easy of fabrication and reduction of material costs.