En esta investigación, se evalúa el comportamiento elasto- plástico y el desempeño sísmico de estructuras aporticadas aplicando el método Pushover. Esta evaluación se hace sobre diversos casos de edificios reforzados con acero de alta ductilidad (Grado 40), acero convencional (Grado 60) y acero de alta resistencia (Grado 75). Para lo anterior, se realiza la evaluación de la capacidad de deformación de los elementos estructurales a partir de las gráficas de momento-rotación de los elementos estructurales más críticos que causa el colapso de la estructura. También, se utilizó la gráfica de curva de capacidad obtenida a partir del método de coeficientes de desplazamiento para medir la capacidad de la estructura. Teniendo en cuenta los valores resultantes de ductilidad y rigidez de cada caso, se evalúa el desempeño de la estructura para diferentes niveles de diseño sísmico. Los resultados mostraron que reforzar una estructura con un acero de Grado 40 aumenta la capacidad de disipación de energía, y si se refuerza con acero de grado 75 aumenta la capacidad de resistencia en la estructura. Finalmente, se presenta el resultado comparativo de los diversos casos para demostrar la influencia del acero de refuerzo en el comportamiento plástico de las estructuras de concreto armado. / In this investigation, the elasto-plastic behavior and the seismic performance of concrete reinforced frame structures are evaluated by applying the Pushover method. This evaluation is done on several cases: with high ductility steel (Grade 40), conventional steel (Grade 60) and high strength steel (Grade 75). For the above, the capacity curve graph obtained from the displacement coefficient method was used to measure the capacity of the structure. In addition, the performance of the structure for different levels of seismic design are evaluated with the resulting values of ductility and rigidity in each case. The results showed that reinforcing a structure with a Grade 40 reinforcing steel increases the energy dissipation capacity, and if reinforced with a Grade 75 reinforcing steel it increases the strength capacity in the structure. Finally, the comparative result of the various cases is presented to demonstrate the influence of reinforcing steel on the plastic behavior of concrete reinforced frame structures. / Tesis

El uso del concreto de alta resistencia está permitiendo la construcción de edificaciones cada vez más altas, la mejora de sus propiedades mecánicas con respecto al de un concreto de resistencia normal produce menor desplazamiento lateral y con ellos le da más resistencia a la rigidez lateral. Una de las interrogantes es conocer en qué medida mejora el comportamiento sísmico de una edificación con el aumento de la resistencia mecánica del concreto y sobre todo con alta resistencia (55MPa), ya que permite la construcción de elementos más esbeltos. El presente proyecto de investigación tiene como objetivo principal analizar la respuesta sísmica de manera más precisa ante una liberación súbita de energía de gran magnitud. Para llevarlo a cabo se planteó el concepto y diferencias entre un concreto normal y uno de alta resistencia. Asimismo, el aporte de investigaciones científicas que ayudaron a comprender mejor el comportamiento mecánico de un concreto de alta resistencia en diferentes elementos estructurales. Se realizaron análisis y diseño estructural de una edificación de 20 pisos con f’c de 21,35, 55 MPa y un Mix de 21-55 y 35-55 MPa donde se le sometió a un empuje lateral mediante un Pushover para generar mecanismos de rotulación hasta lograr el colapso de la estructura y con ella la obtención de la curva de capacidad. Generando cinco espectros de demanda con un periodo de retorno de 43, 72, 475, 975,1500 años para poder interceptarlo con la curva de capacidad y obtener el punto de desempeño de la estructura. / The use of high-strength concrete is allowing the construction of increasingly taller buildings, the improvement of its mechanical properties with respect to that of a normal-strength concrete produces less lateral displacement and with them gives more resistance to lateral stiffness. One of the questions is to know to what extent the seismic behavior of a building improves with the increase in the mechanical resistance of the concrete and especially with high resistance (55MPa), since it allows the construction of slenderer elements. The main objective of this research project is to analyze the seismic response more precisely in the face of a sudden release of energy of great magnitude. To carry it out, the concept and differences between normal and high-strength concrete were raised. Also, the report of scientific research that helped to better understand the mechanical behavior of high-strength concrete in different structural elements. Analysis and structural design of a 20-story building with f'c of 21.35, 55 MPa and a Mix of 21-55 and 35-55 MPa were carried out where it was subjected to a lateral push by means of a Pushover to generate mechanisms of labeling until the collapse of the structure and with it the achievement of the capacity curve. Generating five demand spectra with a return period of 43, 72, 475, 975,1500 years to be able to intercept it with the capacity curve and obtain the performance point of the structure. / Tesis

Low-aspect-ratio reinforced concrete (RC) shear walls, characterized by height-to-length ratios of less than two, have been widely used as a seismic force-resisting system (SFRS) in a wide array of structures, ranging from conventional buildings to critical infrastructure systems such as nuclear facilities. Despite their extensive applications, recent research has brought to light the inadequate understanding of their seismic performance, primarily attributed to the intricate nonlinear flexure-shear interaction behaviour unique to these walls. In this respect, the current research dissertation aims to bridge this knowledge gap by conducting a comprehensive evaluation to quantify the seismic performance of low-aspect-ratio RC shear walls when used in different applications. Chapter 2 focuses on low-aspect-ratio RC shear walls that are employed in residential and industrial structures. Considering their significance, the seismic response modification factors of such walls, as defined in various standards, are thoroughly examined and evaluated utilizing the FEMA P695 methodology. The analysis revealed potential deficiencies in the current code-based recommendations for response modification factors. Consequently, a novel set of response modification factors, capable of mitigating the seismic risk of collapse under the maximum considered earthquake, is proposed. Such proposed values can be integrated into the forthcoming revisions of relevant building codes and design standards. While the FEMA P695 methodology offers a comprehensive approach to assessing building seismic performance factors, its practical implementation is associated with many challenges for practicing engineers. Specifically, the methodology heavily relies on resource-intensive and time-consuming incremental dynamic analyses, making it less feasible for routine engineering practices. To enhance its practicality, a data-driven framework is developed in Chapter 3, circumventing the need for such demanding analyses. This framework provides genetic programming-based expressions capable of producing accurate predictions of the median collapse intensities—a key metric in the acceptance criteria of the FEMA P695 methodology, for different structural systems. To demonstrate its use, the developed framework is operationalized to low-aspect-ratio RC shear walls and the predictive expression is evaluated considering several statistical and structural parameters, which showed its adequacy in predicting the median collapse intensities of such walls. Furthermore, the adaptability of this framework is showcased, highlighting its applicability across various SFRSs. Chapters 4 and 5 tackle the scarcity of experimental assessments pertaining to the seismic performance of low-aspect-ratio RC walls in nuclear facilities. The seismic hybrid simulation testing technique is employed herein to merge the simplicity of numerical simulations with the efficiency of experimental tests. Hybrid simulation can overcome obstacles related to physical specimen sizes, limited actuator capacities, and space constraints in most laboratories. In these two chapters, the experimental program delves into evaluating the seismic performance of three two-storey low-aspect-ratio nuclear RC walls under different earthquake levels, including operational, design, and beyond-design-level scenarios. Diverse design configurations, including the use of increased thickness boundary elements and different materials (i.e., normal- and high-strength reinforcement), are considered in such walls to provide a comprehensive understanding of several structural parameters and economic metrics. Key structural parameters, such as the force-displacement responses, multi-storey effects, lateral and rotational stiffnesses, ductility capacities, displacement components, rebar strains, crack patterns and damage sequences, are all investigated to provide direct comparisons between the walls in terms of their seismic performances. Additionally, economic metrics, including the total rebar weights, overall construction costs and the expected seismic repair costs, are considered in order to evaluate the seismic performance of the walls considering an economic perspective. The findings of this experimental investigation are expected to inform future nuclear design standards by enhancing the resilience and safety of their structures incorporating low-aspect-ratio RC shear walls. / Thesis / Doctor of Philosophy (PhD)

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Η πλειονότητα των ερευνητών/ειδικών του αντισεισμικού σχεδιασμού συμφωνεί πως μια υπολογιστική διαδικασία που θα έχει ως βασική παράμετρο της απόκρισης τις σεισμικές μετακινήσεις θα είναι πιο ορθολογική και πιθανότατα πιο οικονομική απ’ τη συμβατική μεθοδολογία σχεδιασμού βάσει δυνάμεων. Η έλλειψη μιας μεθοδολογίας αντισεισμικού σχεδιασμού γεφυρών βάσει μετακινήσεων που να είναι απλή, εφικτή και συμβατή με την εφαρμοζόμενη πρακτική και η απουσία πρότασης σχεδιασμού των περιοχών του φορέα βάσει μετακινήσεων, αποδεικνύει το γνωστικό κενό που υπάρχει σ’ αυτή την περιοχή του αντισεισμικού σχεδιασμού. Η παρούσα εργασία επιχειρεί να συμβάλλει στην πλήρωση αυτού του κενού και προς τούτο προτείνει μια νέα μεθοδολογία. Αναφέρεται σε (μή-μονωμένες) γέφυρες σκυροδέματος και περιλαμβάνει μια απλή διαδικασία για την εκτίμηση των απαιτούμενων ανελαστικών παραμορφώσεων, τόσο των βάθρων, όσο και των περιοχών του φορέα - κάνοντας χρήση ελαστικής φασματικής ανάλυσης και επεκτείνοντας τον κανόνα των "Ίσων Μετακινήσεων" στο τοπικό επίπεδο. Η διαδικασία αναπτύσσεται και βαθμονομείται βάσει (σχεδόν δύο χιλιάδων) μή-γραμμικών δυναμικών αναλύσεων (με εν χρόνω ολοκλήρωση) αντιπροσωπευτικών γεφυρών, τριών έως πέντε ανοιγμάτων. Όμως για την εφαρμογή της απαιτούνται μόνο ελαστικά εργαλεία. Σε αντίθεση με τις έως τώρα ερευνητικές προσπάθειες, όπου γίνεται η απλουστευτική παραδοχή γραμμικής συμπεριφοράς του φορέα, στην παρούσα έρευνα δίνεται έμφαση στην προσομοίωση των περιοχών του φορέα και λαμβάνονται υπ’ όψιν οι μή-γραμμικότητές του. Από την εφαρμογή του διαπιστώνεται ότι ο προτεινόμενος σχεδιασμός βάσει μετακινήσεων προσφέρει πολύ οικονομικότερα ποσοστά όπλισης (από 1/2 έως 1/7 στο διαμήκη οπλισμό και από 1/1 έως 1/3 στον εγκάρσιο οπλισμό), χωρίς να επιβαρύνει ουσιαστικά την επιτελεστικότητα της γέφυρας - η υπεραντοχή των γεφυρών που σχεδιάζονται με την προτεινόμενη μεθοδολογία είναι πρακτικά ισοδύναμη με την υπεραντοχή των συμβατικά σχεδιασμένων γεφυρών. Η παρουσίαση της μεθοδολογίας περιλαμβάνει την περιγραφή της διαδικασίας σχεδιασμού υπό μορφή αλγόριθμου (Κεφ. 2), του τρόπου εφαρμογής της στην πράξη (διαδικασία προσομοίωσης, παραδείγματα σχεδιασμού: Κεφ. 3), του θεωρητικού υποβάθρου βάσει του οποίου αναπτύχθηκε (Κεφ. 4), των προβλημάτων της συμβατικής μεθοδολογίας (παραδείγματα σχεδιασμού βάσει δυνάμεων: Κεφ. 3) και των κενών που διαπιστώνονται στην τεκμηρίωση της συμβατικής μεθοδολογίας (Κεφ. 4). Η αποτίμηση του σχεδιασμού (Κεφ. 3) δεκαέξι αντιπροσωπευτικών γεφυρών (οκτώ σχεδιασμένων βάσει μετακινήσεων και οκτώ συμβατικά σχεδιασμένων), παρουσιάζεται υπό μορφή παράλληλης σύγκρισης της επιτελεστικότητας και συνηγορεί υπέρ των πλεονεκτημάτων της νέας μεθοδολογίας. Στα Παραρτήματα δίνονται πληροφορίες για τα υπολογιστικά εργαλεία που αναπτύχθηκαν για την προσομοίωση και την ανάλυση των γεφυρών (επέκταση προγράμματος ANSRuop). / The majority of seismic design researchers/specialists concludes that displacement-based design methodologies reduce the uncertainty of the design process and probably lead to less expensive structures. The absence of a simple displacement-based seismic design procedure for bridges that will be feasible and compatible with the current design practice and the nonexistence of a proposal for the displacement-based design of the deck indicate the gap of knowledge in this field of earthquake engineering. This thesis attempts to contribute to the reduction of this gap and for this scope proposes a new methodology. The procedure focuses on bridges with concrete piers monolithically connected to a prestressed concrete continuous deck and comprises simple steps for the estimation of the inelastic/nonlinear deformations of both the piers and the deck - through elastic modal response spectrum analysis, extending the applicability of the "equal displacement" rule to the level of member deformations. About two thousands nonlinear dynamic (time-history) analyses of several representative bridges (with deck of three or five spans) are used for the development and the calibration of the procedure. However, for the application of the methodology only elastic modal response spectrum analysis is needed. Contrary to other current researches, which adopt the hypothesis of deck elastic response, the nonlinearities of the deck are modeled. The proposed displacement-based procedure offers lower reinforcement ratios (from 1/2 to 1/7 for the longitudinal reinforcement and from 1/1 to 1/3 for the transverse reinforcement) at no detriment to the expected seismic performance - the global overstrength of the bridges which are designed with the proposed procedure is practically equivalent to the global overstrength of the conventionally designed bridges (current force-based design). The step by step description of the design algorithm (Chap. 2) is followed by the practical application of the methodology (modeling aspects, design examples: Chap. 3), the conceptual justification (Chap. 4), the deficiencies of the conventional design procedure (force-based design examples: Chap. 3) and the fallacies in the justification of the conventional design methodology (Chap. 4). Comparative performance-based design evaluation (Chap. 3) of sixteen representative bridges (eight bridges subjected to alternative seismic design) indicates the benefits of the proposed procedure. The computational capabilities which were developed for the modeling and the analysis of the bridges are described in the appendices (upgrade of program ANSRuop).

Ce mémoire présente les travaux de thèse visant à étudier le comportement parasismique des éléments de murs à ossature en bois aux travers d’approches expérimentales et du développement d’une méthodologie d’application de méthodes basées sur la performance sismique. Les approches expérimentales sont constituées de trois campagnes d’essais : (1) une série d’essais monotones et cycliques à l’échelle d’assemblages agrafés et pointés, (2) une série d’essais monotones et cycliques à l’échelle de l’élément de mur à ossature en bois et (3) une série d’essais dynamiques sur table vibrante. La base de données constituée par les résultats d’essais permet alors l’examen des propriétés de résistance et de raideur des éléments de murs suivant les conditions de sollicitation (vitesse d’essai, chargement vertical). Le développement d’une modélisation à l’échelle macro du comportement cyclique et dynamique de tels éléments est également proposé à l’aide de modèles de loi de comportement hystérétiques. Une méthodologie d’application aux structures à ossature bois de méthodes basées sur la performance sismique (méthode N2 et MPA) ainsi qu’une analyse de vulnérabilité - construction de courbes de fragilité - à l’aide de la méthode N2 sont proposées. / This thesis presents a study of the seismic behavior of light timber frame walls with stapled and nailed sheathings through experimental approaches and the development of a methodology for the application of seismic performance-based methods. The experimental approaches consist of three test campaigns: (1) a series of static tests on stapled and nailed connections, (2) a series of static tests performed on light timber frame walls and (3) a series of dynamic tests performed on light timber frame walls on a vibrating table. The database consists of these test results then allows the examination of strength and stiffness properties of the wall elements according to the stress conditions (strain rate, vertical load). The development of a macro-scale modeling of the cyclic and dynamic behavior of such elements is also proposed using constitutive law models. A framework of the application to light timber frame structures of seismic performance-based methods based (N2 method and MPA method) and a vulnerability analysis - fragility curves - using the N2 method are proposed.