Ductility of wide-beam RC frames as lateral resisting system

[EN] Some Mediterranean seismic codes consider wide-beam reinforced concrete moment resisting frames (WBF) as horizontal load carrying systems that cannot guarantee high ductility performances. Conversely, Eurocode 8 allows High Ductility Class (DCH) design for such structural systems. Code prescriptions related to WBF are systematically investigated. In particular, lesson learnt for previous earthquakes, historical reasons, and experimental and numerical studies underpinning specific prescriptions on wide beams in worldwide seismic codes are discussed. Local and global ductility of WBF are then analytically investigated through (1) a parametric study on chord rotations of wide beams with respect to that of deep beams, and (2) a spectral-based comparison of WBF with conventional reinforced concrete moment resisting frames (i.e. with deep beams). Results show that the set of prescriptions given by modern seismic codes provides sufficient ductility to WBF designed in DCH. In fact, global capacity of WBF relies more on the lateral stiffness of the frames and on the overstrength of columns rather than on the local ductility of wide beams, which is systematically lower with respect to that of deep beams.Gómez-Martínez, F.; Alonso Durá, A.; De Luca, F.; Verderame, GM. (2016). Ductility of wide-beam RC frames as lateral resisting system. Bulletin of Earthquake Engineering. 14(6):1545-1569. doi:10.1007/s10518-016-9891-xS15451569146ACI (1989) Building code requirements for reinforced concrete (ACI 318-89). ACI Committee 318, American Concrete Institute, Farmington Hills, Michigan, USAACI (2008) Building code requirements for structural concrete (ACI 318-08) and commentary (318-08). ACI Committee 318, American Concrete Institute, Farmington Hills, Michigan, USAACI-ASCE (1991) Recommendations for design of beam-column connections in monolithic reinforced concrete structures (ACI 352R-91). 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Investigation on the seismic behavior of RC interior wide-beam connections.

An investigation was conducted to evaluate the response of banded-floor systems to earthquake loading. A banded-floor system, also called wide-beam system, consists of slabs carried by shallow, wide beams that frame into columns. Wide-beam systems have several advantages, most of them related to construction cost minimization. Because of those advantages, banded-floor construction is widely used in non-seismic regions as a primarily gravity load carrying system. In spite of the several features that makes banded-floor construction an attractive alternative as a structural system for buildings, most design codes restrict its use in regions of high seismicity because of lack of sufficient information on how the system would behave under severe earthquake loading. The experimental component of this investigation focused on the response of interior wide beam-to-column connections subjected to lateral earthquake-type loading. Three interior wide beam-column-slab subassemblages were tested under quasi-static cyclic loading. It was found that these connections, when properly designed, possess adequate strength and deformation capacity. The connections reached their expected capacities and maintained them throughout a severe deformation history. The hysteretic response of I interior wide-beam connections to lateral cyclic loading is controlled by the bond behavior of the longitudinal reinforcement, in particular, the reinforcement passing outside the column core. When the bond parameters are permitted to be close to the limits proposed by ACI Committee 352, pinching of the load vs. displacement hysteretic loops is present. On the other hand, when the bond parameters are improved, robust hysteretic response is observed. An evaluation of the dynamic response of wide-beam buildings to earthquake loading was performed via computer simulation, Hysteretic models obtained from the experimental investigation were used in nonlinear dynamic analyses of prototype low- and medium-rise wide-beam buildings. It was found that buildings comprised of exterior normal beam frames and interior wide-beam frames are able to withstand severe earthquake excitations without developing a collapse mechanism and without exceeding reasonable levels of interstory drift. The use of dual systems (structural walls and wide-beam frames) is an effective design solution for taller structures in which high interstory drifts would prevent the use of pure frame systems. Overall, it was found that when specific design guidelines are followed, banded-floor construction can be safely used in seismic zones.Ph.D.Applied SciencesCivil engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/130802/2/9811163.pd

¿ES POSIBLE PREDECIR LA DIFICULTAD DE PREGUNTAS DE COMPRENSIÓN DE LECTURA EN INGLÉS CIENTÍFICO Y TÉCNICO (ICT) A PARTIR DEL ANÁLISIS DE SU PERFIL LÉXICO?

Las investigaciones sobre comprensión de lectura en L1 y L2 atribuyen al perfil léxico de los textos un papel clave en las fórmulas de lecturabilidad, privilegiándolo sobre otras variables (Chall, 1984; Day, 1994; Nuttall, 1996; Read, 1997, entre otros). En el presente estudio se explora la posible correlación estadística entre el perfil léxico y el índice de dificultad de los ítems que integran las pruebas de logro en el contexto de un programa de lectura en inglés científico y técnico dirigido a hispanohablantes. Para ello, se calcularon la relación tipo-muestra; los porcentajes de palabras de alta frecuencia, de vocabulario académico, de vocabulario científico general y de palabras de etimología greco-latina en dichos ítems. Nuestros resultados indican que el perfil léxico per se no determina el nivel de dificultad. Las deficiencias de los aprendices en cuanto a la amplitud de sus inventarios léxicos en la L2 y sus fallas en el reconocimiento de cognados inglés-español podrían dar cuenta de dicho hallazgo. A pesar de que no permite predecir el nivel de dificultad de los ítems, el análisis de su perfil léxico constituye un valioso insumo durante los procesos de generación y evaluación de preguntas de comprensión de lectura para garantizar su idoneidad.Could Difficulty of English for Science and Technology (EST) Reading-Comprehension Test Items be Predicted by Analysing their Lexical Profile?ABSTRACTResearch in L1 and L2 reading-comprehension assigns a key role to the vocabulary profile of a text in readability formulas, favoring it over other variables (Chall, 1984; Day, 1994; Nuttall, 1996; Read, 1997; etc.). This study explores a possible statistical correlation between lexical profiles and difficulty indexes of the items in a set of achievement tests of a reading program in English for Science and Technology for Spanish-speakers. With this in mind, type-token ratio; percentage of high-frequency words, academic and scientific vocabulary; and the Greco-Latin index for each item were calculated. Our results show that lexical profiles per se do not determine the level of difficulty of an item. Learners’ lack of a minimal lexical threshold in L2 and their failure to recognize English-Spanish cognates may account for these results. Although lexical profile analysis does not allow for item difficulty prediction, it is still essential for guaranteeing the suitability of texts during generation and evaluation of reading comprehension questions.Est-il possible de prédire la difficulté des questions de compréhension de lecture en anglais scientifique et technique (AST) à partir de l’analyse de leur profil lexique ?RÉSUMÉLes recherches sur la compréhension de lecture en L1 et L2 attribuent un rôle clé au profil lexique des textes dans les formules de lisibilité et le privilégient par rapport à d’autres variables (Chall, 1984; Day, 1994; Nuttall, 1996; Read, 1997, entre autres). Dans cette étude, l’on explore la possible corrélation statistique entre le profil lexique et l’indice de difficulté des items qui font partie des épreuves dans le cadre d’un programme de lecture en anglais scientifique et technique pour des hispanophones. L’on a calculé la relation type-échantillon et les pourcentages des mots très fréquents, des mots appartenant au vocabulaire scientifique général et des mots d’origine grecque-latine de ces items-là. D’après les résultats, le niveau de difficulté n’est pas déterminé uniquement par le profil lexique. Les difficultés des étudiants quant à la taille de leurs inventaires lexiques en L2 et leurs problèmes pour reconnaître des semblables anglais-espagnol pourraient avoir aussi de l’influence. Même si l’analyse du profile lexique ne permet pas de prédire le niveau de difficulté des items, celle-ci est un outil important pour poser et pour évaluer des questions de compréhension de lecture et pour garantir qu’elles seront les plus appropriées.É possível predizer a dificuldade de perguntas de compreensão de leitura em Inglês Científico e Técnico (ICT) a partir da análise de seu perfil léxico?RESUMONas pesquisas realizadas em relação à compreensão de leitura em L1 e L2 se afirma que o perfil léxico dos textos tem um papel fundamental nas fórmulas de leiturabilidade, dando a ele mais importância que a outras variáveis (Chall, 1984; Day, 1994; Nuttall, 1996; Read, 1997, entre outros). No seguinte estudo se explora a possível correlação estatística entre o perfil léxico e o índice de dificuldade dos itens que fazem parte das provas de conhecimento no contexto de um programa de leitura em ICT voltado a hispanofalantes. Por isso, foi calculada a relação tipo-amostra, as porcentagens de palavras de alta frequência, de vocabulário acadêmico, de vocabulário científico em geral e de palavras de etimologia greco-latina existente nesses itens. Nossos resultados mostram que o perfil léxico per se não determina o nível de dificuldade. As deficiências dos estudantes em relação à amplitude de seus inventários lexicais na L2 e as falhas para reconhecer cognados inglês-espanhol poderiam servir para demonstrar esses resultado. Apesar de não permitir predizer o nível de dificuldade dos itens, a análise do seu perfil léxico é uma importante fonte de informação durante os processos de geração e avaliação de perguntas de compreensão de leitura para garantir sua idoneidade. &nbsp