The determination of the tensile properties of such a deflection hardening response material as UHPFRC is a serious challenge for both researchers and designers. This process involves many factors, such as specimen size, fibre orientation or test typology. The socalled inverse analysis is used to obtain the tensile constitutive properties that are consistent with the specimen response in a bending test. This work focuses on the inverse analysis process. The main aim is to develop a new back-calculation methodology, which is easy to implement, reliable, quick and is consistent with the measurements taken from a four-point bending test. The new methodology proposed has been validated using an analytical formulation and the experimental results of others authors. This paper also includes an application example of how this methodology works.
No part of this volume may be produced, stored in retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publishers. Los límites son físicos. Las limitaciones, mentales. Summary Dosage optimization and bolted connections for UHPFRC tiesConcrete technology has been in changeful evolution since the Roman Empire time. It is remarkable that the technological progress became of higher magnitude from the second part of the XX Century. Advances in the development of new cements, the appearance of the fibers as a reinforcement for structural applications, and specially the grand progress in the field of the water reducing admixtures enabled the emergence of several types of special concretes. One of the lasts is the Ultra High Performance Fiber Reinforced Concrete (UHPFRC), which incorporates advances of the Self-Compacting Concrete (SCC), Fiber-Reinforced Concrete (FRC) and Ultra High Strength Concrete (UHSC) technology. This exclusive material requires a detailed analysis of the components compatibility and a high control of the materials and processes. Mainly patented products have been used for the few structural elements carried out so far today, but the costs makes doubtful the development of many other potential applications.In accordance with the previously explained, a simplification of the UHPFRC components and processes is needed. This becomes the first main goal of this Ph.D. thesis, which emphasizes in the use of local available components and simpler mixing processes. Moreover, the singular properties of this material, between ordinary concrete and steel, allow not only the realization of slenderer structures, but also the viability of new concepts unthinkable with ordinary concrete. In this field is focused the second part of the Ph.D. thesis, which develops a bolted connection system between UHPFRC elements. This research summarizes, first of all, the subfamilies belonging to the HPC-UHPC materials. Afterwards, it is provided a detailed comparison between the dosage and properties of more than a hundred of mixtures proposed by several authors in the last ten years of technology. This becomes a useful tool to recognize correlations between dosages and properties and validate or no preconceived ideas about this material.Based on this state of art analysis was performed the later development of mixtures, on Chapter 4, which analized the effect of use of simpler components and processes on the UHPFRC. The main idea was use local components available in the Spanish market, identifying the combinations that provide the best rheological and mechanical properties. Steam curing use was avoided since a process simplification is intended. Diferent dosages were developed to be adapted to various levels of performance, and always trying to be as economical as possible. The concretes designed were selfcompacting and mainly combined two fiber types (hybrid), as the flexural performance was of greater relevanc...
ResumenLa seguridad vial es uno de los problemas más importantes de sociedad actual, causando centenares de miles de víctimas mortales cada año en todo el mundo.En la generación de un accidente intervienen diversos factores, siendo los más relevantes el factor humano y la infraestructura, así como su interacción. Sobre dicha interacción se ha investigado mucho en los últimos años, ampliando la comprensión sobre el proceso de conducción y dando lugar a mejoras que, en muchos casos, todavía no han sido transcritas a las guías de diseño.Algunos de estos avances se centran sobre la comprensión de los procesos cognitivos involucrados en la tarea de conducción; en la respuesta de los conductores y en la mejor estimación de la siniestralidad. Ligado a todo ello está el concepto de consistencia. Se entiende como tal al grado de adecuación entre las expectativas de los conductores y el comportamiento de la carretera. Así pues, una carretera inconsistente produce sorpresas en los conductores, potencialmente derivando en una mayor siniestralidad.En esta tesis se desarrolla un modelo de consistencia global basado en el análisis de la velocidad de operación. Se han tratado más de 150 tramos homogéneos de carreteras convencionales de la Comunidad Valenciana, extrayendo diversos parámetros operacionales y determinando cuáles presentan una mayor relación con la siniestralidad.Para posibilitar el estudio, se han creado diversas herramientas auxiliares, algunas de las cuales constituyen igualmente una importante innovación. Dos ejemplos son un nuevo método analítico-heurístico de restitución geométrica en planta basado en el azimut, así como una nueva metodología de tramificación de carreteras convencionales o unas expresiones para determinar de forma más precisa la velocidad de proyecto idónea para un tramo homogéneo.El modelo de consistencia obtenido puede servir de base para la estimación de la siniestralidad, a través de safety performance functions. Con el objetivo de integrar todos estos avances, se propone una nueva metodología de diseño de carreteras que, complementando las actuales guías, permite considerar el carácter continuo de la seguridad vial en el proceso de diseño. DEVELOPMENT AND CALIBRATION OF A GLOBAL GEOMETRIC DESIGN CONSISTENCY MODEL FOR TWO-LANE RURAL HIGHWAYS, BASED ON THE USE OF CONTINUOUS OPERATING SPEED PROFILES II ResumLa seguretat viària és un dels problemes més importants de la societat actual, causant centenars de milers de víctimes mortals cada any a tot el món.A la generació d'un accident de trànsit hi intervenen diversos factors, dels quals els més importants són el factor humà i la infraestructura, així com la seua interacció. Als últims anys s'ha investigat molt al voltant d'eixa interacció, ampliant el coneixement sobre el procés de conducció, donant lloc a millores que, en molts cassos, encara no hi han sigut transcrites a les guies de disseny.Alguns d'aquests avanços es centren sobre la comprensió dels processos cognitius involucrats en la tasca de conducció; en la resposta dels conductors i...
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