Experimental Assessment of the Shear Resistant Behaviour of Precast Concrete Beams with Top Cast-in-Place Concrete Slab

Tesis por compendio[ES] La construcción con elementos prefabricados de hormigón es un sector en alza por la aceleración del proceso constructivo, el ahorro de costes derivados de la obra in situ y la mejora de la calidad y acabados, entre otros. En la construcción prefabricada de estructuras de ingeniería civil como puentes y edificios es frecuente el empleo de vigas prefabricadas de hormigón. La construcción con estas vigas requiere el vertido de una capa de hormigón in situ sobre las mismas tras su emplazamiento, que sirve como elemento integrador para garantizar la unidad estructural. Los elementos estructurales que se obtienen de esta forma son conocidos como vigas compuestas de hormigón. En vigas compuestas, aspectos como la resistencia a rasante de la interfaz entre hormigones han sido estudiados en numerosas publicaciones. No obstante, su comportamiento a cortante no ha sido, por el momento, analizado en profundidad. En consecuencia, existe muy poca información, tanto en la literatura existente como en los códigos de diseño actuales, acerca de la resistencia a cortante de estos elementos, de cómo influye la presencia de una interfaz entre los hormigones en la resistencia a cortante o de cómo contribuye la losa hormigonada in situ a dicha resistencia. La presente tesis doctoral tiene como objetivo estudiar la resistencia a cortante de vigas compuestas de hormigón. Para ello, se desarrolla un extenso programa experimental compuesto por vigas monolíticas y compuestas con y sin armadura transversal, con sección transversal rectangular o en forma de T y con hormigones de diferentes calidades en la viga prefabricada y en la losa hormigonada in situ. Se ensaya a cortante un total de 69 vigas de hormigón armado con el fin de analizar las diferentes variables de interés en la resistencia a cortante. A partir de los resultados experimentales, se propone un modelo mecánico de predicción de la resistencia a cortante de vigas compuestas de hormigón con sección transversal rectangular y en forma de T, que también es de aplicación a vigas monolíticas en T. Además, como apoyo al estudio experimental y al modelo mecánico, se modelan numéricamente algunos especímenes del programa experimental. Con todo ello, se busca incrementar el estado actual del conocimiento en este campo, mediante el aporte de un gran número de resultados experimentales y el análisis de los parámetros de diseño, así como sentar las bases para el desarrollo de una formulación de diseño de estructuras compuestas y de evaluación de las ya existentes globalmente aceptada por la comunidad científica.[CA] La construcció amb elements prefabricats de formigó és un sector en alça per l'acceleració del procés constructiu, l'estalvi de costos derivats de l'obra in situ i la millora de la qualitat i acabats, entre altres. En la construcció prefabricada d'estructures d'enginyeria civil com a ponts i edificis és freqüent l'ús de bigues prefabricades de formigó. La construcció amb aquestes bigues requereix l'abocament d'una capa de formigó in situ sobre les bigues després del seu emplaçament, que serveix com a element integrador per a garantir la unitat estructural. Els elements estructurals que s'obtenen d'aquesta forma són coneguts com a bigues compostes de formigó. En bigues compostes, aspectes com la resistència a rasant de la interfície entre formigons han sigut estudiats en nombroses publicacions. No obstant això, el seu comportament a tallant no ha sigut, de moment, analitzat en profunditat. En conseqüència, existeix molt poca informació, tant en la literatura existent com en els codis de disseny actuals, sobre la resistència a tallant d'aquests elements, de com influeix la presència d'una interfície entre els formigons en la resistència a tallant o de com contribueix la llosa formigonada in situ a aquesta resistència. La present tesi doctoral té com a objectiu estudiar la resistència a tallant de bigues compostes de formigó. Per a això, es desenvolupa un extens programa experimental compost per bigues monolítiques i compostes amb armadura transversal i sense, amb secció transversal rectangular o en forma de T i amb formigons de diferents qualitats en la biga prefabricada i en la llosa formigonada in situ. S'assaja a tallant un total de 69 bigues de formigó armat amb la finalitat d'analitzar les diferents variables d'interés en la resistència a tallant. A partir dels resultats experimentals, es proposa un model mecànic de predicció de la resistència a tallant de bigues compostes de formigó amb secció transversal rectangular i en forma de T, que també és aplicable a bigues monolítiques en T. A més, com a suport a l'estudi experimental i al model mecànic, es modelen numèricament alguns espècimens del programa experimental. Amb tot això, es pretén incrementar l'estat actual del coneixement en aquest camp, mitjançant l'aportació d'un gran nombre de resultats experimentals i l'anàlisi dels paràmetres de disseny, així com establir les bases per al desenvolupament d'una formulació de disseny d'estructures compostes i d'avaluació de les ja existents globalment acceptada per la comunitat científica.[EN] Construction with precast concrete elements is a booming sector due to the acceleration of the construction process, the saving of costs arising from the on-site construction and the quality and finish improvement, among others. Precast concrete beams are frequently used in the precast construction of civil engineering structures such as bridges and buildings. Construction with these beams requires the pouring of a cast-in-place concrete layer on top of the beams after their placement, which works as a unifying element to ensure structural integrity. Structural elements obtained in this way are known as concrete composite beams. In composite beams, some aspects such as the shear strength of the interface between concretes have been studied in multiple publications. However, their shear behaviour has not yet been analysed in depth. Consequently, there is very little information, both in the existing literature and in current design codes, about the shear strength of these elements, how the presence of an interface between the concretes influences the shear strength or how the cast-in-place concrete slab contributes to the shear strength. The aim of this doctoral thesis is to study the shear strength of concrete composite beams. For this purpose, an extensive experimental programme is developed, consisting of monolithic and composite beams with and without transverse reinforcement, with rectangular or T-shaped cross-section and with concretes of different qualities in the precast beam and in the slab. A total of 69 reinforced concrete beams are tested under shear forces in order to analyse the different variables of interest in shear strength. Based on the experimental results, a mechanical model for predicting the shear strength of concrete composite beams with rectangular and T-shaped cross-section is proposed, which is also applicable to monolithic T-beams. In addition, to support the experimental study and the mechanical model, some specimens of the experimental programme are numerically modelled. All in all, the aim is to improve the current state of knowledge in this field by providing a large number of experimental results and analysing the design parameters, as well as to lay the foundations for the development of a formulation for the design of existing structures and the assessment of existing ones that is globally accepted by the scientific community.The present doctoral thesis would not have been possible without the financial support of the Ministerio de Ciencia e Innovación (MCIN) and the Agencia Estatal de Investigación (AEI) through Grants BIA2015-64672-C4-4-R and RTI2018- 099091-B-C21-AR, both funded by MCIN/AEI/10.13039/501100011033 and by the “ERDF A way of making Europe”. I am thankful as well for their support through Grant BES-2016-078010 funded by MCIN/AEI/10.13039/501100011033 and by the “ESF Investing in your future”. The project was also supported by the Regional Government of Valencia through Project AICO/2018/250. And finally, thanks to the Concrete Science and Technology University Institute (ICITECH) of the Universitat Politècnica de València (UPV; Spain) in which this research project has been developed, and to our concrete supplier Caplansa.Rueda García, L. (2022). Experimental Assessment of the Shear Resistant Behaviour of Precast Concrete Beams with Top Cast-in-Place Concrete Slab [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/183594TESISCompendi

Diseño, construcción, ensayo y análisis de modelos reducidos de estructuras de hormigón armado: arco rígido triarticulado. Análisis experimental

[EN] This theoretical and experimental study of a real element of reinforced concrete fits properly to the objectives for a degree final project. The design itself represents an application of skills associated with the title, the same way, construction permits implement procedures assimilated theoretically during the degree. By the testing and analysis of results the student can be formed in experimental techniques not acquired in the degree. Arches are structures that work primarily compressed by shape, which has traditionally led to its concrete construction, allowing them to save large spans with reduced use of material. If reinforced concrete is used, in addition, they can resist bending, in which case it is ideal the cross-section height variation for structural optimization. Among all types of reinforced concrete arches employed in history, three-hinged configuration was chosen by its adequacy to experimental analysis, since it shows accurately the stresses in the structure. Further, it is possible to examine the functioning of the joint in the key, so little used today. With cross-section height variation greater efficiency and improved structural elegance criterion are achieved. This final degree project has focused on a reduced model of reinforced concrete consisting of a polygonal three-hinged arch with variable depth, a span of two meters and sixty centimetres of height. This structure has been designed, built entirely by the authors, tested and analyzed using the experiment results. Herein whole process is chronologically presented. An initial approach and preliminary design constraints leads to the final geometry, in which it is based a reinforcement able to resist the internal forces. All this considering characteristics of materials unstated until later. To characterize the concrete was conducted two previous batches. The second phase of this work is the construction of the element, which includes all possible aspects that might occur in a building site: making procedural decisions, procurement of materials, reinforcement, formwork, production, placement and curing of concrete; without leaving aside the quality control and cost. And finally, the structure is prepared and subjected to a laboratory test, which aims to observe their actual behaviour under the action of a monotonically increasing load, to study both the phase of service and the breaking. The experiment results are processed and analyzed to compare them with theoretical values obtained by various methods of calculation.[ES] Este estudio teórico y experimental de un elemento real de hormigón armado se ajusta adecuadamente a los objetivos marcados para un trabajo final de grado. El diseño representa en sí mismo una aplicación de las competencias profesionales asociadas al título, del mismo modo que la construcción permite poner en práctica los procedimientos asimilados de forma teórica durante el Grado. Con el ensayo y análisis de resultados, igualmente, es posible formarse en técnicas experimentales no adquiridas en la titulación. Los arcos son estructuras que trabajan fundamentalmente a compresión por su forma, lo que tradicionalmente ha llevado a su construcción con hormigón, pudiendo salvar grandes luces con un reducido empleo de material. Si se usa hormigón armado, además, pueden resistirse solicitaciones de flexión, en cuyo caso resulta ideal para la optimización estructural la variación de canto. De entre toda la tipología de arcos de hormigón armado empleados en la historia se ha optado por la configuración triarticulada por su adecuación al análisis experimental, ya que permite conocer con precisión los esfuerzos en la estructura. Asimismo, resulta posible examinar el funcionamiento de la articulación en la clave, tan poco usada en la actualidad. Con la variación de canto se consigue una mayor eficiencia, así como una mejora del criterio de elegancia estructural. Este trabajo final de grado se ha centrado en un modelo reducido de hormigón armado consistente en un arco poligonal de canto variable triarticulado, con una luz de dos metros y sesenta centímetros de flecha. Esta estructura ha sido diseñada, construida íntegramente por los autores, ensayada y analizada a partir de los resultados del experimento. En esta memoria se presenta cronológicamente todo el proceso seguido. A partir de un planteamiento inicial de condicionantes y un prediseño se llega a la geometría definitiva, en base a la cual se propone un armado que permita resistir las solicitaciones establecidas. Todo ello considerando unas características de los materiales no constatadas hasta más tarde. Para caracterizar el hormigón se llevaron a cabo dos amasadas previas. La segunda fase de este trabajo es la construcción del elemento, que incluye todas las posibles facetas que podrían presentarse en una obra real: toma de decisiones procedimentales, adquisición de materiales, ferrallado, encofrado, fabricación y puesta del hormigón, curado y desencofrado; sin dejar a parte el control de calidad y de costes. Ya por último, se prepara y somete la estructura a un ensayo de laboratorio, con el que se pretende observar su comportamiento real bajo la acción de una carga monótona creciente, tanto para estudiar la fase de servicio como la de rotura. Los resultados del experimento se procesan y se analizan para poderlos comparar con valores teóricos obtenidos mediante métodos de cálculo variados.[CA] ermet posar en pràctica els procediments assimilats de forma teòrica durant la carrera. Amb l'assaig i anàlisis de resultats, igualment, es possible formar-se en tècniques experimentals no adquirides en la titulació. Els arcs son estructures que treballen fonamentalment a compressió per la seua forma, cosa que tradicionalment ha portat a la seua construcció amb formigó, podent salvar grans llums emprant poc de material. Si s'utilitza formigó armat, amés, poden resistir-se sol'licitacions de flexió, resultant ideal en aquest cas per a la optimització estructural la variació de cantell. De entre tota la tipologia de arcs de formigó armat emprats en la historia s'ha optat per la configuració triarticulada per la seua adequació a l'anàlisi experimental, ja que permet conèixer amb precisió els esforços en la estructura. Així mateix, resultava possible examinar el funcionament de la articulació en la clau, tan poc usada en l'actualitat. Amb la variació de cantell s'aconsegueix una major eficiència, així com una millora del criteri d'elegància estructural. Aquest treball final de grau s'ha centrat en un model reduït de formigó armat que consisteix en un arc poligonal de cantell variable triarticulat, amb una llum de dos metres i seixanta centímetres de fletxa. Aquesta estructura ha sigut dissenyada, construïda integrament pels autors, assajada i analitzada a partir dels resultats del experiment. En esta memòria es presenta cronològicament tot el procés seguit. A partir d'un plantejament inicial de condicionant i un predisseny s'arriba a la geometria definitiva, en base a la qual es proposa un armat que permeta resistir les sol'licitacions establides. Tot açò considerant unes característiques dels materials no constatades fins a més tard. Per a caracteritzar el formigó es van realitzar dues amasades prèvies. La segona fase d'aquest treball es la construcció del element, que inclou totes les possibles facetes que podrien presentar-se en una obra real: presa de decisions procedimentals, adquisició de materials, ferrallat, encofrat, fabricació i posada en obra del formigó, curat i desencofrat; sense oblidar el control de qualitat i de costos. Ja per últim, es prepara i sotmet la estructura a un assaig de laboratori, amb el que es pretén observar el seu comportament real baix l'acció d'una càrrega monòtona creixent, tant per a la fase de servei com la de trencament. Els resultats de l'experiment es processen i analitzen per a poder-los comparar amb valors teòrics obtinguts a mitjançant mètodes de càlcul diversos.Rueda García, L. (2014). Diseño, construcción, ensayo y análisis de modelos reducidos de estructuras de hormigón armado: arco rígido triarticulado. Análisis experimental. http://hdl.handle.net/10251/38776.Archivo delegad

Safety Assessment of Shear Strength Current Formulations for Composite Concrete Beams without Web Reinforcement

[EN] Construction with precast concrete elements without web reinforcement and cast-in-place concrete on them to enhance the overall structure's integrity is a widespread practice in building construction. However as these composite elements' vertical shear strength has not been studied in-depth, a clear criterion about cast-in-place concrete's contribution to shear resistance is still a pending matter. The present study intends to reach practical conclusions about the shear strength assessment of composite concrete elements without web reinforcement. To do so, the shear strengths of 36 specimens, provided by existing shear formulations, were compared: 19 specimens tested by the authors, in which the existence of an interface between concretes, the cross-sectional shape and the concrete compressive strengths of the beam and slab were studied; and 17 specimens taken from a previous study about composite elements by Kim et al. (2016). The applied shear formulations were those of EC2-04, Draft 7 of EC2-20, fib MC-10, ACI 318-19 and the model proposed by Kim et al. (2016). Firstly, specimens' shear strength was calculated by considering that only the beam resisted shear. Secondly according to ACI 318-19 indications about assessing composite elements¿ shear strength, the entire composite element's effective depth was used considering the lower of the compressive strengths of the beam's and slab's concretes and the weighted average of the compressive strengths. Additionally,the entire effective depth and the beam's concrete compressive strength were used. Codes formulations were more precise when estimating the monolithic specimens' shear strengths than those of composites. Therefore, the development of an adapted methodology to assess these elements¿ shear strengths is needed. EC2-20 obtained the most accurate results and gave quite good estimations for composite elements when the entire effective depth and weighted average of the concretes compressive strengths were considered.This study forms part of the research conducted at the Concrete Science and Technology University Institute (ICITECH) of the Universitat Politècnica de València (UPV, Spain) with concrete supplied by Caplansa. The project has been supported by the Spanish Ministry of Science and Innovation through Projects BIA2015-64672-C4-4-R and RTI2018-099091-B-C21-AR; the Regional Government of Valencia through Project AICO/2018/250, and the European Union with FEDER funds. The authors thank the Spanish Ministry of Economy and Business for Grant BES-2016-078010.Rueda-García, L.; Bonet Senach, JL.; Miguel Sosa, P.; Fernández Prada, MÁ. (2021). Safety Assessment of Shear Strength Current Formulations for Composite Concrete Beams without Web Reinforcement. Fédération Internationale du Béton (fib) - International Federation for Structural Concrete. 1-10. http://hdl.handle.net/10251/182209S11

Application of Project-Based Learning in the development of a Bachelor’s Thesis in the Bachelor’s Degree in Civil Engineering

El Aprendizaje Basado en Proyectos (ABP) es un enfoque educativo que consigue motivar al alumnado a través de su implicación activa en el desarrollo de un trabajo que tiene un alto componente práctico. En consecuencia, se genera un aprendizaje profundo de los temas tratados. Con la finalidad de alcanzar estas metas, se aplicó el ABP al Trabajo Final de Grado (TFG) de cuatro alumnos del Grado en Ingeniería Civil de la Universitat Politècnica de València. El trabajo realizado consistió en el diseño, construcción, ensayo y análisis de un modelo reducido de una estructura de hormigón armado. La metodología empleada consistió en la definición de las actividades prácticas y teóricas necesarias para desarrollar el proyecto sobre el elemento estructural y el establecimiento de un sistema de seguimiento por parte del tutor. Los resultados obtenidos demuestran el buen funcionamiento de la innovación, que consiguió motivar a los alumnos, potenciar su aprendizaje y facilitar el alcance de las competencias establecidas en el TFG y otras propias de la titulación, así como despertar el interés de los alumnos por el cálculo de estructuras de hormigón.Project-Based Learning (PBL) is an educational approach that motivates students through their active involvement in the development of a highly practical assignment. As a result, a deep learning process is generated. In order to achieve these goals, PBL was applied to the Bachelor’s Thesis (BT) of four students of the Degree in Civil Engineering of the Universitat Politècnica de València. The work consisted of the design, construction, testing and analysis of a scaled-down model of a reinforced concrete structure. The methodology used consisted of defining the practical and theoretical activities necessary to develop the project on the structural element and the establishment of a monitoring system by the tutor. The results obtained demonstrate the good performance of the innovation, which motivated the students, enhanced their learning and facilitated the achievement of the competences established in the BT and others specific to the degree, as well as awakened the students' interest in the calculation of concrete structures

Estudio de uniones de hormigón armado con barras de aleación con memoria de forma reparadas con CFRP y sometidas a carga cíclica. Parte I: Estudio Teórico. Aplicación práctica a un caso real de viaducto en zona de alta sismicidad en México

[EN] Research in seismic engineering have a very high importance due to the social and economic interest they arouse. The development of new construction materials or the use of existing ones applied to structural engineering is one of the paths to be followed for the creation of new structural systems of protection against earthquakes. In this field, a type of structural joint for protection against earthquakes based on the use of shape memory alloys (SMA) has been recently developed at the Universitat Politècnica de València as substitutes for conventional longitudinal steel reinforcement at joints between elements of reinforced concrete. These give the joint elastic characteristics much higher than those of conventional reinforcement. The purpose of this new type of joints is to replace those joints of the structures in which a high ductility is required. Whereas for a project earthquake, joints with conventional materials would be sufficiently damaged to require major repair or replacement of certain elements, a structure in which the unions are replaced by this type and that suffers the same earthquake would not present the own problems of the failure of the steel reinforcement. There would possibly be a breakage of the concrete at the joint, but the SMA would remain in good condition. For the structure to be put into service again only a minor repair would be necessary. In this framework the investigation of this Master Final Project is carried, in which it is tried to study the correct repair of this type of unions so that they can show correct operation after the occurrence of an earthquake, using the fewest possible resources. With this objective, the reinforcement of structures with fiber reinforced polymers (FRP) is studied. The FRP as external sheathing in beams and columns seeks to increase the resistant capacity of these by the confining pressure it generates on the concrete. To verify its applicability to the repair of unions with SMA, a theoretical study is carried out on how FRP structures behave and an experimental study to determine the correct functioning of FRP repaired unions with SMA. In order to carry out the first task, a thorough review of the state of the art in FRP is made, from which conclusions can be drawn regarding its design and manufacture, to later model the behaviour of the union under study. In order to carry out the experimental study, a campaign of tests is developed to represent the conditions of operation of the reinforced concrete joints before a seismic solicitation. After analyzing the experimental results and validating the proposed numerical model, a practical application of the researched unions is carried out in order to study the global impact on long-term costs of this type of structures developed with non-conventional materials and to study their socio-economic viability.[CA] Les investigacions en enginyeria sísmica presenten una gran importància a causa de l'interés social i econòmic que desperten. El desenvolupament de nous material de construcció o l'ús dels ja existents aplicats a l'enginyeria estructural és un dels camins a seguir per a la creació de nous sistemes estructurals de protecció contra terratrèmols. En aquest àmbit, s'ha desenvolupat recentment a la Universitat Politècnica de València un tipus d'unió estructural per a la protecció contra terratrèmols basada en l'ús d'al·leacions amb memòria de forma (SMA) com a substitutes de les convencionals armadures d'acer longitudinals en les unions entre elements de formigó armat. Aquestes confereixen a la unió unes característiques elàstiques molt superiors a les de les armadures convencionals. La finalitat d'aquest nou tipus d'unions es substituir aquelles unions de l'estructura en les que es requerixca una ductilitat elevada. Mentre que per a un terratrèmol de projecte les unions amb materials convencionals resultarien suficientment danyades com per a requerir una gran reparació o substitució de certs elements, una estructura en la que les unions son substituïdes per aquesta nova unió i que experimenta el mateix sisme no presentaria els problemes propis de l'armadura d'acer. Es tindria possiblement un dany greu del formigó de la unió, però el SMA es mantindria en bon estat. Per a la nova entrada en funcionament de la estructura sols seria necessària una reparació menor. En quest marc es desenvolupa la investigació d'aquest Treball Final de Màster, en el que es pretén estudiar la correcta reparació d'aquest tipus d'unions per a que puguen tornar a presentar un correcte funcionament després de l'esdeveniment del terratrèmol, emprant els menors recursos possibles. Amb aquest objectiu, s'estudia el reforç d'estructures mitjançant l'envoltura amb polímers reforçats amb fibres (FRP). Per a verificar la seua aplicabilitat a la reparació d'unions amb SMA es realitza un estudi teòric de com es comporten les estructures amb FRP i un estudi experimental per a determinar el correcte funcionament de les unions amb SMA reparades amb FRP. Per a realitzar la primera tasca, es fa una revisió exhaustiva del estat de l'art en matèria de FRP, d'on poder extraure conclusions pel que fa a disseny i fabricació per a posteriorment modelitzar el comportament que tindria la unió objecte d'estudi. Per a l¿estudi experimental es desplega una campanya d'assajos que representen les condicions de funcionament de les unions de formigó armat davant d'una sol·licitació sísmica. Una volta analitzats els resultat experimentals y validat el model numèric proposat, es realitza una aplicació pràctica de les unions investigades amb l'objectiu d'estudiar l'impacte global en costos a llarg termini d'aquest tipus de estructures plantejades amb materials no convencionals i estudiar la seua viabilitat socioeconòmica.[ES] Las investigaciones en ingeniería sísmica presentan un alto grado de importancia debido al interés social y económico que despiertan. El desarrollo de nuevos materiales de construcción o el empleo de los ya existentes aplicados a la ingeniería estructural es uno de los caminos a seguir para la creación de nuevos sistemas estructurales de protección frente a sismos. En este ámbito, se ha desarrollado recientemente en la Universitat Politècnica de València un tipo de unión estructural para la protección frente a sismos basada en el empleo de aleaciones con memoria de forma (SMA) como sustitutas de las convencionales armaduras de acero longitudinales en las uniones entre elementos de hormigón armado. Éstas confieren a la unión unas características mecánicas muy superiores a las de las armaduras convencionales. La finalidad de este nuevo tipo de uniones es sustituir aquellas uniones de las estructuras en las que se requiera una ductilidad elevada. Mientras que para un sismo de proyecto las uniones con materiales convencionales resultarían suficientemente dañadas como para requerir una gran reparación o sustitución de ciertos elementos, una estructura en la que las uniones son sustituidas por esta nueva unión y que sufre el mismo sismo no presentaría los problemas propios del fallo de la armadura de acero. Se tendría posiblemente una rotura del hormigón en la unión, pero el SMA se mantendría en buen estado. Para que la estructura pudiera ser puesta en servicio de nuevo sería necesaria únicamente una reparación menor. En este marco se desarrolla la investigación del presente Trabajo Final de Máster, en el que se pretende estudiar la correcta reparación de este tipo de uniones para que puedan volver a presentar un correcto funcionamiento tras la ocurrencia de un sismo, empleando los menores recursos posibles. Con ese objetivo, se estudia el refuerzo de estructuras mediante su envoltura con polímeros reforzados con fibras (FRP). Para verificar su aplicabilidad a la reparación de uniones con SMA se lleva a cabo un estudio teórico de cómo se comportan las estructuras con FRP y un estudio experimental para determinar el correcto funcionamiento de las uniones con SMA reparadas con FRP. Para realizar la primera tarea, se hace una revisión exhaustiva del estado del arte en materia de FRP, del cual extraer conclusiones en cuanto a su diseño y fabricación para posteriormente modelizar el comportamiento que tendría la unión objeto de estudio. Para llevar a cabo el estudio experimental se desarrolla una campaña de ensayos que representen las condiciones de funcionamiento de las uniones de hormigón armado ante una solicitación sísmica. Una vez analizados los resultados experimentales y validado el modelo numérico propuesto, se realiza una aplicación práctica de las uniones investigadas con el fin de estudiar el impacto global en costes a largo plazo de este tipo de estructuras desarrolladas con materiales no convencionales y estudiar su viabilidad socioeconómica.Rueda García, L. (2017). Estudio de uniones de hormigón armado con barras de aleación con memoria de forma reparadas con CFRP y sometidas a carga cíclica. Parte I: Estudio Teórico. Aplicación práctica a un caso real de viaducto en zona de alta sismicidad en México. http://hdl.handle.net/10251/89619Archivo delegad

Behaviour of retrofited precast UHPC and Ni-Ti SMA column-to-foundation connection with CFRP wrapping layers

Four precast column-to-foundation connection specimens, previously tested under lateral reversed cyclic loading and constant axial load (first-stage tests), were repaired with Carbon Fibre Reinforced Polymer (CFRP) layers in the areas where plastic hinges had formed and were retested under the same loads (second-stage tests). The columns were originally manufactured with ultrahigh-performance concrete (UHPC) with high stee-fibre content (volumetric steel/fibre ratio 1.9%). The steel bars in the connection were replaced with superelastic Ni-Ti SMA bars that crossed the column/foundation interface. Two types of connection between the precast column and the foundation were analysed: protruding bars and smooth pocket bars (SP). The specimens were subjected to the same constant level of relative axial load in both the first and second-stage tests. The objective was to determine whether the initial performance of precast UHPC and SMA reinforced column-to-foundation connections against lateral cyclic loads can be restored after a seismic event by means of simple and economic retrofitting. The effectiveness of the number of strengthening CFRP layers was also studied (two or three CFRP wrapping layers) for each column-to-foundation connection type. The main results for PB and SP connection specimens with respect to the original specimens were respectively: an average strength capacity loss of 8% and 19%, displacement ductility increase of 8% and 42%, dissipated energy 48% and 53% higher and initial stiffness 9.5% and 21% lower. No significant differences were observed in the repairs done with two or three CFRP wrapping layers.The authors wish to thank the Spanish Ministry of Science and Innovation for the support provided through Projects BIA2012-32645 and RTI2018-099091-B-C21-AR, and Grant BES-2016-078010 from the European Union for the financial support with FEDER funds, and the Spanish Ministry of Education, Culture and Sport for Grant FPU12/01451

Behaviour of retrofited precast UHPC and Ni-Ti SMA column-to-foundation connection with CFRP wrapping layers

[EN] Four precast column-to-foundation connection specimens, previously tested under lateral reversed cyclic loading and constant axial load (first-stage tests), were repaired with Carbon Fibre Reinforced Polymer (CFRP) layers in the areas where plastic hinges had formed and were retested under the same loads (second-stage tests). The columns were originally manufactured with ultrahigh-performance concrete (UHPC) with high stee-fibre content (volumetric steel/fibre ratio 1.9%). The steel bars in the connection were replaced with superelastic Ni-Ti SMA bars that crossed the column/foundation interface. Two types of connection between the precast column and the foundation were analysed: protruding bars and smooth pocket bars (SP). The specimens were subjected to the same constant level of relative axial load in both the first and second-stage tests. The objective was to determine whether the initial performance of precast UHPC and SMA reinforced column-to-foundation connections against lateral cyclic loads can be restored after a seismic event by means of simple and economic retrofitting. The effectiveness of the number of strengthening CFRP layers was also studied (two or three CFRP wrapping layers) for each column-to-foundation connection type. The main results for PB and SP connection specimens with respect to the original specimens were respectively: an average strength capacity loss of 8% and 19%, displacement ductility increase of 8% and 42%, dissipated energy 48% and 53% higher and initial stiffness 9.5% and 21% lower. No significant differences were observed in the repairs done with two or three CFRP wrapping layers.This paper forms part of a line of research carried out at the University Institute of Concrete Science and Technology (ICITECH) of the Universitat Politecnica de Valencia. The authors wish to thank the Spanish Ministry of Science and Innovation for the support provided through Projects BIA2012-32645 and RTI2018-099091-B-C21-AR, and Grant BES-2016-078010 from the European Union for the financial support with FEDER funds, and the Spanish Ministry of Education, Culture and Sport for Grant FPU12/01451.Pereiro-Barceló, J.; Bonet Senach, JL.; Rueda-García, L.; Ciurana-Tatay, Á. (2022). Behaviour of retrofited precast UHPC and Ni-Ti SMA column-to-foundation connection with CFRP wrapping layers. Construction and Building Materials. 323:1-17. https://doi.org/10.1016/j.conbuildmat.2022.12653611732

Cyclic response of precast column-to-foundation connection using uhpc and Ni–Ti SMA reinforcements in columns

Earthquakes are catastrophic natural events with a special impact on reinforced concrete structures due to the horizontal loads that they introduce into structures. To adequately resist an earthquake, a precast structure must have a high deformation capacity, dissipate energy in each earthquake cycle, undergo less damage and fewer residual deformations. To achieve all this, the behaviour of precast columns made with UPHC was herein experimentally analysed. Steel rebars were replaced with Nisingle bondTi shape memory alloy (SMA) bars with superelasticity (SE) in the critical zone of the column-to-foundation connection. The Nisingle bondTi SMA bars crossed the interface between the column and foundation. Two types of connection with the foundation were studied: smooth pocket type and protruding bar type. Columns were subjected to constant compression and a cyclic lateral load. Rocking behaviour was observed at the connection critical section. The use of advanced materials allowed a moment-rotation behaviour of the connection to be developed without any significant damage. Low residual deformations were observed while testing because of both the damage in UHPC was low and the superelasticity of the Nisingle bondTi SMA bars.This paper forms part of a research line carried out at the Institute of Concrete Science and Technology (ICITECH) of the Universitat Politècnica de València. The authors wish to thank to the Government of Spain Ministry of Economy and Competitiveness for the support it provided through Project BIA2012-32645, to the Government of Spain Ministry of Science and Innovation for the project RTI2018-099091-B-C21-AR, and the grant BES-2016-078010, to the European Union for the financial support with FEDER funds and to the Government of Spain Ministry of Education, Culture and Sports for grant FPU12/01451

Analysis of the shear strength mechanism of slender precast concrete beams with cast-in-place slab and web reinforcement

[EN] Precast concrete beams with cast-in-place slabs on top, namely concrete composite beams are frequently used for building concrete bridge decks. In designs, the contribution of cast-in-place slabs to shear strength tends to be omitted. However, given the vast number of existent bridges with this deck typology, significant cost savings could be made when assessing these structures if the slab's shear strength is considered. This paper analyses how cast-in-place slab influences the shear behaviour of concrete composite beams with web reinforcement. For this purpose, an experimental programme of 18 concrete specimens with web reinforcement and rectangular crosssections was run, in which the following parameters varied: cross-sectional depth; existence of an interface between concretes; compressive strengths of the concrete of beams and slabs; differential shrinkage between concretes. It was observed that: the slab contributed to resist shear; the existence of an interface between concretes led to a crack appearing along it that caused the transmitted shear to be divided into two load paths: one through the precast beam and another one through the slab; the slab's concrete strength was that which mainly influenced the element's shear strength; differential shrinkage did not reduce shear strength. Based on experimental observations, a mechanical model is proposed in this paper to assess the composite elements' shear strength, which considers the yielding of both stirrups and the slab's longitudinal reinforcement to be a failure criterion, which well predicted the experimental results. The shear formulations of Eurocode 2, the Level III Approximation of Model Code 2010 and the (b) Formula of ACI 318-19 offered a similar result to the herein proposed method when using the entire composite element effective depth and the weighted average of the concrete strengths of both the beam and slab estimated from the area ratio. Codes significantly underestimated specimens' interface shear.The experimental programme of this research work was undertaken at the Concrete Science and Technology University Institute (ICITECH) of the Universitat Politecnica de Valencia (UPV; Spain) with concrete supplied by Caplansa. The project was supported by the Spanish Min-istry of Science and Innovation through Projects BIA2015-64672-C4-4-R and RTI2018-099091-B-C21-AR; the Regional Government of Valencia through Project AICO/2018/250; the European Union with FEDER funds. The authors thank the Spanish Ministry of Economy and Business for Grant BES-2016-078010 that supported Lisbel Rueda-Garcia.Rueda-García, L.; Bonet Senach, JL.; Miguel Sosa, P.; Fernández Prada, MÁ. (2021). Analysis of the shear strength mechanism of slender precast concrete beams with cast-in-place slab and web reinforcement. Engineering Structures. 246:1-18. https://doi.org/10.1016/j.engstruct.2021.113043S11824

Experimental analysis of the shear strength of composite concrete beams without web reinforcement

[EN] Composite concrete members without web reinforcement are often used in precast construction. The contribution of the cast-in-place concrete topping slab to vertical shear strength has been traditionally disregarded. However, significant cost savings can result from designing and assessing these structures if this contribution is considered. This paper presents the experimental study of a series of 21 monolithic and composite (precast beam and cast-in-place slab) specimens without web reinforcement, and with rectangular and T-shaped cross-sections, failing in shear. The vertical shear strength was analysed by the following test variables: cross-section shape, the existence of an interface between different aged concretes, strengths of the two concretes and the differential shrinkage effect. From these experimental tests, it was concluded that the slab contributed to shear strength, the use of high-strength concrete slightly increased specimens' shear strength and the differential shrinkage did not reduce shear strength. Specimens' failure modes were analysed based on their shear transfer mechanisms, noticing that the arching action in the slab was considerable after critical shear crack formation. The vertical shear strength experimental results were well predicted by the codes' formulations (Eurocode 2, Model Code 2010 and ACI 318-19) when composite beam depth was taken for the calculations instead of beam depth. Codes significantly underestimated the horizontal shear strengths of the composite specimens.This research has been supported by: the Spanish Ministry of Science and Innovation through Research Project BIA2015-64672-C4-4-R and RTI2018-099091-B-C21-AR; the Regional Government of Valencia through Project AICO/2018/250; the European Union with FEDER funds. The experimental programme was developed in the Laboratory of Concrete of the Institute of Concrete Science and Technology (ICITECH) of the Universitat Politècnica de València (UPV) with concrete supplied by Caplansa. The Spanish Ministry of Science and Innovation supported Lisbel Rueda through grant BES-2016-078010.Rueda-García, L.; Bonet Senach, JL.; Miguel Sosa, P.; Fernández Prada, MÁ. (2021). Experimental analysis of the shear strength of composite concrete beams without web reinforcement. Engineering Structures. 229:1-17. https://doi.org/10.1016/j.engstruct.2020.111664S117229Ribas González, C. R., & Fernández Ruiz, M. (2017). Influence of flanges on the shear-carrying capacity of reinforced concrete beams without web reinforcement. Structural Concrete, 18(5), 720-732. doi:10.1002/suco.201600172Loov, R. E., & Patnaik, A. K. (1994). Horizontal Shear Strength of Composite Concrete Beams With a Rough Interface. 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