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UPCommons - E-prints UPC Universitat Politècnica de Catalunya (81,070 recursos)
E-prints UPC cobreix dues finalitats: per una banda, és el dipòsit institucional de la UPC que recull els articles de revista, les comunicacions de congrés i els reports de recerca generats en les activitats de recerca del personal docent i investigador de la universitat; per l'altra, és una eina que permet accelerar la producció científica, allotjant versions de documents prèvies a la publicació en una revista o a les actes d’un congrés.

Articles de revista

Mostrando recursos 1 - 20 de 189

1. Improved assessment of fibre content and orientation with inductive method in SFRC - Pialarissi Cavalaro, Sergio Henrique; López Carreño, Rubén-Daniel; Torrents Dolz, Josep M.; Aguado de Cea, Antonio
The inductive method is a robust and simple non-destructive test to assess the content and the distribution of steel fibres in FRC. Despite the advantages in comparison with other methods, further studies are still needed to define the accuracy, the theoretical basis and the equations for the conversion of the inductance into fibre content and distribution. In fact, although the test provides an indirect estimation of the fibre distribution, currently no equation exists for the assessment of the orientation number, which is a valuable parameter for the design of structures. The objective of the present paper is to address this...

2. Experimental study about the effects of granular skeleton distribution on the mechanical properties of self-compacting concrete (SCC) - Santos, Ana C. P.; Ortiz Lozano, José Ángel; Villegas, Noe; Aguado de Cea, Antonio
In recent years, the use of self-compacting concrete (SCC) has been increasing. Although methods for designing the mixture proportions usually derive from experience with conventional concretes, some specific procedures still are not universally accepted. The design and characterization of SCC influences not only the mix components (paste volume and nature, binder amount and type, granular skeleton, etc.) but also the testing methods used to validate the self-compactability (usually in terms of rheology, fluidity, viscosity and resistance to segregation). This paper studies the influence on SCC mechanical properties based on the consideration of two types of granular skeleton, discontinuous and continuous,...

3. Influence of barite aggregate friability on mixing process and mechanical properties of concrete - González-Ortega, Martha Alejandra; Pialarissi Cavalaro, Sergio Henrique; Aguado de Cea, Antonio
The main objective of this paper is to evaluate the friability of the barite aggregate during the mixing process and its influence on the fresh and hardened properties of concrete. Three types of aggregates were studied: barite (in two states, dry and wet), limestone and EAF slag. A specific test was designed in which each type of aggregate was exposed to several times of mixing to evaluate possible changes to the grading curves and in the surface of the aggregates grains. Moreover, four types of concretes were designed (two with barite, one with EAF slag aggregate and one with conventional...

4. Experimental analysis of properties of high performance recycled aggregate concrete - Gonzàlez Corominas, Andreu; Etxeberria Larrañaga, Miren
Due to the increase in the demolition of high strength concrete structures and the interest of precast concrete companies in being more competitive, it is necessary to analyse the use of recycled concrete aggregates (RCA) in high performance concrete (HPC). In this study, HPC were produced using 20%, 50% and 100% of RCA on substitution of natural coarse aggregates. Three types of RCA were used, they were produced crushing original concrete of 100, 60 and 40 MPa of compressive strength. The physical, mechanical and durability properties of the recycled aggregates concretes and conventional concrete were analyzed. The results showed that...

5. Properties of high performance concrete made with recycled fine ceramic and coarse mixed aggregates - Gonzàlez Corominas, Andreu; Etxeberria Larrañaga, Miren
There are various means of obtaining waste for the production of recycled aggregates. In this study the waste material has been obtained from building demolition and also from the ceramic industry (known for the production of large amounts of rejected ceramic wastes). High performance concretes (HPC) was produced using fine ceramic aggregates (FCA) in substitution of 15% and 30% of natural sand, and using 20%, 50% and 100% of coarse mixed aggregates (CMA) on substitution of natural coarse aggregates. The physical, mechanical and durability properties of the recycled aggregate concretes were determined and compared to those of the results of...

6. Residue strength, water absorption and pore size distributions of recycled aggregate concrete after exposure to elevated temperatures - Kou, Shi-Cong; Poon, Chi-Sun; Etxeberria Larrañaga, Miren
In this paper, the effects of high temperature exposure of recycled aggregate concretes in terms of residual strengths, capillary water absorption capacity and pore size distribution are discussed. Two mineral admixtures, fly ash (FA) and ground granulated blast furnace (GGBS) were used in the experiment to partially replace ordinary Portland cement for concrete production. The water to cementitious materials ratio was maintained at 0.50 for all the concrete mixes. The replacement levels of natural aggregates by recycled aggregates were at 0%, 50% and 100%. The concretes were exposed separately to 300 °C, 500 °C and 800 °C, and the compressive...

7. Shear design of reinforced concrete beams with FRP longitudinal and transverse reinforcement - Oller Ibars, Eva; Marí Bernat, Antonio Ricardo; Bairán García, Jesús Miguel; Cladera Bohigas, Antoni
The shear resisting mechanisms of reinforced concrete (RC) beams with longitudinal and transverse FRP reinforcement can be affected by the mechanical properties of the FRP rebars. This paper presents a mechanical model for the prediction of the shear strength of FRP RC beams that takes into account its particularities. The model assumes that the shear force is taken by the un-cracked concrete chord, by the residual tensile stresses along the crack length and by the FRP stirrups. Failure is considered to occur when the principal tensile stress at the concrete chord reaches the concrete tensile strength, assuming that the contribution...

8. Shear-flexural strength mechanical model for the design and assessment of reinforced concrete beams subjected to point or distributed loads - Marí Bernat, Antonio Ricardo; Cladera Bohigas, Antoni; Bairán García, Jesús Miguel; Oller Ibars, Eva; Ribas, Carlos
A mechanical model recently developed for the shear strength of slender reinforced concrete beams with and without shear reinforcement is presented and extended to elements with uniformly distributed loads, specially focusing on practical design and assessment in this paper. The shear strength is considered to be the sum of the shear transferred by the concrete compression chord, along the crack, due to residual tensile and frictional stresses, by the stirrups and, if they exist, by the longitudinal reinforcement. Based on the principles of structural mechanics simple expressions have been derived separately for each shear transfer action and for their interaction...

9. An algorithm for simulation of concrete cable-stayed bridges built on temporary supports and considering time dependent effects - Lozano Galant, Jose Antono; Turmo Coderque, José
The time-dependent phenomena effects might play an important role in the structural behavior of a cable-stayed bridge during construction and in service. In fact, because of these effects the target state of stresses (Objective Service Stage, OSS) can only be achieved at a certain target time. In the literature, a number of software have been presented to study creep and shrinkage effects during cantilever erection of cable-stayed bridges. Nevertheless, the effects of these phenomena in the alternative erection technique, the temporary support erection method, have received little attention. Furthermore, none of the presented software are able to: (1) Define a...

10. Creep and shrinkage effects in service stresses of concrete cable-stayed bridges - Lozano Galant, Jose Antono; Turmo Coderque, José
Most of the methods presented in the literature to define the target service stresses (Objective Service Stage, OSS) of cable-stayed bridges rarely include the time-dependent phenomena effects. Nevertheless, especially in concrete structures, this assumption might be on the unsafe side because time-dependent phenomena usually modify service stresses. To fill this gap, this paper studies the time-dependent phenomena effects into service stresses of concrete cable-stayed bridges. After illustrating the important role of these phenomena in an asymmetrical cable-stayed bridge without backstay, a new method to include their effects into the OSS is presented. An important issue to be considered in this...

11. Modification of the stress-state of cable-stayed bridge due to staggered erection of their superstructure - Lozano Galant, Jose Antono; Ruiz Ripoll, Lidia; Payá Zaforteza, Ignacio Javier; Turmo Coderque, José
In current practice, the effects of the evolutionary erection of cable-stayed bridge superstructure are rarely included into the simulation of its tensioning process. In fact, stay forces in service are usually defined in early stages of design, when the construction process has not even been conceived in detail yet. In order to fill this gap, the effects of the evolutionary erection of cable-stayed bridge superstructure throughout the tensioning process are studied in this paper. This study is focused on steel cable-stayed bridges erected on temporary supports. For the very first time a new criterion to include the effects of the...

12. Structural system identification of cable-stayed bridges with observability techniques - Lozano Galant, Jose Antono; Nogal Macho, María; Payá Zaforteza, Ignacio Javier; Turmo Coderque, José
Cable-stayed bridges are highly statically redundant, light and flexible structures. This complexity highlights the role of the structural system identification (SSI) method in the calibration of the actual properties of the simplified models of these structures. This study proposes the first application of observability techniques to SSI of cable-stayed bridges. This method enables to define which subset of actual structural variables should be measured on site to identify mechanical properties, such as Young's modulus, area and inertia, or stiffnesses (EA and EI) of deck, pylon and stay cables. The effects of the inclination and inertia of the stay cables and...

13. Efficient 1D model for blind assessment of existing bridges : simulation of a full scale loading test and comparison with higher order continuum models - Santos Ferreira, Denise Carina; Bairán García, Jesús Miguel; Marí Bernat, Antonio Ricardo
Assessing the structural performance of existing concrete bridges is nowadays a major task. Nonlinear finite element (FE) analysis can quantify their capacity, evaluate strengthening interventions and prevent premature dismantle. However, this technique, mainly performed with 2D/3D FE, is seldom used at true scale due to the great complexity and computational costs involved. In this paper, the loading test of a strengthened concrete bridge in Sweden (Örnsköldsvik) is simulated using a 1D model. The bridge failed in combination of shear–bending–torsion triggered by fibre-reinforced polymer bond failure. Consecutive levels of refinement of the 1D model are presented and available results from higher...

14. The bridges of the future or the future of bridges? - Casas Rius, Joan Ramon
Postprint (author’s final draft)

15. External sulfate attack in dam concretes with thaumasite formation - Chinchón Payá, S.; Aguado de Cea, Antonio; Nugteren, H. W; Chinchón Yepes, Jose Servando
Concrete core samples extracted from different areas of the Mequinenza Dam (Spain) have been studied and expansive reactions affecting the structure were not found. However, expansive reactions in the concrete of certain parts located near the abutments of two galleries have been observed as a consequence of an external sulfate attack due to the sulfur compounds contained in the lignites that are present on the surrounding terrain. Secondary gypsum, ettringite, and thaumasite, as well as several sulfate efflorescence have been detected. The thaumasite formed in the degraded concrete is related to a Thaumasite Sulfate Attack (TSA). Scanning Electron Microscopy (SEM)...

16. Safety factors for CFRP strengthening in bending of reinforced concrete bridges - Trentin, Caterina; Casas Rius, Joan Ramon
Concerning the strengthening in bending of reinforced concrete bridge decks, the use of fiber reinforced polymers (FRP) has increased due to its easy application and excellent mechanical and chemical properties. However, due to the lack of codes and standards and the lack of experience in the long term behavior, uncertainties exist in the calculation bases along the dimensioning of this reinforcement and more precisely in the partial coefficients of safety to be adopted for the material properties. As a consequence, bridge engineers are reluctant to use composite materials in the strengthening of damaged reinforced concrete bridge decks. To try to...

17. Passive and hybrid mitigation of potential near-fault inner pounding of a self-braking seismic isolator - Abdel Kareem Moustafa, Mohamed Ismail; Rodellar Benedé, José; Pozo Montero, Francesc
A seismic isolated structure is usually a long-period structural system, which may encounter a low-frequency resonance problem when subjected to a near-fault earthquake that usually has a long-period pulse-like waveform. This long-period wave component may result in an enlargement of the base displacement and a decrease of the isolation efficiency. To overcome this problem, a rolling-based seismic isolator, referred to as roll-n-cage (RNC) isolator, has been recently proposed. The RNC isolator has a built-in buffer (braking) mechanism that limits the peak isolator displacements under severe earthquakes and prevents adjacent structural pounding. This paper addresses the problem of passive and hybrid...

18. Design of FRC tunnel segments considering the ductility requirements of the Model Code 2010 - Liao, Lin; Fuente Antequera, Albert de la; Pialarissi Cavalaro, Sergio Henrique; Aguado de Cea, Antonio
Fibre reinforced concrete (FRC) is used to improve the mechanical response of precast segments for tunnels. The structural use of the material has been regulated by national codes and, recently, by the Model Code 2010 (MC 2010, hereinafter). In this regard, it is necessary to update the philosophy applied to the design of tunnel segments in compliance with the most recent guidelines, evaluating their applicability and repercussion. The objective of this paper is to present a critical analysis of the design of FRC segments according to the ductility requirements from the MC 2010; an alternative approach is proposed that is...

19. Efficient preliminary floating offshore wind turbine design and testing methodologies and application to a concrete spar design - Matha, Denis; Sandner, Frank; Molins i Borrell, Climent; Campos Hortigüela, Alexis; Cheng, Po Wen
The current key challenge in the floating offshore wind turbine industry and research is on designing economic floating systems that can compete with fixed-bottom offshore turbines in terms of levelized cost of energy. The preliminary platform design, as well as early experimental design assessments, are critical elements in the overall design process. In this contribution, a brief review of current floating offshore wind turbine platform pre-design and scaled testing methodologies is provided, with a focus on their ability to accommodate the coupled dynamic behaviour of floating offshore wind systems. The exemplary design and testing methodology for a monolithic concrete spar...

20. Pull-out of textile reinforcement in concrete - Williams Portal, Natalie; Fernández Pérez, Ignasi; Nyholm Thrane, Lars; Lundgren, Karin
Textile Reinforced Concrete (TRC) has emerged as a promising novel alternative offering corrosion resistance and both thinner and light-weight structures. Although TRC has been extensively researched, the formalization of experimental methods and design standards is still in progress. The aim of this work was to extract local-bond behaviour from pull-out tests of basalt and carbon TRC and utilize these in both simple (1D) and advanced models (3D) to yield the global structural behaviour. The simulation results from the 1D and 3D models are able to simulate the complex behaviour of TRC with a reasonable level of correlation. (C) 2014 Elsevier...

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