Collaborative workshop: sustainable civil engineering proposals for real settings

The objective is to familiarize students with real civil engineering problems as posed by social agents (e.g. a city council, a neighbourhood association, etc.) and to foster social responsibility, active and cooperative learning, teamwork and sustainability. A multidisciplinary team accompanies students in finding solutions to problems affecting a region, with the goal of training them in how to sensitively deal with complex urban realities and understand the possible impacts and conflicts of their projects for their region and society. Methodologically, this training strategy is based on active teamwork and cooperation applied to a real case. It is also influenced by service learning in that local stakeholders explain their problems to the students and ask for solutions. This initiative is not part of any study plan but is a complementary teaching activity organized by the Civil Engineering School of Barcelona and worth 3 ECTS for participating students. In 2016-2017, the workshop —covering problems related to harbour design, water quality, pedestrian bridges and retaining walls— as conducted in Marina d’Empuriabrava on the Costa Brava, proving to be a very satisfactory experience for students, teachers and local stakeholders in terms of learning and proposals. In 2017-2018 the workshop has been held in El Vendrell (Tarragona). In the next, editions, it is planned to make ongoing improvements in terms of time organization and teamwork evaluation.Postprint (published version

Taller col·laboratiu per acostar els estudiants de l´àmbit d'enginyeria civil i ambiental a problemàtiques reals

L'objectiu és acostar l'estudiantat a problemes reals de l'enginyeria civil a proposta d'un agent del territori per fomentar les competències de treball en equip, la sostenibilitat i el compromís social. Per això, s'ha dissenyat un taller basat en l'aprenentatge actiu i cooperatiu, on un equip multidisciplinar acompanya als estudiants per trobar solucions a les qüestions plantejades des del territori. El curs anterior es va fer a Empuriabrava i enguany s’ha portat a terme a El Vendrell amb una valoració positiva per part de tots els estudiants.Postprint (published version

Armadura de polímeros reforzados con fibras (PRF) para estructuras de hormigón en la nueva versión del Eurocódigo 2

The new version of Eurocode 2 will include for the first time an informative annex, Annex R “Embedded FRP reinforcement”, to design reinforced concrete structures with fibre reinforced polymer (FRP) reinforcement. FRP embedded reinforcement has some advantages such as their low susceptibility to corrosion, high-strength, and low life-cycle cost. FRP rebars can be used as longitudinal or transverse reinforcement in a similar way than conventional steel rebars. However, in the design of FRP reinforced concrete structures, some particular aspects related to the reinforcement properties must be taken into account, among which it is worth highlighting their linear elastic behaviour until failure, their relatively low modulus of elasticity or their behaviour under sustained stresses. Since, the content of Annex R is new, a summary and background related to all aspects required for designing with FRP reinforcement are given in this paper.The authors acknowledge the support provided by Spanish Ministry of Science and Innovation (MCIN/  AEI)  and  by  the  European  Funds  for  Regional  Development  in  the  following  projects  during their collaboration in the TN140/SC2 and in the CEN/TC250/SC2/WG1/TG1 (Eva Oller): BIA2015‐64672‐C4‐1‐R, RTI2018‐097314‐B‐C21, and PID2020‐119015GB‐C22.Peer ReviewedPostprint (published version

Contribution of externally bonded FRP shear reinforcement to the shear strength of RC beams

An experimental program of T-beams strengthened in shear by CFRP sheets has been developed with two longitudinal reinforcement ratios and different externally bonded CFRP shear strengthening amounts in a discontinuous or continuous U-shaped configuration with and without mechanical anchorages. The effectiveness of the external reinforcement without anchorages was low regardless the CFRP reinforcement ratio. There is an evidence of the interaction of the different shear strength components, concrete Vc, transverse steel Vs, CFRP sheets Vf that have been obtained from the registered data of the instrumentation. This interaction might explain that the ultimate shear force of some CFRP-strengthened beams was lower than the one of the control beam. There is a significant difference between the sum of the Vc, Vs, and Vf components and the total shear force. This difference is assumed to be carried out by the flange (including its internal transverse reinforcement), which represents a significant percentage of the total shear strength (with a mean value of 38%). Finally, the contribution of the CFRP has been obtained by different existing guidelines and has been compared to the experimental values.Peer ReviewedPostprint (author's final draft

Refuerzo de estructuras de hormigón armado con laminados de fibra de carbono (CFRP)

El uso de los materiales compuestos en el campo del refuerzo estructural ha experimentado un notable crecimiento en los últimos años gracias a sus elevadas relaciones resistencia/peso y rigidez/peso, que permiten reducir costes de mano de obra respecto al empleo de otros materiales más convencionales. Los polímeros reforzados con fibras (FRP) se pueden aplicar como refuerzo de estructuras de hormigón armado o pretensado a flexión, cortante o confinamiento. Independientemente del tipo de refuerzo, uno de los principales inconvenientes o condicionantes en el dimensionamiento es el fallo por el desprendimiento prematuro del refuerzo, antes de alcanzar la resistencia última del mismo, por la concentración de tensiones en la interfase entre el laminado y el soporte

Analysis of FRP shear strengthening solutions for reinforced concrete beams considering debonding failure

In this paper, a fiber beam model previously developed by the authors for the nonlinear analysis of strengthened elements, including the effects of shear, is used to predict the response of reinforced concrete (RC) beams strengthened in shear with fiber reinforced polymers (FRP) sheets. In the previous version of the model, debonding failure of FRP was not included; hence, its application was limited to the simulation of wrapped configurations. The model is now extended to account for debonding failure in order to allow for its application to beams strengthened with U-shaped and side-bonded configurations. Existing experimental tests on RC beams strengthened in shear by FRP sheets in both wrapped and U-shaped configurations were numerically simulated. The model reproduces, with reasonable accuracy, the experimental failure loads, the load-deflection behavior, and the strains in FRP and stirrups with increasing load. The advantages of this proposal are related with the simplicity and straightforwardness of the beam models to be applied in practical engineering problems.Peer ReviewedPostprint (author's final draft

Evaluación de la eficiencia de soluciones de refuerzo en estructuras de hormigón mediante análisis no lineal evolutivo

When designing a structural strengthening solution, the influence of the previous state of the structure on the capacity of the strengthened structure must be evaluated. In addition, strengthening interventions may involve operations such as partial unloading of the structure, placement and removal of temporary shores, application of loads or pre-deformations, restoring of damaged reinforcement or spalled con-crete or constraining of lateral strains. Therefore, changes in the cross-section geometry and reinforcement, longitudinal scheme, support conditions, loads and state of stresses and strains, may take place. Furthermore, occurrence of phenomena producing a premature failure or a change in the failure mode, should be avoided. In order to account for such a large variety of causes and phenomena affecting the structural response, a nonlinear and time-dependent analysis model of 3D reinforced and prestressed concrete frames, capable of capturing different failure modes and taking into account the structural history, is described. The model has been verified with tests on strengthened structures available in the literature and has been applied to an actually remodeled structure, comparing the advantages and disadvantages of two different strengthening proposals, showing its capabilities to assess the efficiency of structural strengthening systems.This paper is dedicated to the memory of an extraordinary engineer and human being, Luis Ortega Basagoiti, who was an example and reference for structural engineers and researchers along his professional career. The works described in this paper have been developed in the framework of the following research projects funded by the Spanish Science and Technology Ministries and by the European Funds for Regional Development, ADRESS (BIA2009-11764), REHABCAR (IPT-370000-2010-029), HORVITAL (BIA2015-64672-C4-1-R) and STRADURAVIUS (RTI2018-097314-B-C21).Peer ReviewedPostprint (published version

Refuerzo de estructuras existentes de hormigón con polímeros reforzados con fibras (PRF) en la nueva versión del Eurocódigo 2

This  paper  aims  to  introduce  the  content  of  Annex  J  “Strengthening  of  Existing  Concrete  Structures with CFRP” of Eurocode 2 [1]. This is first time that the design of adhesively bonded reinforcement  with  CFRP  has  been  introduced  in  the  European  regulations  through  an  informative annex. Annex J considers two different bonded strengthening techniques: externally bonded reinforcement (EBR) that consists of bonding CFRP strips or sheets to the surface of concrete elements, and near surface mounted reinforcement (NSM) that consists of embedded CFRP strips or rods to the slot cut in the concrete cover. Since, the content of Annex J is new, a summary  and  background  related  to  all  aspects  required  for  designing  CFRP  strengthened  systems for concrete structures, are given in this paper.The authors acknowledge the support provided by Spanish Ministry of Science and Innovation (MCIN/AEI) and by the European Funds for Regional Development in the following projects during their collaboration in the CTN140/SC2 and in the CEN/TC250/SC2/WG1/TG1 (Eva Oller): BIA2015‐64672‐C4‐1‐R, RTI2018‐097314‐B‐C21, and PID2020‐119015GB‐C22.Peer ReviewedPostprint (published version

Experimental investigation of the shear strength of one-way reinforced concrete (RC) slabs subjected to concentrated loads and in-plane transverse axial tension

This paper presents the results of an experimental campaign carried out to investigate the effects of in-plane transverse tensile forces on the shear strength of linearly supported one-way reinforced concrete (RC) slabs without shear reinforcement subjected to concentrated loads. A total of 5 half scale slabs (1650¿×¿1650¿×¿120¿mm), subjected simultaneously to different levels of in-plane tensile forces and a concentrated load were tested up to failure. The clear shear span to effective depth ratio av/d was equal to 3 in all tests, to minimize the effects of the direct transmission of the load to the closest support, the so called arching action. As observed, the shear strength barely decreases with increasing values of the tensile force applied, even for values of the external force that cracked the concrete cross-section of the slabs in the direction perpendicular to the span. These observations may indicate that the shear–flexural behavior in the spanning direction is not significantly affected by the membrane forces in the transverse direction.This work has been carried out within the framework of the research project BIA-2015-64672-C4-1-R, financed by the Ministry of Economy and Competitiveness (MINECO) of Spain, and with the invaluable help of the technicians and the director of the Laboratory of Technology of Structures and Materials of the Universitat Politècnica de Catalunya. The authors want also to thank Master students Pau Figueras and Laura Beltran who collaborated in the numerical predictions and execution of the tests, respectively.Peer ReviewedPostprint (published version

Límites de esbeltez basados en prestaciones para vigas de hormigón armado para el control de deformaciones y el control de tensiones en la armadura

Due to the complex deformational behavior of cracked RC members, an effective way to ensure the fulfilment of the SLS is to limit the slenderness ratio l/d of the element. In this study, the deformation slenderness limit concept is generalized to incorporate crack width limitations. The proposed slenderness limits are compared with those derived from non-linear time-dependent analysis and also with those obtained using the EC2 method of deflections interpolation. Very good approximation and low scatter has been obtained showing that the proposed slenderness limits are a useful tool for performance-based design of RC structures.The financial support provided by the Spanish Ministry of Economy and Competitiveness (MINECO) and the European Funds for Regional Development (FEDER), through the Research projects: BIA2015-64672-C4-1-R and BIA2017-84975-C2-2-P and through the Excellence network BIA2015-71484-REDTPostprint (published version