Static structural system identification for beam-like structures using compatibility conditions

This is the peer reviewed version of the following article: [Lei J, Xu D, Turmo J. Static structural system identification for beam-like structures using compatibility conditions. Struct Control Health Monit. 2018;25:e2062. https://doi.org/10.1002/stc.2062], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/stc.2062/full. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Due to the inevitable noise existing in the measured responses, structural system identification is often a challenging task in terms of the accuracy of the estimations. Structural system identification by the observability method, which is characterized by the analysis of null spaces, is a powerful tool to determine the observability of structural parameters. However, it did not cope well with measurement errors so far. In this paper, for the first time, functional relations among displacements, denoted by the term compatibility conditions, in beam-like structures are derived by the observability method. Then, compatibility conditions are imposed in an optimization procedure to minimize the discrepancy between the measured response and the compatible one. The compatible response obtained by the optimization is used to obtain the final estimations of the parameters. In a simply supported bridge example, the proposed method is thoroughly evaluated regarding the number of measurements, error levels, and load cases. In an example of a continuous bridge, different load cases are used to estimate the bending stiffnesses of different zones. The accuracy and the efficacy of the proposed method are verified by the numerical results.Peer ReviewedPostprint (author's final draft

Evaluation of the techniques to mitigate early shrinkage cracking through an image analysis methodology

This is the accepted version of the following article: [Ruiz-Ripoll, L., Barragán, B. E., Moro, S., and Turmo, J. (2016) Evaluation of the Techniques to Mitigate Early Shrinkage Cracking through an Image Analysis Methodology. Strain, 52: 492–502. doi: 10.1111/str.12191], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/str.12191/abstractNowadays, new products are introduced in concrete mixes to reduce the effects of shrinkage, which are the main reason of most of early age cracking phenomena, especially when curing is not performed in accordance to best practices. The lack of a standardized methodology to quantify concrete cracking complicates the determination of the effectiveness of different solutions and comparison between them. This research presents an evaluation through images of the suitability of fibres and shrinkage-reducing admixtures to control early shrinkage cracking in slab-type concrete elements. The use of this technique has permitted quantifying the typical cracking parameters objectively and analyse probabilistically the average crack width. Results show a delay and reduction of cracking after adding shrinkage-reducing admixtures and fibres in concrete, especially 1kgm-3 of polymeric microfibres. The incorporation of these components directly into the mix modified the behaviour of concrete, reducing shrinkage cracking from the beginning of moisture losses.Peer ReviewedPostprint (author's final draft

Solving some special cases of monomial ratio equations appearing frequently in physical and engineering problems

We first show that monomial ratio equations are not only very common in Physics and Engineering, but the natural type of equations in many practical problems. More precisely, in the case of models involving scale variables if the used formulas are not of this type they are not physically valid. The consequence is that when estimating the model parameters we are faced with systems of monomial ratio equations that are nonlinear and difficult to solve. In this paper, we provide an original algorithm to obtain the unique solutions of systems of equations made of linear combinations of monomial ratios whose coefficient matrix has a proper null space with low dimension that permits solving the problem in a simple way. Finally, we illustrate the proposed methods by their application to two practical problems from the hydraulic and structural fields.Peer ReviewedPostprint (published version

Analysis of measurement and simulation errors in structural system identification by observability techniques

This is the peer reviewed version of the following article: [Lei, J., Lozano-Galant, J. A., Nogal, M., Xu, D., and Turmo, J. (2017) Analysis of measurement and simulation errors in structural system identification by observability techniques. Struct. Control Health Monit., 24: . doi: 10.1002/stc.1923.], which has been published in final form at http://onlinelibrary.wiley.com/wol1/doi/10.1002/stc.1923/full. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.During the process of structural system identification, errors are unavoidable. This paper analyzes the effects of measurement and simulation errors in structural system identification based on observability techniques. To illustrate the symbolic approach of this method a simply supported beam is analyzed step-by-step. This analysis provides, for the very first time in the literature, the parametric equations of the estimated parameters. The effects of several factors, such as errors in a particular measurement or in the whole measurement set, load location, measurement location or sign of the errors, on the accuracy of the identification results are also investigated. It is found that error in a particular measurement increases the errors of individual estimations, and this effect can be significantly mitigated by introducing random errors in the whole measurement set. The propagation of simulation errors when using observability techniques is illustrated by two structures with different measurement sets and loading cases. A fluctuation of the observed parameters around the real values is proved to be a characteristic of this method. Also, it is suggested that a sufficient combination of different load cases should be utilized to avoid the inaccurate estimation at the location of low curvature zones.Peer ReviewedPostprint (author's final draft

Active learning for project management in civil engineering

Higher Educations studies in Spain were very much impacted by the Bologna Declaration. This was also so for the Civil Engineering curricula (Ingeniero de Caminos, Canales y Puertos). When the European Higher Education Area (EHEA) was launched to promote homogeneous Civil Engineering programs in all European countries, structure of the studies changed from a five-year program to a four-year bachelor program followed by a twoyear master. Not only duration, but also pedagogical methods were drastically transformed. The passive-learning professor-centred methods turn into active-learning student-centred ones. In this paper, the example of an elective subject for Project Management of Civil Infrastructure will be presented. In this subject, Project Based Learning is the basic learning method. Students, by groups, have to work on a real project of a big civil engineering infrastructure (airport terminal, railway line, highway line). To do so, all the documents from a real project under construction are provided. Students, by groups, have to follow all the steps leading to a successful completion of the works, from proposing an offer for the bid, to the health and safety, quality and environmental management; from the technical and economic planning of the site, to the management of the relation with the press. The presentation will address topics as various as the group motivation, the acquisition of soft skills, the learning methodology, the virtual visits to site, the interaction with BIM or the impact of the group size.Postprint (published version

Structural system identification by measurement error-minimizing observability method

This is the accepted version of the following article: [Lei, J, Lozano‐Galant, JA, Xu, D, Turmo, J. Structural system identification by measurement error‐minimizing observability method. Struct Control Health Monit. 2019; 26:e2425. https://doi.org/10.1002/stc.2425], which has been published in final form at https://doi.org/10.1002/stc.2425This paper proposes a method for the finite element model updating using static load tests under the framework of observability analysis. Previous works included measurement errors in the coefficient matrix of the observability equations. This impeded the obtainment of accurate estimations. To deal with this issue, the proposed method relocates the errors and incorporates an optimization procedure to minimize the square sum of these errors. This method is able to identify the structural parameters of complex structures where the axial and bending behaviors are coupled, such as inclined beams or frame structures. Its application is illustrated by three structures. First, the method was validated in a beam-like structure by comparing it with other methods in the literature. Then the effects of different factors were investigated in a multistory frame and a rigid frame bridge with inclined piers. These factors include the curvatures, the inclusion of rotation measurements, and the constraints on the range of unidentifiable parameters. The importance of rotation measurements is demonstrated in static structural system identification.Peer ReviewedPostprint (author's final draft

Resistencia de juntas secas conjugadas de puentes de dovelas prefabricadas de hormigón: propuesta para el Eurocódigo 2

Este trabajo presenta un estudio sobre el comportamiento de puentes de dovelas de hormigón con llaves de cortante, centrado en el comportamiento a cortante de las juntas secas conjugadas en Estado Límite Último. Se ha realizado una exhaustiva recopilación de la dispar formulación existente para evaluar la resistencia a cortante de las juntas. Se ha realizado, asimismo, una investigación bibliográfica de los resultados experimentales disponibles sobre este particular en la literatura. Los resultados recogidos en la bibliografía han sido comparados con la variada formulación existente para predecir la resistencia última de las juntas. La fórmula que mejor predice la resistencia ha sido identificada. Ésta ha sido adaptada al formato de seguridad presente en el Eurocódigo 2. This paper discusses a study on the performance of concretesegmental bridges with shear keys, focusing on theshear behaviour of castellated dry joints under ultimatelimit state conditions. The widely varying formulationused to evaluate joint shear strength were compiled,along with the experimental results published in the literatureon the subject. The various approaches were evaluatedby comparing their predictions of ultimate jointstrength to published empirical findings. The formulagiving the best prediction was adapted to the safety factorprovisions set out in Eurocode 2.Peer ReviewedPostprint (published version

Simplified calculation of shear rotations for first-order shear deformation theory in deep bridge beams

Nodal rotations are produced by bending and shear effects and bending rotations can be easily calculated using Euler–Bernoulli’s stiffness matrix method. Nevertheless, shear rotations are traditionally neglected, as their effects are practically negligible in most structures. This assumption might lead to significant errors in the simulation of the rotations in some structures, as well as the wrong identification of the mechanical properties in inverse analysis. Despite its important role, no other works studying the calculation of shear rotations in deep beams were found in the literature. To fill this gap, after illustrating the errors of commercial software regarding calculating the rotations in deep beams, this study proposed a simple and intuitive method to calculate shear rotations in both isostatic and statically redundant beams. The new method calculates the shear rotation for all segments separately and introduces the result to the total rotation of the structure. This method can be applied to find the shear rotation in a redundant structure as well. A parametric study was carried out to calculate slenderness ratios to determine in what structural systems the shear rotations can be neglected. In addition, the errors in the inverse analysis of deep beams were parametrically studied to determine the role of shear rotation in different structural systems. Finally, to validate the application of the method in actual structures, a construction stage of a composite bridge was analyzed.The authors are indebted to the projects PID2021-126405OB-C31 and PID2021-126405OB-C32 funded by FEDER funds—A Way to Make Europe and Spanish Ministry of Economy and Competitiveness MICIN/AEI/10.13039/501100011033/, BIA2017-86811-C2-1-R and BIA2017-86811-C2-2-R funded by FEDER funds.Peer ReviewedPostprint (published version

Comportamiento estructural de puentes de dovelas prefabricadas con pretensado exterior y junta seca. Segunda parte: modelización de ensayos

Este trabajo de investigación presenta la modelización por el método de los elementos finitos de una serie de ensayos de vigas de dovelas de hormigón con pretensado exterior y juntas secas conjugadas, centrándose en el estudio de la respuesta a solicitaciones de flexión y cortante combinados, en servicio y en rotura. Se han puesto a punto dos modelos de junta para estudiar la transmisión de cortante entre juntas conjugadas. Un modelo elaborado con elementos tipo junta a los que se les confiere un comportamiento de rozamiento coulombiano y que modeliza la junta (y sus llaves conjugadas) con su geometría. Otro modelo de junta plana que modeliza el comportamiento medio de la junta en la zona de llaves con elementos tipo junta dotados de un modelo de comportamiento de rozamiento cohesivo. Estos modelos de junta han sido calibrados y aplicados al estudio de los ensayos. De la aplicación de estos modelos se han extraído conclusiones referentes al modelo de análisis, al armado de las dovelas y al comportamiento global de este tipo de estructuras.Peer ReviewedPostprint (published version

Experiencias en innovación en la enseñanza de la Ingeniería Civil para adaptarse a los nuevos planes de estudio auspiciados por Bolonia

El principal objetivo de la ponencia es plantear la problemática asociada a la coexistencia de asignaturas de corte tradicional con asignaturas basadas en el aprendizaje por proyectos o asignaturas basadas en créditos ECTSs y presentar la transformación de la metodología docente desarrollada en asignaturas tradicionales para asegurarse de que los alumnos adquieren conocimientos suficientes para que la elaboración del proyecto sea una actividad formativa y no frustrante; y asegurarse además que estos conocimientos se adquieren con carácter previo a la elaboración de los proyectos.Postprint (published version