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One of the most effective ways to encourage the use of new approaches like BIM consists on applying Project Based Learning (PBL). According to this methodology, teams might gain knowledge and skills by solving a realistic challenge, that is to say, they learn by doing. In this way, team members can experiment and investigate by themselves. BIM contests stands as one of the most encouraging PBL activities. This format has the additional advantage that all teamOne of the most effective ways to encourage the use of new approaches like BIM consists on applying Project Based Learning (PBL). According to this methodology, teams might gain knowledge and skills by solving a realistic challenge, that is to say, they learn by doing. In this way, team members can experiment and investigate by themselves. BIM contests stands as one of the most encouraging PBL activities. This format has the additional advantage that all teams work on the same problem, what eases the comparison of the results. In this sense, the analysis of the proposed Building Execution Plan (BEPs) provides useful insights about the know-how of the different designs. Despite the interest and usefullness of these results, no comparisons of similar BIM work flows have been carried out. To solve this gap, this paper analyzes, for the first time, the BEPs of the BIM projects presented in the different calls of the international contest BIM Valladolid. This analysis provides a useful insight about the most common software in each discipline. The evolution of the software of teams throughout time, as well as the information flows between the modeling and the structural analysis software of the proposals are also presenteds work on the same problem, what eases the comparison of the results. In this sense, the analysis of the proposed Building Execution Plan (BEPs) provides useful insights about the know-how of the different designs. Despite the interest and usefullness of these results, no comparisons of similar BIM work flows have been carried out. To solve this gap, this paper analyzes, for the first time, the BEPs of the BIM projects presented in the different calls of the international contest BIM Valladolid. This analysis provides a useful insight about the most common software in each discipline. The evolution of the software of teams throughout time, as well as the information flows between the modeling and the structural analysis software of the proposals are also presented

Arduino-based accelerometers are receiving wide attention from researchers to make long-term Structural Health Monitoring (SHM) feasible for structures with a low SHM budget. The current low-cost solutions found in the literature share some of the following drawbacks: (1) high noise density, (2) lack of wireless synchronization, (3) lack of automatic data acquisition and data management, and (4) lack of dedicated field tests aiming to compare mode shapes from Operational Modal Analysis (OMA) with those of a digital model. To solve these problems, a recently built short-span footbridge in Barcelona is instrumented using four Low-cost Adaptable Reliable Accelerometers (LARA). In this study, the automatization of the data acquisition and management of these low-cost solutions is studied for the first time in the literature. In addition, a digital model of the bridge under study is generated in SAP2000 using the available drawings and reported characteristics of its materials. The OMA of the bridge is calculated using Frequency Domain Decomposition (FDD) and Covariance Stochastic Subspace Identification (SSI-cov) methods. Using the Modal Assurance Criterion (MAC), the mode shapes of OMA are compared with those of the digital model. Finally, the acquired eigenfrequencies of the bridge obtained with a high-precision commercial sensor (HI-INC) showed a good agreement with those obtained with LARA. 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/. It is also to be noted that funding for this research has been provided for Seyedmilad Komarizadehasl by Spanish Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant (PRE2018-083238).

Collecting the information of traffic load, especially heavy trucks, is crucial for bridge statistical analysis, safety evaluation, and maintenance strategies. This paper presents a traffic sensing methodology that combines a deep learning based computer vision technique with the influence line theory. Theoretical background and derivations are introduced from both aspects of structural analysis and computer vision techniques. In addition, to evaluate the effectiveness and accuracy of the proposed traffic sensing method through field tests, a systematic analysis is performed on a continuous box-girder bridge. The obtained results show that the proposed method can automatically identify the vehicle load and speed with promising efficiency and accuracy and most importantly cost-effectiveness. All these features make the proposed methodology a desirable bridge weigh-in-motion system, especially for bridges already equipped with structural health monitoring system.

Nowadays, engineers are widely using accelerometers to record the vibration of structures for structural verification purposes. The main obstacle for using these data acquisition systems is their high cost, which limits its use to unique structures with a relatively high structural health monitoring budget. In this paper, a Cost Hyper-Efficient Arduino Product (CHEAP) has been developed to accurately measure structural accelerations. CHEAP is a system that is composed of five low-cost accelerometers that are connected to an Arduino microcontroller as their data acquisition system. Test results show that CHEAP not only has a significantly lower price (14 times cheaper in the worst-case scenario) compared with other systems used for comparison but also shows better accuracy on low frequencies for low acceleration amplitudes. Moreover, the final output results of Fast Fourier Transformation (FFT) assessments showed a better observable resolution for CHEAP than the studied control systems. This research was funded by the Spanish Ministry of Economy and Competitiveness, grant number BIA2017-86811-C2-1-R; the Spanish Ministry of Economy and Competitiveness, grant number BIA2017-86811-C2-2-R; the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya, Catalunya, Spain, grant number 2017 SGR 1482; Spanish Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant, grant number PRE2018-083238; Shanghai Qizhi Institute, grant number SYXF0120020109.

This article presents the application of the problem-based learning (PBL) methodology for introducing the civil engineering task of bridge design and construction to high school students wi...

La metodología Building Information Modelling (BIM) está revolucionando la manera en la que se desarrollan los proyectos de ingeniería civil. Una de las muchas ventajas de esta metodología es el desarrollo de modelos 3D, los cuales pueden ser conectados con herramientas de realidad aumentada. Entre las múltiples ventajas de la aplicación de esta tecnología en el campo de la ingeniería civil, resalta la accesibilidad de obtención de un gran nivel de detalle e información de un determinado elemento, facilitando la visualización y comprensión para todos los agentes. Hoy en día, esta tecnología está consolidada en sectores como el turismo o los video juegos, y cada vez está siendo más popular en estudios de arquitectura o inmobiliarias. Sin embargo, la realidad aumentada es una tecnología en desarrollo, y por ahora sus aplicaciones en la ingeniería civil son relativamente escasas. El objetivo del presente artículo es ilustrar el estado actual de la aplicación de BIM y de realidad aumentada en la ingeniería civil. Con tal objetivo, se analizarán los softwares más representativos de realidad aumentada y se analizará su aplicación en un puente elaborado con BIM. Tras este análisis, se obtendrán conclusiones sobre la interoperabilidad entre ambos. Por último, se expondrán las ventajas e inconvenientes encontrados para la aplicación de realidad aumentada en el campo de la ingeniería civil.

The use of Building Information Modelling (BIM) is getting more and more popular since governments worldwide are increasing the demand of this methodology as a requirement in their projects. One of the most encouraging ways to promote the use of this methodology is based on the so-called BIM contests, where practitioners are challenged to build a virtual model of a structure collaboratively. These challenges are usually designed to take the participants out of their comfort zone and to encourage them to experiment in the use of the latest software and collaborative software connections. Unlike other activities encouraging BIM, these contests have the additional advantage of easing the comparison in terms of software, exchange file formats and information flows as all the proposals are framed into a common project with the same working time. Despite the interest of this kind of comparative analyses, no studies of the results of BIM contest proposals can be found in the literature. To fill this gap, this paper analyses the summary reports of the different proposals submitted in three editions (2014, 2015 and 2016) of the BIM Valladolid contest in Spain. The results of this study provide usefull insights into the use of software in a number of disciplines (Architecture, Structural Analysis, Energy Efficiency, Measurements and Budget, Facilities, Planning Execution and Coordination) and the most common file exchange formats. The evolution of teams in software use throughout the different contest editions as well as the information flow among the Architecture and the Structural Analysis disciplines are also analyzed.

Resumen En la mayoria de vigas mixtas, la conexion entre el hormigon y el acero es imperfecta y, por tanto, aparece un mayor o menor deslizamiento relativo entre ambos materiales. Este deslizamiento afecta tanto a las deformaciones como a los esfuerzos de la viga. Para simular este fenomeno, en este trabajo se propone un nuevo modelo de elementos finitos bidimensional basado en elementos tipo viga, facilitando asi la interpretacion y la aplicacion practica de los resultados. Para validar la precision del modelo, se comparan los resultados obtenidos mediante el modelo con los derivados de las ecuaciones analiticas propuestas en la literatura, en dos estructuras mixtas con diferentes estados de carga.

Despite its importance in some structures, shear deformation is systematically neglected by most static structural system identification methods. This paper analyzes for the first time in the literature the effect of this deformation in the static inverse analysis of thin web bridges. This study is focused on the observability techniques. The most recent formulation found in the literature is based onthe Euler-Bernoulli beam theory. This formulation is unable to identify correctly the characteristics of a structure (such as flexural stiffness) when shear deformation is not negligible. To solve this problem, the observability method is updated according to Timoshenko's beam theory. This formulation uses an algebraic method which combines a symbolical and a numerical application. Thus, the updated observability formulation is able to obtain not only the flexural stiffness but also the shear one. Besides this, a parametric equation of the estimates is obtained for the first time in the literature. Some examples of growing complexity are used to illustrate the validity of the the proposed formulation formulation.

Traditionally, Spanish schools of civil engineering provide their students a class on “Technical English” in order to develop their language skills. However, this class does not cover all the skills that the student would need in the labor market and mainly focuses in the reading and writing skills, and in a lower degree in the speaking and listening ones. This paper proposes a series of innovative and informal training activities, such as cine-forum on technical civil engineering topics and role playing on real professional situations, that allow Spanish civil engineering students to develop English skills, that can rarely be worked in the classroom (i. e. speaking, negotiating and conversing), which encourage debate, participation, and foster their self-confidence to speak about technical-English topics in public. Although the students’ level of English is much lower than expected, they all agree on the importance of technical English for their future career. The results also show the students’ lack in skills that are difficult to train in regular classes (speaking and talking). Consequently, this situation would require to provide complementary activities like the ones suggested in this project in order to develop these skills and increase the students’ demand for engineering classes taught in English. В последние годы традиционное преподавание с использованием обычной доски дополняется визуальными средствами, такими как слайд-проекторы и видео. Феноменальный рост Интернета привел к появлению новых учебных средств массовой информации, таких как онлайн-курсы общего пользования, которые делают доступными образовательные ресурсы для более широкого и удаленного контингента студентов. Легкий доступ к образованию может повысить мотивацию, что является полезным коммерческим инструментом для университетов. В отличие от других дисциплин, таких как экономика или психология, МООК редко используются для распространения курсов по дисциплинам направления «Строительство». Чтобы восполнить этот пробел и поощрить использование МООК среди строительных университетов, в настоящем документе представлен опыт создания такого курса для многодисциплинарного проектирования мостов, созданных Университетом Кастилии и Ла Манча. Этот курс основан на опыте, полученном на конкурсе по строительству мостов с заданиями для студентов‑магистрантов, организованных Университетом Кастилии и Ла Манча в 2015, 2016 и 2017 годах.

In the field of bridge structural system identification (SSI), Bernoulli beam element models are often used to solve inverse problems. More rarely, Timoshenko beam element models can be calibrated. However, these models account for only the general shear effects, whereas other shear effects, such as shear lag, are not accounted for. However, as wide-flange box girder bridges become prevalent due to design demands, neglecting shear lag may introduce significant errors in predicting the mechanical parameters of the system and, hence, reduce the accuracy. In this paper, for the first time, the shear lag's effect on the vertical deflections is taken into account in an inverse problem. A parametric SSI, the observability method (OM), is updated to address the identification of thin-walled box girder bridges with wide flanges, including the shear lag effects. The structural analytical equations are used to connect the spatial shear effects with the beam-unidimensional-element model to be applied in the inverse analysis, which is referred to as the analytical observability method (AOM-SSI). This updated version of the OM is established and validated to identify the mechanical parameters of a structural test. The identified mechanical parameters show much better agreement with the expected results than those obtained with previous methods. This work was supported by BIA2017-86811-C2-1-R Spanish Ministry of Economy and Competitiveness, Spain. It was also supported by the Innovation Group Project, Natural Science Foundation of Hubei, China (Grant No. 2020CFA047) and the National Natural Science Foundation of China (Grant No.52178104).

[EN] This paper describes a study of the Tempul Aqueduct, one of the first structures designed and built by Eduardo Torroja. At a time when computers did not exist, Torroja's courage and innovation were outstanding. He was in no way constrained by a lack of theoretical knowledge, inadequate materials and the contemporary doubts about cable-stayed structures. In fact, he was able to build one of the world's first prestressed concrete structures, and a precursor to modern cable-stayed and extradosed bridges. This paper briefly reviews the history of the Tempul Aqueduct, gives the results of the analysis of this structure by several Finite Element Models (FEMs), and compares the FEM results to those obtained by Torroja himself. The FEM results confirm the validity of Torroja's conceptual design. The paper also contains a detailed analysis of the influence of the structural system on the behavior of the bridge and the effect of removing the live loads with the aim of providing a better understanding of the context and behavior of the Tempul aqueduct., Funding for this research has been provided to Mr Lozano-Galant by the Spanish Ministry of Economy, Industry and Competitiveness (Research Project BIA2013-47290-R from FEDER funds). The authors are also grateful to Prof. S. Buonopane of Bucknell University and J.L. Temprado, of COMPOSAN, for their assistance and support. The authors also want to thank the CEHOPU-Archivo Torroja, for all the information and support provided.

Structural Health Monitoring (SHM) is essential to assess the accuracy of durability predictions of structures. Using low-cost sensors on structural evaluation has gained significant attention compare to high-cost sensors. Although these may not be as accurate and sensitive as the expensive electronic devices, with efficient code and right use, there is a possibility of getting useful information from them. These sensors can vary based on their functionality and the measurements they provide. For example, one is highly sensitive to the light of its environment while the other kind would give different results in different temperatures. In this paper, three different displacement measuring sensors have been studied. An ultrasonic sensor (HC-SR04) and two different types of laser sensors (VL53L0X and VL53L1X) are investigated in the paper. An Arduino Mega has captured their measured data, and a raspberry pi has made the acquisition. Not only issues regarding coding and placing of these sensors have been presented ultimately, but precise solutions for the aforementioned problems as well as an efficient way of assembling all the sensors are also presented in this paper. The data generated from these electronic devices can be used for Structural Health Monitoring applications. The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research project BIA2017-86811-C2-1-R directed by José Turmo and BIA2017-86811-C2-2-R, directed by Jose Antonio Lozano-Galant. All these projects are funded with FEDER funds. Authors are also indebted to the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya for the funding provided through Agaur (2017 SGR 1482). It is also to be noted that funding for this research has been provided for MR. SEYEDMILAD KOMARIZADEHASL by Agencia Estatal de Investigación del Ministerio de Ciencia Innovación y Universidades grant and the Fondo Social Europeo grant (PRE2018-083238).

Temperature and humidity measurements provide useful information on multiple areas of civil engineering application such as Structural Health Monitoring (SHM), Structural System Identification (SSI) and structures rehabilitation. Majority of the existing commercial systems are so costly and also these measurement paradigms need many reference spots for a full-scale structure. The aforesaid paradigms are based on collecting data through smart devices, transferring information to each other and in the final stage processing the obtained information collaboratively through cloud computing or the others technologies. Taking into account the above information and obstacles, utilizing the Open Source Platforms (OSP) microcontrollers like Arduino as well as low cost sensors are attracting more and more attention. This paper gives a comprehensive information about the most determinant aspects of the aforementioned kits in terms of their pros and cons, installation procedure, communication protocol, number of the required connections and specific characteristics of the data acquisition system, Las mediciones de temperatura y humedad proporcionan información útil en múltiples áreas de aplicación de la ingeniería civil, como la monitorización de la salud estructural (SHM), la identificación de sistemas estructurales (SSI) y la rehabilitación de estructuras. La mayoría de los sistemas comerciales existentes son muy costosos y además estos paradigmas de medición necesitan muchos puntos de referencia para una estructura a escala real. Dichos paradigmas se basan en la recogida de datos a través de dispositivos inteligentes, la transferencia de información entre ellos y, en la etapa final, el procesamiento de la información obtenida de forma colaborativa a través de la computación en la nube u otras tecnologías. Teniendo en cuenta la información y los obstáculos anteriores, la utilización de microcontroladores de plataformas de código abierto (OSP) como Arduino, así como de sensores de bajo coste, está atrayendo cada vez más atención. Este artículo ofrece una información exhaustiva sobre los aspectos más determinantes de los kits mencionados en términos de sus pros y sus contras, el procedimiento de instalación, el protocolo de comunicación, el número de conexiones necesarias y las características específicas del sistema de adquisición de datos.

In the last years, more and more studies highlight the advantages of complementing traditional master classes with additional activities that improve students´ learning experience. This combination of teaching techniques is specially advised in the field of structural engineering, where intuition of the structural response it is of vital importance to understand the studied concepts. This paper deals with the introduction of a new (and more encouraging) educational tool to introduce intuitively students in the dynamic response of structures excited with an educational shaking table. Most of the educational structural health monitoring systems use sensors to determine the dynamic response of the structure. The proposed tool is based on a radically different approach, as it is based on low-cost image-recognition techniques. In fact, it only requires the use an amateur camera, a black background and a computer. In this study, the effects of both the camera location and the image quality are also evaluated. Finally, to validate the applicability of the proposed methodology, the dynamic response of small-scale buildings with different typologies is analyzed. In addition, a series of surveys were conducted in order to evaluate the activity based on student´s satisfaction and the actual acquisition and strengthening of knowledge.

Structural system identification (SSI) is a powerful tool for the assessment of the current condition of structures in operation. The basic assumption is that the deterioration of structures is reflected in the change of structural parameters. In SSI, the observability of these parameters depends on the location and the number of sensors. If the available sensors are less than the required ones, some parameters might not be observed. Furthermore, the incapability of identifying all parameters might occur when the sensors are sufficient but placed improperly. An investigation was carried out using SSI by observability method when then number of measurements is the same as the number of sensors. It is seen that a large proportion of the studied measurement sets cannot ensure the observability of all parameters. To improve the observability of structural parameters, a two-stage static SSI method is presented to fully exploit the information in the measurements. In the first stage, the SSI problem is treated in a linear manner and thereby the computation is greatly reduced. In the following stage, the nonlinear relations among the variables in the formulated system are recovered and thus the capability of the method to observe those structural parameters is enhanced.

In a staggered erected cable-stayed bridge made of concrete, time-dependent phenomena (suchas creep or shrinkage) effects might play an important role in both its geometry and its stress state. In fact, because of these phenomena, stays will indeed lose force and higher bending moments will appear in the structure. To compensate these effects, one or two re-stressing operations are traditionally planned during the life time of long span cable- stayed bridges made of concrete. These re-stressing operations might be technologically challenging and always imply additional costs. To guarantee that allowable stresses and deflections are not exceeded during erection, a number of simulation methods are presented in the literature. Some of these methods, concretely those based on a backward simulation approach, fail addressing the effects of the timedependent phenomena. To simulate these effects, methods based on the forward simulation approach are traditionally followed. Nevertheless, the main trade-off of these algorithms is that their computation is based on complex iterative processes that make simulation more time consuming. Furthermore, these methods are not able to avoid the need of additional re-stressing operations in service to prevent the effects of the timedependent phenomena. To fill all these gaps, a new simulation algorithm, the Forward-Direct Algorithm (FDA), is formally presented in this paper to simulate the construction process of cable-stayed bridges including the time-dependent phenomena effects. This algorithm takes advantage of the unstressed length of the stays concept to carry out a computationally efficient simulation based on an innovative direct simulation approach. The major advantage of this algorithm is the fact that the prestressing operations during construction can be defined to avoid the need of additional re-tensioning operations in service. To illustrate the creep and shrinkage effects, the proposed algorithm is applied to a real cable-stayed bridge. This tool also can be used by the designer or the contractor for construction control of the strand by strand tensioning technique.

This paper presents a finite element model for the analysis of composite beams with partial interaction. In this model, the elements of the composite beams are modeled by six different types of frame elements. Compared with other methods presented in the literature, the main advantages of the proposed method are as follows: (1) intuitiveness, as the different elements of the model present a close and easy to understand relation with the structural behavior of the composite beam; (2) applicability as the method directly provides useful information for the design work; (3) versatility and generalization in dealing with any combination of loading and boundary conditions (Furthermore, the proposed model enables the analysis of statically indeterminate structures, tapered beams as well as structures with non-uniform shear connector distributions.); (4) easy elaboration of models; and (5) possible widespread use of the model, as the proposed method can be implemented in any structural software. To validate the accuracy and the efficiency of the proposed model, a set of FEMs are verified against those results obtained by analytical equations available in the literature for different boundary and loading conditions. Furthermore, a set of parametric studies are performed to investigate the effects of the size of the FEMs along with the influence of the connection stiffness on the behavior of composite beams with different I beams.

Structural collapses have indirectly produced important progress in science. The last lesson learnt from structural collapses reveals the important role of polyrational systems of equations in the Civil Engineering field, as all problems in Physics and Engineering involving scale variables lead to systems of these equations. Since no efficient methods are known to solve this type of equations, a powerful and efficient method to multivariate polyrational equations using observability techniques is presented in this paper. It is pointed out that this method can be applied to solve different Civil Engineering problems. The information obtained by this tool can be used to assist decision making and risk management processes during maintenance and service life. As an example of its use, a structural damage detection problem is solved.

Construction of cable stayed bridges is very challenging. These structures are extremely redundant and the effect of tensioning one cable has the effect of changing the stresses of the already installed cables. In order to achieve a targeted service state at the end of the construction process careful calculations has to be done by the contractor in order to ensure it. However, deviations arise between the modelling of the tensioning process and the actual results obtained on site. In order to adjust the final stresses in the cables, a final restress of the stays is unusually required. This re-stressing operation is usually done for the whole cable, as the strand by strand stressing technique used for the first stressing operations, cannot be used anymore. This last operation is costly, time consuming and has less accuracy, compared with the strand by strand tensioning techniques. The paper will present a method to control the tensioning process on site and to modify it according to the stresses measured in the cables at each stressing stage. In this way, the chances of requiring a restressing operation are diminished.

The usual moderate dimensions of footbridges allow design architects (and sometimes engineers) to provide such structures with capricious forms. Under such circumstances, the analysis of the service state is usually very thorough, devoting to the study of the construction stages much less attention. However, it is very well known that the construction procedure can determine the service stage. Moreover, dimensions of footbridges also allow a wide range of construction procedures. For example, when cables are used to help to support the deck, as in cable stayed bridges, those are, namely, cantilever method, temporary support method, movement of the bridge to its final position as well as bridge launching. When the cables are used in tied arch bridges most of the previously mentioned methods might be used, especially temporary support method, movement of the bridge to its final position as well as bridge launching techniques. Having this in mind, it is crucial for the designer and for the contractor to have practical tools for construction control of the tensioning process of the stays, as this will condition the service stresses of the bridges. This is challenging, as the prestressing of one stay affects the stresses of the already installed stays. This paper will present a procedure to calculate the stress to be given to the first strand of a stay when the strand by strand tensioning technique is used. Also, a procedure to modify the tensioning process of a cable supported bridges to minimize deviation between design and actual stay stresses in service will be presented.

Traditionally, Spanish schools of civil engineering provide their students a class on “Technical English” in order to develop their language skills. However, this class does not cover all the skills that the student would need in the labor market and mainly focuses in the reading and writing skills, and in a lower degree in the speaking and listening ones. This paper proposes a series of innovative and informal training activities (cine-forum on technical civil engineering topics and role playing on real professional situations) that allow Spanish civil engineering students to develop English skills that can rarely be worked in the classroom (i.e. speaking, negotiating and conversing), encouraging debate, participation, and fostering their self-confidence to speak about technical-English topics in public. Although the students’ level of English is much lower than expected, they all agree on the importance of technical English for their future career. The results also show the students’ lack in skills that are difficult to train in regular classes (speaking and talking). Consequently, this situation would require to provide complementary activities like the ones suggested in this project in order to develop these skills and increase the students’ demand for engineering classes taught in English.

Externally anchored prestressed cables can be employed to enhance the stability of steel truss compression elements significantly. To demonstrate this concept, a system comprising a tubular strut subjected to an external compressive load and a prestressed cable anchored independently of the strut is studied. Energy methods are utilized to define the elastic stability of the perfect and imperfect systems, after which the first yield and rigid–plastic responses are explored. The influence of the key controlling parameters, including the length of the strut, the axial stiffness of the cable and the initial prestressing force, on the elastic stability, the inelastic response and the ultimate strength of the system is demonstrated using analytical and finite element (FE) models. To illustrate the application of the studied structural concept, FE modelling is employed to simulate the structural response of a prestressed hangar roof truss. A nearly two-fold enhancement in the load-carrying capacity of the truss structure is shown to be achieved owing to the addition of the prestressed cable.

This article deals with the problem of apply- ing observability techniques to structural system identi- fication, understanding as such the problem of identify- ing which is the subset of characteristics of the structure, such as Young's modulus, area, inertia, and/or product of them (flexural or axial stiffnesses) that can be uniquely defined when an adequate subset of deflections, forces, and/or moments in the nodes is provided. Compared with other standard observability problems, two issues arise here. First, nonlinear unknown variables (products or quotients of elemental variables) appear and second, the mechanical and geometrical properties of the structure are "coupled" with the deflections and/or rotations at the nodes. To solve these problems, an algebraic method that adapts the standard observability problem to deal with structural system identification is proposed in this article. The results obtained show, for the very first time, how ob- servability techniques can be efficiently used for the iden- tification of structural systems. Some examples are given to illustrate the proposed methodology and to demon- strate its power.

Eduardo Torroja's thin concrete shells stand among the best examples of structural engineering work of the 20th century. At a time when computers did not exist, Torroja's imagination and creativity were not constrained by the limits of the analytical methods available for structural design, and he was able to design and build economically innovative structures of the highest aesthetic quality. One of his major creations was the roof of the Frontón Recoletos, a unique two lobe thin shell that was destroyed during the Spanish Civil War. This paper reviews briefly the history of the Frontón, shows the results of a structural analysis of its roof by several Finite Element (FE) models of different complexity and precision, and compares FE results to those obtained by Torroja. FE results confirm the validity of Torroja's conceptual design, although he seems to have underestimated the internal forces and stresses in the roof. In addition, the paper analyses in detail the influence on the behaviour of the roof from its support conditions and from the stiffening ribs that Torroja designed but that never were built. As a result, the paper enables a better understanding of one of the masterpieces of Structural Art, and of simplified and complex shell analysis models, which is useful for the education of engineers as well as for future designs. © 2010 Elsevier Ltd., Funding for this research has been provided to Mr. Paya-Zaforteza by the Spanish Ministry of Education through its program for postdoctoral stays (Contract No. EX-2008-0669) and to Mr. Lozano-Galant by the Junta de Comunidades de Castilla La Mancha, Spain (Research Project PII2I09-0129-4085). The authors are also grateful to Prof. J. Antuna and J.A. Torroja of the Universidad Politecnica de Madrid, Professors C. Lazar and J.M. Adam of the Universidad Politecnica de Valencia and Professors H. Sundquist and C. Pacoste of the Royal Institute of Technology of Stockholm for their assistance and support. The authors also want to thank the Archivo Torroja and its librarian, Isabel Garcia, for all the information and support provided. Finally, the authors express their gratitude to CEng W. Plunket who carefully reviewed the English of the manuscript and to M.Sc. C. Llopis who lent the authors his original copy of Ref. [23].

Universities rarely have time to develop a major tool for Civil Engineers: their social skills. As a result, recent graduates usually have troubles in presenting their work to different groups of people. During the last years, the internationalisation of Civil Engineering has increased their difficulties as they need to work in a common language that may differ with their first language. In addition, young engineers need to learn how to interact with people from other cultures around the world. These social skills demanded in the current labor market are traditionally learnt by young engineers themselves in a process that might be overwhelming.Being a member of IABSE, and specially participating in their conferences and annual meetings, offers a unique opportunity for young engineers to develop their social skills as they can get in contact and talk in front of a broad spectrum of engineers from both the industry and academia. Furthermore, young engineers can discuss topics and exchange ideas with senior and junior engineers in a friendly atmosphere.

Throughout the tensioning process of cable-stayed bridges changes in geometry, boundary conditions, applied loads as well as material properties may produce unacceptable stresses and/or deflections in the structure. Therefore, an appropriate simulation and structural verification of this process is especially advisable in this kind of structures. Nevertheless, the predicted tensioning process rarely coincides with that measured on site. Usually, deviations between actual and predicted structural behaviour are found in every construction stage. If these deviations are so large that the achievement of the pursued stress state cannot be assured after completion or exceeds safety thresholds, an additional tensioning stage is added. Then, the following calculated tensioning operations are needed. If throughout these stages new differences are measured, new additional tensioning stages would be added. The addition of these additional stages on site is both time- consuming, as the tensioning process must be interrupted, and expensive, as more tensioning operations than the initially calculated ones are required.This paper aims to fill this gap by providing a new method that eases the simulation of deviations in the tensioning strategy on site, the Forward Algorithm. This procedure has been applied to the temporary supports erection method as, despite its importance, no specific investigation of this erection technique has been found in the literature. The Forward Algorithm is especially indicated to control the construction process on site, increasing safety and decreasing construction time.

Summary 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. Copyright © 2016 John Wiley & Sons, Ltd.

One of the fastest and more economical ways of erecting cable-stayed bridges consists on building the bridge deck on a set of temporary and permanent supports. Then, the stays are successively placed and tensioned according to a predefined tensioning sequence and the static scheme of the structure is successively changed. Despite this technique has been used for erecting many cable- stayed bridges worldwide, no specific research referring to the modelling of the temporary supports erection method has been found in existing literature. In fact, most of the literature is based on the alternative erection technique, the cantilever erection method, and the temporary supports erection method is usually only described in general terms. This paper aims to fill this gap by providing an algorithm specifically designed to model the construction process of cable-stayed bridges built on temporary supports from a backward approach. This algorithm can be efficiently used to define the initial design of the tensioning sequence and, because of its simplicity; it can be easily implemented in any structural code that enables the modelling of the prestressing of the stays by means of imposed strains or imposed temperature increments.

The condition assessment of pedestrian bridges might be overlooked due to the small scale of these structures. A short list of accidents is provided to justify the necessity of condition assessment on pedestrian bridges. In this paper, the structural system identification by observability method is applied in two traditional arrangements of pedestrian bridges. In the simply supported beam example, the symbolical expressions of the estimation for bending stiffnesses are derived first. The validity of the method is justified by the accurate estimations using error-free measurements. However, as the real-life measurements are inevitably polluted by errors, the effect of measurement errors is thoroughly studied according to measurement errors in a particular measurement, loading cases and errors in all measurements. The simulation errors of the method is also demonstrated by a two-span continuous beam. The results show that the loading case is important regarding the accuracy of the estimations.

Despite of the growing number of built examples, the analysis of non-symmetrical cable-stayed bridges has not received considerable attention from the researchers. In feet, the effects of the main design parameters in the structural behavior of these bridges are not addressed in detail in the literature. To fill this gap, this paper studies the structural response of a number of non-symmetrical cable-stayed bridges. With this aim, a parametric analysis is performed to evaluate the effect of each of the main design parameters (the ratio between the main and the back span length, the pylon, the deck and backstay stiflhesses, the pylon inclination, and the stay configuration) of this kind of bridges. Furthermore, the role of the geometrical nonlinearity and the steel consumption in stays are evaluated.

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.2425 This 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.

The structural response of any structure is traditionally predicted by simplistic physics-based models. In these models the mechanical and geometrical properties are assumed as known. Nevertheless, this is not the case in most actual structures where the values of the actual properties (such as axial or flexural stiffness) are unknown due to uncertainties in the materials, in the construction methods or in the stress state. In some cases, a calibration of the computer models is required to improve de accuracy of the predicted structural response. To carry out this task Structural System Identification (SSI) methods can be used. In this paper, a new parametric method for SSI from static excitation response is proposed. This method is based on the observability of the structure, understanding as such the problem of identifying which is the subset of characteristics of the structure, such as Young’s modulus, area, inertia, and/or products of them (axial or flexural stiffnesses) that may be uniquely determined when a subset of deflections and forces at nodes is provided. This method has lead to the development of a powerful mathematical tool to deal efficiently with polynomial systems of equations with a number of applications in many fields of science and engineering. To illustrate the applicability of the proposed method, the analysis of the SSI of two structures of growing complexity is presented.

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 method is the target time in which the OSS is defined to be achieved. The application of this method to two different structures showed the convenience of defining the OSS to be achieved at early times because that way the envelope of service stresses is reduced.

The temporary supports erection method is the most common way of building cable-stayed bridges. In this technique the bridge deck is first built over a set of temporary and permanent supports. Then, during the tensioning process, the stays are successively placed and tensioned by the jacks and the deck is raised from the temporary supports. Several variants of this method are the launching of the bridge and the rotation method. This paper proposes an algorithm to calculate and to control the construction of such bridges when the strand by strand tensioning technique is used. It is based on the unstressed length of the stays concept. The use of such concept enables a fast and direct simulation of construction stages by analysing independent Finite Element Models. As there is no need of superposition of models it is a very convenient way for construction supervision.

Despite its importance in some structures, shear deformation is systematically neglected by most static structural system identification methods. To fill this gap, this paper analyzes, for the first time in the literature, the effect of the shear deformation in the inverse analysis of structures. This study is focused on a parametric structural system identification method: the observability technique. As the majority of the methods, this technique is based on the Euler-Bernoulli beam theory. The method presented in the literature is unable to identify correctly the characteristics of a structure (such as flexural stiffness) when shear deformation is not negligible. In fact, in this method, the effects of shear deformation are close to those produced by measurement errors. To solve this problem, the observability procedure is updated according to the Timoshenko’s beam theory. This formulation uses an algebraic approach combining both a symbolical and a numerical application. Thus, the updated observability formulation is able to obtain not only flexural stiffness but also shear stiffness. Besides this, for the first time in the literature, a parametric equation of the estimates is obtained. Some examples are presented to illustrate the validity of the new formulation.

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 determined OSS for a given time including the time-dependent phenomena effects and the evolutionary erection of the superstructure. (2) Simulate the construction process assuring the achievement of a given OSS without the need of an overall iterative process taking into account time-dependent phenomena. (3) Provide the prestressing sequence in such a way that no additional tensioning operations are required to correct creep and shrinkage effects in service. To fill all these gaps, a new algorithm, the Forward-Direct Algorithm (FDA), is formally presented in this paper to simulate the construction process of cable-stayed bridges built on temporary supports. The main innovation of this algorithm consists of introducing the time-dependent phenomena effects into the unstressed length of the stays concept to calculate the prestressing strains to be introduced during the last re-tensioning operation. The application of the unstressed length concept has major advantages both in the simulation (as the OSS can be achieved without any overall iterative process) and in service (as re-tensioning operations to correct time-dependent phenomena effects can be avoided). To illustrate the creep and shrinkage effects during the construction and in service the FDA is applied to a real cable-stayed bridge. Furthermore, an analysis to define the optimum time to achieve the OSS is presented.