Ballasted railway bridges are subject to dynamic excitation from passing trains, which can cause excessive vibrations in the ballast bed depending on the train speed, resulting in track instability. The Eurocode EN 1990 uses vertical deck acceleration as an indicator of safety, limited it to 3.5 m/s2 for ballasted bridges. Since experimental studies show that ballast instability occurs at about 7.0 m/s2, the normative limit seems to be arbitrarily based on a safety ratio of 2.0. The present paper examines the suitability of a lower safety ratio. The proposed methodology compares the physical acceleration limit with the design acceleration calculated at a critical speed corresponding to a failure probability of 10-4. An algorithm for the efficient assessment of critical speeds based on subset simulation is introduced, together with a parametric study for its optimization. A sensitivity analysis of the random variables of ballasted bridges allows the definition of two design scenarios in accordance with the Eurocode EN 1991-2. Results from the application of the methodology to four case study bridges show that design accelerations greater than the limit defined in the Eurocode can be found in ballasted bridges within the target probability of failure, suggesting that the safety ratio may be set lower than 2.0.

High-speed railway bridges are subjected to normative limitations concerning maximum permissible deck accelerations. For the design of these structures, the European norm EN 1991-2 introduces the high-speed load model (HSLM)—a set of point loads intended to include the effects of existing high-speed trains. Yet, the evolution of current trains and the recent development of new load models motivate a discussion regarding the limits of validity of the HSLM. For this study, a large number of randomly generated load models of articulated, conventional, and regular trains are tested and compared with the envelope of HSLM effects. For each type of train, two sets of 100,000 load models are considered: one abiding by the limits of the EN 1991-2 and another considering wider limits. This comparison is achieved using both a bridge-independent metric (train signatures) and dynamic analyses on a case study bridge (the Canelas bridge of the Portuguese Railway Network). For the latter, a methodology to decrease the computational cost of moving loads analysis is introduced. Results show that some theoretical load models constructed within the stipulated limits of the norm can lead to effects not covered by the HSLM. This is especially noted in conventional trains, where there is a relation with larger distances between centres of adjacent vehicle bogies.

The assessment of running safety of railway bridges is conditioned by the Eurocode EN 1990 A2 by limiting vertical deck acceleration. On ballastless track bridges, this value is 5 m/s 2 . The background for this value is not clear, and it is believed that it originates in the application of an arbitrary safety factor of 2 on accelerations around 1 g to avoid loss of wheel-rail contact. However, studies show that the level of acceleration may not be directly related to the occurrence of derailment. In this work, this idea is expanded by assessing both vertical and lateral dynamics, comparing acceleration values with the Unloading and Nadal derailment criteria. The parametric study is comprised of a set of five representative single-track slab bridges with spans between 10 m and 30 m with two levels of track irregularities, corresponding to a well-maintained track and an Alert limit situation. A three-dimensional articulated FE model based on the load properties of the EN 1991-2 High-Speed Load Model A is presented, crossing the bridges at running speeds from 150 km/h to 400 km/h. Despite the complexity of the models, a large amount (1461) of full 3D train-track-bridge interaction dynamic analyses are performed, to produce a data set representative of the phenomenon. Results show a weak correlation between the criteria and deck acceleration (maximum r 2 of 0.47 for Unloading and 0.15 for Nadal). Additionally, track quality is shown to be a more conditioning factor for derailment when compared to resonance. This work contributes to discussing the thesis of using deck acceleration as an indicator of running safety, considering lateral dynamics.

The perovskite BaBiO$_3$ crystallizes in a cubic structure and undergoes structural transitions toward lower symmetry phases upon cooling. The two low-temperature monoclinic phases are insulating, and the origin of this unexpected non-metallic character has been under debate. Both monoclinic phases exhibit tilting and breathing distortions, which are connected with the insulating nature of this compound and may have important effects on phononic heat conductivity. Here, we report the first thermal conductivity measurement, $\kappa$(T), in pristine polycrystalline BaBiO$_3$ from 1.5 K to 310 K. At low and intermediate temperatures, we observe features reminiscent of a glass-like behavior, whereas at high-temperatures we find a downturn - typical of a crystalline solid. We compare our findings with available data of other recently investigated perovskite oxides displaying similar temperature dependence.

Short-span railway bridges subjected to high-speed traffic are structures where dynamic effects are mandatory. Additionally, the variability associated with materials and geometric characteristics introduces uncertainty to the safety assessment of railway traffic. This work discusses the current norm’s limit for vertical deck acceleration regarding the evaluation of stability on ballasted tracks, as stated on Annex A2 of EN1990. A probabilistic methodology to define a partial safety factor is presented, employing dynamic analyses and Monte Carlo simulations. The evaluation of a case study is presented for a single-span filler-beam bridge of the Portuguese Railways Network. The results allow the definition of deterministic design scenarios that are compared to the simulations’ outcome. Conclusions show consistent partial safety factors with the norm’s limit, contributing to further discussion of this factor.

In the design of reinforced concrete structures several limit states are usually verified using simplified methods instead of using complex direct calculation. Span-to-depth ratio limits are applied for deflection control. In the same way, a redistribution factor and the relative depth of the compression zone are applied for the required ductility, but this is not enough. In fact, specific span-to-depth ratio limits, which are developed in this paper, should also complement the conditions referred to here. A numerical study is developed to compute the deflection ductility index of a wide range of continuous beams (or one-way slabs) considering as ultimate point when the rotation capacity (given by MC2010 and EC2) is achieved. From the boundary between fragile and ductile failures, the new span-to-depth ratio limits for the required ductility are defined and compared with the existing similar limits for deflection control. The results indicate that: (i) for normal strength concrete (up to 50 MPa), the ductility limit is more restrictive than the deflection limit when the redistribution factor delta is lower than 0.9, being always more restrictive for high strength concrete; (ii) for the current building beams, the slenderness used (10 < 1/d < 20) allows ductile failures, while for typical building slabs (low reinforcement ratio, but high redistribution), the slenderness should be 1/d <= 20; (iii) the conditions of MC2010 and EC2 to use plastic analysis without any direct check of the rotation capacity are actually incomplete and need to be revised. The new span-to-depth ratio limits proposed in this paper, which satisfy both ductility and deflection requirements, depend on the redistribution factor, characteristic compressive strength of concrete and total mechanical reinforcement ratio.

A management system is a decision-making tool that uses mathematical models to predict the future condition of the infrastructures as well as to make recommendations to the project managers. Generally, an infrastructure management system shall include a system for processing and analysing data, predicting deterioration, proposing maintenance actions, forecasting costs, obtaining optimal solutions and defining strategies that considers the political and economic constraints. The focus on this paper will be the module regarding the definition of cost-models. During its life cycle, bridges are exposed to several issues that can compromise their functionality. In this way, performing maintenance and rehabilitation actions and establishing cost models are very important tasks to keep the bridge functions according to the demands of the society. In the field of bridge engineering, the cost models can be used for different purposes such as the definition of optimum maintenance policies and project investment alternatives. Also, they are very important for the decision-making process once they cover several aspects related to the decisions about the system’s performance and decisions that are influenced by social-economic aspects. Hence, the idea of this paper is to discuss different approaches of how the cost-models are evaluated over a life cycle of a bridge due different scenarios of maintenance and rehabilitation with an application to a case study.

The First International Symposium on Risk Analysis and Safety of Complex Structures and Components (IRAS 2019) was organised in-teamed with the ESIS/TC12 Technical Committee on Risk Analysis and Safety of Large Structures and Components, which took place between 1-2 July 2019 at the Faculty of Engineering of the University of Porto (FEUP), in the City of Porto, located at seaside in the northwest region of Portugal. The guest editors of the IRAS 2019 deeply acknowledges all members of the International Scientific Committee, Thematic Sessions Organizers, Keynote Speakers and authors that contributed to the success of this event, that gathered more than 126 participants presenting more than 168 papers and posters. Sponsors are also fully acknowledged for their important contributions. The ESIS/TC12 2019 winners of the Robert Moskovic Award, Award of Merit TC12, and ESIS/TC12 Young Scientist Award were announced during the conference. Additionally, the guest editors (conference chairs) sincerely thank the tireless efforts of the Organizing Committee members as well as students and other FEUP and Construction Institute staff involved in the organization. Finally, the guest editors are pleased to inform that the second edition of the IRAS event will be organised by Prof. Aleksandar Sedmak (University of Belgrade, Serbia) which will take place in Belgrade in Serbia in the year 2021.

Bridges present valuable assets for the rail network by providing cross critical links such as waterways, valleys, and other types of facilities. However, these types of structures, during their life-cycle, are exposed to several threats such as natural hazards and deterioration. In fact, the lack of maintenance can lead to large consequences either for the structure, such as the partial or total collapse of the system, or for people. To assess the condition state of bridges, several performance indicators, of both quantitative and qualitative nature, have been proposed over these last decades by several researchers. Such indicators present a valuable information about the actual condition of the bridge to avoid undesirable consequences. These performance indicators are assessed over time through predictive models and can be determinist or probabilistic. The latter has been largely applied once they allow considering uncertainties associated with deterioration of the bridge. It is known that the deterioration of an infrastructure it is due to progressive deterioration (e.g., corrosion of the reinforcement, cracking of the concrete) and shock deterioration (e.g. earthquakes, collisions, floods). The idea of this paper is then to analyse a railway bridge and develop a framework that can consider gradual degradation to develop an optimal maintenance schedule.

In the scope of infrastructure risk assessment, structural reliability analysis leads to a challenging problem in order to deal with conflicting objectives: accurate estimation of failure probabilities and computational efficiency. Since the application of classical reliability methods is limited and often leads to a prohibitive computational cost, metamodeling techniques (e.g. polynomial chaos, kriging, response surface methods (RSM), etc.) have been widely used. Nevertheless, existing RSM present limitations handling with highly non-linear limit states, large-scale problems and approximation error. To overcome these problems, this paper describes a cutting-edge response surface algorithm covering the following issues: (i) dimensionality reduction by a variable screening procedure; (ii) definition of a promising search domain; (iii) initial experimental design based on an optimized space-filling scheme; (iv) model selection according to a stepwise regression procedure; (v) model validation by a cross-validation approach; (vi) model fitting using a double weighted regression technique; (vii) sequential sampling scheme by exploring a defined region of interest; (viii) confidence interval of reliability estimates based on a bootstrapping technique. With the aim of proving its efficiency, a wide collection of six illustration examples, concerning both analytical and FE-based problems, was selected. By benchmarking obtained results with literature findings, proposed method not only outperforms existing RSM, but also provides a powerful alternative to the use of other metamodeling techniques. (C) 2018 Elsevier Ltd. All rights reserved.

The CIVIL’in program started in the academic year of 2015-2016 with the goal of integrate and monitoring the new first-year students on the Master of Civil Engineering (MIEC) study cycle of the Faculty of Engineering of the University of Porto (FEUP) [1]. The monitoring is conducted by tutorial during the first year, being assigned to the new student a single tutor that is a student attending advanced years. The tutor support is monitored by a MIEC teacher, which will assess the difficulties, give some advices to the issues raised by the tutor and observe the student’s progress. This program aims a better integration of MIEC new students at FEUP allowing the tutors to develop relationship, socialization and team spirit that will be relevant to the acquisition of personal soft skills that are important for its future integration in job environments. In the academic year of 2017-2018, after some experience in the CIVIL’in Program by promoting different activities like the “best Civil Engineering photo”, the “best Civil Engineering Department video”, it comes the idea of presenting an hand-on challenge where students can learn in a friendly environment with young and older students and teachers of the different areas of Civil Engineering. The challenge, developed and monitored by CIVIL’in teachers, was considered an interesting activity. Students could understand construction processes by building a wall and they could analyze the qualitative thermal and acoustic behavior of the built wall by comparing experimental results from different built walls. This was also an opportunity of visiting Civil Engineer laboratories, using the equipment and anticipating some concepts, which first-year students will explore and learn later in the study cycle. The walls, built with mortar and plastic bottles, glass bottles or cans, presented some interesting results that fascinated the students.

the Master of Civil Engineering (MIEC) at the Faculty of Engineering of the University of Porto (FEUP) is a 5 years’ study cycle. To integrate and monitoring the new first-year students on MIEC, by other students who attend advanced years, the CIVIL’in program has been developed. The monitoring is conducted by tutorial during the first academic year, being assigned to the new student a single tutor, who has the responsibility of helping the new student in its integration from the beginning of the study cycle until the end of the first academic year.A teacher, who will assess the difficulties, observes the progress of students and gives some advices to the questions raised by the tutor, monitors the performance of the tutor in this new and challenging mission. This initiative, in addition to allowing a better integration of the new students in FEUP, also enables the tutors to develop soft skills such as positive attitude, teamwork, leadership and communication skills that will be relevant for their future integration in enterprise environments.

Several technical and scientific publications have been made available focussing on Bridge Weight-in-Motion (BWIM) concerning railway bridges. On the contrary, BWIM analysis on road bridges are more scarce and therefore, this work intends to provide a contribution by presenting the BWIM analysis performed on two major road bridges in Portugal – Lezíria Bridge and Pinhão Bridge. These bridges are equipped with electric and optical strain gauges, acquisi­tion systems with features that allow high sampling rates. Based on the collected data and focussing on the bridges’ life­time, a probabilistic approach to quantify extreme traffic loads was implemented using extreme distribution functions. The bridges’ behaviour to these extreme traffic loads is numerically evaluated and a comparison with the alarm levels established by the bridge designers is performed. Although the bridge’s safety is not compromised, it was concluded that the representativeness of the observation period is a critical issue and the analysis of this kind of results must be care­fully considered. A comprehensive discussion about this matter is carried out at the end of this work.