Трансформація проблеми вміння вчитись та її відображення в навчальній літературі з педагогіки

Стаття присвячена трансформації проблеми вміння вчитись у проблему загальнонавчальних умінь і навичок. Висвітлюється розвиток проблеми у наукових дослідженнях 60-80 років ХХ століття - початку ХХ століття

Steel-soil composite bridge:an alternative design solution for short-span bridges towards sustainability

The construction sector is a major source of greenhouse gases. Under the increasing concern about climate change and growing construction activities, the whole sector is challenged to shift focus toward sustainable solutions. The traditional procurement often prioritizes technical and economic viability, while their environmental performance is overlooked. Today’s designers are urged to seek new design options to reduce environmental burdens. Sweden owns more than 24574 bridges, most of which are short spans. Among them, the slab frame bridge (CFB) is a common solution. Soil steel composite bridge (SSCB), alternatively, is a functional equivalent solution to CFB and shows advantages in low cost and easy construction. This paper compares the environmental performance between these two bridge types based on life cycle assessment (LCA). The analysis and its results show that the SSCB is preferable over CFB in most of the examined environmental indicators

Estimating running safety factor of ballastless railway bridges using tail modelling

Excessive vertical acceleration of ballastless railway bridges subjected to vibrations induced by passing trains is one of the governing design criteria for bridges in high-speed lines. However, to the authors’ knowledge, the corresponding design limit is not based on a solid theoretical or experimental background. Moreover, the traditionally applied safety factor also suffers from these concerns. Therefore, in the present study, a crude probabilistic approach is adopted to evaluate the consistency and reliability of this safety factor. For this purpose, deterministically designed bridges (using conventional methods) with short to medium spans are considered. Then, their reliability is evaluated using simulation-based techniques and extreme value theory, i.e., tail approximation. Then, the existing safety factor is calculated to evaluate the consistency of the current approaches, and possible new values are proposed based on the desired target reliabilities

Dynamic behaviour of bridges under critical articulated trains: Signature and bogie factor applied to the review of some regulations included in EN 1991-2

[EN] The information contained in this paper will be of interest not only to bridge engineers, but also to train manufacturers. The article provides practical insight into the degree of coverage of realarticulated trains(ATs) that Eurocode EN1991-2 guarantees. In both the design of new railway bridges, as well as in the assessment of existing ones, the importance of a detailed knowledge of thelimits of validityofload modelscannot be overemphasised. Being essential components of the rail transportation system, the capacity of bridges to withstand future traffic demands will be determined precisely by the load models. Therefore, accurate definition of the limits of validity of such models reveals crucial when increased speeds and/or increased axle loads are required by transportation pressing priorities. The most relevant load model for a significant portion of the bridges in high-speed railway lines is the so-called HSLM-A model, defined in EN1991-2. Their limits of validity are described in Annex E of such code. For its singular importance, the effects of vibrations induced by HSLM-A are analysed in this paper with attention to the response ofsimply supported bridges. This analysis is carried out in a view to determine whether the limits of validity given in Annex E of EN1991-2 cover the largest part of cases of interest. Specifically, the vibration effects of HSLM-A are compared with those of the ATs described in such Annex E, and the response is analysed in depth for simply supported bridges, which are structures especially sensitive to passing trains at high speeds. New theoretical approaches have been developed in order to undertake this investigation, including a novel, simplified expression of thetrain signaturefor ATs that is convenient for its low computational cost. The mathematical proofs are included in the first part of the paper and two separate appendices.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was partially developed during a stay performed by Pedro Museros at the KTH Royal Institute of Technology, within the Division of Structural Engineering and Bridges (Stockholm, Sweden). The financial support of the Generalitat Valenciana, through the program BEST2019 for research stays (Subvenciones para estancias de personal investigador doctor en centros de investigacion radicados fuera de la Comunitat Valenciana), as well as the permission obtained from the Universitat Politecnica de Valencia to carry out such stay, are gratefully acknowledged.Museros Romero, P.; Andersson, A.; Marti, V.; Karoumi, R. (2021). Dynamic behaviour of bridges under critical articulated trains: Signature and bogie factor applied to the review of some regulations included in EN 1991-2. Proceedings of the Institution of Mechanical Engineers. Part F, Journal of rail and rapid transit (Online). 235(5):655-675. https://doi.org/10.1177/0954409720956476S655675235

Free vibration of viscoelastically supported beam bridges under moving loads: Closed-form formula for maximum resonant response

[EN] In this paper, a closed-form approximate formula for estimating the maximum resonant response of beam bridges on viscoelastic supports (VS) under moving loads is proposed. The methodology is based on the discrete approximation of the fundamental vertical mode of a non-proportionally damped Bernoulli-Euler beam, which allows the derivation of closed-form expressions for the fundamental modal characteristics and maximum amplitude of free vibration at the mid-span of VS beams. Finally, an approximate formula to estimate maximum resonant acceleration of VS beams under passage of articulated trains has been proposed. Verification studies prove that the approximate closed-form formula estimates the resonant peaks with good accuracy and is a useful tool for preliminary assessment of railway beam bridges considering the effect of soil-structure interaction at resonance. In combination with the use of full train signatures through the Residual Influence Line (LIR) method, the proposed solution yields good results also in the lower range of speeds, where resonant sub-harmonics are more intensely reduced by damping.This research was partly sponsored by the Swedish Research Council FORMAS and has also received funding from the Shift2Rail Joint Undertaking under the European Union's Horizon 2020 research and innovation program under grant agreement No 826255 which are gratefully acknowledged.Zangeneh, A.; Museros Romero, P.; Pacoste, C.; Karoumi, R. (2021). Free vibration of viscoelastically supported beam bridges under moving loads: Closed-form formula for maximum resonant response. Engineering Structures. 244:1-11. https://doi.org/10.1016/j.engstruct.2021.112759S11124

Aerodynamic Analysis of Simple Girder Bridges under Construction Phase

[EN] Bridge designs are becoming slender and lighter, making wind dynamic effects even more important than wind static effects. Some types of bridges show especially vulnerable situations during construction stages, when the structure is lighter or does not have its final stiffness. The aim of this document is to assess the dynamic wind loading on simple girder bridges during their construction phases. The studied section is formed by two steel beams supporting a concrete slab, but the analysis was made when the concrete slab has not been built yet. Several CFD simulations were made to find the aerodynamic parameters depending on the section¿s dimensions. Three construction stages were analyzed: when only one beam is placed, when both beams are in their final locations but they are not connected yet, and when both beams are joined by the bracing. The results showed that vortex shedding effects are stronger in the along-wind direction due to the low horizontal bending stiffness of the beams and their large area perpendicular to the flow. Increasing beams¿ distance is a good solution to reduce wind effects. However, closing the section with light plates was more effective, decreasing the frequency of vortex shedding and its effects.Sadrizadeh, S.; Martínez-López, G.; Ülker-Kaustell, M.; Karoumi, R. (2021). Aerodynamic Analysis of Simple Girder Bridges under Construction Phase. Applied Sciences. 11(12). https://doi.org/10.3390/app11125562111

Resonance and cancellation phenomena in two-span continuous beams and its application to railway bridges

The objective of this study is to evaluate the vibratory response of two-span continuous beams subjected to moving loads and, in particular, to investigate the maximum resonance and cancellation of resonance phenomena. The main practical interest is the evaluation of the maximum acceleration response in railway bridges, which is one of the most demanding Serviceability Limit States for traffic safety according to current regulations. Two-span continuous bridges, in their simplest version (i.e. uniform identical spans), present antisymmetric and symmetric modes with closely spaced natural frequencies, leading to a more involved dynamic behaviour than that of simply-supported bridges. First, the free vibration response of a Bernoulli-Euler two-span beam after the passage of a single load at constant speed is formulated analytically, and non-dimensional speeds leading to cancellation or maximum response in free vibration are obtained for each mode. Then, these conditions are equated to resonant speeds induced by equidistant load series, and span length-to-characteristic distance ratios causing cancelled out resonances, or remarkably prominent ones, are obtained. Based on the previous derivations, a methodology for detecting which could be the most aggressive trains for a particular structure based on pure geometrical considerations is discussed. Finally, the applicability of the theoretical derivations is shown through the numerical analysis of two real bridges belonging to the Swedish railway network