Tytuł Data publikacji Autor
A novel sandwich composite footbridge is described in this paper, for the first time after it has been put into operation over the Radunia River in the Pruszcz Gdański municipality. This paper presents results of dynamic tests and describes technical monitoring of the footbridge. The dynamic tests were conducted to estimate pedestrian comfort and were compared with the ones from numerical simulations made in the environment of Finite Element Method. A discussion of the obtained results is made then. The characteristics and capabilities of the network of sensors spread over the bridge to monitor its long-term behavior are described.
2020
Jacek Chróścielewski,
Mikołaj Miśkiewicz,
Łukasz Pyrzowski,
Magdalena Rucka,
Bartosz Sobczyk,
Krzysztof Wilde,
Błażej Meronk
The article presents numerical simulations, dynamic in situ load tests and a structural health monitoring (SHM) system installed in a suspended on a single cable footbridge. Numerical simulations performed prior to construction indicated the possibility of structural dynamics problems, finally confirmed in the course of dynamic test loading. In the dynamic load course the bridge deck developed vibrations displaying accelerations up to 4.5 m/s2. Such footbridge behavior causes unacceptable discomfort to the users and risk of structural damage. The tests brought about the need for repair works and the use of a monitoring system to increase operational safety of the object.
2020
Mikołaj Miśkiewicz,
Łukasz Pyrzowski,
Krzysztof Wilde
Adhesive joints have numerous applications in many branches of industry, such as civil engineering, automotive, aerospace and shipbuilding. As with most structural elements, adhesive joints can experience any damage mechanism, which induces the need for diagnostic testing. Ultrasonic waves are widely used for non-destructive inspection of many structures and their elements, including adhesive joints. Guided wave propagation method consists in excitation of wave in one point of analysed element and collection of signals in a set of points spread over this element. Further signal processing, such as calculation of root mean square values (RMS), can provide a precise damage imaging, because of a high vulnerability of wave characteristics to any discontinuity. The work is focused on identification and localisation of damaged areas in adhesive film of steelclad concrete beams. Steel-concrete composite elements, such as steel-clad concrete beams containing adhesive joints are commonly used in civil infrastructure. In the conducted research, composite specimens were prepared with the use of an epoxy-based adhesive Sikadur® 30 Normal. Artificial defects were performed by omitting adhesive film on a part of a joint. The input wave signal was provided by the arbitrary function generator. Elastic waves were excited by plate piezoelectric actuator placed on a steel plate. Signals of propagating waves were collected point by point on the surface of steel part of the joint, by means of the scanning laser vibrometer. The maps representing RMS values calculated individually for each signal proved to be an effective visualisation of the actual shape and position of damage areas.
2020
Erwin Wojtczak,
Magdalena Rucka,
Magdalena Knak
The main physical laws of thermal–plastic deformation and fatigue damage accumulation processes in polycrystalline structural alloys under various regimes of cyclic thermal–mechanical loading are considered. Within the framework of mechanics of damaged media, a mathematical model is developed that describes thermal–plastic deformation and fatigue damage accumulation processes under low-cycle loading. The model consists of three interrelated parts: relations defining plastic behavior of the material, accounting for its dependence on the failure process; evolutionary equations describing damage accumulation kinetics; a strength criterion of the damaged material. The plasticity model based on the notion of yield surface and the principle of orthogonality of the plastic strain vector to the yield surface is used as defining relations. This version of defining equations of plasticity describes the main effects of the deformation process under monotone cyclic, proportional and nonproportional loading regimes. The version of kinetic equations of damage accumulation is based on introducing a scalar parameter of damage degree and energy principles, and account for the main effects of nucleation, growth and merging of microdefects under arbitrary regimes of low-cycle loading. The strength criterion of the damaged material is based on reaching a critical value of the damage degree. The results of numerically modeling cyclic thermal–plastic deformation and fatigue damage accumulation in heat-resistant alloys (Nimonic 80A, Haynes 188) under combined thermal–mechanical loading are presented. Special attention is paid to the issues of modeling the processes of cyclic thermal–plastic deformation and fatigue damage accumulation for complex deformation processes accompanied by the rotation of the main stress and strain tensor areas. It is shown that the present damaged medium model accurately enough for engineering purposes describes the processes of cyclic isothermal and nonisothermal deformation and fatigue damage accumulation under combined thermal–mechanical loading and makes it possible to evaluate low-cycle fatigue life of heat-resistant alloys under arbitrary deformation trajectories.
2020
Ivan Volkov,
Leonid Igumnov,
Francesco Dell'isola,
Svetlana Litvinchuk,
Victor Eremeev
The asymptotic homogenization of periodic network materials modeled as beam networks is pursued in this contribution, accounting for surface effects arising from the presence of a thin coating on the surface of the structural beam elements of the network. Cauchy and second gradient effective continua are considered and enhanced by the consideration of surface effects. The asymptotic homogenization technique is here extended to account for the additional surface properties, which emerge in the asymptotic expansion of the effective stress and hyperstress tensors versus the small scale parameters and the additional small parameters related to surface effects. Based on the elaboration of small dimensionless parameters of geometrical or mechanical nature reflecting the different length scales, we construct different models in which the importance of surface effects is dictated by specific choice of the scaling relations between the introduced small parameters. The effective moduli reflect the introduced surface properties. We show in particular that surface effects may become dominant for specific choices of the scaling laws of the introduced small parameters. Examples of networks are given for each class of the considered effective constitutive models to illustrate the proposed general framework.
2020
Yosra Rahali,
Victor Eremeev,
Jean-François Ganghoffer
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