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Do trzech razy sztuka - niestabilność dynamiczna mostu dla pieszych w Squibb Park przy Moście Brooklińskim

Bocian Mateusz, Czaplewski Bronisław

Inżynieria i Budownictwo

2022

R. 78, nr 1-2

58--61

Dokumentowanie problemów konstrukcyjnych może pomóc w zapobieganiu ich wystąpienia w przyszłości. Mając to na uwadze, w niniejszym artykule przedstawiono przypadek niestabilności dynamicznej Squibb Park Bridge pod wpływem obciążeń generowanych przez pieszych. Dokonano syntezy i krytycznej oceny informacji na temat konstrukcji i zachowania dynamicznego mostu dostępnych w domenie publicznej. Rozważania te wsparto analizami materiału wideo z okresu niestabilności zaobserwowanego wkrótce po otwarciu mostu oraz symulacjami modelu MES.

Documenting structural problems is of great benefit to structural engineers as it can help to prevent their occurrence in the future. In this spirit, this paper presents the case of dynamic instability of the Squibb Park Bridge under the action of walking pedestrians. The information on the bridge's design and dynamic behaviour available in public domain is synthesized and critically evaluated. This is aided with the analyses of a video footage from the instability period observed soon after the bridge's opening and simulations of an FE model.

Using symbolic computation in the characterization of frictional instabilities involving orthotropic materials

Agwa M. A., Pinto da Costa A.

International Journal of Applied Mathematics and Computer Science

2015

Vol. 25, no. 2

259--267

The present work addresses the problem of determining under what conditions the impending slip state or the steady sliding of a linear elastic orthotropic layer or half space with respect to a rigid flat obstacle is dynamically unstable. In other words, we search the conditions for the occurrence of smooth exponentially growing dynamic solutions with perturbed initial conditions arbitrarily close to the steady sliding state, taking the system away from the equilibrium state or the steady sliding state. Previously authors have shown that a linear elastic isotropic half space compressed against and sliding with respect to a rigid flat surface may get unstable by flutter when the coefficient of friction μ and Poisson's ratio ν are sufficiently large. In the isotropic case they have been able to derive closed form analytic expressions for the exponentially growing unstable solutions as well as for the borders of the stability regions in the space of parameters, because in the isotropic case there are only two dimensionless parameters (μ and ν). Already for the simplest version of orthotropy (an orthotropic transversally isotropic material) there are seven governing parameters (μ, five independent material constants and the orientation of the principal directions of orthotropy) and the expressions become very lengthy and literally impossible to manipulate manually. The orthotropic case addressed here is impossible to solve with simple closed form expressions, and therefore the use of computer algebra software is required, the main commands being indicated in the text.