1,721,123 research outputs found
Fatigue analysis induced by vibrations in stay-cables subjected to along wind turbulence component
No full textCable-stayed bridges are very well optimized structural systems with light stiffening girder, supported by stays with an efficient transfer of forces to the towers. In recent years, these favorable structural characteristics, as well as aesthetic qualities, contributed to the increase of the length of spans up to 1000 m. The increase of span length brought to the need of investigating new problems: one of these is the out-of-plane cables vibration, which can generate fatigue problems near the anchorages, due to the rise of additional stresses. In this study, the fatigue behavior of stay cables under wind action is investigated, taking into account only the along-wind component of wind velocity. Particularly the fatigue stress analysis at the end zones of bridge stays is considered. The effects induced by the geometric non-linearity of the structure are taken into account; by using the Hamilton’s principle, the motion equations are obtained through an original continuous approach. The problem is carried out in the time domain and the stay is idealized as a bending stiffened cable analyzed in the large displacements field. © 2015, Taylor & Francis Group, London
Dynamic analysis of axially loaded cantilever shear‐beam under large deflections with small rotations
Full text linkThe modal analysis and seismic response of a vibrating cantilever, with or without tip mass and rotary inertia, are investigated in this study using a shear deformable beam model and including the effect of vertical load. Based on existing approaches, an original method is proposed that does not use fourth-order uncoupled equations to determine modal deflection and rotation. In fact, the approach presented herein transforms the second-order coupled system into a first-order system which can be solved more easily using matrix algebra and Laplace transform. Furthermore, the proposed form allows a straightforward demonstration of orthogonality conditions, that is, the problem is self-adjoint, and the solution in the case of forced response using modal superposition. In addition, even if the solution presented herein is applicable only to the cantilever with a tip mass and rotary inertia, the scope is general, and the approach can be applied to shear deformable beams with other boundary conditions. Finally, the seismic response by modal superposition is shown, and some examples are proposed and discussed for the case of uniform or continuously varying cross-sectional properties
A continuous vibration analysis model for cables with sag and bending stiffness
No full textThe paper reports an investigation on a continuous model for dynamics of large-diameter sagged cables, taking bending stiffness and sag extensibility into account. Following the classical guidelines of cable dynamics, and by making some simplifications, a continuous model is found in this work; frequency and mode shape equations have been obtained in non-dimensional form. Comparison with Finite Element (FE) and Finite Difference (FD) models has been made to validate the proposed method. Moreover, it allows us to represent local effects at the end zones of cable correctly, if clamped boundary conditions are assumed. To obtain comparable results, the FE model would require a large subdivision, with consequently, a large number of elements. The proposed eigenfunctions allow us to solve the dynamic problem without a large computational effort compared to FE or FD approaches. Finally, in order to show the usefulness of the developed continuous model, an application on the main cables of the designed Messina Strait Bridge has been made. © 2007 Elsevier Ltd. All rights reserved
Analysis of No-Tension Material Arch Bridges with Finite Compression Strength
No full textThe mechanism method, based on the particularization of limit design to masonry structures proposed by Heyman, is certainly a very suitable procedure for the analysis of no-tension material arches, especially because of its simplicity. The literature largely treats the method under the hypothesis of infinite compressive strength of the material, whereas fewer studies are devoted to finite compression strength. In this paper the latter case is revisited with reference to masonry arch bridges, assuming a rigid-perfect plastic model for the material and using a nondimensional formulation. In this way, results are derived and discussed for a wide range of parameters. The results are compared with those obtained using Heyman's hypotheses. © 2016 American Society of Civil Engineers
Il silenzio significativo come misura di semplificazione dell'attività edilizia: dubbi e prospettive
No full textL'articolo esamina la disciplina del silenzio in materia di accertamento di conformità, di condono edilizio, di agibilità degli edifici e di rilascio del permesso di costruire
La funzione di produzione di certezza pubblica nelle riflessioni di Antonio Romano Tassone
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