Search results for "BRIDGES"

Mathematical formulation of pulse amplitude modulation selective harmonic elimination in multilevel three phase inverters

2022

In this paper multilevel cascaded H-bridges (CHB) three phase inverters with 2n dc sources, n=1,2,3,... are considered and a mathematical formulation providing both 2n switching angles and dc voltage source to eliminate n+1 harmonics and their respective multiple from their output voltage waveform, is proposed. The computed angles don't depend on modulation index and the source voltages linearly vary with it. The proposed procedure finds the solution through an analytical formula that avoids to solve transcendental systems and presents very low computational cost. A lot of low order harmonics are eliminated, returning a very low total harmonic distortion (THD). Particularly for 9-level conf…

Symplectic analysis of thin-walled curved box girders with torsion, distortion and shear lag warping effects

2022

Shear lag effect and torsional and distortional warping can significantly affect the performance of thin-walled curved box girders used in modern bridge engineering. The structural behaviour of these bridges exhibits complexity due to coupled bending and torsion together with warping effects of non-uniform torsion, distortion and shear lag. A practical method of analysis, based on the symplectic approach, with the same perspective as the Higher Order Beam Theories, is presented for overcoming the difficulties of numerical approaches via the Finite Element Method. In this paper, the Hamiltonian Structural Analysis method implements the analysis of the shear lag effect together with non-unifo…

Comportamento di una passerella pedonale strallata nei confronti delle azioni del vento

2007

The wind behaviour of a stayed footbridge has been analyzed. In order to avoid aeroelastic phenomena, an experimental campaign on a 1:15 scale model has been realized at the boundary-layer wind-tunnel of the Milan Polytechnic. The aerodynamic characterization of the structure has allowed to direct the project towards the choice of non-solid barriers, but with a medium porosity, by avoiding possible problems that can lead to ultimate limit state condi-tions of the structure (e.g., flutter or vortex shedding). In this way the quantitative effect of barriers has been estimated deducing reliable values not only for the alongwind forces, but also for the crosswind and torsional actions.

Inland navigation on French rivers

2020

DOI: https://doi.org/10.22032/dbt.40680 (pdf), https://doi.org/10.22032/dbt.40683 (csv), https://doi.org/10.22032/dbt.40682 (excel).; International audience

Fenomeni lenti nelle fasi di costruzione ed esercizio degli impalcati da ponte precompressi

2010

Creep effects and stress adjustments in cable-stayed bridges with concrete deck

2010

In construction stages of cable-stayed bridges with prestressed concrete deck, the influence of creep on stresses and strains is very important in order to foresee the final patterns of internal forces and displacements. In cantilever construction, the concrete deck can be considered, in each stage, as a continuous beam resting on elastic restraints, which modify with successive additions of new segments, until the last one has been assembled. In these stages stress relaxation in concrete occurs as well as vertical displacements increase. Ehen structure has been closed by inserting midspan segment, stress redistribution begins, due to creep. Deformation and internal force development in con…

A stress ribbon footbridge as the tie of an arch bridge.

2008

Dispositions légales concernant les ponts dans la législation de Justinien

2019

Many bridges built in the ancient Rome have survived to the present time. In this presentation, the author does not focus his attention on the architectural, archaeological, construction or statistical aspects. He discusses, above all, the legal regulations concerning the bridges in the Justinian's legislation. He is looking for an answer to the question of who in the ancient times at the Romans’ supervised the bridges. He wonders if the curatores pontis existed? It touches on the question of building a "private" bridge, the correlation of bridge issues and servitude, the bridge versus assassination, the bridge versus a suicide or the bridge versus taxes paid by the Church. The Romans did n…

Crystal structure of tricarbonyl(μ-diphenylphosphido-κ2P:P)(methyldiphenylsilyl-κSi)bis(triphenylphosphane-κP)iron(II)platinum(0)(Fe—Pt)

2015

The title compound belongs to the large family of heterodinuclear phosphide-bridged complexes. The Fe—Pt bond is of 2.7738 (4) Å and there is an unprecedented arrangement of the silyl ligand in a trans-position with respect to the metal–metal vector in the family of phosphide-bridged iron–platinum heterobimetallics.

Investigation about selective harmonic elimination in unbalanced multilevel inverters

2022

In this paper 5 and 7 levels cascaded H-bridges inverters are considered, feeding by unequal dc voltage sources. The effect of these unbalancing operation is examined concerning harmonic analysis and total harmonic distortion of the output voltages. The system of equations, obtained by the expansion in the Fourier series of phase output voltage, is solved by applying a method of graphic solution that allows obtaining the switching angles able to eliminate the lower order harmonics.