A New Experimental Investigation for Improving Bridge Management Systems and Road Operation Sustainability

Generally, during maintenance operations on bridges and motorway viaducts, the circulation of vehicles is limited or suspended. This causes significant economic losses due to the increase in the costs of transport: delays, increased fuel consumption, higher emissions of pollutants into the atmosphere, increased risk of accidents, etc. However, few studies have analyzed the influence of bridge vibrations on the final mechanical properties of the cement mortar placing during ordinary bridge service. As such, interest is increasing in repair techniques that could achieve high structural performance without reducing road service levels. This paper provides the results obtained through an innovative laboratory trials campaign that evaluated the influence of vibrations on the mechanical properties of high-performance mortar used for repairing bridge decks. The results of 24 cubic and prismatic specimens showed the relationship between the traffic-induced vibrations and the mechanical characteristics of the studied mortar. The findings can be considered as the first methodologic step that is necessary to address further field studies, drawing a detailed link between the repair techniques and transportation user costs. Based on the obtained results, a synthetic bridge management system framework was developed that merges the road function into the structural issue with the goals of increasing the resilience of road networks and optimizing the maintenance resources budget.

Determination of OH-groups concentration, and point defects in lithium niobate crystals.

The analysis of structural particularities of nominally pure and doped LiNbO3single crystals was performed by methods of Raman light scattering and infrared absorption. The concentration of OH groups, as well as the concentration of point defects is calculated from IR absorption spectra in the region of stretching vibrations of OH groups. A correlation has been determined in behavior of IR absorption spectra bands of strongly doped LiNbO3:Zn crystals with the behavior of the Raman spectra band that correspondsto stretching bridge vibrations of oxygen atoms in octahedra along the polar axis.

Symmetry/Asymmetry of the NHN Hydrogen Bond in Protonated 1,8-Bis(dimethylamino)naphthalene

Experimental and theoretical results are presented based on vibrational spectra and motional dynamics of 1,8-bis(dimethylamino)naphthalene (DMAN) and its protonated forms (DMANH+ and the DMANH+ HSO4− complex). The studies of these compounds have been performed in the gas phase and solid-state. Spectroscopic investigations were carried out by infrared spectroscopy (IR), Raman, and incoherent inelastic neutron scattering (IINS) experimental methods. Density functional theory (DFT) and Car–Parrinello molecular dynamics (CPMD) methods were applied to support our experimental findings. The fundamental investigations of hydrogen bridge vibrations were accomplished on the basis of isotopic substitutions (NH → ND). Special attention was paid to the bridged proton dynamics in the DMANH+ complex, which was found to be affected by interactions with the HSO4− anion.

Reduction of vibration and noise in rail transit steel bridges using elastomer mats: Numerical analysis and experimental validation

The noise radiating from a steel bridge can be much greater than the pass-by noise levels of trains at-grade. This is attributed to a special phenomenon known as the steel bridge-borne noise, which occurs when shocks and vibrations due to moving train loads are transferred onto the bridge. To investigate the effectiveness of elastomer mats for reducing vibration and noise in rail transit steel bridges, a frequency domain prediction model is established and calibrated through a field experiment. In this model, the train and track interactions were investigated analytically, and the receptance technique was introduced to determine the force transmitted from a multi-layer track structure to the bridge deck. The local vibrations of the bridge components were solved numerically using a hybrid shell/beam finite element model based on a harmonic response analysis. The bridge vibrations were regarded as the source of noise radiation by considering each bridge component as a rectangular flat plate noise source. There was good agreement between the calculated and measured results in terms of both the magnitude and frequency dependence. The mechanisms of vibration transmission and noise radiation were investigated using numerical simulations. In addition, the vibration and noise reduction effects are discussed by numerically comparing a track system with and without an elastomer mat.

Определение стехиометрии, концентрации ОН-групп и точечных дефектов в кристаллах ниобата лития по ИК спектрам поглощения

The concentration of OH groups, the ratio of Li/Nb, as well as the concentration of NbLi4+ and VLi- point defects is calculated from IR absorption spectra in the region of stretching vibrations of OH groups of LiNbO3 crystals. The crystals were of stoichiometric and congruent composition, as well as doped with doped near-threshold concentrations of magnesium and zinc. A correlation has been determined in behavior of IR absorption spectra bands of strongly doped LiNbO3:Mg and LiNbO3:Zn crystals with the behavior of the Raman spectra band that corresponds to stretching bridge vibrations of oxygen atoms in NbO6 octahedra along the polar axis.