Development of Theoretical and Experimental Dynamic Monitoring of Large-scale Building Structure

The object of research is the method of monitoring and assessing the technical condition of the large-sized building structure of the International Exhibition Center (Kyiv, Ukraine). The currently applied method of monitoring this structure is based on the use of deformation indicators. The indicators of this method do not allow estimating the global technical state of the structure. Taking into account the social importance of the structure, it is possible to use dynamic monitoring while monitoring its technical condition.In the course of the study, two independent finite element models of the controlled facility are developed in the SCAD (Russia) and NASTRAN (USA) software complexes. With their help, a modal analysis was made and the values of the frequencies and forms of the natural oscillations of the structure were determined. The natural measurements of its natural frequencies have been made. It is found that the difference between the calculated and natural values of natural frequencies does not exceed 3 %.In addition, version of an automated experimental control system is proposed, which includes the use of three-component accelerometers MS2002+, Geoscop software, controlled by the operating system MS Server.The received results testify to the efficiency of the use of frequencies and forms of natural oscillations in the system of monitoring the technical state of the given structure. In comparison with static deformation parameters, they allow estimating the global technical condition and determining the integrity of the structure

Enhanced photorefractive properties of Bi-doped Sn2P2S6

International audienceEnhanced photorefractive properties of tin hypothiodiphosphate (Sn2P2S6) crystals as a result of Bi doping are presented. These new crystals were obtained by the vapor-transport technique using stoichiometric Sn2P2S6 composition with an additional amount of Bi up to 0.5 mol. % in the initial compound. The bandgap edges of the obtained crystals are located at ~750 nm and shift toward the red wavelengths with increasing Bi concentration. Sn2P2S6:Bi crystals are found to exhibit larger two-beam coupling gain coefficients (up to 17 cm−1 at a wavelength of 854 nm) as compared to (i) pure Sn2P2S6 (2.5 cm−1 at 854 nm), (ii) Sn2P2S6 crystals modified by the growth conditions (14 cm−1 at 860 nm), and (iii) Te-doped Sn2P2S6 (8 cm−1 at 860 nm). At the same time, for an intensity of 1.3 W/cm2 at 854 nm, buildup times of 0.9 and 2.5 ms at grating spacings of Λ=9.8 and 1.3 μm, respectively, are found; Bi-doped Sn2P2S6 crystals are the fastest among all the presently known Sn2P2S6 crystals operating at near-infrared wavelengths