Assessment of nonlinear seismic performance of a restored historical arch bridge using ambient vibrations

Historic masonry arch bridges are vital components of transportation systems in many countries worldwide, ensuring the ready access of goods and services to millions of people. The structural failure of these historic structures would severely and adversely impact the economies of these nations due to the massive disruptions of transportation systems accompanying such failures. To successfully maintain these aging masonry structures, performance assessment must incorporate the unique mechanical characteristics of masonry. Therefore, the preferred analysis technique must go beyond a linear approach. This study assesses the earthquake performance of a restored historical masonry arch bridge through nonlinear finite element analysis incorporating the Drucker–Prager damage criterion. The case study structure is the Mikron Arch Bridge, a nineteenth century Ottoman Era structure built over the Firtina River near Rize, Turkey, and restored in 1998. The Mikron Arch Bridge was first subjected to ambient vibration testing, during which accelerometers were placed at several points on the bridge span to record the bridge vibratory response. The investigators then used Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques to extract the experimental natural frequencies, mode shapes, and damping ratios from these measurements. Experimental results were compared with those obtained by the linear finite element analysis of the bridge. Good agreement between mode shapes was observed during this comparison, though natural frequencies disagree by 8–10%. The boundary conditions of the linear finite element model of Mikron Arch Bridge are adjusted such that the analytical predictions agree with the ambient vibration test results. By introducing the Drucker–Prager damage criterion, the calibrated linear FE model was next extended into a nonlinear model. Nonlinear analysis of seismic behavior of Mikron arch bridge was performed considering the acceleration record of Erzincan earthquake in 1992 that occurred near the Mikron Bridge region. The displacement and stress results were observed to be allowable level of the stone material. Moreover, linear FE model calibrations elicited a significant influence on the nonlinear FE model simulations.     

On the Gauss-Weierstrass summability of multiple trigonometric series at µ-smoothness points

The notion of μ-smoothness points of periodic functions of several variables is introduced and the rate of convergence of the Gauss-Weierstrass means of relevant Fourier series at these points is investigated.     

Bernstein series solution of a class of linear integro-differential equations with weakly singular kernel

In this study, a new collocation method based on the Bernstein polynomials is introduced for the approximate solution of a class of linear Volterra integro-differential equations with weakly singular kernel. If the exact solution is polynomial, then the exact solution can be obtained. If the exact solution is not a polynomial, then an accurate solution can be obtained with a combination of choice in the number of nodes and the number of digits in the solver. In addition, the method is presented with error and stability analysis.     

A Taylor matrix method for the solution of a two-dimensional linear hyperbolic equation

A Taylor matrix method is proposed for the numerical solution of the two-space-dimensional linear hyperbolic equation. This method transforms the equation into a matrix equation and the unknown of this equation is a Taylor coefficients matrix. Solutions are easily acquired by using this matrix equation, which corresponds to a system of linear algebraic equations. As a result, the finite Taylor series approach with three variables is obtained. The accuracy of the proposed method is demonstrated with one example.     

Assessment of 210Po and 210Pb by moss biomonitoring technique in Thrace region of Turkey

Journal of Radioanalytical and Nuclear Chemistry - This study presents the first data of 210Po and 210Pb activity concentrations using moss species Hypnum cupressiforme from Thrace region, the...     

Outlining In Vitro and In Silico Cholinesterase Inhibitory Activity of Twenty-Four Natural Products of Various Chemical Classes: Smilagenin,Kokusaginine, and Methyl Rosmarinate as Emboldening Inhibitors

Cholinesterase (ChE) inhibition is an important treatment strategy for Alzheimer’s disease (AD) as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are involved in the pathology of AD. In the current work, ChE inhibitory potential of twenty-four natural products from different chemical classes (i.e., diosgenin, hecogenin, rockogenin, smilagenin, tigogenin, astrasieversianins II and X, astragalosides I, IV, and VI, cyclocanthosides E and G, macrophyllosaponins A-D, kokusaginin, lamiide, forsythoside B, verbascoside, alyssonoside, ipolamide, methyl rosmarinate, and luteolin-7-O-glucuronide) was examined using ELISA microtiter assay. Among them, only smilagenin and kokusaginine displayed inhibitory action against AChE (IC₅₀ = 43.29 ± 1.38 and 70.24 ± 2.87 µg/mL, respectively). BChE was inhibited by only methyl rosmarinate and kokusaginine (IC₅₀ = 41.46 ± 2.83 and 61.40 ± 3.67 µg/mL, respectively). IC₅₀ values for galantamine as the reference drug were 1.33 ± 0.11 µg/mL for AChE and 52.31 ± 3.04 µg/mL for BChE. Molecular docking experiments showed that the orientation of smilagenin and kokusaginine was mainly driven by the interactions with the peripheral anionic site (PAS) comprising residues of hAChE, while kokusaginine and methyl rosmarinate were able to access deeper into the active gorge in hBChE. Our data indicate that similagenin, kokusaginine, and methyl rosmarinate could be hit compounds for designing novel anti-Alzheimer agents.     

Temporal changes of atmospheric deposition of major and trace elements in European Turkey,Thrace region

Journal of Radioanalytical and Nuclear Chemistry - In the present study, the actual levels and temporal changes of 34 major and trace elements were examined in 44 moss samples Hypnum cuppressiforme...