Stochastic collocation-based nonlinear analysis of concrete bridges with uncertain parameters

This paper focuses on the stochastic response of concrete bridges considering uncertainty in bearing and abutment stiffness. A multi-span simply supported bridge with concrete girders is selected. A 3D-dimensional model is prepared, and nonlinear response history analyses are performed. For the numerical dynamic simulation, the non-sampling stochastic method based on generalized polynomial chaos (gPC) expansion is utilised. The uncertain parameters include the vertical and shear stiffness of bearings and the lateral stiffness of abutments are presented by the truncated gPC expansions. Furthermore, the system response such as base shear, acceleration, velocity and displacement in different columns is presented by gPC expansion with unknown deterministic coefficients. The stochastic Galerkin projection is employed to calculate a set of deterministic equations. A non-intrusive solution, as a set of collocation points, determines the unknown gPC coefficients of the system response and the results are compared with Monte Carlo simulations. The key advantage of spectral discretization is the combination of the mentioned method with the spatial discretization, e.g. finite element model. This study also emphasises the accuracy in results and time efficiency of the proposed non-sampling method for uncertainty quantification of stochastic systems comparing to sampling procedure (e.g. Monte Carlo simulation).     

Preparation of AgO<Subscript>2</Subscript>/GrO nanocomposites by hydrothermal method and investigation of photoluminescence properties

This paper reports a novel processing route for producing AgO₂/GrO nanocomposites by hydrothermal method. AgO₂/GrO nanocomposites as semiconductor materials have been synthesized via a facile one-step process using AgNO₃ and glucose as starting reagents. We investigated the influence of the thermal decomposition temperature and reaction time, on the morphology and the particle size of AgO₂/GrO nanocomposites. The AgO₂/GrO nanocomposites were characterized by FT-IR, UV–Vis spectra, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. The obtained results exhibited that the synthesized nano product by calcining for 4 h showed excellent uniformity and quality.     

Immobilization of Metalloporphyrin on Functionalized MCM-48 Nanoporous Silica as a Catalyst in Oxidation of Cyclohexene: The Effects of Nanoporous Structure of MCM-48 on Its Catalytic Efficiency

MCM-48 nanoporous silica were prepared by the sol–gel method and functionalized by pyridine using a silane agent. With the aid of pyridines on the surface, the nanoporous material was used as a support for immobilization of metalloporphyrin. The formation of this material was confirmed by infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, inductively coupled plasma atomic emission spectroscopy analysis and specific surface area measurement. The application of this metalloporphyrin-immobilized MCM-48 was investigated as a heterogeneous catalyst in cyclohexene oxidation. Various parameters such as solvent and time were optimized. Also the effect of nanoporous structure on the efficiency of the catalyst was investigated by comparing the results with the same composite using nonporous silica (SiO₂). The result showed that the MCM-48 immobilized metalloporphyrin is a better catalyst for cyclohexene oxidation, which can be attributed to its nanoporous structure. The nanoporous structure increases the surface area of MCM-48 and leads to more metalloporphyrin immobilization.     

Reduction of formaldehyde emission from plywood

The aim of this work is to evaluate performances of tannin-based resins designed as adhesive in the plywood production. For this purpose, a part of phenol formaldehyde (PF) and melamine formaldehyde (MF) in the classic adhesive formulation was replaced by tannin. The physical properties of the formulated resins (rheological characterization, etc.) were measured. In order to analyze the mechanical performance of tannin-based resins, plywood panels were produced and the mechanical properties including tensile strength wood failure and three-point bending strength were investigated. The performance of these panels is comparable to those of plywood panels made by commercial PF and MF. The results showed that the plywood panels bonded with tannin–PF (PFT) and tannin–MF (MFT) resins exhibited better mechanical properties in comparison to the plywood panels made of commercials PF and MF. The introduction of small properties of tannin in PF and MF resins contribute to the improvement of the water performance of these adhesives. The formaldehyde emission levels obtained from panels bonded with tannin-based resins were lower than those obtained from panels bonded with control PF and MF. Although there are no actual reaction at all between PF, MF, and tannin, addition of tannin significantly improves the water resistance of PF and MF resins. This is a novel finding that manifests the possibility of replacing a convention PF and MF resins by tannin. Modified adhesive is one of the goals in the plywood production without changing any of their production conditions with improvement to their overall properties.     

Barium hexaferrite nanoparticles: morphology-controlled preparation,characterization and investigation of magnetic and photocatalytic properties

In this paper, barium hexaferrite (BaFe₁₂O₁₉) nanoparticles have been successfully synthesized via a simple co-precipitation route. Six chelating agents such as three amino acids (proline, alanine, aspartic acid) and three surfactants (SDBS, PVP, and EDTA) were used. The result showed that the amino acids decrease the particle size and the best result was observed for alanine. Besides, the photocatalyst activity of as-prepared BaFe₁₂O₁₉ nanoparticles was evaluated by degradation of methyl orange under visible light irradiation (λ?>?400 nm). The degradation rates of the methyl orange were measured to be as high as 95% in 200 min. The nanoparticles were also characterized by several techniques including FT-IR, XRD, SEM, and VSM. The VSM measurement showed a saturation magnetization value (Ms) of 30 emu/g.     

Synthesis of ZnFe2O4 Nanoparticles Confined Within Nanoporous Silica Using Trinuclear Oxo-centered Complex: Inorganic Complexes as a Precursor for the Preparation of Magnetic Nanoporous Silica

MCM-48 Nanoporous silica (Mobil Composition of Matter, #48) was synthesized and functionalized by pyridine groups. The formation of this functionalized nanoporous silica was confirmed by elemental analysis, low angle x-ray powder diffraction and N₂ adsorption. The trinuclear oxo-centered Fe₂Zn(μ₃-O)(CF₃COO)₆(H₂O)₃ cluster was synthesized and immobilized inside the pyridine functionalized MCM-48 pores. The immobilization of this cluster was confirmed by IR spectroscopy and flame atomic adsorption spectroscopy. Fe₂ZnO₄ nanoparticles were confined within the nanoporous silica pores by thermolysis of the immobilized Fe₂Zn(μ₃-O)(CF₃COO)₆(H₂O)₃ cluster and were characterized by high angle X-ray powder diffraction and high resolution transmission electron microscopy. This method is suitable for the one-pot preparation of Fe₂ZnO₄ confined nanoporous silica.     

Geotechnical characteristics of Bakhtiary dam site,SW Iran: the highest double-curvature dam in the world

The Bakhtiary Hydropower Project with a 325 m high dam will be constructed on Bakhtiary River, in southwest Iran. The main dam has been designed as a double-curvature concrete structure which will be the highest one of its type in the world. Geologically, the dam site is located on siliceous limestone of the Sarvak Formation in the northwestern part of the folded Zagros. A large number of complicated geological structures in the study area, such as folding and duplex structure, faults, chevron folds, kink band zones as well as joint and fracture systems, raised concerns regarding the acceptability of the site for such a monumental dam. To create a comprehensive geotechnical model of the dam site and appurtenant structures, very extensive surface and subsurface investigations were carried out, including core drilling, water pressure testing, driving exploratory galleries for engineering geological mapping, a rock mass discontinuity survey and in situ rock mechanical tests. This research applies the results of the engineering geological and geotechnical investigations to define the geomechanical model of the dam site enabling options to be considered to achieve a safe dam design. The investigations show the rock mass of the dam site area is intersected by four main discontinuities namely, the bedding plane(s) of the rock mass and three major joint sets. Water pressure tests provide data about the permeability of the rock mass which is significantly dependant on the joint properties and the geological structures. These parameters, set the criteria for the design of the grout curtain at the dam foundation. The rock mass classification of the dam site was determined mainly based on the gallery survey and core logging using the rock mass rating, geological strength index (GSI) and Q system. Six classes of rock mass qualities were distinguished which show a fair to good rock mass at the dam foundation. From the plate load test results, a site-specific correlation was developed for estimating the modulus of deformation of the rock masses using GSI value. The estimated engineering geological and geotechnical parameters at the dam site are generally favorable and suitable for the safe design of the Bakhtiary arch dam with a height of 325 m.