Structural health monitoring system of the long-span bridges in Turkey

Abstract

This study presents the general features of the structural health monitoring (SHM) system of the long-span cable-supported bridges in Turkey, namely the First Bosphorus Bridge, the Second Bosphorus Bridge (Fatih Sultan Mehmet Bridge), the newly constructed the Third Bosphorus Bridge (Yavuz Sultan Selim) and the Osman Gazi Bridge (Izmit Bay Bridge). Due to the critical function of the bridges in the transportation networks of Istanbul, structural health under extreme and operational load cases without interruption of their operation is essential. The SHM systems are already available and in use for the First and Second Bosphorus Bridges; however, the Yavuz Sultan Selim and the Osman Gazi Bridges, only have the preliminary SHM systems established. General preferences of the current and planned SHM systems of the bridges are given based on the monitoring objectives and requirements. Data collected from the SHM systems are also exhibited as an illustration for structural modal identification of the First Bosphorus Bridge. Based on the experiences from the current SHM systems, future works and planning are recommended to effectively design new SHM system and to efficiently update the current ones.     

Toxicity and mutagenicity assessment of a boron mine drainage water

This study was aimed to assess toxicity of boron mine drainage (BMD) water in K?rka borough of Turkey, which is one of the most important boron deposit sites in the world. Three complementary tests were done to assess the toxicity of BMD water. Root growth inhibition tests showed that EC₅₀ value of BMD water sample was approximately 3.85% of concentration. Furthermore, mutagenicity was analysed utilising Ames Salmonella Mutagenicity Test and Muta‐ChromoPlate kit system (Environmental Biodetection Products Inc., Ontario, Canada). Salmonella typhimurium TA 98 strain for all concentrations and Salmonella typhimurium TA100 strain for the highest concentrations of BMD water in the absence of metabolic activation significantly stimulated mutagenic activity and increased the numbers of revertant colonies for several concentrations compared to spontaneous revertant colonies. RAPD‐PCR result and the polymorphism percentage proved that the effect of boron contamination was seen on DNA level.     

An Experimental Investigation on the Chemical Stability of Selected Formation and Determination of the Proper Type of Water-Base Drilling Fluids. Part 2. Test Results

The objective of this study was to select the proper drilling fluid type and composition for drilling stable holes through the problems of the selected formations. This study was performed on shale samples taken from 10 wells in which hole instability was encountered to various extents during drilling the Germav formation. Both ionic and polymer inhibitions were utilized in formulating the proper drilling for the Germav formation. Ionic inhibition was obtained using KCl and NaCl. Polyanionic polymer (Pac-L) was used for providing the polymer encapsulation. Experimental results indicated that KCl is superior to NaCl in providing ionic inhibition. Both salts lowered the interaction between the drilling fluid and Germav formation, but better results were obtained with KCl. Minimum salt concentration up to 15% yields more inhibitive environment. Polymer inhibition tests indicated that minimum Pac-L concentration required for maintaining the polymer inhibition was about 2 lb/bbl for both systems. In conclusion, KCl/encapsulating polymer system seems to be the most proper water: base drilling fluid available for Germav formation achieving the required wellbore stability. The fluid loss and suspending properties of the proposed system must be controlled using the modified starch and XC polymer.     

Effects of sheet thickness and anisotropy on forming limit curves of AA2024-T4

In this study, the effects of sheet thickness and anisotropy of AA2024-T4 on forming limit curve (FLC) are experimentally investigated according to ISO 12004-2 standard. A new limit strain measurement method is proposed by using the grid analysis method so as to determine limit strains conveniently and reliably. In addition to the regular test specimens, various widths are added to enhance the FLC’s accuracy at the plane strain condition (PSC). The accuracy and reliability of the proposed method are verified for different materials. Results illustrate that an increase in the sheet thickness increases the FLC level. The additional experiments for additional widths improve the accuracy of the FLC at the PSC, and the position of the lowest major strain value differs from the literature. However, the effect of anisotropy on the FLC is found to be insignificant. Finally, experimental and numerical case studies are carried out for conventional deep drawing, stretch drawing, and hydraulic bulge processes. Results reveal that different FLCs are necessary for different thicknesses for accurate predictions.     

Distributions of environmentally hazardous elements in the Tertiary oil shale deposits from NW Anatolia,Turkey: A statistical analysis

The environmentally hazardous element concentrations (As, Cd, Cr, Cu, Hg, Mn, Pb, S, and Zn) and element–organic matter relations of the oil shale deposits in six different fields in NW Anatolia, Turkey, were investigated and the characteristics of fields were compared. The enrichment factor (EF) for most of the trace elements in the studied oil shales generally show enrichment patterns for all the fields. Only Cr, Hg, and Pb for oil shale samples from the Bahçecik field samples and Hg for oil shale samples from the Gölpazar? field samples are depleted. Arsenic in the Bahçecik field samples and Hg in the Himmeto?lu field samples are neither depleted nor enriched. The lowest and highest element enrichments in these fields are determined to be Hg and S, respectively. In general, all elements have high concentrations in the Beypazar? and Seyitömer fields and low concentrations in the Himmeto?lu, Bahçecik, and Gölpazar? (except for As) fields. A positive correlation at significance level of p ≤ 0.05 was observed for total organic carbon content with Cd in four of the fields, with Cu and S in two fields and with Cr, Mn, and Zn in only one field.     

Using exergy for performance evaluation of a conceptual ramjet engine burning hydrogen fuel

Ramjet engines are widely-used devices in the defence industry and have military applications. These engine types, preferred in many fields, are known to act according to the laws of thermodynamics. For this reason, exergy analysis methodology is a beneficial tool for assessing the performance of a ramjet engine, as well as other energy conversion systems. The present study aims to introduce a performance analysis of a hydrogen fueled ramjet engine within the framework of the first and second laws of thermodynamics. At the end of the study, the exergy efficiencies of inlet, combustion zone and nozzle are found to be 3.88%, 7.62%, and 0.03%, respectively, whereas the exergy efficiency of a ramjet engine is 8.85%. The introduced methodology and the results obtained from the current study may be useful for anybody who is interested in thermal sciences and aero-propulsion technologies.     

Experimental investigation and analysis of a new photoelectrochemical reactor for hydrogen production

In this research paper, an experimental investigation of photoactive material titanium dioxide (TiO₂) coated on 180 cm² 316 stainless steel anode is undertaken to study the photoresponse on photoelectrochemical (PEC) hydrogen production. The TiO₂ nanoparticles are first prepared via sol-gel method. A large surface 316 stainless steel anode is coated with TiO₂ nanoparticles by a dip coating apparatus at a withdraw rate of 2.5 mm/s. The nanoparticles are carried on the stainless steel substrate by two-step annealing procedure. The potentiostatic studies confirm the photoactivity of TiO₂ nanoparticles in a photoelectrochemical reactor when exposed to solar ultraviolet (UV) light. The photon to current efficiency measurements carried out on the PEC reactor with TiO₂ coated large surface stainless steel as photoanode demonstrate a significant increase of photoresponse in UV light compared to the uncoated stainless steel prepared under similar conditions. Upon illumination at a power density of 600 W/m², the hydrogen production is observed in TiO₂ coated stainless steel substrate at a measured rate of 51 ml/h while no illumination conditions show a production rate of 42 ml/h. In comparative assessments, the TiO₂ coated substrate shows an increase in photocurrent of 10 mA with an energy efficiency of 1.32% and exergy efficiency of 3.42% at an applied potential of 1.6 V. The present results show a great potential for titanium nanoparticles semiconductor metal oxide in photoelectrochemical hydrogen production application.     

The vibration and buckling of freely supported non-homogeneous orthotropic conical shells subjected to different uniform pressures

The paper examines the vibration and stability of freely supported orthotropic truncated and complete conical shells with non-homogeneous material properties under uniform lateral and hydrostatic pressures. First, the basic relations have been obtained for orthotropic truncated conical shells, Young's moduli and density which vary continuously in the thickness direction. By applying the Galerkin method, the buckling pressures and lowest cyclic frequencies of truncated and complete conical shells are obtained. To verify the accuracy of the results, comparisons are made with results available in the open literature. This study also examines in detail the effects of the variations of conical shell characteristics, the effects of the non-homogeneity and the orthotropy on the critical pressures and lowest cyclic frequencies of truncated and complete conical shells.     

Some physical properties of ZnO thin films prepared by RF sputtering technique

ZnO thin films were deposited with RF sputtering using pure Zn target. In order to generate oxidation process of Zn, Ar:O₂ gas mixing in (9:1), (7:3) and (5:5) ratios of Ar:O₂ was used. To characterize ZnO thin films thickness and transparency were measured using optical method, and refractive index and band gap energies were calculated. Electrical conductivity of the ZnO thin films was also determined. AFM images were used to determine surface morphology of produced ZnO thin films.