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A novel structural modification to eliminate the early coupling between bending and torsional mode shapes in a cable stayed bridge

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Frontiers of Structural and Civil Engineering 2017年第2期11卷 131-142页

作者： nazim Abdul NARIMAN Institute of Structural Mechanics Faculty of Civil Engineering Bauhaus University Weimar Weimar 99423 Germany

In this paper, a novel structural modification approach has been adopted to eliminate the early coupling between the bending and torsional mode shapes of vibrations for a cable stayed bridge model generated using ABAQUS software. Two lateral steel beams are added to the middle span of the structure. Frequency analysis is dedicated to obtain the natural frequencies of the first eight mode shapes of vibrations before and after the structural modification approach. Numerical simulations of wind excitations are conducted for the 3D model of the cable stayed bridge with duration of 30 s supporting on real data of a strong wind from the literature. Both vertical and torsional displacements are calculated at the mid span of the deck to analyze both the bending and the torsional stiffness of the system before and after the structural modification. The results of the frequency analysis after applying lateral steel beams declared a safer structure against vertical and torsional vibrations and rarely expected flutter wind speed. Furthermore, the coupling between the vertical and torsional mode shapes has been removed to larger natural frequencies magnitudes with a high factor of safety. The novel structural approach manifested great efficiency in increasing vertical and torsional stiffness of the structure.

关键词： aeroelastic instability structural damping flutter wind speed bending stiffness torsional stiffness

Influence of fluid-structure interaction on vortex induced vibration and lock-in phenomena in long span bridges

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Frontiers of Structural and Civil Engineering 2016年第4期10卷 363-384页

作者： nazim Abdui NARIMAN Institute of Structural Mechanics Faculty of Civil Engineering Bauhaus University Weimar Weimar 99423 Germany

In this paper, deck models of a cable stayed bridge are generated in ABAQUS-finite element program once using only CFD model （one-way fluid-structure interaction） and another by using both the CFD model and the CSD model together （two-way fluid-structure interaction） in a co-simulation. Shedding frequencies for the associated wind velocities in the lock-in region are calculated in both approaches. The results are validated with Simiu and Scanlan results. The lift and drag coefficients are determined for the two approaches and the latter results are validated with the flat plate theory results by Munson and coauthors. A decrease in the critical wind velocity and the shedding frequencies considering two-way approach was determined compared to those obtained in the one-way approach. The results of the lift and drag forces in the two-way approach showed appreciable decrease in their values. It was concluded that the two-way approach predicts earlier vortex induced vibration for lower critical wind velocities and lock-in phenomena will appear at lower natural frequencies of the long span bridges. This helps the designers to efficiently plan and consider for the design and safety of the long span bridge against this type of vibration.

关键词： vortex-induced vibration fluid-structure interaction Strouhal number lock-in kinetic energy

DEFPOS Hα observations of the W80 Complex

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Research in Astronomy and Astrophysics 2013年第5期13卷 547-556页

作者： nazim Aksaker Vocational School of Technical Sciences University of C ukurova Research and Application of Space Sciences and Solar Energy Center (UZAYMER) University of Cukurova

We present Hα emission line measurements of the W80 nebula complex. A total of 26 regions have been observed inside the nebula with the Dual Etalon Fabry- Perot Optical Spectrometer system at the f/48 Coud6 focus of the 150 cm RTT150 telescope located at TUBITAK National Observatory in Antalya, Turkey. The inten- sities, local standard of rest velocities, heliocentric radial velocities and linewidths for full width at half maximum of the Hα emission lines have been determined from these observations. They lie in the range of 259 to 1159 Rayleigh （R; 1R = 106/47r pho- tons cm-2 sr-1 S-1 = 2.41 × 10-7 erg cm-2 sr-1 S-1 at Ha）, 4 to 12 km s-1, -3 to -11 km s-1 and 44 to 55 km s-i, respectively. The radial velocity measurements show that there are several maxima and minima inside W80. The new results confirm findings in the literature that the complex seems to be rather uniform in terms of radial velocity and no turbulent motion is seen inside the complex. The average value of the calculated emission measure for the region is 3.1 pc cm-6.

关键词： instrumentation: interferometers -- ISM: H II regions -- techniques:radial velocities -- techniques: interferometric

Thermal fluid-structure interaction and coupled thermal-stress analysis in a cable stayed bridge exposed to fire

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Frontiers of Structural and Civil Engineering 2018年第4期12卷 609-628页

作者： nazim Abdul NARIMAN Institute of Structural Mechanics Faculty of Civil EngineeringBauhaus Universitat WeimarMarienstrasse 1599423WeimarGermany

In this paper, thermal fluid structure-interaction (TFSI) and coupled thermal-stress analysis are utilized to identify the effects of transient and steady-state heat-transfer on the vortex induced vibration and fatigue of a segmental bridge deck due to fire incidents. Numerical simulations of TFSI models of the deck are dedicated to calculate the lift and drag forces in addition to determining the lock-in regions once using fluid-structure interaction (FSI) models and another using TFSI models. Vorticity and thermal convection fields of three fire scenarios are simulated and analyzed. Simiu and Scanlan benchmark is used to validate the TFSI models, where a good agreement was manifested between the two results. Extended finite element method (XFEM) is adopted to create 3D models of the cable stayed bridge to simulate the fatigue of the deck considering three fire scenarios. Choi and Shin benchmark is used to validate the damaged models of the deck in which a good coincide was seen between them. The results revealed that TFSI models and coupled thermal-stress models are significant in detecting earlier vortex induced vibration and lock-in regions in addition to predicting damages and fatigue of the deck due to fire incidents.

关键词： fire scenario transient heat transfer TFSI model coupled thermal-stress XFEM

Control efficiency optimization and Sobol＇s sensitivity indices of MTMDs design parameters for buffeting and flutter vibrations in a cable stayed bridge

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Frontiers of Structural and Civil Engineering 2017年第1期11卷 66-89页

作者： nazim Abdul NARIMAN Institute of Structural Mechanics School of Civil Engineering Bauhaus University Weimar Weimar 99423 Germany

This paper studies optimization of three design parameters （mass ratio, frequency ratio and damping ratio） of multiple tuned mass dampers MTMDs that are applied in a cable stayed bridge excited by a strong wind using minimax optimization technique. ABAQUS finite element program is utilized to run numerical simulations with the support of MATLAB codes and Fast Fourier Transform FFT technique. The optimum values of these three parameters are validated with two benchmarks from the literature, first with Wang and coauthors and then with Lin and coauthors. The validation procedure detected a good agreement between the results. Box-Behnken experimental method is dedicated to formulate the surrogate models to represent the control efficiency of the vertical and torsional vibrations. Sobol＇s sensitivity indices are calculated for the design parameters in addition to their interaction orders. The optimization results revealed better performance of the MTMDs in controlling the vertical and the torsional vibrations for higher mode shapes. Furthermore, the calculated rational effects of each design parameter facilitate to increase the control efficiency of the MTMDs in conjunction with the support of the surrogate models.

关键词： MTMDs power spectral density fast Fourier transform minimax optimization technique Sobol's sensitivityindices Box-Behnken method

Uncertainty quantification of stability and damage detection parameters of coupled hydrodynamic-ground motion in concrete gravity dams

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Frontiers of Structural and Civil Engineering 2019年第2期13卷 303-323页

作者： nazim Abdul NARIMAN Tom LAHMER Pevman KARAMPOUR Institute of Structural Mechanics Faculty of Civil EngineeringBauh aus Universitat Weimar99423 WeimarGermany Department of Mechanical Engineering Faculty of EngineeringArak UniversityArak 38156-8-8849Iran

In this paper, models of the global system of the Koyna dam have been created using ABAQUS software considering the dam-reservoir-fbundation interaction. Non coupled models and the coupled models were compared regarding the horizontal displacement of the dam crest and the differential settlement of the dam base in clay foundation. Meta models were constructed and uncertainty quantification process was adopted by the support of Sobol's sensitivity in dices considering five un certain parameters by exploiting Box-Behnken experimental method. The non coupled models results determined overestimated predicted stability and damage detection in the dam. The rational effects of the reservoir height were very sensitive in the variation of the horizontal displacement of the dam crest with a small interaction effect with the beta viscous damping coefficient of the clay fbundation. The modulus of elasticity of the clay foundation was the decisive parameter regarding the variation of the differential settlement of the dam base. The XFEM approach has been used for damage detection in relation with both minimum and maximum values of each uncertain parameter. Finally the effects of clay and rock foundations were determined regarding the resistance against the propagation of cracks in the dam, where the rock fbundation was the best.

关键词： massed foundation hydrodynamic pressure Box-Behnken method meta model Sobol's sensitivity indices

Biofilter:a promising tool for mitigating methane emission from manure storage

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Journal of Arid Land 2011年第1期3卷 61-70页

作者： nazim CICEK Danny MANN Department of Biosystems Engineering University of Manitoba

Liquid manure storage may contribute to methane （CH4） emission and this emission can be greatly reduced if appropriate management practices are applied. Biofiltration has been used in other fields for mitigating greenhouse gas （GHG） emission （e.g., landfill） and shown promise for mitigation OH4 emis- sion from liquid manure storage. It has been reported that biofilter was capable of reducing 80% of CH4 emissions from manure storage. The OH4 removal efficiency is influenced by many factors, including OH4 and 02 concentrations, temperature, moisture, composition of the filter bed, nutrient, and empty bed resi- dency time （EBRT）. Biological conversion of methane of a biofilter is a slow process due to the low water solubility of methane. The residence times （EBRT） between 5 min and 5 h have been used, whereas a typical EBRT of 25 s is used for common biofilter applications. Temperature at which methanotrophic bac- teria are active ranges from 10℃ to 45℃. The maximum activity is found at around 30℃. The optimal filter bed water content depends on both the gas flow rate and the type of filter bed （soil, compost, etc.） and ranges from 30%-70% of the water holding capacity. Compost is the best material for filter bed. The optimal pH for methanotrophic bacteria is neutral to slightly acidic. Copper and nitrogen compounds especially nitrate are important nutrients to methanotrophic bacteria but their optimal concentrations have not been founded. Phosphorus and other elements such as potassium and manganese are reported to affect the performance of methanotrophic bacteria but need further confirmation.

关键词： biofilter greenhouse gas methane manure storage

Hα measurements using DEFPOS/RTT150 Telescope: Instrumentation and observations

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Chinese Journal of Astronomy and Astrophysics 2009年第2期9卷 237-248页

作者： Muhittin Sahan Ilhami Yegingil nazim Aksaker Department of Techinical Programs Vocational School of Osmaniye University of Osmaniye KorkutAta 80000 Osmaniye Turkey Sultan Qaboos University Department of Physics College of Science 123 Al-Khodh Muscat Oman Department of Physics ukurova University 01330 Adana Turkey

To investigate the physical properties of HII regions and some PNe about 4＇ in size, a DEFPOS Fabry-Perot spectrometer has been redesigned and set up at the coude exit of the 150cm RTT150 telescope （f/48） at TUBITAK National Observatory （Antalya/Baklrhtepe, Turkey）. The spectrometer has a 4＇ circular field of view and a velocity resolution of 27.27 km s^-1 （a spectral resolving power of 11000） over a 200 km s^-1 spectral window near Hα. This work presents the details of the newly redesigned instrument for coude observations, the data reduction techniques and finally presents some physical results of our new Hα observations selected from the Reynolds et al. （2005） and Fich et al. （1990） papers. The DEFPOS system has been fully tested and the first observations of HII regions and PNe in the Galaxy are used to illustrate the power of the instrument. We feel that our first Fabry-Perot observations can provide a powerful tool for the study of objects with small angular size. In the future, we are planning to prepare a catalog including some physical properties such as radial velocity, line width, and intensity of some PNe and HII regions close to the 4＇ field of view.

关键词： instrumentation adaptive optics, interferometers -- methods data analy- sis -- ISM HII regions, planetary nebulae general -- techniques spectroscopic, radial velocities

Network Lifetime Global Optimization for Multi-Source and Single-Sink Topology in Wireless Sensor Networks

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Journal of Shanghai Jiaotong university(Science) 2009年第2期14卷 195-203页

作者：王晖吴迪 AGOULMINE nazim 马懋德 Networks and Multimedia Systems Research Group(LRSM) ENSIIE University of Evry School of Electronic Information and Electrical EngineeringShanghai Jiaotong University School of Electric and Electronic Engineering Nanyang Technological University

The multi-source and single-sink(MSSS) topology in wireless sensor networks(WSNs) is defined as a network topology,where all of nodes can gather,receive and transmit data to the *** energy-constrained WSNs with such a topology,the joint optimal design in the physical,medium access control(MAC) and network layers is considered for network lifetime maximization(NLM).The problem of integrating multi-layer information to compute NLM,which involves routing flow,link schedule and transmission power,is formulated as a nonlinear optimization *** under time division multiple access(TDMA) scheme,this problem can be transformed into a convex optimization *** solve it analytically we make use of the property that local optimization is global optimization in convex *** allows us to exploit the Karush-Kuhn-Tucker (KKT) optimality conditions to solve it and obtain analytical solution expression,i.e.,the globally optimal network lifetime(NL).NL is derived as a function of number of nodes,their initial energy and data rate arrived at them. Based on the analysis of analytical approach,it takes the influence of data rates,link access and routing method over NLM into ***,the globally optimal transmission schemes are achieved by solution set during analytical approach and applied to algorithms in TDMA-based WSNs aiming at NLM on OMNeT++ to compare with other suboptimal schemes.

关键词： multi-source and single-sink (MSSS) topology network lifetime cross-layer optimization Karush- Kuhn-Tucker (KKT) optimality conditions global optimization analytical solution