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Multiple damage detection in complex bridges based on strain energy extracted from single point measurement

Frontiers of Structural and Civil Engineering 2020年第3期14卷 722-730页

作者： Alireza ARABHA NAJAFABADI Farhad DANESHJOO hamid Reza ahmadi Department of Structural Engineering RoadHousing&Urban Development Research CenterTehran 13145-1696Iran Department of Structural Engineering Faculty of Civil and Environmental EngineeringTarbiat Modares UniversityTehran 14115-397Iran Department of Civil Engineering Faculty of EngineeringUniversity of MaraghehMaragheh 55136-553Iran

Strain Energy of the structure can be changed with the damage at the damage *** accurate detection of the damage location using this index in a force system is dependent on the degree of accuracy in determining the structure deformation function before and after *** use of modal-based methods to identify damage in complex bridges is always associated with problems due to the need to consider the effects of higher modes and the adverse effct of operational conditions on the extraction of structural modal *** this paper,the deformation of the structure was determined by the concept of influence line using the Betti-Maxwell *** two damage detection indicators were developed based on strain energy *** indices were presented separately for bending and torsion *** element analysis of a five-span concrete curved bridge was done to validate the stated *** was simulated by decreasing stiffness at different sections of the *** response regarding displacement ofa point on the deck was measured along each span by passing a moving load on the bridge at very low *** of the strain energy extracted from displacement influence line and the strain energy extracted from the rotational displacement influence line(SERIL)were calculated for the studied *** results show that the proposed methods have well identified the location of the damage by significantly reducing the number of sensors required to record the ***,the location of symmetric damages is detected with high resolution using SERIL.

关键词： damage detection strain energy infuence line complex bridges rotation displacement

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A low-power and low-energy flexible GF(p) elliptic-curve cryptography processor

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Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第9期11卷 724-736页

作者： hamid Reza ahmadi Ali AFZALI-KUSHA School of Electrical and Computer Engineering University of Tehran

We investigate the use of two integer inversion algorithms,a modified Montgomery modulo inverse and a Fermat's Little Theorem based inversion,in a prime-field affine-coordinate elliptic-curve *** perform this,we present a low-power/energy GF(p) affine-coordinate elliptic-curve cryptography(ECC) processor design with a simplified architecture and complete flexibility in terms of the field and curve *** design can use either of the inversion *** on the implementations of this design for 168-,192-,and 224-bit prime fields using a standard 0.13 μm CMOS technology,we compare the efficiency of the algorithms in terms of power/energy consumption,area,and calculation *** results show that while the Fermat's theorem approach is not appropriate for the affine-coordinate ECC processors due to its long computation time,the Montgomery modulo inverse algorithm is a good candidate for low-energy *** results also show that the 168-bit ECC processor based on the Montgomery modulo inverse completes one scalar multiplication in only 0.4 s at a 1 MHz clock frequency consuming only 12.92 μJ,which is lower than the reported values for similar designs.

关键词： Elliptic-curve cryptography(ECC) Prime field Montgomery multiplication Montgomery inverse Low-energy

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Static behavior of offshore two-planar tubular KT-joints under axial loading at fire-induced elevated temperatures

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Journal of Ocean Engineering and Science 2019年第4期4卷 352-372页

作者： Neda Azari-Dodaran hamid ahmadi Faculty of Civil Engineering University of TabrizTabriz ***Iran

A total of 540 nonlinear steady-state finite element analyses were performed to study the influence of temperature and dimensionless geometrical parameters(β,γ,θ,andτ)on the ultimate strength,failure modes,and initial stiffness of two-planar tubular *** joints were analyzed under two types of axial loading and five different temperatures(20℃,200℃,400℃,550℃,and 700℃).So far,there has not been any equation available for calculating the ultimate strength of two-planar tubular KT-joints at elevated ***,after parametric study,a set of design formulas were developed through nonlinear regression analyses,to calculate the ultimate strength of two-planar tubular KT-joints subjected to axial loading at elevated temperatures.

关键词： Ultimate strength Two-planar tubular KT-joint Axial loading Elevated temperatures Parametric equation

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Investigation on the Effect of Geometrical and Geotechnical Parameters on Elongated Offshore Piles Using Fuzzy Inference Systems

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China Ocean Engineering 2017年第3期31卷 378-388页

作者： Ali AMINFAR Alireza MOJTAHEDI hamid ahmadi Mohammad Hossain AMINFAR Civil Engineering Department Islamic Azad UniversityTabriz Branch Faculty of Civil Engineering University of Tabriz

Among numerous offshore structures used in oil extraction, jacket platforms are still the most favorable ones in shallow waters. In such structures, log piles are used to pin the substructure of the platform to the seabed. The pile＇s geometrical and geotechnical properties are considered as the main parameters in designing these structures. In this study, ANSYS was used as the FE modeling software to study the geometrical and geotechnical properties of the offshore piles and their effects on supporting jacket platforms. For this purpose, the FE analysis has been done to provide the preliminary data for the fuzzy-logic post-process. The resulting data were implemented to create Fuzzy Inference System （FIS） classifications. The resultant data of the sensitivity analysis suggested that the orientation degree is the main factor in the pile＇s geometrical behavior because piles which had the optimal operational degree of about 5° arc more sustained. Finally, the results showed that the related fuzzified data supported the FE model and provided an insight for extended offshore pile designs.

关键词： pile soil FEM offshore jacket platform pile-soil interaction, ^-logic fuzzification

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Parametric Study on the Effects of Pile Inclination Angle on the Response of Batter Piles in Offshore Jacket Platforms

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Journal of Marine Science and Application 2016年第2期15卷 193-200页

作者： Ali Aminfar hamid ahmadi Mohammad Hossein Aminfar Department of Civil Engineering Tabriz Branch Islamic Azad University Pasdaran Highway Tabriz *** Iran Faculty of Civil Engineering University of Tabriz 29 Bahman Blvd. Tabriz *** Iran

Offshore jacket-type platforms are attached to the seabed by long batter piles. In this paper, results from a finite element analysis, verified against experimental data, are used to study the effect of the pile＇s inclination angle, and its interaction with the geometrical properties of the pile and the geotechnical characteristics of the surrounding soil on the behavior of the inclined piles supporting the jacket platforms. Results show that the inclination angle is one of the main parameters affecting the behavior of an offshore pile. We investigated the effect of the inclination angle on the maximum von Mises stress, maximum von Mises elastic strain, maximum displacement vector sum, maximum displacement in the horizontal direction, and maximum displacement in the vertical direction. Results indicate that the pile＇s operationally optimal degree of inclination is approximately 5°. By exceeding this value, the instability in the surrounding soil under applied loads grows extensively in all the geotechnical properties considered. Cohesive soils tend to display poorer results compared to grained soils.

关键词： pile batter pile inclination angle finite element analysis offshore jacket platform pile-soil interaction settlement offshore piles

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新型吡咯烷键合反相高效液相色谱固定相的制备与研究（英文）

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色谱 2017年第11期35卷 1120-1128页

作者： Elahe NAGHDI Kourosh TABAR HEYDAR Ali SHARIFI Seyyed hamid ahmadi Chemistry and Chemical Engineering Research Center of Iran

A new ionic liquid-based high-performance liquid chromatography stationary phase is reported.A derivative of N-methyl pyrrolidinium tetrafluoroborate was covalently immobilized on the surface of silica particles to prepare silica-based N-methyl pyrrolidinium tetrafluoroborate(SilprMP BF4)stationary *** obtained ionic liquid-modified silica was evaluated and confirmed by elemental analysis,infrared spectroscopy,and thermogravimetric analysis.A column was packed with the modified *** retention behavior of aromatic compounds,alkyl benzenes,and acidic and basic compounds on the SilprMP BF4 stationary phase was studied under reversed-phase liquid chromatography *** effect of the eluent pH on the separation of the acidic and basic compounds was also *** new stationary phase involves multiple retention mechanisms,such as electrostatic,hydrophobic,ion-dipole,and anion-exchange interactions,which might lead to multipurpose separation media.

关键词： reversed-phase high-performance liquid chromatography stationary phase ionic liquids (ILs) pyrrolidinium

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Stress Concentration Factors at Saddle and Crown Positions on the Central Brace of Two-Planar Welded CHS DKT-connections

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Journal of Marine Science and Application 2012年第1期11卷 83-97页

作者： hamid ahmadi Mohammad Ali Lotfollahi-Yaghin Mohammad H. Aminfar Faculty of Civil Engineering University of TabrizTabriz 51664Iran

A set of parametric stress analyses was carried out for two-planar tubular DKT-joints under different axial loading conditions. The analysis results were used to present general remarks on the effects of the geometrical parameters on stress concentration factors （SCFs） at the inner saddle, outer saddle, and crown positions on the central brace. Based on results of finite element （FE） analysis and through nonlinear regression analysis, a new set of SCF parametric equations was established for fatigue design purposes. An assessment study of equations was conducted against the experimental data and original SCF database. The satisfaction of acceptance criteria proposed by the UK Department of Energy （UK DoE） was also checked. Results of parametric study showed that highly remarkable differences exist between the SCF values in a multi-planar DKT-joint and the corresponding SCFs in an equivalent uni-planar KT-joint having the same geometrical properties. It can be clearly concluded from this observation that using the equations proposed for uni-planar KT-connections to compute the SCFs in multi-planar DKT-joints will lead to either considerably under-predicting or over-predicting results. Hence, it is necessary to develop SCF formulae specially designed for multi-planar DKT-joints. Good results of equation assessment according to UK DoE acceptance criteria, high values of correlation coefficients, and the satisfactory agreement between the predictions of the proposed equations and the experimental data guarantee the accuracy of the equations. Therefore, the developed equations can be reliably used for fatigue design of offshore structures.

关键词： offshore jacket structure multi-planar tubular DKT-joint fatigue hot-spot stress method stressconcentration factor (SCF)

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Recent progresses in dry gas polymeric filters

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Journal of Energy Chemistry 2021年第11期30卷 103-119,I0003页

作者： Samaneh Bandeh Ali hamid Ghasemi Reyhaneh ahmadi Ali Ghaffari Department of Chemical Engineering Faculty of EngineeringArak UniversityArak 38156-8-8349Iran Department of Mechanical Engineering Arak University of TechnologyArak38181-41167Iran Department of Mechanical Engineering Iran University of Science and TechnologyTehranIran

Filtration and membrane separation are popular methods in gas separation since they are cost and energy efficient. Despite to air filters, there are comparatively few studies on dry gas filters, particularly at industrial scale. In fact, major unsolved challenges such as high efficiency, low pressure drop, long-term stability, high-thermal and chemical stability and advanced physiochemical properties, are still remained. The aim of this review is to scrutinize the advanced scientific and technological practices (such as selection of appropriate polymeric materials and additives, nanotechnology, modification techniques and preparation methods) towards design and fabrication of an efficient filter media for solid particles removal from the natural gas flow. Recent progresses in solid particle separation mechanisms, modeling and simulation techniques and the effect of membrane fabrication methods on its performance, strategies for modification of filter media, current challenges and future perspective are discussed.

关键词： Filtration Solid particle separation Dry gas filter Membrane Nanotechnology

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Nanostructured Carbide-Free Bainite Formation in Low Carbon Steel

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Acta Metallurgica Sinica(English Letters) 2020年第12期33卷 1635-1644页

作者： hamid Mousalou Sasan Yazdani Naghi Parvini ahmadi Behzad Avishan Faculty of Materials Engineering Sahand University of TechnologyP.O.Box:51335/1996TabrizIran Department of Materials Engineering Azarbayan Shahid Madani UniversityTabrizIran

It is an important challenge to reduce the carbon content in nanostructured bainitic steels for commercialization purposes while still being able to gain the desired microstructural characteristics in nanoscale and not to deteriorate the strength–ductility *** is the point at which an appropriate heat treatment procedure design would be an important *** article aims to investigate how to obtain nanostructured bainite in steel with 0.26 wt%carbon content by applying multi-step austempering ***-,two-and three-step austempering processes have been implemented,and proper heat treatment temperatures and approaches were selected based on dilatometry *** indicated that it has become possible to achieve bainitic ferrites and austenite fi lms with overall thicknesses of 164,145 and 132 nm and 134,105 and 90 nm at the end of one-,two-and three-step austempering heat treatments,***,microstructural characteristics resulted in enhanced mechanical properties with ultimate tensile strength(UTS)of 1435,1455 and 1428 MPa in combination with elongation levels of 15.4,13.6 and 11.4%after implementing those heat ***,it has been shown that applying the multi-step austempering heat treatments resulted in enhanced yield strength and impact toughness values due to the microstructural characteristics and proper heat treatment procedure design.

关键词： Bainite Multi-step austempering Austenite Mechanical properties Impact toughness

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An investigation on the ground motion parameters and seismic response of underground structures

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Earthquake Science 2012年第3期25卷 253-261页

作者： hamid Reza Nejati Morteza ahmadi hamid Hashemolhosseini Rock Mechanics Department School of Engineering Tarbiat Modares University Tehran 14117-13116 Iran Mining Engineering Department Isfahan University of Technology Isfahan 84156-83111 Iran

Peak ground acceleration (PGA), frequency content and time duration are three fundamental parameters of seismic loading. This study focuses on the seismic load frequency and its effect on the underground structures. Eight accelerograms regarding different occurred earthquakes that are scaled to an identical PGA and variation of ground motion parameters with ratio of peak ground velocity (PGV) to PGA, as a parameter related to the load frequency, are considered. Then, concrete lining response of a circular tunnel under various seismic conditions is evaluated analytically. In the next, seismic response of underground structure is assessed numerically using two different time histories. Finally, effects of incident load frequency and frequency ratio on the dynamic damping of geotechnical materials are discussed. Result of analyses show that specific energy of seismic loading with identical PGA is related to the seismic load frequency. Furthermore, incident load frequency and natural frequency of a system have influence on the wave attenuation and dynamic damping of the system.

关键词： ground motion parameter load frequency PGA dynamic analysis wave attenuation

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