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    Enhancing the structural performance of masonry arch bridges with ballast mats

    , Article Journal of Performance of Constructed Facilities ; Volume 31, Issue 5 , 2017 ; 08873828 (ISSN) Mohammadzadeh, S ; Miri, A ; Nouri, M ; Sharif University of Technology
    A large portion of the railway bridge stock in many countries is comprised of masonry arch bridges. During recent years, more attention has been paid to the maintenance of such structures. Rehabilitation and retrofitting methods have been proposed to enhance the performance of masonry arch bridges and extend their service life. Because a large portion of forces exerted on such structures comes from the railway track and passing trains, structural elements are added to the track to reduce the forces transmitted to bridges. One such element is the ballast mat, which, according to suppliers, has a positive impact on the structural performance of the track. This paper tries to assess the effects... 

    Derating of transformers under non-linear load current and non-sinusoidal voltage - An overview

    , Article IET Electric Power Applications ; Volume 9, Issue 7 , August , 2015 , Pages 486-495 ; 17518660 (ISSN) Faiz, J ; Ghazizadeh, M ; Oraee, H ; Sharif University of Technology
    Institution of Engineering and Technology  2015
    The increasing application of non-linear loads in power system causes additional losses in transformers resulting in premature damage. Manufactures and users of transformers realise the importance of this phenomenon and it is vital to adopt a procedure to prevent it thereby enhancing the reliability of power system. To achieve this, the most common method is derating of transformers. This paper intends to review derating of transformers under nonsinusoidal operation, for which all available approaches are classified into four major methods including IEEE recommended, analytical, experimental and finite elements based method. For each method, the fundamental theory, significant factors... 

    Performance evaluation of energy meters in nonses'usoidal environment based on IEEE 1459 standard

    , Article 22nd International Conference and Exhibition on Electricity Distribution, CIRED 2013; Stockholm; Sweden; 10 June 2013 through 13 June 2013 ; Volume: 2013, Issue: 615 , 2013 ; 9781849197328 (ISBN) Youhannaei, M ; Honarmand, M. E ; Ouni, S ; Mehri, R ; Behinh, Y ; Mokhtari, H ; Talebi, J ; Sharif University of Technology
    The objective of this work is to study the effects of harmonics on energy meters. This study is canied out based on IEEE 1459 standard through extensive tests on some energy meters installed at Gil an utility consumers. First, a review on IEEE 1459 standard on power definitions will be given. The definitions are then ervaluated for a compact Fluorescent Lamp (CFL) as a harmonic generating load. Then, the results of the performance e-alnation of two energy meters are presented for different linear and nonlinear loads based on IEEE1459 standard power definitions. Two different test procedures are performed for this putpose. In the first series of tests, a harmonic polluted voltage is applied... 

    Numerical modeling of piles in sandy soils considering stress dependent modulus of elasticity

    , Article Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014, 22 September 2014 through 25 September 2014, Kyoto ; 2015 , Pages 973-977 ; 9781138001480 (ISBN) Ahmadi, M. M ; Abadi, S. M ; Sharif University of Technology
    Taylor and Francis - Balkema  2015
    Pile Foundations are used to transfer loads from superstructures to the underlying competent soil layers. Predicting pile bearing capacity is among the most interesting subjects for geotechnical engineers. In this study, a single pile is modeled in axisymmetric condition. The soil is considered to be a sandy soil. Then, results of the model were verified with a full scale pile load test performed by previous researchers. In order to take into consideration the real behavior of sandy soils, a variation of modulus of elasticity with respect to the changes in the mean effective stress was taken into account. The dependency of soil modulus to the mean effective stress makes the model more... 

    Investigating the effect of ambient temperature on fault-induced delayed voltage recovery events

    , Article IET Generation, Transmission and Distribution ; Volume 14, Issue 9 , 2020 , Pages 1781-1790 Saber, H ; Karimi, M. R ; Hajipour, E ; Farzin, N ; Hashemi, S. M ; Agheli, A ; Ayoubzadeh, H ; Ehsan, M ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    The high penetration of residential air conditioners (RACs) poses a growing concern in emerging fault-induceddelayed voltage recovery (FIDVR) in power systems. FIDVR is expected to be a significant threat to the stability and reliability offuture power grids. Hence, the system planners should carry out appropriate simulation studies to mitigate the severeconsequences of FIDVR events. A key question to implement these studies is how to determine the worst condition whichresults in FIDVR. Most of the actual FIDVR events have been experienced in the hot hours of the day and this issue makes onecurious to think about the relationship between the FIDVR events and the ambient temperature. In this... 

    An investigation of the effects of socket joint flexibility in space structures

    , Article Journal of Constructional Steel Research ; Volume 102 , November , 2014 , Pages 72-81 ; ISSN: 0143974X Ahmadizadeh, M ; Maalek S ; Sharif University of Technology
    Connection of truss elements using socket joints is one of the more common practices in the construction of space structures. Although these hollow spherical joints may deform due to the applied loads, these deformations and the resulting effects on the member axial forces are usually ignored in the analysis and design. This work is an investigation of the effects of socket joint deformability on the behavior of space grid structures. Here, the load-deformation relationships obtained from a series of biaxial loading tests on actual socket joints have been used to represent their behavior in several finite-element analysis models. These models have been analyzed using a special-purpose... 

    Analytical solution for large amplitude vibrations of microbeams actuated by an electro-static force

    , Article Scientia Iranica ; Volume 20, Issue 5 , 2013 , Pages 1499-1507 ; 10263098 (ISSN) Baghani, M ; Asgarshamsi, A ; Goharkhah, M ; Sharif University of Technology
    Sharif University of Technology  2013
    An analytical study using Variational Iteration Method (VIM) is carried out in order to investigate the vibrations of electro-statically actuated double-clamped and simply-supported microbeams. Effects of applied voltage and residual axial load on the nonlinear natural frequency and deflection of the microbeams are studied. It shows that pre-compression in microbeams increases the amplitude of deflections for a specific applied voltage. Also, an increase in pre-tension motivates the microbeam to show more nonlinear behavior in an applied voltage. Predicted results are compared with the experimental data available in the literature and also with numerical results which shows a good agreement.... 

    Rock joint modeling using a visco-plastic multilaminate model at constant normal load condition

    , Article Geotechnical and Geological Engineering ; Volume 24, Issue 5 , 2006 , Pages 1449-1468 ; 09603182 (ISSN) Mahin Roosta, R ; Sadaghiani, M. H ; Pak, A ; Saleh, Y ; Sharif University of Technology
    Rock joints play an important role in the behavior of rock masses under normal and shear loading conditions. Numerical simulation of the behavior of jointed rock masses is not an easy task due to complexities involved in the problem such as joint roughness, joint shear strength, hardening and softening phenomenon and mesh dependency. In this study for modeling purposes, a visco-plastic multilaminate model considering hardening and softening effects has been employed. For providing the necessary data for numerical simulation, a series of laboratory experiments have been carried out on regular tooth-shape asperities made by gypsum, under constant normal load conditions. Shear stress-shear... 

    Experimental investigation of square RC column strengthened with near surface mounted GFRP bars subjected to axial and cyclic lateral loads

    , Article Scientia Iranica ; Volume 20, Issue 5 , 2013 , Pages 1361-1371 ; 10263098 (ISSN) Dayhim, N ; Nicknam, A ; Barkhordari, M. A ; Hosseini, A ; Mehdizad, S ; Sharif University of Technology
    Sharif University of Technology  2013
    This article is intended to highlight the effectiveness of longitudinal Glass Fiber Reinforced Polymer (GFRP) bars in combination with GFRP sheets on the flexural capacity of Reinforced Concrete (RC) columns. Seven half-scale RC columns including five strengthened and two control unstrengthened specimens were experimentally tested under axial and cyclic lateral loads. The strengthened columns with two different longitudinal GFRP bar ratios were tested under three different axial load levels. The flexural strength and ductility parameters of the specimens were calculated by obtaining their deformations and measuring the loads from load cells. The experimental results indicate significant... 

    Trunk coordination in healthy and chronic nonspecific low back pain subjects during repetitive flexion-extension tasks: Effects of movement asymmetry, velocity and load

    , Article Human Movement Science ; Volume 45 , 2016 , Pages 182-192 ; 01679457 (ISSN) Mokhtarinia, H. R ; Sanjari, M. A ; Chehrehrazi, M ; Kahrizi, S ; Parnianpour, M ; Sharif University of Technology
    Multiple joint interactions are critical to produce stable coordinated movements and can be influenced by low back pain and task conditions. Inter-segmental coordination pattern and variability were assessed in subjects with and without chronic nonspecific low back pain (CNSLBP). Kinematic data were collected from 22 CNSLBP and 22 healthy volunteers during repeated trunk flexion-extension in various conditions of symmetry, velocity, and loading; each at two levels. Sagittal plane angular data were time normalized and used to calculate continuous relative phase for each data point. Mean absolute relative phase (MARP) and deviation phase (DP) were derived to quantify lumbar-pelvis and... 

    Influence of load history on the force-displacement response of in-plane loaded unreinforced masonry walls

    , Article Engineering Structures ; Volume 152 , 2017 , Pages 671-682 ; 01410296 (ISSN) Valentin Wilding, B ; Dolatshahi, K. M ; Beyer, K ; Sharif University of Technology
    Empirical drift capacity models for in-plane loaded unreinforced masonry (URM) walls are derived from results of quasi-static cyclic shear-compression tests. The experimentally determined drift capacities are, however, dependent on the applied demand, i.e., on the loading protocol that is used in the test. These loading protocols differ between test campaigns. The loading protocols applied in tests are also different from the displacement histories to which URM walls are subjected in real earthquakes. In the absence of experimental studies on the effect of loading histories on the wall response, this article presents numerical simulations of modern unreinforced clay block masonry walls that... 

    Mechanical behaviour of A-III steel rebars under monotonic loadings at seismic strain rates

    , Article Magazine of Concrete Research ; Volume 70, Issue 1 , 2018 , Pages 42-54 ; 00249831 (ISSN) Khonsari, S. V ; Shabani, A ; England, G. L ; Shahsavar Gargari, M ; Sharif University of Technology
    ICE Publishing  2018
    As the reinforcing bars used in concrete structures located in earthquake-prone areas experience strain rates higher than normal quasi-static ones, it is necessary to have a comprehensive understanding of the behaviour of such materials under these rates of loading. In this work, in order to study the behaviour of grade A-III reinforcing-bar steel (based on the GOST standard, a set of technical standards maintained by the Euro-Asian Council for Standardization, Metrology and Certification), a number of monotonic tests on its tensile and compressive strength on (short and long) specimens at various strain rates, 0·002, 0·01, 0·02 and 0·04 s-1, experienced during earthquakes, were carried out.... 

    Effects of motion segment simulation and joint positioning on spinal loads in trunk musculoskeletal models

    , Article Journal of Biomechanics ; Volume 70 , March , 2018 , Pages 149-156 ; 00219290 (ISSN) Ghezelbash, F ; Eskandari, A. H ; Shirazi Adl, A ; Arjmand, N ; El-Ouaaid, Z ; Plamondon, A ; Sharif University of Technology
    Elsevier Ltd  2018
    Musculoskeletal models represent spinal motion segments by spherical joints/beams with linear/nonlinear properties placed at various locations. We investigated the fidelity of these simplified models (i.e., spherical joints with/without rotational springs and beams considering nonlinear/linear properties) in predicting kinematics of the ligamentous spine in comparison with a detailed finite element (FE) model while considering various anterior-posterior joint placements. Using the simplified models with different joint offsets in a subject-specific musculoskeletal model, we computed local spinal forces during forward flexion and compared results with intradiscal pressure measurements. In... 

    Experimental investigation of life-time performance of unbounded natural rubber bearings as an isolation system in bridges

    , Article Structure and Infrastructure Engineering ; July , 2020 , Pages 1-14 Maghsoudi Barmi, A ; Khaloo, A ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    An experimental research study was carried out to investigate the life-time performance of unbounded Steel Reinforced Elastomeric Bearings (SREB), which are designed and used for service limit state in bridges, subjected to seismic demands. Such behaviour was investigated using 13 full-scale specimens in three phases; (1) effects of long-term service, namely the long term presence of vertical loading at service limit state, on the mechanical properties of the bearings, (2) effects of consecutive shear loading at different amplitude in presence of permanent loading, and (3) post-earthquake behaviour of the bearing against service load conditions. An innovative test setup was utilized in which... 

    Seismic performance and fragility analysis of power distribution concrete poles

    , Article Soil Dynamics and Earthquake Engineering ; Volume 150 , 2021 ; 02677261 (ISSN) Ghahremani Baghmisheh, A ; Mahsuli, M ; Sharif University of Technology
    Elsevier Ltd  2021
    This paper proposes probabilistic damage and collapse models for reinforced concrete poles in electric power distribution networks and investigates the damage and collapse pattern of poles under earthquake excitations. To this end, detailed finite element models of the H-type reinforced concrete poles are developed and verified using past experimental studies as well as the observed damage in previous earthquakes. The models are then subjected to nonlinear static analyses to study the effect of the loading pattern, loading direction, concrete strength, and failure criteria on the capacity and the collapse pattern of the pole. Next, incremental dynamic analysis is carried out to investigate... 

    Dynamic responses of intervertebral disc during static creep and dynamic cyclic loading: A parametric Poroelastic finite element analysis

    , Article Biomedical Engineering - Applications, Basis and Communications ; Volume 25, Issue 1 , 2013 ; 10162372 (ISSN) Nikkhoo, M ; Haghpanahi, M ; Parnianpour, M ; Wang, J. L ; Sharif University of Technology
    Low back pain is a common reason for activity limitation in people younger than 45 years old, and was proved to be associated with heavy physical works, repetitive lifting, impact, stationary work postures and vibrations. The study of load transferring and the loading condition encountered in spinal column can be simulated by finite element models. The intervertebral disc is a structure composed of a porous material. Many physical models were developed to simulate this phenomenon. The confounding effects of poroelastic properties and loading conditions on disc mechanical responses are, nevertheless, not cleared yet. The objective of this study was to develop an axisymmetric poroelastic... 

    Modeling and validation of a detailed FE viscoelastic lumbar spine model for vehicle occupant dummies

    , Article Computers in Biology and Medicine ; Volume 99 , 2018 , Pages 191-200 ; 00104825 (ISSN) Amiri, S ; Naserkhaki, S ; Parnianpour, M ; Sharif University of Technology
    Elsevier Ltd  2018
    The dummies currently used for predicting vehicle occupant response during frontal crashes or whole-body vibration provide insufficient information about spinal loads. Although they aptly approximate upper-body rotations in different loading scenarios, they overlook spinal loads, which are crucial to injury assessment. This paper aims to develop a modified dummy finite element (FE) model with a detailed viscoelastic lumbar spine. This model has been developed and validated against in-vitro and in-silico data under different loading conditions, and its predicted ranges of motion (RoM) and intradiscal pressure (IDP) maintain close correspondence with the in-vitro data. The dominant frequency... 

    Effect of reduced frequency on the aerodynamic behavior of an airfoil oscillating in a plunging motion

    , Article Scientia Iranica ; Volume 16, Issue 1 , 2009 , Pages 40-52 ; 10263098 (ISSN) Soltani, M. R ; Rasi Marzabadi, F ; Sharif University of Technology
    A series of low speed wind tunnel tests were conducted to study the unsteady aerodynamic behavior of an airfoil sinusoidally oscillating in plunge. The experiments included measuring the surface pressure distribution over a range of reduced frequencies, k = 0.03 - 0.06. In addition, steady state data were acquired and were used to furnish a baseline for further analysis and comparison. The model was oscillated with amplitude of ±15 cm and at three different mean angles of attack of 0, 10° and 18°. The unsteady aerodynamic loads were calculated from the surface pressure measurements, 64 ports, along the chord for both upper and lower surfaces. The plunging displacements were transformed into... 

    Transient analysis of trunk response in sudden release loading using kinematics-driven finite element model

    , Article Clinical Biomechanics ; Volume 24, Issue 4 , 2009 , Pages 341-347 ; 02680033 (ISSN) Bazrgari, B ; Shirazi Adl, A ; Parnianpour, M ; Sharif University of Technology
    Background: Sudden trunk perturbations occur in various occupational and sport activities. Despite numerous measurement studies, no comprehensive modeling simulations have yet been attempted to investigate trunk biodynamics under sudden loading/unloading. Methods: Dynamic kinematics-driven approach was used to evaluate the temporal variation of trunk muscle forces, internal loads and stability before and after a sudden release of a posterior horizontal load. Measured post-disturbance trunk kinematics, as input, and muscle electromyography (EMG) activities, for qualitative validation, were considered. Findings: Computed agonist and antagonist muscle forces before and after release agreed well... 

    Dynamic performance of concrete slabs reinforced with steel and GFRP bars under impact loading

    , Article Engineering Structures ; Volume 191 , 2019 , Pages 62-81 ; 01410296 (ISSN) Sadraie, H ; Khaloo, A ; Soltani, H ; Sharif University of Technology
    Elsevier Ltd  2019
    Reinforced concrete slabs are common structural elements that could be exposed to impact loading. Although use of reinforced concrete slabs and utilization of Fiber Reinforced Polymer (FRP) as alternative to traditional steel reinforcement slabs are growing, but the influence of various parameters on their response under impact loads is not properly evaluated. This study investigated the effect of rebar's material, amount and arrangement of reinforcements, concrete strength and slab thickness on dynamic behavior of reinforced concrete slabs using both laboratory experiments and numerical simulations. Performance of fifteen 1000 × 1000 mm concrete slabs, including two 75 mm thick plain slabs,...