Challenge Journal of Structural Mechanics
http://www.challengejournal.com/index.php/cjsmec
<a href="http://cjsmec.challengejournal.com"><img src="/public/journals/1/images/CJSMEC_small.png" alt="" width="200" height="181" align="left" hspace="10" /></a><p><em style="font-style: normal;"><a href="http://cjsmec.challengejournal.com"> <strong>cjsmec.challengejournal.com</strong></a></em></p><p><em>Challenge Journal of Structural Mechanics</em> is an international, quarterly published and open access scholarly journal that publishes original research articles as well as review articles, case studies, short communications, discussions, book reviews, letters to the editor and a diary on international events related to any aspect of structural engineering.</p><p>Primary aim of <em>CJSMEC</em> is to encourage academic challenges in structural mechanics and materials disciplines to seek for the global truth. Therefore, the Journal intends to publish at least a review or discussion as a challenge to previously published papers at each issue. A double blind peer-review policy is followed in order to increase the scientific quality of the published papers.</p>TULPAR Academic Publishingen-USChallenge Journal of Structural Mechanics2149-8024Effect of time step size on stress relaxation
http://www.challengejournal.com/index.php/cjsmec/article/view/82
<div><div><p class="CJ-Abstracttext">Many materials used in industry show time and temperature dependant stress strain relationship. While essentially most of the materials exhibit stress relaxation or in general viscoelastic material properties, some of them are assumed as linear elastic to be able to make their stress calculations simpler. On the contrary, there are some materials showing intense viscoelastic stress strain relationship even at lower temperatures and short time periods. Most of these materials are employed in construction industry as pavements on roads or bridges and needed a better understanding of their viscoelastic material properties and calculation methods for their design. For a better understanding and comparison between several material products in industry, their stress strain behavior shall be evaluated. Stress relaxation of materials, which shows time and temperature dependant properties, is investigated in this paper. For that reason first, relaxation test results existed in the literature are used to verify the numerical stress relaxation calculation of commercial FEM program, ANSYS. Second, the determination of Prony series parameters and the commands to be entered in ANSYS to perform stress relaxation are given. Finally, the amount of error in the numerical calculation depending on time step sizes at different temperatures is presented.</p></div></div>Abdullah Fettahoğlu
Copyright (c) 2017 TULPAR Academic Publishing
2017-03-102017-03-1031586210.20528/cjsmec.2016.11.029Non-linear behaviour modelling of the reinforced concrete structures by multi-layer beam elements
http://www.challengejournal.com/index.php/cjsmec/article/view/87
<div><p class="CJ-Abstracttext">A two-dimensional multi-layered finite elements modeling of reinforced concrete structures at non-linear behaviour under monotonic and cyclical loading is presented. The non-linearity material is characterized by several phenomena such as: the physical non-linearity of the concrete and steels materials, the behaviour of cracked concrete and the interaction effect between materials represented by the post-cracking field. These parameters are taken into consideration in this paper to examine the response of the reinforced concrete structures at the non-linear behaviour. Two examples of application are presented. The numerical results obtained, are in a very good agreement with available experimental data and other numerical models of the literature.</p></div>Mourad KhebiziHamza GuenfoudMohamed Guenfoud
Copyright (c) 2017 TULPAR Academic Publishing
2017-03-102017-03-1031525710.20528/cjsmec.2016.11.034Universal size effect of concrete specimens and effect of notch depth
http://www.challengejournal.com/index.php/cjsmec/article/view/215
<div><p class="CJ-Abstracttext">The universal size effect law of concrete is a law that describes the dependence of nominal strength of specimens or structure on both its size and the crack (or notch) length, over the entire of interest, and exhibits the correct small and large size asymptotic properties as required. The main difficulty has been the transition of crack length from 0, in which case the size effect mode is Type 1, to deep cracks (or notches), in which case the size effect mode is Type 2 and fundamentally different from Type 1. The current study is based on recently obtained comprehensive fracture test data from three-point bending beams tested under identical conditions. In this test, the experimental program consisted of 80 three-point bend beams with 4 different depths 40, 93, 215 and 500mm, corresponding to a size range of 1:12.5. Five different relative notch lengths, <em>a</em>/<em>D</em> = 0, 0.02, 0.075, 0.15, 0.30 were cut into the beams. A total of 20 different geometries (family of beams) were tested. The present paper will use these data to analyze the effects of size, crack length. This paper presents a studying to improve the existing universal size effect law, named by Bazant, using the experimentally obtained beam strengths for various different specimen sizes and all notch depths. The updated universal size effect law is shown to fit the comprehensive data quite well.</p></div>Sıddık ŞenerKadir Can Şener
Copyright (c) 2017 TULPAR Academic Publishing
2017-03-102017-03-1031475110.20528/cjsmec.2017.02.003HVAC systems: measurements of airflows in small duct length
http://www.challengejournal.com/index.php/cjsmec/article/view/80
<div><p class="CJ-Abstracttext">One of the most feasible ways to measure duct airflows is by tracer gas techniques, especially for complex situations when the duct lengths are short as well as their access, which makes extremely difficult or impossible other methods to be implemented. One problem associated with the implementation of tracer gas technique when the ducts lengths are short is due to the impossibility of achieving complete mixing of the tracer with airflow and its sampling. In this work, the development of a new device for the injection of tracer gas in ducts is discussed as well as a new tracer-sampling device. The developed injection device has a compact tubular shape, with magnetic fixation to be easy to apply in duct walls. An array of sonic micro jets in counter current direction, with the possibility of angular movement according to its main axle ensures a complete mixing of the tracer in very short distances. The tracer-sampling device, with a very effective integration function, feeds the sampling system for analysis. Both devices were tested in a wind tunnel of approximately 21m total length. The tests distances between injection and integration device considered were:<em> X</em>/<em>Dh</em>=22; <em>X</em>/<em>Dh</em>=4; <em>X</em>/<em>Dh</em>=2; and <em>X</em>/<em>Dh</em>=1. For very short distances of <em>X</em>/<em>Dh</em>=2 and <em>X</em>/<em>Dh</em>=1, semi empirical expressions were needed. A good reproducibility of airflow rate values was obtained. These preliminary tests showed that the practical implementation of tracer gas techniques in HVAC systems for measuring airflow rates with a very short mixing distance is possible with the devices developed.</p></div>Clito Félix Alves Afonso
Copyright (c) 2017 TULPAR Academic Publishing
2017-03-102017-03-1031384610.20528/cjsmec.2016.11.027Influence of blast-induced ground motion on dynamic response of masonry minaret of Yörgüç Paşa Mosque
http://www.challengejournal.com/index.php/cjsmec/article/view/89
<div><p class="CJ-Abstracttext">This paper focuses on the dynamic response analysis of masonry minaret of Yörgüç Paşa Mosque subjected to artificially generated surface blast-induced ground motion by using a three-dimensional finite element model. The mosque is located in the town of Kavak of Samsun, in Turkey. This study intended to determine the ground motion acceleration values due to blast-induced ground motions (air-induced and direct-induced) calculated by a random method. In order to model blast-induced ground motion, firstly, peak acceleration and the time envelope curve function of ground motion acceleration were obtained from the distance of the explosion center and the explosion charge weight and then blast-induced acceleration time history were established by using these factors. Non-stationary random process is presented as an appropriate method to be produced by the blast-induced ground motion model. As a representative of blast-induced ground motion, the software named BlastGM (Artificial Generation of Blast-induced Ground Motion) was developed by authors to predict ground motion acceleration values. Artificial acceleration values generated from the software depend on the charge weight and distance from the center of the explosion. According to the examination of synthetically generated acceleration values, it can be concluded that the explosions cause significant effective ground movements. In the paper, three-dimensional finite element model of the minaret was designed by ANSYS. Moreover, the maximum stresses and displacements of the minaret were investigated. The results of this study indicate that the masonry minaret has been affected substantially by effects of blast-induced ground motion.</p></div>Olgun KöksalKemal HacıefendioğluEmre AlpaslanFahri Birinci
Copyright (c) 2017 TULPAR Academic Publishing
2017-03-102017-03-1031313710.20528/cjsmec.2016.12.036Metaheuristic approaches for optimum design of cantilever reinforced concrete retaining walls
http://www.challengejournal.com/index.php/cjsmec/article/view/84
<div><div><p class="CJ-Abstracttext">An approach is presented for optimum design of cantilever reinforced concrete (RC) retaining wall via teaching-learning based optimization (TLBO) algorithm. The objective function of the optimization is to minimize total material cost including concrete and reinforcing steel bars of the cantilever retaining wall by considering overturning, sliding and bearing stabilities, bending moment and shear capacities and requirements for design and construction of reinforced concrete structures (TS 500/2000). TLBO algorithm is a simple algorithm without any special algorithm parameters. This innovative approach is providing an advantage to TLBO in terms of easily applying to the problem. The proposed method has been performed on numerical examples and the results are compared with previous approaches. Results show that, the methodology is feasible for obtaining the optimum design of RC cantilever retaining walls.</p></div></div>Gebrail BekdaşRasim Temür
Copyright (c) 2017 TULPAR Academic Publishing
2017-03-102017-03-1031233010.20528/cjsmec.2016.11.031Research on relation between natural frequency and axial stress of round bar with intermediate-supported ends
http://www.challengejournal.com/index.php/cjsmec/article/view/133
<div><p class="CJ-Abstracttext">In order to make a method be useful to measure an axial stress of a member by a natural frequency, we investigated a relation between a natural frequency and an axial stress of a round bar with intermediate-supported ends, the boundary condition of which was one between a fix-supported end and a simply-supported end. To define an intermediate-supported end condition, we adopted a parameter, a ratio of a moment of a force to a deflection angle at the end. It was shown theoretically that the parameter of an intermediate-supported end could be evaluated by one at a support on a continuous beam consisted of 3 spans. The 3-spanned beam has same vibration characteristics of a beam with intermediate-supported ends. We manufactured a test device of a 3-spanned beam by which we could simulate a vibration under various intermediate-supported end conditions. The theoretical relation and experimental results between a natural frequency and an axial stress agreed for the most part.</p></div>Tsutomu YoshidaTakeshi WatanabeKunihiko Sakurada
Copyright (c) 2017 TULPAR Academic Publishing
2017-03-102017-03-1031172210.20528/cjsmec.2017.02.002Analytical solution for bending and buckling response of laminated non-homogeneous plates using a simplified-higher order theory
http://www.challengejournal.com/index.php/cjsmec/article/view/224
In this study, analytical solutions for the bending and buckling analysis of simply supported laminated non-homogeneous composite plates based on first and simplified-higher order theory are presented. The simplified-higher order theory assumes that the in-plane rotation tensor is constant through the thickness. The constitutive equations of these theories were obtained by using principle of virtual work. Numerical results for the bending response and critical buckling loads of cross-ply laminates are presented. The effect of non-homogeneity, lamination schemes, aspect ratio, side-to-thickness ratio and in-plane orthotropy ratio on the bending and buckling response were analysed. The obtained results are compared with available elasticity and higher order solutions in the literature. The comparison studies show that simplified-higher order theory can achieve the same accuracy of the existing higher order theory for non-homogeneous thin plate.Ferruh TuranMuhammed Fatih BaşoğluZihni Zerin
Copyright (c) 2017 TULPAR Academic Publishing
2017-03-102017-03-103111610.20528/cjsmec.2017.02.001Cover & Contents Vol.3 No.1
http://www.challengejournal.com/index.php/cjsmec/article/view/245
Journal Management CJSMEC
Copyright (c) 2017 TULPAR Academic Publishing
2017-03-102017-03-1031Thermoelastic stress analysis for detecting wrinkles and associated resin pockets in polymer composites
http://www.challengejournal.com/index.php/cjsmec/article/view/78
<div><p class="CJ-Abstracttext">A thermos elastic stress analysis method is proposed consisting of an array of infrared measurement sensors used for evaluation the wrinkling defects and associated resin pockets in a fiber reinforced polymer (FRP) composite structure. Wrinkling or fiber waviness defects results when out of plane distortions occur in some or all of the composite layers of the laminate. The wrinkles result in significant reductions of mechanical properties in the composite structure. The method involves instrumentation and device for application of internal energy in the material such as transient or cyclic mechanical excitations. These external excitations are induced in a prescribed or measurable cyclic or transient function of time. Infrared measurements from the surface of the composite are synchronized with the applied excitation energy. The results are used to provide for a map detailing the inner wrinkle defects and associated resin pockets in the laminated composite structure.</p></div>Rani ElhajjarRami Haj-Ali
Copyright (c) 2016 TULPAR Academic Publishing
2016-12-262016-12-263124624710.20528/cjsmec.2016.11.025Soft-story effects on the behaviour of seismically isolated buildings under near and far-fault earthquakes
http://www.challengejournal.com/index.php/cjsmec/article/view/212
<div><p class="CJ-Abstracttext">In this study, the effects of soft-story on the seismic behaviour of 3-story and 8-story isolated buildings under near and far-fault earthquakes were investigated. Four different structural models with two different 1<sup>st</sup> story height were designed: One with 1<sup>st</sup> story height of 3m and 2<sup>nd</sup> with 1<sup>st</sup> story height of 4.5m to capture soft story effect. The prototype fixed base buildings were converted to seismically isolated buildings by introducing rubber isolators at base level. Analyses were conducted by using two different isolation systems (QW7.5Tb3 and QW7.5Tb4). The modelling of conventional fixed base prototype seismically isolated buildings and their modal analyses were conducted on finite-element program SAP2000, whereas, modelling of seismically isolated buildings and nonlinear time-history analyses were conducted using 3D-BASIS program. The four accelerations records has been used for the time-history analysis. Floor accelerations, story shears and inter-story drift ratios were the key structural responses considered. The analysis results showed seismic isolations can be used as a viable mitigation method for the buildings with soft-stories under near and far-fault earthquakes. Based on the results obtained, it is interesting to note that all types of buildings whether with soft story or with typical story height show the same acceleration trend and close values (except top floor) for all types of isolation systems and earthquakes considered. In addition, both 3 and 8-story buildings suffered increase in interstory drifts beyond the limits defined UBC 97 under earthquakes containing long period pulses.</p></div>Savaş ErdemKhalid Saifullah
Copyright (c) 2016 TULPAR Academic Publishing
2016-12-262016-12-263123424510.20528/cjsmec.2016.12.038Nonlinear finite element analysis of cold-formed steel plain angle columns
http://www.challengejournal.com/index.php/cjsmec/article/view/86
<div><p class="CJ-Abstracttext">The main objective of this paper is to provide an efficient and accurate finite element model to understand the behavior of cold-formed steel plain angle columns. The effects of initial local and overall geometric imperfections have been taken into consideration in the analysis. The material nonlinearities of flat and corner portions of the angle sections were incorporated in the model. Failure loads and buckling modes as well as load-shortening curves of plain angle columns were investigated in this study. The nonlinear finite element model was verified against experimental results. The finite element analysis was performed on plain angles compressed between fixed ends over different column lengths, and column curves were obtained.</p></div>Mustafa DurmazAyşe Daloğlu
Copyright (c) 2016 TULPAR Academic Publishing
2016-12-262016-12-263122022510.20528/cjsmec.2016.11.033Wind loads for stadium lighting towers according to Eurocode 1
http://www.challengejournal.com/index.php/cjsmec/article/view/88
<div><p class="CJ-Abstracttext">The determination of actions on structures is an important step of in the design process. In nature, so many outer and inner actions are acting on structures continuously. The two most important ones of those actions are the earthquake and wind actions. For some structures, i.e. towers, high chimneys or lighting towers, the priority of these two severe actions can change. Wind forces can become a governing force on the design of these structures. Therefore, the determination of wind forces for these tall, slender and wind-sensitive structures becomes very important. Also, these tall and slender structures have a high ratio of height to least diameter that makes them more slender and wind-sensitive than any other structures. In this study, the determination of wind loads for a selected and modeled stadium lighting tower was given according to Eurocode 1 which is an international well-known standard. This study showed that it is difficult to calculate wind loads of stadium lighting towers according to Eurocode 1 because of the complexity of the document, insufficient explanation of some formulas like resonant response factor and unclear graph sections for the reader. This study is believed to enlighten the way of the users of Eurocode 1.</p></div>Zeki KaracaHasan Tahsin ÖztürkErdem Türkeli
Copyright (c) 2016 TULPAR Academic Publishing
2016-12-262016-12-263122623310.20528/cjsmec.2016.12.035Bonded particles models of rock plates with circular cavities in uniaxial and biaxial compression
http://www.challengejournal.com/index.php/cjsmec/article/view/79
<div><p class="CJ-Abstracttext">In this paper, a distinct elements code is used to perform a numerical investigation for the size and stress gradient effects on the fracture initiation and propagation around single or pairs of pre-existing cavities in brittle rock. To investigate the rock fracture around cavities and to assess the potential of the numerical model to simulate this behavior, published laboratory physical model on granite is simulated numerically with a Bonded Particles Model (BPM). The numerical model is presented and the calibration of the BPM micro-parameters is described. Then, the calibrated BPMs are used to investigate the effect of the size of the cavity on the primary, secondary and side wall fracturing, as well as on the fracturing modes. Moreover, BPMs with two circular cavities were used to study the interaction of these holes of the same diameter and to investigate the importance of their relative distance. Finally, the simulated material was studied by biaxial tests on BPMs with a pre-existing hole.</p></div>Michail A. LotidisPavlos P. NomikosAlexandros I. Sofianos
Copyright (c) 2016 TULPAR Academic Publishing
2016-12-262016-12-263120521110.20528/cjsmec.2016.11.026High strain rate and quasi-static compression behavior and energy absorption characteristic of PVC foam
http://www.challengejournal.com/index.php/cjsmec/article/view/81
<div><p class="CJ-Abstracttext">The mechanical properties at room temperature of two densities PVC foams have been experimentally evaluated in both quasi-static and dynamic compression loading conditions. The strain rate effect have been evaluated by comparing the constant strength during plateau region. Energy absorption efficiency of PVC foam is investigated, and it shows that in certain density range, the efficiency of lighter PVC foam is larger than that of heavier PVC foam, but the efficiency stress of lighter PVC foam is smaller than that of heavier PVC foam. While the lighter PVC foam has been compressed more than heavier PVC foam when they reach their peak efficiency. Therefore, for a certain density of PVC foam itself, when the loading rates increase, the PVC foam will absorb more energy more efficiently.</p></div>Zhang WeiYe Nan
Copyright (c) 2016 TULPAR Academic Publishing
2016-12-262016-12-263121221510.20528/cjsmec.2016.11.028Optimum design of reinforced concrete columns employing teaching-learning based optimization
http://www.challengejournal.com/index.php/cjsmec/article/view/83
<div><p class="CJ-Abstracttext">In structural engineering, the design of reinforced concrete (RC) structures needs an initial de-sign for cross sectional dimensions. After these dimensions are defined, the design constraints and the required reinforcement bars are calculated. But the required reinforcement area is not exactly provided since the size of rebars are fixed. At the end of the design, the security measures are provided, but the designer has no idea for the optimization of the design in mean of economy. For that reason, a powerful search methodology can be programed by using metaheuristic algorithms. In this study, optimum design of reinforced concrete columns was investigated by using an education based metaheuristic algorithm called teaching-learning based optimization (TLBO). In the methodology, the slenderness of the columns is also taken into consideration by using a simple approach given in the ACI 318 design code. In this approach, the factored design flexural moments are defined according to the buckling load and axial load of columns. The design variables of the problem include cross section dimension of the column and the detailed reinforcement design and the optimization objective is the minimization the maximum material cost of the column. Differently from the other metaheuristic algorithms, the decision of the optimization type (global or local search) is not defined by using a probability parameter in TLBO. In optimization, two phases of TLBO; teacher (global search) and learner (local search) phases are consequently applied in search of best design variables. The proposed approach is effective for the structural optimization problem.</p></div>Gebrail BekdaşSinan Melih Niğdeli
Copyright (c) 2016 TULPAR Academic Publishing
2016-12-262016-12-263121621910.20528/cjsmec.2016.11.030Assessment of aerodynamic response of the Nissibi cable-stayed bridge using three-dimensional computational fluid dynamics
http://www.challengejournal.com/index.php/cjsmec/article/view/91
<div><p class="CJ-Abstracttext">Aerodynamic behavior has the greatest impact on long-span bridges and is the most important factor in the design of cable stayed bridges, which should not be overlooked. CFD (Computational Fluid Dynamics) is the most widely used technique, among bridge engineers, to predict wind speed, direction and vortex-shedding form before conducting wind tunnel tests. In this study, a bi-directional CFD analysis with the wind flow parallel and perpendicular to Nissibi Bridge's, which has a main span of 400 m and claimed the spot of Turkey’s 3<sup>rd</sup> largest bridge, deck cross-section has been performed by approximate modelling of the bridge and the surrounding structures. The study is done by using CFD++ software/computer program. The results showed that the effect of wind acting on <em>x</em> direction of impact with 30 m/s has caused turbulence and vortex on conjugation area of the tower and it is observed that the upside down Y shape of the tower breaks down the balance of wind flow. However, bridge deck is not exposed to serious amount of vortex influence due to the wind on <em>y</em> direction. In addition, the analysis revealed that maximum pressure distribution occurred on vertical surface of the tower and it increases in direct proportion to the height of the tower.</p></div>Savaş Erdemİrem YağmuroğluKhalid Saifullah
Copyright (c) 2016 TULPAR Academic Publishing
2016-12-262016-12-263119620410.20528/cjsmec.2016.12.037Cover & Contents Vol.2 No.4
http://www.challengejournal.com/index.php/cjsmec/article/view/213
Journal Management CJSMEC
Copyright (c) 2016 TULPAR Academic Publishing
2016-12-262016-12-2631Teaching-learning based optimization for parameter estimation of double tuned mass dampers
http://www.challengejournal.com/index.php/cjsmec/article/view/85
<div><p class="CJ-Abstracttext">The classical methods for parameter estimation of tuned mass dampers are well known simple formulations, but these formulations are only suitable for multiple degree of freedom structures by considering a single mode. If special range limitation of tuned mass dampers and inherent damping of the main structure are considered, the best way to estimate the parameters is to use a numerical method. The numerical method must have a good convergence and computation time. In that case, metaheuristic methods are effective on the problem. Generally, metaheuristic method is inspired from a process of life and it is formulated for several steps in order to reach an optimal goal. Differently from the single tuned mass dampers, double tuned mass dampers can be also used for the reduction of vibrations. In civil structures, earthquake excitation is a major source of vibrations. In this study, optimum double tuned mass dampers are investigated for seismic structures by using a wide range of earthquake records for global optimum. As an optimization algorithm, teaching learning based optimization is employed. In this algorithm, the teaching and learning phases of a class are modified for optimization problems. The optimization of double tuned mass damper is more challenging than the single ones since the number of design variable is doubled and the design constraint about the stroke of the both masses must be considered. The proposed method is compared with the existing approaches and the methodology is feasible for parameter estimation of double tuned mass dampers.</p></div>Sinan Melih NiğdeliGebrail Bekdaş
Copyright (c) 2016 TULPAR Academic Publishing
2016-11-182016-11-183110.20528/cjsmec.2016.11.032Experimental verification of blade elongation and axial rotor shift in steam turbines
http://www.challengejournal.com/index.php/cjsmec/article/view/74
<div><p class="CJ-Abstracttext">The experimental research of static and dynamic characteristics of rotating parts of turbomachines is a very important part of the design and verification of the machine parameters as well as optimization of their operational regimes. The described method of measuring dynamic and static characteristics, especially blade elongation and rotor axial shift, are based on the utilization of the non-contact magnetoresistive sensors developed in the Institute of Thermomechanics AS CR. These sensors exhibit positive properties for this purpose.</p></div>Pavel Procházka
Copyright (c) 2016 TULPAR Academic Publishing
2016-09-292016-09-293119019210.20528/cjsmec.2016.09.021Girkmann problem with a Discrete Element Method
http://www.challengejournal.com/index.php/cjsmec/article/view/66
<div><p class="CJ-Abstracttext">Cells of Voronoï are used as particles in the Discrete Element code CeaMka3D. This type of meshing does not leave geometrical space like that can be the case with spherical particles. This method has already been used successfully to simulate the propagation of seismic waves in a linear elastic medium in 2D or in 3D. In this paper, a specific axisymmetric formulation is presented. In a first part, the calculation of the volumetric deformation of a particle and the forces between particles are described. In a second part, the specific forces for the axisymmetric formulation are described. At last, this formulation is tested for the Girkmann problem. This axisymmetric benchmark has been presented in January 2008 by the International Association of Computational Mechanics (IACM) in order to test the singularity at the junction between shell and beam. The accuracy of the axisymmetric formulation for this Discrete Element Method is evaluated by this benchmark. The results of this Discrete Element Method are compared with others numerical methods.</p></div>Christian Mariotti
Copyright (c) 2016 TULPAR Academic Publishing
2016-09-292016-09-293118518910.20528/cjsmec.2016.08.017Assessment of bonding defects in FRP reinforced structures via ultrasonic technique
http://www.challengejournal.com/index.php/cjsmec/article/view/68
<div><p class="CJ-Abstracttext">Fiber reinforced polymer (FRP) composite systems are widely used for the rehabilitation of concrete structures such as building that need to resist to seismic loads, bridges that have to carry heavier traffic loads. The technique consists in bonding the composite plate to the concrete surface element in order to increase the flexural capacity. A proper attachment of the FRP plate to the concrete surface is necessary for the efficiency of the load transfer between the reinforcement and the substrate. In this work, the quality of composite bonding is characterized through ultrasonic testing. The proposed technique is relative to a time domain analysis of the ultrasonic signals and couples the Akaike Information Criterion (AIC), used as automatic onset signal detection, and the Equivalent Time-Length (ETL), used as an indicator of the quantity of energy propagating through the bonding. It has been tested both numerically and experimentally, in vitro, using samples with imposed well- known defects.</p></div>Emma La Malfa RibollaMohsen Rezaee HajidehiGiuseppe Fileccia ScimemiAntonino SpadaGiuseppe Giambanco
Copyright (c) 2016 TULPAR Academic Publishing
2016-09-292016-09-293113914610.20528/cjsmec.2016.08.018Transient resonance in limited power systems
http://www.challengejournal.com/index.php/cjsmec/article/view/71
<div><p class="CJ-Abstracttext">Difficulties in obtaining – by means of known methods - the proper estimation of maximum amplitudes in the transient resonance of technical systems, were indicated in the paper. It was proved that models of 1 degree of freedom cannot be used for such systems. The energy method of estimating maximum amplitudes in the transient resonance - useful also for systems of several degrees of freedom and multiple drives - was proposed. Taking into account interactions between the rotor and body motion of vibratory machines case the nomogram method for investigating resonance amplitude for coast-down phase was also presented.</p></div>Jerzy MichalczykGrzegorz Cieplok
Copyright (c) 2016 TULPAR Academic Publishing
2016-09-292016-09-293116316810.20528/cjsmec.2016.09.020Research of the non-uniform strain and displacement fields in solids with concentrators with the use of the DIC technique
http://www.challengejournal.com/index.php/cjsmec/article/view/75
<div><p class="CJ-Abstracttext">This work focuses on analyzes the non-uniform strain fields in the area of stress concentration and study the limiting stress-strain state of the material in the test samples with different geometry concentrators with the use of the measuring system non-contact three-dimensional digital optical system Vic-3D. The research included tensile mechanical tests on flat samples with a hole research of the damage and failure processes of materials.</p></div>Elena M. Spaskova
Copyright (c) 2016 TULPAR Academic Publishing
2016-09-292016-09-293119319510.20528/cjsmec.2016.09.023The influence of different concrete classes on the seismic response of a seismically isolated building
http://www.challengejournal.com/index.php/cjsmec/article/view/73
<div><p class="CJ-Abstracttext">In this study, an eight story seismically isolated building representing a mid-rise type building was employed to investigate the effect of usage of different concrete classes (C20, C25, C30, C40, and C50) on the seismic response of a seismically isolated building. The prototype fixed base buildings were converted to seismically isolated buildings by introducing rubber isolators at base level. Analyses were conducted by using two different isolation systems (QW5Tb3 and QW10Tb3).The modelling of conventional fixed base prototype seismically isolated buildings and their modal analyses were conducted on finite-element program SAP2000, whereas, modelling of seismically isolated buildings and nonlinear time-history analyses were conducted using 3D-BASIS program. Floor accelerations, Story shears and inter-story drift ratios were the key structural responses considered. The analysis results showed concrete strength have significant effects on the seismic behaviour of the structures. Seismically isolated buildings with isolation system having 5% characteristic strength, C40 and C50 concrete buildings showed less first floor accelerations as compared to the lower concrete class buildings. In addition, isolated buildings with C40 and C50 concrete showed much more inter-story drift ratio values at each floor level as compared to isolated buildings with C20, C25 and C30 concrete which showed values very close to one another.</p></div>Savaş ErdemKhalid SaifullahEzgi GürbüzMarva Angela Blankson
Copyright (c) 2016 TULPAR Academic Publishing
2016-09-292016-09-293116917810.20528/cjsmec.2016.09.022Optimal strain gage location for determination of mode I stress intensity factor for orthotropic laminates using a single strain gage
http://www.challengejournal.com/index.php/cjsmec/article/view/76
<div><p class="CJ-Abstracttext">The present work discusses a robust method developed for determination of mode I stress intensity factor (<em>K<sub>I</sub></em>) of orthotropic laminates using a single strain gage and based on a three parameter strain series representation ahead of the crack tip. Appropriate radial location of the strain gage ahead of the crack tip is important in the sense that strain gages placed either very near or very far from the crack tip might lead to inaccuracies in the estimated SIFs due to 3D effects near the crack tip or inaccurate strain field representation at farther distances. The theoretical formulation has been presented for determination of angular location, orientation and the upper bound on the radial location (<em>r</em><sub>max</sub>) for pasting the strain gage which could be subsequently used for accurate determination of <em>K<sub>I</sub></em>. Numerical simulations have been presented considering edge cracked [90<sub>2</sub>/0]<sub>10S</sub> carbon-epoxy orthotropic laminates to illustrate the determination of <em>r</em><sub>max</sub> and <em>K<sub>I</sub></em> of such laminates.</p></div>Debabrata ChakrabortyDebaleena ChakrabortyK. S. R. Krishna Murthy
Copyright (c) 2016 TULPAR Academic Publishing
2016-09-292016-09-293117918410.20528/cjsmec.2016.09.024Cover & Contents Vol.2 No.3
http://www.challengejournal.com/index.php/cjsmec/article/view/77
Journal Management CJSMEC
Copyright (c) 2016 TULPAR Academic Publishing
2016-09-292016-09-2931Energy & crack tip stress interactions in mixed mode I/III fracture of DX51 steel sheets
http://www.challengejournal.com/index.php/cjsmec/article/view/70
<div><p class="CJ-Abstracttext">DX51D sheet is subjected to mixed mode I/III loading in a purposely designed fixture apparatus. The resulting stable crack-tip growth, direction, slant angle and typical factory-roof crack were observed and discussed as the loading mixity was varied. The total essential work of fracture or fracture toughness, for each mixity loading, was evaluated adopting energy methods during experimentation, whilst theory details how the total may be separated into its individual mode components. The fracture type and direction of crack path were based on the von Mises failure theory and the fracture criteria of maximum shear stress, maximum hoop stress and maximum normal stress along with the application of Hill’s theory. The findings described clearly establish the link between the applications of the energy based equations governing crack initiation and propagation and the equations describing the stress field surrounding the crack tip in the mixed mode I/III field.</p></div>Claire De Marco Muscat-FenechStephen Ciappara
Copyright (c) 2016 TULPAR Academic Publishing
2016-09-292016-09-293114716210.20528/cjsmec.2016.09.019Shear capacity of post-installed anchors according to ACI318 and TS500
http://www.challengejournal.com/index.php/cjsmec/article/view/56
Applications of strengthening works have accelerated gradually due to earthquakes in recent years. Different strengthening methods are being used in order to bring the structures with insufficient strength to those levels specified by current codes. In most of the applications, the bonding between the new structural elements and the concrete of the old structure is established with the chemical anchors. Although they are used widespread in the practice, there are not any sufficient details in Turkish Standards for the design and application of these anchors. In this work, a comparison of ACI318 and the Turkish Standards for anchor shear strength is given. As the result, it has been concluded that there are vital differences between ACI and the Turkish Standards and that an immediate revision is needed for the Turkish Standards.Özlem ÇalışkanSalih YılmazHasan Kaplan
Copyright (c) 2016 TULPAR Academic Publishing
2016-06-302016-06-3031697410.20528/cjsmec.2016.04.009Reliability design of the hinge kit system subjected to repetitive loading in a commercial refrigerator
http://www.challengejournal.com/index.php/cjsmec/article/view/59
A newly designed hinge kit system (HKS) of a commercial refrigerator was subjected to a robust reliability methodology during the design phase of the system. This methodology included setting the overall parametric accelerated life test (ALT) plan of product and identifying failure mechanisms and modes in field. The ALT included a sample size equation to improve several of the HKS design parameters. Reliability of the new HKS was targeted to be 10 years over B1. Failure sites in the HKS were identified through returned products from the field. The first ALT confirmed a failure that occurred at the housing of HKS. The missing design parameters of HKS housing for the refrigerator were that it had no support ribs in the original design. The supporting structure of HKS in the refrigerator was modified based on the action plan. Cracks were identified in a second ALT that was generated in the torsional shaft. Due to it having squared off corners, the HKS torsional shaft did not have not enough strength to withstand repetitive stresses. The shaft was modified as a consequence of the ALTs. The reliability of redesigned HKS is now guaranteed as B1 10 years. The design methods - load analysis and three ALTs were very effective in identifying the missing design parameters during the design phase. The robust design method presented in this paper might be applicable to the other mechanical systems.Seong-woo WooDennis L. O’Neal
Copyright (c) 2016 TULPAR Academic Publishing
2016-06-302016-06-3031758410.20528/cjsmec.2016.05.010Seismic analysis of arch dams subjected to in-phase and anti-phase ground motions
http://www.challengejournal.com/index.php/cjsmec/article/view/60
<div><p class="CJ-Abstracttext">In this study, the response of arch dams is obtained for in-phase and anti-phase ground motions when there is no water in the reservoir. The material of the dam is considered to be linearly elastic, homogenous and isotropic. The foundation and banks of the dam, which are usually of hard rock, are assumed to be rigid. The S16E component of San Fernando Earthquake, February 9, 1971, has been used in the calculations. The response of arch dams determined for anti-phase dynamic effects is compared with that of in-phase (uniform) dynamic effects.</p></div>Mehmet AkköseAli Aydın DumanoğluAlemdar Bayraktar
Copyright (c) 2016 TULPAR Academic Publishing
2016-06-302016-06-3031859210.20528/cjsmec.2016.05.011Acceleration response spectra for Tbilisi city with site effects
http://www.challengejournal.com/index.php/cjsmec/article/view/61
<div><p class="CJ-Abstracttext">The utilization of time histories of earthquake ground motion has grown considerably in the field of earthquake engineering. It is very unlikely, however, that recordings of earthquake ground motion will be available for all sites and conditions of interest. Hence, there is a need for efficient methods for the simulation of strong ground motion for a given region. Due to lack of the real strong ground motion records the objective of this research is to develop a methodology for rapid generation of horizontal and vertical components of earthquake ground motion at any site for Tbilisi city. The model developed in this study provides simulation of ground motion over a wide range of magnitudes and distances at 8 earthquake sources zones of Tbilisi region (within 50 km). The research includes three main topics: (i) the stochastic simulation of earthquake ground motion at a given site of the city of Tbilisi; (ii) the estimation of acceleration time histories at a given site using the direct method of engineering seismology considering soil conditions based on the theory of the reflected waves and (iii) calculation of horizontal and vertical acceleration elastic response spectra for main sites of Tbilisi territory. The simulation procedure typically consists of multiplying deterministic modulating function with a stationary process of known power spectral density. The obtained results in the terms of normalized elastic response spectra can be widely applied in the practice of earthquake engineering in Georgia.</p></div>Paata RekvavaKetevan Mdivani
Copyright (c) 2016 TULPAR Academic Publishing
2016-06-302016-06-30319310010.20528/cjsmec.2016.05.012Evaluation of framed building types based on the combination of fuzzy AHP and fuzzy MOORA methods
http://www.challengejournal.com/index.php/cjsmec/article/view/62
<div><p class="CJ-Abstracttext">Mankind has been using different kind of materials to build shelters and after then more specific structures throughout the history. If the stone is accepted as a primitive construction material; wood, concrete and steel has spread to the construction history. However, from both of the supply and demand view, it is possible to say that defining the best solution to the construction necessities and constraints is vastly ambiguous. In other words, making decision with respect to infinite parameters is an important task. The level of uncertainty in the optimality based definition of framed building types is relatively high and need to be carefully analyzed. Therefore, in order to select a proper construction technique, combination of fuzzy AHP (analytic hierarchy process) and evaluation based on fuzzy MOORA (multi objective optimization by ratio analysis) has proposed a new useful method, in which FAHP is used for calculating priority weight of criteria and the MOORA is implemented for obtaining the final ranking of construction techniques. In addition, for expressing the applicability of the offered model, it is supported by a case study. In the rating of framed building types; cost, performance, time, fire, corrosion, esthetics and recycling is considered as important factors. As a result, this model is easy to understand and simple to implement in various areas. Also, this method is applicable for the choosing of proper alternatives in different selection problems.</p></div>Burak ErkaymanFatih Mehmet Özkal
Copyright (c) 2016 TULPAR Academic Publishing
2016-06-302016-06-303110110810.20528/cjsmec.2016.06.013A Poisson method application to the assessment of the earthquake hazard in the North Anatolian Fault Zone, Turkey
http://www.challengejournal.com/index.php/cjsmec/article/view/63
<div><p class="CJ-Abstracttext">North Anatolian Fault (NAF) is one from the most important strike-slip fault zones in the world and located among regions in the highest seismic activity. The NAFZ observed very large earthquakes from the past to present. The aim of this study; the important parameters of Gutenberg-Richter relationship (<em>a</em> and <em>b </em>values) estimated and this parameters taking into account, earthquakes were examined in the between years 1900-2015 for 10 different seismic source regions in the NAFZ. After that estimated occurrence probabilities and return periods of occurring earthquakes in fault zone in the next years, and is being assessed with Poisson method the earthquake hazard of the NAFZ. The 10 different seismic source regions are determined the relationships between the cumulative number-magnitude which estimated <em>a</em> and <em>b</em> parameters with the equation of <em>LogN=a-bM</em> in the Gutenberg-Richter. A homogenous earthquake catalog for <em>M<sub>S</sub></em> magnitude which is equal or larger than 4.0 is used for the time period between 1900 and 2015. The database of catalog used in the study has been created from International Seismological Center (ISC) and Boğazici University Kandilli observation and earthquake research institute (KOERI). The earthquake data were obtained until from 1900 to 1974 from KOERI and ISC until from 1974 to 2015 from KOERI. The probabilities of the earthquake occurring are estimated for the next 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 years in the 10 different seismic source regions. The highest earthquake occur probabilities in 10 different seismic source regions in the next years estimated that the region Tokat-Erzincan (Region 9) 99% with an earthquake occur probability for magnitude 6.5 which the return period 24.7 year, 92% with an earthquake occur probability for magnitude 7 which the return period 39.1 year, 80% with an earthquake occur probability for magnitude 7.5 which the return period 62.1 year, 64% with an earthquake occur probability for magnitude 8 which the return period 98.5 year. For the Marmara Region (Region 2) in the next 100 year estimated that 89% with an earthquake occur probability for magnitude 6 which the return period 44.9 year, 45% with an earthquake occur probability for magnitude 6.5 which the return period 87 year, 45% with an earthquake occur probability for magnitude 7 which the return period 168.6 year.</p></div>Tuğba TürkerYusuf Bayrak
Copyright (c) 2016 TULPAR Academic Publishing
2016-06-302016-06-303110912110.20528/cjsmec.2016.06.014An experimental study on impact of anchor bars at the steel frames with infilled walls
http://www.challengejournal.com/index.php/cjsmec/article/view/64
<div><p class="CJ-Abstracttext">In this study, a series of experimental study was conducted to investigate the effect of anchor bars on steel frame systems where the connections were provided by anchor bars between frame and infilled walls. Seven one over four scaled specimens having one story and one bay of frames were tested. Experimental study was carried out by damage-controlled and incrementally applied load up to loading cracks. The test results relieved that with the help of using anchor bars the capacity of energy absorption with initial stiffness were increased. It has been found that the frames without using anchor bars failure at the loading edge, the crushing behavior of infilled walls and separations at free edges were occurred. These observed failure behaviors replies with tensile cracking for the frames having anchor bars. There for it should be underlined that anchor bars have a significant effect on improving the behavior of the frames.</p></div>Atila KumbasaroğluAhmet Budak
Copyright (c) 2016 TULPAR Academic Publishing
2016-06-302016-06-303112913810.20528/cjsmec.2016.06.016Test on dynamic performance of silt-concrete structure system under cyclic loading with different frequency
http://www.challengejournal.com/index.php/cjsmec/article/view/65
<div><div><p class="CJ-Abstracttext">In order to study the dynamic response of the soil-structure system and the contact performance between soil and structure under cyclic loading, a Suspensory Ring Test Apparatus was designed by the authors, and a series of tests had been carried out. The physical properties of the test silt were that <em>ρ</em>=1.59g/cm<sup>3</sup>, <em>ω<sub>P</sub></em>=14.26%, <em>ω<sub>L</sub></em>=21.77%. In the paper, The Suspensory Ring Test Apparatus was introduced firstly. Then, the test data were analyzed in two aspects, that was (1) the damage mechanism of the soil-structure system, (2) the factors which affected on contact performance between silt and concrete structure under cyclic loading, such as moisture content, loading frequency, roughness, and so on. Finally, some conclusions were also proposed.</p></div></div>Liyun LiXiuli DuXiaoqiong WangShengxia ZhangAijun Yao
Copyright (c) 2016 TULPAR Academic Publishing
2016-06-302016-06-303112212810.20528/cjsmec.2016.06.015Cover & Contents Vol.2 No.2
http://www.challengejournal.com/index.php/cjsmec/article/view/67
Journal Management CJSMEC
Copyright (c) 2016 TULPAR Academic Publishing
2016-06-302016-06-3031Seismic response of a ten story concrete building subjected to different earthquakes
http://www.challengejournal.com/index.php/cjsmec/article/view/53
<div><p class="CJ-Abstracttext">The purpose of this paper is to compare the response of a ten story concrete building in San Jose, California, under three different earthquakes. The strong-motion records of the instrumented building obtained during the 1984 Morgan Hill earthquake were used to calibrate a finite element model. Soil-structure interaction was included in the model by adding some translational springs to the foundation. The same model was subjected to 1986 Mount Lewis and 1989 Loma Prieta earthquakes. While for the first case a good match between the recorded data and analytical results was obtained, for the second one the match was not as good as expected. A modal identification analysis of the building was conducted for the three ground motions using both just output operational modal analysis (OMA) and input-output experimental modal analysis (EMA). It was demonstrated that for Loma Prieta, which presents higher amplitude shaking than the other two ground motions, the fundamental period for the transversal mode of the structure was higher than that obtained using the other two earthquakes. Consequently, the springs of the finite element model needed to be updated for Loma Prieta in order to capture the more flexible response of the building. After this adjustment, there was a good match between the recorded motions and analytical results. This study proves that the effects of soil-structure interaction becomes very important when a building is subjected to high levels of shaking. In some cases, a single model of a building with concrete shear walls may not be suitable to predict properly the behavior of the building under different ground motions.</p></div>Amaia MartinezCarlos E. Ventura
Copyright (c) 2016 TULPAR Academic Publishing
2016-03-152016-03-1531606810.20528/cjsmec.2016.03.008Design procedure for ductile tension-only seismic bracing with an energy dissipation ring
http://www.challengejournal.com/index.php/cjsmec/article/view/49
<div><p class="CJ-Abstracttext">This paper will present a design solution for a ductile, tension–only seismic bracing with the use of an energy dissipating ring. This type of bracing behaves very well under seismic loading and has shown, by testing carried out in conjunction with the University of British Columbia, that it can reach very high post elastic drift limits. The presented procedure is a method created by the author and is based on information collected during the research testing program performed by the Civil Engineering Department at the University of British Columbia. The team was led by Professor Carlos Ventura, in collaboration with Dejan Erdevicki from Erdevicki Structural Engineering. The presented design procedure describes the behaviour of the system, the relation between energy, forces, drift limits and capacities of the ring. It also includes geometrical limitations and requirements for the ring element and bracing system, to ensure that target drifts can be achieved. It allows the user to calculate seismic forces and reduction factors based on an energy criterion and the chosen final drift of the structure. For longer period structures, an equal displacement principle was discussed and considered. The procedure can be used for seismic capacity design and is easily adjusted to suit applicable national codes. Ring capacity tables and examples are also included. This ductile, tension–only bracing, with an energy dissipating ring, can be used for new structures, as well as for the retrofit of existing ones. The system is relatively simple and allows for easy replacement of the ring after an earthquake event if needed. The application of the bracing system for buildings, including multi-storey structures, will be discussed.</p></div>Dejan Erdevicki
Copyright (c) 2016 TULPAR Academic Publishing
2016-03-152016-03-1531142410.20528/cjsmec.2016.02.003Cover & Contents Vol.2 No.1
http://www.challengejournal.com/index.php/cjsmec/article/view/57
Journal Management CJSMEC
Copyright (c) 2016 TULPAR Academic Publishing
2016-03-152016-03-1531Impact of adjacent footings on immediate settlement of shallow footings
http://www.challengejournal.com/index.php/cjsmec/article/view/42
<div><p class="CJ-Abstracttext">When the settlement of a footing under a structure is estimated by considering the bearing pressure of that footing only, the estimated value of the settlement may not be good enough since the other neighboring footings are going to effect the settlement of the footing under consideration also. Thus, in the settlement estimation of a footing, the effect of neighboring footings must be considered. In this study, impact of adjacent footings is considered on the estimation of elastic settlement of shallow foundations. In the estimation of elastic (immediate) settlement, the Schmertmann’s method that is a very popular method in the elastic settlement estimation of shallow foundations is employed. In order to consider effect of neighboring footings on elastic settlement of main footing in different configurations, a MATLAB script has been generated. Elastic settlements of the various configurations are estimated by the script and several conclusions have been reached.</p></div>Mustafa Aytekin
Copyright (c) 2016 TULPAR Academic Publishing
2016-03-152016-03-15311610.20528/cjsmec.2016.01.001Some open issues in the seismic design of bridges to Eurocode 8-2
http://www.challengejournal.com/index.php/cjsmec/article/view/48
<div><p class="CJ-Abstracttext">This paper summarises the ongoing research on the seismic design of isolated and integral bridges at the University of Surrey. The first part of the paper focuses on the tensile stresses of elastomeric bearings that might be developed under seismic excitations, due to the rotations of the pier cap. The problem is described analytically and a multi-level performance criterion is proposed to limit the tensile stresses on the isolators. The second part of the paper sheds light on the response of integral bridges and the interaction with the backfill soil. A method for the estimation of the equivalent damping ratio of short-span integral bridges is presented to enable the seismic design of short period bridges based on Eurocode 8-2. For long-span integral bridges, a novel isolation scheme is proposed for the abutment. The isolator is a compressible inclusion comprises tyre derived aggregates (TDA) and is placed between the abutment and a mechanically stabilised backfill. The analysis of the isolated abutment showed that the compressible inclusion achieves to decouple the response of the bridge from the backfill. The analyses showed that both the pressures on the abutment and the settlements of the backfill soil were significantly reduced under the thermal and the seismic movements of the abutment. Thus, the proposed decoupling of the bridge from the abutment enables designs of long-span integral bridges based on ductility and reduces both construction and maintenance costs.</p></div>Stergios A. Mitoulis
Copyright (c) 2016 TULPAR Academic Publishing
2016-03-152016-03-153171310.20528/cjsmec.2016.02.002The collapse of WTC 7: A re-examination of the “simple analysis” approach
http://www.challengejournal.com/index.php/cjsmec/article/view/50
<div><p class="CJ-Abstracttext">Although the events of that tragic day happened 14 years ago, there remain nagging questions of why the 47 storey WTC 7 steel framed structure collapsed, when it was NOT hit by an airplane. We will review the official rationale of how the collapse events started, and why, in our opinion, the explanation is judged to be wrong. Then, we will proceed with another scenario that says “Okay – let’s assume that the two critical storeys did sustain extremely hot fires, so much so that 2/3rds of their columns totally lost axial resistance capability”. We then proceed to employ Newton’s laws to inquire whether there was sufficient gravitational potential energy due to live and dead loadings in upper and lower floors to overcome the resistance offered by the remaining columns, together with floor slabs known to have been pulverized to reduced particle sizes by surface to surface crushing. Our conclusion suggests that Newton’s laws of motion and energy conservation considerations would have had to have been violated to explain that building’s total collapse within a debris pile several storeys high.</p></div><strong>Supplementary Sources:<br /> </strong><p><a href="https://vid.me/u0gZ">Clip from "9-11 in the Academic Community"</a></p>Robert KorolPaul HeeremaKen Sivakumaran
Copyright (c) 2016 TULPAR Academic Publishing
2016-03-152016-03-1531253110.20528/cjsmec.2016.02.004Seismic performance of a pre-cast concrete arch system
http://www.challengejournal.com/index.php/cjsmec/article/view/52
<div><p class="CJ-Abstracttext">Lock Block Ltd of Vancouver, Canada produces pre-cast concrete products, including their name-sake retaining wall system which uses recycled materials. More recently they have adapted these products to create a system of easy to assemble dome and arch structures. This study aims to evaluate the behavior of these systems when subjected to seismic loading. A program of experimental shake-table testing was undertaken using a small scale arch models. For the tests, a suite of six earthquake records were chosen, including Tohoku 2011, Loma Prieta 1989 and Kobe 1995. The records were time scaled to increase the applied frequencies to the tested models; the accelerations were applied full-scale. For each model, they were tested with increasing intensity until failure occurred; this determined the failure level for each earthquake. For all the cases, the failure mode exhibited the typical four-hinge mechanism. The failure intensity varied with type of earthquake, with impulses being the dominant factor. The study also explored a method of reinforcing the arches, using a steel band over the structure to withstand the tension force, anchored at both ends of the arch. This method performed well to all applied earthquakes.</p></div>Amaia MartinezMartin E. TurekCarlos E. VenturaJay Drew
Copyright (c) 2016 TULPAR Academic Publishing
2016-03-152016-03-1531323710.20528/cjsmec.2016.02.005Vertical and lateral horizontal forces of walking area running pedestrians
http://www.challengejournal.com/index.php/cjsmec/article/view/54
<div><p class="CJ-Abstracttext">The authors have noticed the newest observations and few analysis of excitation mechanism. Therefore they prepared the series of vertical and lateral forces measurements due to steps of walking, running persons on horizontal plane, on inclined plane and on stairway. They suppose that the import knowledge of the forces frequencies of step or strides for different walking velocities is the most important for the further analysis and analysis of the mechanisms. The time histories of lateral forces of a pedestrian were registered and statistical analyzed: the authors received the lateral force dependence on the walking velocity, on stride length an on the weight of pedestrian. The new research step is focused on lateral horizontal forces.</p></div>Shota UrushadzeMiroš Pirner
Copyright (c) 2016 TULPAR Academic Publishing
2016-03-152016-03-1531385010.20528/cjsmec.2016.03.006The boundary integral equation based method for damages detection in multilayered elastic structures
http://www.challengejournal.com/index.php/cjsmec/article/view/55
<div><p class="CJ-Abstracttext">For two kinds of defects – delamination and transversal failure in the multilayer composite the damages detection method is proposed. The inverse geometrical problems of crack’s parameters reconstruction were formulated as a sequence of boundary integral equations (BIE). These boundary integral equations were derived on the basis of the principle of works mutuality applied to the problem of the composite specimen stationary oscillations. To solve the integral equations the finite element method, the boundary element method, and the Tikhonov regularization method were used. As complementary information for inverse problems solving the displacement field measured on a mechanical stress free area of the specimen’s surface was served. The numerical examples of the interfacial cracks and transversal failure of the internal layers in the multilayered composite were considered in the framework of two-dimensional elasticity.</p></div>Arcady N. SolovievAlexander O. VatulyanSergey N. ShevtsovAlexander S. Spogakin
Copyright (c) 2016 TULPAR Academic Publishing
2016-03-152016-03-1531515910.20528/cjsmec.2016.03.007Seismic performance evaluation of an existing school building in Turkey
http://www.challengejournal.com/index.php/cjsmec/article/view/24
<div><p class="CJ-Abstracttext">A great part of existing RC structures built in Turkey is that they have been designed without considering seismic-induced actions and seismic criteria for strength and ductility design. In this context, after the recent devastating earthquakes in Turkey, there has been a concerted effort to address the seismic vulnerability of existing public buildings in Turkey. The need for the evaluation and strengthening of these public buildings have come into focus following the enormous loss of lives and property during the past earthquakes. This study aims to assess the seismic performance evaluation of a typical school building in accordance with the rules of Turkish Earthquake Code-2007. The performance analysis is carried out by using nonlinear static analysis. The analytical solutions show that the intended performance level has not been satisfied for this building and decided to retrofit the structural system. The proposed procedure is applied to the retrofitted system and the obtained results are tabulated and discussed.</p></div>Hüseyin Bilgin
Copyright (c) 2015 TULPAR Academic Publishing
2015-12-072015-12-073116116710.20528/cjsmec.2015.07.020A substructure based parallel dynamic solution of large systems on homogeneous PC clusters
http://www.challengejournal.com/index.php/cjsmec/article/view/27
<div><p class="CJ-Abstracttext">This study focuses on developing a parallel solution framework for the linear dynamic analysis of large structural models on homogeneous PC clusters. The framework consists of two separate stages where the former is preparing data for the parallel solution that involves partitioning. The latter is a fully parallel finite element analysis that utilizes substructure based solution approach with direct solvers to perform implicit integration. The linear dynamic analysis of a large scale model was performed on a homogeneous PC cluster and the number of computers was varied in order to demonstrate the performance and the efficiency of the overall solution framework. The performance of the implemented framework was also compared with the widely acknowledged parallel direct solver, MUMPS.</p></div>Semih ÖzmenTunç BahçecioğluÖzgür Kurç
Copyright (c) 2015 TULPAR Academic Publishing
2015-12-072015-12-073115616010.20528/cjsmec.2015.07.021Dynamic vibration analysis of ballastless track: Istanbul Aksaray-Airport LRT System
http://www.challengejournal.com/index.php/cjsmec/article/view/29
<div><p class="CJ-Abstracttext">In this study, ballastless superstructure with a steel base-plate of light metro track, which lies between Aksaray and the Airport in Istanbul, was analyzed with a numeric method using ANSYS 9.0 finite element software. Since the railroad superstructure has a symmetric structure with respect to the track axis, a rail system that consists of a single rail and a half sleeper was modeled to simplify the computations in this analysis. In the discrete supported track model, the rail was modeled as an Euler-Bernoulli beam and steel base-plate, and it was assumed to be a rigid mass. Dynamic computation results and graphs were determined by performing harmonic analysis with the aid of ANSYS software. A field vibration survey was conducted to determine the natural frequencies of the railroad and the dynamic receptance behavior, and to validate the finite element model according to the measurement results. The frequency receptance behavior of the rail and the support was measured by applying a hammer impact load on the rail head in the field, and the finite element model of the ballastless track with steel base-plate was verified.</p></div>Veysel ArlıTurgut ÖztürkZübeyde Öztürk
Copyright (c) 2015 TULPAR Academic Publishing
2015-12-072015-12-073119219710.20528/cjsmec.2015.07.026Seismic analysis of offshore wind turbine including fluid-structure-soil interaction
http://www.challengejournal.com/index.php/cjsmec/article/view/30
<div><p class="CJ-Abstracttext">This paper presents the seismic response analysis of offshore wind turbines subjected to multi-support seismic excitation by using a three dimensional numerical finite element model considering viscous boundaries. The sea water-offshore wind turbine-soil interaction system is modeled by the Lagrangian (displacement-based) fluid and solid-quadrilateral-isoparametric finite elements. The research conducts a parametric study to estimate the effects of different foundation soil types on the seismic behavior of the offshore wind turbine coupled interaction system. The results obtained for different cases are compared with each other.</p></div>Kemal HacıefendioğluFahri Birinci
Copyright (c) 2015 TULPAR Academic Publishing
2015-12-072015-12-073119820110.20528/cjsmec.2015.07.027