Publisher: TULPAR Academic Publishing   (Total: 2 journals)   [Sort by number of followers]

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Challenge J. of Concrete Research Letters     Open Access   (Followers: 5)
Challenge J. of Structural Mechanics     Open Access   (Followers: 6)
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Challenge Journal of Structural Mechanics
Number of Followers: 6  

  This is an Open Access Journal Open Access journal
ISSN (Online) 2149-8024
Published by TULPAR Academic Publishing Homepage  [2 journals]
  • Cover & Contents Vol.6 No.1

    • Authors: Journal Management CJSMEC
      PubDate: 2020-03-25
      Issue No: Vol. 6, No. 1 (2020)
  • An investigation on determining optimum wall ratio–cost relationship of
           shear walled reinforced concrete buildings

    • Authors: İbrahim Hakkı Erkan, Talha Polat Doğan, Musa Hakan Arslan
      Pages: 1 - 9
      Abstract: Reinforced concrete walls are very efficient structural elements in terms of carrying the lateral loads that are expected to affect the structures during the service of the buildings. These elements, which are not used for economic reasons in buildings designed in areas with low seismic hazard, can actually provide a significant increase in performance with a very small increase in construction cost. In this study, a total of 9 building models have been created and the relationship between optimum reinforced concrete wall ratio and cost on these buildings has been investigated. The design and analysis of the models were carried out according to the criteria specified in TSC 2018. Three different structural systems specified in TSC 2018 were used in the designed models. These structural systems used; RC frame structures, RC wall-frame structures and RC wall structures. These structures were analyzed by Response Spectrum Method which is linear analysis method and base shear forces were obtained. Then, push-over analysis, which is a nonlinear analysis method, was applied to obtain the base shear forces that the structure can actually carry. After the analysis, the quantities of materials to be used for the construction of the structural systems of the models were calculated and current manufacturing prices and rough costs were calculated. In order to compare the obtained costs with the structural performances, nonlinear shear forces and linear shear forces ratios were calculated and the over strength factors were calculated for each model. In the light of the data obtained from the studies in the literature, when the over strength factors and cost values are examined together, it is concluded that the optimum design for the conditions specified in TSC 2018 will be provided with the RC wall ratio between 0.001 - 0.0016. It is concluded that lateral load carrying capacity of construction increases up to 650% by increasing the construction cost by 17% for the designed models.
      PubDate: 2020-03-25
      DOI: 10.20528/cjsmec.2020.01.001
      Issue No: Vol. 6, No. 1 (2020)
  • Evaluation of performance-based earthquake engineering in Yemen

    • Authors: Sulaiman Al-Safi, Ibrahim Abdullah Alameri, Rushdi A. M. Badhib, Mahmoud Kuleib
      Pages: 10 - 22
      Abstract: Building codes follow a common concept in designing buildings to achieve an acceptable seismic performance. The objective underlying the concept is to ensure that the buildings should be able to resist minor earthquake without damage, resist moderate earthquake with some non-structural damage, and resist major earthquakes without collapse, but some structural as well as non-structural damage. This study aims to evaluate the performance-based seismic to come up with necessary recommendations for both future practices, essential review, and restoration of existing structures in Yemen. To do this real case studies incorporated, and nonlinear pushover analysis is carried out. The analysis results presented and then assessed to find out the conformity with the required performance. The structural sections assumed at the beginning of the design, then the design repeated many times to achieve the selected performance criteria (the plastic hinge properties and the maximum displacement).
      PubDate: 2020-03-25
      DOI: 10.20528/cjsmec.2020.01.002
      Issue No: Vol. 6, No. 1 (2020)
  • Investigating the synergy between lean construction practices and post
           disaster management processes

    • Authors: Sevilay Demirkesen
      Pages: 23 - 30
      Abstract: Lean aims to maximize value while minimizing waste. Lean practices are likely to reduce the number potential hazards and errors. The use of Lean practices in construction is essential to experience less hazards. Benefitting from Lean practices has gained much attention in the last decade. Especially, the destroying effect of hazards and accidents is of utmost importance in terms of seeking for better strategies. Within this context, Lean practices offer a wide variety of advantages and provide means for achieving greater success in projects. This study investigates the use of Lean practices in post disaster management. Since post disaster management includes the activities to help community in rebuilding, Lean tools and techniques might be employed to better handle post disaster management processes. The study also scrutinizes the integration of Lean practices with the post disaster processes and encourages the community to compete against the destroying effect of disasters thanks to using Lean tools and techniques. The main contribution of this study is that it introduces Lean practices to be used in the post disaster management processes, which might potentially remove safety concerns in construction sites up to a great extent.
      PubDate: 2020-03-25
      DOI: 10.20528/cjsmec.2020.01.003
      Issue No: Vol. 6, No. 1 (2020)
  • Effect of configuration of shear walls at story plan to seismic behavior
           of high-rise reinforced concrete buildings

    • Authors: Mustafa Tolga Çöğürcü, Mehmet Uzun
      Pages: 31 - 40
      Abstract: In developing countries, the need for shelter, working area, shopping and entertainment centers is increasing due to the increasing population effect. In order to meet this need, it is necessary to turn to high-rise buildings. Significant damages have been observed as a result of insufficient horizontal displacement stiffness of high-rise buildings in major earthquakes in previous years. It is known that as the height of the structure increases, the displacement demand of the structure also increases. Since it is accepted that the structure will make inelastic deformation in the design of the structure, these displacements increase to very high levels as the number of stories increases. For this reason, damages can be much higher than expected. In order to limit the level of damage that may occur in high-rise buildings, the horizontal displacement of buildings is limited in many regulations in our age. This limitation is possible by increasing the rigidity of the structures against horizontal displacement. In recent years, the use of shear wall has increased due to the horizontal displacement limitation in the regulations. The use of shear walls in buildings limits the horizontal displacement. However, the choice of where the shear walls will be placed on the plan is very important. Failure to place the shear walls correctly may result in additional loads in the structure. It can also lead to torsional irregularity. In this study, a 10-storey reinforced concrete building model was created. Shear wall at the rate of 1% of the plan area of the building was used in the building. The shear walls are arranged in different geometric shapes and different layouts. The earthquake analysis of 5 different models were performed. Equivalent Earthquake Load, Mode Superposition and Time History Analysis methods were used for earthquake analysis. The results were compared and a proposal was made for the geometry and configuration of the shear wall.
      PubDate: 2020-03-25
      DOI: 10.20528/cjsmec.2020.01.004
      Issue No: Vol. 6, No. 1 (2020)
  • Model updating of a reduced-scaled masonry bridge by using response
           surface method

    • Authors: Emre Alpaslan, Zeki Karaca
      Pages: 41 - 51
      Abstract: Historical structures reflect the historical and cultural properties of countries and also contributes to the economy in terms of cultural tourism. Therefore, it is important to understand the structural behavior of these kinds of structures under dynamics loads such as earthquakes, etc. to protect and transfer them safely to future generations. For this reason, this study aims to investigate the dynamic behavior of a reduced-scale one-span masonry arch bridge constructed in laboratory conditions by performing experimental and numerical analysis. Operational Modal Analysis (OMA) Technique was performed under ambient vibrations for experimental study to determine modal parameters of the reduced-scaled bridge model. Sensitive three-axial accelerometers were located on critical points on the bridge span and signals originated by accelerometers were collected to quantify the vibratory response of the scale bridge model. The experimental natural frequencies, mode shapes and damping ratios resulting from these measurements were figured out by using Enhanced Frequency Domain Decomposition (EFDD) technique. ANSYS software was utilized to carry out 3D finite element (FE) modeling of the reduced-scale masonry bridge and determine the natural frequencies and mode shapes of the bridge numerically. Experimental results were compared with FE analysis results of the bridge. Significant differences appeared when comparing the results of the experimental and numerical with the initial conditions. Therefore, the finite element model is calibrated by using the response surface (RS) method according to the experimental results to minimize the uncertain finite element modeling parameters of the reduced-scale bridge model such as material properties.
      PubDate: 2020-03-25
      DOI: 10.20528/cjsmec.2020.01.005
      Issue No: Vol. 6, No. 1 (2020)
  • Cover & Contents Vol.5 No.4

    • Authors: Journal Management CJSMEC
      PubDate: 2019-12-02
      Issue No: Vol. 5, No. 4 (2019)
  • Analysis of historical structures by using finite element method in Iznik
           Yeşil Mosque

    • Authors: Aykut Uray, Hasan Selim Şengel, Serdar Çarbaş
      Pages: 121 - 129
      Abstract: In this study, non-destructive tests and laboratory tests were carried out in order to determine the material properties in Iznik Yeşil Mosque, Iznik District, Bursa Province. For the purpose of determining the soil characteristics of the building, the soil survey studies conducted in the Iznik Yeşil Mosque area were investigated. The finite element model was formed by making a three dimensional model study of the structure. With the finite element model, static analysis, modal analysis and behavioral spectrum analysis were performed under vertical loads in order to collect data for the damaged areas of the structure.
      PubDate: 2019-12-02
      DOI: 10.20528/cjsmec.2019.04.001
      Issue No: Vol. 5, No. 4 (2019)
  • Optimization of PID controller parameters for active control of single
           degree of freedom structures

    • Authors: Serdar Ulusoy, Sinan Melih Niğdeli, Gebrail Bekdaş
      Pages: 130 - 140
      Abstract: In active control of structures, the parameters of controllers used application must be perfectly tuned. In that case, a good vibration reduction performance can be obtained without a stability problem. During the tuning process, the limit of control force and time delay of controller system must be considered for applicable design. In the study, the optimum parameters of Proportional-Derivative-Integral (PID) type controllers that are proportional gain (K), integral time (Ti) and derivative time (Td) were optimized by using teaching learning-based optimization (TLBO). TLBO is a metaheuristic algorithm imitating the teaching and learning phases of education in classroom. The optimization was done according to the responses of the structure under a directivity pulse of near fault ground motions. In the study, time delay was considered as 20 ms and the optimum parameters of PID controller for a single degree of freedom (SDOF) structural model was found for different control force limits. The performances and feasibility of the method were evaluated by using sets of near fault earthquake records.
      PubDate: 2019-12-02
      DOI: 10.20528/cjsmec.2019.04.002
      Issue No: Vol. 5, No. 4 (2019)
  • Comparison of equivalent seismic load and response spectrum methods
           according to TSC 2018 and TSC 2007

    • Authors: İbrahim Hakkı Erkan, Talha Polat Doğan
      Pages: 141 - 153
      Abstract: In this study, two different analysis methods were compared; the first is a linear static analysis method and the second is a linear dynamic analysis method. First one is the Equivalent Seismic Load Method, which is a linear static method where seismic loads can be obtained by applying a simple calculation. The second method, the Response Spectrum method, is a linear dynamic analysis method which obtains the seismic loads using more complex statistical calculations. For this analysis study, 18 structural models with 3 different building heights were analyzed according to the conditions of Equivalent Seismic Load Method and Response Spectrum Method specified in both TSC 2007 and TSC 2018 and base shear forces obtained as a result of these analyzes were compared. As a result of analysis; compared to the results obtained from TSC 2007, due to the effective stiffness coefficients specified in TSC 2018, it was observed that the base shear forces obtained for both methods were lower and the modal period values were longer in the analyzes applied according to TSC 2018. This means that the structural systems created with the designs according to TSC 2018 are more ductile than the structural systems created with the designs made according to TSC 2007. Base shear forces obtained by 2 different analysis methods applied according to regulations stated in both TSC 2018 and TSC 2007; it was observed that the base shear forces obtained by the Equivalent Seismic Load Method were higher than the results of the Response Spectrum Method.
      PubDate: 2019-12-02
      DOI: 10.20528/cjsmec.2019.04.003
      Issue No: Vol. 5, No. 4 (2019)
  • Modification of the effective area method on two-way loaded shallow

    • Authors: Mustafa Aytekin
      Pages: 154 - 160
      Abstract: In rectangular/square based and two-way loaded (two-way eccentric) shallow foundations, four zones in which the resultant load might act are defined in the effective area method. Three out of the four zones that are employed in the determination of the effective areas overlap around kern. Only one zone that has a triangular-shaped effective area (called as case 1 in the literature) out of the four zones has no overlap with the others. The resultant load will always be out of the kern for case 1, and also it might be out of the kern for the remaining three cases. Design of foundations is not acceptable in general if the resultant load acts out of the kern. In the present study, the four cases are reconsidered. The zones on which the resultant load can be acting for the four cases are modified because these zones are overlapped partly. The modification has been made to have clear borders between the zones. On top of that, zone 4 is divided into two. A new zone corresponding to the area of kern is defined as zone 5. The design will be accepted if the resultant load acts within zone 5 (the kern). Also, the graphs in use to determine the dimensions of the effective areas are eliminated since it is not precise. Formulas are derived to determine the dimensions of the effective areas instead of using the graphs. Two new criteria are discovered and proposed to check whether the resultant load acts outside, inside or on the borderline of zone 5 (the kern).
      PubDate: 2019-12-02
      DOI: 10.20528/cjsmec.2019.04.004
      Issue No: Vol. 5, No. 4 (2019)
  • Cover & Contents Vol.5 No.3

    • Authors: Journal Management CJSMEC
      PubDate: 2019-09-11
      Issue No: Vol. 5, No. 3 (2019)
  • Utilization of ceramic waste in the production of Khorasan mortar

    • Authors: Hasan Selim Şengel, Mehmet Canbaz, Ersin Güler
      Pages: 80 - 84
      Abstract: Khorasan mortar was used in almost all of the historical structures in the geographical area of turkey. It is still used in the renovation of these structures. Water, lime, baked clay is used in the production of Khorasan by breaking and grinding. Crushed brick and tiles are preferred as baked clay. In this study, the usability of ceramic wastes as baked clay was investigated. An important part of ceramic production is made especially in Eskişehir and its vicinity. 10% of ceramic production shows up as wastes because of various reasons. These wastes which are under 20 mm are crushed in the jaw breakers and these which are under 150 mm are grinned in grinders, transformed to powder and then mixed with hydrated lime and water in various proportions, in this way Khorasan mortars are obtained. In mortar production, crushed ceramic-ceramic powder ratio, ceramic-lime ratio were changed and the most suitable ratios were tried to be found. Samples taken from these mortars which are 4 cm x 4 cm x 16 cm in size are removed after a day from the mold and kept in humid environment. Physical and mechanical properties such as unit weight, ultrasonic pulse velocity, bending strength, compressive strength of the mortar were determined. As a result of the experiments, the unit weights range was between 1.5–1.65 kg/dm3, the ultrasonic pulse velocity rates range from 1.3–1.9 km/h, the range of bending strengths was from 0.25–1.05 MPa, and compressive strength has changed in the range of 7.5–10.5 MPa. With the work done, it is recommended to use a high percentage of lime while using ceramic wastes in the process of producing Khorasan mortar.
      PubDate: 2019-09-11
      DOI: 10.20528/cjsmec.2019.03.001
      Issue No: Vol. 5, No. 3 (2019)
  • The impact of design approach and contracting practices on cost and
           execution period of school buildings

    • Authors: Abdullatif A. AlMunifi, Ibrahim Abdullah Alameri
      Pages: 85 - 95
      Abstract: More than two million school-age children in Yemen are unable to enroll in education because of a shortage of school buildings. This is one of the reasons the country missed the Millennium Development Goal of achieving Education for all by 2015. The struggle to afford school accommodation will continue, because of the lack of resources and high unit cost. Construction cost as time schedule for an identical school building vary by the implementing agency. This paper aims to study in-depth this multi-dimensional issue to find out the factors that lead to this variation, as well as the reasons for the high unit cost and lengthy periods of construction. To achieve this objective, comprehensive raw data that was resourced from agencies that are assigned to implement the largest part of the construction program along with data collected through questionnaires and semi-structured interviews were utilized. Complete sets of design and contracting documents of representative schools were used for deeper analysis and evaluation. The analysis shows that the employed design approaches lead to large structural elements and consequently to longer implementation period and 30% increase in cost. It also shows that contractors add up to 20% for the client’s procurement procedure, approvals, and payment cycle. Additionally, bidders price risks related to accessibility to building sites, availability of building materials, and how trouble-prone is the region. The findings are of relevance to researchers, education planners, and practitioners as they are of high importance to policy makers and financiers whose main concern is to meet the growing need for school accommodation.
      PubDate: 2019-09-11
      DOI: 10.20528/cjsmec.2019.03.002
      Issue No: Vol. 5, No. 3 (2019)
  • Numerical modelling of heat transfer through protected composite
           structural members

    • Authors: Burak Kaan Çırpıcı, Süleyman Nazif Orhan, Türkay Kotan
      Pages: 96 - 107
      Abstract: Among many various types of passive fire protection materials (i.e. plaster boards, sprayed materials and intumescent coatings) thin film intumescent coatings have become the preferable option owing to their good advantages such as flexibility, good appearance (aesthetics), light weight to the structure and fast application. Despite their popularity, there is also a lack of good understanding of fire behaviour. In general, experimental methods are used to push this knowledge with labour and high-energy consumption and extremely expensive processes. With the development of computer technology, numerical models to predict the heat transfer phenomena of intumescent coatings have been developed with time. In this work, the numerical model has been established to predict the heat transfer performance including material properties such as thermal conductivity and dry film thickness of intumescent coating. The developed numerical model has been divided into different layers to understand the sensitivity of steel temperature to the number of layers of intumescent coating and mesh sizes. The temperature-dependent thermal conductivity of intumescent coatings can be calculated based on inverse solution of the equation for calculating temperatures in protected steel according to the Eurocodes (EN 1993-1-2 and EN 1994-1-2). However, as the temperature distribution in the intumescent coatings is highly non-uniform, that Eurocode equation does not give accurate coating thermal conductivity-temperature relationship for use in numerical heat transfer modelling when the coating is divided into a number of layers, each having its characteristic thermal conductivity values. The comparison study of steel temperature under Standard (ISO 834) and Fast fire conditions against Eurocode analytical solution has also been made by assuming both constant thermal conductivity and variable thermal conductivity. The obtained results show close agreement with the Eurocode solution choosing a minimum certain mesh, number of layer and best-fitted thermal conductivity of the intumescent coating.
      PubDate: 2019-09-11
      DOI: 10.20528/cjsmec.2019.03.003
      Issue No: Vol. 5, No. 3 (2019)
  • Parametric investigation for discrete optimal design of a cantilever
           retaining wall

    • Authors: Esra Uray, Serdar Çarbaş, İbrahim Hakkı Erkan, Özcan Tan
      Pages: 108 - 120
      Abstract: In this paper, discrete design optimization of a cantilever retaining wall has been submitted associated with a detailed parametric study of the wall. In optimal design, the minimum wall weight is treated as the objective function. Through design algorithm, the optimal design variables (base width, toe width, thickness of base slab and angle of front face) yielded minimum structural weight of the wall and satisfied stability conditions have been determined for different soil parameter values. At the end, a detail parametric study searching the effect of change of soil parameters on the retaining wall design has been conducted with 120 optimized wall designs for different values; eight values of the angle of internal friction, three values of the unit volume weight and five values of wall heights. The obtained results from optimization analyses indicate that change of the angle of internal friction more effective than change of the unit volume weight on the optimal wall weight. Economic wall design with optimization analysis is achieved in a shorter time than the traditional method.
      PubDate: 2019-09-11
      DOI: 10.20528/cjsmec.2019.03.004
      Issue No: Vol. 5, No. 3 (2019)
  • Cover & Contents Vol.5 No.2

    • Authors: Journal Management CJSMEC
      PubDate: 2019-06-11
      Issue No: Vol. 5, No. 2 (2019)
  • Effect of basalt, polypropylene and macro-synthetic fibres on workability
           and mechanical properties of self-compacting concrete

    • Authors: Zinnur Çelik, Ahmet Ferhat Bingöl
      Pages: 35 - 41
      Abstract: In this study, the effects of different fibre types on the workability and mechanical properties of self-compacting concrete were investigated. Fresh and hardened properties of self-compacting concrete, different fibre content 0.90, 1.35 and 1.80 kg/m3 were evaluated using basalt, polypropylene and macro synthetic fibres with different fibre lengths of 24, 19 and 40 mm, respectively. The properties of fresh concrete were evaluated in terms of slump flowing, viscosity and flowability. In addition, compressive, flexural and splitting tensile strength were obtained from hardened concrete properties. To characterize mechanical properties 90 specimens were experimentally tested. The results show that the use of fibre reduces the workability of self-compacting concrete. On the other hand, tensile and flexural strength of the self-compacting fibre reinforced concrete increased with increasing fibre content, but it was determined that the fibre addition had no significant effect on the compressive strength.
      PubDate: 2019-06-11
      DOI: 10.20528/cjsmec.2019.02.001
      Issue No: Vol. 5, No. 2 (2019)
  • A comparative study of concrete strength prediction using artificial
           neural network, multigene programming and model tree

    • Authors: Preeti Kulkarni, Shreenivas N. Londhe, Pradnya R. Dixit
      Pages: 42 - 61
      Abstract: In the current study 28 day strength of Recycled Aggregate Concrete (RAC) and Fly ash (class F) based concrete is predicted using Artificial Neural Network (ANN), Multigene Genetic Programming (MGGP) and Model Tree (MT). Four sets of models were designed for per cubic proportions of materials, Properties of materials and non-dimensional parameters as input parameters. The study shows that the predicted 28 day strength is in good agreement with the observed data and also generalize well to untrained data. ANN outperforms MGGP and MT in terms of model performance. Output of the developed models can be presented in terms of trained weights and biases in ANN, equations in MGGP and in the form of series of equations in MT. ANN, MGGP and MT can grasp the influence of input parameters which can be seen through Hinton diagrams in ANN, input frequency distribution in MGGP and coefficients of input parameters in MT. The study shows that these data driven techniques can be used for developing model/s to predict strength of concrete with an acceptable performance.
      PubDate: 2019-06-11
      DOI: 10.20528/cjsmec.2019.02.002
      Issue No: Vol. 5, No. 2 (2019)
  • Structural analysis of reinforced concrete mansard roof structures
           according to different structural plans

    • Authors: Hasan Selim Şengel, İsmail Kanber, Serdar Çarbaş
      Pages: 62 - 71
      Abstract: In this study, analysis and evaluations were carried in order to determine the optimum conditions of reinforced concrete mansard roof applications. In total 96 mansard and 24 non mansard structure analysis were performed. The constructed models are symmetrical from all directions and it is modeled under the minimum conditions allowed by the regulation. As the column span, the distance between the columns was determined as 4 meters. The span conditions were determined as 3 spans, 4 spans, 5 spans and 6 spans by evaluating the parcel sizes and zoning conditions. Thus, a total of 120 calculation models were created. The base shear force, column moments and the maximum top displacement values were discussed in concordance with these calculations. As a result of the analysis, the graphical values of the mansard buildings were examined along with the non mansard buildings from the 3rd floor to the 8th floor, according to the zoning plan. In this study, graphs of parcels, span values and the number of storeys were drawn by keeping the values constant, and evaluations were made on the same graphs with and non mansard. In addition, by looking at the movements of the graphs obtained from this study on the same series, equations were adapted to the graphs and the series created with these equations were expanded and stochastic parabolic cones were formed at the shear force for 10 storeys, in the column moments. The mean values for the top displacement chart were taken and when the 20-storey displacement value was placed on this curve, it was determined that it appeared at a point very close to the estimating equation curve. Based on the analysis results, it is understood that it is possible to create a set of estimations for different number of storeys and plans.
      PubDate: 2019-06-11
      DOI: 10.20528/cjsmec.2019.02.003
      Issue No: Vol. 5, No. 2 (2019)
  • Arch effect in silos on discrete supports - Is it a myth or reality'

    • Authors: Lyubomir A. Zdravkov
      Pages: 72 - 79
      Abstract: Steel silos are interesting, complicated facilities. In order to assure its complete emptying by gravity they are often placed on supporting frame structure above the ground. Values of stresses in joints between thin walled shell and supporting frame elements are very high. It can cause the local buckling in the shell. The simplest way to design steel silos is to divide hypothetically the cylindrical shell into two parts - ring beam, supported in some points and shell above, uniformly supported. This conception is accepted by European Standard EN 1993-4-1. The particular moment is that the ring beam and cylindrical body above it are separated. Actually the two elements are jointed and work together in the same time. Considering the last results of Zeybek, Topkaya and Rotter from 2019, and as well as his own research, the author asks the question if it is true that the transferring of discrete base reactions to the cylindrical body is done by bending work of the ring beam, which is the conception in EN 1993-4-1' Or the vertical reaction forces are actually redistributed on the height based on the work of the cylindrical shell under compression as an arch. Using the contemporary capabilities of the programs for spatial analysis of building structures the author will try to find the answer of this question.
      PubDate: 2019-06-11
      DOI: 10.20528/cjsmec.2019.02.004
      Issue No: Vol. 5, No. 2 (2019)
  • Cover & Contents Vol.5 No.1

    • Authors: Journal Management CJSMEC
      PubDate: 2019-03-12
      Issue No: Vol. 5, No. 1 (2019)
  • Estimation of capacity of eccentrically loaded single angle struts with
           decision trees

    • Authors: Saha Dauji
      First page: 1
      Abstract: Single angle struts are used as compression members for many structures including roof trusses and transmission towers. The exact analysis and design of such members is challenging due to various uncertainties such as the end fixity or eccentricity of the applied loads. The design standards provide guidelines that have been found inaccurate towards the conservative side. Artificial Neural Networks (ANN) have been observed to perform better than the design standards, when trained with experimental data and this has been reported literature. However, practical implementation of ANN poses problem as the trained network as well as the knowhow regarding the application should be accessible to practitioners. In another data-driven tool, the Decision Trees (DT), the practical application is easier as decision based rules are generated, which are readily comprehended and implemented by designers. Hence, in this paper, DT was explored for the evaluation of capacity of eccentrically loaded single angle struts and was found to be robust and yielded comparable accuracy as ANN, and better than design code (AISC). This has enormous potential for easy and straightforward implementation by practicing engineers through the logic based decision rules, which would be easily programmable on computer. For this application, use of dimensionless ratios as inputs for the development of DT was found to yield better results when compared to the approach of using the original variables as inputs.
      PubDate: 2019-02-09
      DOI: 10.20528/cjsmec.2019.01.001
      Issue No: Vol. 4, No. 4 (2019)
  • Dynamic instability of castellated beams subjected to transverse periodic

    • Authors: Sahar Sahib Elaiwi, Boksun Kim, Long-yuan Li
      First page: 9
      Abstract: In this study, an analytical solution is developed for the investigation of free vibration, static buckling and dynamic instability of castellated beams subjected to transverse periodic loading. Bolotin’s method is used to perform the dynamic instability analysis. By assuming the instability modes, the mass, stiffness, and geometric stiffness matrices are derived using the kinetic energy, strain energy and potential of applied loads. Analytical equations for determining the free vibration frequency, critical buckling moment, and excitation frequency of castellated beams are derived. In addition, the influences of the flange width of the castellated beam and the static part of the applied load on the variation of dynamic instability zones are discussed.
      PubDate: 2019-02-11
      DOI: 10.20528/cjsmec.2019.01.002
      Issue No: Vol. 4, No. 4 (2019)
  • Improving the impact resistance of recycled aggregate concretes with
           different types of fibers

    • Authors: Muhammet Gökhan Altun, Meral Oltulu
      First page: 19
      Abstract: In this study, the aim was to use different types of fibers to improve the impact resistance of recycled aggregate concrete (RAC) that normally shows poor performance against mechanical impacts compared to normal concrete (NC). For this purpose, 18 groups of concrete were cast using different parameters. The study examined different types of concrete mixtures where the proportion of RCA (recycled coarse aggregate) used was 30% and 50% respectively, and where steel fiber-reinforcement was used in proportions of 1% and 2%, and polypropylene fiber-reinforcement was used in proportions of 0.1%. While the material performance of RAC compared to NC is analyzed in existing published literature, there is no evidence on whether the use of RCA and hybrid fibers affect the impact properties of concrete. Drop weight impact testing was conducted on test specimens and the impact resistance of these specimens was studied at 28 days. It was observed that the increasing use of RCA reduced the impact resistance. The use of 30% RCA does not significantly influence the strength of concrete. According to the results, the performance of both the NC and RAC was increased with an increase in the volume fractions of steel fiber used. In addition, hybrid fiber-reinforced concretes showed the best results of all the concrete groups.
      PubDate: 2019-03-05
      DOI: 10.20528/cjcrl.2019.01.003
      Issue No: Vol. 4, No. 4 (2019)
  • Research on effect of the quantity and aspect ratio of steel fibers on
           compressive and flexural strength of SIFCON

    • Authors: Nurullah Soylu, Ahmet Ferhat Bingöl
      First page: 29
      Abstract: SIFCON (Slurry Infiltrated Fiber Reinforced Concrete) is a composite which occur hardening of the matrix phase, consists of cement, water, mineral additives, fine sand, water reducing plasticizer, and reinforced with high volume fiber (5–20%). The main difference from the high strength concrete (HSC) is the ductile behaviour at failure. However, the brittleness increases with the strength increase in HSC, SIFCON has a ductile behaviour because of the high volume fiber content, low permeability, high durability. Despite fiber content is 2-3% in fiber reinforced concrete, fiber content may be ten times more in SIFCON and ductility is gained. This concrete is suggested to be used in military buildings against explosion, industrial grounds, airports, and bridge feet. In this study, in order to investigate the compressive and flexural strengths of SIFCON, the aspect ratio and fiber volume of steel fibers were chosen as variable and the effects of these parameters on compressive and flexural strengths were investigated. In the study, steel fibers with aspect ratio of 40, 55, 65, and 80 were used in 0, 4, 8 and 12% ratios. The water/binder ratio was kept constant at 0.35. Silica fume is used 10% and water-reducing plasticizer is used 1.5% of cement by weight. 7 and 28 days cured samples were subjected to compressive and flexural tests and the results were compared. As a result of the tests carried out, increases in both the compressive and flexural strengths of SIFCON specimens were determined with increasing fiber volume up to 8%. Strength reductions were observed at higher ratios. In cases where the fiber volume is too high, it has been seen that the strengths were decreased. The reason of strength reduction can be explained by the difficulty of passing ability of mortar between the fibers. The highest strengths were obtained from fibers with the aspect ratio of 80. Increase in the aspect ratio as well as increases in compressive and flexural strengths have been found.
      PubDate: 2019-02-12
      DOI: 10.20528/cjsmec.2019.01.004
      Issue No: Vol. 4, No. 4 (2019)
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Tel: +00 44 (0)131 4513762

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