Journal of Structural Engineering and Geo-TechniquesJournal of Structural Engineering and Geo-Techniques
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Feed provided by Journal of Structural Engineering and Geo-Techniques. Click to visit.An investigation into a Geocell-reinforced Slope in The Unsaturated Numerical Model
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Considering unsaturation conditions of soil significantly helps to produce relatively real results. Numerical methods have been assumed as conventional methods in soil mechanics to examine soil behavior. However, the accuracy of numerical methods dramatically depends on applying the appropriate behavioral model to solve problems. One of the known elastoplastic models for unsaturated soils is the Barcelona Basic Model which is added to FLAC2D software through codification. Geocell-reinforced slope functions as a beam in the soil due to the three dimensional nature of the reinforcement, i.e. height is included. Furthermore, the reinforcement causes a reduction in slope displacement and an increase in the factor of safety of slope due to its bending characteristics including moment of inertia and consequently bending strength. Moreover, soil unsaturated conditions are applied to the modelling and suction variations in soil are incorporated. This makes the maximum horizontal displacement of slope occur in the upper part of the Geocell layer while the horizontal displacement values for the slope height are substantially reduced below the Geocell layer. Increasing suction, geocell axial force declines by at most 18.5%. As overhead pressure increases, there is an increase in the force concentrated at the soil-geocell interface and the tensile force is consequently enlarged in reinforcements. Sat, 30 Mar 2019 19:30:00 +0100Deep Excavation Hazard Assessment Zoning in District 1 in Shiraz Municipality Using Geographic ...
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This research presents the geotechnical zoning map of district 1 in Shiraz municipality with focus on municipal deep excavation hazard assessment on data from 160 boreholes. For this purpose, the mechanical properties are determined according to the results of direct shear, uniaxial, and SPT tests and then excavation hazard assessment with depths of 3, 6 and 9 m, in situations where the excavation depth of the neighbor foundation is below 0 and 0 to 20 meters have been calculated. Finally, using ArcGIS software, the assessment hazard excavation for 6 different modes was zoned and the zoning map of the assessment hazard excavation with the normal, high and very high hazard index is provided. The zoning maps shows that with increasing depth of excavation, the danger is increased, so that in maps whit depth of excavation of 9 meters, more than 90 percent of points have high hazard index.Sat, 30 Mar 2019 19:30:00 +0100Mix Design Selection For Old and New Generation of SuprePlasticizers
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Determination the optimal mix design plays an important role in order to gain the maximum characteristic strength. This research was conducted as a case study for Manjil tunnel project located in Qazvin-Rasht highway. For this purpose, 18 concrete mix designs were prepared at the study phase of the project with specifications such as conventional water-to-cement ratios of 0.4, 0.5 and 0.6, the use of two generations of new and old conventional superplasticizer in Iran (naphthalene sulphonate and polycarboxylate ether types, respectively) with cement weight percentages of 0.2, 0.4 and 0.6. Superplasticizers are used to increase the fluidity of concrete without adding excess water. The naphthalene sulphonate is a polymeric molecule formed by condensation of naphthalene sulfonic acid and formaldehyde, in which the hydrophilic groups are mainly sulfonic groups. It has been demonstrated that polycarboxylate ether can mitigate plastic shrinkage of matrix because of the reduction of the build-up rate of capillary pressure by polycarboxylate ether. Finally, the optimal water-to-cement ratio and superplasticizer weight percentage were determined. Concrete mix designs with different ages of curing were made (0, 3, 7, 14 and 28 days).Sat, 30 Mar 2019 19:30:00 +0100Behavior Study of Cemented Specimen by Biological Technique after Disturbance
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With the population growth and consequently the requirement for development of civil constructions, it is necessary to design appropriate foundations for resisting structural loads. Soil weakness in bearing capacity of geotechnical elements has forced the researchers to continuously follow a solution to compensate for this deficiency. Within the past two decades, many studies have been carried out regarding the performance of this technique in optimization of the soil. One technique which is nowadays highly considered due to compatibility with the environment, high efficiency and low cost, is Biological Optimization Technique. One of the characteristics of this type of optimization is its ability for recovering after disturbance. In this research it has been tried to analyze the behavior of cemented specimens after disturbance and reconstruction. For this purpose, after construction of cubic specimens with dimensions of 2*6*6 cm and applying the disturbance and reconstruction, their shear strength under different vertical stresses has been evaluated by direct shear test.Thu, 30 May 2019 19:30:00 +0100Determination of Lateral load Capacity of Steel Shear Walls Based on Artificial Neural Network ...
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In this paper, load-carrying capacity in steel shear wall (SSW) was estimated using artificial neural networks (ANNs). The SSW parameters including load-carrying capacity (as ANN’s target), plate thickness, thickness of stiffener, diagonal stiffener distance, horizontal stiffener distance and gravity load (as ANN’s inputs) are used in this paper to train the ANNs. 144 samples data of each of this parameters was calculated using SSW simulation in abaqus. Load-carrying capacity of SSW was estimated using radial basic function (RBF) and multi-layer perceptron (MLP) neural networks. Spread parameter in RBF and number of hidden layer, number of neurons in this layers and activation function in MLP optimized using a trial and error method. The results showed that the load-carrying capacity of SSW could estimate using RBF and ANN by 84 and 96 percent of precision respectively.Sat, 30 Mar 2019 19:30:00 +0100Investigating the Effect of natural Pozzolans on Mechanical Properties of Roller Compacted Concrete
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Roller Compacted Concrete (RCC), is a concrete with zero slump, which is used in damming and road pavement. Roller Compacted Concrete Pavement (RCCP) bear heavy traffic loads and severe weather conditions. This type of concrete is due to its economic and environmental capabilities, including reduced construction and maintenance costs, longer durability and longer lifetime, as well as environmental compatibility. This paper presents the results of laboratory studies on the effect of natural pozzolan (zeolite) on the mechanical properties of RCC specimens. In this study, cement materials of were used The rheological performance test (VeBe) and compressive and tensile strengths at the age of 7, 14 and 28 days and the flexural strength tests at 14 and 28 days were performed on the specimens. The results show that the higher amount of pozzolan reduced concrete efficiency (the time of VeBe increased). In addition, the compressive, tensile and flexural strength of the samples are decreased, significantly. However, reducing resistance does not mean compliance with the requirements of the Code.Thu, 28 Feb 2019 20:30:00 +0100A Discrete Hybrid Teaching-Learning-Based Optimization algorithm for optimization of space trusses
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In this study, to enhance the optimization process, especially in the structural engineering field two well-known algorithms are merged together in order to achieve an improved hybrid algorithm. These two algorithms are Teaching-Learning Based Optimization (TLBO) and Harmony Search (HS) which have been used by most researchers in varied fields of science. The hybridized algorithm is called A Discrete Hybrid Teaching-Learning Based Optimization (DHTLBO) that is applied to optimization of truss structures with discrete variables. This new method is consisted of two parts: in the first part the TLBO algorithm applied as conventional TLBO for local optimization, in the second stage the HS algorithm is applied to global optimization and exploring all the unknown places in the search space. The new hybrid algorithm is employed to minimize the total weight of structures. Therefore, the objective function consists of member’s weight, which is depends on the form of stress and deflection limits. To demonstrate the efficiency and robustness of this new algorithm several truss structures which are optimized by most researchers are presented and then their results are compared to other meta-heuristic algorithm and TLBO and HS standard algorithms.Thu, 28 Feb 2019 20:30:00 +0100Evaluation and Comparison of LEED, BREEAM, and the 19th issue of National Building Regulations ...
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In this research, the features of LEED, BREEAM, and NBRI also, their principles, are reviewed, evaluated, and compared from the aspects of the sustainability. The compliance items of standards with the principles of sustainability determine that their goals are well matched. By comparing the different and shared principles, it discovered how each standard has succeeded from the aspect of the sustainable design also, the shortcomings in the 19th issue of NBRI were appeared. The evaluation of standards with sustainability principles is done by applying (MCDM) TOPSIS. furthermore, by ranking each sub-item of standards from weak to excellent, the respect of sustainability principle is recognized. plus, according to the TOPSIS and analyzing the data, any items of each standard has the most sustainability feature are considered. The alignment with the leading tools can result in the promotion of the Iranian regulations. Findings of this research provide suggestions for completing and localizing the criteria that are part of the LEED and BREEAM in energy section which are neglected in the 19th issue. Applying these solutions and paying more attention to all of building's sustainable aspects in Iran will lead to the success of the country to be adopted with the global counterparts.Sat, 30 Mar 2019 19:30:00 +0100The Effect of Viscous Dampers on Improvement of the Behavior of Tall Belt Truss Structures
http://www.qjseg.ir/article_666902_1133025.html
Using energy absorption systems in the structures with malfunctioning components is of paramount importance. By absorbing the seismic energy, these systems help the components of the structure to remain resilient during earthquake. In the present study, viscous dampers were applied in order to enhance the reactions of tall building with belt truss.
To assess the response of a structure under earthquake loading conditions, we used the dynamic non-linear time-history analysis by the finite element method (FEM) using the ABAQUS software. Considering that the frequency content varies in earthquakes, each exert a different effect on the structure. For the evaluation of this parameter, seven accelerograms were used for the dynamic non-linear analysis. The studied tall buildings had 20, 30 and 40 floors and were selected without a damper and with viscous dampers so as to determine the effect of the number of floors on structural behavioral with and without dampers. X-braces were used in the structure, and the viscous dampers were applied within the horizontal braces. In addition, belt truss was used once in the last floor and again in the last and middle floors.
According to the results, the structure’s response reduced due to the use of dampers or a second belt truss, so that the simultaneous addition of the middle belt truss and damper was associated with the highest reduction in the structure’s response (66.72%). However, this effect does not occur at all times, and the possibility must be considered for the structure before implementation. On the other hand, our findings suggested that the effects of the damper and middle belt truss on the decreased acceleration and maximum base shear would augment with increased height. Therefore, using dampers with middle belt truss is one of the most effectual techniques to reduce the structure response in tall buildings.Fri, 29 Mar 2019 19:30:00 +0100A Case study of Performance Improvement of Femur Prosthesis
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Nowadays, the placement of artificial prostheses in human skeleton, etc. is common due to different reasons such as fractures or deficiencies. Prostheses are structures that assist the performance of organs by reconstruction of some body parts through different methods to enable the organ to re-obtain its performance completely or partially and, since the use of external prostheses might lead to issues such as severe traumas, slow recovery and imposition of enormous hospital costs on the patient, therefore, use of internal prostheses can be an effective method for accelerating the process of improvement for the patient. By using CT-scan photos of a 54-year-old man weighing 60 kg and with a femur length of 36 centimeters, and also using a titanium prosthesis with diameters equaling 9 and 13 mm along with screws with diameters of 4 mm whose placement are with angles of ±4, ±4 and ±36 degrees, the geometry of the model has been provided and the model has been analyzed through the finite element method. Results indicated that in case of using the prosthesis with the diameter of 13 mm and screws of 4 mm with angle of +36, the least stress will be imposed on the bone and prosthesis.Fri, 29 Mar 2019 19:30:00 +0100