فهرست مطالب

Structural Engineering and Geotechnics - Volume:9 Issue:1, 2019
  • Volume:9 Issue:1, 2019
  • تاریخ انتشار: 1398/01/11
  • تعداد عناوین: 8
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  • An investigation into a Geocell-reinforced Slope in The Unsaturated Numerical Model
    Behnam Behnam Mehdipour, Hamid Hashemalhosseini *, Bahram Nadi, Masoud Mirmohamahsadeghi Pages 0-0
    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.
    Keywords: Unsaturated soil, Barcelona Basic Model, suction, Geocell, FLAC2D
  • Deep Excavation Hazard Assessment Zoning in District 1 in Shiraz Municipality Using Geographic Information System (GIS)
    Sara Afarid, Alireza Hajiani Boushehrian * Pages 0-0
    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.
    Keywords: Geotechnical zoning, Excavation hazard assessment, geographic information system, districts1 in Shiraz municipality
  • Mix Design Selection For Old and New Generation of SuprePlasticizers
    Seiyed Ali Haj Seiyed Taghia *, Navid Afshari Pages 0-0
    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).
    Keywords: Polycarboxylate Ether, Naphthalene Sulphonate, Compressive Strength, Mix design
  • Behavior Study of Cemented Specimen by Biological Technique after Disturbance
    Mohammad Reza Asgari, Mohammad Azadi * Pages 0-0
    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.
    Keywords: Disturbance, Biological cementation, Calcit, Cohesion, Friction angle
  • Determination of Lateral load Capacity of Steel Shear Walls Based on Artificial Neural Network Models
    Ali Delnavaz *, Meisam Bayat Pages 0-0
    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.
    Keywords: Load-carrying capacity of SSW, RBF neural network, MLP neural networks
  • Investigating the Effect of natural Pozzolans on Mechanical Properties of Roller Compacted Concrete
    Mohammad Falahnejad, Mahdi Mahdikhani * Pages 0-0
    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.
    Keywords: Roller Compacted concrete, Zero Slump, Road pavement, mechanical properties, VeBe test
  • A Discrete Hybrid Teaching-Learning-Based Optimization algorithm for optimization of space trusses
    Siamak Talatahari *, Vahid Goodarzimehr Pages 0-0
    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.
    Keywords: Discrete variables, Teaching-learning-based optimization, Harmony search, Size optimization, Truss structures, Structural optimization, Meta-heuristic algorithm
  • Evaluation and Comparison of LEED, BREEAM, and the 19th issue of National Building Regulations of Iran (NBRI) in Perspective of Sustainability by (MCDM) TOPSIS Method
    Mohammad Javad Mahdavinejad *, Mohammad Mehranrad, Nasim Eslamirad Pages 0-0
    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.
    Keywords: Comparative Analogy, Sustainable assessment tools, LEED, BREEAM, 19th issue of the National Building Regulations of Iran (NBRI), (MCDM) TOPSIS method