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Civil Engineering Infrastructures Journal - Volume:53 Issue: 1, Jun 2020

Civil Engineering Infrastructures Journal
Volume:53 Issue: 1, Jun 2020

  • تاریخ انتشار: 1399/04/21
  • تعداد عناوین: 12
  • Behnam Zehtab, Amir Tarighat * Pages 1-13

    In this paper, the effects of different aluminum to silicon ratios in silicate chains of calcium silicate hydrates (C-S-H) are evaluated on the diffusion coefficient of chloride ions by molecular dynamics method. Tobermorite is a crystalline phase that is used for studying C-S-H properties in nano scale, because of its analogous chemical composition to C-S-H. Aluminum incorporation in C-S-H and the formation of calcium aluminosilicate hydrates (C-A-S-H) is due to both of hydration of tricalcium aluminate (C3A) in portland cement and aluminum oxides in pozzolans. There exist different Al/Si ratios in the tetrahedral chains of C-A-S-H depending on available aluminum oxides in cementitious raw materials. In order to compare the simulation results with previously-published experimental researches on cement pastes, a novel method is introduced here to calculate Al/Si ratio in tetrahedral chains of C-A-S-H using pozzolan replacement ratio in cementitious paste. MK (metakaolin) and FC3R (Fluid Catalytic Cracking Catalyst Residue) are the pozzolans that are used to validate the obtained results in this paper. Results showed that diffusion coefficients of chloride ions in C-A-S-H decrease by Al/Si ratio increasing in the tetrahedral chains as it was observed experimentally in previous researches.

    Keywords: aluminum, C-A-S-H, Chloride Diffusion, C-S-H, Molecular Dynamics, Pozzolan, Tobermorite
  • Mojtaba Aslmand *, Iradj Mahmoudzadeh Kani Pages 15-31
    Wave propagation in unbounded layered media with a new formulation of Axisymmetric Scaled Boundary Finite Element Method (AXI-SBFEM) is derived. Dividing the general three-dimensional unbounded domain into a number of independent two-dimensional ones, the problem could be solved by a significant reduction in required storage and computational time. The equations of the corresponding Axisymmetric Scaled Boundary Finite Element (AXI-SBFE) are derived in detail. For an arbitrary excitation frequency, the dynamic stiffness could be solved by a numerical integration method. The dynamic response of layered unbounded media has been verified with the literature. Numerical examples indicate the applicability and high accuracy of the new method.
    Keywords: Axisymmetric Scaled Boundary Finite Element Method, Fourier Series, Layered System
  • Milad Tajdini *, Asan Taherkhani Pages 33-51
    Occurrence of top down and bottom up fatigue cracking in asphaltic pavements is common. Conventional pavement analysis methods ignore the existence of cracks in asphaltic layers. However, it seems that the responses of cracked pavement would not be the same as a pavement without crack. This paper describes effects of crack type, position and length, and vehicles tire inflation pressure and axle load on the performance of cracked asphalt pavement. Tensile strain at the bottom of asphaltic layer, the vertical strain on subgrade, maximum deflection on the surface, rut depth and the stress intensity factors of cracked pavement, with top down and bottom up crack have been computed using 3D Finite Elements method in ABAQUS. Moving load of standard single axle with different loads and tire pressures have been used in the analysis. Standard 8.2 ton single axle load at different tire pressures of 552(80), 690(100), 828(120) and 1035(150) kPa(psi) and single axle at different loads of 5, 8.2 and 15 ton, all at the same tire pressure of 690 kPa, have been used. Results show that the pavement responses increase with increasing tire pressure and axle load with higher values and rate of increase with increasing tire pressure and axle load for the cracked pavement compared with the pavement without crack. For the pavement structure investigated in this study, it was found that, in general, top down crack results in higher responses than bottom up crack.
    Keywords: Axle Load, Cracked Asphalt Pavement, Fatigue Cracking, Rutting, Tire Pressure
  • Mohamadreza Shokri, Hamidreza Tavakoli *, Ali Rahmani Pages 53-69
    In this paper, the formulation of a modified applied element method for linear analysis of structures in the range of small and large deformations is expressed. To calculate deformations in the structure, the minimum total potential energy principle is used. This method estimates the linear behavior of the structure in the range of small and large deformations, with a very good accuracy and low analytical time. The results show that analysis of a console beam by proposed method, even with minimum numbers of elements, in range of small deformations, has a computation error of less than 2%. Meanwhile, solving the same problem by Applied Element Method (AEM), has more than 31% error. Also, the buckling and post-buckling behavior of the structure, within the range of large deformations, is well-suited. So, with minimum number of elements, and very high accuracy, the buckling behavior of the fixed-base column was simulated. Also, the computational time of the proposed method is less than 40 percent of the computational time in the application of the applied elements method with 10 series of connection springs.
    Keywords: Applied Element Method, Linear Analysis, Minimum Total Potential Energy Principle, Small, Large Deformations
  • Seyed Ahmad Mobinipour, Saeid Pourzeynali * Pages 71-88
    Nowadays it is common to use the fragility curves in probabilistic methods to determine the collapse probability resulting from an earthquake. The uncertainties exist in intensity and frequency content of the earthquake records are considered as the most effective parameters in developing the fragility curves. The pulse-type records reported in the near-fault regions might lead to the major damages in the structures having moderate and long periods since response spectra of near-fault ground motions within the long period range are different from those of the far-fault ground motions. In the present study, the influence of this type of earthquake records on the fragility curves of the steel special moment resisting frames, SMRFs, was examined. The results indicated that the median value of the collapse capacity (i.e.ŜCt Parameter, which defines the earthquake intensity leading to the collapse of the structure in half-set of the chosen records) due to near-fault ground motions was 76% that of the far-fault records for the ten-story example SMRF.
    Keywords: Collapse Capacity, Collapse Damage Level, Fragility Curve, Near-Fault Ground Motions, Special Moment Resisting Frame (SMRF), Uncertainty
  • Ebrahim Zamani Beydokhti *, Hashem Khatibi Pages 89-102
    In this paper, the effect of elliptical shape openings was numerically compared to the case when circular openings were used in the steel panel shear walls. At first, the finite element model in ABAQUS was calibrated by experimental results, obtained from previous studies. Then, three steel shear panels with different sizes of elliptical openings were analyzed under cyclic loads, and the results were compared to those circular perforations. Moreover, comparisons of cyclic response parameters such as elastic stiffness, ductility ratio, and energy absorption were made. According to the results, the shape of the openings has a significant effect on the seismic behavior of the perforated shear wall. The elliptical opening with the smaller to larger diameter ratio, equal to 0.5, increased the ultimate capacity by 15%. Furthermore, the elastic stiffness, ductility ratio of the frame, and the absorbed energy were promoted by 28%, 3%, and 8%, respectively. Finally, the distance between the openings was improved. Using a ratio of about 0.17 for the center to center distance of elliptical openings to the total width of steel panel led to the best performance.
    Keywords: Circular Opening, Elliptical Opening, Finite Element Analysis, Perforated Shear Wall, Steel Panel
  • Amir Kavussi *, Behzad Naderi Pages 103-114
    Cohesion properties of the binder matrix within asphalt mixes and adhesion characteristics of the asphalt binder and aggregate particles are the two major mechanisms resisting against cracking in asphalt mixes. This study is focused on estimating crack resistance of asphalt mixes at intermediate temperatures through evaluation of cohesion and adhesion properties of binder-aggregate systems using Surface Free Energy (SFE) method. Semi-Circular Bending test (SCB) was used to support the SFE analysis. SFE measurements were performed applying Sessile Drop test method. A Granite aggregate type and two asphalt binders (PG64-16, PG58-22) containing various amounts of SBS polymer were used to produce six groups of asphalt mixes. Cohesion and adhesion energies obtained from SFE analysis and Flexibility Indexes and Fracture Energies determined in SCB test showed the positive effect of SBS on performance of asphalt mixes at intermediate temperatures, although the effectiveness of SBS modification was more pronounced with SCB parameters. A linear regression was performed and a strong correlation was observed between SFE results and SCB parameters.
    Keywords: Asphalt Mixture, Crack Resistance, Semi-Circular Bending, Sessile Drop, Surface Free Energy
  • AliReza Ghanizadeh *, Nasrin Heidarabadizadeh, MohammadJavad Mahmoodabadi Pages 115-136

    The main purpose of this work is the comparison of several objective functions for optimization of the vertical alignment. To this end, after formulation of optimum vertical alignment problem based on different constraints, the objective function was considered as four forms including: 1) the sum of the absolute value of variance between the vertical alignment and the existing ground; 2) the sum of the absolute value of variance between the vertical alignment and the existing ground based on the diverse weights for cuts and fills; 3) the sum of cut and fill volumes; and 4) the earthwork cost and then the value of objective function was compared for the first three cases with the last one, which was the most accurate ones. In order to optimize the raised problem, Genetic Algorithm (GA) and Group Search Optimization (GSO) were implemented and performance of these two optimization algorithms were also compared. This research proves that the minimization of sum of the absolute value of variance between the vertical alignment and the existing ground, which is commonly used for design of vertical alignment, can’t at all grantee the optimum vertical alignment in terms of earthwork cost.

    Keywords: Earthwork Volumes, Group Search Optimization (GSO), Objective function, Optimization, Optimum Vertical Alignment
  • Alireza Ezoddin *, A. Kheyroddin, Majid Gholhaki Pages 137-159
    This study investigates the effect of different link beam lengths in the Reinforced Concrete (RC) frame retrofitted with the Linked Column Frame (LCF) system. It also investigates the ratio of the link beam length (e) to the span length of the RC frame (L) from 0 to 1.5 for the 9 models of the RC frame retrofitted by the LCF system has been investigated. In addition, it studies the formation of plastic hinges in the RC and Linked Column (LC) frame, distribution of stiffness between the RC and LC frame and the ratio of the structural displacement with the formation of the first plastic hinge in the member of the RC frame at the collapse prevention level (Dp LCF) to the structural displacement with the formation of the first plastic hinge in the link beam (Dy LCF) has been studied. Based on the nonlinear static analysis results, the model with the ratio of e/L= 0.45 has a better performance than other different lengths of the link beam. In this model, the stiffness of the LC frame has increased about 78% in comparison with the model with the ratio of e/L that is more than 0.6. Also, the ratio of Dp LCF to Dy LCF for the model of e/L = 0.45 in comparison with two models of e/L = 0.3 and 0.6 is more about 14% and 22%, respectively. It means that, the model of e/L = 0.45 has more potential to reach the performance level of Rapid Repair (RR) to occupancy.
    Keywords: Link Beam, Linked Column Frame System, Nonlinear Static, Plastic Hinge, Retrofitting
  • Nasser Parishad, Kayvan Aghabayk *, Rose Rezaie, Alireza Samerei, Amin Mohammadi Pages 161-171
    The Driver Behaviour Questionnaire (DBQ) is widely used around the world to investigate driving behaviours. However, it has several different versions extracted from the 50-items Manchester driver behaviour questionnaire for variety of societies. This study aims to calibrate the DBQ for the Iranian driver population and explore their aberrant driver behaviour. In total, 524 participants (325 men and 199 women) between the ages of 18 and 79 years from different cities of Iran with more than one million populations were engaged in this study (Tehran, Mashhad, Esfahan, Qom, Tabriz, Karaj, Ahvaz, Shiraz). Principal Component Analysis (PCA) with varimax rotation extracts four-factor that describes the aberrant driver behaviours: violations, dangerous errors, lapses, and aggressive behaviours. A short version of DBQ with 20 items is also developed on the same four factors using high factor loading of each of the axis categories. This DBQ can serve as an instrument of driver self-assessment and can use with other self-reporting measures. For reliability assessment, the Cronbach’s alpha test (α) is conducted for both long and short version of the questionnaire. Finally, regression analysis predicts the factor scores using demographic and some general questions.
    Keywords: aggressive behavior, Dangerous Error, Driver Behavior Questionnaire (DBQ), Iranian Sample, Lapse, Violation
  • Ali Ghassemi *, Seyed Sahand Shahebrahimi Pages 173-188
    Dynamic Compaction (DC) is a common deep compaction method that is usually used for densification of coarse-grained soils. Although traditional continuum-based models such as the Finite Element Method can be successfully applied for assessment of stress distributions or deformations induced by DC, they are typically not adequate for capturing the grain scale mechanisms of soil behavior under impact. In contrast, numerical models such as Discrete Element Method (DEM) in which the interaction of constituting distinct elements is explicitly simulated are promising for simulation of DC process. In this study, dynamic compaction in a dry rockfill was simulated through a two-dimensional DEM model. Based on the developed model, a series of analyses with various tamper weights and drop heights were conducted to investigate the effects of important factors such as energy and momentum per drop on DC results. Comparison of the obtained results with experimental observations reveal the capability of DEM for simulation of DC. The numerical simulations also confirm the positive effect of using conical-based tampers in DC process.
    Keywords: Discrete element method, Dynamic compaction, Tamper Shape
  • Amin Motallebiyan, Meysam Bayat *, Bahram Nadi Pages 189-205
    The use of wind turbines to generate electricity has increased in recent years. One of the most important parts of a wind turbine is the foundation, which should be designed accurately because it is influenced by difference forces. Soil cannot carry tension stress; thus, when a wind turbine foundation is applied eccentricity forces, a gap appears between the soil and foundation. The gap will have no positive effect on the ultimate bearing capacity of the foundation. This must be considered when designing the dimensions of an onshore wind turbine on a spread foundation using finite element software in order to avoid error during analysis. In the current study, a spread foundation of an onshore wind turbine was simulated using ABAQUS and PLAXIS-3D software. Based on the results, the effects of Soil-Structure Interaction (SSI), eccentricity of forces, soil strength parameters and the foundation buried depth on static response of the foundation are discussed. The results indicate that the influence of soil-structure interaction is depend on magnitude of eccentricity of forces and depth of foundation, so that soil-structure interaction has little impact on settlement of foundation when eccentricity of forces is less than 1/6 of the diameter of the foundation and this has important effect when the eccentricity forces at an amount exceeding 1/6 of the diameter of the foundation. In addition, this effect decreases with increasing the foundation buried depth and independent of the soil strength parameters (φ´ and C).
    Keywords: ABAQUS, Plaxis, Soil-Structure Interaction, Tension Stress, Wind Turbine Foundations