Amirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Free Vibration of Axially Functionally Graded Tapered Micro-Beams Considering Uncertain Properties543556470410.22060/ajce.2022.18056.5657ENFarhadKamaliCivil Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran.0000-0002-6238-1799FarzadShahabianCivil Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran.Journal Article20200307Experimental observations reveal that the classical continuum theory cannot accurately describe the mechanical behavior of micro/nanoscale structures. In fact, the size-effect will arise when the order of structure dimensions is the same as the material characteristic length. The current work presents free vibration and stability of axially functionally graded (AFG) tapered micro-beams with random properties. The size-dependent behavior of the micro-structure is modeled by the modified couple stress theory. The mathematical formulations are developed based on the Euler-Bernoulli beam model and von Kármán geometric nonlinearity. The minimum total potential energy principle is employed to obtain governing differential equations and the corresponding boundary conditions. The governing equations are solved by the Galerkin method. Due to the complexity of the fabrication process of FGMs, their mechanical and structural properties may vary from sample to sample significantly. Hence, achieving the desired FGMs specification is almost impossible and they are not deterministic, inherently. To incorporate uncertainties in the mathematical model of this study, a First-Order Second-Moment (FOSM) technique is applied to estimate the reliability index of the micro-structure, stochastically. Finally, numerical examples are presented for both deterministic and reliability analysis to show the effects of geometry, length scale parameter, material distribution, and axial load on the natural frequency of vibration and the reliability index of the AFG tapered micro-beam. It can be concluded that by increasing the coefficient of variation (COV) of random variables, the reliability index will decrease. Indeed, by enhancing the length scale parameter, a higher natural frequency of vibration is expected.https://ajce.aut.ac.ir/article_4704_ecb47fbb07a752413640f82a945530f8.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201“Friction-Transfer” Method to Assess the Compressive and Tensile Strengths and Rupture Modulus of Fiber-Reinforced-Pozzolanic Concrete and Mortar/Steel Adhesion557576472210.22060/ajce.2022.18373.5673ENAliSaberi VarzanehFaculty of Technical and Engineering, Imam Khomeini International University, Qazvin, Iran.MahmoudNaderiFaculty of Technical and Engineering, Imam Khomeini International University, Qazvin, Iran.Journal Article20200506Nowadays, non-destructive tests are of great importance for evaluating the quality of concretes. However, such tests typically measure the relevant parameters indirectly, followed by estimating the strength of the concrete using several equations. Accordingly, the present study utilized the friction transfer method to directly evaluate the compressive and tensile strengths and the rupture modulus of glass and polypropylene fiber reinforced pozzolanic concretes at different ages. The in-situ test results were related to the strength of the fiber-reinforced pozzolanic concrete using linear and power regression analyses. Afterward, calibration curves were plotted to translate the friction transfer results into compressive and tensile strengths and the rupture modulus. To realize this objective, eight mixed designs with compressive strengths of 15-50 MPa were employed. In addition, the effects of the fibers on the adhesion of the mortar and steel were evaluated using the friction transfer test. ABAQUS was employed to model non-reinforced and fiber reinforced concrete specimens and the effects of fibers on the results. The results indicated high correlation coefficients between the experimental tests and friction transfer test results. The addition of fibers led to the improved compressive behavior of the concrete, reduced mortar shrinkage, and increased concrete-steel adhesion.https://ajce.aut.ac.ir/article_4722_f1b035b71ef5f8e1e7c1d6c0c5032faa.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Numerical Study of the Settlement of Rafts on Soft Soils Improved by Small Groups of Stone Columns577596475810.22060/ajce.2021.18701.5694ENDanialGhafarianDepartment of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran.S M RezaImamDepartment of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran. Iran0000-0002-5228-1444Journal Article20200710Stone column installation is used as an economical, simple, and efficient technique for soft ground improvement to reduce settlements, increase bearing capacity and accelerate the drainage of the foundation soil. While design approaches and analytical methods usually consider the condition of a very large loaded area by using unit-cell models, many practical stone column improvement projects deal with finite or semi-infinite loading areas (e.g. storage tank foundations and road embankments, respectively). In recent years, researchers drew attention to studying the behavior of small groups of stone columns. There are some recommendations in the literature for the prediction of settlements of small groups of stone columns (<em>S<sub>group</sub></em>) based on results of unit-cell models (<em>S<sub>uc</sub></em>). However, these methods are developed for a specific soft soil or loading condition. This paper presents a relationship for the estimation of the ratio of settlement of a finite-sized stone column supported foundation (SCSF) to the settlement of an infinite group as obtained from a unit-cell model (<em>S<sub>group</sub>/S<sub>uc</sub></em>). The sub-soil and loading conditions are easily taken into account in the proposed relationship. For this purpose, the settlement of a large number of SCSFs having various geometrical and mechanical conditions is investigated using numerical FEM modeling.https://ajce.aut.ac.ir/article_4758_0bfce127947574733b19da0f30739fcd.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Delay Sensitivity of Smith Predictor for Real-Time Hybrid Simulation597612472310.22060/ajce.2022.19265.5723ENMostafaNasiriMechanical Engineering Group, Golpayegan College of Engineering, Isfahan University of Technology, Isfahan, Iran.Journal Article20201116In a real-time hybrid simulation (RTHS), a multi-story structure is partitioned into numerical and physical substructures, and the vibration behavior of the physical substructure is tested within the real-time simulation. An actuator is employed to apply static and inertial forces to the physical substructure due to forces calculated by the numerical substructure. The actuator dynamic is approximated by a pure time delay, and the time delay in the closed-loop system causes inaccuracy results or even instability. The Smith predictor is adopted to minimize the adverse effect of time delay from the RTHS test results. The delay differential equation (DDE) modeling and Hopf analysis are used to determine the dependence of critical time-delay on mass ratios of the system. The method drives the stability crossing curves in the space of parameters defined by nominal delay, and delay uncertainty. The Smith predictor is a model-based approach for the compensation of time delay in delayed control systems. The Smith delay compensator is sensitive to model uncertainty, particularly for time delay mismatch. The effects of delay-induced uncertainty on the stability of the Smith Predictor control scheme are also analyzed. Sensitivity analysis of Smith predictor to delay mismatch shows a more stable margin for overestimation of delay regarded to underestimation, and the stable region becomes smaller in the area as time-delay increases.https://ajce.aut.ac.ir/article_4723_53420bd6e6798761679772a7dd012674.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Causes of Delays in Iranian Building Construction Projects613624472110.22060/ajce.2022.19293.5725ENMahdiRahmatiGraduate School of Management and Economics, Sharif University of Technology, Tehran, Iran.MahdiRojhaniDepartment of Civil Engineering, Faculty of Engineering, Shahed University; Tehran, Iran.0000-0002-5220-5716Mohammad AminRaoofDepartment of Civil Engineering, Sharif University of Technology, Tehran, Iran.0000-0001-8535-1296Journal Article20201122Building construction consumes a large percentage of the materials and energy of a country and plays a significant role in the sustainable development of a region. Therefore, any factor affecting construction can have a significant impact on that country. One issue faced by the construction industry as a whole is delayed completion of projects. Poor management practices, such as time management, are pervasive factors. This study investigated and evaluated the causes for delays in the completion of construction projects in order of significance. As applied research, this study examined the causes of delays in building projects in Iran. Library resources were used to extract a set of causes from the literature and these were used to form the items of a questionnaire. The significance of each item was evaluated based on severity and frequency indices. It was then distributed through social media among a society of engineers active in the field of building construction. A total of 216 responses were gathered and formed the basis of our analysis. The results indicated that late financing by the client, demands for kickbacks, non-standard procedures followed by officials, and unrealistic planning and time scheduling of projects were the main causes of delay. The results of this study are a wake-up call for development planners, policymakers, project managers, engineers, experts, clients, contractors, and consulting engineers. Sustainable development can only be achieved by controlling these determinants of construction delays.https://ajce.aut.ac.ir/article_4721_c47e93742387750baba2e238558fa12d.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Half-Plane Boundary Element Fundamental Solutions and Body Force625642477610.22060/ajce.2022.19447.5732ENBahmanAnsariDepartment of Civil Engineering, University of Zanjan, Zanjan, IranAlirezaFiroozfarDepartment of Civil Engineering, University of Zanjan, Zanjan, IranJournal Article20210103Two-dimensional half-plane fundamental solutions have been developed by different researchers in the fields of electronics, mechanics, and geotechnics. However, for geotechnical purposes, their solutions are not complete. This paper discusses those previous solutions and details the mathematical procedures for obtaining a new and complete set of half-plane boundary element fundamental solutions. Initially, static equilibrium equations were written using Papkovitch functions and a proper Green’s function was presented for a two-dimensional half-plane space. Having applied the second Green’s identity, the stress-free condition for the ground surface has been satisfied in the displacement and traction fundamental solutions. These solutions can be applied in a meaningful way to problems with semi-infinite workspaces like those much seen in geophysics, geotechnical, and mining engineering because they do not need to discretize the distal boundaries of the model. After extracting half-plane fundamental solutions, the effects of the gravity force as body force and required functions for a half-plane boundary element analysis were extracted. The effectiveness and accuracy of the new solutions have been evaluated by implementing them in a boundary element computer code and solving several classic semi-infinite examples. Results showed that the new solutions are capable of accurately and economically modeling semi-infinite problems.https://ajce.aut.ac.ir/article_4776_04c6906524cd877e833fe26ddaddc62f.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Lateral Stiffness and Bending Moment Changes along Piles Having Different Sections in Loose Sand Subjected to Cyclic Lateral Loading643656475510.22060/ajce.2021.19518.5739ENAnvarFaresghoshooniDepartment of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran.S M RezaImamDepartment of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran.0000-0002-5228-1444Journal Article20210117Two-way cyclic lateral loading tests with constant displacement amplitude were performed on model piles in the sand to investigate the effects of cross-section geometry and modulus of elasticity on their behavior. The tested model pile sections included one square and three circular shapes and were made of polyethylene and polyurethane materials. The frequency of the cyclic loading was 0.29 Hz and the total number of loading cycles was 145 for all the tests. The model piles were tested in a metal test tank equipped with various facilities including a cyclic lateral loading system, devices to measure displacement and pressure along with the pile, an inverter to adjust or change loading frequency, a sand raining system, etc. Test results indicated that, from a global point of view, the soil modulus of lateral subgrade reaction and maximum moment developed in the pile increases with the number of loading cycles; however, the rate of increase gradually decreases. These variations may be formulated using a logarithmic relationship which includes a degradation parameter that reflects the rate of the mentioned decrease. It was also concluded that the cyclic effects are more significant for the lateral load resistance and stiffness than for the moment. The maximum moment at the 145<sup>th</sup> cycle for piles with various section geometries and elasticity moduli varied from 1.10 to 1.18 times the value obtained in the first cycle. Depending on the section shape and dimension, cyclic loading can increase the lateral stiffness of the soil at depths shallower than about 6.2 to 9.3 times the pile diameter.https://ajce.aut.ac.ir/article_4755_a7c628dced6a691f1fd31aebc647a0a8.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Numerical Simulation of the Effect of Column Removal on the Plastic Rotation of Beams in Reinforced Concrete Structures657674472610.22060/ajce.2022.19875.5751ENKAHILAMARCivil Engineering Department, University Mouloud MAMMERI, Tizi-Ouzou, Algeria.MEZIANIFAROUDJACivil Engineering Department, University Mouloud MAMMERI, Tizi-Ouzou, Algeria.Journal Article20210417In recent years, the progressive component collapse phenomenon in structures has attracted the attention of agencies around the world, structural systems are subject to progressive collapse when they are exposed to excessive loads that exceed the ultimate capacity of the structural elements. The rapid loss of structural components, such as columns, causes failure mechanisms that can result in the total or partial collapse of the structure. Currently, researchers are adopting different modeling techniques to simulate the effect of structural load-bearing elements loss on the overall behavior of structures during a progressive collapse. The objective of this study is to interpret the effect of the deleted column in the reinforced concrete frame structures on the overall behavior. The modeling procedure was implemented following the finite element method. An experimental model was tested to validate the accuracy of the modeling approach using CAST3M, in which the local modeling approach (fiber model) for the cross-sections and the global modeling approach for the elements (beams and columns) were used. The behavior laws are used to model the behavior of the materials using empirical laws during their deformations. Then, the study focused on the study of the plastic hinges development under vertical loading (imposed displacement) in a reinforced concrete frame composed of three stories and four spans. The results show that the occurrence of plastic hinges (damage level) is located on the near-central column nodes. At the edges, minor damage is noted, remaining practically in the elastic stage.https://ajce.aut.ac.ir/article_4726_f9ff6540c092abd6a77908c034710a04.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Effect of using Calcined Clays, Silica Fume, and Limestone Powder on the Compressive Strength and Chloride Binding Capacity of Cementitious Pastes675684471010.22060/ajce.2022.20347.5767ENFarnazBahman-ZadehDepartment of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran.Ali AkbarRamezanianpourDepartment of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran.ArashZolfagharnasabDepartment of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran.Journal Article20210731Chloride ions ingress is one of the major reasons for the deterioration of reinforced concrete structures, particularly those exposed to marine environments. The use of supplementary cementitious materials (SCM) has been introduced by many researchers as a practical approach to reducing corrosion of embedded steel caused by chloride ions penetration. In addition to the effects of SCM on transfer properties of cement-based materials, their influence on the binders' chloride binding capacity should be studied to evaluate the durability of mixtures against chloride attack. In this investigation, the chloride binding capacity of pastes containing silica fume (SF), limestone powder (LS), and three samples of calcined clays (CC) as SCMs, have been compared with Portland cement (PC) paste. The chloride binding capacity has been measured by the equilibrium method for samples submerged in different concentrations of NaCl solution (0.1, 0.3, 0.5, 1, and 2 molars) for 42 days. Furthermore, compressive strength tests after 7, 28, and 90 days of curing, X-ray diffraction (XRD) analysis, and Friedel’s salt (FS) quantification by thermogravimetric analysis have been carried out. Results indicated that by increasing the kaolinite contents of raw clays, the chloride binding capacity and FS amounts of samples submerged in 2 M NaCl solution have been increased up to 242.5 and 169.5%, respectively. While samples with LS and SF had generally lower chloride binding capacity than PC paste. The 10% replacement of PC by SF and LS led to 37.5% and 9.8% lower formation of FS in samples submerged in 2 M NaCl solution. https://ajce.aut.ac.ir/article_4710_a78e17c964d3593d89cde3fb678f6a14.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201A New Correlation to Estimate Bearing Capacity of Micropile Groups685700477810.22060/ajce.2022.20386.5772ENAliGhanbariFaculty of Engineering, Kharazmi University, Tehran, Iran.0000-0002-8264-0540MahdiYoosefi TaleghaniFaculty of Engineering, Kharazmi University, Tehran, Iran.Journal Article20210827Most of the recent studies that have focused on the micropile group have been limited to a specific soil type. However, the bearing capacity of micropile groups has not been considered in any of these studies. This study concerned three-dimensional numerical modeling of loose sand, medium sand, silty clay, and soft clay improved by the micropile group. The bearing capacity of the micropile group was estimated by 3D numerical modeling. The micropile group was modeled using spacing to diameter ratio (<em>S</em>/<em>D</em>) and the ratio of micropile length to cap width of micropile (<em>L</em>/<em>B</em>) in soil. Despite the use of only the shear failure criterion in the FHWA Code, the allowable settlement criterion was also considered in this study. A novel approach was presented to estimate the bearing capacity of the micropile group in which a new concept known as “unit length bearing capacity” has been used for the first time. The results demonstrated that in all four soils studied, the unit length bearing capacity of the group will decrease with increasing micropile length. In addition, the settlement of the micropile group in all four soils will decrease with increasing micropile length. The unit length bearing capacity of the micropile group and the overall bearing capacity of the micropile group in all four soils will decrease with an increasing spacing of micropiles. Of course, with increasing micropile length, the unit length bearing capacity will decrease at a slower rate than the overall bearing capacity. According to the simulation results, a punching failure occurred in the micropile group. https://ajce.aut.ac.ir/article_4778_085ccaddbd3aa270b1d72beef6bbc5ca.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Lost Vibration Test Data Recovery Using Convolutional Neural Network: A Case Study701714477710.22060/ajce.2022.20641.5773ENPouyaMoeinifardSchool of Civil Engineering, College of Engineering, University of Tehran, Tehran, IranMohammad SadraRajabiSchool of Civil Engineering, College of Engineering, University of Tehran, Tehran, IranMaryamBitarafSchool of Civil Engineering, College of Engineering, University of Tehran, Tehran, Iran0000-0002-7945-9388Journal Article20211008Data loss in Structural Health Monitoring (SHM) networks has recently become one of the main challenges for engineers. Therefore, a data recovery method for SHM, generally an expensive procedure, is essential. Lately, some techniques offered to recover this valuable raw data using Neural Network (NN) algorithms. Among them, the convolutional neural network (CNN) based on convolution, a mathematical operation, can be applied to non-image datasets such as signals to extract important features without human supervision. However, the effect of different parameters has not been studied and optimized for SHM applications. Therefore, this paper aims to propose different architectures and investigate the effects of different hyperparameters for one of the newest proposed methods, which is based on a CNN algorithm for the Alamosa Canyon Bridge as a real structure. For this purpose, three different CNN models were considered to predict one and two malfunctioned sensors by finding the correlation between other sensors, respectively. Then the CNN algorithm was trained by experimental data, and the results showed that the method had a reliable performance in predicting Alamosa Canyon Bridge's missed data. The accuracy of the model was increased by adding a convolutional layer. Also, a standard neural network with two hidden layers was trained with the same inputs and outputs as the CNN models. Based on the results, the CNN model had higher accuracy, lower computational cost, and was faster than the standard neural network.https://ajce.aut.ac.ir/article_4777_c36b1132ac829ece87dda55d77ac06a4.pdfAmirkabir University of TechnologyAUT Journal of Civil Engineering2588-28995420211201Traffic Level of Service Prediction by Support Vector Machine, Deep Neural Network and Long Short-Term Memory Models715726478510.22060/ajce.2022.21090.5791ENArashRasaizadiSchool of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran.0000-0003-1653-9265SeyedehsanSeyedabrishamiSchool of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran.MohammadSaniee AbadehSchool of Electrical & Computer Engineering, Tarbiat Modares University, Tehran, Iran.Journal Article20220209Short-term prediction of traffic parameters and informing them to travelers and transportation operators is a useful tool for advanced traveler information systems. Also, as an advanced traffic management system, it helps to make or maintains the balance between travel demand and supply for the near future. This paper predicts the hourly traffic level of service, which has easily understandable information for all users. Data used in this study is related to 5 sections of a critical suburban road in the north of Iran. This data was collected for five years, and due to its high volume, it is considered big data. Long short term memory and deep neural network as two deep learning algorithms and support vector machine as a well-known classifier are trained by the first four years records. Results show that in average long short term memory predictions are more accurate for all sections, which compared to the second precise model, long short term memory predictions are higher between 1 and 14%. Using long short term memory for predicting level of services A and C, support vector machine for predicting level of services B and D and deep neural network for predicting E and F, bring the highest accuracy for each level of service.https://ajce.aut.ac.ir/article_4785_1d0787d664c95f8c2adb1da311af3c78.pdf