فهرست مطالب

Scientia Iranica - Volume:25 Issue: 6, 2018
  • Volume:25 Issue: 6, 2018
  • Transactions on Civil Engineering (A)
  • تاریخ انتشار: 1397/09/09
  • تعداد عناوین: 14
|
  • J.P. Amezquita, Sanchez *, M. Valtierra, Rodriguez, H. Adeli Pages 2913-2925
    A wireless smart sensor (WSS) has an embedded processor which is employed for signal processing, communication, and integration capabilities. A state-of-the-art review of recent articles on the WSS technologies employed in structural health monitoring (SHM) is presented in this paper. Different types of WSS and communication technologies are reviewed and their advantages and disadvantages are pointed out. WSS networks provide a number of advantages for SHM such as robust data management, higher flexibility, low cost, and high potential for providing data for better understanding of structural response and behavior. Hybrid platforms, fusing different technological platforms, appear to be promising schemes as the strengths of each technology are exploited. Next generation WSS must consume less power, integrate more with new sensors, have improved noise immunity, and be capable of working with a huge quantity of data without losses produced by wireless communication. Power harvesting based on wind, solar, and structural vibration energy needs to be explored further for long-term. Truly smart sensors should have inherent pattern recognition and machine learning capabilities. Authors advance the research ideology of integrating the sensor technology with recent advances in machine learning technologies.
    Keywords: Wireless smart sensor, Structural health monitoring, Sensors, Signal conditioning, Processors, Wireless communication
  • Mohsen Lamea*, Hasan Mirzabozorg Pages 2926-2937
    Alkali-Aggregate Reaction (AAR) is a deteriorative phenomenon for concrete that impresses the performance of structures. This study focuses on the seismic and post-earthquake behavior of an AAR-affected dam. A computer program is developed for simulating the structural behavior of AAR-affected dams including the seismic and post-earthquake durations. A thin high double-curvature arch dam is selected as case study and is modeled in a series of analyses within the assumed 30-year operating period. Each analysis includes an earthquake excitation in a different specified time. In each analysis, the seismic record is applied to the dam at different status of AAR progression considering the proposed ARI index. The results show that AAR affects seismic performance of the dam, i.e. with the AAR progression; the dynamic responses are significantly changed. On the other side, the effect of earthquake occurrence time on the dam post-earthquake behavior is not noticeable. This may be explained by the linear elastic behavior assigned to the body material in the provided FE model.
    Keywords: Alkali-Aggregate Reaction, Concrete arch dams, Finite-element method, seismic behavior, Post-Earthquake performance
  • Fooad Karimi Ghaleh Jough, S.B. Beheshti Aval * Pages 2938-2953
    The present study is focused mainly on development of the fragility curves for the sidesway collapse limit state. One important aspect of deriving fragility curves is how uncertainties are blended and incorporated into the model under seismic conditions. The collapse fragility curve is in uenced by di erent uncertainty sources. In this paper, in order to reduce the dispersion of uncertainties, Adaptive Neuro Fuzzy Inference System (ANFIS) based on the fuzzy C-means algorithm is used to derive structural collapse fragility curve, considering e ects of epistemic and aleatory uncertainties associated with seismic loads and structural modeling. This approach is applied to a Steel Moment-Resisting Frame (SMRF) structural model whose relevant uncertainties have not been yet considered by others in particular by using ANFIS method for collapse damage state. The results show the superiority of ANFIS solution in comparison with excising probabilistic methods, e.g., First- Order Second-Moment Method (FOSM) and Monte Carlo (MC)/Response Surface Method (RSM) to incorporate epistemic uncertainty in terms of reducing computational e ort and increasing calculation accuracy. As a result, it can be concluded that, in comparison with the proposed method rather than Monte Carlo method, the mean and standard deviation are increased by 2.2% and 10%, respectively.
    Keywords: ANFIS C-means algorithm, Collapse Fragility Curve, First order second moment method, Epistemic uncertainty, Aleatory uncertainty, Incremental Dynamic Analysis
  • Sohaib Ahmad* , Kypros Pilakoutas, Muhammad Masood Rafi, Qaiser Uz Zaman Khan, Kyriacos Neocleous Pages 2954-2966
    The use of inferior quality materials, inadequate detailing and poor construction practices are responsible for most of the brittle failure modes of non-engineered reinforced concrete structures. Bond failures in non-engineered reinforced concrete elements due to short anchorages or low concrete cover result in large slip deformations prevent the development of plastic deformations and reduce energy dissipation capacity. Until now, little work has been carried out that can lead to the development of bond-slip relationships for low strength non-engineered reinforced concrete structures. To address this, experiments have been carried out on pullout and splitting specimens under monotonic loading to investigate bond characteristics of typically used steel bars in non-engineered reinforced concrete structures. Various deficient parameters are considered in the experiments in order to develop multi-parameter bond strength relations for low strength concrete ≤15MPa. The key parameters examined in the experiments are low strength concrete, bar development length, concrete cover, re-bar types (deformed and plain) and re-bar diameter. This paper presents the experimental details and results which are further processed to develop bond strength equations for different bar types in low strength concrete. These equations can be used to define the bond-slip relation for conducting seismic vulnerability assessment of non-engineered structures.
    Keywords: Low strength concrete, normal strength concrete, non-engineered reinforced concrete, Reinforced concrete, Bond-slip, deformed bar, cold-formed bar, Plain bar
  • Seyedemad Motaghian, Massood Mofid *, John E. Akin Pages 2967-2979
    In this research, the combination of Fourier sine series and Fourier cosine series is employed to develop an analytical method for free vibration analysis of an Euler-Bernoulli beam of varying cross- section, fully or partially supported by a variable elastic foundation. The foundation stiffness and cross section of the beam are considered as arbitrary functions in the beam length direction. The idea of the proposed method is to superpose Fourier sine and Fourier cosine series to satisfy general elastically end constraints and therefore no auxiliary functions are required to supplement the Fourier series. This method provides a simple, accurate and flexible solution for various beam problems and is also able to be extended to other cases whose governing differential equations are nonlinear. Moreover, this method is applicable for plate problems with different boundary conditions if two-dimensional Fourier sine and cosine series are taken as displacement function.
    Numerical examples are carried out illustrating the accuracy and efficiency of the presented approach.
    Keywords: Fourier series solution, Free vibration, non-uniform beam, variable elastic foundation, general boundary conditions
  • Mohammad Mehdi Hasheminejad* , Nasrin Sohankar, Alborz Hajiannia Pages 2980-2996
    Soil collapsibility is one of the important phenomena in unsaturated soil mechanics. This phenomenon can impose extensive financial damages on civil engineering structures due to soil subsidence. Because of uncertainties in effective parameters and their measurements, no precise mathematical relation has been proposed for collapsibility potential evaluation. Therefore, soft computing techniques such as fuzzy logic could be a suitable choice to account for different factors. Adaptive neural fuzzy inference system (ANFIS) was used in this study. To predict the collapsibility potential, hybrid algorithm and particles swarm optimization (PSO) were employed by ANFIS for system training. Gaussian membership functions were utilized for fuzzifying the data. Also, data classification was performed in a subtractive form in the fuzzy inference system. A total of 327 laboratory data was used in particles swarm algorithm, 266 of which were chosen for training and 66 for testing. The obtained results showed the effects of different parameters and the rate of their changes in collapsibility potential. Moreover, comparison of different approaches of system training was done using correlation coefficient. The superiority of the proposed method and the utilized techniques was shown by comparing the results with the ones obtained by other researches.
    Keywords: Collapse potential, soft computing, Adaptive neural fuzzy inference system, particle swarm optimization, Gaussian membership function
  • Ali Mohammadi, Hossain Poorzahedy* Pages 2997-3020
    Road alignment design is an important determinant of the development cost of road networks. On the one side, it affects road construction and maintenance costs, which constitute a significant part of country-wide infrastructure development, management and operation budget each year. On the other side, it affects road user-related costs of travel time and vehicle use, which comprise a significant portion of the total transportation cost. This study adapts the existing Electromagnetism-like meta-heuristic algorithm to solve a three-dimensional highway alignment problem, which explores and finds a good route between two given points on a terrain. It detects the potentials of the given initial routes, which are enhanced and shaped toward better positions by the help of the local and global search. The final good solution is, then, fine-tuned for a better alignment. Several example problems are designed to show the behavior of the algorithm. The results show that the algorithm satisfactorily maneuvers to by-pass obstacles, and build highway structures where necessary. The set of the example problems in this paper may also serve to found a basis for evaluation of the performance of alternative algorithms
    Keywords: routing, Three-dimensional alignment, meta-heuristic algorithm, Electromagnetism-like algorithm, earthwork-bridge-tunnel costs, User, operator costs, Reference examples
  • M. Anoushehei, F. Daneshjoo* , S. Mahboubi, M.H. Hashemi Pages 3021-3029
    . Passive energy dissipation devices have been widely used to reduce the maximum responses of structures under seismic loading. Recently, different types of passive energy devices are developed to improve seismic behavior of structures in new construction and retrofitting existing structures. Friction dampers are displacement dependent passive devices which dissipate energy using friction mechanism. Many different types of friction dampers have been proposed in recent years. This paper aims at investigating the cyclic behavior of a rotational friction damper with different friction pads under cyclic loading. To this end, experimental analysis is performed on a friction damper with four friction materials. The tested damper consists of steel plates, friction pads, preloaded bolts and hard washers. Cyclic loads are applied on damper specimens with four friction pads include: aluminum, galvanized steel, stainless steel, steel (St-37). The experimental results are studied according to FEMA-356 acceptance criteria to select the appropriate friction materials as friction pads for using in the friction damper.
    Keywords: Experimental analysis, Passive energy dissipation, Rotational friction damper, cyclic loading, Hysteresis behavior
  • Sasan Tavakkol *, Amir Reza Zarrati Pages 3030-3041
    This paper studies the effects of velocity gradients and secondary currents on distribution of the shear force between the walls and bed of rectangular open channels. We show that neglecting the effect of secondary currents and assuming zero-shear division lines does not yield acceptable results. We, accordingly, introduce a method to determine the percentage of the total shear force acting on the walls and bed of rectangular open channels, which takes both the velocity gradients and secondary currents into account. Using the channel bisectors, along which there is no secondary flows effect, and orthogonal trajectories to isovels, along which there is no shear stress, we divide the channel cross-section into three major subsections, namely bed area, wall area, and shared area. The geometry of each subsection is derived given the location of the maximum velocity. The share of the bed and wall shear forces from the shared area are calculated afterward. The results for bed and walls shear forces agree with the experimental data with an average relative error less than 5% for regular flows and flows carrying suspended sediment. This method also provides a physics-driven range for the wall and bed shear forces which nicely covers the experimental data.
    Keywords: Open channel flow, velocity distribution, shear force, Secondary Flow, dip phenomenon
  • Taesung Eom, Su , Min Kang* , Seung , Yoon Yu, Jae , Yo Kim, Dong Kwan Kim Pages 3042-3053
    In high-rise buildings, lateral loads, such as wind and seismic loads, are frequently resisted by reinforced concrete (RC) structural walls. Behavior and design of fin walls at the periphery of strong core wall structure in high-rise buildings were not analyzed seriously despite their structural importance. Using elastic design/analysis methodologies for the design of high-rise RC fin walls, it is shown that elicited reinforcement ratios are too high, the economic feasibility and constructability thus becomes worse and the ductile failure mode can not be assured. In the present study, the current design process of these fin walls is investigated by analyzing their structural behavior. According to the investigation of the current design and elicited results, high-rise RC fin walls are coupled by beams although they are located on another line and apart from each other, which is main cause of high reinforcement in high-rise RC fin walls. In the present study, a literature review has been conducted to recommend the alternative design method for high-rise RC fin walls under lateral loads, and inelastic analysis has been performed to verify the design method.
    Keywords: High-rise RC structural walls, Fin walls, Alternative design, Inelastic analysis, Coupling beam, High-rise building design
  • Mehran Jafari*, Vahid Lotfi Pages 3054-3065
    Different approaches are utilized for dynamic analysis of concrete gravity dam-reservoir systems. The rigorous approach for solving this problem employs a two-dimensional semi-infinite fluid element (i.e., hyper-element). Recently, a technique was proposed for dynamic analysis of dam-reservoir systems in the context of pure finite element programming which was referred to as the Wavenumber approach. Of course, certain limitations were imposed on the reservoir base condition in the initial form of this technique to simplify the problem. However, this is presently discussed for the general reservoir base condition, contrary to the previous study which was merely limited to the full reflective reservoir base case. In this technique, the wavenumber condition is imposed on the truncation boundary or the upstream face of the near-field water domain. The method is initially described. Subsequently, the response of an idealized triangular dam-reservoir system is obtained by this approach, and the results are compared against the exact response. Based on this investigation, it is concluded that this approach can be envisaged as a great substitute for the rigorous type of analysis under the general reservoir base condition.
    Keywords: frequency domain analysis, concrete gravity dams, Wavenumber approach, reservoir bottom absorption, truncation boundary
  • Masoud Shakibayifar *, A. Sheikholeslami, F. Corman Pages 3066-3087
    The reliability assessment of the railway services is a complex procedure that is affected by many different factors. A railway system is reliable when the trains arrive at their destination within the allowed delay threshold. The objective of this study is to investigate the effect of the infrastructure doubling and electrification on the reliability of the train schedules. In this study, advanced event-driven stochastic simulation software is developed to determine the reliability of the train movements. The calculation of the average train delay as a benchmark is provided to evaluate performance. We compared average train delay with the acceptable delay to define a new benchmark to determine the reliability of the train movements. We also analyzed the delay cascading effect along the railway line in order to better illustration of a number of correlations between the arrival and departure delays at different stations. The model has been validated through a real-world case study of Iranian railway. Successful validation of the developed simulation system demonstrated that the model provides accurate reliability estimations in both congested and non-congested situations. Furthermore, the experimental results showed that electrification and doubling improve the reliability significantly.
    Keywords: Reliability, electrification, average delay, infrastructure doubling, simulation modeling, railway
  • S. Fallahian *, Abdolreza Joghataie, Mohammad Taghi Kazemi Pages 3088-3100
    Nowadays, structural health monitoring has attracted much attention, due to the construction of important and complex structures and their safety. One branch of structural health monitoring is damage detection, estimating the location and extent of eventual damages in the structural systems. In this study, an efficient method is introduced to determine the location and extent of damage in the frame, beam and truss structures using time domain response and an optimization algorithm. First of all, the structural damage detection problem is formulated as a standard optimization problem. So that, the optimization objective function is defined by using the acceleration of damaged structures and analytical model acceleration. The acceleration is obtained using Newmark method. Damage is simulated by reducing the elasticity modulus of structural members. Then, damage problem converted to an optimization problem are solved by teaching–learning-based optimization (TLBO) algorithm therefore, the exact location and extent of damage in structure can be determined. In order to show the capabilities of the proposed approach for identifying structural damage, four illustrative test examples are considered with considering measurement noise effect. The results clearly show that the proposed method is as a powerful method to detect multiple damage in structures.
    Keywords: structural damage detection, Time domain response, Measurement noise, Teaching–Learning-Based Optimization (TLBO) algorithm, analytical model
  • Ali Firat CABALAR * Pages 3101-3109
    In this paper, triaxial and cyclic direct shear behaviour of different sand mixtures were investigated by considering variations of shape, size and mixture content. In most studies, investigations on stress-strain properties of soils are carried out using clean sands. However, granular soils in the field may contain a considerable amount of grains in different physical characteristics (i.e., shape, size). Therefore, behaviour of the various sand mixtures in triaxial compression and cyclic direct shear testing apparatuses has received attention in this study. Two different sizes (0.25 mm-0.5 mm, and 1.0 mm-2.0 mm) of sands with distinct shapes (rounded and angular) were tested in triaxial and cyclic direct shear apparatuses. The mixtures of coarser and finer geomaterials were tested in various mix ratio values from 5% to 50% by weight. Based on the examinations during shearing of these materials, it was observed that behavior of the sand mixtures are closely related to the grain shape of host materials as well as fines content in both testing apparatuses, whilst size of the sands was not found to be significantly effective on the results.
    Keywords: Triaxial compression, cyclic direct shear, grain shape, grains size, sand mixtures