فهرست مطالب

Rehabilitation in Civil Engineering - Volume:7 Issue: 1, 2019
  • Volume:7 Issue: 1, 2019
  • تاریخ انتشار: 1397/11/12
  • تعداد عناوین: 12
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  • Borhan Mirzaei, Kourosh Nasrollahi, Seyedmohamadmahdi Yousefbeik, Gholamreza Ghodrati Amiri *, Ali Zare Hosseinzadeh Pages 1-20

    This paper suggests a two-step approach for damage prognosis in long trusses in which the first step deals with locating probable damages by wavelet transform (WT) and static deflection derived from modal data with the intention of declining the subsequent inverse problem variables. And in the second step, optimization based model updating method applying Artificial Bee Colony (ABC) algorithm will be employed to quantify the predicted damages within an inverse problem. Interestingly, it is indicated that the two-step method greatly aids in declining the number of variables of the model updating process resulting in more precise results and far less computational effort. Moreover, the method is found considerably effective especially for damage prognosis of large trusses. In this regard, two numerical examples including noisy data are contemplated to assess the efficacy of the method for real practical problems. Furthermore, the validity of the second step results is investigated applying other optimizers namely Invasive Weed Optimization (IWO) and Particle Swarm Optimization (PSO).

    Keywords: Structural Health Monitoring, Damage Detection, Wavelet Transform, Model Updating, Large Trusses
  • Arash Adib *, Valiallah Shiri, Mahmood Shafai Bejestan Pages 21-34
    In this article a physical model is presented. A trapezoidal shape of channel with 1.45 m width, 1 meter depth and banks slope of 1H: 1.5V was applied. Circular piers (6, 8 and 10cm diameter) were examined under three dissimilar flow discharges of 50, 65 and 80 lit/s and three different median bed material sizes equal to 0.94, 1.31 and 2.12 mm. Seven different longitude distance to pier diameter ratios (1, 1.5, 2, 2.5, 3, 4 and 5) were examined. Measurement of scour depth (upstream, around and downstream of pier) was accomplished in 10, 15, 20, 30, 60, 120, 240 and 360 minutes from the beginning of each examination. The results indicated that 30%-40%, up to 65% and more than 90% of local scour occurs at first two, 10, 120 and 200 minutes from the beginning of test respectively. The effect of dissimilar parameter especially the distance between piers on scour depth at group piers in series was evaluated and the results were compared to other researchers. It was found that our results is best fitted with the general form of well known Sheppard et al. (2004)’s equation.
    Keywords: Local Scour, Group Piers, Physical Model, Sheppard et al. (2004)&#039, s Equation, Sediment
  • Mohsen Mousivand, Mohammad Maleki *, Masood Nekooei, Mohammad Reza Mansoori Pages 35-48

    Dimensionless coefficient (l) in convergence confinement method indicates the relaxation of stress in the wall of the tunnel at different excavation movements. This factor is  contemplated a constant number in previous studies and tunnel geometric characteristics (such as depth, cross-section shape, radius, soil material, etc.) are not included in its determination; however, ignoring these effects can cause significant errors in the analysis of tunnels. In this article, the effect of excavation pattern and tunnel cross section shape on stress reduction factor  is investigated. For this purpose, at first, by considering the conventional cross sections of the tunnel (circular, horseshoe, and double arch), applying finite difference numerical simulation software FLAC 2D and FLAC 3D, the type of excavation (full face and multi face) was inspected in estimating the stress reduction factor by considering depth, radius, and dissimilar points around the tunnel. At last, studies were carried out between the 2D and 3D analyses and the experiments conducted at Karaj Subway to verify the results obtained from the above 2D analyses. The results of this study indicate the significant effect of radius, depth, point position around tunnel cross-section and its shape on stress reduction factor. Convergence around tunnel variation was observed about 21 percent in horseshoe tunnel. However, the maximum and minimum convergence value was in circle and double arch respectively in a constant radius and depth. The results illustrate the variety percentage error in tunnel wall about 27, 10 and 7 percent for circle, double arch and horseshoe respectively. Nonetheless, percentage error was decreased by increasing the tunnel radius. Applying variable stress reduction factor in the all-around of tunnel cross section can lead to more realistic simulations of complex behavior of tunnels during the excavation. Moreover, this method can be utilized for the analysis and design of tunnel due to its time saving nature and at the same time sufficient accuracy.

    Keywords: Convergence-Confinement Method, Tunnel Shape, Excavation Pattern, Shallow Tunnel, Soft Ground, FLAC
  • Masoud Zabihi Samani *, Mohammad Ghanooni, Bagha Pages 49-69
    The effect of intelligent semi-active thermal exchange-fuzzy controller in structural rehabilitation by attenuating seismic responses of structural systems is investigated. In the suggested structural controller, MR dampers and their sensors are employed as a semi-active controller. Resultant control forces of MR damper are administrated by providing external voltage supply during the earthquakes and high intensity winds. Moreover, a novel evolutionary algorithm of thermal exchange (TE) is applied to compute the optimal location and the quantity of Magnetorheological (MR) dampers and their sensors with regard to minimizing resultant vibration magnitude. An optimal semi-active Thermal Exchange-Fuzzy Controller (TE-FC) has been suggested to administrate MR damper ingeniously. Results of numerical simulations illustrate the efficiency of suggested control system. The TE-FC can determine the optimal control arrangement and forces during a reasonable number of iterations. In comparison of the performance of various control strategies, the TE-FC demonstrates that economical cost and rehabilitation properties of the building could be optimized simultaneously. The TE-FC managed the optimal control forces online during strong ground motion, to attenuate the excessive responses in several rehabilitated buildings. Consequently, the TE-FC could improve the reliability of rehabilitated structure in comparison with passive and offline controllers. The significant efficiency of optimal arrangement of dampers and sensors over uniformly distribution of damper and sensors is presented as well.
    Keywords: Thermal Exchange (TE), Magnetorheological (MR) Damper, Fuzzy Interface System, Semi-Active Control, Structural Rehabilitation
  • Mehdi Ebadi Jamkhaneh, Mohammad Ali Kafi * Pages 70-82
    Partially Encased Composite (PEC) column is one of the recent achievements in the field of composite columns. This paper presents a combined experimental and theoretical study on the mechanical performances of six octagonal PEC columns subjected to axial compressive and bending moment loading. The major different between them was the concrete reinforcement details. The parameters studied in the experimental and numerical study were the type of reinforcement details and the failure mode. The results were presented as load-deformation and moment-rotation curves. In the analytical phase, the experimental results in the compressive loading were compared with those obtained from CSA S16-14 and EN 1994-1-1 equations. The comparison of the code equations given in CSA S16-14 and EN 1994-1-1 revealed that the equation in CSA S16-14 underestimates the capacity. Also, theoretical relationships were used to estimate the compressive capacity and the behavior of laboratory models in order to find the confinement coefficient of concrete.
    Keywords: Octagonal partially encased composite column, Failure mode, Experimental model, Load bearing capacity, Concrete reinforcement
  • Samaneh Kazemi *, Ali Maasoumy Haghighi, Farhad Daneshjoo, Mohsen Ali Shayanfar Pages 83-100
    With energy resource scarcity and energy crisis in the world, energy efficiency has become a subject of great importance. In warm and humid climates as well as cold and mountainous ones, annual energy consumption is too high to achieve desirable living conditions in built environments, and hence energy efficiency measures and practices in such buildings is of utmost priority. Given the direct relationship of amount energy consumption and occupant comfort level in residential buildings, energy saving and energy efficiency is of increasing importance specifically in the residential sector. In this study, the combination of building information modeling (BIM) and building performance modeling (BPM) is used to identify appropriate dimensions and building materials to reduce energy in the lifecycle of a building. To perform this modeling, we evaluated various software applications used in different studies and after identifying their advantages and disadvantages, finally we chose Autodesk Revit and Autodesk Ecotect. In addition, suitable building materials and optimum sizes are determined corresponding to different weather conditions and climates in Iran. In another part of this study, the breakdown of energy consumption in the commercial and residential areas in Iran is examined. Given the 38% share of space heating in total building energy consumption, the important role of thermal insulation of external walls is emphasized. The effect of insulating in this region is calculated and marked using simulation of energy consumption. Using a suitable insulation system, can save 35% in lifecycle energy consumption.
    Keywords: Energy consumption, Optimization, modeling, insulation, climate
  • Somayyeh Karimiyan *, Mahmood Hosseini Pages 101-109
    The variation of earthquake input energy with characteristics of various structural systems, particularly in hysteretic states, has not been studied to such extent that creates enough con-fidence for proposing energy-based design criteria. In this paper, at first, based on a somehow new insight into the concept of earthquake input energy, two concepts of ‘Received Energy’ (ERec) and ‘Returned Energy’ (ERet) have been discussed. Then, by using various hysteretic mod-els for expressing the behavior of structures, including elasto-plastic, bilinear, Wen, Clough, and Takeda models, and two strength levels for the structure, variations of the ‘Total Input Energy’ (ETot) and also ERec and ERet with respect to the structural specifications have been investigated, by a series of Non-Linear Time History Analyses (NLTHA). Several earthquake accelerograms with various frequency contents from low to high, and peak ground acceleration values have been used for NLTHA. Results show that in some cases the amount of seismic input energy varies remarkably with the hysteretic specifications of the structure, particularly its strength. On this basis, it can be claimed that the hysteretic specifications can be used as measures for limiting the amount of earthquake input energy, and accordingly the level of overall damage to the structure.
    Keywords: Wen, Takeda, Clough models, Non-Linear Time History Analyses
  • Nazanin Shahkarami * Pages 110-123
    An experimental study has been conducted on the effectiveness of two types of flow-altering countermeasures placed around a cylindrical pier under clear water condition, which include sacrificial piles and submerged vanes. Their arrangements follow the optimal configurations recommended in the published articles with some modification. The temporal evolution of maximum scour depth and its equilibrium amount around the pile without and with two scour countermeasures were recorded; scour depth reduction rates and changes in bed topography were then calculated. It can be said that according to the result which has been earned from the experiments of this study, submerged vanes had better performances compare with the sacrificial piles in all of investigated aspects. By using submerged vanes 75% of the scour only occurred in first 5 minute. Presence of submerged vanes played more efficient role in reducing scour depth as subjected scour depth reduction was 17% more than one subjected to sacrificial piles. The length of changes downstream the pier (L) were 12, 13.2 and 6 times of pier diameter (D) corresponding to pier with no protection, sacrificial piles and submerged vanes respectively, which showed the effectiveness of submerged vanes in reducing the area affected by pier scour. Also the maximum changes of bed level were -6.9 cm to 3.9 cm in unprotected pier test, -4.4 to 3.5 cm in protection by sacrificial piles test and -3 to 3.2 cm in protection by submerged vanes.
    Keywords: Countermeasures, Cylindrical Bridge Pier, Experimental Study, Sacrificial Piles, Submerged Vanes
  • Seyed Rohollah Hoseini Vaez *, Seyedeh Somayeh Tabaei Aghdaei Pages 124-140
    In this study, the effect of earthquake frequency content and noise effects on damage detection has been investigated. For this purpose, the damage was defined as nonlinear behavior of beams and columns, and several ground motion records were scaled so that some elements yield under the applied excitation. Then the acceleration response data of each floor obtained using the nonlinear dynamic analysis. Using the discrete wavelet analysis, the occurrence and time of damage in a frame can be detected based on the spikes appearing in the wavelet details plots obtained from discrete wavelet decomposition. The mean period (Tm) was used to determine the frequency content of earthquakes. The implications of this parameter for the analyses with different ground motion records were investigated and the results showed that the records with low Tm are more suitable for structural damage detection. To investigate the effect of noise or measurement errors on damage detection process, the discrete wavelet analysis was repeated with a noise introduced to the acceleration response data.
    Keywords: Damage Detection, Frequency content, Wavelet Transform, Steel frames
  • Vafa Morsali, Farhad Behnamfar * Pages 141-158
    The design of earthquake-resistant buildings starts with defining the maximum lateral earthquake forces or their resultant. The amount of these forces depends on various factors, including coefficient of system behavior which depends on overstrength and its ductility. In this study, a method is presented for designing an earthquake-resistant system in which the distribution of lateral forces is adjusted based on equal distribution of the seismic demand ratio in structural elements for the optimum use of seismic capability of the structure. To this end, three types of 4-, 7-, and 10-story structures are used. First, the above-mentioned structures are designed based on gravity loads and then analyzed based on linear and nonlinear dynamic analyses, using the accelerograms of some major earthquakes. Following that, the average loading ratio to the allowed capacity of the elements of each story in linear analysis and the average ratios of plastic rotations to the allowed capacity of elements in nonlinear analysis are applied as the modified shear ratio in the Iranian National Seismic Code. Therefore, the new lateral loading distribution is measured and identified. Based on this new distribution, the above-mentioned structures are designed and their seismic behaviors are identified, using linear and nonlinear dynamic analyses of the same accelerograms. The findings indicate an improved seismic behavior of the beams and the columns. Moreover, the distribution of the seismic demand ratios attains more uniformity along the height of the structures.
    Keywords: ductility, Seismic design, Lateral force distribution, Demand to capacity ratio, Plastic rotation
  • Ali Kheyroddin *, Majid Gholhaki, Ghasem Pachideh Pages 159-173
    One of the methods for retrofitting reinforced concrete moment frames is the use of steel braces. In this research, the seismic performance of a double-skinned concrete framing system reinforced with two concentric (CBF) and eccentric (EBF) steel bracing, was investigated under seven near-fault earthquake records of varying intensity. For this purpose, two ten-story concrete frames with five spans were designed according to the rules of procedure and were subjected to increasing dynamical analysis (IDA). Locating the braces in the first and fifth spans. The results indicate that reinforcing concrete frame using CBF and EBF braces increases the frame capacity by 2.3 and 2 times, respectively. The use of EBF braces in a concrete frame reduces up to 7 times the amount of base shear applied to the building relative to the CBF frame. Approximately, the displacement of the roof in the EBF frame in the near-fault area is less than the CBF frame. Also, the softer behavior of the EBF frame against earthquake records increases the safety and level of performance of the concrete bending frame at the immediate occupancy (IO).
    Keywords: Reinforced Concrete, CBF, EBF, Seismic Retrofitting, IDA, Near-fault
  • Nader Hataf *, Ali Fatolahzadeh Pages 174-186
    This paper presents the results of a series of small-scale model tests and numerical analyses conducted on circular and ring model footings located near geogrid reinforced sand slopes. Layers of geogrid were used as reinforcement. For numerical analyses Finite Element Method (FEM) was used. The effects of reinforcement depth, size, number of layers, and the horizontal distance between reinforcement and the slope surface were experimentally investigated. Additionally, the effects of other parameters such as slope angle, the distance of the footing from the slope crest (for circular footings) and the ratio of inner to outer diameters (for ring fittings) were also investigated, numerically. The results of numerical analyses were compared with the laboratory test results and found to be in fair agreement. Optimum bearing capacity values were found for some studied parameters. The results indicate that if the reinforcement layers are implemented correctly, the bearing capacity of circular and ring footings over slopes would significantly increase.
    Keywords: Bearing capacity, geogrid, circular footing, ring footing, slope