Search for: seismology
0.008 seconds
Total 161 records

    Influence of earthquake record truncation on fragility curves of RC frames with different damage indices

    , Article Journal of Building Engineering ; Volume 7 , 2016 , Pages 23-30 ; 23527102 (ISSN) Khaloo, A ; Nozhati, S ; Masoomi, H ; Faghihmaleki, H ; Sharif University of Technology
    Elsevier Ltd 
    Probabilistic seismic analysis of structures with incremental dynamic analysis (IDA) is a widely used method to offer comprehensive evaluation of the seismic performance of structures. Although IDA is a powerful computer-intensive method, it is really a time-consuming procedure. Accordingly, in this study, for coping with this problem, significant motion duration is used instead of total motion duration. This truncation can significantly reduce the computational effort and time. In order to determine the influence of truncation, fragility curves and their mean annual frequencies (MAF) in each limit state are used with two different damage indices, namely modified Park & Ang and maximum... 

    Seat width requirement for skewed bridges under seismic loads

    , Article Scientia Iranica ; Vol. 21, issue. 5 , 2014 , pp. 1471-1479 ; ISSN: 10263098 Maleki, S ; Bagheri, S ; Sharif University of Technology
    In this paper, the dynamic characteristics of skewed bridges are explored analytically. Closed form solutions for translational and torsional periods of free vibration and mode shapes are given for slab-girder skewed bridges. Moreover, the seismic displacement of the deck of skewed bridges is calculated using the response spectrum method and its skew term is compared with the requirement of AASHTO. The effects of seismic force resisting elements, such as elastomeric bearings and end diaphragms are included. It is shown that the skew term in AASHTO's equation can underestimate the seat width requirement for some bridges. A new skew term for the bridge seat width requirement is suggested  

    Topology optimization for the seismic design of truss-like structures

    , Article Computers and Structures ; Volume 89, Issue 7-8 , April , 2011 , Pages 702-711 ; 00457949 (ISSN) Hajirasouliha, I ; Pilakoutas, K ; Moghaddam, H ; Sharif University of Technology
    A practical optimization method is applied to design nonlinear truss-like structures subjected to seismic excitation. To achieve minimum weight design, inefficient material is gradually shifted from strong parts to weak parts of a structure until a state of uniform deformation prevails. By considering different truss structures, effects of seismic excitation, target ductility and buckling of the compression members on optimum topology are investigated. It is shown that the proposed method could lead to 60% less structural weight compared to optimization methods based on elastic behavior and equivalent static loads, and is efficient at controlling performance parameters under a design... 

    Seismic rehabilitation of exterior RC beam-column joints using steel plates, angles, and posttensioning rods

    , Article Journal of Performance of Constructed Facilities ; Volume 30, Issue 1 , 2016 ; 08873828 (ISSN) Arzeytoon, A ; Hosseini, A ; Goudarzi, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE) 
    The presented studies have been conducted on the scope and magnitude of damages inflicted by earthquakes over the years. Many RC buildings, designed and constructed in the 1960s and 1970s, have serious structural deficiencies, especially in their beam-column joints. Such deficiencies result from inadequate joint shear strength or confinement of column reinforcement. The joints require elaborate retrofit measures to ensure the performances comparable to those of new designed structures. In this research, a new seismic retrofitting method is presented for beam-column joints based on the two-dimensional enlargement of the joint by using steel plate, angles, and posttensioning rods. The seismic... 

    Comparing calculation methods of storey stiffness to control provision of soft storey in seismic codes

    , Article Earthquake and Structures ; Volume 11, Issue 1 , 2016 , Pages 1-23 ; 20927614 (ISSN) Tabeshpour, M. R ; Noorifard, A ; Sharif University of Technology
    Techno Press  2016
    Numerous buildings have been damaged or destroyed in previous earthquakes by developing soft storey. Almost all the seismic codes have provisions to prevent soft storey in structures, most of them have recommended the ratio of stiffness between adjacent storeys, but none of them has proposed the method to calculate the storey stiffness. On the other hand a great number of previous researches on stiffness have been focused on approximate methods and accurate methods by using analytical softwares have been almost neglected. In this study, six accurate methods for calculating the storey stiffness have been studied on 246 two-bay reinforced concrete frames. It is shown with the results of the... 

    Seismic performance evaluation and design of steel structures equipped with dual-pipe dampers

    , Article Journal of Constructional Steel Research ; Volume 122 , 2016 , Pages 25-39 ; 0143974X (ISSN) Mahjoubi, S ; Maleki, S ; Sharif University of Technology
    Elsevier Ltd 
    Dual-pipe damper (DPD) is a metallic yielding device for passive control of structures, introduced recently by the authors. The objective of the current study is to provide guidelines for implementing DPDs in actual steel buildings, evaluate and compare their performance against other metallic dampers. In this study, a representative load-displacement model for DPDs is proposed for the first time, and assessed based on previous experimental cyclic tests. Guidelines for the design of DPD devices are also presented. Three steel moment resisting frames of 5, 10 and 20 stories are designed and then equipped with DPDs of various properties. The responses of the frames to seven earthquake... 

    Pipe dampers as passive devices for seismic control of isolated bridges

    , Article Structural Control and Health Monitoring ; Volume 24, Issue 2 , 2017 ; 15452255 (ISSN) Mahjoubi, S ; Maleki, S ; Sharif University of Technology
    John Wiley and Sons Ltd  2017
    During an earthquake, pounding of bridge superstructure into abutments is potentially destructive to structural elements and may cause unseating failure and collapse. By using energy dissipative devices such as passive dampers, the harmful pounding force may be prevented. One of the most economical passive dampers for structural applications is the pipe damper, recently introduced by the authors. In this paper, computer models of a two-span 60-m long conventional overpass bridge are equipped with different lengths of two types of pipe dampers, namely the dual-pipe (DPD) and infilled-pipe (IPD) dampers. A simplified lumped-mass model for the bridge considering soil stiffness is proposed and... 

    Dynamic-based pushover analysis for one-way plan-asymmetric buildings

    , Article Engineering Structures ; Volume 163 , 2018 , Pages 332-346 ; 01410296 (ISSN) Rahimzadeh Rofooei, F ; Mirjalili, M. R ; Sharif University of Technology
    Elsevier Ltd  2018
    A simple Dynamic-based Pushover analysis for Plan Asymmetric buildings (DPPA) is proposed with the aim of properly considering the effects of torsional behavior as well as the higher modes in the applied lateral load pattern. According to the proposed method, the peak story drifts obtained from the response spectrum analysis (RSA) can be resolved into their translational and rotational components, and the related equivalent static lateral forces and torsional moments can be calculated. Consequently, for accurate estimation of the maximum drift demands of plan-asymmetric buildings, it is proposed that the drift responses obtained from the RSA for the stiff and flexible edges of the building... 

    Turbulencelike behavior of seismic time series

    , Article Physical Review Letters ; Volume 102, Issue 1 , 2009 ; 00319007 (ISSN) Manshour, P ; Saberi, S ; Sahimi, M ; Peinke, J ; Pacheco, A. F ; Rahimi Tabar, M. R ; Sharif University of Technology
    We report on a stochastic analysis of Earth's vertical velocity time series by using methods originally developed for complex hierarchical systems and, in particular, for turbulent flows. Analysis of the fluctuations of the detrended increments of the series reveals a pronounced transition in their probability density function from Gaussian to non-Gaussian. The transition occurs 5-10 hours prior to a moderate or large earthquake, hence representing a new and reliable precursor for detecting such earthquakes. © 2009 The American Physical Society  

    Development of declustered processed earthquake accelerogram database for the Iranian Plateau: including near-field record categorization

    , Article Journal of Seismology ; Volume 23, Issue 4 , 2019 , Pages 869-888 ; 13834649 (ISSN) Khansefid, A ; Bakhshi, A ; Ansari, A ; Sharif University of Technology
    Springer Netherlands  2019
    In this paper, a comprehensive accelerogram database of the Iranian plateau containing 3585 data with all three components is gathered. The raw data are processed by the wavelet-based denoising method, and results are compared with the contaminated data. All the data are classified into mainshock and aftershock categories using the time and spatial window method. Afterward, the data are categorized into the pulse-like and non-pulse-like events based on the detection of velocity pulse in any of horizontal and/or vertical directions. Eventually, among 3585 data, the ones with an average shear wave velocity of top 30 m of subsurface soil profile are selected and their important ground motion... 

    Non-linear behavior of mass concrete in three-dimensional problems using a smeared crack approach

    , Article Earthquake Engineering and Structural Dynamics ; Volume 34, Issue 3 , 2005 , Pages 247-269 ; 00988847 (ISSN) Mirzabozorg, H ; Ghaemian, M ; Sharif University of Technology
    John Wiley and Sons Ltd  2005
    A smeared crack approach has been proposed to model the static and dynamic behavior of mass concrete in three-dimensional space. The proposed model simulates the tensile fracture on the mass concrete and contains pre-softening behavior, softening initiation, fracture energy conservation and strain rate effects under dynamic loads. The validity of the proposed model has been checked using the available experimental results under static and dynamic loads. The direct and indirect displacement control algorithms have been employed under incremental increasing static loads. It was found that the proposed model gives excellent results and crack profiles when compared with the available data under... 

    Performance-based seismic assessment of steel frames using endurance time analysis

    , Article Engineering Structures ; Vol. 69 , 2014 , Pages 216-234 ; ISSN: 01410296 Hariri Ardebili, M. A ; Sattar, S ; Estekanchi, H. E ; Sharif University of Technology
    The current performance-based seismic assessment procedure can be computationally intensive as it requires a large number of time history analyses (THA) each requiring time intensive post-processing of results. This study proposes the endurance time analysis (ETA) method as an alternative method to THA and incremental dynamic analysis (IDA). ETA is a time history based dynamic pushover procedure that applies a set of gradually intensifying acceleration functions to the structure and monitors the performance of the building accordingly. In this paper, the application of ETA in the seismic assessment of multistory steel concentrically braced frames is compared with THA and IDA methods.... 

    Hybrid damping systems in offshore jacket platforms with float-over deck

    , Article Journal of Constructional Steel Research ; Vol. 98, Issue. 1 , 2014 , pp. 178-187 ; ISSN: 0143-974X Jafarabad, A ; Kashani, M ; Parvar, M. R. A ; Golafshani, A. A ; Sharif University of Technology
    Employing dampers to control wave-induced and seismic vibrations of offshore jacket platforms is an attractive method in order to mitigate fatigue and seismic damage. However, adjustable parameters of a damper are designed by considering only one type of environmental loads; either normal-condition load or extreme-condition load. So, it is important to investigate effectiveness of damping system, for both of two main categories of environmental loads. Also it is ideal for the system to have an acceptable performance in both normal and extreme conditions. The idea investigated in the current study is to use a friction damper device (FDD) and a tuned mass damper (TMD) simultaneously in... 

    A parametric study of seismic response in anchored steel tanks with endurance time method

    , Article Scientia Iranica ; Vol. 21, Issue. 5 , 2014 , pp. 1608-1619 ; ISSN: 10263098 Vaezi, D ; Estekanchi, H. E ; Vafai, A ; Sharif University of Technology
    In this paper, the seismic response of anchored cylindrical steel tanks with various dimensional parameters has been investigated by endurance time method considering fluid-structure interaction effects. Various response quantities, such as stresses and displacements, have been evaluated by subjecting tanks to specially designed intensifying accelerograms and their performance is judged based on their response at predefined level(s) of dynamic excitation. It is shown that ET analysis can reliably predict the result of ground motion time history analysis in all seven tank models studied. In four of the tanks in which height of the shell and the level of fluid is the same, the variation of... 

    Risk based seismic assessment of structures

    , Article Advances in Structural Engineering ; Volume 16, Issue 2 , 2013 , Pages 307-314 ; 13694332 (ISSN) Khaloo, A ; Tonekaboni, M ; Sharif University of Technology
    In this paper a new approach to risk based seismic assessment of structures is proposed based on acceptable risk levels. In this approach, the probabilistic seismic vulnerability, predicted lifetime of structure, importance and knowledge factors are considered in the evaluation process. Park & Ang damage index is used to quantify damage states of structure. By performing several incremental dynamic analyses, all damage states of structure from minor to heavy and collapse are considered under all possible ground motions. The structural risk level and the necessity of seismic retrofit measures are specified by seismic risk index of structure. This probabilistic performance based method is... 

    Response modification factors of steel moment frames equipped with completely closed ribbed bracing system (CC-RBS)

    , Article Advances in Structural Engineering ; Volume 15, Issue 7 , 2012 , Pages 1083-1097 ; 13694332 (ISSN) Tabeshpour, M ; Golafshani, A ; Shalmani, A ; Sharif University of Technology
    In this paper completely closed RBS (CC-RBS) is proposed as a function of a new ribbed bracing system (RBS). RBS is an innovative system which has capacity of performing variable stiffness that can be used for controlling structural deformations and frequency shifting to compensate seismic energy. The overstrength, ductility, and response modification factors of steel moment frames equipped with CC-RBS was evaluated by performing pushover analysis of model structures with various stories and compared with those which Iranian seismic code of practice, Standard No. 2800 is supposed for steel moment frame equipped with ordinary brace.The results were compared with those from nonlinear... 

    Optimal damper placement in steel frames by the endurance time method

    , Article Structural Design of Tall and Special Buildings ; Volume 20, Issue 5 , 2011 , Pages 612-630 ; 15417794 (ISSN) Estekanchi, H. E ; Basim, M. C ; Sharif University of Technology
    Performance-based optimal seismic design of structures requires repetitive and massive dynamic analyses. In the Endurance Time (ET) method, structures are subjected to specially designed intensifying acceleration functions and their response at various excitation levels is estimated by each single response-history analysis, thus, significantly reducing the required computational demand. In this paper, the ET method is utilized to acquire optimal placement of viscous dampers in short steel frames with the target of obtaining the desirable performance in two hazard levels simultaneously. In the optimization procedure, the damping coefficients of the added dampers are treated as design... 

    Development of structural shear fuse in moment resisting frames

    , Article Journal of Constructional Steel Research ; Volume 114 , November , 2015 , Pages 349-361 ; 0143974X (ISSN) Nikoukalam, M. T ; Dolatshahi, K. M ; Sharif University of Technology
    Elsevier Ltd  2015
    Abstract Codes require that the span-to-depth ratio of the beams in moment resisting frames (MRF) should be limited to guarantee the development of plastic hinges with a sufficient length at beam ends. This requirement limits the application of MRFs mostly in framed-tube structures. In the current design procedure of steel MRFs, the strength and stiffness design of the structure are coupled often leading to overdesigned structures and foundations. To overcome the abovementioned limits, in this paper a new replaceable shear structural fuse is introduced for MRFs. The fuse is a shear link designed as a sacrificial component by weakening the shear strength of a segment at the middle of the beam... 

    Performance-based seismic retrof itting of steel frames by the endurance time method

    , Article Earthquake Spectra ; Volume 31, Issue 1 , February , 2015 , Pages 383-402 ; 87552930 (ISSN) Mirzaee, A ; Estekanchi, H. E ; Sharif University of Technology
    Earthquake Engineering Research Institute  2015
    The endurance time method (ET) is a dynamic analysis procedure in which intensifying dynamic excitations are used as the loading function. Seismic performance is evaluated over the entire range of equivalent seismic intensities of interest in each response history analysis, considerably reducing computational demand. In this paper, a general methodology for performance-based retrof itting of typical steel frames by the ET method is discussed. A baseline steel momentresisting frame is considered, and its seismic performance is evaluated by the ET method, considering viscous dampers and shear wall panels as strengthening alternatives. Each retrof itting option includes several design... 

    Seismic performance assessment of steel frames equipped with a novel passive damper using a new damper performance index

    , Article Structural Control and Health Monitoring ; Volume 22, Issue 4 , 2015 , Pages 774-797 ; 15452255 (ISSN) Mahjoubi, S ; Maleki, S ; Sharif University of Technology
    John Wiley and Sons Ltd  2015
    Seismic response of steel moment-resisting frames equipped with a novel passive damper called infilled-pipe damper (IPD) is investigated in this study. The IPD is a very economical and easily assembled structural control device with high energy absorption, invented recently by the authors. A simplified trilinear load-displacement model for IPD devices is suggested to be used in this study and further investigations. Next, criteria for IPD elements size selection are proposed for passive control of structures against earthquake loads. Steel frame structures of 5, 10, and 20 stories are designed without any IPD devices. Then, the frames are equipped with IPDs of different stiffness. The frames...