فهرست مطالب

  • Volume:14 Issue: 2, 2013
  • تاریخ انتشار: 1392/02/14
  • تعداد عناوین: 6
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  • Pushan Kumar Dutta, O.P. Mishra, Mrinal Kanti Naskar Pages 81-90
    All large-scale events, like natural disasters and conflict mechanisms follow certain endogenous and exogenous interactions, which are still unclear to geoscientists by normal surface observations. It has been established that complex scale analysis provides a direct insight into the precursory framework for occurrence of endogenous and exogenous events related to large-scale dynamics. The present study is based on the mathematical derivation of a theoretical framework for the process in Earth system dynamics using Poisson process and Markov analysis to identify the endogenous and exogenous stress distribution and their redistributions beneath the sub-surface earth. The transition probability matrix derived for the optimal state sequences of the Markov model, which is relevant in analysis of shock wave of a complex system. This study validates the concept of exogenous events using sand pile cellular automata system, an approach to study complex behavior of multicomponent system. In this paper, Poisson hidden Markov model implemented on a continuous space of sand pile behavior shows that seismogenesis and conflicts occur due to accumulating stress, representing disequilibria in energy and interactions between active agents (faults and heterogeneities) in which the stress may find its release through the onset of a tremor. Earthquake occurrence in the critical state or a critical shock due to the contributor states or conflict in societal analysis is not adequately known. Subsequently, the influence of each contributor tries to come back into stasis (meta-stable state or stable equilibrium state), the spatial system position of earth dynamics or conflicts through a series of tremors (aftershocks) or post earthquake responses.
  • Panjamani Anbazhagan Pages 91-116
    In this study, a shallow region of engineering bedrock in Bangalore, India, was chosen to investigate the application of 30 m based site classification scheme. About 370 bore logs previously drilled up to the bedrock were selected from a geotechnical database. Equivalent N values for 30 m were estimated using measured standard penetration test (SPT) N values, which mean that the study area may be classified as site class C and D. In the study area, a geophysical test and a multi-channel analysis of the surface wave (MASW) were conducted at 58 locations. The shear wave velocities were measured and then used to estimate the equivalent 30 m shear wave velocities (Vs30), upon the results of which the study area was then classified as class B, C, and D sites. The average 30 m SPT N and Vs values were included rock N and Vs values when the depth of the rock is less than 25 m. Therefore, an attempt was made to estimate the equivalent SPT N values and shear wave velocity of the thickness of the overburden soil up to the engineering bedrock and compared with 30 m values. This study shows that, by excluding the N and Vs values of the bedrock, this area can be classified as site class D. There were large spatial site class variations between the site classifications based on the 30 m and engineering bedrock. If the area had clearly defined engineering bedrock within 30 m, then average 30 m SPT N values and the shear wave velocity would mean a higher classification. Site response analysis carried out considering selected SPT N and Vs profiles by giving regional synthetic ground motion at 30 m and engineering bedrock. Response spectrum and amplification values are much higher than 30 m based spectrum and amplifications. Separate site classification scheme needs to be developed for the shallow bedrock region with response spectrum and amplification values.
  • Ali Reza Habibi, Mehdi Izadpanah Pages 117-129
    Determination of seismic performance for a structure is one of the most important topics that researchers have attended to. Most of regulations regarding performance-based design, introduce the drift as a criterion to determine global seismic performance of the structure. Recently, pushover analysis has widely been adopted as the primary tool for nonlinear analysis because of its simplicity and facility compared with dynamic procedures. The main objective of this research is to develop some relations to estimate damage to Reinforced Concrete Moment Resisting Frames (RCMRFs) based on drift criterion resulting from pushover analysis. For this purpose, by employing the Park-Ang damage index, damage analysis is performed on several frames subjected to various earthquake records. By comparing the amounts of damage and drift and evaluating correlation between two sets, some explicit damage functions are derived based on the pushover results. These functions can be applied to estimate the damage to the structures using a simple pushover analysis. The reliability of FEMA-273 acceptance limits on the drift criterion is discussed using the proposed drift based damage functions.
  • Seyed Mehdi Zahrai, Seyed Amin Mousavi Pages 131-143
    Different kinds of passive and active control methods, their advantages and disadvantages, and their feasibility for buildings in Iran are investigated during this study. The main focus of this study is on passive control techniques used in private typical buildings with relatively low seismic performance, which are quite common in Iran. This study also includes a brief outline of different passive dampers and vibration absorbers. According to the technical and economical issues, it is shown that tuned liquid column-gas damper, TLCGD, is one of the best options for enhancing the seismic behavior of typical buildings in the country. A simple yet accurate procedure is proposed to estimate equivalent damping ratio corresponding to the TLCGD. Finally, through a numerical assessment, effect of TLCGD is investigated. Based on the obtained results, TLCGD can reduce rout mean square (RMS) response of buildings, but its capability in reducing the maximum response depends on the excitation itself. TLCGD was shown an efficient scheme for enhancement of seismic capacity of both new and under-operation existing buildings.
  • Farshid Fathi, Omid Bahar Pages 145-158
    Coupled Building Control (CBC) has been effectively used to help mitigate the extended responses of the adjacent tall buildings due to strong ground excitations. Extensive analytical studies and experimental tests have shown this control strategy works well for «dissimilar» coupled buildings, but it''s completely inefficient for the «similar» buildings. Recently, an innovative scheme for structural control, named the Hybrid Coupled Building Control (HCBC), has been presented by the authors, which improves and develops the CBC strategy. HCBC is applicable to all adjacent buildings; in order to apply the HCBC strategy, one of the adjacent buildings will be equipped with a base isolation system, and an active actuator link will connect the two buildings at a floor level. The primary buildings may be similar or dissimilar but, as a desired case, the «similar» buildings will be concerned here. In the previous works, it''s shown that HCBC strategy efficiently decreases the maximum drifts and accelerations of the buildings. This paper investigates the effects of connector location on the performance of HCBC strategy. Analytical results for different configurations are presented in details, and the best choice is introduced.
  • Mohamadreza Shahri, Alireza Azarbakht, Mehdi Mousavi Pages 159-164
    The target spectrum, which has been used most frequently for the seismic analysis of structures, is the Uniform Hazard Spectrum (UHS). The joint occurrence of the spectral values in different periods, in the development of UHS, is a key assumption that remains questionable. Baker et al [3-4] have recently developed the Conditional Mean Spectrum (CMS) as an alternative for UHS. The CMS provides the expected response spectrum, conditioned on the occurrence of the target spectral acceleration value in the period of interest. It is shown that CMS can be accounted as an improvement of UHS. The correlation between the Peak Ground Velocity (PGV) and the spectral acceleration values is investigated in the current study and a newer form of the target spectrum has been proposed. It is shown that the emerged new spectrum, named Eta-based Conditional Mean Spectrum (E-CMS), is more efficient than the conventional CMS in order to modify the UHS. The nuclear industry design guidelines (i.e. Nuclear Regulatory Commission Guide 1.165) provide an alternative procedure for defining the design spectrum, which has been compared with using the proposed E-CMS. The results show that the alternative procedure may not be conservative for stiff structures such as nuclear facilities.