Journal of Seismology and Earthquake Engineering
Volume:17 Issue: 1, Spring 2015

Persian Gulf's largest island, Qeshm is located in north-west of the Strait of Hormuz. Earthquakes of 27 November, 2005 (Mb=6) and 10 September, 2008 (Mb=6.2), causing 10 and 7 casualties respectively, destroying many villages and triggering numerous slope instabilities, revealed the need for a comprehensive study on development of safe construction more than ever. One of these studies could be on landslides, using its results could be considered for reducing damages and injuries during upcoming earthquakes. To achieve this goal, landslide hazard zonation of Qeshm has been studied. In this regard, the type of slope instability and its factors were identified, using the aerial photographs, satellite images and field surveys; showing that the most abundant type of landslide in the region is rock fall. In the next step, maps of landslide factors were prepared, and then by using and modifying Anbalagan methodology, landslide hazard zonation map was prepared. In addition to the above-mentioned method the fuzzy logic theory is also applied in order to achieve more accurate results and to investigate the effects of weighting method on the conducted zonation. Assessing and comparing the results of the zonations are carried out calculating the Quality Sum (QS) for each method. Comparing the results shows almost equal values. Concerning the equal situation and according to the obtained results (QS), it can be said that the appropriate selection of affecting factors on slope instability is more important than the simplicity or complexity of weighting methods.

Since shear wave velocity is determined by non-destructive experiments in the narrow range of small strain, some researchers have reservations about employing it in the assessment of medium-to-large phenomenon, i.e. liquefaction. However, some others confirm that the shear wave velocity is more likely to suit for distinguishing the liquefaction and non-liquefaction susceptibility of sand deposits by means of the chart correlating liquefaction resistance to shear wave velocity, similar to the other types of indices, i.e. SPT and CPT, despite of its few limitations. Such liquefaction charts have commonly been proposed based on the liquefaction resistance of young Holocene deposits, without taking "age" into account. In an attempt to bridge the gap between those ideas, relations between liquefaction resistance and shear wave velocity of sand deposits are proposed under aging effect using a newly introduced index property, i.e. "cyclic reference strain" or "cyclic yield strain", to differentiate between new and old sand deposits. The smaller the cyclic yield strain, the less ductile response of soil and vice versa. It may be concluded, therefore, that this parameter can be employed as a criterion for taking into account the cementation or the effect of age in sandy soils.

Structures are being built very close to each other in metropolitan areas where the cost of land is very high. Due to the proximity of the structures, they often collide with each other when subjected to earthquakes. To mitigate the amount of damage from pounding, the most simplest and effective way is to provide minimum separation distance. Generally most of the existing buildings in seismically moderate regions are built without codal provisions. The main objective of the present study is to check the adequacy of provisions given in codes of various countries. For this purpose, four pairs of structures were selected. The gap between structures was estimated according to codes of different countries and the same were subjected to earthquake excitation. Some codal provisions failed to satisfy the safety requirements, whereas some were safe. Based on this study, recommendations were drawn.

In transient analysis against digitized excitations, and specially, practical seismic analyses, the steps, by which, the strong ground motions are digitized, might be smaller than those recommended for the accuracy of integration. In these cases, in order to consider the total excitation information, the integration steps are to be set as small as the excitation steps. The result is extra computational cost. In the last decade, techniques are proposed, to provide the capability of time integration with larger steps, without disregarding the excitations information. Though the resulting responses are sufficiently accurate, a fundamental question persists. It is on the loss of accuracy, when we simply omit the inter-integration-step excitations. This paper is dedicated to this concern, in the area of seismic analysis. The study is carried out, through theoretical discussions and numerical examples. As the consequence, omission of inter-integration-step excitations may impair the responses, the inaccuracies can be significant, and even, halts of analyses are expectable, in nonlinear analyses. Implementation of techniques for enlargement of integration steps can lead to more efficient and more reliable analyses.

A supervisory genetic-fuzzy controller is proposed for the motion control of an electric shake table, LARZA, in this paper. The controller comprises of two loops, an inner PI loop and a genetic-fuzzy supervisor. The fuzzy controller is devised, based on the prior experience, such that the tracking error is minimized. Furthermore, for optimizing the fuzzy supervisor controller, a genetic algorithm is utilized. For this purpose, a mathematical model is developed for the shake table. Moreover, the model is validated based on the test data. The parameters of the supervisor controller are then tuned based on the model response variables using the genetic optimization approach. The controller is implemented in the shake table and its performances is studied. The test results reveal the effectiveness of the proposed controller in decreasing displacement, velocity, and acceleration tracking errors for two sample earthquakes.

In this paper, steel plate shear wall strengthened by Carbon Polymer''s Fiber was studied. An equation has been proposed for elastic strength using composite theory and maximum work failure model, and another equation has been obtained for elastic displacement related to polymer''s fiber using virtual work principle. Considering fibers and shear wall web as a layer and super positioning plate and fiber behavior, composite shear wall model was achieved. Optimum fiber orientation angle for composite shear wall was in diagonal tension field. Finite element values via the presented model were compared and concluded that the offered model can predict composite shear wall in close range. The proposed model can predict the elastic strength and displacement of composite steel plate shear wall that strengthened with CFRP layers. In this model, the over strength due to CFRP layers super positioned to PFI model and the overall response of composite shear wall can be achieved.