Journal of Seismology and Earthquake Engineering
Volume:14 Issue: 3, Autumn 2012

In this paper, automatic detection and picking of the S-wave, in the problem of passive seismicmonitoring has been studied, and a method is proposed for detecting S-phase onset time based on the eigenvalue analysis. By calculating eigenvalues of the time domain covariance matrix of the earthquake record, a characteristic function is defined, in which applying an adaptively determined threshold value, the S-phase onset time is picked. The proposed method is capable of successful determining S-phase onset time in local and near regional seismograms. Motivation towards this research has been the growing number of operating seismic stations in Iranian Broadband Network (BIN) and the necessity of providing earthquake parameters information fast and precisely. In addition, a doing well S-phase picking algorithmcan be used to increase the number of determined S-phases in databases in which tomography studies are carried on. We tested the proposed method on 185 earthquakes recorded in the BIN, and evaluated the performance of the algorithm. We also examined the other algorithmof S-phase detection based on Autoregressive (AR) modeling of the seismograms on the same data, and compare the output of two algorithms. This comparison implies that the results of the proposed method are better than the AR based algorithm on our database.

In composite steel plate shear walls system, steel web plates can be strengthened by adding a number of layers of fiber reinforced polymer laminate or concrete on one or both sides of the web plate. In this paper, nonlinear behaviour of strengthened steel plate shear wall by means of glass fiber reinforced polymer laminates have been numerically investigated. In that regard, the tested ½ scaled one-story un-stiffened steel plate shear walls have been selected and simulated using finite element method, based on the available experimental data in the literature. Non-linear large displacement analyses on the finite element model have been carried out and the results presented. The shear capacities and hysteresis curves of the experimental and numerical unstiffened steel plate shear wall are compared. It is found that the simulation outcomes have showed good agreement with the experimental results. After calibration of the numerical model, steel web plate is strengthened by GFRP laminate, and effects of GFRP laminate on the seismic behavior of strengthened steel plate shear walls are investigated. The results indicate that with strengthening infill steel plate on the steel plate shear walls, yield strength, ultimate shear capacity, secant stiffness and cumulative dissipated energy of SPSWs can be significantly increased.

Demand for earthquake insurance is directly or indirectly related to several independent variables. In this study, a sample of 800 owner-occupants of residential units in Tehran was categorized by characteristics of the head of household (age, education, employment, monthly income, attitude toward insurance company, trust in federal disaster relief, geophysical risk) and the structure (type, age, construction quality, value). The effect of these characteristics on the demand for insurance was assessed. The results showed that the level of seismic risk significantly affected the demand for earthquake insurance and that an increase in the premium and value of the structure decreased the demand for earthquake insurance. In addition, the perception of risk significantly increased the demand for residential earthquake insurance. Finally, confidence in federal disaster relief decreased the demand for earthquake insurance. Income level had no significant effect on the demand for insurance.

The walls are permitted to displace to a specific amount in the seismic designing of the retaining walls using the limited displacement methods. As a result, the dynamic pressure of the earthquake on the retaining walls decreases compared to the case in which the wall is not allowed to move. The purpose of this paper is calculating the coefficients of the Richards and Elms equations in seismic designing of retaining walls, so that they can be applied in seismic provisions of Iran. Since this method requires determining the Aa and Av coefficients, the records with the magnitude of higher than 5.5 were selected among the three-component records of the accelerograph network of the country. The baseline correction and filtering of all accelerograms have been conducted using SeismoSignal V.3.2.0 software. From a total of 426 records, a set of 142 records were selected with a distance to the epicenter less than 60 km and peak ground acceleration of more than 0.05 g (50 cm/sec2). Since the results could be used in Iranian code, the macrozonation of Aa and Av has been done throughout the country. Depending on the location of the accelerograph, the related records have been normalized according to the acceleration coefficients of the zone plan. Finally, a zoning map of Aa and Av is proposed. Using this map and determining the permitted displacement, the designers can achieve the horizontal seismic coefficients for designing of retaining walls.

In damage detection of civil, mechanical, aerospace, nuclear, bio-mechanic, and offshore engineering, dynamic characteristics of beam-spring structures (BSS) play an important role. Recently, a new and innovative method for the free vibration of cracked bars is proposed. The method is extended for the free vibration of BSS. By introducing a new and innovative conjugate beam through defining a new variable, a single ordinary differential equation, golden equation, is obtained. The solution for the golden governing equation (GGE) is the same as that for an intact beam and so great simplicity and generality is obtained. Using the GGE, both closed form and numerical solutions are obtained. Through applying the work to specific examples and comparison of the results with the others, the accuracy, efficiency and robustness of the work is verified.

A magnitude 6.3 earthquake struck Christchurch, New Zealand at 12:55 pm on 22nd February 2011 resulting in liquefaction, rockfall and shaking induced building damage. The peak horizontal ground acceleration of 1.68 g was much higher than the design level of 0.22 g and it is much greater than that recorded in most other earthquakes around the world. The severity of shaking was due to the fault proximity to Christchurch, the fault rupture mode and local site effects/conditions. The death toll was 185 mainly due to building collapse. Backgrounds to a number of post-earthquake decisions are described. These relate to: the level of shaking to be considered in future Christchurch building designs; earthquakeprone buildings; University of Canterbury reactions; governmental response; engineering community activities; insurance company issues; and decisions by citizens affected by earthquake damage. Major lessons learnt relate to the effects of severe earthquake shaking, ground deformation and aftershocks on loss and recovery, the need to develop better assessment and repair methodologies, and the need to develop buildings which will sustain much less damage in future earthquake events.