Abstract

Estimating the time, location and the size of an earthquake event using neural networks is an emerging technology. Present study aims to predict the near future earthquake events in each of the regions partitioned as clusters of epi-central locations of earthquakes related to Indian subcontinent. K-means clustering algorithm is applied to develop a catalogue of earthquake epicenters. Two approaches are considered for the purpose of forecasting. In the first approach regions obtained as clusters are considered as the area sources. The distribution of time series of (temporal distribution) events are divided into five time periods viz., 15 days, 30 days, 60 days, 90 days and 180 days. The accuracy of forecasting a magnitude for the next time period is studied using application of Recurrent Neural Network In the second approach the seismic data of each cluster is further grouped into three categories of magnitude viz., minor (≤ 4 Mw), moderate (between 4 Mw and 6 Mw) and strong (> 6 Mw). Accuracy of forecasting for each of the group belonging to the clusters is computed considering the same five time periods. The epicentral locations represented as latitude and longitude is the inputs for recurrent neural network. The results show that accuracy of second approach is significantly more than first approach. Finally, an attempt has been made to compare the accuracy level of Recurrent Neural Network method with the accuracy level of Gutenberg Richter law in predicting the earthquakes for future 60 days. It has been observed that Gutenberg-Richter law poorly forecasts near future earthquake.

Abstract

Construction of buildings without keeping enough setback from plot boundary is very common practise in India. This lead to very closely spaced buildings with practically zero or few mm gap between them. The intension behind this is to utilize the maximum plot area, without knowing the consequences of damage due to pounding during moderateto-severe earthquake shaking. In this study, an attempt is made to check the adequacy of separation distance clause of IS 1893: 2016 and also a comparison is made with similar clauses in international codes of practise. For this purpose, four low to mid-rise RC buildings located in seismic zone IV were designed as per IS 456: 2000 and IS 1893: 2016. These buildings are assumed to be closely spaced with each other, in pair of two, for four different cases. Further, the linear and non-linear time history analysis (NLTHA) were carried out by considering ground motion time histories of three moderate earthquakes recorded in India. From the study, it was found that the separation distance clauses prescribed in IS 1893-2016 are on conservative side.

Abstract

In this study, a three-dimensional, four-storied, reinforced concrete (RC) building is designed for seismic zone-IV and seismically evaluated for different infill configurations along with consideration of openings in infills to develop a realistic model. Four models are considered, ie model I (full RC-infilled frame without lintel beam), model II (bare frame without lintel beam), model III (full RC-infilled frame with lintel beam) and model IV (bare frame with lintel beam). In this study, we have evaluated the effect of lintel beams on response reduction factor of the frame structure. The nonlinear static adaptive pushover analysis has been done using Seismostruct program. In seismic design, the response reduction factor (R-factor) reduces from the elastic to inelastic strength. The R-factor is one of the design tools to show the level of inelasticity in a structure and so it has significant importance in the earthquake engineering field. The response reduction factor mainly consists of ‘ductility reduction factor’and ‘over strength factor’, which are evaluated from static adaptive pushover analysis. Ultimately the response reduction factor is obtained for the building and compared with the value recommended by IS 1893 Part-1 (2016). The results depict that the

Abstract

No Results Found

Abstract

An earthquake Mw7.8 occurred on 25 April 2015 in a seismically dominant area of Nepal. No major earthquakes (>Mw7.0) were recorded in the past two decades, though Nepal is one of the active seismic regions in the world. The combined effect of the main event and the aftershocks, which are temporally distributed over 40 days, has led to a huge devastation, killing thousands of people in the epi-central area. A complete seismic catalog and influencing parameters such as type of fault, epi-central/hypo-central distance, type of soil are required for a region to assess seismic hazard scenario. The seismic hazard can be represented in terms of Peak Ground Acceleration (PGA), which is the most widely used parameter in strong motion studies. The main objective of this paper is to understand the characteristics of ground motion of the 2015 Nepal earthquake. Since the available ground motion records are limited, an attempt has been made to generate ground motion records using a modified semi-empirical approach. Contour maps of PGA and intensity have also been generated. It is observed that around 22% of buildings experienced an intensity of VI on MMI scale at Bageswari mandal. A few buildings have experienced an intensity of VII in Thankot, Seuchatar, Satikhel, Mahadevathan, Indrayani, Chhaimale, and Balambu.

Abstract

Damage index models are used for quantification of damage in any numerical model of a building. While using any particular damage model there is high possibility that it might give similar result for two identical structures, each having different attributes. So, though currently available damage index models precisely quantify damage in the structure but fails to identify the reason or attributes/irregularities present in it. Therefore, for quantitative assessment, a unique aspect should be used which will depend on structural as well as architectural features. This paper presents new method for quantification of damage for reinforced concrete (RC) moment resisting framed (MRF) structures using the pattern of hinge formation in structure when it is subjected to a monotonic loading. A two-dimensional RC MRF structures with different building irregularities were modeled. As a primary step to estimate the damage from the pattern of hinge formation, it is necessary to understand and study the relation between damage and hinge pattern. For this purpose, energy-based damage index model is used. The relation between damage index and pattern of hinge formation is studied with the help of regression analysis. A multiple regression analysis is performed taking damage index as dependent variable and the number of hinges formed in each damage state as independent variables. The paper also discusses two different approaches for regression analysis determining the corresponding coefficients. The regression analysis resulted in an equation which can approximately quantify the damage in the structure using total number of hinges formed in each

Abstract

Buildings on hill slopes are highly vulnerable due to its less resistive lateral load capacity. This type of buildings are unsymmetrical and are of in irregular configuration. There are variations in the column height which gives eccentricity to the structure as the center of mass and center of rigidity doesn’t coincide. This irregularity leads to its torsional behavior and gives us the necessity for analyzing these buildings for its base conditions and its behavior by changing its plan configuration. This paper contain the calculation of Twist which is an effective parameter to decide the behavior of the building, Axial forces on the members that can lead to collapse in the structure and about the twist variation with change in the aspect ratio so that we can know the suitability of the configuration of the building. The building on hill slopes does not behave similar to the buildings which are on plane ground. Change in the Aspect ratio means changing the length of the building in ridge direction. Changing the length in valley direction will disturb the load path of gravity load for each and every change in the structure and after some increment of the length in valley direction will fail the structure for its gravity load path. So we can’t play with the length of the building along the valley direction but changing the length along ridge direction does not effect that much to the load path of gravity load and we can obtain a best aspect ratio of the structure for that region.

Abstract

Radiating boundary conditions are essential in the numerical analysis of infinite domains such as dynamic SoilStructure-Interaction analysis. Local absorbing boundary conditions proposed by Lysmer and Kuhlemeyer (1969) are widely used in SSI analysis. These boundary conditions are developed based on the wave propagation in elastic materials. However, almost all soil materials exhibit viscoelastic properties. Badry and Ramancharla (2018) proposed the Absorbing Boundary Conditions for wave propagation in viscoelastic materials (VABC). The VABC conditions were developed from the original Absorbing Boundary Conditions (ABC) by including a spring in addition to the dashpot. In fact, these boundary conditions are inefficient when the waves impinge other than normal direction. In this paper, the radiating boundary conditions are modelled using VABC and ALID (Absorbing Layers by Increase in Damping) together to include the advantages of both the boundary conditions and to overcome the drawback of ABC on angle incidence. A detailed numerical analysis is carried out to verify the boundary conditions. The efficiency of the proposed method has been verified for both 1D and 2D wave propagation problems. The efficiency on angle incidence is verified using 2D plane strain model response through spatial Fourier Transformation. The study concludes that the proposed method is simple and reliable method for modelling radiating boundary conditions. Keywords: Local Absorbing Boundaries, Viscoelastic wave propagation, Rayleigh damping, Soil-Structure interaction, Absorbing Layers by Increase in Damping (ALID)

Abstract

In last two decades, operational modal analysis is widely used for modal identification of structures which uses ambient responses of structure for determining the modal parameters and Frequency Domain Decomposition is one of the most popular method, but seismic excitations and high damping values of structures do not satisfy the assumptions of this classical method. The dynamic modal parameters derived from earthquake responses are more reliable than those from small amplitude responses since dynamic properties of civil structures are dependent on amplitude. In recent years, a new algorithm known as refined Frequency Domain Decomposition (rFDD) is developed which uses structural response to strong ground motions that can be short in duration and is applicable for structures with light to heavy damping. The refined Frequency Domain Decomposition (rFDD) algorithm was initially developed using synthetic seismic response signals as input and later real strong motion response records were used to demonstrate the effectiveness of this algorithm for modal dynamic identification of structures under real earthquake excitations. This method is well developed to counter the problems that normally arise in modal identification and in cases of heavy damping and non-stationarity of the signal, making it lengthy and tedious to process. In this paper the main feature of this method which is Integrated Power Spectral Density matrix computation is taken and applied on mild earthquakes responses of structure. The modal parameters identified are then compared with target values obtained from classical FDD method using ambient responses and interpreted, presenting a case for usage of rFDD in simplified manner in modal dynamic identification of structures. Keywords: Operational Modal analysis, mild earthquake response, refined Frequency Domain Decomposition

Abstract

UN World Conference on Disaster Risk Reduction held in 2015 at Sendai, Japan, reiterated the need for substantial reduction in loss of life and property. Thus, assessing disaster risk and identifying key items for risk mitigation are in focus. Assessment of disaster risk is a multidisciplinary effort, which includes expected tangible physical loss, such as collapse and damage to built environment. In countries with limited resources, prioritizing risk reduction effort across the different parts of the country needs a quantitative (yet simple) approach to bring objectivity into the decision-making process. This paper presents a simple method, called Earthquake Disaster Risk Index (EDRI), for estimating relative earthquake risk across the different regions in a country; it uses three major constituents of risk, namely Hazard, Exposure and Vulnerability. Hazard is taken as the acceleration hazard specified in the national earthquake design standard, Exposure as per the permitted occupancy in the Local Municipal Byelaws, and Vulnerability through a Level 2 Detailed Qualitative Assessment of buildings built in the Town or City (with penalty points for missing features of earthquake resistance compared to an Ideal Building). First, the EDRI of a Town or City is estimated for each typology of building in the Town or City, and then the net EDRI of the Town or City is obtained as a weighted average of the EDRI of each typology of buildings using the number of buildings of each typology present in the city.