Abstract

In the proximity of an active fault, spatial variation of peak ground motion is significantly affected by the faulting mechanism. It has been observed that near fault ground motions consists of different characteristics compared to the far fault ground motions. Near fault records, in the distance range of less than 100 m from the faults are not available except for few cases. Therefore numerical simulation of ground motions for such near-fault situations is necessary. There is a need to enhance our understanding of the possible potential hazard that can be caused due to the future rupture activity by understanding the phenomenon of surface faulting. In this paper we propose numerical simulation based on discrete modeling to investigate the fault rupture propagation. Initially a two dimensional study is done for understanding the crack propagation due to various types of bedrock movement. A model of size 1000x150 m is selected for this purpose. It is observed as the stiffness of the media is decreasing, the affected surface is decreasing and also width of the shear crack zone is decreasing. However in the dynamic analysis we can observe the significant increase in amplification in soft media. Secondly, we attempted to study the presence of boulders. Surface faulting has been examined by keeping the boulder at different positions. We find that there is an increase in the shear zone as well as the PGA on the surface when the boulder is present on the foot wall. Finally, we performed the analysis using layered media and studied the affect of crack propagation and also the variation of peak accelerations Findings from the study can be utilized to assess the …

Abstract

Experiences from past earthquake disasters clearly shows that the ground motion was responsible for majority of property and life loss. Among the collapsed structures during the 1964 Niigata earthquake, the 1995 Kobe earthquake, the 1999 Koceli earthquake, the 2001 Bhuj earthquake and the 2004 Sumatra earthquake, excessive damage was occurred to pile supported bridges, towers, chimneys, high rise structures, etc. In view of this there is a need to study the complex behavior of soil-pile-structure interaction problems using numerical methods. In this research paper, a numerical study is carried out to understand the dynamic soil structure interaction of a high rise structure in a visco elastic half space in the presence of near by pile supported structures. The structure soil structure interaction is modelled by considering the direct methodology using a Finite element method based code ANSYS 10. Initially a two dimensional study is carried out for understanding the seismic response of group of high rise structures supported on pile foundations. The linear super structures are considered as framed structures of different dynamic characteristics suported on group of piles. Different case studies are made one in which the group effect of structures supported on piles are considered like group of two identical structures, group of three identical structures and group of three different structures, second one in which the effect of variability in structure height is considered like 5 storey structure, 10 storey structure and 15 storey structure and the third one in which the effect of variability in structure shape is considered. For each case the effect of structure …

Abstract

Pipelines are common transportation means for oil and natural gas, which act as an important lifeline facility for any nation. Often the design of these pipelines is a difficult task because they commonly are installed underground passing through different types of soil media. Many of these existing pipelines run through the faulted area, which continuously exposed to considerable risk of failure due to movement along the fault. In this paper, a numerical study is carried out to understand stress development in buried pipeline subjected to fault motion with Mundra-Delhi pipeline as a case study. For this purpose, a 3D finite element program is developed and the same is used to study stress development in the pipe subjected to fault motion. Also here study has been done to find out the effect of different soil media and effect of fault-pipeline angle for both strike slip and dip slip fault motion.

Abstract

In the case of foundations of bridges, transmission towers, offshore structures and for other type of huge structures, piles are also subjected to lateral loads. This lateral load resistance of pile foundations is critically important in the design of structures under dynamic loading. Load carrying capacity and load deformation behavior of a single pile and group of piles subjected to lateral load is obtained using nonlinear finite element method of analysis. According to Poulos and Davis (1980) the maximum deflection of the pile is the major criterion in its design and made the initial attempts to study the lateral behavior of piles included twodimensional finite element models in the horizontal plane. Several investigations have attempted to study the behavior of pile under lateral load using 3D finite element analysis. In this paper a detailed study on the piles subjected to lateral loads are investigated.

Abstract

The amplification of ground motion is being observed during major earthquake events all over the world and is highly dependent on the local geological, topography and geotechnical conditions. In view of this there is a great need to study the local site effects in a seismically active region. In this paper, the numerical modeling of infinite media is carried out by using transmitting boundary condition. Wave interaction with different kinds of boundaries like fixed and viscous boundary is discussed. The heterogeneities in the soil media are taken into account by considering the soft clay and the rock inside the half-space. Peak ground acceleration at the surface is plotted and local amplification of soils is studied by giving Elcentro ground motion as input at the bed rock for both the cases. In the half-space where clay is present, PGA is amplified by a factor of 2.5 with respect to input. More energy is concentrated in the half-space where clay is present. In the half-space where rock is present the area adjacent to the rock is getting amplified as energy is concentrated around the rock.

Abstract

Many countries have become victims of terrorism on a large scale. Bombs have exploded in and around buildings in many countries causing civilian causalities and structural damage. A bomb explosion with in or around a building can have catastrophic effects, damaging and destroying internal or external portions of the building. Bomb damage to buildings depends on the type and layout of the structure, material used, range of the located explosive device and the charge weight. The impact from the blast causes debris, fire and smoke and hence can result in injury and death of occupants. Escape of the occupants and protection of the valuable documents, equipments, property is possible only when there is minimum damage to structures. This may be achieved by designing the building structures for blast loading. This attempt gives basic idea to all the consultants in estimating the blast loads over the building structures.

Abstract

Heritage structures bears a valuable testimony of ancient cultural heritage of any country. Among these structures statues, iconic emblems plays significant role. In the proposed to study the vulnerability of monolithic statues to earthquake ground motions. Initially we used the equations developed by Housner for studying the dynamics of rigid blocks. Parametric study was conducted to study the inuence of size of the block and input parameters such as amplitude and frequency on the behaviour of the block. The study was extended to generate safe surface for the block of given dimensions. This surface gives the information that with any combination of parameters such as amplitude of vibration, frequency of vibration and duration of vibration, if the point lies outside the surface then block overturns otherwise it is safe. To verify the above formulation we selected four statues, viz, Gomateswara statue, Christ the Redeemer, Statue of Liberty, Guinyin Statue for case study. Initially all the statues were idealized like rigid blocks and later safe surfaces were developed for each statue. Since each statue is having different dimensions, surfaces were are also of different nature. Later, eighteen earthquake records were selected and strong ground motion parameters were estimated. Finally every statue was tested for the safety during the earthquake events. It was found that as the height of the statue is increasing its vulnerability is increasing. However, for all the given ground motions, none of the statue overturned.

Abstract

This paper presents the detailed seismic hazard assessment of the peninsular India (lat. 8°-28°N and long. 67.5°-90°E) which is considered to be seismically most stable landmasses of the Indian plate. Past seismic history in this region (Koyna, 10 December 1967; Bhadrachalam, 13 April 1969; Broach, 23 March 1970; Hyderabad, 30 June 1983; Latur, 30 September 1993; Jabalpur, 22 May 1997; Bhuj, 26 January 2001 etc) clearly shows that the seismicity of the area is varying. There were more than five damaging earthquakes with magnitudes greater than Mw 6.0 have occurred in this region, stressing the importance of detailed seismic hazard assessment for the region. For India, Bhatia et al. (1999) published a probabilistic seismic hazard map based on several well identified and prominent source zones in the country. An attempt has been made in this paper to study the present seismic status of this region incorporating the seismicity, tectonic and geological characteristics and using the collected earthquake data Peak Ground Acceleration was estimated using the attenuation relation developed by Iyengar and Raghukanth (2004). Estimated PGA values were used to compute the deviation with respect to assigned PGA values for various regions provided in Indian Standard code IS 1893:2002. The results show that, the estimated PGA in many areas of the Peninsular India is more than the specified value in the current seismic macrozonation map of the country. This provides an important basis for attempting the detailed microzonation of an area within the Penisular India

Abstract

Indian Subcontinent is one of the seismically active regions of the world. The seismicity of India can be divided into 4 groups: Himalayan Region, Indo-Gangetic Plain, Kutch-Kathiawar Region and the Peninsular India (Ref EU Report 2003). Himalayas are one of the rare sites of continent to continent collision and also tectonically very active belt. The high seismicity of the region can be observed from the past events occurred in the region as shown in Figure.1. Depending on the past earthquakes, Bureau of Indian Standards has prepared the Seismic Zonation map of India (IS-1893-2002), which divides the country into 4 different zones. As per the zonation map 57% land of the country falls under high seismic zone. These maps do not consider the frequency of occurrence of earthquakes; hence they do not divide the country into regions of equal hazard and risk. For cultural heritage and other important structures, these maps act only as a guideline for the expected intensities. For those structures, site specific seismic hazard maps have to be generated specially for use. Rigorous quantifications of seismic hazard in detail for the Delhi region have not been carried out so far. Chouhan (Proc.INSA) estimated the focal depth of earthquake around Delhi to be about 8 km. His frequency-magnitude analyses lead to the conclusion that the maximum size of an earthquake that may occur in this region would be 7.6. The work of Srivastav and Roy (1982) indicates that in a period of 50 years a magnitude 6 earthquakes are almost certain and that there is 80% probability of a 7 magnitude event visiting the region. Khattri (1992) has carried out an exercise estimating the seismic hazard for the northern region of the country. According to this study in a fifty year window of 1983 - 2033, the peak ground accelerations around Delhi would be 0.2 g with 10% probability of exceedence. Delhi and its environs have not yet experienced this level of ground vibration in the above time period. Even if these estimates need further refinement they indicate the nature of events expected for Delhi city (Iyengar, 2000). Keeping in view all these studies, the effect of any future earthquake in Delhi region is studied in this paper.

Abstract

This paper presents the detailed seismic hazard assessment of the peninsular India (lat. 8°-28°N and long. 67.5°-90°E) which is considered to be seismically most stable landmasses of the Indian plate. Past seismic history in this region (Koyna, 10 December 1967; Bhadrachalam, 13 April 1969; Broach, 23 March 1970; Hyderabad, 30 June 1983; Latur, 30 September 1993; Jabalpur, 22 May 1997; Bhuj, 26 January 2001 etc) clearly shows that the seismicity of the area is varying. There were more than five damaging earthquakes with magnitudes greater than Mw 6.0 have occurred in this region, stressing the importance of detailed seismic hazard assessment for the region. For India, Bhatia et al. (1999) published a probabilistic seismic hazard map based on several well identified and prominent source zones in the country. An attempt has been made in this paper to study the present seismic status of this region incorporating the seismicity, tectonic and geological characteristics and using the collected earthquake data Peak Ground Acceleration was estimated using the attenuation relation developed by Iyengar and Raghukanth (2004). Estimated PGA values were used to compute the deviation with respect to assigned PGA values for various regions provided in Indian Standard code IS 1893:2002. The results show that, the estimated PGA in many areas of the Peninsular India is more than the specified value in the current seismic macrozonation map of the country. This provides an important basis for attempting the detailed microzonation of an area within the Penisular India.