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

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

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

Bhuj earthquake of 26 January 2001 caused 14,000 casualties. Main reason for such huge casualties is low earthquake awareness and poor construction practices. Based on the technology advancement and knowledge gained after earthquake occurrences, the seismic code is usually revised. Last revision of IS 1893 (Criteria for earthquake resistant design of structures) was done in 2002 after a long gap of about 18 years. Some new clauses were included and some old provisions were updated. Assuming that concerned authorities will take enough steps for code compliance and the structures that are being constructed are earthquake resistant. In this light, what will happen to the safety of pre-code revision structures? These structures carry major percentage of vulnerable structure stock. Even if we have a very good disaster response system, it is impossible to reduce earthquake damage without considering the safety of pre-code revision structures. In this regard, a comprehensive study of seismic risk assessment of Gujarat is necessary. As a pilot study, government of Gujarat selected Gandhidham and Adipur cities. Rapid Visual Screening (RVS) was conducted on 16000 buildings in Gandhidham and Adipur cities. Initial results reveal that there are large variety of construction practices, however, predominantly RCC and masonry structure were found. RVS score of these structures reveal that in general buildings are of low quality and further evaluation and strengthening of buildings is recommended. Keywords: RVS, performance score, preliminary assessment and detailed assessment Earthquake Vulnerability Assessment of Existing Buildings in Gandhidham and Adipur Cities Kachchh, Gujarat (India)

Abstract

Transmission tower lines are one of most important life-line structures. It is necessary that these structures are designed for seismicity. The dynamic behavior of a single transmission tower and transmission tower system that are linked by conductors has been studied in this research work. The dynamic analysis is performed on both the single transmission tower and the tower line system. The wind force acting on the tower is considered as an equivalent static force. The seismic analysis of the tower has been performed in SAP2000 Nonlinear computer program (SAP2000, Computers and Structures). The tower elements are modeled using 3 D frame elements. The tower has been subjected to North-ridge strong ground motion (1994) and the Koyna strong ground motion (1967) to study the dynamic behavior as described in the present work. Parametric study has been carried out by studying the influence of cable on the tower when the force in the cable is applied at different angles to the cross arms. The non-linear material behavior of the leg members of the tower has been studied when it is subjected to the two strong ground motions considered. To understand the non-linear behavior of the material bi-linear model has been considered and it is analyzed in the present work.

Abstract

Bamboo was used as construction material for housing since times immemorial. However, with the advent of materials like concrete and steel, its use has been signicantly reduced in last 50-100 years. On the other hand concrete and steel has large carbon footprints before even they are born. Use of wood has already banned by Central Public Works Department (CPWD). Similarly, State PWD's are also trying to follow the same. In this scenario, there is a great need to demonstrate cost eective housing with alternate technologies, especially like bamboo. However, for promoting bamboo as natural building material for housing, several dificulties are involved. This paper discusses the dificulties involved in promoting bamboo as sustainable construction material.

Abstract

Ask a common man about past earthquakes in india. Most people would answer Latur earthquake of 1993 and Bhuj earthquake of 2001 in addition to tsunami devastation of Dec 2004. However if we look at the figure we can see many events have occurred in last two decades. But why we remember only few events. The reason being obvious i.e life loss during these events. From the figure we can easily understand that during during last decades we have witnessed 6 moderate earthquake.

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. In addition to the understanding of the phenomenon of near fault ground motion 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 and its effect on the surface peak ground acceleration. In the present two dimensional study rupture propagation due to bedrock motion has been observed for different shear wave velocity. A model of size 1000 X 150 m is selected for this purpose. It has been observed that as the stiffness of the media is decreasing, the affected surface is decreasing and also width of the shear crack zone is decreasing. Secondly, we attempted to study the ground motion on the surface due to the bedrock motion in presence of boulders in the soil media. 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 and in the vicinity of the rupture zone. Finally, we performed the …

Abstract

This paper presents the preliminary seismic hazard assessment of the peninsular India (lat. 10-26N and long. 68-90E) which is considered to be seismically most stable land masses of the Indian plate. Past major seismic events in this region (Koyna, 10 Dec 1967; Bhadrachalam, 13 Apr 1969; Hyderabad, 30 Jun 1983; Latur, 30 Sep 1993; Jabalpur, 22 May 1997; Bhuj, 26 Jan 2001) clearly shows that the seismicity of the area is highly varying. There were five damaging earthquakes with magnitudes Mw 6.0 occurred in this region, stressing the importance of detailed seismic hazard assessment for this region. For India, Bhatia 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 detailed seismicity, tectonic and geologic characteristics. Around 110 major faults are considered in this present research study for estimating the peak ground acceleration at the bedrock level using the attenuation relationships developed by Atkinson and Boore. The considered area under peninsular region has been divided into grid pattern with 10x10 and around 280 site specific locations are considered for the detailed analysis. From this study, it is observed that 30% of PI is overestimated and 12% is underestimated when compared with PGA values for various regions provided in Indian seismic code IS: 1893-2002. The results show that there is a great need for carrying out the detailed microzonation of an area within the peninsular India.

Abstract

Heritage could be something which is acquired from one’s ancestors. It could be natural heritage, cultural heritage, food heritage, built monumental heritage; or it could be the virtue of vernacular architectural & construction techniques which people from many different communities have secured from their ancestors through generations. But, with the advent of modernism, vernacular architecture, construction techniques and skills are fast disappearing as there is simply no demand for them anymore. Similar to the case with many of our traditional crafts, we are facing the risk of extinction of skills for buildings. As more and more constructions in villages are turning towards cement and steel, the traditional and sophisticated art of construction will fade away sooner rather than later. The preservation of such skills and, in fact their propagation must be an important priority for stakeholders and policy makers. This paper not only the presents the risks of extinction which these heritage construction techniques & skills are facing from modern mind-set, but it also presents some of the vernacular building typologies in seismic zones IV & V showing, their uniqueness in intertwining the culture and resistance to natural forces of the region.