Abstract

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.

Abstract

Strong ground motions are the most desirable for the earthquake-resistant design of structures. If the site at which a major construction is required has less ground motion records, then artificial ground motions will serve the purpose. In highly seismic areas like Kashmir and the Himalaya region, artificial ground motions are quite helpful. Artificial accelerograms can be generated either through analytical or numerical procedures. Several methods were suggested in the literature for generating artificial ground motions. However, suitability of method for the region is to be understood before application. The main objective of this paper is to generate synthetic accelerograms of May 01, 2013, Doda earthquake using modified semi-empirical approach. A MATLAB code is written to generate the ground motion records of 1991 Uttarkashi earthquake and also validate the results. Based on effectiveness of the code …

Abstract

Indian standard code of practice for plain and reinforced concrete IS 456 was last revised in 2000 after 22 years of the third revision. The major revision done in the new code is shift in design philosophy from working stress method to limit state method. The new code has not shown any significant changes in the concepts of structural design, material properties for high strength of concrete and steel, material grade limitation for seismic design, design of deep beam and walls, design of infilled frames, design of beam column joint and provisions for effective length of frame members. The code does not clearly mention about mode of failures such as shear, flexure in structural members. In the present paper a comprehensive literature review on the design strength of materials, stress stain curve for concrete, steel and confined concrete, partial safety factors and limitations/recommendations for usage of concrete grade and reinforcement steel grade in design provisions of Indian Standards, American Standards, European Standards, New Zealand Standards, Japanese Standards and from the latest available literature is done.

Abstract

Urbanization is rapidly increasing in almost every city in India. Huge infrastructure developmental plans have been laid by the government and private organizations. Large advertising boards of tall buildings (ranging from 30 to 50 floors) already started attracting people to invest in these infrastructure plans. However, from the point of view of seismic hazard prevailing in the country,“Will these buildings survive during future earthquakes?” is a question to be answered before proceeding for construction. In last 2.5 decades, 7 moderate earthquakes have been witnessed: Bihar-Nepal border (M6. 4) in 1988, Uttarkashi (M6. 6) in 1991, Killari (M6. 3) in 1993, Jabalpur (M6. 0) in 1997, Chamoli (M6. 8) in 1999, Bhuj (M6. 9) in 2001, A&N Islands (M9. 3) in 2004, Muzaffarabad (M7. 2) in 2005, Sikkim (M6. 8) in 2011 and more recently Twin Earthquakes in the neighborhood Nepal. These earthquakes have clearly exposed the lack of understanding of seismic hazard of the country. Sometimes, even when the hazard is understood, the lack of knowledge is exposed on earthquake resistant design and construction practice of reinforced concrete structures. The professionals involved in building construction should be more concerned with the safety of building infrastructure during future earthquake events. Among several aspects, natural period of building is one of the crucial parameters which decide the seismic demand of the building. Present study focuses on developing an empirical expression of fundamental natural period of RC tall buildings in India with the help of ambient vibration tests. Through the study it is found that the periodheight relationship is …

Abstract

Past earthquakes in India have caused maior damage to structures even for lesser peak ground acceleration than it is designed for. This is because of lack of incorporation of earthquake resistant design features in the structure. In India most of the structures are designed for gravity loads only. It is due to lack of knowledge and awareness of earthquake resistant design and the myth that earthquake resistant design is costlier. in this view, present study aims at comparing normal detailing as per IS 456: 2000 and ductile detailing as per IS 13920 (Proposed draft) in terms of its capacity, damage and cost. A parametric study has been carried out by considering a 5 storey building, designed for gravity loads as well as, lateral load as per IS 18931002, for different seismic zones (Zone II to V) and results are compared. Static Non Linear (Pushover) analysis and fragility analysis are performed for estimation of post damage …

Abstract

Different shapes of column cross sections are possible for design of structures which ultimately affect the overall performance. Various cross section reinforced concrete columns like square, circular, plus, L, and T shaped with same cross sectional area and reinforcement are modelled. In order to make this study more practically applicable, three models each of multi storeyed structures of different number of storeys were analysed for non-linear static responses. One of the models used conventional rectangular columns, second used circular columns throughout and another model employed combination of various geometrically possible column cross sections such as L, T and plus (+) shaped columns. The study compares response modification factors for above mentioned structures.

Abstract

Earthquake performance of Reinforced concrete bare frame has been well documented in the past. Also, damage patterns in reinforced concrete frames during the past earthquakes have been extensively studied. However, more recently, several destructive earthquakes, including the 1999 Athens (Greece) earthquake, the 1999 Ýzmit and Düzce earthquakes (Turkey), 1999 Chi Chi (Taiwan) earthquake, 2001 Bhuj (India) earthquake, and the 2003 Boumerdes (Algeria) earthquake, have given more insights to performance of RC frame constructions. In order to understand the complete behavior of RC frame, it is required to study the performance from no loading condition till the complete collapse. In this paper, a set of four bare frames designed as per Indian Standards are considered. All the frames are subjected to Northridge earthquake ground motion. Newly developed numerical model called Applied Element Method (AEM) is considered for analysis. Initially, the linear analysis is carried out and the results were compared with commercially available software. Later, progressive collapse analysis is performed. Collapse process of each bare frame is discussed in detail.

Abstract

The process of crustal deformation depends on the type of tectonic plate interactions viz. convergent, divergent and transform. For all the three cases, the topography effect is different. However, higher elevations and huge compressions are measured at convergent plate margins. Past observations reveal that these margins are very much prone to great earthquakes especially at the locations where oceanic plate is subducting underneath a continental plate. For the purpose of understanding horizontal and vertical displacement profiles on both the plates, a study considering the interaction between oceanic and continental plate which are resting on lithosphere mantle is carried out. Two dimensional finite element models were developed and analyzed using commercially available software ABAQUS. Contact properties are defined between plates so that effect of friction is calculated. All plates have an elastic rheology and slip is allowed at the interfaces. The models demonstrate that inclination angles leading to subduction or collision affects the length of vertical and horizontal displacements. Also, increasing the coefficient of friction decreases the vertical deformation but increases the amount of subsidence. This study concludes that the inclination angle and coefficient of friction plays a vital role for the development of varied crustal deformations at convergent plate margins.

Abstract

Nuclear power plant is one of the largest source of producing electricity in India after thermal, hydroelectric and renewable sources of electricity. As of 2013, India has 21 nuclear reactors in operation in 6 nuclear power plants, having an installed capacity of 5780 MW and producing a total of 30, 293 GWh of electricity while six other reactors are under construction and are expected to generate an additional 6,100 MW. After 2011 Fukushima earthquake in Japan, safety of nuclear reactors has become a major concern. For assessing safety it is utmost important to have information on expected earthquake events. In case of lack of sufficient information, artificial ground motions may be generated by using geological features and faults information. This study presents simulation of near field generated ground motions of Rawatbhata nuclear power plant. For this purpose, three faults nearer to the power plant have been selected to the generate ground motions using semi-empirical approach. It is observed that as the source (M) of the earthquake increases, the amplitude of the ground motion, duration and energy content increases. Similarly, the spectral accelerations also increase due to all three active faults.

Abstract

Improperly designed brick masonry walls cause undesirable effects under seismic loading in both brick masonry in-filled reinforced concrete (RC) frames and masonry load bearing wall structures. Doors and windows (openings) are unavoidable components in brick masonry in-filled RC structures and masonry load bearing wall structures because of its functional and ventilation requirements. The presence of openings in brick masonry walls reduces the lateral stiffness and strength of the wall in both RC and load bearing structures, which changes the actual behavior of structure. If these openings are located in the restricted zones like areas within middle two thirds of a wall wall, then the wall needs to be strengthened by providing necessary horizontal/vertical (bands) structural elements such as lintel or lintel bands around them. Lack of such structural elements may cause the structure to undergo severe damage during the earthquake event. In this paper, two case studies,(a) the presence of openings in infill wall with or without lintel and lintel band (b) the presence of openings in load bearing wall with or without lintel and lintel band is studied, to know the nonlinear response of brick masonry in-filled RC frame and load bearing wall under seismic loading. To understand the behaviour of the infilled frames and load bearing wall, a two dimensional (2D) infilled frame and load bearing wall is modeled and analyzed using a tool based on Applied Element Method (AEM). Nonlinear static pushover (SPO) is performed to estimate capacity of the models.