Abstract

D uring past earthquakes many buildings suffered severe structural damage. Besides damage due to inadequate design and execution, buildings and building components suffered damage due to pounding also. Pounding is defined as collision between two buildings or different parts of the same building leading to severe damage or even sometimes complete collapse. In addition to simple lateral collision, buildings may also collide in torsion mode arising due to eccentricity of mass and stiffness, causing severe damage to adjacent building. In this paper two single storey reinforced concrete buildings are considered. To study the torsional effects due to pounding, buildings with different setbacks and unequal storey levels are analyzed using SAP 2000. The effect of collision is more when structures are kept at extreme levels of setback. At different elevation levels, the pounding response changes significantly than the structures at same elevation levels. More collision force is generated at mid height of column level than other height levels because of shear amplification.

Abstract

In this paper an attempt has been made to understand the Soil Structure Interaction behavior of pile supported framed buildings under transient loading by taking the interface effects between the pile and soil. For this purpose a three dimensional Finite Element Method is used for modelling the soil-pile structure interaction using SAP 2000. A single bay five storey framed structure with a pile group foundation is modelled. First the significance of soil foundation structure interaction over fixed base analysis is studied, it has been observed that the presence of soil and foundation make a considerable change in response with a shift of natural period of the system. Next, a parametric study has been done to understand the significance of interface behaviour on soil foundation structure interaction. From the results it has been observed that under transient loading the acceleration response of top floor is reduced by two times, when contact between pile and soil has been modeled.

Abstract

In recent years, the introduction of Pre Engineered Building (PEB) concept in the design of structures has helped in optimizing design. The adoptability of PEB in the p lace of Conventional Steel Building (CSB) design concept re sulted in many advantages, including economy and easier fabricatio n. In this study, an industrial structure (Ware House) is analyzed an d designed according to the Indian standards, IS 800&1984, IS 800&2007 and also by referring MBMA&96 and AISC&89. In this study, a structure with length 187m,width 40m,with clear height 8m and havi ng R&Slope 1:10,isconsidered to carry out analysis& design for 2D frames (End frame, frame without crane and frame with 3 module cranes). The economy of the structure is discussed in terms of i ts weight comparison, between Indian codes (IS800&1984, IS800 &2007) & American code (MBMA&96), & between Indian codes (IS 800&1984, IS800&2007).

Abstract

Continental subduction and collision normally follows oceanic subduction leading to enormous crustal deformations. For understanding this mechanism oftectonic plates in collision area, which may propagate into the subductioncollision transition zone is of great interest. At the locations of high-pressure metamorphism, some places form huge crustal deformations like between Indian-Eurasian plates, and subduction at other places like Indian-Burmese plates. In either of the casesdeformation is a continuous, dynamic process. To understand the process, a study has been carried out using two dimensional finite element modeling. With the current availability of computing technology, advanced numerical techniques and material models it would be an easy task to know the parameters effecting the transition from collision to subduction process between different tectonic plates. In this paper, simpleinclined models are used to study subduction-collision transition zone. Elastic material rheology is considered for all the tectonic plates and contact analysis is used for the tectonic plate interfaces for the implementation of weak zones. Parameters consideredfor this study are geometry of plates, friction at the interface and length of the plates. This study concludes that vertical surface displacements are largely effected by the considered parameters.

Abstract

The pipeline systems are commonly used to transport water, sewage, oil, natural gas and other materials world over. These pipelines run over long distances and in some instances they cross high seismic areas including fault crossings. Many buried pipelines in India run through high seismic areas and are exposed to considerable seismic risk. These pipelines should be designed in such a way that they remain functional even when they are subjected to high intensity earthquake shaking. This paper illustrates the performance of one of the high pressure gas pipeline in the state of Gujarat, under the fault movement. Analysis shows that the burial depth of pipeline should be minimized in the fault zones in order to reduce soil restrain on the pipeline during fault movement.

Abstract

The earthquake resistant design of structures according to the existing design philosophy aims to ensure that during their lifetime, the structures resist the maximum possible earthquake without collapse. This philosophy ignores the fact that for the allowable damage at the end of the design life, it is necessary to account for the seismicity of the area in a comprehensive manner i.e., in terms of magnitudes with proper spatial distributions around the site. It is also necessary to estimate damage due to each of these events and also cumulative damage till date. Such a procedure is proposed in the paper and it is applied to heritage structures which stand for longer duration compared to ordinary buildings. As a case study, the proposed methodology is used to evaluate damage to Golkonda Fort located in Zone II according to IS 1893-2002. Proposed approach is based on the estimation of Power spectral density function (PSDF) of earthquakes already occurred and then estimation of damage to the structure during each of these events. Golkonda Fort is modeled using Applied Element Method (AEM). Pushover analysis of the AEM model is also carried out. The damage computed from the proposed approach is plotted on the fragility curve obtained from the push over analysis for comparison.

Abstract

Response of a structure subjected to gravity and lateral loads depends on the boundary conditions assigned at the base of structure in numerical modeling. Most of the structures are analyzed considering fixed base, but in reality, foundation is not fixed. The fixity depends on the interaction between the soil and foundation. In most of the cases base of a structure undergoes small amount of rotation because of flexibility induced by soil especially at the time of earthquake. Difference in boundary conditions used in analysis and in actual conditions will lead to improper estimation of the design forces, to reduce such effects in numerical analysis fixed base of structure can be replaced by springs or structure base resting on soil to obtain results closer to that of actual base conditions. Stiffness of the spring depends on geotechnical parameters as well as on the dimensions of the foundation. In the present paper an attempt is made to understand the difference between the Linear and Non Linear response of a frame having fixed base, spring base and with soil. Stiffness of springs for spring base structure is calculated as per ATC-40 [1] and JICA [7]. Analysis of structure with soil modeling is complex, specifically for Non Linear behavior for this Applied Element Method is used. Linear and Non Linear response is compared in terms of stress resultants and capacity of the frame respectively, for non linear response static pushover analysis is done. From the study, it is observed that the actual capacity of structure is overestimated assuming fixed base. The fact that the initial stiffness of the structure is governed by the soil stiffness can be clearly stated from the obtained pushover curves. It is also recommended that analysis of structure should be done considering spring base in place of fixed support.

Abstract

Tall building construction is booming in India. There are several earthquake safety issues involved in planning, designing and constructing these buildings. Some issues related to seismic behaviour are still not resolved even in developed countries, like USA and Japan. Researchers all over the world are continuously working towards development of latest techniques for improving earthquake safety of tall building. The situation in India is that there are few codes which specify guidelines for earthquake resistant design of structures. However, the guidelines given in this code are useful for regular and relatively small, low-rise buildings. When it comes to tall buildings, every structure is special, several parameter needed to be considered. One such parameter is T. Existing empirical natural period equation given in IS 1893 is suitable only for small to medium rise buildings. There is a serious need for proposing equation for high rise buildings. In this paper an attempt is made to compare empirical equations for natural period of different countries. Study gives that there is a need to propose the new time period formula exclusively for Tall structure based on Indian condition.

Abstract

The overall capacity of a structure depends on the strength and deformation capacity of the individual components of the structure. This paper deals with the prediction of effect of a member on global performance of the structure. The performance of a 5 storey RC frame, designed for Indian standard codes has been presented. Non linear pushover analysis is used to draw the capacity curve. During the pushover analysis when the structure becomes unstable, the failed members are identified. In the present study, end columns of the bottom storey which exists in failed members are strengthened by increasing the longitudinal reinforcement, increasing the c/s area and reducing the shear reinforcement spacing. Increase of longitudinal reinforcement or decrease of shear reinforcement spacing not effected much the strength capacity, but the ductility is increased in both the cases. Increasing the c/s area of two columns increased the strength and stiffness of the frame, but the ductility is increased up to a certain limit and then decreased. Parametric study also done for individual column performance with same geometric and material properties as it exists in the frame. The performance of individual column is completely different with frame performance though the geometric and material properties are same this is because of the frame action where redistribution of forces takes place when the member fails in the frame.

Abstract

Modern research in India on dams has entered a distinct phase subsequent to the damage to Koyna dam, located in hitherto considered stable continental part, due to an earthquake on 11th December, 1967 in Koyna district, India. Out of about 5,100 large dams in India, a significant number are in moderately high and high seismic zones. As such they may be prone to probable instability to the dam’s structure due to earthquake resultant impacts. Even though none of the dams other than Koyna got damaged in India due to high magnitude earthquake activity, since 1967, it is felt necessary to understand the behaviour of dams due to water load coupled with dynamics of faults that are present in the vicinity of the dam, as dam failures due to earthquake activity are reported from different parts of the world. In this paper, damage to Koyna dam due to a fault motion caused nearby has been studied. A concrete gravity dam is selected from the National Importance Dams of India. Structure-1(S1) as a concrete gravity dam with foundation and structure-2 (S2) as a concrete gravity dam with foundation and soil strata are numerically modeled using Applied Element Method (AEM). Displacement at the base of soil strata is given to generate reverse fault effect on the dam. Behavior of dam is studied by direct and sub-structure methods. In the direct method, the effect of fault motion on dam is studied in S2, by modeling dam at different locations on foot wall and hanging wall. In sub-structure method, free-field accelerations are recorded at different locations on foot wall and hanging wall while only the sub-structure is subjected to fault motion. The recorded accelerations on the surface are used as input to analyze super structure S1. Comparison on behavior of dam in models S1 and S2 is later drawn.