http://localhost:8081/jspui/handle/123456789/113 Fri, 25 Jul 2025 21:04:29 GMT 2025-07-25T21:04:29Z http://localhost:8081/jspui/handle/123456789/17945 Title: SENSITIVITY OF GROUND MOTION SIMULATIONS TO EARTHQUAKE SOURCE PARAMETERS Authors: Vijay, Sandeep Abstract: Strong motion data provides an important mean of understanding the characteristics of earthquakes as it provides crucial information related to the frequency content and duration of ground motion. The sensitivity of the strong ground motion to source effects, variations in the transmission path and the effect of local site conditions provides useful insight with respect to response of built up environments to earthquakes. In this regard it is important to generate synthetic data for various earthquake environments in regions where strong motion data is not available. In this study three reference scenario earthquakes are used for generating synthetic data for the Dehradun city at the bed rock level using a stochastic method. The uncertainties related to the source and path effects in the simulated data are needed to be resolved and that is where the study becomes fruitful. For this purpose, 31 scenario earthquakes are modeled for each reference scenario by changing the various source and path factors. The variation in mean ditThrences of the absolute values of PGA and PGV for the reference scenario and each scenario earthquake gives a good insight into the sensitivity of these simulations to the various parameters. The source duration was found to be the most sensitive parameter among those considered. The ground motion simulations showed negligible sensitivity effect to change in site diminution factor kappa. Among others, the stress drop (Ac) and the attenuation parameters Qo and ij were found to have significant effect on the ground motion simulations. In the different simulations the frequency range of 7-17 Hz was found to be critical in terms of spectral accelerations. Sat, 01 Jun 2013 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/17945 2013-06-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/17944 Title: INFLUENCE OF LONG WELDED RAILWAY TRACK ON FATIGUE OF STEEL RAILWAY BRIDGES Authors: Pramod, Arnepalli Abstract: The increase of the population and the need for the quick transportation of the men and material in the modernized world has le-d to the requirement of man to deal with high velocities with greater comfort at low cost. In the rail transportation system, the use of the long welded railway track is one of the method which has grabbed the attention of the engineers for attaining higher speeds, with smooth riding experience and cost efficiency. The existing infrastructure should be checked and analyzed for the effects with this replacement and should be assured for its safety. Since, with the replacement of the long welded railway track on the bridge, the length of the track extends beyond the length of the bridge. As a result, the frequency characteristics and the response of the bridge changes when subjected to dynamic loading such as a train passing on it. Hence study should be made before the replacement of the long welded track is done. A complete study on the variation of the thtigue life has been done for 30.5meter and 76.2 meter truss bridges for all the routes and all the trains with a speed of 300Kinph. A comparison of the dynamic analysis and the static analysis with the dynamic augmentation factor has also been made in the report. Also the dynamic response of the bridge with the variation of velocity has been done for a train. From the analytical results obtained in the study, it can be justified that the the bridges are safe from fatigue point of view along with a little increase in life of the bridge. Itis also found that the dynamic augmentation factors given are not adequate for all the spans Sat, 01 Jun 2013 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/17944 2013-06-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/17942 Title: EFFECTS OF LIQUEFACTION ON SHALLOW FOUNDATIONS Authors: Singh, Manendra Abstract: Design of foundations in earthquake prone areas needs special considerations. Shallow foundations may experience a reduction in bearing capacity and increase in settlement and tilt due to seismic loading. The reduction in bearing capacity depends on the nature and type of soil and ground acceleration parameters. International Building Code generally permits an increase of 33 % in allowable bearing capacity when earthquake loads in addition to static loads are used in design of the foundation. However, according to Indian Standard (IS: 1893- 2002), when earthquake forces are considered, the allowable bearing pressure in soils shall be increased by a margin of 0 to 50%, depending upon type of soil. Amount of settlement of shallow foundation is much greater for the liquefaction condition compared to the non liquefied state. Construction of shallow foundation on liquefiable soils shall be allowed only after proper soil treatment. Construction of shallow foundation on liquefiable soils is possible in the presence of a sufficiently thick and shear resistant nonliquefiable soil crust. Due to earthquake, excess pore pressure build up and the associated shear strength degradation of liquefiable soils may result in reduction in bearing capacity and increase in settlement of shallow foundations. Cascone and Bouckovalas (1998) shown that shear strength of liquefiable soil is expressed in terms of a degraded friction angle. Since friction angle is used for determination of bearing capacity factor, therefore reduction in friction angle leads todecrease in bearing capacity and factor of safety. This degraded friction angle can be used for evaluating bearing capacity and degraded factor of safety of liquefiable soil by any analytical method such as Terzaghi, Meyerhof, Vesic and IS 6403:1981. Liquefaction induced settlement are correlated to the seismic excitation characteristics and the degraded factor of safety. The presence of unliquefiable layer may drastically reduce settlement and increase the bearing capacity of footing. Clay crust, dense sand and improved sand may be used as a unliquefiable layer. Thickness of unliquefiable layer affects significantly the performance of shallow foundation under liquefaction. The peak ground acceleration much affects the liquefaction induced settlement than the bearing capacity. The depth of liquefiable layer, also affects the liquefaction performance of shallow foundations Sat, 01 Jun 2013 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/17942 2013-06-01T00:00:00Z http://localhost:8081/jspui/handle/123456789/17941 Title: REPAIR AND RETROFITTING OF HIGHWAY BRIDGES USING FRP TECHNIQUE Authors: Wankhede, Atul Vasantrao Abstract: Many existing reinforced concrete structures were designed before the introduction of modern seismic code and are thus vulnerable to collapse in the event of an earthquake. It is often more economically feasible to retrofit these structural components than to completely replace them. In order to strengthen these susceptible reinforced concrete structures against seismic loading, it is important to understand the progression of damage and mechanisms causing collapse in such structures under both gravity and seismic loads. The comparative study of three square column section with increasing cross sectional size and confinement effectiveness from spacing of stirrups up to 4hhl layer of GFRP wrapping is carried out in the dissertation work. The analysis consist of axial load Vs axial deformation relationship, moment-curvature, ductility and shear capacity of column. The analysis results shows that as the size of column section increases then confinement effectiveness of GFRP jacketing decreases because of the hoop stress is inversely proportional to the diameter of column and confinement effectiveness due to decreasing spacing of transverse reinforcement is very small as compare to increasing layer of GFRP wrapping Sat, 01 Jun 2013 00:00:00 GMT http://localhost:8081/jspui/handle/123456789/17941 2013-06-01T00:00:00Z