Faculty Publications

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Author: search.filters.author.Jayalekshmi, B.R.Subject: search.filters.subject.Base shear

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    Nonlinear Seismic Response Analysis of Mid-rise RC Buildings Founded on Soft Soil
    (Springer Science and Business Media Deutschland GmbH, 2024) Mathews, M.; Jayalekshmi, B.R.; Venkataramana, K.
    Multi-storeyed RC structures have become a significant part of modern construction. Damages induced by earthquake excitations on RC structures depend not only on the structural behaviour of the superstructure but also depend on the type of foundation and soil on which the structure is founded. The present study aims to understand the impact of soil-structure interaction on the seismic response of mid-rise RC buildings. Nonlinear static pushover analysis of RC frame buildings having 4 and 6 storeys has been conducted considering fixed base condition and flexible base. The effect of SSI is analysed by creating 3D building models using finite element software considering the SSI between the building model and the soil on which the building is founded. The nonlinear behaviour of the building components is incorporated in modelling using the concrete damaged plasticity model by defining the compression and tension damage parameters. The consideration of nonlinearity of soil and structure is found to alter the system’s dynamic characteristics by an increase in the natural period. The pushover analysis results indicate a comparable variation of the force–displacement curves for the building models with and without considering SSI and show an increase in the lateral displacement value while considering the SSI effect. The results presented in this study illustrate the inefficiency of fixed base modelling in assessing the dynamic response of mid-rise RC buildings by highlighting the disparity in the fundamental time period and flexibility of the building under the effect of SSI. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
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    Seismic response analysis of reinforced concrete frames including soil flexibility
    (Techno-Press, 2013) Jayalekshmi, B.R.; Deepthi Poojary, V.G.; Venkataramana, K.; Shivashankar, R.
    The seismic response of RC space frame structures with isolated footing resting on a shallow soil stratum on rock is presented in this paper. Homogeneous soil stratum of different stiffness in the very soft to stiff range is considered. Soil, footing and super structure are considered to be the parts of an integral system. A finite element model of the integrated system is developed and subjected to scaled acceleration time histories recorded during two different real earthquakes. Dynamic analysis is performed using mode superposition method of transient analysis. A parametric study is conducted to investigate the effect of flexibility of soil in the dynamic behaviour of low-rise building frames. The time histories and Fourier spectra of roof displacement, base shear and structural response quantities of the space frame on compliant base are presented and compared with the fixed base condition. Results indicate that the incorporation of soil flexibility is required for the realistic estimate of structural seismic response especially for single storey structures resting on very soft soil. Copyright © 2013 Techno-Press, Ltd.
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    Seismic behavior of rc framed shear wall buildings as per is 1893 and IBC provisions
    (Techno-Press, 2015) Jayalekshmi, B.R.; Chinmayi, H.K.
    Usually the analyses of structures are carried out by assuming the base of structures to be fixed. However, the soil beneath foundation alters the earthquake loading and varies the response of structure. Hence, it is not realistic to analyze structures by considering it to be fixed. The importance of soil-structure interaction was realized from the past failures of massive structures by neglecting the effect of soil in seismic analysis. The analysis of massive structures requires soil flexibility to be considered to avoid failure and ensure safety. Present study, considers the seismic behavior of multi-storey reinforced concrete narrow and wide buildings of various heights with and without shear wall supported on raft foundation incorporating the effect of soil flexibility. Analysis of the three dimensional models of six different shear wall positions founded on four different soils has been carried out using finite element software LS DYNA. The study investigates the differences in spectral acceleration coefficient (Sa/g), base shear and storey shear obtained following the seismic provisions of Indian standard code IS: 1893 (2002) (IS) and International building code IBC: 2012 (IBC). The base shear values obtained as per IBC provisions are higher than IS values. © 2015 Techno-Press, Ltd.
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    Soil–Structure Interaction Effect on Seismic Force Evaluation of RC Framed Buildings with Various Shapes of Shear Wall: As Per IS 1893 and IBC
    (Springer India sanjiv.goswami@springer.co.in, 2015) Jayalekshmi, B.R.; Chinmayi, H.K.
    Behaviour of a structure is altered by the interaction amid the structure, foundation and the soil medium below the foundation. This mutual dependent behaviour of structure and soil is called as soil–structure interaction (SSI). Hence, it is not realistic to analyse a structure as per conventional structural design practice which considers the base to be fixed. Comparative study on seismic provisions of Indian seismic code, IS 1893:2002 (IS) and International building code IBC:2006 (IBC) is carried out in present study to look into the effect of soil flexibility on variation in natural period, spectral acceleration coefficient, base shear and storey shear. Multi-storey reinforced concrete framed buildings of varying height with various shapes of shear walls over raft foundation were considered. Analysis of 3D SSI models with three different shear wall shapes founded on four different soil types which are classified based on shear wave velocity has been carried out using finite element software LS DYNA. Study shows the significant effects of SSI in altering the seismic response of structure. It also shows that the base shear obtained as per IBC are higher than the IS values and the corrugated shape of shear wall experience the lowest base shear compared to cylindrical and rectangular shape shear walls for buildings with aspect ratio below 3. © 2014, Indian Geotechnical Society.
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    Seismic force evaluation of RC shear wall buildings as per international codes
    (Techno Press technop2@chollian.net, 2016) Jayalekshmi, B.R.; Chinmayi, H.K.
    Seismic codes are the best available guidance on how structures should be designed and constructed to ensure adequate resistance to seismic forces during earthquakes. Seismic provisions of Indian standard code, International building code and European code are applied for buildings with ordinary moment resisting frames and reinforced shear walls at various locations considering the effect of site soil conditions. The study investigates the differences in spectral acceleration coefficient (Sa/g), base shear and storey shear obtained following the seismic provisions in different codes in the analysis of these buildings. Study shows that the provision of shear walls at core in low rise buildings and at all the four corners in high rise buildings gives the least value of base shear. © 2016 Techno-Press, Ltd.
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    Dynamic soil-structure interaction analysis of RC framed building with various positions of shear walls
    (CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2016) Chinmayi, H.K.; Jayalekshmi, B.R.
    In the present study, a three-dimensional dynamic soil-structure interaction analysis of symmetric buildings in time domain is performed using IS spectrum ground motion record corresponding to zone III to evaluate the dynamic response of structure-foundation-soil system. Three types of shear wall buildings of aspect ratio 1, 1.5, 2, 3 and 4 categorized based on the shear wall locations were considered in conjunction with four types of soil of shear wave velocities ranging from 150m/s to 1200 m/s, symbolizing soil classes B, C, D and E of FEMA-356: 2000. Integrated structure-foundation-soil systems were analyzed using commercial finite element software LSDYNA, based on direct method of soil-structure interaction (SSI) assuming linear elastic behavior. The study shows considerable variation in dynamic characteristics and structural seismic response of the structure due to the incorporation of the effect of flexibility of soil and position of shear walls. Tall buildings with shear walls placed at the exterior corners experience the least base shear. © 2016 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.