Faculty Publications

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    Probabilistic Analysis of RC Buildings Based on Incremental Dynamic Analysis
    (Institute of Physics, 2023) Mathews, M.; Jayalekshmi, B.R.; Venkataramana, K.
    Earthquake is a natural disaster that can induce immense damage to properties and human lives. Fragility curve, defined as the probability of reaching or exceeding a specific damage state under an earthquake excitation, provides a prediction of damage that may occur during an earthquake. Incremental Dynamic Analysis Curve (IDA curve) developed from Incremental Dynamic analysis can be considered as the initial step of fragility curve development. The present study summarises the development of IDA curve for a RC building considering maximum roof displacement and storey drift as Damage Measure (DM) and peak ground acceleration as Intensity Measure (IM). The fragility curves developed using incremental dynamic analysis provide an overview of the probability of exceedance of damage limits in an existing building when acted upon by different levels of earthquake excitations and the performance level can be improved by incorporating appropriate design changes. © Published under licence by IOP Publishing Ltd.
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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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    Vulnerability Assessment of RC Building by Incremental Dynamic Analysis Approach
    (Springer Science and Business Media Deutschland GmbH, 2024) Rawal, S.N.; Mathews, M.; Jayalekshmi, B.R.
    Vulnerability assessment of existing RC building subjected to earthquake excitations can be used as an effective tool for understanding the seismic response of building. Incremental dynamic analysis (IDA) offers an efficient method to nonlinear dynamic structural analyses for accurate estimation of seismic performance of structures under earthquake ground motions. This study summarizes the evaluation of fragility curves for a reinforced concrete frame structure using incremental dynamic analysis approach considering variability of ground motion. A detailed review of literature on incremental dynamic analysis and fragility curve is presented. The detailed model of two-story RC building is generated, and nonlinear time history analysis is performed to assess the performance under seismic excitation. The variation in ground motion is considered by using three sets of earthquake data to evaluate response of the structure and IDA curves are obtained. These curves are then operated by fragility evaluation procedure to obtain fragility curves at different damage limit states. From the fragility curves, prediction on the probability of exceedance of different damage states under seismic excitations is made. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
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    Site specific fragility modification factor for mid-rise RC buildings based on plastic energy dissipation
    (Techno-Press, 2024) Mathews, M.; Jayalekshmi, B.R.; Venkataramana, K.
    The performance of reinforced concrete buildings subjected to earthquake excitations depends on the structural behaviour of the superstructure as well as the type of foundation and the properties of soil on which the structure is founded. The consideration of the effects due to the interaction between the structure and soil-foundation alters the seismic response of reinforced concrete buildings subjected to earthquake motion. Evaluation of the structural response of buildings for quantitative assessment of the seismic fragility has been a demanding problem for the engineers. Present research deals with development of fragility curve for building specific vulnerability assessment based on different damage parameters considering the effect of soil-structure interaction. Incremental Dynamic Analysis of fixed base and flexible base RC building models founded on different soil conditions was conducted using finite element software. Three sets of fragility curves were developed with maximum roof displacement, inter storey drift and plastic energy dissipated as engineering demand parameters. The results indicated an increase in the likelihood of exceeding various damage limits by 10-40% for flexible base condition with soft soil profiles. Fragility curve based on energy dissipated showed a higher probability of exceedance for collapse prevention damage limit whereas for lower damage states, conventional methods showed higher probability of exceedance. With plastic energy dissipated as engineering demand parameter, it is possible to track down the intensity of earthquake at which the plastic deformation starts, thereby providing an accurate vulnerability assessment of the structure. Fragility modification factors that enable the transformation of existing fragility curves to account for Soil-Structure Interaction effects based on different damage measures are proposed for different soil conditions to facilitate a congenial vulnerability assessment for buildings with flexible base conditions. © 2024 Techno-Press, Ltd.
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    Fragility curve modifiers for dual-frame systems in various site classes incorporating nonlinear SSI effects
    (Taylor and Francis Ltd., 2025) Mathews, M.; Jayalekshmi, B.R.; Venkataramana, K.
    The seismic response of reinforced concrete buildings depends on the interaction between the superstructure, foundation type and soil properties, making accurate fragility assessment a complex engineering challenge. This study focuses on constructing fragility curves specific to building vulnerability assessment by incorporating various damage parameters that account for soil–structure interaction effects. Using finite element analysis software, Incremental Dynamic Analysis was performed on RC building models with both fixed and flexible bases founded on varying soil conditions. Fragility curves were developed using three engineering demand parameters: maximum roof displacement, inter-storey drift and plastic energy dissipation. Findings reveal that maximum roof displacement parameter consistently yields the highest probabilities of exceedance, reaching up to 90–100% for soft soil at a PGA of 0.3 g, identifying it as the most conservative measure, while plastic energy dissipation displays the lowest probabilities (10–50% across all soil types), indicating its limitations in capturing deformation demands. To streamline vulnerability assessment for buildings incorporating the effect of supporting soil stratum, fragility modification factors are proposed to efficiently adjust existing fragility curves for incorporating SSI effects based on different damage measures and soil conditions, providing a comprehensive approach to efficient vulnerability analysis. © 2025 Korea Institute for Structural Maintenance and Inspection.