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Item Effect of diaphragm discontinuity on the seismic response of an rc building(Springer Science and Business Media Deutschland GmbH, 2021) Mable Vas, V.; Nagaraja, P.; Venkataramana, K.Although rigid floor diaphragm is a reasonable assumption for seismic analysis, certain building configurations may exhibit diaphragm flexibility. Detailed investigations have been carried out on modelling of flexible diaphragms compliant with various codes such as ASCE-07 and UBC 1997. Studies have shown that diaphragm flexibility amplifies both the deformation and the shear in the diaphragm. However, additional studies are essential to assess the magnitude of such amplification and to account for it in the design. The methodology is outlined by three major elements such as the choice of building models, the adopted method of analysis and the parameters studied. Buildings with large cut-outs and openings are observed to exhibit flexible behaviour. These models are analysed dynamically using a site-specific response spectrum developed from probabilistic seismic hazard analysis (PSHA) for Mangalore region (a coastal city in Karnataka, Southern India). The analysis is carried out using a G+10 RC building. The effect of percentage of openings in the diaphragm is studied using structural parameters such as storey drift, base shear and storey displacement with the help of ETABS 2015 software, and the optimum shape for these openings in a building plan is finalized. Further, time history analysis is performed over the models, and the results obtained through response spectrum and time history analysis are compared. The study highlights the importance of diaphragm flexibility in determining the seismic response of a building. This flexibility causes significant increase in the building period, which results in reduction in the earthquake-induced base shear. Since the seismic input used for the study was developed for the moderate seismic zone, the outcomes of this investigation are believed to have vast applications. © Springer Nature Singapore Pte Ltd 2021.Item Effectiveness of base isolation using single friction pendulum in plan irregular structures(Springer Science and Business Media Deutschland GmbH, 2021) Sharika, R.; Venkataramana, K.Base isolation is found to be a very efficient earthquake-resistant construction method. When base isolation is introduced, the transfer of large amount of inertia forces is prevented by the moving action of an isolator during an earthquake. The application of base isolator in regular buildings is done from long before, but the usage and effectiveness of base isolation in irregular buildings are a topic which needs more research. In this study, single friction pendulum isolator is used to isolate the buildings and the effectiveness of isolators is discussed in regular as well as plan irregular buildings. Modal analysis and time history analysis using Chi-Chi earthquake accelerogram data is done. Time period obtained from modal analysis and the results of time history analysis, such as base shear, storey acceleration and storey drift of regular, as well as plan irregular buildings are compared. The time period is found to increase significantly and base shear, acceleration and storey drift are decreased significantly with the application of single friction pendulum isolator. Also, the effectiveness of isolator got reduced with the introduction of irregularity in the structure. © Springer Nature Singapore Pte Ltd 2021.Item Seismic Pounding Between Adjacent RC Buildings with Asymmetric Alignment(Springer Science and Business Media Deutschland GmbH, 2021) Ambili, P.; Krishnachandran, V.N.; Venkataramana, K.During earthquakes, adjacent structures may collide with each other due to different dynamic characteristics. When buildings vibrate out-of-phase and the separation gap provided between buildings is not sufficient to accommodate their relative motions, collisions can cause severe damage or even complete collapse of structures, and is known as seismic pounding. In metropolitan cities, due to increased population and land values, buildings have been constructed with inadequate separation distance between them. The seismic oscillations induced in a structure in a block of buildings will be partly restrained in lateral displacements and hence torsional movements are introduced (asymmetric pounding). Two different types of impacts may occur during pounding including floor-to-floor and floor-to-column (inter-storey) collisions. In this paper, the effects of asymmetric (contact asymmetry) pounding on the seismic response of adjacent buildings with symmetric plan and unequal building heights are studied. Time history analysis of adjacent buildings with different pounding cases involving 1, 2 and 3 column pounding is carried out using the software ETABS and the corresponding torsional response is evaluated. The influence of separation gap and floor heights between the adjacent structures on the torsion effect is investigated and the results are compared with no pounding case. © 2021, Springer Nature Switzerland AG.