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  • Titill er á ensku System identification and seismic analysis of a residential RC building in Kathmandu, Nepal
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  • Útdráttur er á ensku

    This study focuses on experimental system identification, numerical modelling and seismic analysis of an existing reinforced concrete frame building located in Kathmandu, Nepal. System identification is performed with basic theoretical background along with brief introduction to different methods. Demonstrations of the different methods are depicted using response simulated from known simple single degree of freedom (SDOF) and multi degree of freedom (MDOF) systems which are then used for system identification. As a case study, system identification of a four-storied reinforced concrete building located in Kathmandu, Nepal is considered. Two methods of system identification techniques--Welch spectral method and N4SID method--are used for estimation of modal properties. The estimated natural periods of the building are 0.264s and 0.266s for the two fundamental modes of vibration in the two principal directions. The corresponding damping ratios are estimated to be 6.3% and 6.9%. Finite element models with and without soil flexibility are created on ETABS 2017 to study overall differences in the model properties compared to results from system identification. The estimated natural periods are 0.226s and 0.207s for model with rigid soil and 0.275s and 0.259s for model with flexible soil for the first two fundamental modes of vibration in the two principal directions. Study finds that the natural periods of the structure, estimated by finite element model, significantly depend on supporting conditions. When the structure is assumed to be built on rigid soil, the estimated vibration periods are lower than those identified from ambient vibration. While, estimated natural periods for model with flexible soil support are very close to those identified from ambient vibration. This shows the importance of modelling soil flexibility for accurate dynamic characterization of buildings using finite element model.
    Seismic analysis of the building was conducted with strong ground motion recorded during the 25 April 2015 Gorkha Earthquake. Along with recorded ground motion, peak ground acceleration (PGA) scaled elastic response spectra from Eurocode 8 and Indian standards IS 1893 (part 1): 2002 are used for analysis. The structural response of the building with brick infills in terms of base shear, story drift, and structural integrity are checked. The result shows that base shear demand from ground motion is met by code specified response spectra at soft site. However, base shear demand at rock site is considerably higher than that from the soft sites which is underestimated by code specified spectra. Similarly, drift ratio analysis shows that the drift demand when considering soft site ground motion is well within the recommended limits. However, the drift ratio caused by the ground motion recorded at stiff site is two time higher than that depicted by ground motion recorded at soft soil site. Structural verification of selected cross sections was performed using moment curvature diagram (for beam) and P-M interaction diagram (for column). Result of this checking shows that some of the columns on structure were overstressed while the beams performed well during the 25 April Gorkha Earthquake although the ground shaking was not intense.

  • 30.1.2020

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MS thesis_Rajan Dhakal.pdf3.39 MBOpinnHeildartextiPDFSkoða/Opna
Scan_rajand_202001292015_001 (1).pdf46.6 kBLokaðurYfirlýsingPDF