Seismic Evaluation and Retrofitting of Existing Reinforced Concrete Water Tank Staging System”

Abstract

The Indian standard “Criteria for Earthquake Resistant Design of Structures: IS 1893:2002” has been revised. The seismic zone factors have been changed. Response spectra are now specified for 03 types of founding soil strata & a response reduction factor has been introduced. Elevated water tanks are vulnerable to earthquakes, owing to large mass concentrated at the top of relatively slender supporting systems. Existing elevated water tanks in India designed using IS 1893:1984 needs to be checked for safety as per revised code (IS 1893-2002) by carrying out static analysis. It is observed that the structure is unsafe due to under estimation of seismic load as per old code provisions. Retrofit measures such as additional structural elements and passive devices like viscous and friction dampers are modelled and structure analysed again to check for compliance with the revised code. Keywords: Seismic zone factors, Water tank, Dynamic properties, NDT test, Retrofit, Static Analysis by SAP.