Seismic re-qualification of an underground RCC duct

The present paper deals with the re-evaluation of design stresses and assessment of safety margins available for an underground RCC ventilation duct. For stress analysis, a 2-D mathematical model has been adopted to represent the structure appropriately. The structure has been analyzed for both static and seismic loads. The seismic analysis has been carried out for site-specific response spectra. The design checks have been performed using available international standards and accordingly the safety margins have been evaluated. The structure has been found to possess sufficient safety margin under all the postulated design loadings. The seismic reassessment methodology conforms to the available international standards. (authors)