MODEL SEISMIC DESIGN GUIDELINES FOR THERMAL POWER PLANT STEEL BUILDINGS

Abstract

Thermal power plant is used to generate electric energy from thermal energy. Thermal power generation is almost 70% of the total power generation in India. Safety of the thermal power plant should be ensured against all natural hazards including earthquakes. Steel is the most commonly used construction material for power plant buildings. In India, design of thermal power plant structures are based on conventional methodology but thermal power plant buildings are complex structure and require performance assessment to ensure structural behaviour and performance when subjected to earthquake ground motion. In this study, details regarding the evolution of seismic analysis and design of thermal power plant structures are discussed. A typical turbo-generator building, consisting of concentrically braced steel frame structure is considered in this study. The considered building is originally designed according to IS: 800-1984. This building is modelled in SAP2000 Nonlinear software and seismic performance of the building is analysed using the guidelines of ASCE 41 (2017). Nonlinear static (Pushover) and Nonlinear Dynamic (Nonlinear Time History) analyses are performed to estimate the seismic performance of the building at DBE and MCE levels of ground shaking. In India, concentrically braced frames are designed according to conventional design principles, which have various limitations especially, the limited behaviour in nonlinear range and undesirable failure mechanism. Also, there are no design guidelines for Vbracing and inverted V-bracings, though these configurations are commonly used in thermal power plants in India, including the considered building. The relevant Indian standards are compared with the national codes of other countries viz. EC8 and AISC 341, and limitations of the Indian codes are highlighted. The comparison of different codes is used to develop model design guidelines for Indian code. The considered building is redesigned using the recent Indian standards and the proposed model design guidelines. The seismic performance of the originally designed building and redesigned building are compared. Nonlinear static (Pushover) and Nonlinear Dynamic (Nonlinear Time History) analyses are performed to compare the seismic performance at ~ iv ~ MCE levels of ground shaking. The main parameters are evaluated and compared for both the buildings are inter-storey drift, roof displacement and plastic hinge mechanism. The study highlights the inadequacy of the existing building designed according to the old code (IS 800 1984).