Comparative study on response of boiler supporting structure designed using structural steel i-columns and concrete filled square steel tubular columns

Abstract

Boiler supporting structure is one of the most important structures employedin any power plant project. A typical boiler supporting structure will be of 100 m height subject to a concentrated load in the range of 15,000-20,000 tonshung from the top. The distributed loads attached to the rest of the portion (i.e. from 0 to 100 m are comparatively less and therefore, this type of structure is typically like an inverted pendulum with huge mass attached at the top. These kinds of structures are highly sensitive to lateral and dynamic loads. In the present day Indian scenario, the boiler supporting structures are designed using huge Plus columns made with two major I-sections in the order of 1.0-1.2 m web depth with a typical web and flange thicknesses in the order of 16-63 mm. As a typical once through supercritical boiler supporting structure consists of around 25-45 columns of such mega size, such structures becomes more expensive in terms of money and fabrication time. In view of optimizing the structural steel usage and to develop an efficient structural system, a theoretical attempt is made in this study through design of such structures using concrete filled square steel tubular column. Typical boiler structure is modeled using structural analysis program and analyzed for various conditions such as various seismic zones, windzones, different load combinations and various section sizes. The story drift of thestructure is estimated at various levels and compared with that of structure made using Plus I-column. Typical cost comparison also made to study the effectiveness of the project. This paper describes the complete analytical procedure along with results and conclusions.