ASSIGNMENT OF CIRCUMFERENTIAL REINFORCEMENT AREA IN REINFORCED CONCRETE RING JACKETS FOR STRENGTHENING THIN-WAIIED SHELLS OVER THE HEIGHT OF CHIMNEYS

Abstract

Chimneys are an integral part of many industrial enterprises. The main structural element of industrial monolithic exhaust stacks is a thin-walled reinforced concrete shell with a thermal insulation layer and internal lining. The study of the influence of flue gas temperature fluctuations on the stress–strain state of ring sections in the thin-walled reinforced concrete shell is highly relevant, as it is directly related to the area of circumferential reinforcement in these sections and its effect on the width of vertical crack openings. The justification of the adequacy of adopting circumferential reinforcement areas is based on regulatory limits for the width of external vertical cracks.

In this article, the author carried out an analysis of the influence of circumferential reinforcement areas of the thin-walled shell of a chimney on the width of vertical crack openings by modelling the structural parameters (variation of shell thickness) of an existing 120 m high chimney of the Kyiv ST-2 at four different flue gas temperature levels.

During long-term operation of chimneys, their structural elements undergo various types of damage, which creates the need for strengthening. A well-proven method is the strengthening of the chimney shaft with additional reinforced concrete circumferential jackets, which can be installed at any height of the chimney. As a result of such strengthening, the overall thickness of the thin-walled reinforced concrete shell increases. Referring to studies of other researchers who carried out strengthening of the 120 m chimney shaft of the Mariupol Iron and Steel Works with a reinforced concrete jacket, the author confirmed his statements regarding the influence of changes in shell wall thickness and circumferential reinforcement area on the width of vertical crack openings.

It is concluded that when specifying circumferential reinforcement areas in reinforced concrete jackets for strengthening monolithic chimneys, it is necessary to take into account both the variations of flue gas temperature differences and the thickness of the thin-walled reinforced concrete shell along the height.