Numerical investigation on the characteristics of dynamic response and damage of a RC tall chimney considering vertical ground motions

Abstract

Although seismic risk assessment models for structures have become more sophisticated, they have typically disregarded the effects of vertical ground motions (VGMs). Nevertheless, this trend is gradually shifting due to recent recordings and field observations that have demonstrated the potentially destructive effects of high VGMs.In this paper, a nonlinear finite element (FE) model of a 234 m reinforced concrete (RC) chimney is developed, with a focus on investigating its dynamic response and damage characteristics under the effect of VGMs. The results are compared with the case of a combination of horizontal and vertical ground motions (HVGMs). First, a time history analysis (THA) is performed under various VGMs input conditions. The findings reveal that the vertical seismic force increases with the intensity of ground motion. However, the distribution of the seismic force remains unchanged, with the maximum vertical seismic force occurring at 85% of the chimney height. Then, the seismic response of the chimney under HVGMs input conditions is examine, revealing that the maximum vertical seismic force increased by 4%–6%, but its distribution does not change significantly. Furthermore, the effect of the additional mass of the flue is considered, resulting in a significant increase in the vertical seismic force at the suspension points, leading to a change in its distribution. An abrupt increase of about 40% at 1/3 height and an increase of about 45% in the horizontal displacement at the top are observed. The paper also highlights the potential stress concentration and resultants cracks or damage caused by the opening of the chimney barrel.