An investigation into the analysis of innovative slit reinforced concrete shafts design in elevated water tanks in seismic regions

Elevated water tanks are used within water distribution facilities in order to provide storage and necessary pressure in water network systems. During the occurrence of a severe seismic event, the failure or severe damages in the reinforced concrete shaft could result in the total collapse of the structure. In a reinforced concrete shaft, plastic hinge formation only occurs at the base of the shaft and nonlinear resources of the rest of the shaft remains unexploited. This research presents an innovative technique for the assembly of shafts for elevated water tanks, using the slits in the reinforced concrete shaft design, which reduces the stress concentration at the shaft base and distributes stresses uniformly along the height of the shaft. The main aim of this study was to investigate the nonlinear seismic performance of the innovative RC slit shaft of the elevated water tanks by means of a finite element approach. The capacity spectrum and time history analyses were carried out to understand the nonlinear behaviour of the proposed support system. The results revealed that the slit width in the reinforced concrete shaft directly affected the failure mode and stiffness of the elevated water tanks. It was concluded that, with an appropriate design, the conversion of a solid shaft into a slit shaft can significantly increase the ductility of a reinforced concrete shaft, but there would be a slight reduction in the lateral strength. Furthermore, the results revealed that crack propagation was more uniform along the height of the slit shafts in comparison to the solid shaft and the ductility of the shafts increases as the slits become wider. Conclusively, this study showed that introducing the slits in the shaft could result in a significant reduction in the seismic response values of the elevated water tank, resulting in an economical design of the shaft structure and the foundation system.