Study of Post Earthquake Performance of Trestle Supported Water Tank

Abstract

Elevated trestle supported water tanks along with water pipelines are lifeline structures for the community and ought to remain relatively undamaged during any natural calamities. Visual survey of about 20 water tanks constructed by GWSSB has been carry out to find the different types of damages as well as an attempt has been made to find the causes for the observed damages. It has been observed that since these structures are elevated, they are more prone to effect of atmospheric weathering action, which in turn affects the long term performance of such structures. Main distresses observed in such type of structures are corrosion of reinforcement of brace beams and columns which generally occurs due to improper cover, cracks at beam column joint, segregations and spalling of concrete due to improper workmanship, severe damages in staircase etc. A case study of an elevated water tank situated at Kharaghoda village, Surendranager is presented here. It has been observed that this tank is distressed due to weathering and corrosion effect. Analysis of the tank is carried out with draft codal provisions for elevated water tank. The comparisons assessment of the tank using draft code and current code of earthquake analysis is evaluated in terms of base shear and base moment. Non destructive testing such as Rebound hammer, Ultra Pulse Velocity, Cover meter in addition to pH meter and Carbonation has been carried out. Discussion on test procedures, analysis of results and conclusions for above tests also has been included. Finally two major alternatives i.e. Shotcreting and Jacketing for repair and retrofitting of the tank have been suggested.