Abstract
A Corrugated doubly curved sea shell form Concrete Structure of 70 mm thickness is functioning for the past 21 years, with good performance in an institutional building entrance hall of size 30m x 30m. The shell having only boundary beam; sloping to one diagonal corner at + 5 m level, the adjacent two opposite diagonal corners at +7 m level and the peak corner is at + 9 m level, supported by columns and footings are resting on rock. The designer has not taken care for thermal resistance performance and not checked for earth quake, and there was no maintenance except periodical cement based whitewash. But, it has performed well in an earthquake of Richter magnitude 4.0 and performing well for the climatic temperature variations ranging from 19◦C to 44◦C during the 21 years of life span. Vertical micro cracks were noticed in the boundary beams. Roof Shell is fixed with the boundary beams. The roof top surface is fixed with weathering ceramic tiles of size 25 mm x 25 mm bonded using tile bond branded chemical adhesive, has opened bonding in a period of five years in the higher deformation area. Hence, the observation was started by performance based health monitoring. Suitable smart materials were applied for surface skin coat to take care of the positive and negative stress-strains and deformations due to temperature variations. The static and dynamic stability against overturning, sliding and gravity forces is ensured adequate. The integral action of the system and the Elastic and Inelastic ductile behaviour of the shell are observed to be higher.
Highlights
Maintenance of concrete shell roof structure is highly important
The shell having only boundary beam; sloping to one diagonal corner at + 5 m level, the adjacent two opposite diagonal corners at +7 m level and the peak corner is at + 9 m level, supported by columns and footings are resting on rock
The stability in the system is found perfect. the upper ip of the column supporting the boundary beams displace outward due to thermal expansion and reset to its original position on contraction since the temperature strain is very less, the structural and architectural elements are not subjected to distress or damage, but the roof it is square in plan with large spam of 30m x 30mx 0.01m it is subjected to repeated temperature expansion in deny and contraction in might with various climate conditions from summer to winter in this tropical climate location
Summary
Maintenance of concrete shell roof structure is highly important. Placing and compacting stiff concrete in curves is difficult. It causes durability in addition temperature expansion and construction problem is severe. Non structures cracks are formed due to the above said problems. Since shell is this corrosion and diteration problems are caused and it is continuous and progressive. Our problem is a corrugated doubly curved shell form concrete roof structure unit in the entrance hall This paper presents the assessment, repair over maintenance of the above said shell roof as per the NBC2016
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