WIND PRESSURE MEASUREMENTS ON HYPERBOLIC PARABOLOID CIRCULAR ROOF MODELS

Abstract

Various types of roofs are used now a days. Cable roofs are one of them. These roofs have a wide field of application as they have been successfully used to cover different buildings having large or small spans. Experience has shown that cable roof structures have considerable economical, structural and architectural potential. For the cable roofs wind load is a major load, hence its accurate determination is a necessity. Codal provisions are applicable to more common types of buildings, whereas roofs like the hyperbolic paraboloid roof which are not in common use are not covered by the codes. No study on wind pressures has been reported on hyperbolic paraboloid circular roofs. A limited study on one such roof having rise to span ratio of 0.04 has been carried out in this thesis for partly built terrain (Category III of IS1875 Draft Code). An industrial wind tunnel of 2.10 m x.2.15 m cross-section was used and pressure measurements were taken on a simulated roof model of 80 cm diameter excluding a 2.5 cm wide beam provided at the periphery. The wind directions and also the percentage of openings have been varied. The outer surface of the roof is seen to have suction in all cases whereas the inner surface has suction on windward side and in most cases pressure on the leeward side. Very high suctions are localised on the windward side near the edge of the roof and steeply reduce to the average values