To obtain a copy of a specific publication, users should contact the publication's publisher directly.
Abstract
As part of a New Zealand government aid program to tropical cyclone ravaged Western Samoa in 1992, the writers evaluated the high failure rate of single story timber framed classroom. One architectural feature of the classroom was the extension of the low pitched gable corrugated iron roof along one of the nine meter long walls to form a verandah 2.3 meters wide. Field studies of the damaged buildings indicated a number of points of failure. One common point of failure was at the connections between the roof trusses and walls. Estimated uplift wind loads on the verandah roof were largest when the wind direction was toward the verandah side of the building. Codes indicated a combined effect of positive upward wind pressure on the underside and negative upward wind pressures above the verandah roof with such a wind direction. This positive wind pressure on the underside was due to partial stagnation of the approaching air flow trapped under the extended verandah roof. Many buildings built in tropical regions during the colonial era had a provision for air flow between the roof and room ceilings to improve indoor thermal comfort. Such roofs were referrred to as parasol roofs. Relatively inexpensive reconfiguration of the roof trusses can create a parasol roof on Western Samoan classrooms. Air flow through the parasol roof space in a wind tunnel model reduced critical wind pressures on the verandah roof. Results of boundary layer wind tunnel studies are provided in graphical form in the paper. These results show clearly how changes to architectural features, such as parasol roofs, can change wind loads. Further studies are warranted.
As part of a New Zealand government aid program to tropical cyclone ravaged Western Samoa in 1992, the writers evaluated the high failure rate of single story timber framed classroom. One architectural feature of the classroom was the extension of the low pitched gable corrugated iron roof along one of the nine meter long walls to form a verandah 2.3 meters wide. Field studies of the damaged buildings indicated a number of points of failure. One common point of failure was at the connections between the roof trusses and walls. Estimated uplift wind loads on the verandah roof were largest when the wind direction was toward the verandah side of the building. Codes indicated a combined effect of positive upward wind pressure on the underside and negative upward wind pressures above the verandah roof with such a wind direction. This positive wind pressure on the underside was due to partial stagnation of the approaching air flow trapped under the extended verandah roof. Many buildings built in tropical regions during the colonial era had a provision for air flow between the roof and room ceilings to improve indoor thermal comfort. Such roofs were referrred to as parasol roofs. Relatively inexpensive reconfiguration of the roof trusses can create a parasol roof on Western Samoan classrooms. Air flow through the parasol roof space in a wind tunnel model reduced critical wind pressures on the verandah roof. Results of boundary layer wind tunnel studies are provided in graphical form in the paper. These results show clearly how changes to architectural features, such as parasol roofs, can change wind loads. Further studies are warranted.
Date
6/1993
6/1993
Author(s)
R Aynsley; A Lynch; I Johnstone
R Aynsley; A Lynch; I Johnstone
Page(s)
77-85
77-85
Keyword(s)
wind tunnel; architectural; wind load; single story classroom; roof truss failure; wind uplift; parasol roof
wind tunnel; architectural; wind load; single story classroom; roof truss failure; wind uplift; parasol roof