International Journal of Civil and Structural Engineering Research ISSN 2348-7607 (Online) Vol. 8, Issue 1, pp: (56-61), Month: April 2020 - September 2020, Available at: www.researchpublish.com
EFFECT OF DENSITY ON RATE OF BURNING OF WOOD USED IN FRAME OF FIRE RATED DOORS Anand Nandanwar, Kiran M. C., Narsimhamurthy and Mamatha B. S. Indian Plywood Industries Research and Training Institute IPIRTI, P. B. No 2273, Tumkur road, Bangalore – 560022, India
Abstract: During designing of fire rated doors more importance is given to the door shutter as compared to door frame for achieve given fire rating. On the contrary, it is observed in various events that, even if the fire rated door resists fire, the failure occurs in frame because of wrong selection of wood, resulting in non-conformity or failure of door set for achieving the desired fire rating. This study is carried out to correlate the density of wood used in frames of door shutter assemblies with its rate of burning. Some of the widely used species for frames of fire rated door were selected for the study viz. Red meranti (Shorea acuminata), Sal (Shorea robusta), Birch (Betula pendula), Padauk (Pterocarpus spp.), White Meranti (Shorea spp.). Samples of different densities ranging from density of 412 to 849 Kg/m3 were tested for rate of burning as per Indian standard IS 1734 (1983). The correlation of fire performance/ rate of burning was drawn with respect to density of wood. From the results of the study it is observed that lower rate of burning of wood is observed with denser wood, hence it can be said that fire resistance of wood increases with density. Keywords: fire rating, density, selection criteria, optimization, wood species.
1. INTRODUCTION Wood is one of the most used natural building materials. A number of valuable properties such as low heat conductivity, low bulk density, relatively high strength, amenability to mechanical working etc. makes wood as a famous building material. The often inevitable hazards of fire make wood a very desirable material for further investigation. It is necessary to take great care to adequately reduce the risk of fire. The use of wood as an interior material is strictly controlled by building codes, so it is necessary in the design stage to thoroughly consider the resistance of these materials to fire. Fire Resistance means the ability of a building component to resist fire, while still performing its function. Fire resistance in form of a fire rating, can be applied to a total building element incorporating plywood e.g. fire rated door, wall or roof system. Fire retardant plywood (IS: 5509, 2004) is quite acceptable material used in fire resistance components or structures. While timber is indeed a combustible material, in construction it has significant insulating properties and burns in a slow, predictable and measurable way. These factors see timber perform strongly against fire and give designers the ability to confidently create strong, durable, fire resistant timber constructions. When exposed to the heat of a fire, timber goes through a process of thermal breakdown into combustible gases. During the process, a layer of charcoal forms on the burning surface of the timber and it is this charred layer that is the key contributing factor in timber‟s fire resistance. The layer acts as an insulator protecting the inner core of the timber, making it resist heat penetration and thus burn more slowly ; while the temperature of inner, un-charred core remains low, enabling it to continue to carry its load. Initially the rate of charring is fast but as the char depth increases it provides a stronger protective layer to the timber, slowing the overall combustion rate. The rate at which timber chars varies between species and is predominately dependent on density and moisture content. Since density has a great relationship with the other physical properties of wood, this study focuses on density, the most widely used physical index of wood, to correlate with fire resistance of wood.
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