The type of timber recommended for constructional purpose, whose modulus of elasticity in bending is above 12.5 kN/mm², is classified as ________ timber.

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SSC JE Civil 9 Oct 2023 Shift 1 Official Paper-I

Answer 1

Concept:

According to IS 399 (1963), the classification of timbers is as follows:

Classification of Timber(based on)	Types
Position	Standing Timber: It means that the living tree.
	Rough Timber: Form a part of the felled tree.
	Lumber: lumber are the logs of timber sown into planks, posts.
Modulus of Elasticity	Group A - Modulus of elasticity in bending above 12.5 kN/mm2
	Group B - Modulus of elasticity in bending above 9.8 kN/mm2 and below 12.5 kN/mm2
	Group C - Modulus of elasticity in bending above 5.6 kN/mm2 and below 9.8 kN/mm2
Availability	Grade X - Most common, 1415 m3 or more per year
	Grade Y - Common, 355 m3 to 1415 m3 per year
	Grade Z - Less common, below 355 m3 per year
Durability	High Durability - Average life of 120 months and over.
	Moderate Durability - Average life of less than 120 months but of 60 months or more.
	Low Durability - Average life of less than 60 months.
Seasoning Characteristics	High Refractory - These are slow and difficult to season free from defects.
	Moderate Refractory - The protection is given against rapid drying.
	Low Refractory - These can be rapidly seasoned free from defects.
Treatability	Easily treatable
	Treatable but complete preservation is not easily obtained.
	Only partially treatable
	Refractory to treatment
	Very refractory to treatment, penetration of preservative being practically nil from the sides and ends.