What is the factor of safety to be used for designing the posts?

A factor of safety of 2.5 should be applied to the ultimate stress of the timber species used for transverse loads (Clause 4.3.1.2).

What kind of timber can be used?

Recommended structural timber species as listed in the code (e.g., Sal, Teak, Deodar), which must be properly seasoned and treated (Clause 3.1 & Table 1).

What is the maximum voltage line for which these posts can be used?

These posts are intended for low and medium voltage lines up to and including 11 kV (Clause 1.1).

What are the key requirements for nailing?

Nails should be common wire nails as per IS 723. Minimum end distance is 12d, edge distance is 6d, and spacing along the grain is 10d, where 'd' is nail diameter (Clause 5.4.1).

IS 7683

: 1975

Code of practice for design, fabrication and maintenance of nail-jointed timber posts from small dimensional timber for overhead electric distribution lines for low voltage

CurrentSpecializedCode of PracticeStructural Engineering · Building Construction Practices incl. Painting, Varnishing

Download PDF BIS Portal Google

This standard provides guidelines for the design, fabrication, and maintenance of nail-jointed timber posts. These posts are constructed from smaller, readily available pieces of timber and are intended for use as supports for low-voltage overhead electrical distribution lines, offering a cost-effective solution particularly for rural areas.

Code of practice for design, fabrication and maintenance of nail-jointed timber posts from small dimensional timber for overhead electric distribution lines for low voltage

Quick Reference Values

Applicable VoltageUp to and including 11 kV lines

Factor of Safety on Ultimate Stress2.5

Minimum Nail End Distance12 times nail diameter (12d)

Minimum Nail Edge Distance6 times nail diameter (6d)

Minimum Nail Spacing (parallel to grain)10 times nail diameter (10d)

Practical Notes

Proper chemical treatment (preservation) of timber as per IS 401 is critical to ensure long-term durability and prevent failure due to rot or insect attack.

Adherence to specified nailing patterns and minimum spacing is essential for the structural integrity of the joints, as this is where stresses are concentrated.

This construction method is a viable alternative to single solid poles, especially in regions where large-section timber is scarce or expensive.