What property classes of bolts are covered by IS 3757?

It covers property classes 8.8 and 10.9.

What is the size range for high strength structural bolts per this code?

The code specifies dimensions and requirements for sizes from M16 to M36.

What do the digits in grade 8.8 signify?

The first digit represents 1/100 of the nominal tensile strength (800 N/mm2). The second digit represents 10 times the ratio of yield stress to nominal tensile strength (0.8).

Which code specifies the installation of these bolts?

IS 4000 covers the design and installation of high strength friction grip (HSFG) bolting.

IS 3757

: 1985

High Strength Structural Bolts

CurrentFrequently UsedSpecificationBIMStructural Engineering · Steel and Reinforcement

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This standard specifies the requirements for high strength structural bolts of property classes 8.8 and 10.9 in the size range from M16 to M36. It details dimensions, material specifications, and mechanical testing requirements to ensure the reliability of these fasteners in structural friction-grip and bearing-type connections.

Specifies requirements for high strength structural bolts for use in steel structures.

Quick Reference Values

tensile strength grade 8.8800 MPa

yield strength grade 8.8640 MPa

tensile strength grade 10.91040 MPa

yield strength grade 10.9940 MPa

bolt size rangeM16 to M36

minimum elongation grade 8.812%

Practical Notes

These bolts must be used with matching high strength structural nuts (IS 6623) and hardened washers (IS 6639).

Grade 8.8 implies an ultimate tensile strength of 800 MPa and a yield strength that is 80% of the ultimate (640 MPa).

For the structural design and installation procedures of joints using these bolts, engineers should refer to IS 4000.