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[pulkitkumar_dungrani]

Clause 8.3.1 of IS1893 Part 4 : 2015 stipulates strength Load combinations for Steel Design. These combination factors are enhanced when compared to those given for RC design (clause 8.3.2) and also those given in IS 800 2007 in Table 4, i.e. load factors of 1.7 & 1.3 are recommended in in place of 1.5 & 1.2 respectively when making the comparison.

One probable reason may be that it mentions these combinations are for  'Plastic Design', however the AMENDMENT NO. 2 JULY 2018 removes the word Plastic Design from Table 2 - Method of Structural Design for Steel, and states just 'Design as per IS800 for steel'. Moreover, IS 800 2007 does not provide criteria for Plastic Design but instead it talks about Plastic Analysis. So this might have instigated this amendment.

Can someone please explain the basis of these enhanced load factors for steel design?
And whether we should consider these combinations while performing Limit State Design as per IS 800 2007 or to follow those provided in IS 800 Table 4?

I have referred the paper 'Review of Critical Design Provisions of IS1893 (Part 4): 2015' by Mrs. Alka richharia-pisal & Mr. Yogesh Pisal but it does not address this topic. Perhaps they might want to shed some light on this topic here in this forum.

I appreciate your support. Thank you.