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prabh SEFI Member
Joined: 26 Jan 2003 Posts: 7
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Posted: Tue Oct 07, 2003 4:03 pm Post subject: E-conference on IS:800 Draft (LSM) |
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Dear Structural Engineers,
I would like to write the following observations on the draft code which may be considered by the code committee:
1. Clause 3.1.2.2 in page 28 may be reworded as follows:
“Where the Limit State Method cannot be conveniently adopted, Working Stress Method (Section 11) shall be used.
2. The Partial Safety Factor of 1.05 for load cases with crane (CL), given in Table 5.1 in page 48, is very small indeed. This may be a typographical error. In industrial type structures, dead and live loads on roof etc. are usually very small, and crane loads combined with wind load are critical in the structural design in most cases. This Partial Safety Factor needs to be revised to 1.5.
3. In Table 5.3 in page 51, the types of cladding mentioned need to be defined, particularly with reference to the types of cladding used in India.
4. The figures shown in page 70 for the lacing details of columns are inadequate. The code should show all the figures (Figs. 4A to 4D) given in the National Building Code of India 1983, Group 2, Part VI Section 6 Structural Steel , for more clarity.
5. Section 10 deals with connections between steel sections only. Clause G.5.2. in pages 197 and 198 on holding down bolts is also very sketchy. These do not deal with various types connections of steel sections to concrete, such as with expanding type bolts and insert plates with anchors, which are used in large numbers in industrial type structures. In most design offices, usually two separate groups operate for the design of steel and concrete structures. This practice has become more universal. The steel designer considers only the strength of steel while designing the end details of steel members and usually does not bother about the strength of the concrete to resist the end loads. The concrete designer designs the supporting concrete members only for the loads furnished by the steel designer, usually not verifying the design of steel end details given by the steel designer. In these circumstances, sometimes failures do occur in concrete at the interface of the connections. These connections are a specialised subject on its own, and the latest literature on the subject may not be available to many structural designers in India. Hence, a guideline should be given in the code on this important subject.
I trust that the above observations will be useful for inclusion in the final copy of IS:800.
Yours truly,
N. Prabhakar Chartered Structural Engineer 404 Star View Aptmnts Sion Trombay Road at Chembur Mumbai 71
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