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IS 800 draft comments

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Joined: 26 Jan 2003
Posts: 63

PostPosted: Wed Oct 08, 2003 9:04 pm    Post subject: IS 800 draft comments Reply with quote

Dear all,

Following are some thoughts on the new draft of IS 800:


I strongly recommend an ELABORATE subject index. That’s what sets it apart as a world class code. It makes it so much easier to use. This hard work is well worth it.

Please restrict the use of the word “should” in the code. It becomes difficult to implement. Use of “shall’ or “must” is preferred.

Just referring to “specialist literature” to the designer leaves him out in the cold. Particular references should be given (and when possible particular extracts given in footnotes or commentary).

Publication of a commentary along with this code is of utmost importance. See AISC or ACI formats. Our code language attempts at places to explain parts that normally should be given in the commentary. This will also make for simpler reading and accessing information.

Composite concrete/steel design, which is one thing that makes steel economically feasable, has been entirely left out of the code. Ironically it does find a brief mention in appendix D regarding damping effects for floor vibrations.

Very little attention has been paid to earthquake (ductile) connection design. Even though earthquake standards (IS 1893-2002 etc.) have been mentioned yet nothing has been said about ductility—refer lessons lessons learnt from Northridge earthquake.

There is a lot of discussion about steel plate shear walls in AISC recently. Any chances of those provisions being adopted in IS?

“Wide flange” shapes are now beginning to be manufactured in India—any impact on any design procedures or figures & tables (Appendix I) shown in the code?

Particular Clauses:

3.5.4. What about combination of blast load? Also definition of blast (shock spectra etc.)? Is Accidental loading same as blast load (table 5.1)? If so why not keep the same terminology? Also see 3.5.6.—quantify or supply equations to calculate “bumper impact” load or refer to particular references. These kinds of issues are big time-takers in design offices.

How about rain load (not to be confused with ponding)—see IBC? Usually an alternate drainage path (in the form of a direct spout that is not prone to clogging) is provided that spills the water directly outside. This spout is above the level of the proper drainage. If the regular drainage path is clogged, water will only accumulate to the level of the alternate drainage and no more. However this accumulated water must be accounted for in design. Collapses have been reported when alternate drainage systems have not been provided.

Also Flood load can be incorporated for areas subjected to inundation.

All combinations--with earth pressure and water pressure (as in water tanks etc.) must also be addressed in Table 5.1.

5.2.2 Limit State of vibration (as in floor vibration). Cl. 5.6.2 only advises broadly but gives no specifics. Appendix D should be referenced to from the appropraite places. I have a strong suspicion the character “Ë” is a typo in this electronic version—it is replacing many symbols.(Note this ASCII symbol “Ë” is a "rectangle" in "WORD")

7.5  Does this section also apply to unequal leg single angle struts?

8.6 Instead of giving requirements for thicknesses of web it would be better to present the various limit states for which the design is being checked. That way it is simpler for the designer to understand and has fewer chances of making mistakes.

Also, is there a section that deals with concentrated forces on flanges and webs—limit states of flange local bending, Web local yielding, web crippling, web sidesway buckling, web compression buckling etc.?

8.8 Design rules of box girder should be more explicit—perhaps refer to other parts of the code when appropriate (like b/t ratios etc.). Also it may not be practical to put additional horizontal stiffeners in box girders referred to by 8.7.13 via 8.8—is that really the intent.

10.4.7 Prying forces cannot be developed for bolts with prestress for the “T” section shown

Ch 10 & Appendix G: Design of the connections such as end-plate connections, continuity plate & doubler plate design procedures are also not covered.

Appendix D:     I believe the heel drop impact test is no longer used as a criterion for floor vibration—especially where floors are very light. For one it is skewed even by the added mass of the people witnessing the test. There has been far more research into this topic. Code writers should try to incorporate the state of the art information. Prof. T.M. Murray’s work has been well recognised in this area (refer AISC web site and search for floor vibrations). Floors subject to aerobic dancing should be very much within the scope of the code & not excluded.

Warm regards,
Vipul Ahuja
(Life Member INSDAG)

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