www.sefindia.org

[Dr. N. Subramanian]

DON'T INCLUDE A CLAUSE ON DESIGN LIFE OF STRUCTURES IN IS 456


I feel that we should not include a clause in IS 456 which says for the building to have a life of 50/75/100 years we need to do such and such things.  This will result in the client suing the practicing engineers, and some may even go to jail. That is the reason even in ASCE or ACI there is no clause on Design Life of Structures. Also life is dependent not only the design, but also the use of proper materials, maintenance, etc.


Unfortunately, BIS is having Professors, and persons from research institutes like SERC, CBRI, etc., or top level engineers,  who do not do actual designs and hence many not know the implications of such a clause.


Also the codes should be simple and not complicated. Already students are not opting for Civil Engineers. If we make things complicated, there will not be Civil Engineers in the future. Please do not think that whatever you do for research should find a place in the codes. If it is very important, give a table or chart, which is easy to apply.


I sincerely feel that the current codes have enough information and the problem is only in the implementation. Many  failures occur periodically in India (even in major constructions like Bridges) due to mistakes done at site. It is urgent to pass rules to have only educated and experienced engineers at site and also train site engineers on mix design, importance of water cement ratio, where to provide more ties or lapping in columns, joint reinforcement, etc.


As done in Singapore, we should have boards in floors about the maximum live load for which it is designed and also have compulsory maintenance.


Dr. N. Subramanian

[vikram.jeet]

Life expectancy of a structure is dependent on many factors , and merely predicting structure longevity in isolation will create confusion .  Very rightly pointed out by Dr NS Sir that such inclusion in IS 456 needs to be discouraged .

Civil engineering is not a preferred option now a days . Structural engineering is seemed as very hard and tough . Simplification of subject makes it more popular with many takers , but it is seen that researchers on structural engg have adopted different  approach , making Revisions more and more complicated .

Just concluding on a joking note that  SIMPLICITY IS THE BEST CITY IN THE WORLD .

[sspawar]

Dear Sefians/Seniors

IS 456 Clause speaks about, Design Life as follows:

8. DURABILITY OF CONCRETE

8.1. General
A durable concrete is one that performs satisfactorily in the working environment during its anticipated exposure conditions during service. The materials and mix proportions specified and used should be such as to maintain its integrity and, if applicable, to protect embedded metal from corrosion.

8.1.1 One of the main characteristics influencing the durability of concrete is its permeability to the ingress of water, oxygen, carbon dioxide. chloride, sulphate and other potentially deleterious substances. Impermeability is governed by the constituents and workmanship used in making the concrete. With normal-weight aggregates 2116 818/07-4.. 17 a suitably low permeability is achieved by having an adequate cement content sufficiently low free water/ cement ratio, by ensuring complete compaction of the concrete and by adequate curing. The factors influencing durability include:

a) the environment;
b) the cover to embedded steel;
c) the type and quality of constituent materials;
d) the cement content and water/cement ratio of the concrete;
e) workmanship, to obtain full compaction and efficient curing; and
f) the shape and size of the member.

The degree of exposure anticipated for the concrete during its service life together with other relevant factors relating to mix composition. workmanship. design and detailing should be considered. The concrete mix to provide adequate durability under these conditions should be chosen taking account of the accuracy of current testing regimes for control and compliance as described in this standard.
.............
Regards