Indeed past research showed that large-diameter reinforcing steel appeared to be weaker under fatigue loading conditions. Therefore, in some standards the stress range for testing fatigue of steel bars are reduced for increasing bar size for the same reason.

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In BS4449:1997 it species a re-bend test of steel reinforcement where
reinforcing steel is bent 45^o at 100^oC for an hour and then bent back by 23^o.

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It is not uncommon that steel reinforcement is bent prior to installation into concrete structure. However, upon bending process steel reinforcement may fracture owing to the following reasons:

(i) The ribs on steel bars serve as location of stress concentration which is a potential weak point for fracturing.
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For too much reinforcement to be incorporated in concrete structures, the reinforcement bars are sometimes groups because:

(i) It facilitates placing of fresh concrete with more space available;
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Acetylene gas is commonly used for gas welding because of its simplicity in production and transportation and its ability to achieve high temperature in combustion (e.g. around 5,000^o F).

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