The Structural Engineer > Archive > Volume 4 (1926) > Issues > Issue 12 > Correspondence on Strength of Steel
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Correspondence on Strength of Steel

To the Editor of The Structural Engineer. Sir, I have had occasion quite recently, to discuss with the Manager of a small engineering works, the matter of welding mild steel rods and upon asking him "Can you guarantee your weld?" he retorted by asking "Can you guarantee your steel?" Although the steel rods I was about to have welded were of British manufactsure I could not, of course, guarantee them, nor did I think that, there was any particular merit in the question, until I got a rude shock from my friend (who, by the way, comes from Glasgow, and has had a large experience in engineering and workshop practice) when he explained to me his experience at various times, and even within the past few weeks, of the behaviour of mild steel rods. My reference to welding applies to open forge-welding and rods mean rods foreinforced concrete purposes. I have always held the view that a weld, however carefully forged, could not be as strong as an original rolled rod, arguing by analogy, that, a broken limb, however well set, could not equal in efficiency and strength, the unbroken limb. My concern is not with the strength of welds, but, in arguing the merit and de-merits of welds, my friend was able to point out to me the extraordinary behaviour of round mild steel rods when being bent into truss units. Imagine an ordinary truss, some 25 ft. long of 1 in. section, which, after being bent had become slightly distorted, a very frequent happening. The truss was placed upon an anvil and three blows struck with a 14 lb. sledge-hammer. At the third blow, struck at one end of the rod, the bent portion at the other end dropped off. The diagram shows the relative position of the blow, which was merely a moderate one, and the portion of the rod that dropped off. I was shown the piece (12 in. long) that dropped off, and my friend put it through a severe practical test.