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[rupen]

Dear Sri Kadam:



You are absolutely right in saying bar bending means plastic deformation at
the bend. I would like to extend this discussion.



Generally, the bending radius recommended is arrived at through extensive
experimentation for different bar diameters. The minimum radius is
recommended to prevent the extreme fibers of the bars from being stretched
far beyond the yield point (plastic deformation), or, being stretched too
close to the rupture strain. In other words, sharp bending may cause
fracture of the outer fibers of the bar during bending itself. Thus, in
essence, it is a way to preserve some capacity of the material to be
strained later under the external loads. So, it has its effect on the
strength of the structure also.



Further, now with TMT bars becoming common in use, is it okay to continue to
use the recommended bending radius (originally developed for normal steel
bars), or are these numbers already validated through experiments for TMT
bars? This question arises because the TMT bar is now a non-homogenous
cross-section with a softer core, as against the previous bars that are
homogenous across the cross section.



With regards..

Rupen Goswami

IIT Kanpur





-----Original Message-----
From: p_kadam@vsnl.com [mailto:p_kadam@vsnl.com]
Sent: Saturday, 09 July, 2005 03:18 PM
Subject: [Econf] [Econf] Bending of bars





Dear all,



What is the effect(qualitative/quantitative) of sharp bending(bending radius
being smaller than recommended)?As such bar bending is a plastic
deformation.How does it affect the strength?



regards,



P Kadam

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