Galambos, T. V.

Lay, M.

English

Lehigh University: Lehigh Preserve

Lehigh University
Lehigh Preserve
Fritz Laboratory Reports Civil and Environmental Engineering
1963
Discussion of "lateral bracing force of steel i-beams"
by massey, C., Proc. ASCE, Vol. 89, EM3, June
1963, Reprint No. 226 (63-13)
M. Lay
T. V. Galambos
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Recommended Citation
Lay, M. and Galambos, T. V., "Discussion of "lateral bracing force of steel i-beams" by massey, C., Proc. ASCE, Vol. 89, EM3, June 1963,
Reprint No. 226 (63-13)" (1963). Fritz Laboratory Reports. Paper 1428.
http://preserve.lehigh.edu/engr-civil-environmental-fritz-lab-reports/1428
FRITZ ENGHiEERiHG LABORATORY
LEHIGH UNIVERSITY
BETHLEHEM, PENNSYLVANIA
Welded Continuous Frames anel Their Components
DISCUSSION OF TIlE PAPER
"Lateral Bracing Force of Steel X-Seams" by
Campbell Massey. ASCE Proceedings Paper
Noo 3364~ EMO" Vol. 88 •. Decl!mbu ,l 1962.'
by
Maxt>lell GoLay
TbeodoX:-8 V 0 Galambos
Fritz Engineering Laboratory
Lehigh University
BethlGWem" Penna u
April" 1963
t=:". L. l\!?>rzr\ff
~ 05-;1.1 ()
I·
Fritz Engineering Laboratory Report No 0 20SH 0 10
I ' Discussion by Ko GoLay & T" V 0 Galambo&
has fwnd the force required to bold one point of an I beam fixed
against deflections out of the plane in which the beam is heiDg
loaded" There is no re&8gQ wy this force should be synonomous
with the bracing condition required to ensure the adequate structural
performance of that beam., For i!lstance; testa raported elsewhere18
have shown that I beams may dc!liver adequate rotation capacity under
conditions in which the braced points deflect laterally 7/8" in a
13 foot spam" As the author did not present load-deflection curves
for biB tests it would be appreciated if such curves could be given
1n th2 closure to this discussion 0 Plots of moment versus vertical
and horizontal deflection would allow the significance of Mt'" Massey is
teets to be more fully realized"
It also needs to be pointed out that the author's post ...
elastic analysis reprezents a highly idealized situationo A
complete analyBia would also consider the following effects:-
ca.:-O-==__- I3!l* g-
a December 1962 l) by campbell Massey (hoc" Paper 3364)
16aesQIU'ch Assistant, Fritz Engrg 0 Lab 0 9 Civil Engrg 0 Dept" J
Lehigh University 9 Bethlehem" Pa"
17Reae&rch Associate Professor, Fritz Engrs" Lab 0 , Civil Engrg"
Dept,,» Lehigh University" Bethlehem!! Pa"
lS"Experiments on Braced Wiota Flange Beams" by A" T" Ferrara,
G" Co LeQ and To V" Galambos, Fritz Engrg" Lab" Report 205800 9
March, 19630
205'H!"lO
1) Residual Stresseu
2) 810:1&1 bending and twisting dwd.ng the loading sequence
3) The variation of defo~tions and stiffness functions
along the beam
The meglect of residual stressea is valid for a theory applicable to
heat-treated specimens such as the author tested" However» it bas
been ahown10,19 that residual stresses will exert a significant
influence on the lateral buckling behavior of commercial beams and
thus tbe author is not correct in using bi~ reliults to draw conclu-
The stress distribution uaed in Fig" 2 is applicable in
cases of iD"'plane bending &ld problems treating the point of lateral
bifurcation (or buckliag)" The author It s case is an initial c.ieflec-
tioD problem and therefore buckling will ba precluded" Twisting
and lateral deflections will occur from the commencement of loadins
and the &8L1Umj1)li::lon of Fig" 2 will progressively worsen as the load-
iog increas~so
The above points are not intended to indicate that Massey vs
ana.lytiJi~ will necessarily lead to incorr«ect results lJ but rather to
point out that more careful 8tudi~s are required before some of his
1910Inelastic Lateral Buckling of Beam-Colum!MSH by Yo Fukumoto;
Ph"D" Dissertation/) Lehigh Universi.ty/) 1963
·.
"
205B.10 -3-
conclusions can be accepted I> A case ill point· i3 the author 0 s
conclusion on the magnitude of therequiifGd bracing force I> This
force is normally.taken as:
Fb &; 0002 Ff
where Ff 1I9 (area of compression flange) x (yield
stress)
M&saey suggests tlwt this value of 0002 may be too low for beams
proportioned according to Ref 0 13 or Ref. 200 The maximum value of
F'b/Ff from the author's tests is 000039, i}O these do not directly
support his conclusions o The theoretical results presented in
Figs 0 3 and 4 do appcaar to indicate large braci~g forces for
very short beams (in this regard it is noted that the theory
',.
a4.sumes no straino;ahardening).
),
Massey .suggests that a beam designed according to Ref 0 13
would fall into this category of very short beams. It appears here
tliat the author has incorrectly interpreted the bracing recommenda- .
tiona of Refs 0 ·13 and' 20 0 In the former it is recoDIIDended that
. theunbracea' length be 45ry II not the ·full span as interpreted by
Massey. Using the correct length 1l it is seen that the author's
t~mts are for unbraced lengths of 120%')', lOOry 11 60ry and 4Ory , not
for 240ry J 20o-cy, 120ry and 80ry as wa.s stated 0 Since it was a
4bry teat which gave, Fb/Ff Cl 0,,0039 it ifi seen that the tests.:-
actually contradict the author \) $ conclusion" Furthermore l) when
-4-
the theoretical results are viewed in this light, see Figs~ 3 and 4,
the maximum spen rec~ded by Ref ~ 13 'would be 2 x 45ry III 90ry J
Dot 45ry ~ From Fig 0 1+ the value of Fb would be 13 lb 0 whereas
Ff Ill! 1/2" X 1/8" x 31,500 w 1,980 lh o Hence Fb/Ff Cl 0000650 Ali
this latter value is still very mu~b le8~ than the 0 0 0200 recommended,
the wrU:ers Bee little cause for the concern expressed by the author"
20 '~pecification8 for the Design, Fabrication and Erection of
~A.~"'._f-'lI.~,,1! ,.,..'!. ...... ~.1 .e ... ta ~ ...- ~ ~ Ill... ~. ~


Discussion of  lateral bracing force of steel i-beams  by massey, C., Proc. ASCE, Vol. 89, EM3, June 1963, Reprint No. 226 (63-13)

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Discussion of lateral bracing force of steel i-beams by massey, C., Proc. ASCE, Vol. 89, EM3, June 1963, Reprint No. 226 (63-13)

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