I...

"

S TEE L NTERCHANGE

• Steel I nterchange is an open forum for Modern Steel

Constructio'l readers to exchange useful and practical profes·
sional ideas and information on all phases of steel bui lding and
bridge construction. Opinions a nd suggestions are welcome on
any subject covered in this magazine. If you have a question or
problem that your fellow readers might help you to solve, please
Answers and/or questions should be typewritten and double·
spaced. Submittals that have been prepared by word· processing
a re appreciated on com pu ter diskette (either as a Wordperfect
file or in ASCII format).
The opin ions expressed in SteelIllterchange do not necessar-
ily represent an official position of the Ame ri ca n Institute of
forward it to Modem Steel Construction. At the same time, feel Steel Construction, Inc. a nd have not been reviewed. It is recog-
free to respond to any of the questions that you have read here. nized that the design of structures is within the scope and
Please send t hem to: expertise of a competent licensed structural engineer, architect
Steel Interchange or other licensed professiona l for the application of principals to
Modern Steel Construction a particular structure.
One East Wacker Dr., Suite 3100 Information on ordering AISC publi catio ns me ntioned in
Chicago, IL 60601-2001 this article can be obta ined by callin g AI SC at 800/644-2400.

The following r esponses from previous Steel ments of column, respectively, can be attained by
Interchange columns have been received: solving the equations proposed by J.P. Anderson
and J .H . Wodward (AISC Engineering Journal,
In a partially cover-plated column, how October 1972, pp. 157 - 166) or by entering Table 1
would you analyze the column for governing (included in Appendix B) with the values of 1/11,
IIr ratio to calculate F.? L/Lr, and P jI\ under the appropriate end condl-
tion category.
In this case, by using Table 1, L, = 10', L. = 30',
P, = 0.0, P T = p, then L/Lr = 0.33, P./PT = 0.0 and
the end condition is "Fix-Free"; theretore, by enter-
ing the value ofI\II, (the ratios of moments of iner-
tia of upper and ower segments, respectively) the

•
values of K, and K, can be determined by interpo-
,, lation.
•• Kunming Gwo, P.E.
. I. ~~
HCI Steel Building Systems, Inc.
Arlington, WA
~)(~
-«
Another answer:
()

'" he Ur ratios do not work well for this type of

,
,,
• 0
T column. Instead, calculate the theoretical
Euler buckling load, and then check both the
elastic and inelastic allowable buckling loads.
..., ,
o~~
, Ther e are several procedures to calculate the
-« Eul er buckling load. Simple hand calculation
methods include Finite Differences, integration, or
Newmarks Method. Example calculations for the
first two methods are available in " Principles of

-Ift-_.
!ISSLI"''; I< = :2 . 0
Structural Stability Theory" by Alexander Chajes,
and the la st in "Theoretical and Applied
Mechanics" edited by N.M. Newmark.
After finding the theoretical Euler buckling load
(P), determine whether elastic or inelastic buck-
ling controls. If the Euler buckling load (P) is less
ince the r's (r a dius of gyration) are known , than P j2 (where P = AF ) then elastic (Euler)

S the key to the calculation ofF. is to find the K

in the allowable s tress equation for axially
loaded compression members.
buckling controls. This is t he basis for the AISC
ASD equation for C, see the AISC ASD
Commentary. If elastic buckling controls, simply
multiply the theoretical buckling load by "/" and
Per AISC Design Guide, "Industrial Buildings,

•
Roofs to Column Anchorage " Appendix B: yo u have the allowable axial load .
Calculation of Effective Length s of Stepped If inelastic buckling controls (i.e. P,,>P /2) it
Columns, the values of 1(, and K" representing the becomes a littl e more complicated. Lets dissect
effective length factors tor upper and lower seg- AISC ASD Equation E2-1. The denominator is sim-

Modern Steel Construction I August 19951 9

 S TEE L NTERCHANGE
ply a sliding factor of safety that results in 23/"
where KIIr = C , and results in '13 when KIIr = O.
For the momen't, call the denominator the safety
factor, SF. Now we can rewrite equation E2-1 as:
F = 11 - «Kllrl'/(2C 2»JFISF
What is the flatness tolerance for webs of
welded plate girders?

Since for statically loaded (bui ldings) struc-

tures" web flatness does not affect tbe structural
•
This equation can be rewritten in terms of force integrity of a girder, neither the LRFD
s follows: Specification not the AISC Code of Standard
Practice provides a limi tation on the maximum
p. = 1(1 - AF,l 14P, JAF, I S F out-of-flatness of girder webs. AWS Dl.l Section
si ncEP" = 1l'E I (K1 I d 8.13.2 does, however, provide such requirements
andC, = /21[' E I F, for welded plate girders. Problems arise, however,
when these tolerances are applied to girders with
Now, having calculated P from one of the meth- thin webs. Specifica ll y, in girder webs less than
ods noted above, and knowing" all the other terms, ' I,(in. Thick, they do not accou nt for operational
you have only to determine the appropriate safety dltfi cu lti es caused by sh rink age r es ulting from
factor, SF. The term (Kllr)/C, can be rewritten in web-to· flange welds and/or welds that attach stiff-
terms of force if one remembers that: eners to the web . Because of this, in some cases,
flatness within AWS tolerances cannot be practi-
,
C =.j2n' E/F , cally provided.
AISC recommends that, for statically loaded
Substitute this into the equation for (Kllr)/C, and (building) structures, the dimensional tolerance for
you will finally get: deviation from flatness of a girder web less than
5/, ._in. Thick, without stiffeners or with stiffeners
(KII r)C, =/i(F,A) I 2P, ) on one or both sides, be determined by the larger of
\h-in or AWS Section 8.13.2. If architectural consid-
Substitute this into the denominator in place of erations require special flatness tolerances, such

•
(Kl/r)/C, and you have an equation rewritten in special requirements must be id entified on the
terms of force. Use the small er section to deter- engineering drawings an d stipu lated in the bid
mine steel area, A, since ine lastic buckling will documents.
occur there first. American Institute of Steel Construction
Remember that K is a lready included in P , Cbicago, IL
since you determined the buckling load P" directly
with its actual houndary conditions.
Duane L. Siegfried, P.E.,S.E.
Ralph Hahn and Associates, Inc.
Springfield, IL New Questio ns
Another response:
Are tbere special requirements for the

T
he most common approach is to use the for- design of High-strength A325 or A490 bolts
mula P,,=K,1l2E I,lL" where E II, is the stiff- that are going to be in a high temperature
ness of the smaller section, L the total length area?
of the column, and K, depends not only on end con- Alice Leich
straints, but a lso on the ratio of stiffness and S.E.S Environmental, Inc.
lengths for the two sections. Knoxville, TN
Values of Kl are tabulated for different end con-
straints and ratios of stiffness and lengths in If a W-shaped column is made up of three
"Formulas for Stress and Strain", by Raymond J. welded p lates, how does one design the welds
Roark and Warren C. Young, McGraw-Hill, New connecting the plates together?
York (various editions).
For the case in question (cantilever column), ~
varies between and 0.5, with the larger section up Correction: The answer by James
to twice as stiff as the smaller one. McCarthy in the June issue referred to the wrong
Behrauz Jazayery, P.E. question. The correct question is: In a partially
Mueser Rutledge Consulting Engineers cover·plated column, how would you analyze the
New York, NY column for governing I I r ratio ? We regret the error. •

10 I Modern Steel Construction I August 1995

 5
•
TEE L NTERC H A N G E
Steel Int erchange 18 an open forum for Modern Steel Answers andlor questions should be typewritten and double-
Construction readers to exchange useful and practical profes- spaced. Submit.tals that have been prepared by word-proceSSing
sional ideas Rnd information on all phases of steel building and a rc appreciated on computer diskette (either 88 n Wordperfect
bridge construction. Opinions and suggestions are welcome on file or Ul ASCLl format).
any subject covered In this magazme. If you have a question or The opinions expressed in Steel Interchange do not necessar-
problem that your fellow readers might help you to solve, please ily represcnt an official position of the American Institute of
forward it to Modern Steel COflstruction. At the sa me time, feel Steel Construction, Inc. Rnd have not been reviewed . It. is recog-
free to respond to any of the questions that you have read here. nized that the des ign of structures is within the sco pe and
Please send them to: expertise of a competent licensed structural enginNf, architect
Steel Inter change or other lice nsed profess ional for the application of principa ls to
Modern Steel Construction a particular structure .
One East Wacker Dr., Suite 3100 Informalion on ordering AISC publications Ill(>ntioned in
Chicago, IL 60601·2001 this article enn be obtained by calling AlSC a t 8001644 ·2400.

The following responses from previous Steel b- 60001 _ 1901

Interchange columns have been received: - JF, X 1000 -"Jr;
Give n a w a ll of sh eet m e tal or pl ate s ub- which is the same as g iven in AISC Allowab le
j ecte d to fluid pressure and stiffe n e d b y sam e Stress Design Table B5.1.
size paralle l me m ber s s p aced r egularly, w h at The above formula is w idely utilized for the
section (or wid t h ) o f t h e wall s h a ll be u sed design of duct stiffeners. However, a 4 in. limit for
that contributes to the section of a stiffe n er? be is conservatively used by des ign engineers to
The stiffe ning me mbe r may be a flat bar, an compensate a nd account fo r the two way bending
in the plate.

•
angle, a channe l (see figure ) or any othe r sec-
tion. For negative pressu re in the duct or wind load
acting on the duct
surface, stiffe n er's
T he effective width of the plate to be used in
computing design properties (i.e. moment of
inertia and section modulus, etc. ) Of the section
outstanding leg wi ll
become the compr es-
may be determined based on the limiting width- sion flange. This will
thickness ratio for compression elements formula : require that either the
allowab le stress be
b 95 1901,
T = Jr,' as b.= 2band I = I" b. = 7, reduced in accordance
with AlSC provisions
where I, = thicknessof the plate. or additional lateral
support be provided at
For the channel used as a stiffener, b. = II + ~" required spacing not exceeding the ca lcu lated L,
for the effective section. The suggested lateral sup-
where II =flange width ofthe channel section. port detail is shown.
It may be noted that be is independent of the L.Sundar
value of the thickness of the stiffener. Raytheon Enginee rs and Constructors
Another independent reference source, USS T a mpa, FL
Steel Design Manual, 1974, page 86 (Authors: R.L.
I s the r e a more effici e nt and cos t-effective
Brockenbrough and E.G. Johnston ), uses the fol -
lowing formula for a similar situation: way to connect a masonry shear wall to struc-
tural st eel framing? The most common prob-
_
b 6OOor le m with the following d e tail is that once the
-7 m asonry is built up to the bottom flange of
where b =b. =effective wIdth of the plate. the b eam, the r e is not e nough room to install
I = plate thi cknes~ in. the grout and continuous r e inforcing b a r s in
the bond beam at the top of the wall. If the
F, = Yield strength of the plate steel, psi
bond beam is dropped a course in e le vation,

• It may be noted that this formula is derived

from the same AISC req u irements for bIt. When
t he unit for F is changed from psi to ksi, it is
noticed that th~ formula becomes:
the masonry to steel b eam connecting angle
ve rtical le g or bent plate ve rtical le g becomes
excessive ly long.

Modern Steel Construction I Decemlx-'r 19951 9

 S
•
TEE L NTERCHANGE
.....
I

-
,
, !
!
.'" KIf BCL T POSJlJD-I 10 "ATC~ OftOPPCD CORSe J... TH[ aCtlD lCAH CLeVA nON)

~ . : .. f- '-
I

1["

THu, Fang
he a bove detail might be somehow more em-
cient and cost-effective. New Questions
Butler Manufacturing Company Listed below are questions that we would like the readers to answer
Shanghai P.R.C. or discuss.
If you have nn answer or suggestion please se nd it to the Steel •
Are there special requirements for the Interchnnge Editor, Modern Steel Construction, One East Wacker Dr ..
design of high-strength A325 or A490 bolts Suite 3100, Chic8b"O, IL 60601-2001. If you have a question or problem
that readers might help 8Olve, send these to the Steel In terchange Editor.
that are going to be used in a high tempera-
ture service?
Slory ShfOf, VI/

T he term "high temperature" requires more defi-

nition in order to answer this question . The
A325 and A490 bolts are not intended for high-
temperature service., however, the A193 specifica-
tion is s pecifically for high-temperature servIce.
The a llowable stresses will vary with temperature
no matter what type of bolting material is selected.
The Manufacturers Standardization Society
publishes SP-58 which serves as a guide for high- -'-1f-v.
temperature pipe hanger design . Table Al lists
various bolting materials and allowable stresses at
various temperatures.
Uncoated bolts designated as A325 or A490 can
In checking panel zone web shear in a col-
be used to their full capacity if the service tempera-
ture is within the range of -29 degrees C to 325 umn member why is M, d.efined as the sum of
the lateral load and graVIty load moments on
degrees C. Galvanized bolts should be limited to
the leeward side of the connection, and M~
120 degrees C to avoid problems WIth corrosIOn
inhibiting properties. Corrosion inhibiting proper- defined as the difference between the lateral
load and gravity load moments on the wind-
ties of alloy materials a lso vary with temperature
ward side of the connection? It seems to us
and corrosive concentration, and should be investi-
that the difference of moments apply on the
gated.
leeward side and that the sum of the

•
Harold O. Sprague
Black & Veatch moments should apply on the windward side.
Kansas City, MO
Stuart Snyder, P.E.
Snyder Associates
West Chatham, MA

10 / Modern Steel Construction I December 1995

 S TEE L NTERCHANGE

• Steel Interchange is an open forum for Modern Steel

Construction readers to exchange useful and practical profes-
sional ideas and information on all pbases of steel building and
bridge construction. Opinions and suggestions are welcome on
any su bject covered in th.is magazine. rf you have 8 question or
problem that your fellow readers might help you to solve, please
Answers and/or questions should be typewritten and double-
spaced. Submittals that have been prepared by word-processing
are appreciated on computer diskette <either 88 a Wordperfect
file or in ASCII format).
The opinions expressed in Steel interchange do not necessar-
ily represent an official position of the American Insti tute of
forward it to Modern Steel Construction, At the same time, feel Steel Construction, Inc. and have not been reviewed. It is recog-
free to respond to any of the questions that you have read here. nized that the design of structures is within the scope and
Please send them to: expertise of a competent licensed structural engineer, architect
Steel Interchange or other licensed professional for the application of principals to
Modern Steel Construction a particuJar structure .
One East Wacker Dr., Suite 3100 Inform ation on ordering AISC publication s mentioned in
Chicago, IL 60601-2001 this article can be obtained by calling AISC aL 312/670~2400 ext.
433.

The following responses from previous Steel the net tension that the anchor bolts experience
Interchange columns have been received: does not exceed the clamping force that results
from "snug tight" tightening of the nuts. Kulak,
Specifications currently exist which Fisher, and Struik in their book Guide to Design
require minimum pretensioning loads for slip Criteria for Bolted and Riveted Joints indicate that
critical connections. There is, however, no this clamping force from "snug tight" nuts in A307
guidance regarding minimum pre-loading of anchor bolts is not very great and should not be
anchor boIts which occur at column bases. considered to have any influence on the connection
While in most situations this issue is academ- design. The preloads that result from "snug tight"
ic since the anchor bolt nut and thread pro- nuts on A307 bolts are usually in the elastic range
jection are below the plane of the concrete (somewhere in the sloping portion of the stress-
slab on grade and are eventually embedded strain curve) where minor variations in the start-

•
in concrete at the slab isolation joint, there ing point, amount, and accuracy of the nut rotation
are instances where the nut and thread pro- have a greater influence on the amount of preload .
jection remain exposed_ Is tightening the nut On the other hand , pretensioning high-strength
to "snug tight" and tack welding the nut to bolts to the specified values actually stretches the
the bolt thread the only solution in prevent- bolt (ca lled set) and produces a large, constant
ing the nut from backing off? clamping force that is baSically unaffected by the
conditions at the starting point of nut tightening
n general, anchor bolts are selected from mater- (snug tight).

I ial meeting ASTM A307 specifications . A307

specifications require material that conforms to
the A36 specification. The lower strength of this
Tall , lighter structures where large latera l and
tensile forces frequently occur depend on their
anchor bolts to carry tension and prevent upward
material compared to high-strength bolts, such as or horizontal movement at the foundation inter-
A325, does not lend itself to high pretension loads face. Other examples would be anchor bolts used
for a given bolt diame ter . When your anchor for large equi pm ent foundations , s uch as paper
requirements call for resistance to high tension or machine foundation anchor bolts. In these cases,
conditions where slippage due to shear is not per- high-strength anchor can be specified and preten-
mitted then preten sioning using high strength sioned to resist any large dynamic and thermal
bolts may be used. Other methods, such as shear loads. These loads can produce large, lateral forces
keys may be used to prevent slip . High-strength that are present at all times. These "slip critical"
anchor bolts are heat treated and quenched which connections are designed to prevent any slip which
increases their load carrying capabilities. A307 bolt can ca use misalignment in the preci sion eq uip-
material is not treated and therefore cannot be ment. These anchors are us ua lly pretension ed to
expected to produce high, consistent preloads for a meet the equipment supplier' specifications.
given bolt diameter. Another method of preventing loosen ing of a
In most cases anchor bolts are used in locations "snug tight" anchor bolt nut (besides tack welding)
where a small clamping force in conjunction with is to furnish two nuts and torque the second nut
the combined friction from deadweight and or against the first nut.
shear keys is all that is required to resist the occa- Robert R. McGlohn

•
sional shear and tensile forces. The design tension Rust Engineering Company
loads at column bases are usually a result of large Birmingham, AL
wind forces that the structure seldom experiences
wi th the presence of large dead loads. Therefore,

I Modem Steel Construction I February 199519

 S TEE L NTERCHANGE
The AISC Manual includes
examples and figures in the con-
nection sections, some of these
Socking If
usld s •
f
connections include weld access
holes in the beam member. What
~ l10dius fl"Cui by
are the dimensioning require- H SH
drill or h<M SO"
".1. 1)
ment for these weld access ~-""'- 11 {SH o ~ in.
holes? They are not given in the nol. 1
example problems. +-__~____~ ~~1_'._5~
" r-__~
l l"l ~ in.

~
l of the examples and deta ils
in the man u a l fo ll ow t h e AngJ. .1
eq u irements of t h e AISC sl.". n.1
S pecificatio n for S tructu ra l Stee l criticol
Buildings. Section J1.6 of the LRFD Opflonol m.lhod (or
1 1.5,. making com" rodlus
Specification and Section Jl.8 of the
ASD Specification include require- Notes:
me n ts for beam co pes an d we ld 1. Fo r ASTM A6 Group" " 5
.hapel Ind welded bUilt-up
access holes . These dime nsionin g . hape. with plate thlc.ltneue.
requirements are for all weld access more than 2 in .• preheat to 150
degnes F pnor to thermal cut-
holes and copes. The commentary to tm" gnnd and InlIpect thermal·
eac h sectio n i ncl ud es dr aw in gs 110010d sho".' or rttJ.1 I, rut ~ of ac:c.a ho&e Id;LDI

wruch demonstrate trus weld access

g,.... woldod sho". 1,1 ",/thd SholY
~.
1,1 magneLic particle or dye pene--
tralion method. prior to mak-
log web I n d n a ngl! .p h ce
hole and cope geometry. The figu re grnove weld..
a t right is repeated from the AISC 2 RamUlI ,hall provK:le smooth nO\Ch-r~ trantllion; R velter than or equal to 318-10. (typlI:a\ Vl-ID.}.
3. Acceu openHlg mllde after weldin, web to nan.,
Commentary. 4_AC'Ct'U openmg made before weldmg web to nange

•
5. 1'hmIe are typical detail. for JOint. welded from one aide 8gnlntt Iteel backing. AlternatIVe joint
dea1pl1 I hould be ooclIldered.

N E W Q u EST o N S
Listed below are questiollB that we would like the readers to answer
or discuss.
If you have an answer or suggestion please send it to the Steel Inten: ~
hange Editor, Modem Steel Con8truction, One Ea8t Wacker Dr., Suite 31
00, Chicago. IL 60601·2001. Questions and l1!8ponses will be printed in v>JFNvAL LF6t F= ==
futu re editions of Steel lnterchange. Also, jf you have a question or prob- AH ..Lr ~
I:!I!:rc/\
lem that readers might help solve, send these to the Steel Interchange

I
Editor.

Is the method of determining the flexura l design ~IIEA/( £.HT~

strength of a single angle with unequal legs as out- ,I
lined in the Specification for Load and Resistance
F ac t o r Des ig n of S in g le-An g le Me mb e r s,
(Dece mber I , 1993) valid when the a ngle is not
.. 1~ e 1"
loaded through its shear center?
If the method is valid, what effect does the load
eccentricity to the shear center have On the flexur- y'\
al strength? • IV
If the method is va lid and M has been deter- )I.'
mined a bout the principle axes, should th e moment
(M.J about the x-axis be broken into its components
a bout the minor and major axes by multiplying the
moment (M ) by the sin 9 or by cos 9?
---,- 1\ ~
£
Charles"L Bowman
Morrison and Sullivan Engineers
Raleigh, NC

10 I Modern Steel Construction I February 1995

•
 S TEE L NTERCHANGE

• Steel Interchange is an open forum for Modern Steel

Construction readers to exchange useful and practical profes-
sional ideas and information on all phases of steel building and
bridge construction. Opinions and suggestions are welcome on
any subject covered in this magazine. If you have a Question or
Answers and/or questions should be typewritten a nd double-
spaced. Submittals that have been prepared by word-processing
are appreciated on com puter diskette <either 3S a Wordperfect
file or in ASCII format.l.
The opinions expressed in Sleellntercliange do not necessa r-
problem that your fellow reade rs might help you to solve. please ily represent an official pos ition of the American Instit ute of
forward it to Modem Steel Construction . At the sa me time, feel Steel Construction. Inc. and have not. been reviewed . It is recog-
free to respond to any of lhe questions that you have read here. nized t.hat the design of st ru ctu res is within the sco pe and
Please send them to: expertise of a competent li censed structural engineer. architect
Steel Interchange or oLher licensed professiona l for the applicAt.ion of principals to
Modern Steel Construction a particular structure.
One East Wacker Dr., Suite 3100 Inform atio n on ordering AISC publications ment ioned in
Chicago, IL 60601·2001 this article can be obtai ned by ca lling AISC at 3 121670-2400 ext.
433.

The following responses from previous Steel ing are more appropriate:
Interchange columns have been received: - Fisher and Buettner, Industrial Buildings -
Roofs to Column Anchorage, Design Guide 7,
In what instances, if any, and under what AlSC, 1993.
criteria can the attachment of grating with - Guide for the Design and Construction of
mechanical fasteners be used to provide lat- Mill Bu ildings, Technical Re port No . 13 ,
eral bracing to the compression flange of the Association of Iron and Steel Engin ee rs ,
members supporting the grating in applica- Pittsburgh, PA, 1979.
tions such as walkways and catwalks? - Merritt, F. S., Structural Steel Designers
Handbook, McGraw-Hili Book Co., New York,
ur company manufactures industrial grade 1972.

O fiber gla ss grating for walkways and cat- - Gaylord, E. H . Jr . and C. N . Gaylord ,

•
walks su pported by all medias, i.e. steel, alu- Structuretl Engineering Handbook , 2nd
minum, stainless stee l, timber, and fiberglass Edition , McGraw-Hili Book Co., New York,
beams . Weight reduction is very critical for this 1972.
type of application, and eliminating cross beams is Gary J. Davis, P.E.
quite common. Phoenix Engineering Services
Although design criteria for this type of applica- South Milwaukee, WI
tion is limited , two parameters used for design are:
1. The type of mechanical fasteners used - must Specifications currently exist which
be capable to resist cross movement and/or twist- require minimum pretensioning loads for slip
ing of the compression flange. When tightened, the critical connections. There is, however, no
clamping action should produce the proper friction guidance regarding mjnimum pre-loading of
between grating and beam. anchor bolts which occur at column bases.
2. Use L, = maximum unbraced length of the While in most situations thjs issue is academ-
compression flange or 2'-0" maximum to deternline ic since the anchor bolt nut and thread pro-
fastener s pacing. jection are below the plane of the concrete
These two general rules seem to satisfy both the slab on grade and are eventually embedded
fastening requirements for the grating and lateral in concrete at the slab isolation joint, there
support for the compression flange. are instances where the nut and th"ead P"o-
Richard L. Cole, P.E. jection remain exposed. Is tightening the nut
Aligned Fiber Composites to "snug tight" and tack welding the nut to
Chatfield, MN the bolt thread the only solution in prevent-
ing the nut from backing off?
Serviceability is a particular concern for
crane systems in industrial buildings but is nug tightening and tack welding the nuts is
not clearly covered in the standa,'d code lit-
erature_ What are deflection limits for crane
runway systems?
S not the on ly solution to prevent the nuts from
backing off. We have s pec ifi ed A449 high
strength anchor bolts (tensile strength = 105 to 120

T
h e r eferences given in a prev iou s Steel ksi ) instead of the ordinary A36 anchor bolts when

•
Interchange column are mainly concerned the structure is s ubject to fatigu e loading.
with cranes and hoisting equipment. If some- We pretension the bolt to develop 70 percent of
one is interested in industry standard references the s pecified minimum tensile strength of the bolt.
for allowable crane runway deflections, the follow- The bolt is greased with bond break er all the way to

Modern Steel Construction I January 19951 9

 -- - _ ._- - ---

5 TEE L NTERCHANGE
its end to permit stretching of the bolt while ten-
sioning. The tension is developed into the footin g
by an adequately designed heavy plate at the bot-
tom of the bolt. To furth er prevent th e nut from
loosenjng ( which is not likely to occur for a prope r-
•
ly pretensioned bolt), a lock nut or Pal nut can be
added to secure the nut afte\" pretensioning. M,e..
We used th e A449 a nch or bolts for a 160' ta ll
steel t ubular tower that supports a 600 kW wind
turbine unit. The tower was des igned to meet the
UBC a nd Eurocode 3 Fa tigue Provisions. Eurocode
3, Cha pter 9, Fatigue, s pecifies a n extremely low
stress ra nge for a n ordinary anchor bolt without
PLAN
preloading (the lowest stress ra nge category in the
Eurocode). The use of high strength a nchor bolts
with preloading is a ppa rently the common pract ice
in Europe when the fatigue strength is critica l in
the structura l design .
David L. Koo, C.E.
Warren A Minner & Associates
Bakersfield, CA

New Questions
Listed below are questions t h at we wo uld like
t he readers to a nswer or discuss.
If you h ave an a nswer or suggestion pl ease send
it to the Steel Inte rchange Editor, Modern Steel Co
nstruction , One East Wacker Dr., Suite 3100, Chic
ago, IL 60601-200l.
V i eW A •
Qu es tions a nd r es pon ses will be pri nted in
future editions of Steel Inte rch a nge. Al so, if yo u
h a ve a qu esti on or probl e m th at r eaders might
he lp solve, send these to the S tee l Inte rch a nge
Editor.

In tbe partial plan sbown (top & middle),

):~)*..\1:
.•': , l~." ~.,
.f ~:.:\
. .,. . "..,,')
~~'JCVz.
~J~~;~-\ft'~
eacb of the tube beams is to be moment con- .
nected to tbe tube column by welding. All
steel is exposed to view of pedestrian traffic, ",-VI¢fpLf
~TI lJ
but is protected from the elements. What is
an economical procedure for making the
joints?
William Dy/,er
-(
Naperville, IT.. rh '" ~;I" t/I.,)< Vz.
How is the L5 x 3 1/ 2 x 1/, angle shown in the
figure (bottom right) designed? The angle is ;;
used as a rail guide for a roll-up door and is
bolted to other steel members 12" on center.
Glenn Whritenoltr
PL~N
Bechtel Savannnah River, Inc.
Augusta, GA

•
10 I Mode rn Steel Construction I J anuary 1995
,....
~

.-
, ~)

S TEE L NTERCHANGE
Stee l Int e rchange is an open forum for Mod e rn Steel Answers andlor questions should be typewritten and double~
COflstruction readers to exchange useful and practical profes- spaced . Submittals that have been prepared by word ~ proccssing
sional ideas and information on all phases of steel building and a re appreciated on computer diskette (either as a Wordperfect
bridge construction. Opinions a nd suggestions a rc welcome on file or in ASCII format ).
any subject. covered in this magazine. [ f you have 8 question or The opinions expressed in Steel l TlterchaTlge do not necessar~
problem that your fellow readers might help you to solve. please ily represent an officia l position of t he American Institute of
forward it to Modern Steel Construction . At the same time, feel Steel Construction, Inc. a nd have not been reviewed . It is recog·
free to respond to any of the Questions t.hat you have read here. nized that the design of structures is within the scope and
Please send them to: expertise of a competent licensed structural engineer, architect
Steel Interchange or other licensed professional for the application of principals to
Modern Steel Construction a particular structure.
One East Wacker Dr., Su.itc 3100 Information on ordering AISC publications mentioned in
Chicago, IL 60601·2001 this article can be obtained by calling AJSC at 800l644 ~ 2400 .

The following responses from previous Stee l at its outer end. The ANSI method is the most log-
Interchange columns have been received: ical, L unbraced equals 2 times the actual length .
If the cantilever is braced, the brace should con necl
Are there any limitations on the span to to the top tension flange at the end, to offset twist'.
depth ratio of beams required by AISC The interior unbraced length, should be the dis-
Specification for Structural Steel Buildings? tance between supports, per ANSI specifications on
n the Commentary on the AlSC Specification (9 Monorail Systems' .

I edition) chapter L, section L3 the following rule

was s uggested : "Th e d e pth of fu lly stressed
beams and girders in fl oors should , if practicable,
Often the size of the trolley beam is controlled
by the fl a nge width, to be wide enough for the bolt-
ed gage plu s 2 proper edge distances. Also the

•
be not less than (F/800) times the s pan . If mem- bea m depth must be deep enough for the trolley
bers of less depth are used, the unit stress in bend- wheel diamete r. Flange bendin g strength unde r
ing should be decreased from than recommended the wheels is important a lso.
above." I Timoshenko, S., "Theory of Elastic Stability",
Alex Krasilousky, P.E. p. 260 & 269, 1961.
Ridgefi eld Park, NJ , AISC , "Ma nu a l of Stee l Const ructi on,
Allowable Stress Des ign ", p. 5-47 , Ninth
Edition.
For a continuous trolley beam with multi- 3 ANSI, "Am e rican National Standard
ple spans and cantilevered e nds what is the Specifications for Underhung Cranes a nd
lateral unbraced le ngth for the bottom Monorail Systems", p. 7, MH 27.1-1981.
flange? , AlSC, "Steel Design Current Practice, Bending
Members - Buckling and Bracing", p.27.
Claude R. Krout, P.E.
Birmingham, AL

Can an existing steel beam and concrete

slab b e made to work together in composite
action by adding studs to the steel through
cored holes?
his question was previously responded to and

he late ral unbraced length of a cantilever T it was the auth or's opinion that the existing
loads presently on the beam should act on

T t rolley beam is ap proxim ate ly h a lf' of the

canti lever span, provid ed the s upport is
the bare stee l. Howeve r, ut ili zin g the Load &
Resistance Factor Design code (LRFD) and assum-

• braced against twist. The AlSC code' states that L ing plastic stress distribution for positive moment,
shall conservatively be taken as a unity, if the s up- the composite section can carryall the load if the
port is braced against twist. ANSI' Monorail followin g requirements are met:
Specifications specify L to be 2 times the length of 1.iI>M" ~ M, for the composite section .
cantilever, since the cantilever is not fully stayed 2.Yi e ldin g of the bea m does not occur at t he

Modern Steel Construction I July 19951 9

 5
•
TEE L NTERCHANGE
maximum possible service load. For design purposes these stresses should be con-
3.Composite action between the grouted holes sidered as acting in combination with the normal
and existing concrete occurs. and shear stress due to bending.
4. The deflection of the member is acceptable. In addition, deflection and rotation due to these
Using load factor design, the nominal moment of torsional stresses should be added to the deflection
the section is developed when the entire section is due to bending when considering the serviceability
fully plastic. When this occurs, the relationship requirements of this angle.
between stress and strain is non-linear. Therefore, A very good source which outlines the calcula-
the existing dead load can be assumed to be carried tion of the torsional stresses indicated above is
by the composite section. Reference should be found in "Cold Formed Steel Design 2nd edition
made to Chapter I of the LRFD code under appendix B", Wei-Wen Yu. Additional information
Sections II. and 13. By utilizing this type of analy- on torsional stresses and their effects can be found
sis, significant load increase may be permitted in "Steel Structures design and behavior", Salmon
under the provisions of the LRFD code. & Johnson and in the AISC publication "Torsional
Kurt Seidler, P.E. Analysis of steel members".
Canfield, OH The commentary to the specification for single
angle members section C6 states " .. . the applied
moments should be resolved about the principal
Can yo u p rovide so m e i nfor m atio n on axes for the interaction check." If Mn is deter-
ecce n tr ic e ffects o n s in g le a n g le b e ndin g mined about the principal axis then Mu must be
m e mbers? converted from geometric axis loading to equiva-
he specifications for LRFD design of single lent principal axis loading. Hence, Mnx =Mn(sin )

T ang le members is valid for angles loaded

eccentric to the neutral axis and to the shear
center; however, the effects of these eccentric load-
and Muy = Mn (cos J.
The resolution of loading and stresses about the
principal axes may be neglected if the provision of •
ings must be considered in combination with sect. 5.2.1a is met. That is, as stated in the com-
stresses form all other load effects if the provision mentary to this section, if the angle is restrained
of sect. 5.2.1a are not met. That is, if the brick against lateral torsional buckling along its length
wall does not have the stiffness or connectivity to then bending occurs without any torsional rotation
the angle to prevent lateral torsional buckling or if or lateral deflection. Therefore, only bending about
the angle is not independently restrained then the the geometric x axis and shear in the geometric y
effects of this eccentricity must be considered. axis need be considered.
Furthermore, the location of the restraint with Thomas M. Vossm eyer, P.E.
respect to the vertical leg of the angle (i.e. the Salina, KS
extreme fiber of the compression portion of the
angle) should be considered when determining
restraint.
The location of the load with respect to the shear New Question
center will cause a torsional eccentricity. This
eccentricity will increase the shear and normal
stress in the angle requiring an increase in the In fi e ld bolte d connectio ns fo r g a lvanized
strength of the angle. The effect of the load eccen- me mbe r s, are bolt holes e nlarged t o account
tricity to the shear center will induce torsional for t h e layer of zinc whic h will b e d e posited ?
stresses in the member. These stresses can be cat- If so, b y how muc h and is it possibl e to treat
egorized into two types, pure torsion (St. Venant's th e res ul t ing h o l e as a s t a nd a rd hol e i n
torsion) and warping torsion. Pure torsion causes d esign?
pure shear stress only 1, = Gt(d<l>ldz), warping tor-
sion causes warping shear stress 1w = ESw(d' <I>Idz3) H ow do you calc ulate the mome nt ca p acity
of a double angle sh e ar connection?

•
and warping longitudinal stress crw = Ew.(d' <I>Idz') .
Under the loading conditions shown all three of
these stresses can be present. Their magnitude
will depend on the magnitude and location of the
loads and the boundary conditions of the angle.

10 I Modern Steel Construction / July 1995

 .-
.Il
' ,0

S N T E R C H ANGE
•
TEE L
Stttl Intrr~hange is an open forum for Modun ttel Answers andlor questions should be typewritten and double-
Construdlon readers to exchange useful and practical profes- spaced. Submittals thnt have been prepared by word-proc('sslOg
s ional ideas and mrannalian on all phases of steel building and an> appreciated on computer dlsk£'tte (either as 8 Wordperfect
bridge construction. Opinions and suggestions are welcome on file or in ASCII formal).
any subject covered in thiS maganne. If you have 8 quelilian or The opinions expressed in Sl"llllt('rchang~ do nol necessar·
problem that your fellow readers might help you to solve, plea~e Ily represent an officia l poSition of the American Institute of
forward it to Modern Steel Construction. At the some ti me. fee l Steel Construction, Inc. and have not bee n revi ewed. It is recog-
free to respond to any of the questions that you have read here. nized th at t he design of stru ctures is wi thin th e scope Rnd
Please send them to; expertise of n competent licensed structu ral enginee r. architect
Steel lnterchange or other licensed professional fo r th e application of prin Cipa ls to
Modern Steel Construction n particul ar s tru cture.
One East Wacker Dr., Suite 3100 Inform at ion on ordering AISC publi cations mentioned in
Chicago, IL 60601·2001 this article enn be obtained by ca ll ing Al SC al3 121670-2400 ext.
433.

Th e follow ing res ponses from previou s Steel

lnterchange columns h ave bee n rece ived:

For fire wall cons tr u ction, building cod es

say t b e walls h a ll h ave s ufficie n t stabili ty to
allow for coll a p se on e i t h e r side o f t h e w a ll
without colla pse of the wall. Wha t is t h e o p t i-
mum detail for t his type o f connection.
he sketch provided with the question submit-

T ted is a pplicable for a specific type of tied fire

•
wa ll ; non-load bearing, constructed between
rigure 12 Through Wall Tic PrimJry Stl"'('1 P.lr.llld To rtr(' W~lll
two double-column lines, structura l me mbers on
each side of the wa ll at the sa me elevation a nd pri-
mary fra ming members par a llel to th wa ll . For a
sce n a ri o s u ch as thi s the recomme nda t ions of for t he s lack provid ed in the through -wa ll ti es .
Factory Mutual Loss Prevention Da ta Book 1-22 This slack ins ures that the colla psing fram e on the
are very specific and are as follows . fire side of the wa ll will not pull on the wa ll before
The a nti ci pa t ed h ori zonta l compon en t of the there is resistance provided from the fra me on the
force resulting from the colla pse of the structura l unexposed side of the wa ll via the t hrough -wall
frame on one side of the wall should be resisted by ties.
the remaining structure on the opposite side of the Th e F actory Mu t u a l r eco mm e nd a t io ns a lso
wall. Th is is accompli sh ed through the use of include provisions for adequate sepa ration between
through-wa ll ties. The ties are designed based on the double-column line a nd the fire wa ll to prevent
the horizontal pull "H" calcul ated from the formul a damage to the unexposed structure during the ini-
provided in Recommendation #3 of the referenced tia l stages of the fire.
FM Data Book, us ing an a llowable stress of not D. Matthew S tuart, P. E.
mor th a n 10 ksi. A deta il of the recommended Th e Stellar Group
installation of the through-wall tie a t each column J acksonville, FL
line is shown in Figu re 12 of the same FM Da ta
Book. For the situa tion indica ted by the sketch in What is the mos t e ffi c ie nt way to e nlarge
question, it may be necessary to a lso install ties a n e xisting footing, whe n n e w loading condi-
more often tha n every column line. In e ither case, tions are a pplie d ?
here is a good article dealing with this prob-
enough slack should be provided in the tie connec-
tion to a llow for norma l buiJding movement.
While the through-wall ties insure the continu-
ity of the opposing fra mework a t the fire wall , fl exi-
T lem. It was published in the fourth qua rter
AISC Journ a l 1980 a nd was a uthored by
Agrawal a nd Stafiej. The pa ra mete rs requ ired to

•
ble masonry a nchors should be provided at a pprox- solve the proble m include ratios of the res pective
imate ly 2 to 4 feet on ce nte r to brace th e wa ll moments of ine rti a of th e two column sections,
laterally (see Figure 13 of the referenced FM Data ratios of axia l loa ds a ppli ed at the top of the col -
Book). It is important to note th at enough slack umn to loa ds at the lowe r section , and ratios of the
should be provided in t he anchors to compe nsate upper le ngth to th e low e r le ngth . Us ing th ese

Modern Steel Cons truction I May 19951 9

 '.

S
•
TEE L NTERCHANGE
ratios, one then uses a chart which gives equiva-
lent effective lengths factors for the composite col-
umn for six different end condition cases, pin-pin,
flx-free (Steel Interchange question case), fix-pin,
fIx-slider, fIx-fix, fIx-pin, and pin-slider. From the
determined effective length factors, the effective
lengths of the upper and lower column sections are
easily obtained for use in the Euler buckling for-
mula.
James F. McCarthy
Folsom, CA Fran M. Lacsina
Melrose Metals
Is the method of determining the flexural Freemont, CA
design strength of a single angle given in the
Manual appropriate for unequal legs not Is there a more efficient and cost-effective
loaded through the shear center? way to connect a masonry shear wall to struc-

M
ood reference for this question is a paper tural steel framing? The most common prob-
by Tide, Raymond H. R. And Norbert V. lem with the following detail is that once the
rogstad, Economical Design of Shelf masonry is built up to the bottom flange of
Angles, Masonry: Design and Construction, the beam, there is not enough room to install
Problems and Rep air, ASTM STP 1180 , John the grout and continuous reinforcing bars in
Melander and Lynn R. Lauersdorf, Eds. , American the bond beam at the top of the wall. If the
Society of Testing and Materials, Philadelphia, PA, bond beam is dropped a course in elevation,

•
1993, p. 60. the masonry to steel beam connecting angle
R. H. R. Tide vertical leg or bent plate vertical leg becomes
Wiss, Janney, Elstner Associates, Inc. excessively long.
Northbrook, IL

EEAM

TEQCX)E ~

New Questions
Listed below are questions that we would like
the readers to answer or discuss.
If you have an answer or suggestion please send .. -1----- ~
~.
it to the Steel Interchange Editor, Modern Steel Co
'.
' \r'~'~"
nstruction , One East Wacker Dr., Suite 3100, Chic
ago, IL 60601-2001. WI I 117 vamcAL 9...0T AT
EX'l'e() REN". NrO 3'-.4'o.c.
FAST'B'I TO o.u WI
Question s and responses will be printed in E:O() EEAM • SE£
SECT. IIS IO FCQ WALJ..
112' 0 )( a-.·
E>CP ~
• AI.. TERNA TE EA 5I)E CF
future editions of Steel Interchange. Also, if you M'EtF. f GROJT FU CMJ WAlL

have a question or problem that readers might S' DEIP u-a..c:x:x 80NJ EEAM
WI (2) • !I c;o.rr. CSLCR: TO
MATO< BEAM>
help solve, send these to the Steel Interchange
ef o.u SJ-EARW.Ail.
Editor.

Given a wall of sheet metal or plate sub-

jected to fluid pressure and stiffened by same
size parallel members spaced regularly, what Charles L. Bowman
section (or width) of the wall shall be used

•
Morrison and Sullivan Engineers
that contributes to the section of a stiffener? Raleigh, NC
Th e stiffening member may be a flat bar, an
angle, a channel (see figure) or any other sec-
tion.

10 I Modern Stee l Construction I May 1995

 S
•
TE E L NT E R C HAN GE
Steel Interchange is 8n open forum for Modern Steel Answers soeVor questions should be typewritten Rnd double-
Construction readers to exchange useful and practical profes- spaced . Submittals that have been prepared by word-processing
sional ideas and information on all phases of steel building and are appreciou.>d on computer diskette (either as 8 Wordperfect
bridge construction. Opinions and suggest.ions are welcome on file or in ASCII format),
any subject covered in this magaz.ine. If you have 8 Question or The opinions expressed in Sleellllfcrrhatlg(! do not necessar-
problem that your fellow readers might help you to solve. please ily represe nt an official position of the American Ins titute of
forward it to Modern Sleel Construction. At the sa me time, feel Steel Construction, Inc. and have not been reviewed. It is recog-
free to respond to any of the questions that you have reud he re. nized that th c design of st.ructurcs is wit.hin t.h e scope and
Please send them to: expertise of n competent. licensed structural engineer, architect.
Steel lnterchange or ot.her licensed professional for the applicat.ion of principals to
Modern Steel Construction a particular st.ructure.
One East Wacker Dr., Suite 3100 Information on ordering AISC publicntions mentioned in
Ch icago, IL 60601·2001 this article cnn be obtained by calling AISC at 3121670-2400 ext.
433.

The following responses from previous S teel Another r esponse:

Interchange columns have been received:
he weld between the fl ange and web of a fab-
Whe n making a wide flange section out of
three plates, can you weld on only one side of
the w e b?
T ricated wide fl ange section that is a fl exural
or co m p ress ion me mbe r s h ou ld be deter-
mined by the computed shear between the flange
and web. If the computed shear can be carried by a
olution to the problem requires a tee joint. weld on one side of the joint there is no reason to
Aj This partial penetration joint is prequalified
y the American Welding Society. One crite-
arbitrarily weld both sides. Millions of welded
members in rigid frames with one·side welds are
ria for its use is that the web plate be greater than performi ng well a ll over the world and have been

• \4" thick. Preparation of the web plate requires a

single 45 bevel. The effective throat thickness is
determined by the depth of the bevel minus".
Ray Schork
Bayer-Beck e r Engineer s
Fairfie ld, OU
for over fifty yea r s . As w it h a ny product ion
process, tolera nces and qu a lity of workmanship
must be monitored. The angle between the fl ange
and web should not be a llowed to deviate signifi -
cantly from 90 degrees, for instance.
There are cases where one-side welding is not
appropriate, for example, crane beams and beams
Another r esponse: that are going to be hot-dip galvanized. Beams
with high tension loads perpendicular to the flange
es. The weld between web and flanges can (i.e. underhung cr a ne attach ments and moment

Y be on only one side and need only be large

enough to transfer the horizonta l shearing
stress between the web and the flanges under stat-
connections to the fl ange) shou ld be reinforced with
a second weld in the affected area.
Donald L. Johnson P. E.
ic loads. In some cases, if the web of this built-up Principal Engineering Cons u ltant
section is thin enough that the fuJI penetration can Butle r Manufac turing, R esearch
be achieved with a fillet appHed on only one side. G randvie w , Missouri
Especially, this can be commonly found at main
framing members of a pre-engineered steel build- What is the mos t e ffic ient and cost-e ffe c-
ing on which the majority of main frames comprise tive way to connect a s teel wide flange girde r
three-plate (built-up) sections. to a concre te column?
However, if the built-up members a re s ubject to
suming moment does not have to be trans-

N
dynamic loads, the notch which is sometimes pro-
duced by welding on one side on ly may lead to ferred through the connection, the simplest
fatigue problems. In such a case, fatigue stresses nd most efficient connection would proba-
should be checked according to the procedures bly involve the installation of a plate, with appro-

•
defined in the AlSC Manual and other appHcable priately sized a nchors to transfer shear, fl ush with
codes. the face of the column. The plate wou ld be secured
Kunming Gwo, P.E. to the inside face of the colu mn fo r mwork to pre-
HCI Steel Building Systems, Inc. ve nt its dis location du ring co ncrete placemen t.
Arlington, WA After t h e fo rm wo rk fo r the co lu m n h as been

Modern Steel Construction I March 19951 9

 S TEE L NTERCHANGE
strip ped, either a shear tab, seat angle or double
angle could be welded to the face of the steel plate
so as to produce a "standard" simple connection.
This concept is frequently used in precast con-
crete construction and design information for t he
I
F a?
n a partially cover-plated column, as
shown below, how would you analyze the
column for governing Vr ratio to calculate

Vijay P. Khasat, P.E.

•
embedded pl ate can be found in the PCI Design Clinton,OH
Handbook or in various ACI publications.
Stuart K Jacobson
Stuart K. Jacobson & Associates, Ltd.
Northbrook, IL

New Questions H
• ""!';'---

Listed below are questions that we wou ld like

the readers to answer or discuss. •• ••
If you have any questions, please send them to: ~~
Steel Interchange, do Modern Steel Construction, , "
One East Wacke r Dr., Suite 3100, Chi cago, IL ~)C.,...
~<
60601-2001.
Qu estions a nd res ponses will be printed in ,
fu t ure editions of Steel Interchange. Also, if you o
have a question or problem tha t readers might '" --
.
•
help solve, send these to the Stee l Intercha nge
Editor. ,
, a a

...
0 .. ..;
..... II II

PJ
e there any limitations on the span to
depth ratio of beams required by AlSC "'=<
pecification for Structural Steel
Buildings?
flS51Jf>1~ }<. = z. 0

~ ---
he Manual of Steel Construction

T includes many items that are used along

with structural steel frames, this is very
convenient for structural engineers.
However, some of the tables do not provide
all of the information needed by engineers. F/t;UR£ .t.
One of the tables that AlSC includes covers
the dimesioning of cotter pins. What is the
strength of cotter pins listed in the Manual of
Steel Construction? Where can these items be
obtained?

T
he AlSC Code of Standard Practice in
Section 2.1 lists items that are classified
as "strutural steel" while Section 2.2
lists those items not classified as "structural
steel". The rules is the AlSC Specification
and Code of Standard Practice apply to
sturctural steel members. One of the items
classified as " not structural steel" is stairs,
catwalks,handrail and toeplates, what crite-
ria is used to design these members? •
10 I Modern Steel Construction I March 1995
r-- -. ---

S TEE L NTERCHANGE

• Steel Interchange is an open forum for Modern Steel

Construction readers to exchange useful and practical profes-
sional ideas and information on all phases of steel building and
bridge construction. Opinions and suggestions are welcome on
any s ubject covered in this magazine. If you have a question or
problem that your fellow readers might help you to solve, please
Answers and/or questions shoul d be typewritten and double·
spaced. Submi ttals that have been prepared by word·processing
are appreciated on co mputer diskette (either 8S a Wordperfect
file or in ASe JI fo rmat).
The opinions expressed in Steel In terchange do not necessar-
ily represe nt an official position of the American Institute of
forward it to Modern Steel Construction. At the same time, feel Steel Construction, Inc. and have not been reviewed. It is recog-
free to respond to any of the questions that you have read here. nized that the design of stru ctures is within the scope an d
Please send them to: expertise of a competent licensed structutal engi neer, architect
Steel Interchange or other licensed profess ional for the application of principals to
Modern Stee l Construction a particu lar structure,
One East Wacker Dr., Suite 3100 In fo rm ation on ord ering A ISC publi cations mentioned in
Chicago, II.. 60601·2001 this article can be obtained by ca lling AlSC at 3 121670-2400 ext.
433.

Th e foll ow ing res ponses from prev iou s Steel What c r iteria is u se d to d es ign " NOT
Inte rchange columns have been received: S TRUC T U R AL S TEEL" m e mb e r s s uch a s
stairs, catwalks, handrail, a nd toe plates?
Are the r e a n y limi tation s o n t h e s p an to
d e pth r a t io of beams re qui red by AISC or those "NOT STRUCTURAL STEEL" mem-
Specification for Structu ral Steel Buildi n gs?

ne guide line that is given by AlSC can be

F be r design conce rns, the des igne r can use
e it h er th e certifi ed engin eerin g data a nd
ma teria l s pecification s from the individua l metal

O found in t h e All owa bl e Stress Des ig n

Specification Commentary for Section L3. 1,
which deals with serviceability design considera ·
manufacturer/supplier or the Metal Stair s Manual,
Pipe Ra iling Manual, Catwa lks Ma nual, a nd so on,
publi s h e d by th e N a tional Ass oci a tion of

•
tions. The commentary states the following: Architectura l Metal Manufacture rs (NAAMM) in
"Although d efl ecti on , ra th e r th a n s tress, is addition to the local building codes.
som etim es t h e cri ter io n of satisfactory designs , As regard to th e load criteri a,the building code
there is no single scale by which the limit of tolera- shall cover t he minimum design loads for each sub-
ble defl ection can be defined. Where limitations on ject item, for exa mple 1991 Uniform Building Code,
flexibili ty ar e desirable, they are often dictated by Table 23-A and 23-B.
the nature of collatera l building components, such Kunm ing Gwo, P.E.
as plastered walls a nd ceilings, rather than by con- HCI Steel Building Syste m s, Inc.
s ide ration s of hu ma n co mfort a nd sa fet y. The Arlington, WA
admi ssible a mount of movement va ries with t he
type of component . The most satisfactory solution The Ma nual of S teel Construction includes
must rest upon tbe sound judgement of qua lified many ite m s that are u sed along with struc-
engineers. As a guide, the following rules a re sug- t ural st eel frames, thi s is very conve nie nt for
gested: structural e ngin eer s. Howe v e r , s ome of the
1. The depth of full y stressed beams and girders tables d o n ot provide a ll of the information
in floors should , if practicable, be not less tban n eed e d b y e ngineers. One of the tables that
(F / BOO) times the span . If members of less depth AI SC includ es co ver s the dime n s ioning of
a re used , the uni t stress in be nding s hould be cotter p in s . What is the s tre ngth of cotte r
d e cre a se d in th e sa me r a tio as t h e d e p t h is pin s li s t e d in th e Manual of Stee l
decreased from that recommended above. C on st ru c tion ? Wh ere ca n t h ese ite m s b e
2. Th e d e pth of full y st r esse d roof purlin s obtain e d ?
should , if practicable, be not less than (F j IOOO )
times the span , except in the case of fl at roots ." otter pins are commonly constructed of type
Although these a r e only suggested guidelin es
and not str ict limitations, they offer some useful
assistance to the question.
C AlSI 10IO low ca rbon steel or type 302 stain-
less steel. Dimens ions of the pins a nd the
recomm e nd ed h ole s ize a r e cove r e d by ANS I

• Mark D. Hartle, P.E.

Pruitt E b e rly Ston e, Inc.
Atla n ta, GA
Standard B1B.B.1. Dimensions are also tabulated
in va riou s mac hin e de s ign books s u ch a s
Machinery's Handbook . Knowing the dime ns ions
a nd t he ma te rial (low carbon st eel or st a in less

Modern Steel Construction I May 19951 9

 .1

S TEE L NTERCHANGE
steel) one can calculate the shear strength of cotter
pin s. Cotter pins are manufactured and sold by
numerous companies. Local distributors are usual-
ly found in the Yellow pages under "Fasteners" or
"Bolts and Nuts". Usually distributors of slotted
pie spans and cantilevered ends what is the
lateral unbraced length for the bottom
flange?
Can the distance between points of
moment inflection be considered an
•
nuts, clevises and simj lar hardwa re sell cotter pins unbraced length?
even though their Yellow page advertisement may Larry Nix, P.E.
not say so. Manufacturers are \jsted in the Thomas Dallas, TX
Register under "Cotter Pins" and "Pins: Cotter".
Machinery's Handbook and the Thomas Register
can be found in many public or college libraries.
Doug Werner
Douglas Engineering
I :r :r
Westminster, CO

In a partially cover-plated column, how

would you analyze the column for governing
Vr ratio to calculate F .?
n the 1st Quarter 1979 AISC Engineering

I Journal, an artic le with a n app r oximate

method is put forward dealing with this ques-
tion. It requires the calculation of the Euler buck-
What information is available to provide
guidance in the design of a ledger angle and
ling load of the entire column by some process, typ- its connection to a wall in particular, with

•
ica lly numerical, and the identi fication of the most the bolt in tension and the lower edge of the
hi ghly st ressed segme nt du e to the axial load . vertical leg of the angle in compressive con-
Although the column wi ll buckle as a whole, the tact with the waH, what is the stress distribu-
most highly stressed segment can be used to find tion in the angle? Is only part of the angle
an effective KlIr lead ing to an a llowable axial load effective in resisting the applied loads, based
for the entire co lumn. Allowable stresses for a ll on the spacing of the bolts?
segments will fo llow. Greg Michel, P.E.
C. P. Mangelsdorf Mani Muthiah, M.S.E.
University of Pittsburgh Lescher & MahoneyffiLR Group
Pittsburgh, PA Phoenix,AZ

New Questions
VER TIC AL LOAD , N 80 TH OIlI![C Tl ONS

Listed below a re questions that we would like

the readers to answer or discuss.
If you have an answer or suggestion please send
it to the Steel Interchange Edjtor, Modern Steel Co
nstruction, One East Wacker Dr., Suite 3100, Chic
ago, IL 60601-200l.
Questions and responses will be printed in
future editions of Steel Inte rchange. Also, if you
have a question or problem t h at readers might
he lp so lve, send these to the Steel Interchange
Editor.

For a continuous trolley beam with multi-

•
10 I Modern Steel Construction I May 1995
 S NT
•
TEE L ERCHANGE
Stept Int erchange is an open forum for Modf'f"n S/eel Answers undlor question~ should be typewritten and doubl('·
Con~/ru('tlOn renders to exchange useful nnd practlcal profes· spaced. Submittals that have been prepared by word-proct's:,lOg
sional Ideas and lOformalion on all phases of steel building and arc appreciated on computer diskette (either ns n Wordpt'rfcct
bridge construction. Opinions and suggestions are welcome on file or in ASCII (onnan
Rny subject covered in this magazine. If you have 0 question or The opmions expressed In Stf!f!lln/~f'('han8f! do not nt!Ceat.88r-
problem that your fellow readers might help you to solve. please ily represent 8n official pOfHlion of the Amencan Institute of
forward it to Modern Steel ConstruC'tion. At the same time, feel Sleel Construction, Inc. nnd have not Ix>en reviewed Ill S recog-
free to respond to nny of the questions that you have read here. nized that th e design of s tructures is within the scope Bnd
Please send them LO: expertise of 8 competent licensed structural engmeer. orchltecl
Steel Interchange or other licensed professional for the application of pnnclpals to
Mode rn Steel Construction a particular structu re.
One East Wacker Dr., Suite 3100 Informalion on ordering AISC publications mentioned in
Chicago, £L 60601-2001 this article con be oblained by colling AISC at. 800/644·2400.

The following responses from previous Steel connecting the plates together?
Interchange columns have been received: n general it is best to weld a long the full length

Are there special require m ents for the

des ign of high-strength A325 or A490 bolts
I of the web so one may ignore buckling of the
individual elements. i.e. the web and flange.
One must still consider buckling according to Table
that are going to be in a high temperature B5 . 1, Limiting Width-Thickness Ratios for
area? Compression Elements, from the LRFD Manual of

N
TM A325-89. paragraph 1.2 stated in part: Steel Construction. Assuming there is no moment
"... where elevated temperature ap plications introduced into the column onc should use the min -

• re involved, Type 1 bolts shall be specified

by the purchaser."
However, this statement was removed from the
1993 update of the specification. Thi s statement
was all too encompassing, and not knowing the
actual application for the bolts, it was determined
imum weld size given in Tables J2. 3 and J2,4 of
the LRFD Manual.
If t he column is subjected to bending stresses
which may be due to eccentricities or a lateral load
the weld must be designed to transfer the load
between the web and the flange like one would do
that this statement should be removed. It is possi- for a beam. The shea r flow can be calculated using
ble that the user could place these bolts under tem- the formula:
peratures that may affect the physical properties of
t he bolts. An example being that they were not Shear Flow = VuQ kips
I, m.
designed to be used in high-pressure, high-temper-
ature service areas found in power plants. The capacity of the weld is then calculated as:
ASTM A490 specification s do not add ress the Continuous Weld Design Stre ngth = ~R""
use of these bolts in elevated temperature areas. An exa mple of this type of design can be fou nd
There are bolts manufactured for use in elevated in Chapter 11 of Sa lm o n an d J o hn so n , Stce l
temperature areas. Structures. In most cases the minimum weld size
Not knowing the specific application or d sign will control.
requirements the bolts are being used for; look into James D. PaLmer
t h e possibility of substituting these bolts with Butler Manufacturing Company
ASTM A193/A193M "Standard Specification for Grandview, MO
Alloy teel and Stainless Steel Bolting Materials
for High-Temperature Service" and A TM A449 For a continuous trolley beam with multi-
"Standard pecification for Quenched and ple spans and cantilevered e nds what is the
Tempered teel Bolts and Studs" late ral unbrac e d length for the bottom
Tom Lovick flange?

•
Industrial Steel ne answer published in the July 1995 issue
Mims, FL

If a W-shaped column is made up of three

O suggests that the lateral unbraced length is
si mply twice the canti lever dista nce. A more
co mpl ete an d exact soluti on to this problem is
welded plates, how does one design the welds offered in a 3rd Qua rter 1985 Engineering J ou rna l

Modern Steel ConstructIOn I November 1995, 9

 5
•
TEE L NTERCHANGE
pa per by N. Stephe n Ta nner "Allowa ble Be nding must be done of the resistance of welding between
Stresses for Overha ngi ng Monora ils." By consider- th e sheet a nd reinforcement ("Co ligon" stresses),
ing the ratio of the overhangi ng s pa n to the adja- a nd possibl e buckling due to weld spacing in t he
cent interior s pa n in developed equa t ions, a less line of stress.
conservative answer may be computed. Miguel A. Vades Traian
Nestor lwankiw Buenos Aires, Argentina
AlSC, Inc.
Chicago,lL

When considering a point load on the N EW Q UESTIONS

standing leg of an angle, what provisions are
there for determining the effective allowable Listed below a re questions t ha t we would like
member width? the readers to answer or discuss.
he following two a rticles will give a practical If you ha ve an answer or s uggestion please send

T approach including fini te element study a nd

the latter is a theoretical method fo r solving
the problem of how to di stribute a point load on a
it to the Steel Inte rcha nge Edi tor, Modern Steel
Construction, On e East Wacke r Dr., Sui te 3100,
Chicago, IL 60601-2001.
Qu es tion s a nd res ponses will be printed in
shelf a ngle.
Tid e, R.H . R a nd No rb e r t V . Krogsta d , fut ure editions of Steel Interch a nge. Also, if you
"Economkal Design of Shelf Angles," Proceedings, h ave a question or probl em th a t rea de rs mi gh t
Symposium on Masonry: Design a nd Construction, he lp so lve, se nd t hese to the Steel In ter cha nge
Probl e ms a nd Re pa ir, Miami , FL , Decembe r 8, Editor.
1992, STP 1180, May 1993, American Society for

•
Testing and Mate ri a ls, Philadelphia, PA Is there any criteria, except direct field
J a ramill o, T.J ., "Defl ections a nd Moments Due measurements by drilling holes, to determine
to a Concentra ted Load on a Ca ntilever Plate of the percent loss of capacity in steel bridge
Infinite Le ngth ." J ournal of Appli ed Mecha nics, members due to weather exposure for the
Ma r ch 1950, Am e r ica n Soci e ty of Mec h a ni ca l purpose of rating the truck capacity of
Engineers, New York , NY bridges.
R.H.R. TiM Mike Alomari
Wiss, Janney, Elstner Associates, Inc. Wayne County
Northbrook, IL Sterling Heights, MI

Given a wall of sheet metal or plate sub- Where should a control joint be located in
jected to fluid pressure and stiffened by same a composite large composite floor? Should it
size paralJel members spaced regularly, what be located over the top of either the girders
section (or width) of the wall shall be used or the beams? What happens to the strength
that contributes to the section of a stiffener? of the shear studs if the concrete cracks over
The stiffening member may be a flat bar, an the shear studs? Does this crack go all the
angle, or a channel or any other section. way through the slab to the top of the steel
beam?

T
he section of wall tha t contribu tes to the sec-
tion of a stiffener is defin ed by means of a n
effecti ve width be which sha ll not exceed: Can any beam be cambered without heat-
a) The geometri c condition , that is the di sta nce ing? Is there a slenderness li mit for the web
between center line of adjacent bea ms. to prevent buckling of the web while cold
b) The shear lag condition, which may be esti- cambering?
mated as 'I, of the effective beam spa n (length of
positive moment a rea of the rib). Is it acceptable to either mechanically gal-
c) The stabil ity condi tion of the plate between vanize or hot d i p galvanize high strength
stiffeners (see "Specifica tion for the Design of Cold
Form ed Stee l S tructural Membe rs", AISI, 1986,
B2 .1).
With the effective width so defin ed a verification
bolts? Are there different requirements for
the installation depending on how the bolt is
galvanized?
•
10 I Modern Sleel Construction I November 1995
• S TEE L NTERCHANGE
Steel Interchang e is an open forum for Modern Stee l
Construction readers to exchange useful and practical profes-
sional ideas and information on all phases of steel building and
bridge construction. Opinions and suggestions are welcome on
any subjecL covered in this magazine. If you have a Question or
Ans wers and/or questions should be typewritten and double-
s paced. Submitta ls that have been prepared by word -processing
arc appreciated on com pute r diskette (either as a Wordperfect
file or in ASCII format).
The opinio ns expressed in Sleel l lllerchange do not necessar-
problem that your fellow readers might help you to solve, please ily represent an official position of the American Institute of
forward it to Modern Steel Construction. At the same time, feel Steel Construction , [ncoand have not been reviewed . It is recog-
free to respond to any of the questions that you have read here. nized that the design of structures is within the scope and
Please send them to: expertise of 8 co mpetent li ce nsed structural engineer, architect
Steel Interchange or other lice nsed professional for the app li catio n of principals to
Modern Steel Construction a particular structu re.
One East Wacker Dr., Suite 3100 Information on orderi ng AISC publications mentioned in
Chicago, IL 60601·2001 this article can be obtained by calling AlSC at 800/644 ·2400.

The following responses from previous Steel moment without any factor of safety, L is the can-
Intercha nge columns have been received: tilever length, K is an efTective length factor, E is
the modulus of elasticity, G is the shear modulus,
For a continuous trolley beam with multi- I is the ntinor axis moment of inertia, and Cw is
ple spans and cantilevered ends what is the the warping constant, and J is the tor·sional con-
lateral unbraced length for the bottom stant. Both J and C. are provided in the AISC
flange? Can the distance between points of Manuals for sta ndard wide flange and S shapes.
inflection be considered an unbraced length? The value of K varies depending on the re traint

•
cond;tions at the root and at the tip of the can-
tilever, as well as the location of the load with
res pect to the neutral axis ( as indicated by figure
5.11 of the above reference). For the case in ques-
tion, where the cantilever is continuous over the
root with only top flange laterally restrained at the
root, no latera l restraints at the tip , and bottom
p flange loading, the reference suggests a value of K
of3.0.
This will result in a value for the critical buck-
ling moment. An appropriate factor of safety, typi-
e have been involved in the design of cally in the range of 1.67 to 2, should be applied too

W many monorail and bridge crane systems

that had s imilar cantilever conditions.
Since the number of the systems investigated was
obtain the a llow able moment. In addition, this
allowable moment s hould be limited to 0.66 of the
yield moment for compact sections and 0.6 of the
very large, we did some research in this particular yield moment for non-compact sections.
problem, and we are preparing a paper for publica- In efTect thi s method gives an unbraced length of
tion of the findings. 3.0 times the cantilever length , and there is no
If the beams are doubly symmet ric sections, need to use the unhraced length to the infl ection
s uch as wide flanges and S shapes, one suggested point. We should stress the fact that this method
solution is given in the Guide for Stability Design does not apply to s ingly sy mmetri c bea ms, i.e.
Criteria for Metal Structures, edited by T .V. patented track , that are frequently employed for
Galambos, section 5.2.4 page 168. The procedure trolley support.
gives the critical buckling moment, M" , for the Hussain Shanaa, Ph.D., P.E.
cantilever to be: Jehangir Rudina, P.E.
where, M" is the theoretical critical buckling AEC Engineering, Inc.

•
Minneapolis, MN
yt' EC
1+ "
(KL) ' C)

Modern Steel Construction 1 October 1995/ 9

 S TEE L
G ive n a wall of s h eet metal or plate s ub-
j ected to fluid pressure and stiffened by same
size parallel members spaced regularly, what
section or (or width) of the wall shall be used
NTERCHANGE
Storage, revised Edition 1976 provides a table for
the section for the section moduli of the stiffening
ring sections based on the 16t effective projection
on each side of t he stiffener.
•
that contribute s to the section of a stiffener? Isaac Gordo", P.E.
The s tiffening m e mber may be a flat bar, an Ang Associates, Inc.
angle, a channe l or any othe r section_ Philadelphia, PA

, ,
~"
It! I
"
1
I

:/ " '" I " -__........

....._-
,- - ..
--..
I j
,-- -:::-
M . __
10 •

~--~~
...
_ _ co.._

..
I. •

·'M _.,.I"••
" ........ ' ..
ro. ..." .. lin, I. ..
I' • ."

l .. , ... , .
••- ••
"-
, -f:'"
,
t== .... c
. ..
""""... "'"' ... "' •
·....... . . ...
I ...... .
I,. I.
, - .. ."
J ... J ... , .

. "' .... . ---,

., • 2(...,)
'
~ ) 0' ...
........
• .. , 100M

.». ••
........
• .. J
-
, .......
... .
..
....
,. .. .
..
••
•••
,,,
..

~
110

• .,»In
I.
I•

, ,•
,,. ,'
•e

~
"

·......... .. '.'" ...

,~

he efTective width contributing plate section

..........
.. 1'1 ... ",. '"
IN I ••"
>1'
., 'n
•• ,~

T
,.~

•
~ _ _ ....... II

should be limited to the width thickness ... ..,

'wJ ........ UN ' ...

... .....,.. I. ,' . I...

!. "j" ".
' ". "",. ')I,
oon
" '• • • "'_

ratios for compression elements as found in

Table B5.1 of the AlSC Allowable Stress Design
.......
IO.J .. , ' •
... , .. M

I":ro. ..
, ~
""
• __
,tat
.,_

.,,.
_ :IIU
II_

1lIt!
D.o .. , ,. . . . . .
I.
, ..

, ...
II . . .
_"
'''l " . .
,u
:11011
,~

J' __
'0

Specification for Structu ral Steel Bu ildings. As a

...... II" "0'
.. .., ••
"'"" ...
..
:II,' Q~'
bending member, the maximum bit ratio should be
..
•• "' • • w ...
limited to less than 95 / .fF" to be considered as 'l.,k===:==~11T ;: ......... " ,,-
oJ • . .. , " •••

.....,;.; .::
,, ... "" ""
...... ..
......-
.. N ... n~ .. .,
o.

--
fully efTective. A general rule of thumb is to consid- ,.
.
.. " Pit . . . . ..
. . .~ I ~

... .,
..... -._,.. -. ..•
er a total plate width contribution of 32t for struc- ,'" ,,_ ..... t •• , .. "

,
tures comprised of A36 steel, with a corresponding .. ..,.
I . . . . . . . . , •• , iN.

allowable bending stress of O.6F, .

"-
.
..
,, .........
... ., ......
......... aM . . . ,
aU '.N un
...,. '
~ ..

The figure depicts these recommended limits. •

Vincent E. Kokal, P .E.
Alliance Engineering, Inc.
Richmond, VA

ANOTHER RESPONSE: Questions:

T
he effective projection of the plate on either Has any engineering firm e ve r d esigned a
side of the stiffener being in contact with the multi-s tory unbrace d fram e u s ing mainly
plate should be 16 times the thickness of the semj-rigid (partially restrained ) connections?
plate: Thus, b. =t + 32t2 • Which, if a ny, computer programs we r e use d
This common practice to obtain a transformed to a ssis t in the analysis and des ign? What are
section has been widely used in the design of tanks some of the major pitfalls in u s ing partially
for liquid storage per standards by the American res trained mome nt c onnections?
Petroleum Institute (API). Michael G. Klozik

•
The American Iron and Stee l Institute in its Medford,MA
publication entitled Steel Tanks for Liquid

10 I Modern Steel Construction I October 1995

,
,):>

• S TEE L
Steel Interchange i s an open forum for Modern Steel
NTERCHANGE

Construction readers to exchange useful and practical profes-

sional ideas and information on all phases of steel bu ilding and
bridge construction. Opinions and suggestions are welcome on
any subject cove red in thjs magazine. If you have a question or
An swers and/or questions should be typewritten and dou ble-
spaced. Subm itta ls that ha ve been prepa red by word-processing
are appreciated on computer diskette (either as a Wordperfect
fil e or in ASCII format).
The opinions expressed in Steel Interchange do not necessar-
problem that your fellow readers might help you to solve, please ily represent a n officia l position of the American In stitute of
forward it to Modern Steel Construction. At the same time, feel Steel Construction, Inc. an d have not been reviewed. Il is recog-
free to respond to any of the questions that you have read here. ni zed that the design of structures is within the sco pe an d
Please send them to : expertise of a competent li censed structural engineer, architect
Steel lnterchange or other licensed professional for the appli cation of principals to
Modern Steel Construction a particular structure.
One East Wacker Dr., Suite 3100 In fo rm atio n on ordering AISC publications mentioned in
Chicago, IL 60601-2001 thi s article can be obtained by calling Al SC at 800/644-2400 .

Treatment of Simple Shear tions. Recent research on the Tee framing connec-
tions h as led to a formula (AISC Manual LRFD
Connections Subject to Combined 2nd Ed. , Vol. II , p. 9-170) which can be used to
Shear and Ax ial Forces assess the resistance to fracture (ductility) of dou-
ble angle shear connections. The formula is

~
ITS NAME rMPLIES, A SIMPLE SHEAR CONNEC-
TION IS INTENDED TO TRANSFER SHEAR LOAD
UT OF A BEAM while allowing the beam to db l'lti!1 = O.1631f F,b (bL'' + 2 )
act as a simply s upported beam. The most com-
mon simple sh ear connection is the double angle where:

•
connection with angles shop bolted or welded to the db is the minimum bolt diameter (A325 bolts) to
web of the carried beam and field bolted to the car- preclude bolt fracture under a s imple beam
rying beam or colum n . This note will deal with end rotation of 0.03 radian, and
this connection. I, is the angle thickness
Under shear loa d, the double angle connection is b is the di stance from the bolt line to the k dis-
flexible r ega rding the simple beam end rotation , tance of the angle
because of the angle leg thickness and the gage of (see Fig. 1)
the field boIt s in the angle legs. Th e AISC L is the length of the connection angles.
Manuals (A.S .D. 9th Ed. p. 4-9, LRFD 2nd Ed . Vol.
II, p. 9-12 ) r ecommend angle thickn esses not
exceeding 5/, in. with the usual gages. Angle leg Figure 1
thickn esses of 1/. in . to 1/, in. are generally used, - - F'ekI Bolts
with 1/, in. angles us ually being sufficient for the
heaviest load. When this connection is subjected to
axial load in addition to the shear, the important
limit states are angle leg bending and prying
action. These tend to require that the angle thick-
ness increase or the gage decrease, or both , and
these requiremen ts compromise the connection's
ability to remain fl exible to simple beam end rota-
tion . This lack of connection flexibility causes a
tensile load on the upper field bolts which could
lead to bolt fracture and a progressive failure of the
connection and the reSUlting collapse of the beam . Shop---
To the author's knowledge, there has never been a

...•
b
reported failure of this type, but it is perceived to

• be possible.
Even without the axial load, some shear connec-
tions are perceived to have this problem under
shear alone. These are the single plate shear con-
nections (shear tabs) and the Tee framing connec-
Note that this formula can be used for ASD and
LRFD designs in the form given above. It can be

Modern Steel Construction / September 1995/ 9

 5 TEE L NT E R C HANG E
used to develop a table (see Table 1) of angle thick-
nesses and gages for various bolt diameters which
can be used as a guide for the design of double
New Questions
angle connections subjected to shear and axial ten-
Listed below are questions that we would like
sion. Note that Tab le 1 validates AISC's long-
the readers to answer or discuss.
standing recommendation (noted above) of a maxi-
If you have an answer or suggestion please send
mum 5/8 inch angle thickness for the "usual"
it to the Steel Interchange Editor, Modern Steel Co
gages. The usual gages would be 4 1/, to 6 ' /, in.
nstruction, One East Wacker Dr., Suite 3100, Chic
Thus for a carried beam web thickness of say '/,
ago, IL 60601-2001.
in. , GaL will range from 2 in. to 3 in. Table 1 gives
Questions and responses will be printed in
a GaL of 2 ' /, in. for 3/, in. bolts (the most critical
future editions of Steel Interchange. Also, if you
as well as the most common bolt size). Note also
have a question or problem that readers might
that Table 1 ass umes a significant simple beam
help solve , send these to the Steel Interchange
end rotation of 0.03 radian, which is approximately
Editor.
the end rotation that occurs when a plastic hinge
forms at the center of the beam. For short beams,
beams loaded near their ends, beams with bracing
gussets at their end connections, and beams with
light shear loads, the beam end rotation will be p r
small and Table 1 does not apply.
Table 1
estimated Minimum Angle Gages (GOl) for ~~! Angles and
{! Hilt !!I \
A325 Bolts for Rotatlona' Flexiblli '-- ? --1

•
ANGU; MINIMUM GAGE Of ANGLE (GO I.),
TlII C KN ESS
(In.) " , in. dill. boll "~I in. di .. bull I in. du.. bolt
(In.) (In.) (In.)

", PI, 1'1, I".

'I, "'. I", 1'1. Wh e n co n s id eri n g a p oi nt l o ad o n t h e
'I, 2". 2'1, I". standing leg o f a n a ngle , wha t p rovision s a r e
'I. 3' 1, 211/ .. 2'/ .. t h ere for d e te rmining the e ffective a llowable
I 6 4'1"" 3% m emb e r width?
~c"""",,->,-.... _ _ GOL
D avid Ch ida
E lectric P ower Door
Hibbing MN
The design of double angle connections subjected
to shear and axial tension, can be accomplished as
shown in the following AlSC publications.
1. AlSC Manual (ASD 9th Ed. ), p. 4-94, Ex 34,
where the beam web plays the same role as
the gusset of this example.
2. AlSC Manual (ASD 9th Ed.ILRFD 1st Ed.)
Vol. II, pp. 7-123 and 124, pp. 7-125 and 126,
pp. 7-167 through 170.
3. AlSC Manual (LRFD 2nd Ed. ), Vol II, pp. 11-
38 through 42.
L Lu
Ii

While the design is being completed in the usual

When is it con servative t o select t h e b e am
way as show in these publications, Table 1 can be
s hown ass uming the unbraced le ngth of I, a nd
consulted to guide the design, if appropriate.
C b =1.0?
W.A. Th ornton

•
Roswell , GA

10 I Modern Sleel Construction I September 1.995

, S TEE L
Steel I nterchange is an open forum for Moderll Steel
NTERC H A N GE

Construction reade rs to excha nge llseful and practical profes-

s ional ideas and information on a ll phases of steel build ing and
Ans wers anNar questions s hould be tYJX'wriUC' n and double-
s paced. Submittals thul have been prcpared by word'proc{,gsing
are appreciated on computer dis keUe (e it her as H Wordpt'rfecl
bridge construction. Opinions and s uggestions are welcome on file or in ASCII fo rmnll.
any su bject covered in this magazine. If you hnv(' a question or The opinions exprc!:lscd in Sfeellfi/erchaflM(' do not necessar-
problem that your fellow readers might help you to solve, please ily repr('sc nt an official position of the Amc ri ca n Inslitut(' of
forward it to Modem Steel COllstfuction. At lhC' same time, feci Steel Construction, Inc. a nd have not Ix>cn reviewed . It is r('COg-
free U> respond to any of the qu('stions that you have read here. n ized that t h(' des ign of st ructures is within the seo p(' an d
Pleas£' send them to: expertise of a co mpetent licensed s tructural enginee r. arc hitect
Steel Inter change or other li censed professional for tilt' application of pnncipal s to
Mod ern Steel Cons tru ction n particular s t ructu re.
One East Wac ker Dr., Suite 3100 In fo rm ation On orde rin g AISC publications mentioned in
Chicago, IL 60601 -2001 lhis arl icle ca n be obta ined by ca llin g AISC al 3 121670·2400 exl.
433.

Th e following respon ses from previous S teel Needless to say that all loads from the column
Interchange columns h ave been received: shou ld be removed before extens ion of the existing
footing takes place.
V ijc£y P. Khasat, P.E.
C linton, OH

C.h,p (,tn1Gr-t!lc In what in s tances, if a n y, and unde r wha t

to fr,- ...... " cri te ri a ca n the attachme nt o f g r ating with
Sj.,fA'" kti _
m ech a nical fa s te n e r s be u sed to provide lat-
e r a l b r acing to t h e compression fl a nge of the
m e mbe r s s upporting the gra ting in applica-
t io n s s u c h a s walkways and catwalks?

T
he Am e rican National Standard,
ANSIINAAMM MBG 531-93, M eta l Bar
Grating Manllal, 5th Edition, which covers
steel, s tainless steel a nd aluminum grati ng, 1"0-
vides exa mp les of anchorages to u sc to usc in
il L installations where gra ting is s ubj ect to remova l.
Locations of these cl ips are s uggested also.
Thi s sta ndard also de fin es the three types of
gr ating as fo llows:
- R ivetted - Grating composed of straight bear-
ing bars and be nt connecting bars, which are
PLAN - ORllSolNAL joined at their contact points, by riveting.
- We lde d -Gratin g in which th e bearing bars
FI6iU/~E £
and the cross bars are joined at all of their inter-
sections by either a resistance weld or conventional
hand welding.
- P r ess u re-loc k e d - Press u re -locked mea n s
Wh at is th e m ost e fficient w ay to e nla r ge bearing ba rs are locked in position by cross bar
an exis ting foot in g, w h e n ne w load i n g c ondi- deformation instead of riveting or welding. Several
t ion s a pply? proven methods are:
1) Expansion of extruded or drawn tubular cross

~
oncePtual arrangement for e nlarging an bar;
exis ting footing for new loading conditions is 2) Extruded cross bar d e for med or swaged
hown in the accompanying figure s (above). between bearing bars;

I Pier legs ca rry additional load which is trans-

ferred to the new footing by shear keys and dowels
as s hown . Des ign bearing pressure underneath
both footings s hould be as uniform as poss ible.
3) Press assembly of recta ngular cross bars into
s lotted bearing ba rs.
The type of grating as defined above, the rela-
tive s ize of Cross bars to bearing bars, th e s pan -

Modern St.eel Construction 1 April 1995/ 9

 5 TEE L NTERCHANGE
depth ratio of the bearing bars, the lack of both
theoretical and empirical data, and the possibility
New Questions
t
of the grating itself being r emoved, a re reasons
NAAMM does not encourage the use of meta l bar
grating to provide lateral torsional support.
Obviously, there is some support provided, but Li sted below a re questions that we would like
the design provisions have not been established. the readers to answer or discuss.
The Metal Bar Grating Division of NAAMM is If you have an answer or suggestion please send
interested in knowing of any documented tests of it to the Steel Interchange Editor, Modern Steel Co
beams relying on metal bar grating to provide sup- nstruction, One East Wacker Dr., Suite 3100, Chic
port against lateral torsional instability. ago, IL 60601-200l.
Edward R. Estes, Jr., P.E. Questions and responses wi ll be printed in
National Association of future editions of Steel Interchange. Also, if you
Architectural Metal Manufacturers have a question or problem that readers might
Chicago, IL help solve, send these to the Steel Intercha nge
Editor.
What is the most efficient and cost-effec-
tive way to connect a steel wide flange girder For fire waH construction, building codes
to a concrete column? say the wall shall have su ffi cient stability
under fire conditions to allow for collapse of
n the Dece mber 1994 Steel Interchange, one construction on e ither side without collapse

I proposed solution showed a detail with a steel

beam extending through the width of the con-
of the wall. In a tied fire wall application, a
flexible anchor or break-away connection is
crete column . Connections similar to this have in
fact been used in several composite framed struc-
tures in the US a nd J apan for cases where large
recommended to laterally stabilize the wall
and under fire conditions to let go and not to
pull down the wall due to the collapse of the
I
bending moments are transferr ed between the structure on the fire side. What is the opti-
steel beams and reinforced concrete columns. In mum detail (effectiv e and economical) for
addition, over the last ten years, there have been this type of connection? (If a melted anchor is
numerous tests of such connections conducted in not a preferred option.)
the US and Japan to evaluate the effectiveness of Nai-Jang Wen
variou s joint details. For further inform ation and Belcan Engineering Group, Inc.
additional references on s uch connections, readers Cincinnati, OH
should cons ult the following document that was
prepared by a task comm itt ee of the ASCE
Committee on Composite Construction : Guidelines
for Design of Join ts Between Steel Beams to fire wal l
Reinforced Co ncrete Columns, ASCE Journal of
Structural Engineering, August 1994, Vol. 120, No. , / ; ; roof 0' fl"", deck not shown
8, pp. 2330-2357.
G,.egory G. Deierlein / / =ndary st~
Cornell University
Ithaca, NY

primary stccl

10 1 Modern Steel Construction I April] 995