Beam-Column Base Plate Design—
Beam-Column Base Plate Design—
LRFD Method
LRFD Method
Ric
Richarhard d M. M. DraDrake ke is is PriPrincincipal pal StrStructucturaural l EngEngineineer, er, FluFluoror Daniel, Irvine, CA.
Daniel, Irvine, CA.
Sharon J. Elkin is Structural Engineer, Fluor Daniel, Irvine, Sharon J. Elkin is Structural Engineer, Fluor Daniel, Irvine, CA. CA. 1 1 2 2 3 3 4 4 4 4 INTRODUCTION INTRODUCTION RICHARD M. DRAKE and SHARON J. ELKIN RICHARD M. DRAKE and SHARON J. ELKIN
II
B B N N b b d d f f m m N N . . d d m m n n M M P P V V B B . . bb n n x x t t d d x x f f t t Fig. 1.Fig. 1. Base Plate Design VBase Plate Design Variableariabless
Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ o o oo oo oo o o oo o o o o oo o o o o o o oo o o o o oo o o oo oo oo o o o o oo oo oo o o oo o o o o oo oo oo o o o o oo o o o o oo o o o o oo o o o o oo oo oo oo o o o o oo o o oo oo oo oo o o oo o o o o o o o o o o oo o o oo oo oo o o o o oo o o o o oo o o o o oo o o oo o o o o oo oo oo oo oo oo o o o o oo o o o o oo o o oo o o oo o o oo o o o o oo o o oo oo oo o o oo o o oo oo oo o o oo oo oo o o o o oo o o oo oo oo o o oo o o oo oo oo where: where: t is
t is c c mm mm n dn desiesign gn prapracticctice t e t desdesign ign a ba builduilding ing r sr strutruc-
c-base
base plate wplate width pidth perpenerpendicular dicular t t m m ment ment direc- direc-ture
ture beam-beam-c c lumn lumn with with a m a m ment-ment-resistinresisting g r fixr fixed bed base.ase.
ti ti n, n, in.in. Theref
Theref re the bre the base plate ase plate and anand anch ch r r r r ds musds must be capt be capableable
ba
basese plplateate lenlengtgthh papararallellell t t m menm mentt didirerecti ncti n,, inin.. f trans
f transferferrinring shear l g shear l adsads, axial l , axial l adsads, and bend, and bending m ing m
--c
c lumn flanlumn flange widthge width, in., in. men
ments ts t t the the supsupp p rtinrting g f f undundati ati n.n.
verall c
verall c lumn deplumn depth, in.th, in. T
Typicalypicallyly, , these beam-c these beam-c lumn base lumn base plates have plates have beenbeen
anc
anch h r r r r d disd distantance fr ce fr m c m c lumlumn and bn and base pase platelate de
desisigngned aned and/ d/ r anar analylyzed bzed by usiy using seng servrvicice l e l adads s r byr by
cen
centerterline line parparalleallel t l t m m menment dirt directi ecti n, in, in.n. appr
appr ximatinximating the stresg the stress relati s relati nship asnship assuminsuming the c g the c m-
m-base plate bearing interf
base plate bearing interface cantilever directace cantilever directi i nn pr
presessi si n bean bearinring l g l catcati i n. n. ThThe auth rs prese auth rs presenent an t an ththerer
par
paralleallel l t t m m menment dt direirecti cti n, n, in.in. ap
appr achpr ach,, ususiningg fafact ct reredd l l adadss didirerectctlyinlyin aa memeth th dd c c nsnsis is--ten
tentt wiwithth ththee eqequauati nti ns s ff ststatiaticc eqequiuiliblibririumum anandd ththee LRLRFDFD 0 950 95
(1) (1) Specifi Specificati cati n.n. 2 2 The
The m ment-m ment-resresistiisting ng basbase e plaplate te musmust t havhave e desdesignign
bas
basee plaplatete beabearinringg inteinterfarfacece cancantiletileverver perperpenpendic- dic-st
strerengngththss inin exexcescess fs f ththee rereququireiredd ststrerengngthths,s, flexflexururalal ( ( ),),
ula
ular r t t m m menment t dirdirecti n, inecti n, in.. ax
axiaial l ( ( ), ), anand d shsheaear r ( ( ) ) f f r r alall l l l ad ad c c mbmbininatati i nsns.. A typic
A typical beamal beam-c -c lumlumn base plan base plate ge te ge metmetry is sh ry is sh wnwn
0 80 0 80 in Fig
in Figure 1ure 1, whi, which is c ch is c nsinsistenstent with tt with that sh hat sh wn wn n pagn pagee
(2) (2) 2
2 11
11-61 -61 f thf the LRFe LRFD MD Manual.anual.
base plate tens
base plate tensi i n interfacn interface cantilever pae cantilever parallel trallel t m
m menment dit direcrecti ti n, inn, in..
(3) (3) 2
2 22 c
c lumn flanglumn flange thicknese thickness, in.s, in. Th
The e pr grespr gressi si n n f f bebeamam-c -c lulumn mn l l adadiningsgs, , in in rdrder er f f in in--creasin
creasing m g m ments, ments, is preis presented sented in f in f ur l ur l ad casead cases.s. Case A
Case A is a l is a l ad case ad case with axwith axial c ial c mpresmpressi si n and n and shearshear,, with
with ut bendut bending m ing m ment. Thment. This case resuis case results in a full lenlts in a full lengthgth unif
unif rm pressurm pressure distribre distributi uti n between thn between the base plate ande base plate and the supp
the supp rtinrting c g c ncrncrete. Thiete. This s cascase e is summais summarizerized in d in thethe LRFD
LRFD ManuaManual l beginnbeginning ing n pan page 1ge 11-54 1-54 and and is suis summa- mma-rized
rized herein herein f f r c r c mpletenmpleteness.ess. Cas
Case B ev e B ev lvelves fr s fr m Casm Case A be A by thy the ade additditi i n n f a sf a smallmall bending m ment. The m ment changes the full length bending m ment. The m ment changes the full length uni
unif f rm prrm pressessure dure dististribributi uti n t n t a para partial ltial lengength unth unif if rmrm pr
pressessururee didistrstribibututi n,i n, bubutt isis n tn t larlargege en ugen ughh t t caucausese sesepa pa--rati
rati n betwn between theen the base e base plate aplate and thnd the supe supp p rting rting c c ncretencrete.. Ca
Case C ese C ev v lvlves fes fr r m Cam Case B bse B by thy the ade addiditi ti n n f a spf a spe- e-cific bend
cific bending m ing m ment such thment such that the unif at the unif rm pressrm pressure dis-ure dis-tribut
tributi i n in is ths the sme smallest allest p p ssible ssible length length with with ut sut separateparati i nn f f u u u u uu f f f f f f
5
5
CASE A: NO MOMENT—NO UPLIFT
CASE B: SMALL MOMENT WITHOUT UPLIFT
M P e M M e P P P N M N e Y N e N Y e Y
Fig. 2. No Moment - No Uplift
Fig. 3. Small Moment Without Uplift
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between the base plate and the supp rting c ncrete. This 1. Assume that the resultant c mpressive bearing stress c rresp nds t the c mm n elastic limit where any addi- is directly under the c lumn flange.
ti nal m ment w uld initiate separati n between the base 2. Assume a linear strain distributi n such that the an-plate and the supp rting c ncrete. ch r r d strain is dependent n the bearing area
Case D ev lves fr m Case C by the additi n f suffi- strain.
cient bending m ment t require anch r r ds t prevent 3. Assume independent strain distributi n. separati n between the base plate and the supp rting c
n-All three meth ds summarized by AISC assume a lin-crete. This is a c mm n situati n f r fixed base plates
ear triangular distributi n f the resultant c mpressive in structural ffice practice. That is, a rigid frame with a
bearing stress. This implies that the beam-c lumn base fixed base plate will usually attract en ugh bending m
-plate has n additi nal capacity after the extreme fiber ment t require anch r r ds t prevent uplift f the base
reaches the c ncrete bearing limit state. The auth rs pr -plate fr m the supp rting c ncrete.
p se that a unif rm distributi n f the resultant c mpres-sive bearing stress is m re appr priate when utilizing LRFD.
If there is n bending m ment r axial tensi n at the base Case B, a beam-c lumn with a small m ment and n f a beam-c lumn, the anch r r ds resist shear l ads but uplift at the base plate elevati n, is sh wn in Figure 3. are n t required t prevent uplift r separati n f the base The m ment is expressed as l cated at s me ec-plate fr m the f undati n. Case A, a beam-c lumn with centricity ( ) fr m the beam-c lumn neutral axis.
n m ment r uplift at the base plate elevati n, is sh wn in Figure 2. 0 (4) 0 0 6 If the magnitude f the bending m ment is small relative
t the magnitude f the axial l ad, the c lumn anch r
0
r ds are n t required t restrain uplift r separati n f 6 the base plate fr m the f undati n. In service, they nly
2 resist shear. They are als necessary f r the stability f
the structure during c nstructi n.
(5) AISC addresses three different variati ns f the elastic 2
meth d when using an ultimate strength appr ach f r the
where: design f beam-c lumn base plates subjected t bending
bearing length, in. m ment. u u u u u u u u
3
1 CASE C: MAXIMUM MOMENT WITHOUT
UPLIFT
CONCRETE BEARING LIMIT STATE
LRFD Specification Requirements
CASE D: MOMENT WITH UPLIFT N M e P P N M M N e e P P N M P N e N Y N e N Y N P P N P . f A
Fig. 5. Moment With Uplift
Fig. 4. Maximum Moment Without Uplift
Ј Ͻ Ͻ Ͻ Ͻ Ϫ Ϫ Յ o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o oshear. Case D, a beam-c lumn with sufficient m ment t cause uplift at the base plate elevati n, is sh wn in Figure 5. This is the m st c mm n case in design practice, espe-The maximum m ment with ut base plate uplift is
as-cially f r rigid frames designed t resist lateral earthquake sumed t ccur when the c ncrete bearing limit state is
r wind l adings n the building r structure. reached ver a bearing area c ncentric with the applied
l ad at its maximum eccentricity. If the eccentricity ex-ceeds , the tendency f r uplift f the plate is assumed t
6
ccur. This assumes a linear pressure distributi n in acc r-dance with elastic the ry and n tensi n capacity between the base plate and supp rting c ncrete surfaces. Case C, a beam-c lumn with the maximum m ment with ut uplift at the base plate elevati n, is sh wn in Figure 4.
(4) 0 6 (4) (7) 6 0
6 T satisfy static equilibrium at the c ncrete bearing limit state, the centr id f the c ncrete bearing reacti n ( ) must be aligned with the line- f-acti n f the applied axial 6
l ad.
2 2
6
2 The LRFD Specificati n defines the c ncrete bearing (6)
3 limit state in Secti n J9.
(8) When the m ment at the beam-c lumn base plate exceeds On the full area f a c ncrete supp rt:
, anch r r ds are designed t resist uplift as well as
0 85 (LRFD J9-1) 6 u u u u u u u u p u c p p c
1 2 1 1 2 2 1 1 1 2 2 1 1 2 1 2 1 2 2 1 2 2 1 2 1 2 2 1 1 2 2 1 1
Case B: Small Moment Without Uplift
Practical Design Procedure—Required Area
Case C: Maximum Moment Without Uplift
Case D: Moment with Uplift Case A: No Moment - No Uplift
A BY A P . f A A Y N e A A P . . f BY . . f BY A A P qY P q N e f A A q A A y y e e P e N P M P P M P e N e q A BY A q . f B . f B A Y N A q . . f B . . f B A A P . . f BY . . f BY BY A q . f B . f B A A P . f B N . f B N B N P . qN A N A M P e P M . qN A A P M f B f A BN A P . f BY qY A A P . . f BN . . f BN A M e P P qN
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Ј Ј Ј Ј Ј Ј Ј Ј Ј Ј Ј Ј Ј Ј Ј Ј Ј Ј Ϫ Յ Յ Յ Յ Յ Ϫ Յ Յ Յ Յ Յ Յ Յ Յ Յ Ն Յ Յ Յ Յ o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o oOn less than the full area f a c ncrete supp rt:
0 85 (LRFD J9-2)
( 2 )
2 (0 60)(0 85) (0 60)(0 85) (2)
where:
c mpressi n resistance fact r = 0.60 ( 2 ) (12)
specified c ncrete c mpressive strength, ksi
N te that equati n 12 is n t a cl sed f rm s luti n be-area f steel c ncentrically bearing n a c ncrete
cause; supp rt, in.
maximum area f the p rti n f the supp rting is a functi n f , surface that is ge metrically similar t and c n- is a functi n f , centric with the l aded area, in. is a functi n f , and
is a functi n f .
H wever, if is defined as s me fixed distance r as Select base plate dimensi ns such that: s me percentage f , the c rresp nding maximum values
f and can be determined directly. (8)
And n ting that:
(9) As previ usly stated, Case C is the situati n where uplift is imminent and .
F r c nvenience, define a new variable, , the c ncrete
6 bearing strength per unit width (K/in).
0 85 0 85 (2) 2 (6) 3 (0 60)(0 85) (0 60)(0 85) (2) (0 60)(0 85) (0 60)(0 85) (2) 0 51 1 02 (10) 2 2 051 102 2 3 3
F r m st c lumn base plates bearing directly n a c n- 3 crete f undati n, the c ncrete dimensi n is much greater
than the base plate dimensi n, and it is reas nable t 0 667 (13) assume that the rati 2. F r m st c lumn
( )
6 base plates bearing n gr ut r a c ncrete pier, the c
n-crete (gr ut) dimensi n is equal t the base plate
dimen-0 111 (14)
si n, and it is reas nable t c nservatively take the rati 1.
Given the f ll wing:
, , , , , inches & kips
0 85 (15) (0 60)(0 85) (0 60)(0 85) (2) (4) (11) p c u c c u c u c u u u u c p u u c c c c c c u c c c c u c c u u u u u u u c c c p c c u c c u u u
3 vertical 2 2 2 2 2 2 2 2 2 2 2 ⌺
ANCHOR ROD SHEAR AND TENSION LIMIT STATES
LRFD Specification Requirements
Required Strength
Practical Design Procedure—Rod Sizes
T Y F T P P V F A T qY P T F A T F . f N Y P f P e f F . f N Y qY f P e f V qY N qY . qY f P e f F A q N T Y q f Y P e f F f V Y f A aY bY c F b b ac Y a F q f q f P f e Y f N N P f e V Y f f f q A T Y T qY P Y N Y V qY f P e f V . F A
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Ϫ Յ Ϫ Յ Ϫ Յ Ϫ Ϫ Ϫ Յ Ϫ Ϫ Ϫ Ϫ Ϫ Ϫ Ϯ Ϫ Ϯ Ϫ Ϫ Ϯ Ϫ Ϫ Ϫ Ϫ Ϫ Յ o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o oTw equati ns will be needed t s lve f r the tw un-kn wns, the required tensile strength f the anch r r ds,
, and bearing length, .
T maintain static equilibrium, the summati n f
verti-cal f rce must equal zer : The LRFD Specificati n defines the anch r r d (b lts) shear and tensi n limit states in Secti ns J3.6 and J3.7,
0 and Tables J3.2 and J3.5.
0 (21)
(16) (22)
F r ASTM A307 b lts: T maintainstatic equilibrium, the summati n f m ments
taken ab ut the f rce must equal zer : 59 1 9 45 (Table J3.5) F r ASTM A325 b lts, threads excluded fr m the shear
( ) 0 plane:
2 2
117 1 5 90 (Table J3.5) ( ) 0 (17) where:
2 2
required anch r r d shear strength, kips anch r r d resistance fact r 0 75
( ) 0
n minal shear strength, ksi
2 2
anch r r d n minal (gr ss) area, in. required anch r r d tensile strength, kips ( ) 0 (18)
2 2 n minal tensile strength, ksi
anch r r d shear stress, ksi This is in the f rm f a classic quadratic equati n, with
unkn wn . (23)
0 (19) F r A307 b lts:
24 ksi (Table J3.2) 4
F r A325 b lts when threads are excluded fr m the shear 2
plane:
60 ksi (Table J3.2) 4 [ ( )]
2
The shear stress ( ) is calculated c nsidering the required shear strength f the c lumn base.
2 ( )
(20) (24)
2 2
where: T determine the ther unkn wn, , substitute the value
number f r ds sharing shear l ad, unitless f r int the equati n:
N te that all the base plate anch r r ds are c nsidered (16)
effective in sharing the shear l ad. As a check, back substitute the value f r int the
equati n: ( ) 0 (17) 0 75 (25) 2 2 u u u c p ub v b u u ub t b u t v c p u t v u ub u v b ub u t v ub v b v v q N N u q v u ub v v b u v u u u u ub v b v
2 2 8 9 3 6 2 2 7 3 2
BASE PLATE FLEXURAL YIELDING LIMIT STATE
LRFD Specification Requirements
Required Strength—Tension Interface
Required Strength—Bearing Interface
Nominal Strength V F . A m M f T T . F A n M f f db n n M f c m n n c M f n F c n M M M M M x M T x M M B m n f t M M F P M
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Ј Ј Ј Ј Ϫ Յ Յ Յ o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o oo o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o oOn secti n parallel t c lumn flanges: 59 1 9 45 (26)
(29) 2
0 75 (27)
On secti n parallel t c lumn web: where:
(30) number f r ds sharing tensi n l ad, unitless 2
N te that all f the base plate anch r r ds are n t c n- where: sidered effective in sharing the tensi n l ad. F r m st base
c ncrete bearing stress, ksi plate designs, nly half f the anch r r ds are required t
resist tensi n f r a given l ad c mbinati n. The bearing pressure may cause bending in the base plate The embedment, edge distances, and verlapping shear in thearea between theflanges, especiallyf r lightly l aded c nes f the anch r r ds int the c ncrete mustbe checked c lumns. Yield line the ry is used t analyze this c n-t assure n-than-t n-the design n-tensile sn-trengn-th als exceeds n-the siderati n.
required tensile strength. This check sh uld be in acc
r-dance with the appr priate c ncrete design specificati n, (31) 4
and is bey nd the sc pe f this paper.
Itsh uldbe n tedthatbase plateh les are ften versized ( )
(32) withrespectt the anch r r ds. Inthiscase, s me“slippage”
2 may be necessary bef re the anch r r d shear limit state
is reached. F r large shear l ads, the designer may ch se Let the larger f , , and : t investigate alternate shear transfer limit states inv lving
pretensi ned b lts, fricti n and/ r shear lugs.
(33) 2
where:
yield line the ry cantilever distance fr m c lumn The entire base plate cr ss-secti n can reach the specified
web r c lumn flange, in. yield stress ( ).
largest base plate cantilever, in.
N te that f r m st base plate ge metries, the cantilever dimensi n ( ) is very small and “c rner bending” f the TheLRFDSpecificati n definesthe flexural yieldinglimit
base plate is neglected. When the dimensi n is large t state in Secti n F1.
acc mm date m re anch r r ds r m re bearing surface, c rner bending plate m ments sh uld be c nsidered and (28)
used in the base plate thickness calculati ns. (LRFD F1-1)
where:
The tensi n n the anch r r ds will cause bending in the required base plate flexural strength, in-K base plate f r the cantilever distance .
flexural resistance fact r = 0.90 F r a unit width f base plate: n minal flexural strength, in-K
plastic bending m ment, in-K
(34)
The bearing pressure between the c ncrete and the base
F r a unit width f base plate: plate will cause bending in the base plate f r the cantilever
distances and . The bearing stress, (ksi), is calculated
(35) c nsidering the required axial and flexural strength f the 4
c lumn base, and respectively. ub t b p pl u t ub b t p pl t p , f , p pl p pl y n b pl n p pl b n u p pl p p n p y u u
( ) 2 2 ( ) ( ) 2 ( ) 2 ( ) ( ) ( ) 2 3 ( )
Practical Design Procedure—Bearing Interface Case D: Moment with Uplift Base Plate Thickness
Practical Design Procedure—Tension Interface Base Plate Thickness
DESIGN EXAMPLE 1
Case A: No Moment—No Uplift
Case B: Small Moment Without Uplift
Case C: Maximum Moment Without Uplift
P f BY t M M T x t . M M BF t Y m c f . F P t . c BY F f t . c F Y m P m t . BF M M t T x . F B T x t . BF P f BN P t . c BN F P P f BY B N e P t . c B N e F P P . P f BY B N BN m . . P t . c x . BN F
Fig. 6. Design Example 1
Required: Solution:
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Յ Ն Ͼ Յ Ն Ն Ͻ Ϫ Ն Յ Յ Ն Ն Ϫ Ն Ϫ Ϫ Ն Ϫ o o o o o o o o o o o o (44) Setting the design strength equal t the n minal strengthand s lving f r the required plate thickness ( ):
F r all cases: (28) 2 11 (45) (LRFD F1-1) If : 0 90 2 4 1 49 (46) 1 49 (36) If : 2 11 (47)
Setting the design strength equal t the n minal strength and s lving f r the required plate thickness:
(28) 0 90 4 2 11 (37) (38) 1 49 (39) (40) ( 2 ) 1 49 (41) a) Design anch r r ds ( 2 )
b) Determine base plate thickness
1. Dimensi ns: 1 5 (42) 22.0 in. 0.95(12.12 in.) 5 24 in. (1) 2
1 5 16.0 in. 12.12 in. 0.605 in.
1 49 (43) 2 24 in. (3) 2 2 2 u p p n b pl u p req n p y p p y u p req y p p req y Y u p req y p b pl p u y u p req y u p u p req y u u p u p req y u u u p u p req y
2 3 4 2 2 2 5 ( ) 2.27 in. 2 ( )
Select: Base Plate 2 20 1’-10
o.k. DESIGN EXAMPLE 2
o.k.
o.k. Select: 4 - 3/4 in. Diameter Anchor Rods
e . N . . e, Case D q . q . N f . f e . . . Y . . . . . . T . . V F A . V . F . . T F A . T Y . . m, n n P . M t . m . t . x . controls
Fig. 7. Design Example 2
Required: Solution:
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Ј ϫ ϫ Ͻ Ͼ Ϯ Ϫ Ϯ Ϫ Ϫ Ͼ Ϫ Ͼ Ͻ Ϫ Ϫ Ϫ o o o o o o o o o o o o o o o o o o o o o o o o 2. Eccentricity:6. Check bearing n c ncrete bel w gr ut layer 120 ft-K(12 in./ft)
11 08 in. (4) The gr ut is 2 in. thick. Assume that the c ncrete 130K
extends at least 2 in. bey nd gr ut in each directi n. 22.0 in. 3 67 in. 11 08 in. (7) 6 6 (24 in.)(6.67 in.) (0 51)(4 ksi)(20.0 in.) (10) (20 in.)(2.27 in.) 3. C ncrete bearing:
76.6 K/in. 61.2 K/in. used in design Assume the bearing n gr ut area will g vern.
(0 51)(6 ksi)(20.0 in.) 1 61.2 K/in. (10) 16.0 in. 22.0 in. 19 0 in. 2 2 2 16.0 in. 11 08 in. 19 08 in. 2 2(130)(19 08) 19 0 (19 0) (20) 61 2 19 0 16 73 2 27 in. 61 2 K/in.(2.27 in.) 130 K 8.92 K (16) 4. Anch r r d shear and tensi n:
Check 4 in. dia. anch r r ds 30 0 K 7.50 K (25) 4 0 75(24 ksi)(0.4418 in. ) 7.96 K 7.50 K 7 50 K 59 1 9 26 7 ksi (26) 0.4418 in. 8.92 K 4.46 K (27) 2
a) Determine required tensile strength 0 75(26.7 ksi)(0.4418 in. )
b) Determine base plate thickness 8.85 4.46 K
N te that this pr blem is Example 16 fr m the AISC C lumn Base Plate Steel Design Guide Series.
5. Base plate flexural yielding:
1. Required strength: (LRFD A4-2) 2 27 in. 5 24 in. and n t applicable
1.2(21K) 1.6(39K) 87.6K
(8 92 K)(2.24 in.) 1.2(171 in.-K) 1.6(309 in.-K) 700 in.-K 2 11 0.35 in. (45) (20.0 in.)(36 ksi) 2. Dimensi ns: 14.0 in. 0.95(7.995 in.) 3 20 in. (1) (130 K) 5.24 in. 2 211 (47)
(20.0 in.)(36 ksi) 11.0 in. 7.995 in. 0.435 in.
1 72 (3) 2 2 2 1.82 in. u ub v b ub t ub t b ub u u p req p req
3 2 5 ( ) 2.45 in. 2 ( ) 14 5 14 14 1 2
SUMMARY AND CONCLUSIONS
Required Tensile Strength 17.3 K
REFERENCES
Select: Base Plate 1 14 1 -2
NOMENCLATURE e . N . . e, Case D q . N f . f e . . . Y . . . . . . T .
Design Of Welded Structures
Y . . m, n n
Structural Steel Design, LRFD Approach .
t . .
.
Man-t .
ual Of Steel Construction, Load & Resistance Factor Design
controls
Col-umn Base Plates
Engineering Journal,
Design .
Of Anchor Bolts In Petrochemical Facilities . Engineering Journal . Engineering Journal . A
ԽԽ
Ί
Ί
Ί
Ί
Ј Ј Ј Ј Ͻ Ϯ Ϫ Ϫ Ϯ Ϫ Ͻ Ϫ ϫ ϫ ϫ ϫ ϫ ϫ o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o3. Eccentricity: f r the design f the anch r r ds is slightly smaller because the centr id f the c mpressi n reacti n is 700 in.-K
7.99 in. (4) a greater distance fr m the anch r r ds. 87 6 K
14.0 in.
2 33 in. 7 99 in. (7)
6 6 A meth d l gy has been presented that summarizes the
4. C ncrete bearing: design f beam-c lumn base plates and anch r r ds using fact red l ads directly in a manner c nsistent with the (0 51)(3 ksi)(14 in.) 4 42.8 K/in. (10) equati ns f static equilibrium and the LRFD Specifi-cati n. Tw design examples have been presented. A 11.0 in. 14.0 in.
12 5 in. direct c mparis n was made with a pr blem s lved by
2 2 2
an ther AISC meth d.
11.0 in. The step-by-step meth d l gy presented will be benefi-7 99 in. 13.49 in.
2 cial in a structural design ffice, all wing the design prac-titi ner t use the same fact red l ads f r the design f the 2(87 6)(13 49)
steel structure, base plate, and anch r r ds. In additi n the 12 5 ( 12 5) (20)
42 8 unif rm “rectangular” pressure distributi n will be easier t design and pr gram thanthe linear “triangular” pressure 12 5 10 05 2 45 in.
distributi n utilized in all wable stress design and ther 42 8 K/in.(2.45 in.) 87.6 K 17.3 K (16) published LRFD f rmulati ns.
5. Base plate flexural yielding: 1. Bl dgett, Omer W., ,
1966. 2 45 in. 3 20 in. and n t applicable
2. Smith, J. C., ,
2nd Editi n, 1996. (17 3 K)(1.72 in.)
2 11 0 51 in. (45) 3. American Institute f Steel C nstructi n (AISC), (14.0 in.)(36 ksi)
“L ad and Resistance Fact r Design Specificati n f r Structural Steel Buildings”, December 1, 1993. (87 6 K) 3.20 in. 4. AmericanInstitute f Steel C nstructi n (AISC),
211 (47)
(14.0 in.)(36 ksi)
, 2nd Editi n, V lume 2, 1994.
1.24 in. 5. American Institute f Steel C nstructi n (AISC), , Steel Design Guide Series, 1990. /
6. Shipp, J.G., and Haninger, E.R., “Design Of Headed
6. C mparis n: Anch r B lts,” V l 20, N . 2,
AISC s luti n f r this pr blem: (2nd Qtr.), pp 58-69, AISC, 1983.
7. American S ciety f Civil Engineers (ASCE), Required Anch r R d Tensile Strength 21 2 K
,pp4-3t Select: Base Plate 1 / 14 1 -2 4-8, 1997.
Length f triangular c mpressi n bl ck 5 1 in. 8. Th rnt n, W. A., “Design f Small Base plates f r Wide-Flange C lumns,” , V l 27, Auth r’s s luti n f r this pr blem:
N . 3, (3rd Qtr.), pp 108-110, AISC, 1990a.
Required Anch r R d Tensile Strength 17 3 K 9. Th rnt n, W. A., “Design f Small Base plates f r Wide-Flange C lumns - A C ncatenati n fMeth ds,” Select: Base Plate 1 / 14 1 -2
, V l 27, N . 4,(4thQtr.), pp108-Length f rectangular c mpressi n bl ck 110, AISC, 1990b.
2 45 in. Remarks:
area f steelc ncentricallybearing n a c ncrete The auth rs’ s luti n yields the identical base
supp rt, in. plate size and thickness. Required tensile strength
u
p req
2 2 2 A d e f A B f f F f F m F M n M M n M q N t P t P x T T V V Y b c
ն
ն
Ј Ј o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o omaximum area f the p rti n f the supp rting c lumn verall depth, in. surface that is ge metrically similar t and c n- axial eccentricity, in.
centric with the l aded area, in. anch r r d distance fr m c lumn and base plate anch r r d n minal (gr ss) area, in. centerline parallel t m ment directi n, in. baseplate width perpendiculart m ment direc- specified c ncrete c mpressive strength, ksi
ti n, in. c ncrete bearing stress, ksi
n minal tensile strength, ksi anch r r d shear stress, ksi
n minal shear strength, ksi base plate bearing interface cantilever parallel specified minimum yield stress, ksi t m ment directi n, in.
n minal flexural strength, in.-K base plate bearing interface cantilever perpen-plastic bending m ment, in.-K dicular t m ment directi n, in.
required base plate flexural strength, in.-K yieldlinethe rycantileverdistancefr mc lumn web r c lumn flange, in.
required flexural strength, in.-K
c ncrete ( r gr ut) bearing strength per unit base plate length parallel t m ment directi n,
width, kips/in. in.
c lumn flange thickness, in. n minal bearing l ad n c ncrete, kips
base plate thickness, in. required axial strength, kips
base plate tensi n interface cantilever parallel t required tensile strength, kips
m ment directi n, in. required anch r r d tensile strength, kips
anch r r d resistance fact r = 0.75 required shear strength, kips
flexural resistance fact r = 0.90 required anch r r d shear strength, kips
c mpressi n resistance fact r = 0.60 bearing length, in.
number f r ds sharing tensi n l ad, unitless c lumn flange width, in.
number f r ds sharing shear l ad, unitless largest base plate cantilever, in.
b c p t v v y n p pl u p f p u u ub u b ub c t f v
