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8/16/2019 Computer Program for Simulation of Wall Construction Sequence
1/90
us
Army
Corps
o f
Engineers©
Engineer
Research
and
Development Center
Computer-Aided
Structural
Engineering
Project
User's
Guide:
ompute r
Program
fo r
Simulation
o f
Construct ion
Sequence
fo r Stiff Wall Systems with
Multiple Levels
o f
Anchors (CMULTIANC)
William
P .
Dawkins,
Ralph
W.
Strom,
Robert
M .
Ebeling
August
2003
Approved for public
release;
distribution
is
unlimited.
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
2/90
Computer-A ided
Structural
RDC/iTL SR-03-1
Eng ineer ing Project
ugust
2003
User's
Guide:
omputer
Program
fo r
Simulation
o f
Construction
Sequence
fo r
Stiff Wall Systems
with IVIultiple
Levels
o f
Anchors (CMULTIANC)
William P .
Dawkins
5818
Benning
Drive
Houston,
TX
7096
Ralph
W.
Strom
9474
S.
E.
Carnaby W ay
Portland,
OR 7266
Robert M .
Ebeling
Information
Technology
Laboratory
U.S.
Army
Engineer
Research an d
Development
Center
3909
Halls
Ferry Road
Vicksburg,
M S
9180-6199
Final
report
Approved for
public release;
distribution
is
unlimited
Prepared
for
U.S.
Army
Corps
of
Engineers
Washington,
DC
20314-1000
Under
ork
Unit
31589
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
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AB S T RACT :
his report describes th e PC-based
computer
program C M U L T I A N C , used to evaluate th e
effects
of staged
construction
activities i.e.,
xcavation
nd
tieback
post-tensioning)
on
wall
nd
oil
behavior. T he
C M U L T I A N C simplified
construction sequencing
analysis is applicable
to
stiff walls with a
single ro w or multiple rows of post-tensioned tieback anchors. Top-down construction is assumed in this
analysis procedure.
T he
retaining
wall
system
is
modeled using
beam
on
inelastic
foundation
methods
with
elastoplastic
soil-
pressure
deformation
urves R -y
urves)
used o
epresent
he
oil
behavior.
T he R -y
urves
re
developed
within
th e
C M U L T I A N C
program
in
accordance
with th e reference deflection
method.
T he
retaining
wall
is
analyzed
on a
per-unit
length ru n ofwall basis.
One-dimensional
finite
elements
ar e
used
to
model th e retaining wall with closely spaced inelastic concentrated springs
to
represent soil-to-structure
interactions on
both
sides of th e wall. Discrete concentrated, elastoplastic springs ar e used
to
represent th e
anchors.
For each
evel
of excavation (associated
with a
particular
tieback installation) C M U L T I A N C
performs
three
equential
nalyses:
a)
taged xcavation
nalysis to
he
xcavation
evel
needed
or
nchor
installation)
to
capture soil loading effects,
(b )
R -y curve shifting
to
capture plastic soil movement effects,
and
(c )
tieback
installation
analysis
to
capture
tieback
anchor
prestressing
effects.
R -y
curves
are
shifted
to capture th e plastic movement that takes place
in th e
soils
as th e wall displaces toward th e excavation
fo r
those conditions
where
actual wall
computed displacements
exceed
active
computed displacements.
R -y curve hifting s necessary
to
properly apture oi l eloading effects s tieback nchors re post-
tensioned
and th e wall
is
pulled
back
into
th e
retained
soil.
D I S C L A I M E R :
h e contents
of
this report
are
not
to
b e
used
fo r
advert i s ing, publ ica t ion, or promot iona l pu rposes .
Citat ion
of
t rade
n a m e s
does n ot constitute
an
official
endorsement or approval of th e use of such c ommerc i a l products .
A ll
product
n a m e s
an d t rademarks
cited
are
th e property of
thei r respect ive
o wn e rs . h e f ind ings
of this report are
n o t
to b e construed as an
official
Depa r tment of th e A r m y posi t ion unless so designated by oth e r authorized
d o cume n t s .
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
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Contents
C o n v er s io n Factors , Non-SI to
SI Unit s
of
M e as u re m e nt v ii
Preface
ii
1—Background o n T i e b ack Retaining
Wall
Systems
1.1
es ign
of
Flexible
Tieback Wall
Systems. . . . . .
1.2
De s i gn
of
Stiff
Tieback
Wall
Systems
1.2.1
dent i fy ing
stiff w al l
sys tems
1.2.2 Tieback w al l pe r fo rm ance
object ives
1.2.3
rogress ive
des ign
of t i eback w al l
sys tems
1.3
IGID
Method
1.4 R I G I D
2
M e t h o d 0
1.5 W IN K L E R M e t h o d 0
1.6
W IN K L E R
2
M e t h od
1.7
NLFEM M e t h od 2
1.8 Factors
Affect ing
Analys is M e t h o d s
an d
Resul t s
2
1.8.1 verexcavat ion
2
1.8.2
round
anch or
pre loading
3
1.9
Cons t ruct ion
Lo n g - T er m ,
Cons t ruct ion
Shor t -Term,
an d
Pos tcons t ruct ion
Condi t ions
3
1.10
ons t ruct ion-Sequencing
An a l y ses 4
2 — C o m p u t e r
Program C M U L T I A N C 6
2.1 nt roduct ion
6
2 .2 Discla imer
6
2.3
ystem
Overview
6
2 .4 A nch ors ̂
2 .5 xcavat ion
Elevat ions
7
2 .6 o il Profi le
8
2.6.1
n it weights
8
2.6 .2
t rength
proper t i es
8
2 .7
Water
8
2 .8 Vertical
Surcharge
Lo a d s 9
2 .9 Limi t ing
Soil
an d
Water
Pressures 9
2.10 Calcu lat ion
Points 9
2.11 ctive and Pass ive
Pressures
0
2.11.1 ndrained
( cohes ive)
soils 0
2.11.2
Dra i ne d
( cohes ion less)
soils
0
2.11.3 ressure
coefficients 0
III
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2.11.4
Profiles
with
interspersed
undra ined
and
dra ined
layers 2
2.11.5 ressures
d ue
to
surcharge
loads
2
2.12 Water
Pressures
2
2.13 Nonlinear Soil
an d
A n c h o r
Spr ings
2
2.14
Displacements
at Limit ing Forces 4
2.15
hifted
Soil
Spring
Curves
5
2.16
A n c h o r Spr ings 5
2.17
Finite
Element
M o d e l
8
2.17.1
ypica l
e l em en t 8
2.17.2
ypica l
n o d e
9
2.18 xterna l
Suppor t s
9
2.19 M e t h o d
of
Solut ion 9
2 .20
tabil i ty
of
Solut ion 0
2.21
om pu t e r Program
0
2 .22
n p u t D a t a Files
1
2.23 utpu t Dat a File
'
^3 1
2 .24
Graphics
2
2.25
onstruction
Sequence
Simula t ion
2
2.25 .1 npu t
data
2
2 .25 .2 tage
1 : nitial
cond i t ions
2
2.25 .3
tage 2 :
olut ion
fo r
init ial
cond i t ions
3
2 .25 .4 tage
3: hift
of SSI
curves
. 33
2 .25 .5
tage
4:
olut ion
w ^ i t h
shif ted
SSI
curves 3
2 .25 .6 tage
5: o p
a n c ho r instal lat ion 3
2 .25 .7 tage
6: xcavat ion
3
2 .25 .8 ubsequent stages 3
2 .26
Unit s
a nd
Sign
C o n v en t io n s 4
3 — E x a m p l e
Solut ions 5
3. 1
nt roduct ion
5
3.2
ole tanche Wall
' ZZZ ''Z 35
3 .3
onnevi l le
T y p e Wall
1... .'... . 46
3 .4
CacoiloWall
.m.'. . .50
References 5
Ap p en d ix
A :
uide
fo r
D a t a Input l
A.l nt roduct ion l
A . 1.1
ource
of
input
l
A .
1.2
Dat a
edit ing
l
A.1.3
npu t
data file genera t ion
l
A .
1.4 ec t ions
of
input
l
A.l.5
redef ined
data
file 2
A .2
ead ing
3
A .3 Wall
S eg m en t
D a t a 3
A .4 Anchor Data
3
A .5
oil
Profile
D a t a
4
A .6
nit ial
Water
D a t a
6
A .7
Right -S ide
Surface
Surcharge
D a t a
6
A .8 xcavat ion Data
l
O
A .9 Wall
Bottom Condi t ions
l
1
I V
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
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A.IO Terminat ion ll
A ppe nd i x B: bbreviated Input Guide l
SF298
List of F ig ures
Figure
1-1. Defini t ion of span
length
Z ,
Figure
2-1.
Schemat ic of
wall/soi l
sys tem
7
Figure
2-2 .
Log-spi ra l
pass ive
pressure
coefficients
(after
De par t m e n t
of th e
Navy
1982) 1
Figure
2-3. ressure
calculat ions
for surcharge
loads
3
Figure
2-4.
ater
pressures
4
Figure
2-5 .
onlinear
soil
spr ings 4
Figure
2-6 .
oncent rated
soil
spr ings
5
Figure
2-7 .
hifted
SSI soil
spr ings 6
Figure
2-8 .
onlinear a n c ho r spr ing 6
Figure
2-9 .
inite e l em en t
m o d e l 8
Figure
2-10.
ypica l e l em en t
8
Figure
2-11.
ypical
node
9
Figure
3-1.
ole tanche wa l l
5
Figure
3-2.
nput file
fo r
Soletanche
w al l 6
Figure
3-3.
choprint
of
input data
fo r
Soletanche wall 7
Figure
3-4 .
nit ial l imit
pressures
for Soletanche wall
8
Figure
3-5.
nit ial
SSI curves
for Soletanche wa l l
9
Figure
3-6.
esul ts for
init ial cond i t ions
for Soletanche
w al l
0
Figure
3-7.
hifted SSI
curves
for
Soletanche
wa l l
1
Figure
3
-8 . S u m m a r y
of
resul ts
after anchor lock-off
load
fo r
Soletanche
w al l 2
Figure
3-9.
S u m m a r y
of
resul ts
fo r anch or spring replacing lock-off
load fo r
Soletanche
wall 3
Figure
3-10.
Lim i t pressures
after
excavat ion
to eleva t ion
-30 fo r
Soletanche wa l l 4
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
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Figure
3-11.
eft-side
SSI
curves after
excavat ion
to
eleva t ion
-30
fo r
Soletanche
wal l 4
Figure
3-12.
u m m a r y
of
resul ts
after excavat ion
to
elevat ion
-30 fo r
Soletanche wa l l 5
Figure 3-13.
a x im a s u m m a r y
fo r
Soletanche
wa l l
6
Figure
3-14.
onnevi l le
type wa l l
s imula t ion
6
Figure
3-15.
n p u t file
for
Bonnevil le
wa l l 7
Figure
3-16.
choprint
of
input data fo r Bonnevi l l e wal l
8
Figure
3-17. ax i m a
s u m m a r y
fo r
Bonnevi l l e
wal l
0
Figure
3-18 .
acoilowall 0
Figure
3-19.
n p u t file
fo r Cacoi lo wa l l
1
Figure 3-20 .
choprint
of
input
data
fo r
Cacoi lo
wa l l
2
Figure
3-21.
nit ial
water and
soil
l imit pressures fo r initial
cond i t ions
4
Figure
3 - 2 2 . ax i m a
s u m m a r y
fo r
Cacoi lo
wal l 5
List
o f
Tables
T a b l e
1-1.
Table
1-2.
Table
1-3.
T a b l e
1-4.
T a b l e
1-5.
Table
2-1.
T a b l e
2-2 .
Stiffness
Categor iza t ion
of
Focus Wall Systems
(Strom
and Ebel ing 2001)
Genera l
Stiffness Quantificat ion fo r
F o c u s
Wall
Systems
(Strom
and Ebel ing 2001)
D es ig n
and Analys is T o o l s for
Flexible
Wall
Systems
(Ebel ing
et
al . 2 0 0 2 )
D es ig n
an d Analys is T o o l s
fo r
Stiff
Wall Systems
(Strom and
Ebel ing 2 0 0 2 )
S u m m a r y of
R -y C u r v e
Const ruc t ion M e t h o d s
(Strom
and
Ebel ing 2001)
R ef e r en c e
Displacements 5
Unit s
and
Sign
C o n v en t io n s
4
V I
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
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Convers ion Factors, Non-SI
to
SI Units o f
Measurement
Non-SI
units of
measurement
used
in
this
report
can be
converted
to
SI
units
using th e
following
factors.
Multiply By
To Obtain
feet
0.3048
meters
Inches
0.0254
meters
kip-feet
1,355.8181
newton-meters
kips
pe r
square foot
47.88026
kilopascals
pounds
(force)
4.448222
newtons
pounds (force) per square
foot
47.88026
pascals
pourids (force) pe r square inch
0.006894757
megapascals
pounds (mass)
0.4535924
kilograms
pounds (mass) per
cubic
foot
16.01846
kilograms
pe r cubic
meter
square
inches
0.00064516
square meters
tons
pe r
square foot
9,764.856
kilograms pe r square meter
VII
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
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Preface
T hi s repor t descr ibes
th e
sof tware program
C M U L T I A N C ,
n ewl y developed
to
simulate
th e
simplif ied construction
sequence
m et ho d
of
analys is
of a stiff,
t ieback
wal l
with mult iple
levels
of prestressed
anchors
( a s su m in g t o p - d o wn
construct ion).
Funding fo r this
research
w as provided
by
th e C om pu t e r -A i d e d
Structural
Engineer ing
R esea r c h
Program
sponsored
b y
Headquar ters ,
U . S .
A r m y
C o r p s of
Engineers
( H QUS AC E ) ,
as
par t
of th e
Infrastructure
T e ch no l ogy
Research a nd
De v e l opm e nt
Program.
M s.
Y a zm in
Seda-Sanabr ia ,
Geotechnica l
and
Structures
Laboratory (GSL),
Vicksburg ,
M S, U.S.
A r m y
Engineer
R esea r c h
and De v e l opm e nt
C en t e r ( E R D C ) , w as
Program
M a n a g er .
T h e
s tudy
w as
conducted u nd e r Work Un i t 3 1 5 8 9 ,
C om pu t e r -A i d e d
Structural
Engineer ing
(CASE) , for whic h
D r.
R o b er t
L .
Hall, G S L , is
Prob lem
A re a Leader and
M r. Chris
Merril l ,
Chief ,
C o m p u t a t io n a l
Science
and
Engineer ing
Branch,
Informat ion
T e ch no l ogy
Laboratory
( ITL) ,
E R D C ,
is
Princ ipa l
Invest igator. T h e
H Q U S A C E T ec hn ic a l Monitor
is M s.
An j a n a
Chudgar ,
C E C W - E D .
T hi s
report w as
prepared
b y
D r.
Will iam
P.
D a wk in s ,
Houston ,
T X;
M r.
Ralph W. Strom,
Por t l and ,
O R ;
a n d
D r.
R o b er t
M .
Ebel ing,
Engineer ing
and
Informat ic
Systems
Divis ion
(EISD),
I T L .
D r. Ebel ing w as th e
au thor of
th e
scope
of
w o r k
fo r
this
research . T h e research
w a s conducted
u nd e r
th e direct
superv is ion
of D r.
Char les
R .
Welch,
Chief ,
EISD;
and D r. Jeffery
P.
Holland,
Direc tor ,
ITL.
C o m m a n d e r an d
Execut ive
Director
of
E R D C
w as
C O L John
W.
M o r r i s
III,
EN . Director
w as
D r.
J a m es
R .
Houston .
VIII
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
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1
Background
on
Tieback
Retaining Wall Systems
T hi s report descr ibes th e personal com pu t e r ( P C )
-based com pu t e r program
C M U L T I A N C ,
used
to
simulate th e
s impl i f ied
cons t ruct ion
seq u en c e
m e t h od of
analys is
of
a
stiff t i eback
wal l .
T o p - d o w n
cons t ruct ion
is
a s su m ed in this analysis
procedure .
T h e
user's guide
to
C M U L T I A N C
is
given
in
C h ap t e r
2.
T hi s chapte r serves
as
an in t roduct ion to th e categorizat ion an d
analys i s of
flexible an d stiff t ie-
back retaining wall sys tems
involv ing
th e use
of
pres t ressed anchors .
T h e mul t i -
anch ore d
t i eback
earth
retaining
w al l sys tems
used
by
th e
U . S .
Army C o r p s
of
Engineers are classif ied
as
ei ther flexible or rigid accord ing
to
Strom an d
Ebeling
(2001,
2 0 0 2 )
and
Ebeling
e t al.
(2002) . T he
categorizat ion
of
a
t i eback
wall as
be ing
ei ther
f lexible
or rigid is used
fo r convenience in
de te rmining th e
appropria te
analys is
and/or
des ign
procedure
associated with
a
particular
type
(i.e.,
ca tegory)
of
wall .
1 .1
esign
of
Flexible
Tieback
W all
Systems
T h e
equivalent
beam
on
rigid
support
m e t h od
of
analys is
us ing
apparent
ear th-pressure
envelopes
is
m o s t often th e
des ign m e t h od
of
choice , primari ly
because of it s
ex p ed ien c y
in
th e
pract i cal des ign of
t i eback wa l l sys tems.
T hi s
m e t h od provides
th e
m o s t
rel iable
solut ion
for
flexible
w al l sys tems,
i.e.,
so ld ier
beam-lagging
sys tems
an d sheet-pile
wall
sys tems,
since
fo r
these types
of
sys tems
a
s ign if ican t
redis tribution
of
earth
pressures
occurs behind
th e wal l .
Soil
arching ,
s t ress ing of
g r o u n d anchors ,
cons t ruct ion-sequencing effects,
and
l agging
flexibility
a ll
cause
th e
earth pressures behind
f lexible wal l s
to
redis tribute to ,
an d
concent ra te
at,
anch or
suppor t
loca t ions
( F H W A- R D - 9 8 - 0 6 6 ) .
T hi s redis tribution ef fec t in f lexible
w al l
sys tems
canno t
b e
captured
by
equivalent beam on rigid suppor t
m et ho d s
o r by beam o n inelast ic foundat ion
analys is m et ho d s
w h e re th e
act ive
an d
pass ive
l imi t states
are
def ined
in
t e rms
of
R a n k in e
or
C o u l o m b
coefficients.
Full-scale
w al l
tes ts on
f lexible wall sys tems
( F H W A -R D-9 8 -0 6 6 )
ind ica ted
that th e act ive earth pressure used to
def ine
th e
minimxmi
load
assoc ia ted
with th e
so i l
springs
behind
th e
w al l
had
to
be
reduced
b y
5 0
percent
to
m a t c h
measured
behav ior .
Since
th e
apparen t
earth-pressure
d iagrams used
in
equivalent beam on rigid
support
analyses wer e
deve loped fi-om
measured loads ,
an d
thus
inc lude
th e
effects of soil arching ,
stressing of
g r o u n d
anchors ,
cons t ruct ion-sequencing
effects,
an d
l agging
f lexibil i ty ,
they
prov ide
a
Chapter
1 Background on Tieback Retaining Wall Systems
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
11/90
better
indicat ion
of
th e
strength
pe r fo rm ance
of
f lexible
t ieback
wal l
sys tems.
T hi s
is n ot th e
case fo r
*ftj5^wall
sys tems,
ho wev er ,
and
in
fac t th e
d iagrams
are
appl icab le
only
to
those f lexible wa l l
sys tems
in
w h i c h
•
verexcavat ion to
facil i tate
ground
anch or
instal lat ion
does
n ot
occur.
•
rou nd
anch or
pre loading
is
compat ib le
with act ive
l imit
state
cond i t ions .
• he water table
is be low th e base
of
th e
wall .
T he
des ign
of f lexible wal l
sys tems
is
i l lustrated
in Ebeling
et
al .
(2002) .
1 .2
esign o f
Stiff
Tieback
Wall Systems
Cons t ruct ion-sequencing
analyses are
impor tan t
in
th e
evalua t ion
of
stiff
t ieback
wal l sys tems,
since fo r such
sys tems
th e t emporary
construct ion
stages
are often
m o r e d em a n d in g
than
th e
f inal
pe rm ane n t
loading
cond i t ion
(Kerr
a n d
T a m a r o
1990) .
T hi s
m ay
also
b e
true
fo r
f lexible wa l l
sy s t em s wher e
s ign if ican t
overexcavat ion occurs
an d
fo r f lexible wa l l
sys tems
sub jec t to
a n c ho r
pres t ress
loads producing
soil
pressures
in
ex c es s
of
act ive
l imi t
state condit ions.
T he
purpose of th e
ex a m p l e p r o b l em s
conta ined here in
is to
i l lustrate
th e
use of
cons t ruct ion-sequencing analys is
fo r th e
des ign
of
stiff
t ieback wal l
sys tems.
Al t ho u g h
m a n y
types
of
cons t ruct ion-sequencing
analyses
ha v e
b een
used
in
th e
des ign
of
t ieback
wal l
sys tems,
only
three
types
of
cons t ruct ion-sequencing
analyses
are
demons t ra ted
in
th e
ex a m p l e prob lems.
T h e three
const ruc t ion-
sequencing
analyses
chosen
fo r
th e
ex a m p l e p r o b l em s
are
ones
considered
to
b e
th e m o s t
promis ing
fo r th e des ign
and
evalua t ion
of
C o r p s
t i eback wal l
sys tems:
•
quiva len t
b ea m
on
r igid suppor t s
by
c lass ica l m et ho d s
( ident if ied
as
th e
RIGID
2
m et ho d by
Strom and
Ebeling
2002) .
•
ea m
on
inelast ic
foundat ion m et ho d s using
elastoplast ic
so i l -p ressure
deformat ion
curves
(R-y
curves)
that
a c c o u n t
fo r
plast ic
(nonrecoverab le)
m o v em en t s
( identi fied
as
th e
W IN K L E R m e t h od
b y
Strom and
Ebel ing
2002) .
•
eam
on
inelast ic foundat ion m et ho d s
using elastoplast ic
soil -pressure
deformat ion
curves
(R-y
curves)
fo r th e
resist ing
side
only with
c lass ica l
soil
pressures
appl ied
on th e
dr iv ing
side
( ident if ied
as th e W IN K L E R
2
m e t h od
b y
Strom and
Ebel ing
2002) .
T h e
resul ts from
these
three
cons t ruct ion-sequencing
m et ho d s are
com pare d
in
Strom and
Ebel ing
(2002)
with
th e
resul ts obtained fi-om th e
equiva len t
beam
on
r igid
suppor t m et ho d using
apparent
pressure
load ing
( ident if ied here in
as
th e
R I G I D
method) . Recal l
that
apparent
earth
pressures
a re an
envelope of
m a x i -
m u m past pressures
encountered
ov e r a ll
stages
of
excavat ion .
T h e resul ts
are
also
c o m p a r ed
with f ield
m ea su r em en t s
an d finite
e l em en t
analyses
in Strom and
Ebeling
(2002) .
Chapter
1
Background
on
Tieback
Retaining
Wall
Systems
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
12/90
1 .2 .1
dentifying
stiff wall
systems
Five focus
w al l
sys tems
w e re
identi fied
a nd
descr ibed
in detail
in
Strom and
Ebel ing (2001):
•
ert ical
sheet-pile
sys tem with wa l es
and post-tensioned t i eback anchors .
•
oldier b e am sys tem with w o o d or reinforced
concre te
l agging a n d pos t -
tensioned tieback anchors .
For th e w o o d l agging sys tem,
a
pe rm ane n t
concre te
fac ing
sys tem is required .
• e can t
cyUnder
pile
system
with
pos t - tens ioned t i eback anchors .
• ont inuous
re inforced concre te
slurry
w al l system
with
post-tensioned
tieback anchors .
•
i screte
concre te
slurry
w al l
sys tem
(soldier
b e a m s
with
concre te
l agging)
with
pos t - tens ioned t i eback anchors .
D ef o r m a t io n s an d
wa l l
m o v em en t s in
excavat ions are a
funct ion
of
soil
strength a nd wa l l
st iffness, with
w al l
st iffness
a
function
of
structural rigidity
El
of
th e w al l
an d th e vert ical
spac ing
of
a n c ho r s L. Soil
st iffness
correlates to
soil
strength;
therefore ,
soil
strength
is
often
used in
lieu of soil
st iffness
to
charac-
terize
th e
in f luence of
th e
soil on
wa l l d isp lacements .
Steel
sheet-pile
an d
steel
so ld ier
b e a m s
with timber l agging
sys tems are cons idered
to
b e f lexible tieback
w al l sys tems. Secant
cyUnder
pile,
cont inuous
concre te
slurry wal l ,
and discrete
concre te
slurry
wa l l
sys tems are
considered
to b e stiff
t i eback w al l
sys tems.
T h e
effect
of
wall
st iffness
on
wall d isp lacements
an d
earth
pressures
is descr ibed
in
X ant h akos
(1991)
an d
in
F H W A- R D - 8 1 - 1 5 0 .
In th e F H W A report ,
it
is
ind icated
that
C l o u g h
a nd
T su i
(1974)
sho wed , by finite e lement analyses , that w al l
an d
so i l
m o v em en t s
could
b e reduced by
increas ing
wall rigidi ty
an d
tieback
stiffiiess.
None
of
th e
reduct ions
in
m o v em en t s
w e re
proport ional
to
th e
increased
stiffiiess,
ho wev er .
For
example ,
an
increase
in
wa l l rigidity
of 32
t imes
reduced
th e m o v em en t s by a factor
of
2 .
Lik ewise ,
an increase
in
th e t i eback
stiffiiess by
a
factor of 10 caused
a
5 0
percent reduct ion in
m o v em en t s .
O t h e r inves t iga tors ha v e
also
s tud ied th e ef fec t
of support
st iffness
fo r
c lays
(a s
reported
in
F H W A - R D - 7 5 - 1 2 8 ) .
T h e y def ined
sys tem
st iffness
by
EIIL'^,
w h e r e
El
is
th e
stiffiiess of
th e wa l l
and
L
is
th e
d is tance b e t w e e n
suppor t s
(F igure 1-1).
T h e m ea su r e
of
w al l
st iffness is
def ined
as a
variat ion on th e
inverse
of
Rowe's
f lexibil i ty
n u m b e r fo r wal l s ,
an d
is thus expressed by
EIIL^,
w h e r e
L is
th e vert ical
d is tance
b e t w e e n tw o
r o ws
of anchors .
Wall
st iffness
refers not only to th e
structural rigidi ty der ived f rom th e elast ic m o d u l u s
an d th e
m o m e n t
of inert ia , but also
to
th e
vert ical
spac ing of suppor t s
(i n this
case
anchors) .
It
is
suggested
by
Figure
9-106
in
F H W A -R D-7 5 -1 2 8
that ,
for
stiff
c lays with
a
stabil i ty
n u m b e r
Y///5„
equal to or less than 3,
a
sys tem
st iffness
EIIL^
of 10 o r
m o r e
w ou l d
keep
soil
displacement
equal
to
o r
less
than in.' '^
H o wev er ,
other
factors,
such
as
pres t ress level ,
overexcavat ion,
an d factors
of
'
t this t ime, th e aut hors of this repor t r e c o m m e n d that ,
when
t ieback w a l l system d isp lacement s
a re
th e
quantity
of in t e res t
(i.e., s t r ingent
d isp lacement
control
design) ,
they
should
b e
estimated by
nonlinear finite e lement -so i l st ructure interact ion ( N L F E M ) analysis .
^ table of factors
fo r
conver t ing non-S I
units
of m e a s u r e m e n t t o SI
units
is
presented
on page
vii.
Chapter
1
Background
on
Tieback
Retaining
Wall
Systems
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
13/90
s\vs\vs\
k^^V^V^S sV^\\\
Ground anchor (typ)
Figure
1-1.
efinition
of
span length
L
safety,
also
influence
displacement. Data
in
this
figure
clearly
indicate
that
stiff
wall systems in stiff clays will displace less than flexible wall systems in soft
clays.
Table
1 - 1 categorizes flexible and stiff
wall
systems with respect to th e
focus wall systems of th e Strom and Ebeling (2001) report.
Table
1 -1
Stimiess Categorization of
Focus Wall Systems (Strom an d
Ebel ing
2001 )
Focus
Tieback
Wall
System Descript ion
Wall Sti ffness Cateqorv
1
Flexible
stiff
Vertical
sheet-pile
system
V
Soldier beam
system
V
Secant cylinder pile
V
Continuous reinforced
concrete
sluny
wall
system
V
Discrete
concrete slurry
wall
system
V
Using th e approach ofFHWA-RD-75-128, th e wall stiffness ca n be quanti-
fied in terms of th e flexural stiffness El per
foot ru n ofwall and in terms of th e
relative flexural stiffness E I / L ' * . This
information
is
presented in
Table
1-2
fo r th e
focus wall systems of th e Strom
an d
Ebeling (2001)
report.
T he relative flexural
stiffness in th e table
is
based on a span length
L,
i.e., a vertical
anchor
spacing of
10
ft.
It should be
recognized
from these stiffness
calculations
that
a secant
pile
system
with
L equal
to
28.5 ft would produce
a
flexural stiffness value of^//Z,
equal
to
that for th e vertical sheet-pile wall system with L equal
to
10
ft. There-
fore, it
is
possible, by spacing anchors at close intervals, to obtain a stiff wall
system
using
flexible sheetpiling or , vice versa,
to
obtain
a
flexible
wall
system
using secant piles with widely spaced anchors.
Chapter
1
Background
on
Tieback
Retaining
Wall
Systems
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
14/90
Table
1 -2
Genera l Stif fness Quantif ication
fo r
Focus Wall
Systems
(Strom
and
Ebel inq
2001 )
Waif Sti ffness
Wall
System
El
k-ft^/ftx10*
EIIL*
ksf/fl
Flexible
Vertical
sheet-pile
system
0. 3
to
5. 0
3.7^
Soldier beam system
0.1
to 4. 0
1.5^
Stiff
Secant
cylinder
pile
8. 0 to 250.0
239.8 ̂
Continuous
reinforced
concrete slun^
wall
30.0
to
150.0 123.1
Discrete concrete
slun^
wall
35.0 to
160.0
92.3 =
Relative
stiffness
based
on
P Z
27 sheetpiling.
P er Olmsted Prototype
Wall.
^ Relative stiffness
based
on
HP12x53
soldier
beams
spaced
at 8. 0 ft
on
center
(OC).
P er
FHWA-
RD-97-130 design example.
^
Relative stiffness based
on
5.0-ft-diam caisson piles spaced at 7. 0 ft OC . P er Monongahela
River
Locl
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
15/90
r ec o m m en d a t io n s
of F H W A -R D-9 7 -1 3 0 .
Trapezoida l
earth
pressure
distr ibut ions
are used fo r this
type
of
analysis.
For stiff wal l sys tems,
act ive
earth pressures
in
th e
retained soil
can
often b e
a s su m ed an d u sed
in
a
cons t ruct ion-sequencing
analys i s
to size
anchors
and
determine
wal l
proper t ies .
Earth
pressure
distr ibut ion
fo r
this
type
of
analysis
w ou l d
be
in
accordance with
c lass ica l
earth
pressures
theory ,
i.e.,
t riangular
with
th e absence
of
a
water
table .
T h e
genera l prac t ice
fo r
th e
safety
with
e c o n o m y des ign
is to
k eep
anchor
pres t ress
loads
to
a
m in im u m consis ten t with act ive,
o r near-ac t ive ,
soil
pressure
cond i t ions
(depend ing
u p o n
th e value
ass igned
to th e
factor of safety).
T hi s
m ea n s
th e
anchor size
wo u l d
be
smaller ,
th e anch or
spac ing
larger,
and
th e
anch or
pres t ress
l o wer than those
found
in des igns
requir ing stringent
displacement control .
1.2.2.2 Stringent displacement control design.
A
pe r fo rm ance objec t ive
for
a
t i eback
wal l can b e
to
restrict
wal l and soil
m o v em en t s
dur ing
excavat ion
to
a
tolerable
level so
tha t structures
ad jacent
to
th e excavat ion
wil l
n ot exper ience
distress (a s
fo r
th e Bonnevi l l e
t emporary
t ieback
wal l
example) .
Ac c o r d in g
to
F H W A -R D-8 1 -1 5 0 ,
th e
tolerable
ground
surface
se t t l ement m ay b e
less than
0.5 in .
if
a se t t l ement -sens i t ive
structure
is
founded on
th e
sa m e
soil
u sed
fo r
suppor t ing th e
anchors .
T i e b ack
wal l
des igns
tha t are
required
to
m e e t
spec i f ied
displacement control performance
objec t ives
are
t e rmed
s t r ingent
displacement
cont ro l des igns .
Select ion
of th e
appropr ia te
des ign pressure
d iagram
fo r
deter-
mining anchor prestress
load ing
d ep en d s on th e
level
of
wal l
an d
soil
m o v e m e n t
tha t can b e tolerated. Walls buil t
with
factors
of safety
b e t ween
1.3 and 1.5
appl ied
to
th e
shea r
strength
of
th e soil
m ay
result
in
smal ler
d isp lacements
if
stiff wal l
c o m p o n en t s
are
used
( F H W A- R D - 9 8 - 0 6 5 ) .
T o m in im ize th e o u t wa r d m o v em en t ,
th e des ign wo u l d proce e d using
soil
pressures
at
a
magni tude
approach ing
at-rest
pressure cond i t ions (i.e., a
factor
of
safety
of 1.5
appl ied
to th e shear
strength
of
th e
soil).
It should b e recognized tha t
even
though th e
use
of a
factor of
safety
equal to 1.5 is
consis ten t with
an
at-rest
(i.e.,
zero
so i l -d isp lacement cond i t ion) earth
pressure
coeff i c ient
(as
s h o w n
in
Figure
3 -6 of
Engineer
M a n u a l
1110-2-2502
(Headquar ters ,
U . S .
A r m y
C o r p s
of
Engineers
1989)) ,
severa l
types
of
lateral wa l l
m o v e m e n t could
still occur.
T h e s e
inc lude cant i lever m o v em en t s
assoc ia ted with
instal lat ion
of th e fi rs t
anchor ;
elast ic
elongat ion
of th e
t endon
a n c ho r
assoc ia ted
with
a
load
increase;
anchor
yie ld ing,
creep ,
and
load
redist r ibut ion
in th e anchor b o n d zone;
and m a s s
m o v e-
ments
behind
th e
ground
a n c ho r s
( F H W A- S A- 9 9 - 0 1 5 ) .
It
also
should
be
recog-
nized
that
a
stiff rather than
f lexible wal l
sys tem
m ay b e required
to
reduce
bending
d isp lacements
in th e wal l to levels cons i s tent with th e pe r fo rm ance
objectives
es tab l ished fo r th e
s t r ingent
displacement
control
design.
A s t r ingent
displacement
cont ro l
des ign
fo r
a
f lexible wal l
sys tem,
ho wev er ,
w ou l d
result
in
anch or spac ings
that
are
closer an d anch or pres t ress
levels
that are higher than
those
fo r
a
comparab le
safety with
ec o n o m y des ign .
If
displacement
cont ro l
is a
crit ical pe r fo rm ance
objec t ive
fo r
th e
project be ing des igned ,
th e use
of
a
stiff
rather than f lexible wa l l
system should be considered .
Chapter
1
Background
on
Tieback
Retaining
Wall
Systems
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
16/90
1 .2 .3
rogressive
design of tieback
wall
systems
A s with m o s t des igns ,
a
progress ive analys i s
(start ing
with
th e
s imples t
des ign
tools and progress ing to
m o r e
c o m p r ehen s iv e
des ign
tools w h e n neces -
sary) is high ly r e com m e nd e d
by
th e
authors.
With
respec t
to
f lexible
wall
sys tems,
so m e of th e
m o r e
c o m p r ehen s iv e
analys i s
tools
used
for
stiff w al l
sys tem analysis
(cons t ruct ion-sequencing analys i s
b a sed
on
c lass ica l
earth
pressure
distr ibut ions
an d
b e am
on
inelast ic
foundat ion
analys is ) are not
g en -
eral ly
cons idered
appropr ia te
for th e
analys is
of
f lexible
w al l sys tems .
T hi s
is
because apparent pressure
d iagrams, since they
are
envelopes based on m e a -
surements m a d e
during const ruc t ion ,
inc lude th e
effects of soil
arching ,
wall
f lexibil i ty ,
pre loading
of
suppor t s ,
facial st iffness,
an d
construction
sequencing .
H o wev er ,
with stiff wa l l
sys tems,
these
i t ems wil l no t
af fec t
earth pressure
redis tribution
to
th e
sa m e
exten t
they
af fec t
f lexible wa l l
sys tems.
Therefore ,
in
pract i ce , cons t ruct ion-sequencing
analyses
and
b ea m
on
inelast ic
foundat ion
analyses
are considered valid tools
for th e invest igat ion of
stiff
wa l l
system
behav ior .
T he
des ign
a nd
analysis tools typically used in th e
des ign an d analysis
of
f lexible a n d
stiff
wa l l sys tems a re
su m m a r ized
in
Tables
1-3
a nd
1-4,
respec-
t ively,
start ing
with
th e
s imples t
des ign
tool
and
progress ing to th e m o r e c o m p r e -
hens ive analy t ica l tools.
T h e m o s t c o m p r ehen s iv e des ign tools
are
l inear elast ic
finite
e l em en t
( LE F E M )
and nonl inear finite
e l em en t
( N L F E M )
soil -st ructure
interact ion
analyses .
T h e
N L F E M
analysis
is
required
w h e n it
b e c o m e s
necessary
to verify that
th e
des ign meets
s t r ingent
displacement
cont ro l
pe r fo rm ance
object ives.
Both
th e
LEFEM
a n d
NLFEM
analyses
can be
used
to verify
safety
with
ec o n o m y
des igns .
Table 1 -3
Des ign
and
Analys is Tools
for
F lex ib le
Wall Systems
(Ebel ing
e t
al.
2002)
nalysi
s
Objective
Descript ion
Analysis iVIethod
RIGID
1
Final
design
when
performance goal is
safety with
economy.
P reliminary design
when
performance
goal
is stringent
displacement
control.
Beam
on rigid supports analysis
using
apparent
pressure "envelope" diagram.
Apparent pressure diagram based on a
total
load
approach.
Total
load
is
based
on
a
factor
of
safety
of
1. 3 applied to the
shear
strength of
the
soil
when
the
performance goal
is
safety
with
economy
Total
load
is based on a factor of safety
of 1. 5 applied to the shear strength of
the soil
when
the performance goal
is
stringent
displacement
control.
Hand
calculations
NLFEM
Final design when
performance goal is
stringent displace-
ment
control.
Nonlinear soli-structure
finite
element
construction-sequencing
analysis.
P C
SOILSTRUCT-
ALPHA
Chapter
1
Background on
Tieback
Retaining Wall Systems
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
17/90
Table 1 -4
Des ign
and Analysis
Tools
for
Stiff
Wall
Systems
(Strom
an d
Ebel ing
2002)
Analysis
RIGID
1
RIGID
2
Objective
Preliminary design tool to
estimate upper anchor
loads an d bending
moments
in
upper
region
of
wall.
Construction-sequencing
analysis
using
classical
soil pressures.
Used to estimate lower
anchor loads
an d
bending
moments in lower regions
of wall.
WINKLER
1
WINKLER
2
LEFEM
NLFEM
Description
Beam
on
rigid supports analysis using apparent
pressure
"envelope" diagram.
Apparent
pressure
diagram
based
on
a
total
load
approach.
Total
load is
based
on
a
factor
of
safety
of
1. 3
applied to the
shear strength
of
the soil
when
the performance
goal
is
safety
with economy
Total
load
is
based
on
a
factor
of
safety of
1. 5
applied to the
shear
strength
of
the
soil
when
the performance
goal
is
stringent displacement control.
Beam
on
rigid
supports analysis.
Construction-sequencing
analysis to affirm results
of RIGID
1
an d
RIGID 2
analyses.
Construction-sequencing
analysis to affirm results
of
RIGID
land
RIGID
2
analyses.
Construction-sequencing
analysis to affirm results
of
RIGID
land
RIGID
2
analyses
an d
to evaluate
3- D effects and
investigate loss of
anchor
effects.
Used
for cases where
bending effects in the
longitudinal direction are
important.
Final
design
when
performance goal
is
stringent
displacement
control.
Soil-pressure distribution by classical methods, i.e.,
Rankine,
Coulomb, etc.
Active pressures used to determine anchor loads
an d
wall
bending moments based on a factor of safety of 1. 0 applied
to
the
shear
strength
of
the
soil
when
the
perfomiance
goal
is
safety
with
economy.
At-rest
earth
pressures used to detennine anchor loads an d
wall bending moments based on
a
factor of
safety of
1. 5
applied to the
shear
strength
of
the soil when
the
performance
goal
is
stringent
displacement
control.
Passive
pressures used
to determine
anchor loads
and wall
bending
moments based
on
a factor
of
safety
of
1. 0 applied
to the
shear
strength of
the soil.
Beam
on
inelastic supports
analysis.
inelastic springs used to represent
soil
on both sides of
wall.
Inelastic springs
used
to represent anchors.
R-y
curves
shifted
to
account
for
inelastic
soil
deformations.
Beam
on
inelastic
supports analysis
inelastic springs used to represent soil
on
excavated
side
of
wall.
Classical soil pressures applied to retained
earth
side
of
wall.
inelastic springs used to represent anchors.
Plate
elements
used to represent
wall
to
capture
redistribution
effects
in the longitudinal direction of
the
wall.
Elastic
springs used to represent soil
on
excavated
side
of
wall.
Classical
soil
pressures
applied
to
retained
earth
side
of
wall.
Elastic
springs used to represent
anchors.
Nonlinear
soil-structure
finite
element construction-
sequencing analysis
Analysis Method
Hand
calculations
Hand
calculations
for determinate
systems.
CBEAMC equivalent
beam
analysis
for
indeterminate
systems.
CMULTIANC
beam
I
on inelastic supports
analysis.
CBEAMC beam
on
nonlinear supports
analysis.
Structural analysis
software with plate
element analysis
capability.
P C SOILSTRUCT-
ALPHA.
Chapter
1
Background
on
Tieback
Retaining
Wall
Systems
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
18/90
Descr ip t ions
of
th e
analys i s
m et ho d s
cited
in
Tables
1-3
a nd
1- 4
an d
used
in
th e ex a m p l e p r o b l em s
are provided in
Strom and Ebel ing
(2002) .
With respect t o
th e
W IN K L E R
b e am on inelast ic spring
analyses
cited
in these
tables,
there
are
severa l m et ho d s
fo r cons t ruct ing
th e spring
load-d i splacement
(R-y)
curves.
T hese m et ho d s
are
su m m a r ized in T a b l e 1-5
an d descr ibed in th e first ex a m p l e in
Strom
an d
Ebel ing (2002) .
Table
1 -5
Summary
o f
R-y
Curve
Construction
Methods
(Strom
an d
Ebel ing
2001 )
Method
Constant of
Horizontal Subgrade
Reaction/ Subgrade
Constant
Soletanche
Reference Deflection
Method
Descript ion
A constant of horizontal subgrade reaction method was developed by
Terzaghi
(1955) for use in the evaluation of
discrete wall systems. A
subgrade
constant
method
was
also
developed
for
continuous walls.
Interaction distances used
In
the
analysis
are
pe r
Haliburton (1981).
IVIethods
generally
provide
a
reasonable estimate
of wall moments
an d
shears, bu t
often
overestimate displacements.
FHWA-RD-81-150 presents coefficients
of
subgrade reaction based on
information obtained
from
pressure meter
tests.
Subgrade reaction values
are
a function of the shear parameters of the soil. Soletanche used beam
on inelastic foundation analyses, based on the P fister co efficient of
subgrade reaction values, to
verify
that
anchor
loads an d computed wall
displacements
me t performance objectives.
Method
reported
in
FHWA-RD-98-066 for use
in
beam
on
inelastic
foundation analyses. Displacements representing the
elastoplastic
intersection point of
the R- y curve were established for granular
an d
clay
soils.
R- y curves are shifted to account for inelastic
nonrecoverable
displacements. These investigators indicated that
th e
deflection response
estimated
by the
reference deflection method
generally underpredicted
displacements because
it
does no t account for mass movements in the
soil.
1 .3
IGID
1 Method
In
th e
R I G I D
m e t h od
(Strom and
Ebeling
2002) ,
a
vert ical
strip
of
th e
t i eback
w al l
is
t reated
as a
mult i span b e am suppor ted on rigid
suppor t s
located
at
tieback points
in th e upper region
of
th e wal l .
T h e l ow e rm os t rigid support is
as s u m e d
to
occu r a t
f inish
grade.
T h e
wa l l
is loaded on
th e
driving side
with an
apparent pressure
load ing .
In
genera l
prac t ice ,
th e
u se
of soil pressure
envelopes
as
load ings
fo r
a
b e am
on
rigid
support
analys is
provides
an
expedient
m e t h od
for th e init ial layout ,
an d so m et im es th e f inal des ign
of
t i eback
w al l
sys tems.
H o wev er ,
th e
soil pressure
envelopes ,
o r apparent
earth
pressure d iagrams, wer e
not
in tended
to
represent
th e
real
distribution
of
earth
pressure , but ins tead
consti tuted hypothe t i cal pressures .
T hese hypothe t i cal pressures w e re a bas i s
fi-om w h i ch strut loads
could b e
calculated that m i g h t b e
approach e d but wo u l d
no t
b e
ex c eed ed
dur ing
th e
ent ire const ruc t ion process .
T h e
apparent pressure loading used in th e ex a m p l e
p r o b l em s
is
in accordance
with
F H W A- R D - 9 7 - 1 3 0 .
(See
Figure
2 8
of
this
F H W A report fo r
th e
apparent
pressure
d iagram used
fo r
a wall suppor ted by
a
single row
of
a n c ho r s
an d Fig-
ure
29
fo r th e
apparent pressure
d iagram
used fo r a w al l supported by mult iple
r o w s
of
anchors . ) T hi s
informat ion
is
also
presented
in Strom
an d
Ebeling (2001,
Figures 5 .3
and
5.4) .
Chapter 1 Background on
Tieback
Retaining Wall Systems
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
19/90
R I G I D
des ign
procedures
are
i l lustrated
in th e
ex a m p l e prob lems
conta ined
in
Strom and Ebel ing
(2002)
and
in
th e
ex a m p l e
prob l e m s in
Sect ion
10 of
F H W A- R D - 9 7 - 1 3 0 .
W hen t iebacks
a rc pres t rcssed
to levels
consis ten t
with
act ive pressure
cond i t ions
(i.e.,
E x a m p l e
in
Strom and
Ebeling
2002) ,
th e
tota l
load
used to determine
th e
apparen t
earth
pressure
is
based
on
that
approximate ly
corresponding
to
a
factor
of
safety
of 1.3
on
th e
shear
strength
of
th e
soil.
W hen
t iebacks
are prestrcssed to
m in im ize
wal l displacement
(Example 2
in
Strom
an d
Ebeling
2002) ,
th e
total
load
u sed
to
determine
th e
apparen t
earth
pressure
is
b a sed on
at-rest earth
pressure
coef f ic ien t cond i t ions ,
or that
approximate ly
corresponding
to
a
factor of
safety
of 1.5 appl ied
to
th e shear
strength
of
th e soil.
Empir ica l
formulas
are
provided
with th e
appare n t
pressure
m e t h od
fo r
u se
in
est imating
anch or
forces
and wal l
bend ing m o m en t s .
1 .4
IGID
2
Method
A s
with
th e
RIGID
m et ho d ,
a
vert ical
strip of th e
t ieback
wa l l
is
t reated
as
a
mul t ispan
b ea m suppor ted on
r igid supports
located at
t i eback
poin t s
(Strom
and
Ebel ing
2002) .
T he
l o wes t
suppor t locat ion
is
a s su m ed to
b e
below
th e
bot tom of
th e
excavat ion
a t th e
poin t
of
zero net pressure (Ratay 1996) .
T w o
earth
pressure
d iagrams
are
used
in
each
of th e
incrementa l
excavat ion ,
anch or
placement ,
and prestressing analyses .
Act ive earth pressure
(o r
at-rest
earth
pressure
w h e n
wal l
d isp lacements
are
crit ical)
is
appl ied
to
th e
dr iv ing
side
and
extends
from th e
to p of
th e ground
to
th e
actual
bot tom
of
th e
wal l . Pass ive
earth
pressure
(based
on a
factor
of
safety of 1.0 appl ied to th e
shear strength
of
soil)
is
appl ied
to th e
resist ing
side
of
th e wal l
a n d
extends
from th e bot tom
of
th e
excavat ion
to th e actual
bottom
of
th e wal l .
T he
appl ica t ion
of
th e
R I G I D
2
m e t h od is
demonst ra ted
in
th e
tw o ex a m p l e
prob l e m s in Strom
an d
Ebeling
(2002) .
T he
RIGID
2
m et ho d
is
useful
fo r
de te rmining if th e
wal l
a n d anch or
capac i t ies determined
b y
th e
RIGID
analys is are adequate
fo r
stiff
t ieback
wa l l
sys tems,
an d
permit s redes ign
of
both
f lexible an d
stiff
t ieback wa l l
sys tems
to
ensure tha t strength
is
adequate
fo r
all
stages
of
const ruc t ion . N o useful
in forma-
t ion
can b e
ob ta ined
from th e R I G I D 2
analys is
regard ing displacement d em a n d s ,
ho wev er .
1 .5
WINKLER1
Method
T h e W IN K L E R m e t h od (descr ibed
in
Strom
and Ebel ing
2 0 0 2 ) uses
ideal ized
elastoplast ic
springs to represent soil
load-deformat ion
response
an d
anchor
springs
to
represent
grou nd
anch or
load-deformat ion
response .
T he
elastoplast ic
curves
(R-y curves)
represen t ing th e
soil
springs
for th e ex a m p l e
prob l e m s are
b a sed
on th e
reference
deflect ion
m e t h od
( F H W A- R D - 9 8 - 0 6 6 ) .
Other m et ho d s
are avai l ab le
for develop ing
elastoplast ic
R -y
curves
for b ea m
on
inelast ic
foundat ion
analyses.
T he
reference
deflect ion
m e t h od
( F H W A - R D - 9 8 -
0 6 6 ) ,
th e Haliburton
(1981) m et ho d ,
an d th e Pfister m et ho d
( F H W A- R D - 8 1 - 1 5 0 )
a re
descr ibed
in
th e f irst
ex a m p l e
prob lem.
Elastoplast ic curves can be shif ted
with
respec t
to
th e
undef lected
posit ion
of
th e
t i eback
wa l l to capture
non-
recoverab le
plast ic
m o v em en t s that m ay occu r in th e
soil
dur ing
var ious
con-
struct ion s tages
(e.g.,
excavat ing ,
anch or
placement ,
and prestressing
of
anchors) .
'
^
hapter
1
Background
on
Tieback
Retaining
Wall
Systems
8/16/2019 Computer Program for Simulation of Wall Construction Sequence
20/90
T hi s R -y
curve
shif t ing
w as used in both
ex a m p l e
prob l e m s
to
cons ider th e
n o n -
recoverab le
act ive
state
yielding
that occurs
in
th e retained soil
during th e first-
stage excavat ion (canti lever-s tage excavat ion) .
T h e R -y curve
shif t
fo l lowing
th e
f irst -stage
excavat ion wil l help to
capture th e
increase
in
earth
pressure
that
occurs behind th e
w al l
as
a n c ho r pres t ress
is
appl ied ,
an d
as
second-s tage ex c a v a -
t ion
t akes
place.
In th e tw o
ex a m p l e
p r o b l em s
in
Strom an d Ebeling (2002) ,
once
th e upper anchor
is
instal led,
th e
second-s tage
excavat ion causes th e
upper
sec t ion
of
th e t i eback wall to
def lec t
into th e retained
so i l—soi l
that h as previ -
ously
exper ienced
act ive
state
yie ld ing
dur ing f irst -stage
excavat ion .
T h e
WINKLER
m e t h od
is
useful
fo r
determin ing if th e wall and a n c ho r capac i t ies
de te rmined by a R I G I D or RIGID 2
analysis
are adequate ,
an d permit s redes ign
of
stiff
t i eback w al l
sys tems
to
ensure that strength
is adequate
fo r a ll
stages
of