Struktur Beton
PracetakPrategang
Beton Bertulang VS Beton Pracetak
Advantage & Disadvantage discussion?..
Manufacturing of Precast Concrete Elements
Manufcturing of Precast Concrete Elements
Casting bed
Manufacturing of Precast Concrete Elements
Reinforcing Steel (Stressing, Pre/Post)
Manufacturing of Precast Concrete Elements
Casting/Compacting
Casting Hollow Core Planks
• Once the concrete has
cured to sufficient
strength, the castings
are cut into sections of
desired length (above).
• In some cases,
transverse bulkheads
are inserted to divide
the casting bed into
sections before concrete
is placed. In this case,
only the prestressing
strands need to be cut
to separate the sections
(below).
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Manufacturing of Precast Concrete Elements
Moulding Removal
Casting Hollow Core
Planks
• Individual sections
are lifted from the
casting bed (right)
and stockpiled to
await shipping to
the construction
site.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Manufacturing of Precast Concrete Elements
Erection/Stockpiling/Erection
Casting Hollow Core
Planks
• Precast concrete
elements are
shipped to the
construction site by
truck and erected
on site by crane.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Precast Elements (Slab)
Precast Concrete Slabs
• Used for floor and roof decks.
• Deeper elements (toward the
right below) span further than
those that are shallower
(toward the left).
• Right: Hollow core slabs
stacked at the precasting plant.
Fundamentals of Building Construction, Materials
& Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Precast
P P
Elements
RECAST, C
(Beam/Girder)
S
RESTRESSEDE ONCRETE TRUCTURAL LEMENTS
Precast Concrete Beams and Girders
• Provide support for slabs.
• The projecting reinforcing bars will bond with
concrete cast on site.
• Right: Inverted tee beams supported by precast
columns.
Fundamentals of Building Construction, Materials
& Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Precast
P P
Elements
RECAST, C
(Columns/Wall
S E
RESTRESSED
Panels)
ONCRETE TRUCTURAL LEMENTS
Precast Concrete
Columns & Wall Panels
• Provide support for
beam and slab
elements.
• Since these elements
carry mainly axial
loads with little
bending force, they
may be
conventionally
reinforced without
prestressing.
• Or, long, slender
multistory elements
may be prestressed
to provide resistance
to bending forces
during handling and
erection (columns at
right).
Fundamentals of Building Construction, Materials & Methods, 5 th Edition
Copyright © 2009 J. Iano. All rights reserved.
Precast Elements (Wall Panels)
Precast Concrete Columns
and Wall Panels
• Precast concrete wall
panels may be solid
(right), hollow, or
sandwiched (with an
insulating core).
• Wall panels can be
ribbed, to increase their
vertical span capacity
while minimizing weight,
or formed into other
special shapes (below).
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Precast Elements (Stairs/Stadium)
Other Precast Concrete
Elements
• Precast concrete stairs
(below)
• Uniquely shaped structural
elements for a sports
stadium (right)
• Etc.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Precast
P P
Elements
RECAST, C
(Assembling
S
RESTRESSEDE
Elements)
ONCRETE TRUCTURAL LEMENTS
Assembly Concepts for
Precast Concrete
Buildings
• Above: Precast
concrete structure
consisting of solid
wall panels and
hollow core slabs.
• Below: A single story
warehouse consisting
of double tees
supported by
insulated sandwich
wall panels.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Precast Elements (Assembling Elements)
Assembly Concepts
for Precast
Concrete
Buildings
• A parking garage
structure
consisting of
precast double
tees supported
by inverted tee
beams on
haunched
columns.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Jointing Elements (Column to Colums)
Example Column-to-Column Connection
• Metal bearing plates and embedded anchor bolts are cast into
the ends of the columns.
• After the columns are mechanically joined, the connection is
grouted to provide full bearing between elements and protect
the metal components from fire and corrosion.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Jointing Elements (Column to Beam)
Example Beam-
to-Column
Connection
• Beams are set
on bearing
pads on the
column
corbels.
• Steel angles
are welded to
metal plates
cast into the
beams and
columns and
the joint is
grouted solid.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Jointing Elements (Beam to Slab)
Example Slab-to-
Beam
Connection
• Hollow core
slabs are set on
bearing pads on
precast beams.
• Steel
reinforcing bars
are in inserted
into the slab
keyways to
span the joint.
• The joint is
grouted solid.
• The slab may
remain
untopped as
shown, or
topped with
several inches
of cast in place
concrete.
Jointing Elements (Overtopping Slab)
Sitecast Concrete
Toppings over
Precast Slabs
• Greater floor
strength and
stiffness
• Greater fire
resistance
• Greater acoustic
isolation
• Allow easy
integration of
electrical services
into floor system
• Create a smoother,
flatter floor surface.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
Perencanaan Plat Lantai
(Cast in situ Vs Precast)
Pendahuluan
• Beton Bertulang Vs Beton Prategang
Beton Bertulang
Beton kuat thd tekan lemah thp tarik
Baja kuat thd tarik (juga thd tekan)
Beton bertulang (beton mampu menahan tekan, baja tulangan mampu
menahan tarik.
Kuat tarik beton diabaikan
Balok beton bertulang selalu retak pada kondisi layan
Beton Prategang
Prategang adalah metode penerapan gaya tekan pada bagian beton
Efek dari prategang yaitu mereduksi tegangan tarik yang bekerja pd beton
Beton dapat divisualisasikan dg sistem 2 gaya yang bekerja yaitu
1. Gaya internal prategang
2. Gaya eksternal (beban,LL,DL,dll)
• Perspektif Sejarah Beton Prategang
• Perspektif Sejarah Beton Prategang
Eugene Freyssinet (1879-1962)
Penemu yang mengajukan baja mutu tinggi yang tidak
dapat mengalami elongation,creep,LOP akibat creep &
shrinkage
Jembataan Prategang Pertama yang dibuat di Perancis
(tahun 1941)
• Aplikasi Beton Prategang
Jembatan
Slab/plat beton
Tiang Pancang
Plat cangkang
Offshore platform
Nuclear power plant
Perbaikan dan rehabilitasi struktur
• Tipe dan Klasifikasi Beton Prategang
1. Pretensioned Vs Posttensioned
2. External Vs Internal
3. Linier Vs Circular
4. End anchored Vs Non end anchored
5. Bonded Vs Unbonded
6. RC Vs PC Vs PPC
7. Partial Vs Full prestressing
1. Pre-tensioned Vs Post-tensioned
Pretensioned
Posttensioned
2. Eksternal Vs Internal
3. Linier Vs Circular
4. End Anchored Vs Non End Anchored
5. Bonded Vs Unbonded
Bonded Unbonded
6. RC Vs PC Vs PPC
7. Full prestress and Partially prestress
• Material dan Peralatan Beton Prategang
a. Beton
b. Baja Prategang
c. Peralatan beton prategang
a.Beton
Sifat mekanik beton
1. Kuat tekan
2. Modulus Elastisitas
3. Modulus Runtuh
• Kuat tekan beton
• Modulus elastisitas beton
• Modulus runtuh beton
Formula Sifat Mekanik Beton Dengan Parameter Kuat Tekan Beton
b. Baja Prategang
Tendon Prategang
Bentuk : dapat berupa baja terpilin, batang, kawat dll
Material : baja mutu tinggi, fiber komposit, glass fiber komposit
Kurva Teg vs Reg Baja Bentuk tendon prategang
c. Peralatan Baja Prategang
Pretensioned equipments
Hold down devices
c. Peralatan Baja Prategang
Post tensioned equipments
1. Stressing anchorage
2. Dead-end anchorage
3. Duct/Grout tube
2. Analisis & Perencanaan
Lentur
1. Distribusi regangan disepanjang permukaan kolom bersifat linier
2. Tidak terjadi slip antara beton dan tulangan
3. Regangan tekan maksimum pada kondisi ultimit = 0,003
4. kekuatan tarik tekan beton diabaikan, karena jauh lebih kecil
dari kekuatan tarik baja tulangan, sehingga tidak berarti
Pengaruh Prategang
P Pe M
A W W
Solusi:
1
M q l2
8
1
M 18KN / m 10 2
8
M 225 KNm 225 10 6 Nmm
1000 10 3 1000 10 3 250 225.10 6
a ( ) ( ) ( )
500 750 1 1
500 750 2
500 750 2
6 6
a 2,667 5,333 4,8
a 2,134 N / mm 2
1000 10 3 1000 10 3 250 225.10 6
b ( ) ( )( )
500 750 1 1
500 750 2
500 750 2
6 6
b 2,667 5,333 4,8
b 3,200 N / mm 2
Latihan 1
Latihan 2
Gaya-gaya pada Tendon
e
e (0,5 h) d' arc tg 1
1 L M qu L2 P cos 800 cos 2,57 o
2 8
e (0,5 700) 125
225 1 P cos 799,19 KN
e 225 mm arc tg M 10 10 2
1 10000 8 P sin 800 sin 2,57 o
2 M 125 KNM
2,57 o P sin 35,87 KN
799,19 103 179,35 106 125.106
a ( ) ( ) ( )
Mp P sin 1 L 400 700 1
400 700 2 1
400 700 2
2
6 6
Mp 35,87 KN 5 m
a 2,85 5,49 (3,82)
Mp 179,35 KNm
a 1,18 N / mm2
799,19 103 179,35 106 125.106
b ( ) ( )( )
400 700 1 1
400 700 2
400 700 2
6 6
b 2,85 (5,49) 3,82
b 4,52 N / mm2
Latihan 1
Solusi :
Hitung A, ya, yb, Wa, Wb, Itot,
e, kemudian hitung tegangan
penampang spt biasa!
Metode Load Balancing
“Contoh Kasus” Metode Load Balancing
e (0,5 h) d'
e (0,5 500) 125
e 125 mm
qbs 0,3m 0,5m 24KN / m3
3,6 KN / m P M
a
1 A W
M 3,6 82 300 10 3 8,7 10 6
8
28,8KNm 300 500 1
300 500 2
6
M 37,5KNm 28,8KNm
2 0,696
8,7KNm
1,304 N / mm 2
P e
Wp
L
300 KN 0,125 m P M
b
8m A W
4,7875 KN 300 10 3 8,7 10 6
300 500 1
1 300 500 2
Mp Wp L2 6
8
2 0,696
1
4,6875KN 52 m2 2,696 N / mm 2
8
37,5KNm
“Latihan” Metode Load Balancing
A =477400 mm2
yt =889 mm
yb =711 mm
e =711-125 = 586 mm
I =146000000000 mm4
Wt =164335000 mm3
Wb =205502000 mm3
Hitung gaya prategang dan gambarkan tegangan balok
prategang diatas?
Desain Awal Lentur
Transfer (tekan) σct = 0,6 f’c ; (tarik) σtt =0,25 f’c
Servis (tekan) σcs = 0,45 f’c ; (tarik) σts =0,50 f’c
