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Perencanaan Struktur dan Rencana Anggaran Biaya Gedung Kuliah 2 lantai
BAB 6 Balok Anak
C
3 4
3 2
2
300 300
300 300
P
1 = 6484,89 kg
P
1 = 6484,89 kg
2 2
3 4
2 2
2 2
3 2
2
2 2
300 300
300 300
C
P
1
P
1
6.3. Perhitungan Balok Anak As C2 – 4 = As N2 – 4
6.3.1 Pembebanan
Gambar 6.3 lebar equivalen pembebanan balok anak As C2-4
a. Dimensi Balok
h = 110 . L b = 12 . h
= 110 . 600 = 12 x 45
= 60 cm dipakai 45 cm = 20 – 25 cm dipakai 25 cm
b. Pembebanan Setiap Elemen
¾ Beban Mati qD
Berat sendiri balok = 0,25 x0,45 – 0,12 x 2400= 198 kgm’ Berat plat
= 2 x 1 x 404 = 808 kgm’
qd = 1006 kgm
’
Beban titik P1 = 6484,89 kg ¾
Beban Hidup qL Beban hidup digunakan 250 kgm
2
qL = 250 x 2 x 1 = 500 kgm’
Pembebanan Balok Anak
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Perencanaan Struktur dan Rencana Anggaran Biaya Gedung Kuliah 2 lantai
BAB 6 Balok Anak
45
250
d
d
Bidang Momen
Bidang Geser
6.3.2 Perhitungan Tulangan a Tulangan Lentur Balok Anak
Data Perencanaan: b = 250 mm
Ø
t
= 19
mm h = 450 mm
Ø
s
= 10
mm f’c = 25 Mpa
d’ = 40 + 8 + ½ .19 fy = 360 Mpa ulir
= 57,5 mm fys = 240 Mpa polos
d = h – d’
p = 40 mm = 450 – 57,5 = 392,5 mm
m =
9412 ,
16 25
. 85
, 360
. 85
, =
= fc
fy
ρb =
⎟⎟⎠ ⎞
⎜⎜⎝ ⎛
+ fy fy
fc 600
600 .
. .
85 ,
β
= ⎟
⎠ ⎞
⎜ ⎝
⎛ + 360
600 600
. 85
, .
360 25
. 85
, =
0,03136 ρ
max
= 0,75 . ρb
= 0,0235
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Perencanaan Struktur dan Rencana Anggaran Biaya Gedung Kuliah 2 lantai
BAB 6 Balok Anak
ρ
min
= 0039
, 360
4 ,
1 4
, 1
= =
fy ¾
Daerah Lapangan
Mu = 11847,57 kgm = 11,848.10
7
Nmm Perhitungan SAP Mn
= φ
Mu =
8 ,
10 .
848 ,
11
7
= 14,81.10
7
Nmm Rn =
2 7
2
392,5 .
50 2
10 14,81.
d .
b Mn =
= 3,845 m =
25 .
85 ,
360 .
85 ,
= c
f fy
= 16,94
ρ = ⎟⎟⎠
⎞ ⎜⎜⎝
⎛ −
− fy
2.m.Rn 1
1 m
1
= ⎟⎟⎠
⎞ ⎜⎜⎝
⎛ −
− 360
3,845 .
16,94 .
2 1
1 16,94
1 =
0,0118 ρ
ρ
min
ρ ρ
max
→ dipakai tulangan tunggal Digunakan
ρ = 0,0118
As perlu = ρ. b . d
= 0,0118. 250. 392,5 = 1164,256 mm
2
n =
2
19 .
π .
4 1
perlu As
= 385
, 283
256 ,
1164 = 4,108 ~ 5 tulangan
Dipakai tulangan 5 D 19 mm
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Perencanaan Struktur dan Rencana Anggaran Biaya Gedung Kuliah 2 lantai
BAB 6 Balok Anak
450
250
d2 d1
s
d
As ada = 5. ¼ . π . 19
2
= 5 . ¼ . 3,14 . 19
2
= 1416,925 mm
2
As perlu 1164,256 → Aman..
a = =
b .
c f
. 0,85
fy .
ada As
250 .
25 .
0,85 360
. 1416,925
= 96,02 Mn ada = As ada . fy d – a2
= 1416,925. 360 392,5 – 96,022 = 17,572.10
7
Nmm Mn ada Mn
→ Aman..
Jadi dipakai tulangan 5 D 19 mm
Cek jarak =
1 -
n t
- s
2 -
p 2
- b
φ φ
1 -
5 5.19
- 2.8
- 2.40
- 250
= = 14,75 mm 25 mm dipakai tulangan dua lapis
Di pakai d d1 =
392,5 mm
d2 = d1 – s – 2 x ½ Ø
= 392,5 – 30 – 2 x ½.19 =
343,5 mm
d x 7 = d1 x 4 + d2 x 3
d 5
2 x
343,5 3
x 392,5
+ =
= 373
mm Mn ada = As ada . fy d – a2
= 1416,925. 360 373 – 96,022 =
14,129.10
7
Nmm Mn ada Mn
→ Aman..
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Perencanaan Struktur dan Rencana Anggaran Biaya Gedung Kuliah 2 lantai
BAB 6 Balok Anak
¾
Daerah Tumpuan
Mu = 17715,25 kgm = 17,716.10
7
Nmm Perhitungan SAP Mn
= φ
Mu =
8 ,
10 .
716 ,
17
7
= 22,145.10
7
Nmm Rn =
2 7
2
392,5 .
250 10
22,145. d
. b
Mn = = 5,75
m = 25
. 85
, 360
. 85
, =
c f
fy = 16,94
ρ = ⎟⎟⎠
⎞ ⎜⎜⎝
⎛ −
− fy
2.m.Rn 1
1 m
1
= ⎟⎟⎠
⎞ ⎜⎜⎝
⎛ −
− 360
5,75 .
16,94 .
2 1
1 16,94
1 =
0,0191 ρ
ρ
min
ρ ρ
max
→ dipakai tulangan tunggal Digunakan
ρ
ada
= 0,0191 As perlu =
ρ
ada
. b . d = 0,0191 . 250. 392,5
= 1870,919 mm
2
n =
2
19 .
π .
4 1
perlu As
= 385
, 283
919 ,
1870 = 6,602 ~ 7 tulangan
Dipakai tulangan 7 D 19 mm As ada = 7 . ¼ .
π . 19
2
= 7 . ¼ . 3,14 . 19
2
= 1983,695 mm
2
As perlu 1870,919 → Aman..
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Perencanaan Struktur dan Rencana Anggaran Biaya Gedung Kuliah 2 lantai
BAB 6 Balok Anak
450
250
d2 d1
s
d
a = =
b .
c f
. 0,85
fy .
ada As
250 .
25 .
0,85 360
. 1983,695
= 134,42 Mn ada = As ada . fy d – a2
= 1983,695. 360 392,5 – 134,422 = 23,230.10
7
Nmm Mn ada Mn
→ Aman..
Jadi dipakai tulangan 7 D 19 mm
Cek jarak =
1 -
n t
- s
2 -
p 2
- b
φ φ
1 -
7 7.19
- 2.10
- 2.40
- 250
= = 2,4 mm 25 mm dipakai tulangan dua lapis
Di pakai d d1 =
392,5 mm
d2 = d1 – s – 2 x ½ Ø
= 392,5 – 30 – 2 x ½.19 =
343,5 mm
d x 7 = d1 x 4 + d2 x 3
d 7
3 x
343,5 4
x 392,5
+ =
= 371,5
mm Mn ada = As ada . fy d – a2
= 1983,695. 360 371,5 – 134,422 =
21,730.10
7
Nmm Mn ada Mn
→ Aman..
b Tulangan Geser Balok anak
¾
Daerah Lapangan
Vu = 9854,28 kg = 98542,8 N Perhitungan SAP
f’c = 25 Mpa
fy = 240 Mpa
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Perencanaan Struktur dan Rencana Anggaran Biaya Gedung Kuliah 2 lantai
BAB 6 Balok Anak
d = h – p – ½ Ø
= 450 – 40 – ½ 8 = 406 mm Vc
= 1 6 . c
f .b . d = 1 6 . 25 . 250. 406
= 84583,33 N Ø Vc
= 0,6 . 84583,33 N = 50750 N
3 Ø Vc = 3 . 50750 = 152250 N
Ø Vc Vu 3 Ø Vc 50750 N 98542,8 N 152250 N
Jadi diperlukan tulangan geser Ø Vs
= Vu - Ø Vc = 98542,8 – 50750 = 47792,8 N
Vs perlu = 6
, Vs
φ =
6 ,
8 ,
47792 = 79654,667 N
Digunakan sengkang ∅ 8
Av = 2 . ¼
π 8
2
= 2 . ¼ . 3,14 . 64 = 100,48 mm
2
s = =
= 667
, 79654
406 .
240 .
48 ,
100 perlu
Vs d
. fy
. Av
122,9 mm ~ 120 mm s
max
= d2 = 2
406 = 203 mm ~ 200 mm
Jadi dipakai sengkang dengan tulangan Ø 8 – 120 mm
¾
Daerah Tumpuan
Vu = 12865,08 kg = 128650,8 N Perhitungan SAP
f’c = 25 Mpa
fy = 240 Mpa
d = h – p – ½ Ø
= 450 – 40 – ½ 8 = 406 mm
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Perencanaan Struktur dan Rencana Anggaran Biaya Gedung Kuliah 2 lantai
BAB 6 Balok Anak
45
250 45
250
2 D 19
2 D 19 7 D 19
2 D 19
8 - 75 O
8 - 120 O
POT. TUMPUAN POT. LAPANGAN
Vc = 1 6 .
c f .b . d
= 1 6 . 25 . 250. 406 = 84583,33 N
Ø Vc = 0,6 . 84583,33 N
= 50750 N 3 Ø Vc = 3 . 50750
= 152250 N Ø Vc Vu 3 Ø Vc
50750 N 128650,8 N 152250 N Jadi diperlukan tulangan geser
Ø Vs = Vu - Ø Vc
= 128650,8 – 50750 = 77900,8 N Vs perlu =
6 ,
Vs φ
= 6
, 8
, 77900
= 129834,67 N Digunakan sengkang
∅ 8 Av
= 2 . ¼ π 8
2
= 2 . ¼ . 3,14 . 64 = 100,48 mm
2
s = =
= 67
, 129834
406 .
240 .
48 ,
100 perlu
Vs d
. fy
. Av
75,409 mm ~ 75 mm s
max
= d2 = 2
406 = 203 mm ~ 200 mm
Jadi dipakai sengkang dengan tulangan Ø 8 – 75 mm
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Perencanaan Struktur dan Rencana Anggaran Biaya Gedung Kuliah 2 lantai
BAB 6 Balok Anak
8
L M
8
5
400
L M
400
qD = 2262,6 kgm qL = 665 kgm
6.4. Perhitungan Balok Anak As 5 L – M
