Analisa Balok Anak As 7 Analisa Pembebanan Balok Anak As 9
d. Beban Hidup ql = 1 x 2 x 250 kgm
= 500 kgm = 0,3355 kipft
b. Beban berfaktor qu qu
= 1,2 qd + 1,6 ql = 1,2 . 0,4609 + 1,6 . 0,3355
= 1,089 kipft L = 6 m = 19,68 ft
Analisa awal menggunakan tumpuan sendi-roll M max
= 8
1 . qu . L
2
+ 18 q L =
8 1
. 1,089. 19,68
2
+ 18 0,6196 . 19,68 = 52,72 kip-fit
Z
x
= fy
M
max =
36 .
9 ,
72 ,
52 = 1,627 ft
3
= 19,75 in
3
Dengan Z
x
= 19,75 in
3
, dari LRFD di dapat Profil W8 x 24 Dengan data
– data sebagai berikut : A = 7,08 in
2
wt = 24 lbft
ry = 1,61 in
d = 7,93 in Ix
= 82,8 in
4
x
1
= 3020 ksi tw = 0,245 in
Zx = 23,2 in
3
x
2
= 1610
1 . 10
5
ksi
19,68 ft
bf = 6,495 in Sx
= 20,9 in
3
kr =
16 9
in tf = 0,4 in
rx = 3,42 in
Sy = 5,63 in3
T = 6 8
1 in Iy
= 18,3 in
4
k =
8 7 in
Zy = 8,57 in
3
Dengan Tumpuan Jepit – jepit
qu = qu
1
+ Berat Sendiri = 1,089 + 0,024
= 1,113 kipft M max =
12 1
. qu . L
2
= 12
1 . 1,113. 19, 68
2
= 35,92 kipft
Ra = Rb =
2 1 . qu . L
= 2
1 . 1,113. 19,68 = 10,95 kip
M
1
= M
2
= 24
1 . qu . L
2
= 24
1 .1,113 . 19,68
2
= 17.96 kip-ft
Mu = Mmax + 10 .
2 2
1 M M
= 35,92 + 0,1. 2
92 ,
35 92
, 35
= 37,716 kip-ft 17.96 + 17.96
Mu M
1
37,716 17,716 Dipakai M
u
= 37,716 kip-ft Check: ØMn M
u
12 .
. 9
, fy
Zx 37,716 kip-ft
12 36
. 2
, 23
. 9
, 37,716kip-ft
62,64 37,716kip-
ft ……..Ok Didapatkan :
Lb = 19,68 ft Lp = 6,7 ft
Dari LRFD Tabel 4-20 Lr = 24,4 ft Dari LRFD Tabel 4-20
Jadi LpLbLr M
U
= 37,716 kip.ft Syarat
M
n
M
U
Profil W8 x 24 Mp = F
Y
.
X
= 36 . 23,2 = 835,2 kip.in = 69,488 kip.ft Mr = fy
– Fr . Sx = 36 – 10 . 20,9 = 543,4 kip in = 45,210 kip ft
M
n
= C
b
L M
- M
- M
[
b r
P P
P r
P
L L
L
= 1 .
7 ,
6 4
, 24
7 ,
6 68
, 19
21 ,
45 488
, 69
488 ,
69
= 44,48 kip.ft
dipakai Mn = Mp M
n
= 0,9 x 44,48 kip.ft M
n
= 40,032 kip.ft Mn
Mu
1
40,032 21,552
= 0,53 1 .......ok