33
=
2 2
6 .
10 .
6 1
5 .
3856 10
. 6
. 6
1 9
. 2507
+
= 89.354 kgcm = 89.354 kgcm
2
≤ 100 kgcm
2
= σ
ltr
OK
Jadi, usuk kayu dengan dimensi 57 cm aman dipakai Gambar 1. Rangka Kuda - Kuda
4. Mencari Panjang Batang
Tabel 3. Gaya-gaya pada Kuda-kuda
No Batang Panjang Batang cm
No Batang Panjang Batang cm
a1 = a12 140
d1 = d10 180
a2 = a11 140
d2 = d9 210
a3 = a10 140
d3 = d8 254
a4 = a9 150
d4 = d7 249
a5 = a8 104
d5 = d6 277
a6 = a7 104
d11 = d12 306
b1= b12 156
v1 = v11 62
b2 = b11 156
v2 = v10 98
b3 = b10 156
v3 = v9 134
b4 =
b9 167 v4 =
v8 170 b5
= b8 200 v5
= v7 196
34
b6 = b7 200
v6 231
b13 = b16 119
v12 = v14 98
b14 = b15 115
v13 231
5. Perencanaan Gording
Jarak gording = 1.5 m
Jarak kuda-kuda = 3.6 m
a. Pembebanan Beban mati
- berat sendiri gording taksiran = 3.6 x 1.5
= 5.4 kgm - berat sendiri genteng
= 50 x 1.5 = 75
kgm - berat penggantung + plafond
= 18 x 1.5 = 27
kgm =
107.4 kgm
- berat lain-lain 10 = 10 x 107.4
= 10.74 kgm
q =
118.14 kgm
Momen akibat beban mati q x
= q x cos 30 = 118.14 x 0.866
= 102.312 kgm qy
= q x sin 30 = 118.14 x 0.5
= 59.07 kgm Mx
= 18 x 102.312 x 3.6
2
= 165.745 kgm
35
My = 18 x 59.07 x 3.6
2
Beban Hidup P = 100 kg Py
= P x sin 30 = 100 x 0.5
= 50 kg Px
= P x cos 30 = 100 x 0.866
= 86.6 kg My
= ¼ x Py x l = ¼ x 50 x 3.6
= 45 kgm Mx
= ¼ x Px x l = ¼ x 86.6 x 3.6
= 77.94 kgm Beban angin
Koefisien angin tekan = 0.02 x 30 -0.4 = 0.2 w = 0.2 x 1.5 x 25
= 7.5 kgm M = 18 x 7.5 x 3.6
2
= 12.15 kgm Koefisien angin hisap = -0.4
w = -0.4 x 1.5 x 25 = -15 kgm
M = 18 x -15 x 3.6
2
= -24.3 kgm Momen kombinasi
a. Beban mati + beban hidup
36
Mx = 165.745 + 77.94 = 243.69 kgm My = 95.693 + 45 = 140.69 kgm
b. Beban mati + beban hidup + beban angin Mx = 165.745 + 77.94 + 12.15 = 255.84 kgm
My = 95.693 + 45 = 140.69 kgm b. Pendimensian Gording
Direncanakan memakai profil C tipis, atap yang didunakan adalah atap genteng jadi merupakan struktur yang tegar sehingga diambil momen arah
x yang terbesar Mx = 255.84 kgm
3 2
99 .
15 1600
25584 cm
cm kg
kgcm Mx
Wx =
= =
σ Dicoba profil C 150x50x20x4.5 dari tabel Profil Baja didapatkan :
W
x
= 49.0 cm
3
W
y
= 10.5 cm
3
Ix = 368 cm
4
Iy = 35.7 cm
4
Weight = 9.20 kgm Kontrol tegangan
σ
ytsb
= M
x
W
x
= 2558449.0 cm
3
= 522.12 kgcm
2
σ = 1600 kgcm
2
Kontrol lendutan f ijin = l 250 x 1 = 360 250
= 1.44 cm
37
fx = xExlx
Pxxl xExlx
xqxxl 48
384 5
3 4
+
= 368
10 1
. 2
48 360
6 .
86 368
10 1
. 2
384 360
02312 .
1 5
6 3
6 4
x x
x x
x x
x x
x +
= 0.29 + 0.11 = 0.4 cm fy =
xExIy l
Pyx xExIy
l xqyx
48 2
384 2
5
3 4
+
= 7
. 35
10 1
. 2
48 2
360 50
7 .
35 10
1 .
2 384
2 360
5907 .
5
6 3
6 4
x x
x x
x x
x x
x +
= 0.11 + 0.08 = 0.19 cm f =
2 2
fy fx
+ =
+
2
4 .
2
19 .
= 0.44 cm 1.44 cm……………oke
6. Menghitung Pembebanan Kuda-kuda
