8

1.1. Perhitungan Secara Sistematis

Panjang Batang Bawah B1 = B2 = B3 = B4 = B5 = B6 = B7 = B8B = Panjang Batang Tegak

T1 = T7T1 = tan . B1= tan 450 . 2,5 = 2,5

T2 = tan . (B1 + B2) = tan 450 . (2,5 + 2,5) = 5

T3 = tan . (B1 + B2 + B3) = tan 450 . (2,5 + 2,5 + 2,5) = 7,5 m

T4 = tan . (B1 + B2 + B3 + B4) = tan 450 . (2,5 + 2,5 + 2,5 + 2,5) = 10 m

Panjang Batas AtasA1 = A2 = A3 = A4 = A5 = A6 = A7 = A8

D1 = = 3,535 D2 = = 5,590

D3 = =7,905

NoA (m)B (m)T (m)D (m)

13,535 2,52,53,535

23,5352,555,590

33,5352,57,57,905

43,5352,5107,905

53,5352,57,55,590

63,5352,553,535

73,5352,52,5-

83,5352,5--

BAB 2Perhitungan Gording

2.1 Data Bentang rangka atap: 20 m Jarak kuda-kuda: 6 m Berat atap asbes: 18 kg/m Jarak gording: 1,7 m Beban angin: 30 kg/m2 Beban berguna: 75 kg

2.2 Perencanaan Dimensi GordingDi coba gording siku sama kaki 120:120:11Data profil : F= 25,4 cm2G= 19,9 kg/mLx= 341 cm4Ly= 341 cm4Wx= 39,5 cm3Wy= 39,5 cm3

2.3 Pembebanan GordingA. beban mati Berat sendiri gording = 1 x 19,9 = 19,9 kg/mBerat penutup atap = 1,7 x 18 x 1 = 30,6q1 = 19,9 + 30,6 = 50,5 kg/mbrancing 10% x q1 = 5,050 kg/mq2 = 5,050 kg/m

qtotal = q1 + q2= 50,5 + 5,050= 55,5 kg/m

B. beban berguna = 70 kgC. Beban Angin Angin tekan C = 0,02 . 0,4 = 0,02 . 45 0,4 = 0,5 Angin Isap = C` = - 0,4 Beban Angin Tekan W = C x W x a x 1=0,5 x 30 x 1,7 x 1= 25,5 kg/m Beban Angin IsapW` = C` x W x a x 1 = - 0,4 x 30 x 1,7 x 1 = - 20,4 kg/m

2.4 Momen Pada GordingA. Akibat beban matiqy = q.cos = 55,5.cos 450= 39,280 kg/m

qx = q.sin = 55,5.sin 450= 39,280 kg/m

Mqy = 1/8.qy.2= 1/8.39,280.62= 176,759 kg/m

Mqx = 1/8.qx.2= 1/8.39,280.62= 176,759 kg/m

B. Akibat Beban Berguna Py = p. cos = 70.cos 450= 53,033 kg/mPx = p.sin = 70.sin 450= 53,033 kg/mMpy= 1/4.qy.= .53,033. 6= 79,550 kg/mMpx = 1/4.qx.= .53,033. 6= 79,550 kg/m

C. Akibat Beban AnginWy = w = 25,5Wx = 0Mwy = 1/8.wy. 2=1/8.25,5.62= 114,75 kg/m Mwx = 0

D. Angin IsapWy` = w` = - 20,4Wx` = 0Mwy`= 1/8.wy`. 2=1/8.-20,4.62= - 91,8 kg/mMwx` = 0

2.5 Kombinasi MomenArahBeban MatiBeban HidupBeban AnginKombinasi

12345678

x176,75979.55000256.309256.309256.309

y176,75979.550114.750-91.8256.309371.059164.509

2.6 Kontrol Terhadap Tegangan

Mx = 256.309 kg.m = 25630.9 kg.cmMy = 371.059 kg.m =37105.9 kg.cmWx = 39,5 cm3Wy = 39,5 cm3 = 1600 kg/ cm2

Aman

2.7 Kontrol Terhadap LendutanData : qx= 39,280 kg/m = 0,393 kg/cm2qy= 39,280 kg/m = 0,393 kg/cm2px= 53,033py= 53,033lx= 341ly= 341= 6 m = 600 cmE= 2x106 kg/cm2

Lendutan arah sumbu x Dx = 5/384 x ((0,393x6004)/ (2x106 x 341)) + 1/48 x ((53,033 x6003)/ (2x106 x 341))Dx = 1,2589

Lendutan arah sumbu x Dy = 1,2589

= = 1,780 Aman

ijin= 1/250 x 600 = 2400

Maka, profil siku sama kaki dimensi 120:120:11 aman terhadap tegangan dan lendutan.