Sebelum Komposit Beban Mati

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5.3.4.1 Analisa Penampang Balok

1. Sebelum Komposit

Gambar 5.21 Gambar Potongan Melintang Balok Girder 30,8 m Tabel 5.7. Analisa Penampang Balok Prategang No A cm 2 Y cm A.Ycm 3 I cm 4 A . Y-Ybp 2 Ix cm 4 1 687,5 153,75 105703,125 8951,822 4691783,319 4700735,141 2 138,75 145 20118,75 433,59375 756922,82 757356,414 3 2250 85 191250 2929687,50 432224,1 3361911,6 4 235 25,833 6070,755 1305,55 482390,198 483695,748 5 1462,5 11,25 16453,125 61699,22 5245712,69 5307411,91 4773,75 339595,755 14611110,81 • Penentuan cgc balok prategang Ybp = Σ A. Y Σ A = 339595,755 4773,75 = 71,14 cm Ytp = 160 – 71,14 = 88,86 cm • Penentuan batas inti balok prategang Ktp = Ix A . Ybp = 14611110,81 4773,75 x 71,14 = 43,024 cm Kbp = Ix A x Ytp = 14611110,81 4773,75 x 88,86 = 34,44 cm 550 1600 Ybp Ytp Ybc Ytc cgc composit cgc prestress 125 75 1075 100 225 180 ℵ ℑ ℑ ℘ ℘ ⊗ b eff = 1850 650 154 W a = t X Y I = 86 , 88 1 14611110,8 = 164428,4359 cm 3 W b = b X Y I = 14 , 71 1 14611110,8 = 205385,308 cm 3

2. Sesudah Komposit

Gambar 5.22 Komposit Balok Prategang Direncanakan : • Mutu beton gelagar prategang : f’c = 50 Mpa • Mutu beton pelat lantai : f’c = 22,5 Mpa • Modulus elastisitas beton E = 4730 √f’c E plat = 4730 √22,5 E balok = 4730 √50 • Angka ekivalen n = E balok E plat = 4730 √50 4730 √22,5 = 1.49 • Luas plat lantai = 185 x 20 = 3700 cm 2 • Luas plat lantai ekivalen dengan luas beton precast A eki = A plat n = 3700 1,49 = 2483,22 cm 2 • b eff = A eki t plat = 2483,22 20 = 124,161 cm = 1241,61 mm • b eff maximum = 1850 mm jarak bersih antar balok Balok Pratekan Plat Lantai 20 cm 160 cm Bef f Bma x 155 Tabel 5.8. Analisa Penampang Komposit No A cm 2 Y cm A.Ycm 3 I cm 4 A . Y-Ybp 2 Ix cm 4 P 4773,75 71,14 339604,575 14611110,81 5462762,447 20073873,26 VI 2483,22 170 422147,4 82774 10501937,24 10584711,24 7256,97 761751,975 30658584,5 • Penentuan cgc balok komposit Ybc = Σ A. Y Σ A = 761751,975 7256,97 = 104,968 cm ≈ 104,97 cm Ytc = 180 – 104,968 = 75,032 cm ≈ 75,03 • Penentuan batas inti balok komposit Ktc = Ix A . Ybc = 30658584,5 7256,97 x 104,968 = 40,2475 cm Kbc = Ix A x Ytc = 30658584,5 7256,97 x 75,032 = 56,3054 cm

5.3.4.2 Pembebanan Balok Prategang :

1. Beban Mati

a. Berat sendiri balok prategang q 1 : q 1 = Ac x beton pratekan U = 0,477375 m 2 x 2,5 tm 3 = 1,1934 tm = 11,934 kNm V B = 0 V B = R A . 30,8 – ½ . 11,934 . 30,8 2 = 30,8R A – 5660,5349 R A = 183,784 kN M = R A . x – ½ . 11,934 . x 2 M X = 183,784 . x – 5,967 . x 2 Dx = 183,784 . – 11,934 . x 2 11,934 kNm 30,8 m A B 156 Jarak Mx Dx 3,85 619,12 137,84 4,00 639,66 136,05 7,70 1061,35 91,89 8,00 1088,38 88,31 11,50 1324,38 46,54 12,00 1346,16 40,58 15,40 1415,14 0,00 . b. M MATI TOTAL Qtotal = Berat sendiri + berat plat + diafragma + berat perkerasan - Berat sendiri balok prategang q 1 : q 1 = Ac x beton pratekan U = 0,477375 m 2 x 2,5 tm 3 = 1,1934 tm = 11,934 kNm - Berat plat lantai q2 q 2 = A plat x beton bertulang = 0,2m x 1,85m x 2,5 tm 3 = 0,925 tm - Berat Pavement q3 : q 3 = A x beton aspal = 0,05m x 1,85m x 2,0 tm 3 = 0,185 tm - Berat diafragma P : P = V diafragma x beton bertulang = 0,20 m x 1,67 m x 1,075 m x 2,5 tm 3 = 0,8976 t Total beban q = q 1 + q 2 + q 3 = 1,1934 tm +0,925 tm + 0,185 tm = 2,3034 tm = 23,034 kNm Total beban P = 0,8976 t 6,00 m 30.80 m 0,4 m 6,00 m 6,00 m 6,00 m 6,00 m B P 1 P 2 P 3 P 4 P 5 P 6 0,4 m Q =2,3034 tm A 157 Direncanakan dipasang 6 buah difragma dengan jarak antar diafragma 6,00m P = 6 x 0,8976 = 5,386 Ton V B = 0 V B = R A . 30,8 - P 1 . 30,4 – P 2 . 24,4 – P 3 . 18,4 – P 4 . 12,4 – P 5 .6,4 – P 6 . 0,4 - ½ . q . 30,8 2 V B = R A . 30,8 - 0,8976 . 30,4 – 0,8976 . 24,4 – 0,8976 . 18,4 – 0,8976 . 12,4 – 0,8976 .6,4 – 0,8976 . 0,4 - ½ . q . 30,8 2 V B = R A . 30,8 – 22,34 – 17,93 – 13,52 – 9,11 – 4,70 – 0,29 – 1092,549 R A = 38,17 Ton M 3,85 = R A . 3,85 – P 1 . 3,85 – 0,4 – ½ . q . 3,85 2 = 38,17 . 3.85 – 0,8976 . 3,45 – 0,5 . 2,3034 . 3,85 2 = 126,787 Tonm = = 1267,87 kNm D 3,85 = R A – P 1 – q . 3,85 = 38,17 – 0,8976 – 2,3034 . 3,85 = 28,404 Ton = 284,04 kN Jarak Mx Dx 381,7 3,85 1267,87 284,04 4,00 1310,21 280,59 7,70 2179,05 186,39 8,00 2233,93 179,48 11,50 2721,02 98,86 12,00 2767,56 87,34 15,40 2904,46 0,00

2. Beban Hidup