ac

d

d'

d-a/2d-d'

Tsy

cu'

=

0,85.f'c

As

As'

Cs

Cc

Analisis Kapasitas Balok dengan Tulangan Rangkap

Data-data perencanaan balok sebagai berikut :

Mutu beton, fc = 25 MPa

Mutu baja :

Tulangan Longitudinal fyv = 400 MPa

Tulangan Geser fys = 240 Mpa

Tebal penutup beton = 40 mm

Diameter tulangan utama = 22 mm

Diameter sengkang = 10 mm

Dimensi balok: bw = 300 mm; h = 600 mm

.2

1'

tulsengkang Dpd = 40 + 10 + .22 = 61 mm

Tinggi efektif 'dhd = 600-61 = 539 mm

Tentukan momen nominal negative dan momen nominal positip penampang yang

merupakan bagian dari tumpuan system balok kolom. Adapun posisi tulangan

terpasang seperti di bawah ini :

Momen Nominal Tumpuan

Perhitungan momen nominal negatif tumpuan:

Diagram tegangan regangan balok induk tumpuan

As = 5D22 (1900,664 mm2)

As = 3D22 (1140,398 mm2)

Asumsi tulangan tarik leleh dan tulangan tekan belum leleh.

068,41738571.54,76026.75,5418

0400664,190060061398,114085,02585,0

0..'..''....'.85,0

.............'..'

'....'.85,0

.''...'.85,0

0

2

2

2

1

1

cc

ccc

cfAEdcAcbf

cfAEc

dcAbcf

fAfAbaf

TCCH

ysscusc

ysscusc

ysssc

ssc

nilai c diselesaikan dengan menggunakan rumus:

a

acbbc

2

42

2,1

mm 80,801amm 06,95

75,54182

68,4173857175,5418454,7602654,76026 2

2,1

c

c

d = 600-40-10-265,760398,1140

58265,76011398,1140

= 520,2 mm

Kontrol keserasian regangan:

002,0

200000

400001075,0

06,95

6106,95003,0

''

s

y

ycusE

f

c

dc

Baja tulangan tekan belum leleh (asumsi benar)

215200000001075,0'.' sss Ef MPa

002,0

200000

4000134,0003,0

06,95

06,952,520

s

y

ycusE

f

c

cd

Baja tulangan tarik sudah leleh (asumsi benar)

)''.('.)2

..(...'.85,0 11 ddfA

cdbcfM sscn

)612,520(215398,11402

801,802,520300801,802585,0

nM

Mn- = 359,725 KNm

c

d

d'

=

a

d-a/2d-d'

Ts1y

cu' 0,85.f'cd''

d-d''

Ts2

Cc

Cs

As

As'

Perhitungan momen nominal positif penampang:

Diagram tegangan regangan balok induk tumpuan

As = 3D22 (1140,398 mm2)

As1 = 3D22 (1140,398 mm2)

As2 = 2D22 (760,265 mm2)

Asumsi tulangan tarik As leleh dan tulangan tekan As1 belum leleh.

600108265,76060061398,114030085,02585,0

0..'..''.'..'....'.85,0

............'..''

..'..'

....'.85,0

.....'.85,0

0

2

21

2

1

211

2211

21

ccc

cfAEcdAEdcAcbf

cEc

cdAfAE

c

dcAbcf

fAfAfAbaf

TTCCH

ysscusscusc

scusysscusc

ssysssc

sssc

0400398,1140 c

08,91003738.6,684238.75,5418 2 cc

nilai c diselesaikan dengan menggunakan rumus:

a

acbbc

2

42

2,1

mm 865,86amm 018,81

75,54182

8,9100373875,541846,6842386,684238 2

2,1

c

c

Kontrol keserasian regangan:

002,0

200000

40010.412,7

018,81

61018,81003,0

' 41

s

y

ycusE

f

c

dc

Baja tulangan tekan As1 belum leleh (asumsi benar)

24,14820000010.412,7. 411

sss Ef MPa

002,0

200000

40010.991,9

018,81

018,81108003,0

'' 42

s

y

ycusE

f

c

cd

Baja tulangan tarik As2 belum leleh (asumsi benar)

82,199000.20010.991,9. 422

sss Ef MPa

002,0

200000

400017,0003,0

018,81

018,81539

s

y

ycusE

f

c

cd

Baja tulangan tarik As sudah leleh (asumsi benar)

)''.(.)'.(.)2

..(...'.85,0 2211

11 ddfAddfA

cdbcfM sssscn

)61539(24,148398,11402

865,68539300865,682585,0

nM

)108539(82,199265,760

Mn+ = 236,848 KNm