III II I I 00 I 0 I l 02 l 03 l 04 105 l 06 l 07 108 I 09 200 20 l 202 203 204 205 206 207 208 209
KIEM TOAN DAM CHU
3.3.2. CBt thep trong ban m~tdu khi chju momen am
Theo quy d!nh trong D6.10.l.7, dn phai kiSm tra t6ng di~n tich c6t ' thep ban m~t du trong truang hqp ung suAt keo d9c trong ban be tong
yuqt qua <Pf;, khi d6 t6ng di~n tich cua c6t thep d9c trong ban khong duqc . nh6 han 1 % t6ng di~n tich cua ban be tong, ~6i <P = 0,9 vaJ; la cuang d9
chiu keo khi u6n cua be tong:
f,. = 0, 24.jl = 1,3 IMPa D6.10.1.7 (153) Day la truang hqp thuang xay fa d6i v6i vung momen am. Nhu v~y
trong truang hqp nay, di~n tich c6t thep t6i thi~u yeu c~u duqc tinh nhu sau:
1%x2.425.497 = 24.255mm2 D6.10.l.7 (154)
V~y di~n tich c6t thep phan· b6 trong ban m~t'cAu tr'en dAm bien:
be.ff x 24.255mm2 = 5.800mm2
Be . D6.10.1.7 (155)
Trong d6: Bc=l 1,5m la chiSu r()ng du.
Ch9n c6t thep ban m~t du la thep''<i>20, nhu v~y, b6 td hai hr6i c6t thep a th6 tren ban (13 thanh) va m()t lu6i c6t thep a th6 du6i ban (6 thanh). C6t thep ban c6 gi6i h~n chay b~ng.!yb = 400MPa.
Di~n tich c6t thep th6 tren a ban m?t du b~ng Ar1=I3x3 I4 = 4,082mm2
va di~n ti ch c6t thep th6 du6i a ban m?t du b~ng A,.b=6x3 I 4 = l ,884mm2.
3.3.3. M~t c~t ngang dim thep lien hQ'P ban BTCT (tai trQng dai
h~n) - Ti6t di~n chju momen am
cAu
ki~n
Bang 15. D?c trung hinh hQc ddm thep lien hqp ban BTCT
duai tac dt,mg tai tr9ng dai hi,m, 3n = 24
M~tdt Di~n Thong s6 Momen quan tfnh
tfch B~ Chi~u r(mg day (mmA 2 y Ay !,., I ) (mm) (mm3) (mm./) (m:n-1) (mm) (mm) Canh tren 360 30 10.800 55d 5.940.000 3.267.000.000 810.000 Ban bi.mg 1.070 13 13.910 0 0 0 1.327.129.917 Canh du6'i 410 32 13.120 -551 -7.229.120 3.983.245.120 1.119.573 BMC I 15 200 22.917 705 16.156.250 I 1.390. I 56.250 76.388.889 Vitt cht:t 205.335.000 ' 80.000 nh~t 15 40 600 585 351.000 I TBng cc)ng 61.347 15.218.130 20.251.264.749
Khoang each tu tr9ng tam m?t dt t6i tfl,lC trung hoa ban bt,mg:
y;,r = ~ ~ = 248, Imm (156)
Momen quan tinh m?t c~t d6i vai trl,lc trung hoa cua m?t dt:
Iir =Ix -yLT l:Ay = 16.476.137.374mm4 (157)
Khoang each tu trl,lC trung hoa m?t c~t t6i mep tren dftm thep:
y;_~· = 0, 5hw + t, - y;,T ~ 316, 9mm (158) Khoang each tu tfl,lC trung hoa m?t C~t t6i mep du6i ddm thep;
Y~~· = 0,5hw +th+ y;,T = 815,lmm (159) Momen finh m?t c~t d6i v6i tfl,lC di qua mep tren ddm thep:
I- _ //~]' _ . 3
Su - ~ -51.986.309mm (160)
M6men finh m?t dt d6i v6i tn,ic di qua mep du6i dfim thep:
b- - 11~1' - 3
SJ,1' ----;:-- - 20.214.439mm (161)
YJ,1'
Khoang each tu tn,ic trung hoa m?t c~t t&i mep·tren ban m?t du: ...
(162)
Mo men finh m?t dt d6i v6i tn.ic di qua mep tren ban m?t du:·
tH- J;T • :i .
Su =~ = 29.583.738mm
Yo:
(163)
J_.3.4. M~t c~t ngang dAm tltep Hen hQ'p ban BTCT (tai trqng ng~n
h~n) - Ti6t di~n momen am
cAu
ki~n
Bang 16. D?ctruhg'hinh hQc dfimthep lien hqp ban BTCT · · · du6i tac dvng tai tr9ng ng~n h?n, n = 8
. .
Di~n tich Th6ngs6
B~ fi)ng Chi~u day . · · A y . . Ay .
(mm) (mm) (mm2) (mm) (mm3) ... ' . Momen quan tfnh . .,· !,,; . (mm-1) r . ./ (mm) Canh tren 360 30 10.800 550 5.940.000 3.267.000.000 810.000 Banbi,mg 1.070 Canh du6i 41 o BMC V(1tchu· .·. nh~t 344 45 T6ngcQlig·· 13 13.910 . b ' ; i . 0 (327'.129.917 32 13.120 >551 ·"7.229.120 3.983.245.120 1.119.573 200 68.750 705 48.468.750 34.170.468.750 229.166.667 . 40 1.800 585 1.053.00Q . 6.16,.Q05.QOp _.;240.000 ,. ' . ; ·i08.380 : . ·48:232.630 • ; . : .. . .. 43.595J85.027 ·. : . . ·.! , .
Khoang each tu tr~mg tam m?t cat t&i trvc trurig hoa ban bvng:
. _ · :LAy ; . '· . •
Ysr = - - = 445, Omm
LA . 'J ,·
. ' . ~ : : .
Momen quan tinh m~t dt d6i vai tr\lc trung hoa cua m~t cdt:
Tsr =Ix -Ysr :LAY== 22.130.093. 712mm4
Khoang each tu tr\lc trung hoa m~t cdt t6i mep tren dAm thep:
y~~· = 0,5hw +t1 - Y~r = 120,0mm
Khoang each tu tr\lc trung hoa m~t cdt t6i mep du6i dAm thep:
y~~ =0,5hw+tb+Y~r =l.012,0mm
Momen tinh m~t cdt d6i v6i tr\lc di qua mep tren dAm thep:
(165) (166) (167) I - I;T 3 SsT =--;::-= 184.467.516mm (168) YsT
Momen tinh m~t cdt d6i v6i tn.1c di qua mep du6i dAm thep:
b- I;T 3
SsT =-;.:-==21.866.978mm (169)
YsT
Khoang each tu tr\lc trung hoa m~t dt tai mep tren ban m~t cAu:
Momen finh m~t cdt d6i v6i trµc di qua mep tren ban m~t du:
s~~- == I;~~ = 61.478.045mm3
YsT
(170)
(171)
i I