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
3.2.4. Momen dco Ti~t dien ch}u momen dU'O'ng
(136)
(137)
(138)
Momen deo, MP, phai duqe tinh b~ng momen do Ive deo quay quanh tr\lc trung hoa deo gay ra. Cae Ive deo trong phdn thep eua m~t c~t phai duqe tinh v6i euang d() gi6i hi;in ehay eua eae ban eanh, ban b\mg va e6t thep tmmg t'mg. Cae Ive deo trong phdn be tong ehiu nen eua m~t e~t duqe tinh theo bi8u do t'.mg sucit ehiu nen hinh ehfr nh~t phdn m~t e~t be tong v6i t'.mg sucit ehiu nen b~ng 0,85fc. Bo qua phdn be tong ehiu keo (D6.Dl).
Bo qua sv tham gia ehiu Ive eua e6t thep ban m~t cdtt trong vi~e xae dinh momen deo, khi xet thien v~ an to~m (D6.D 1 ). Xae dinh eac Ive deo theo eong thue:
D6i v6i vung betong ban m~t cfiu:
' ~
P,, =0,85/J,.beff =0,85x30x200x2750x10
12 0 0 r- ~ - - - + .. Pw ==::'.'=::::r-:=-$--- J 410 J ~
Iflnh 16. Xac dfnh tr1;1c trung hO,a deo - Tih di?n chfu m6men duang
· D6i v6i vung ban canh chiu nen: . .
~ = FY1b/1 = 345 x 360x20x10-3 = 2.484kN D6.Dl.BD1 (140)
£)6i v6i vung ban bvng:
Pw =Fy.vDtw =345xl.070x12xl0-3 =4.430kN
. . . D6.D l.BD 1 (141) .. D6i v6i vung ban canh chiu. keo:
P, = ~hb6t6 = 345 x 360x20x10-3 = 4.526kN D6.Dl.BD1 (142)
Tn,ic trung hoa deo duqc.ixac dinh thortg qua di@u ki~n can b&ng Ive deo. ,, DoPw+f' • ' j ' · 1. =8,956kN<: Pc+Ps=l6.509kNnen ' tn,ic trung hoa deo khong
1 . , . , , , I . · . . . • , ,
.n&m trenJJ~l} ,bµng;, hal} n(fa P w+P1+Pc=ll.440kN <,Ps=14,.025,k.iY nen tn,1c. trung hoa <feqcfing ~hong n~~ trep ban canh tren. V~y, tn,ic t~ung hoa
dep·n~111 r~e.n p~n ro'~t c&u.yachi~u ca9 y~ng chiu 'n~n'.d~Q'c,tinh ~~ sau:' • • ' , • , , • I , ; • • • - · ' ' • , • • ' , • , , • I , ; • • • - · ' ' • ,
• I'~}~(J'~~i+:J , '.' ~6.Di.IlDl (143)
y ~ w~~ (4A39 +1:;0;6$t + .. 4s41~ 163;1 ~Iii . .. . (144) Khoang each tu tn,ic trung hoa deo t6i trc,mg tam cac d.u ki~n la: Khoang each tu tn,ic trung hoa deo t6i trc,mg tam cac d.u ki~n la:
-D~n tr9ng tam ban m~t d.u: ds = 63,lmm;
- D@n tr9ng tam ban canh tren: de = 96,9mm; ·.
- D&n tr9ng tam ban canh du6i: d1 = I. I 92,9mm.
Gia tri momen deo duqc xac dinh thong qua cong thuc:
-2 Mp= PX + ~.d, + P,,,dw +PA D6.Dl (145) Mp= PX + ~.d, + P,,,dw +PA D6.Dl (145) 2t" 14.025x163, 12 M" = 2x200 +2.484x96,9+4.430x641,9+4.526xl.192,9 = 9.4l6,4kNm (146)