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
3.2.5. Momen chay-Ti~t di~n chiu momen dU'O'ng
Momen chay, M_v, cua mi;it c~t lien hqp la momen gay ra hi~n tuqng
chay dftu tien a canh dftm thep (ban canh du6i hoi;ic ban canh tren).
Theo quy dinh trong D6.D2.2 thi momen chay cua mi;it c~t lien hqp trong vung morhen duang phai duqc lfiy b~ng t6ng cac momen tac dt,mg vao mi;it c~t a tung giai do~n nhu mi;it c~t thep chua lien hqp, mi;it c~t lien hqp tuc thai va mi;it c~t lien hqp dai h~n d~ gay ra ung sufit chay danh dinh SO' dp a m9t trong ca hai ban canh a tr~ng thai gi6i h~n cuang d(). Khong xet d&n u6n ngang ban canh cua tfit ca cac lo~i mi;it c~t va chay cua ban
bi,mg mi;it c~t.lai trong tinh toan nay.
Nhu v~y, momen chay duqc tinh nhu sau (D6.D2.2):
- Tinh momen, MDJ; gay ra b&i finh tai thuang xuyen tinh toan tru6c khi ba11 be tong dong clrng hay. tru6c khi lam vi~c li~n hqp. Momen nay tac di,mg vao mi;it dt dftm thep.
- Tinh momen, Mm, gay ra do tai tr9ng tinh toan cua phftn finh tai con
l~i. Momen nay tac d\lng vao mi;it dt lien hqp dai h~n.
- Tinh momcn tac d\lng them, MAD• gay ra do ho~t tai tac d\lng them, d~
khi tac d\lng vao mi;it c~t lien hqp tlrc thai gay ra uhg sufit chay danh dinh trong tung ban canh.
- Momen chay la t6ng cua toan b9 momen do finh. tai va momen tac d\lng them.
Vi momen finh cua truang hqp ti&t di~n lien hqp ng~n h~n d6i v6i bien tren cao han rfit nhiSu so v6i momen finh cua ti&t di~n lien hqp ng~n h~n
d6i vai bien <luai cua <lAm thep nen momen chay se la momen gay ra chay bien du6'i tru6'c.
Do v~y, momen tac d\mg them MAD duqc tinh thong qua phuang trinh:
f, = MJ)I + MD2 +MAD y S~~ s 2; Sc~; D6.D2.2.ED1 (147) M AD =sh+ x(f, -MDI - Mm) (148) ST y sh+ sh+ NC · J,T M = 2 1.492.166 x(345 _1.181,7x106 _649,2x106 )· AD 15.018.998 19.931.193 (149) = 5.023, 7xl06 Nmm = 5.023, 7kNm Trong d6:
. MDI: Momen do finh tai DCJ tac di.mg len <lAm thep chua lien hqp, tf;li
m~t c~t 104, MDI= l,25MDcJ = 1.181,7kNm. .
st~: Momen khang u6n cua m~t c~t d6i v6'i tn,1c di qua mep du6'i <lAm thep (tist <lien chua lien hqp), st~= 15.0J8.998mm~.
Mm: Momen do tinh taiDC2 vaDWtac di.mg Ien dAm thep lien hqp
ng~n hf;ln, tf;li m~t c~t 104, MDI = l,25MDc2+ l,5MDw = 649,2kNm.
s~;: Momen khang u6n cua m~t c~t d6i v6'i tr1,1c di qua mep du6'i dfrm thep (tiSt;dien lien hqp ng~n hf:ln), s~; = 21.492.166mm3.
Sf~: ·Momen khang u6n cua m~t c~t d6i v6'i tr1,1c di qua mep du6'i dAm thep (tiSt <lien lien hqp dai hf:ln), sf~ = l 9.93 l .193m,h3.
· Tu d6 ta tinh duqc momen chay:My:
D6.D2 (150)