- Phfut d6c va cua ra nhu tran bang.
a) Cit dQce6ng b) Oit ngang e6ng nhieu khoang e) Cit ngang e6n g1 khoang H1nh3-36.Sa d6 tfnh toan 6n djnh ella than e6ng ha
_ V6i tuemg chfut dftt: Tuemg ehfut la cong trinh tuyen dai, nen ta chi dn xet cho 1m chi6u dai tuemg ( c~t bang 1m 0 vi trf tuemg coo oofttde tiOO),S<1db tiOOOOuhinh (3- 37) l:Q, - , . P "II> ,. 'p,".'-P'~ c - c ~'f'A-"~ BA-- ~"k ~ ~--fu
a)T11!attren mlj.tn~n b) M~t 1fl!at ciit qua n~n mnh 3-37. sado tfnh On djnh tuang chiiu dllt
- V6i tI\1 mang: Xet 6n diOOella mQt tI\1 mang ta eo S<1db tiOOtoan OOuhinh (3- 38). Khi xet cac hIc tlie d\lng len t11lpMi xet ca l\fe do thiln mang truy6n xu6ng.
- V6i c6ng ngk: S<1db tiOOtoan tuong t\f c6ng ho.
Trong tftt ell eae S<1db tioo toan, b6 qua tAt ell cae l\fe ch6ng tnrgt, I~t do cac bQ khac ella cong trioo tae dvng len bQ ph~ dang xet.
Trong cae S<1db tiOOtoan:
AB: m~t tnrgt co the xAy ra; B la diem I~t ( hay tam.l~t), AC la gi6i h(Ul ella kh6i dftt sau lung tuemg co the bi I~t theo tuemg.
LQI :T6ng ap l\fc xo ngang ( ill m(it tnrgt AB tro len) eo ehi6u ill phia thugng luu v6 phia hil-luu. LQl g6m: Ap l\fc nuac thugng lUll, ap hIe dftt eM dQng ella dftt phia lung tuOng, ap l\fc Clla dong cMy, ap h;rc ella v~t n6i ...tac dvng len phia thugng luu.
LQ2 :T6ng ap l\fc xo ngang ( ill m~t tnrgt AB tro len) co chi6u til phia hll-luu v6 phia thugng luu. LQ2 g6in: Ap l\fc nuae hil-luu, ap h;rc dftt bi dQng Clla dftt phia bvng tuemg ...tac dvng len phia hil-luu.
LP :T6ng cae l\le th~ng dUng (eo chi6u di xu6ng, gi6i h(Ulb6i m~t AC) tae dvng len m~t AB. LP g6m: TrQng lugng ban thiln, trQng lugng nuae( thugng, hil-luu), trQng Im;mg may moc e6 diOOben tren ...
LW: T6ng ap hIe dAy nguqe (eo ehi6u di len) do ap ~ h;rc thftm va ap l\le tiOO du6i day eong triOO tlic dvng len --
.m~tAB.
Ngoai ra vai tI\1 mang nen xet cae h,rc c~t va l\lc rna sat clla kh6i dftt tren m~t day mong ella t11l( co me dvng eh6ng I~t).
(3-19) Dodo:
- Khi tinh toan l\Ic tac d\Ulg trong timg scr d6, nen phan mQt lo~i l\Ic thanh nhi€u l\Ic, sao cho m~i IVCco the tiOO toan dugc tri 56 vii xac diOO dugc diem d~t Clla l\Ic mQt cach d~ dang (thuoog phan thanh l\Ic co bieu d6 hinh chi!' OO~t,hiOOtam giac ...)
- L\Ic 6 scr d6 tiOO cho than c6ng h6 vii cho tIv mang Iii l\Ic phBn b6 theo the tich, nen khi tinh phili xet S\I phBn b6 l\Ic theo cil phuerng ngang vii phuerng dQc Clla cong trinh; con l\Ic 6 scr d6 tiOOcho tuoog chdn Iii l\Ic phan b6 theo di~n tich nen chi dnxet S\I phBn b6 l\Ic theo phuerng dQc Clla tuoog.
- Khi tiOO toan tri 56 tiOOtoan Clla m~i l\Ic phili xet h~ 56 lech tID ( vugt tID) rieng cho timg lolP l\Ic, timg l\Ic. L\Ic co xu th~ lam cong trinh 6n diOOhern thi Idy tri 56 he 56 lech tID006 vii l\Ic co xu th~ lam cong triOO nguy hiem hern v€ 6n diOOthi Idy tri 56M56 lech tIDIan ( trir cac l\Ic co he 56 I~ch tili n = 1).
He so lech tili tra ph1,1I1,1CPL 1-6
Ap l\Ic ddt len tuoog chdn vii mQt 56 tili trQng thuoog g(\p len cong triOO co the tham khilo cach tiOO6 ph1,1l1,1c4
3. Tinh h~s6 an (Dan vJ 6n ainh (h~s6 6n ainh) a. Tinh h~s6 6n ainh vJ tru(J1phdng KT
LQ~
KT= ----
LQ~
2: Q~ =2:QI - 2:Q2 : T6ng I\IC gay trugt len m(\t trugt AB. 2: Q~ Iii l\Ic xo ngang co chi€u huang v€ phia h~ luu
2: Q~ : T6ng l\Ic ch6ng trugt tren m(\t trugt AB. 2:Q~ =(2:P - 2:W).f+C.FAB
_ (Lp- LW}f+C.FAB
KT- LQ
FAB: Di~n tich Clla m(\t trugt AB.
Vo; tuoog chdn, khi c~t bang 1 m de tiOO thi FAB bfulg chi€u da:i cua do~ thdng AB trong cac scr d6 (hiOO3-37a,b).
Vo; than c6ng h6 FAB = 1. Bm (hiOO 3-36a,b,c).
Vo; tr1,lmang FAB = 1m. Bm (hiOO 3-38). BmIii chi€u rQng mong tr1,l( chi€u song song vo; tIvc cAu mang)
f: He 56 rna sat tren m~t trugt. C: Luc diOOtren mat truert.
Cac trio56 f, C. xa~ dioo biin~ th\Ic nghiem, scr bQ co the Idy gk dUng theo d€ nghi Clla TCVN-57-73 (thiet ke tuoog chan cong triOOthuy cong ) OOusau:
Khi trugt qua m~t n€n :
+ N€n da OOom I, khong bi phong hoa: f=0,75; C= 40 T/m2. + N€n da OOom I, co phong hoa, nUt it: f=0,70, C= 30 T/m2;
+ N€n da OOom II, cuoog dQ trung biOOvii y~u: f=0,65, C= 20 T/m2;
+ N€n cat f= 0,4 +0,5; a cat f= 0,25 +0,35; set f= 0,2 +0,3 (n€n ddt, cat C = 0). Khi m(\t trugt c~t qua n€n ddt (hiOO 3-37b) : f= tg<p; <p,C Iii goc rna sat trong vii I\IC diOOClla ddt n€n.
(3-20)
Khi m~t tmgt AB nghieng mQt goc a. vm m~t p~g nk ng~~, ta pMi phan tAt ca cae luc tMnh h,rc co phu<mg song song va vuong goc vm m~t AB de tinh.
b. Tinh h~ an ajnh v€ 14tKL • , , • " • •
KL bang tAng mo men ch5ng I~t ( nguQ'c kim dong h6 ) chla cho tong mo men gay I~t ( thl$l kim d6ng h6 ) tren hinh (3-36), (3-37), (3-38) vm tam I~t B.
_LM~
KL-" B
L"MGL
LM~L' LM~L: Tflng mo men gay I~t va ch5ng I~t lAy d5i vm tam I~t B. Khi tinh tris5 LM~L va LM~L nen tinh rieng cho timg hrc r6i cQng I~.
--,} L {_
lfmh 3-39. Bieu d6Ung suat day m6ng eua tMn e6ng ha
BA A
3.8. TiNH ToAN KItM TRA NEN CONG TRINH
3.8.1. Khlii nifm