C=A
"t
"t - Chu kY song
"t = ~27tA .cth 27tH
g A
Trang cac cong thuc tren: g Iii gia t6c tr9ng wang
Tung dQ bi~u db t(li day biJ ch~n song (Pc):
(3-23)(3-24) (3-24) (3-25) (3-26) (3-27) p, = P;
3.2.4. A.p l,!c ddt U\n tlril'Dg ch~n
1. Khcd ni~m
Hinh 3.8 mo ta sa db Iilm vi~c cua mQt wang ch~n dk M(it BD aphia d~p d~t nhi~u g9i Iii lung wang, m(it AB a phia khong d~p d~t ho(ic d~p d~t it g9i Iii b\lng tuang. H Iii chi6u cao tuang, B Iii chi~u rQng day Wang. Khi Iilm vi~c wang vii kh6i d~t sau lung Wang co th~ dUng yen ho(ic co th~ bi dich chuy~n v6 phia lung hay b\lllg Wang;Tir do ap h,rc d~t len wang se khac nhau.
Kh3i d~tco th~hitrugt *~ M~ttr,fm co th~xay ra . ... " c j_B_~ A
Hinh 3.8. Sa db him vi~e eua tuimg ehim d~t B\Jng tuimg ,'
TUOng ch~n cUng Iii tlIOng chfu duQ'c coi Iii khong bi bien d::mg trong qua trinh chiu hJc. Cac IO(litlIOng ch~n d(lilg tr9ng hJc, d(lilg cong son... b~ng be tong, be tong c6t thep, da xiiy, g(lch xiiy... khi tinh coi Iii tUOng J:
ch~n cUng.
Ap h,rc d~t len tUOngch~n Iii rn(lt v~n d~ phUc t(lP, trong gi6'i h(ln clla chuemg trinh chi gi6'i thi~u cach tinh toan theo phuemg philp can b~ng gi6'i h(ln di~m
clla Riingkin cho SO' d6 dem giiin: Lung tlIOng thAng dUng, rn(it d~t n~rn ngang vii cao ngang dinh tUOng,co th~ co tiii tr9ng phiin b6 d~u q hay h,rct~p trung P tren rn(it d~t vii bo qua IlJcrna sat gifra d~t vii lung tlIOng(rna sat tren rn(itBD).
Khi tinh toan ap hJc d~t len tlIOng, thuOng dt bang r(lng 1 met theo chi~u diii tlIOngd~ tinh.
f)~xac dinh tri s6 vii di~rn d(it clla ap IlJcta nen dung phuemg phap phiin bi~u d6: Phiin bi~u d6 thiinh cac bi~u d6 demgiim (chfr nh~t, tam giac) d~ tinh.
2. CaeIO(Ji ap h.e ddt len tuimg eh6n
Khi tinh toan ap IlJcd~t len tlIOngch~n dn phiin bi~t cac IO(liap h,rcd~t nhu sau: - Ap IlJcd~t tinh (ap IlJcd~t ngung) - Hqp IlJcky hi~u: Eo - (Hinh 3.9)
Ap IlJc d~t tinh Iii ap IlJc d~t tac d\lng len lung wOng khi tlIOng dUng yen ho(ic duQ'ccoi Iii dUng yen (tlIOngco chuy~n vi ngang nha hem 1/5000 chi~u cao tlIOng).
- Ap IlJc d~t chu d(lng - Hqp llJcky hi~u: Ec - (Hinh 3.10)
Ap l\Ic d~t chll d(lng Iii ap hJc d~t tac d\lng len lung tlIOng khi tlIOng b~t dau chuy~n vi v~ phia b\lng tUOng.
- Ap l\Ic d~t bi d(lng - Hqp I\ICky hi~u: Eb - (Hinh 3.14)
'Ap hJc d~t bi d(lng Iii ap IlJc d~t tac d\lng len lung tlIOng khi tlIOng b~t dau chuy~n vi v~ phia lung tlIOng va chuy~n vi cua tlIOngdu d~ t(lOra kh6i dat truqt 6' lung tlIOng.
N goai ra con co ap Ive (liit bi dl)ng khong ep trbi - HQ'P Ive kY hi~u: Ebo - la ap Ive dat tae d\ll1g len lung tuang khi tuang b~t ddu ehuy8n vi v8 phia lung tuang va ehuy8n vi ella tuang chua dll d8 tl;lorakh6i dat trugt alung tuang.
3. Tinh toan ap l1"c adt tfnh (Eo)
N€u tren m(it dat co tili tr9ng philn b6 d8u thi bi8u db ap Ive la tbng ella 2 bi8u db: ap Ive do dat va ap Ive do tili tr9ng phan b6 d8u q tae dVng len lung tuang gay ra (HiOO 3.9).
Cuang dl) phiin b6 ap Ive do dat gay ra adl) sau z so v6i m(it dat:
(3-28)Cuang dl) phiin b6 ap Ive do q gay ra la ap Ive philn b6 d8u tren lung tuang: Cuang dl) phiin b6 ap Ive do q gay ra la ap Ive philn b6 d8u tren lung tuang:
Hinh 3.9. Bii\u db aph!,c d:lt tInh
(3-29)I' 1 I' 1 ' , y~H eoq =qC;o y - Tr9ng Iw;mg rieng ella dat sau lung tuang.
So - H~ s6 ap Ive hOngella dat, tiOO theo eong ella dat, tiOO theo eong thue:
110 - H~ s6 na hongella dat, xae diOO bimg ella dat, xae diOO bimg thi nghi~m. Vai OOilng eong triOO 006 ho(ie khi thi€t k€ co sa co th8 lay
So OOusau:
Dat set: So= 0,7; Dat a set: So= 0,5; car: So= 0,4;
(3-31)Ho(ie co th8 tinh toan theo eong thue ella Jaky: So = 1- simp Ho(ie co th8 tinh toan theo eong thue ella Jaky: So = 1- simp
Trang do <pla goe rna sat trang ella dar. Khi khong co titi tr9ng q thi eoq =O.
Khi tiOOtoan ta co th8 tinh rieng do tae d\ll1gatUng bi8u db rbi el)ng tae dVng Il;li ho(ie dung bi8u db tbng d8 tiOO.
4. Tinh ioim apb,rcddt chit d{jng(Ee)
* Tr140ng hr;p ddt sau ltrng t140ng lil ddt rm, kh6ng co tai tr(Jng ben tren (Hinh 3.10)
Ap h,rc ddt chll dQng trong truOng hQ'Pddt Ia ddt rai, lung luOng th~ng dtmg, rn~t ddt n~ ngang, khong tai tn;mg bentren la M'{-''{- .{- .{- .{-
truOng hQ'P dan giim nhdt. Bi~u db ap h,rc ,ON
co dl;lng tam giac, cuOng dQ phan b6 ap" h,rc a dQ sau z so vai m~t ddt tinh theo.
cong thuc: :c E,
(3-32)
Ae - H~ s6 ap h,rc ddt cM dQng doanh huang clla goc rna sat trong <p. anh huang clla goc rna sat trong <p.
(3-33)
A B
" YAoH ,f Hinh 3.10. Bi~u db aph,re dfrt ehi! d9ng
eua dillrai
* Tr!rOng hr;p ddt sau l!rng t!rl3nglil ddt dinh, co tai tr(Jngphdn b6 dtu q ben tren
(Hinh 3.11)
TruOng hQ'Pnay ta cling dUng phuang phap cQng tac d\rng d~ tinh: Bi~u db t6ng la t6ng clla 3 bi~u db sau: