H"mh4.21. Cac d;mg mat lin dinh cua than dij.p - Trugt tren m(it phdng AB v~ phia h\lluu (hinh 4-2Ia, b) :
Cac 19c hic d\ll1g len m(itAB cua d~p se sinh ra cac 19c gay trugt va ch6ng trugt tren AB. Khi 19c gay trugt Ian hon 19c ch6ng trugt, than d~p se bi trugt.
+ L\lc gay trugt: 1:QI - 1:Q2
+L\lc ch6ng trugt g6m : L\lc rna sat tren AB: (1:P - 1:W).f va l\lc diOOClla m\it trugt AB: C.F.
f, C la h~ s6 rna sat va l\lc diOOclla m\it AB.- Trugt sau ho\ic trugt h6n hQ'P( hiOO4-21 c, d) : - Trugt sau ho\ic trugt h6n hQ'P( hiOO4-21 c, d) :
Trugt sau va trugt h6n hQ'Pchi xAy ra khi nen la dAt va tai trQng thfutg dimg 1611(d?p 1611).Cac d?p 006 kho co the xAy khi ra cac truOng hQ'P nay,trir khi nen quay~u.
- Ngoai ran~u tai trQng thfutg dimg 006, ap l\lc dAy n6i clla dong th&m 1611,d?p co th~ bi dAy n6i len tren ( Dieu nay chi co y nghia ve m\it Iy thuy~t vi th\lC t~ d?p co th~ bi dAy n6i len tren ( Dieu nay chi co y nghia ve m\it Iy thuy~t vi th\lC t~ kho co th~ xay ra truOng hQ'Pnay).
b. Cae dr;mg co thd mat 6n ainh cua cae bi) ph{jn khde eua a{jp
- TUOng chfut dAt ( tuOng ben, tuOng caOO): N~u tUOng xiiy .rm vm mongho\ic xay rai vm phAn day cong triOO ( than d?p, san truac, san sau ) thi duai tac ho\ic xay rai vm phAn day cong triOO ( than d?p, san truac, san sau ) thi duai tac d\ll1g (chll y~u ) clla ap l\lc dAt xo ngang, tuOng cling co th~ bi mAt 6n djnh OOu than d?p, tuy OOien cac b(l ph?n nay thuOng tai trQng thdng dimg 006, nen chi xAy ra trugt phfutg va I?t.
- Tf\I pin clla d?p n~u khong xay lien vm than d?p, khi l\lc XO ngang cllanuac thUQI1g luu 1611,ho\ic khi m(lt khoang dang co nuac 1611,m(lt khoang dang nuac thUQI1g luu 1611,ho\ic khi m(lt khoang dang co nuac 1611,m(lt khoang dang thao C(lllnuac d~ sua chUa cling co th~ xAy ra I?t ho\ic trugt phdng. Tuy nhien tf\I pin thuOng xay lien vm than d?p nen truOng hQ'Pnay khong xAy ra.
- Cac tAm lat m\itah(l.luu d?p, khi ap l\lc dAy n6i clla dong th&m 1611co th~bi dAy n6i len tren. bi dAy n6i len tren.
- Cac b(l ph?n bao v~ hai vai thuQI1g, h(l.luu d?p co th~ bi trugt OOu d6i vaib(l ph?n bao v~ mai thUQI1gClla d?p d&t. b(l ph?n bao v~ mai thUQI1gClla d?p d&t.
2. Cae truUng h(F[Jtinh toan 6n ainh than a{jp
Khi tiOOtoan 6n diOOthan d?p cAn tiOOcho cac truOng hQ'P sau:
- TruQI1g hQ'P I : ThuQI1g luu la MNDBT, h(l. luu la m\lc nuac thAp ooAt (ho\ic khong co nuac) ( khong co d(lng dAt ). ho\ic khong co nuac) ( khong co d(lng dAt ).
- TruQI1g hQ'P2 : ThuQI1g luu la MNDGC, h(l.luu la m\lc nuac tuang img khithao IUthi~t k~. thao IUthi~t k~.
(4-18)
Truang hW I thuQc t6 hw tid trQng ca ban, truang hW 2 thuQc t6 hW tai trQng $c biet.
- Ngoai ra n6u nen d~p la ddt, phai tiOO cho truang hW thUQIlg hfi.luu deukhong co nuac ( thuang chi tinh vai d~p Ian ) va truang hW thi6t bi thOllt nuac