K T C U THP

C BI T

Ch-ng 1 : Kt cu thp bn

$1. i c-ng v kt cu thp bn 1. Phm vi p dng, phn loi -KC thp bn l kt cu -c lm t nhng bn thp. -Dng KC thp bn lm cc cng trnh cha, vn chuyn cht lng, kh, vt liu ri. Cc loi kt cu thp bn: -B cha cht lng: Du, n-c -B cha v phn phi kh -Bunke, xi l: Cha VL ri nh- than, ct, xi mng - ng dn ti n-c, du m, kh (--ng knh ln D>0.6m) -L cao, l t nng khng kh, l ht bi, khi,

2.c im lm vic v cu to iu kin lm vic rt khc nhau: -V tr: + Chn d-i t + Trn mt t - Chu lc: + p lc bn trong + Chn khng +Chu tc dng nhit , mi tr-ng -Yu cu: +Chu l c, m bo bn, n nh +Kn, khng thm +Lm vic trng thi ng sut ln (ch hn, thn-y b), ng sut cc b ln - Vt liu tu thuc tng loi b s dng thp thngth-ng, thp hp kim,

$2. Tnh ton v mng trn xoay Ph-ng trnh c bn tnh v trn xoay chu ti trong i xng trc 1 trc i xng 2 bn knh cong -Bn knh cong ca v R1 R2.)

Quy -c: -Cc kch th- c hnh hc ly theo mt trung bnh ca v (v chiu dy ca v mng) -Cch tnh ph thuc vo trng thi ng sut ca v: -Theo l thuyt momen: S cn bng ca v uc xc nh bi + L c php tuyn N1, N2. + Lc tr-t S1, S2. + Momen un M1, M2. + Momen xon M12, M21. + Lc ct Q1, Q2. -Theo l thuyt phi momen: S cn bng ca v uc xc nh bi + Lc php tuyn N1, N2. (gy ng sut php N1, N2 phn b u theo chiu dy v) + Lc tr--t S1, S2.

Ph-ng php tnh theo LT phi momen ch s dng khi : - T l R/H ln lc v hu nh- khng chu un v vng xa hiu ng bin.

H / R e 1/ 30Th-ng cc cng trinh b n v tho mn iu kin Tnh ton theo l thuyt phi

momen v kim tra ti v tr ni, v tr thay i chiu dy KC (l ni c ng sut cc b)

Tch ra 1 phn t ni xa bin - T i tr ng phn b u theo ph-ng php tuyn ca mt cong ds1ds2 + Lc kinh tuyn + Lc vng

N1 ! W 1ds2H

N 2 ! W 2ds1HdN dE pds1ds 2 ! 2N1sin 2N2 sin 2 2 dN dN dE dE sin ! sin ! 2 2 2 2ds 1 dN ! R1ds 2 dE ! R2

Chiu cc lc ln ph-ng php tuyn

N2 N1 p! R1ds 2 R2ds 1hay

p W1 W2 ! R1 R2 H

- V tr

R1=

W1!

pR2 2H

W2

pR2 ! H

- V c u r 1= r 2 = r

- v nn:

pr W1!W2 ! 2H

W1!

pri 2H cosF

pri W2 ! H cosF

$3. B cha cht lng 1.Phm vi dng, phn loi cha du, xng, kh ho lng, -Theo hnh dng b: + B tr ng + B tr ngang + B hnh cu + B hnh git n-c -Theo v tr trong khng gian: + t cao hn mt t (trn b) + t trn mt t. + t ngm d-i t (n-c) + Na ngm

- Theo th tch: + Th tch khng i (mi tnh, c nh) + Th tch thay i , cn gi l b phao -Theo p lc d-: + B cha p lc thp pd