an mn hoc:Thit k Cu BTCT PHN 2THIT K K THUTChng1:THIT K BN MT CU1. Tnh ton ni lc trong cc tit din ca bn:* Nhn xt: Gi La chiu di tnh ton ca nhp 36 m La = 33,2 mGi Lb chiu di tnh ton ca bn theo phng ngang cu Lb = 1,9 m9 , 12 , 33baLL >>2. bn lm vic theo kiu bn k 2 cnh. tnh ton bn ta ct 1m rng bn theo phng dc cub d e c a 1.1.Tnh ton ni lc bn hnga)Tnh ti tc dng:Cc b phn kt cu c tnh cho 1m chiu rng bnDC1: Trng lng bn mt cuDC1 = 0,2.1,9 = 0,38 T/m =3,728 KN/m DC2: Trng lng lan can , tay vn trn mt mt di cuDC2 = 0,9524/2 T/m= 0,4762 T/m = 4,672KN/mLp ph mt cu theo 1 mt ngang cu:DW = 2,9172/10,4 T/m =0,2805 T/m = 2,752 KN/mb) Hot ti do xe tc dng:Hot ti xe thit k n gin tnh ton nn chn ti trng bnh xe c m hnh ha nh ti trng tp trung:

hll+h b+hbDin tch tip xc ca bnh xe v mt ng-Chiu rng (ngang cu) b = 510mm-Chiu di dc cu:Trang

an mn hoc:Thit k Cu BTCT l= 2,28x103 n+(1+pIM)100-n h s ti trng ca t-IM-lc xung kch(%) ly theo bng 3.6.2.1.1-p-ti trng bnh xe (0,5HL93)P= 0,5.145000/2= 36,25 KN(cho xe ti)Din tch phn b ca bnh xe ln b mt bn-chiu rng= b+h = 510+200= 710 mm-chiu di (dc cu): lTi trng bnh xe quy v 1 bng ti chiu di (b+hf) theo phng ngang cu c cng phn b cho 1m b rng bn:Xt mt bnh xe nng ca xe ti thit k c ti trng P t cch mp g lan can 300 mm .Khong cch t tim bnh xe ti ngm x=150 mm .Chiu rng bn tng ngE=1140+0,833.x=1140+0,833 x= 1264,95mm =1,26495 >1,0mLL=E h bP) ( +=26495 , 1 ). 2 , 0 51 , 0 (25 , 36+=40,362 KN/mc): Hot ti ngi i : PL= 3.1= 3 KN/mTnh ni lc ti bn hng:- H s xung kch: IM=25%DC- H s ti trng tnh ti ca bn mt cu, DC=1,25DW- H s ti trng tnh ti ca lp ph mt cu, DW=1,5LL - H s ti trng ca hot ti, LL=1,75 - Din tch ng nh hng ca M - H s iu chnh ti trng : trong iu kin bnh thng chn = 1Xt cu to th xy ra 2 trng hp:thc t c +Bn ch c tnh ti v ti trng tM men ti ngm:DWDC1LLDC2L1L2L3L41]1

+ + + + 2. ). 1 .(2. . .2.24232 2211 2 /LLL IMLDW L DCLDC MLL DW DC DCCDIs =1.(1,25.3,728.295 , 02+1,25.4,672.0,7 + 1,5.2,752235 , 02+1,25.1,75.40,3622150 , 02)= 15,383 kN.mLc ct ti ngm:V = 1(1,25.3,728.0,95+1,25.4,672+1,5.2,752.0,35+1,25.1,75.40,362.0,45)= 51,443 KN+Bn hng ch chu tnh ti v ngi i bTrang

an mn hoc:Thit k Cu BTCT 1]1

+ + + 2. .2. . .2.24232 2211 2 /LPLLDW L DCLDC MPL DW DC DCCDIs =1.(1,25.3,728.295 , 02+1,25.4,672.0,7 + 1,5.2,752235 , 02+ 1,75.3.2450 , 02)= 6,975kN.mLc ct ti ngm:V = 1(1,25.3,728.0,95+1,25.4,672+1,5.2,752.0,35+ 1,75.3.0,45) =14,074 KN/m1.2.Tnh ni lc bn kiu dm: 1.2.1.Tnh ton m men dng: i vi bn ca cu dm c th phn tch nh di bn lin tc k trn cc dm ch.V nguyn tc phi tnh bn k trn ngm cng xt dm 2 u ngm nhng vi cha s dng c tin hc ng dung nn a s 2 u ngm thnh s tnh inh tnh ton theo phng php gn ng:Tr s m men ti mt ct gia nhp ca bn 2 u ngm xc nh theo cng thc sauM+0,5l =k.M00,5lM00,5l M men do ngoi ti gy ra ti mt ct gia nhp bn gin n

05 , 0 LM=[DC1.DC1.MDC1 +DW.DW.MDW +LL(1+IM).LL.MLL]k-h s iu chnh ly bng 0,5- Tnh ti tc dng:DC1 = 3,728 KN/m (tnh cho nhp ngang di 1,9m)DW= 2,752 KN/m (tnh cho nhp ngang di 1,9m- Hot ti tc dngXc nh b rng di tng ng theo phng dc cu+M men dng:E+= 660+0,55.S = 1705mm S Khong cch gia cc cu kin k . S=1900mm*Tc dng ca bnh c th quy v mt bng ti trn b rng(b+h) c cng :LL=E t bPs). (2 /+=705 , 1 ). 2 , 0 51 , 0 (25 , 36+ = 29,945 KN/m+Ti trng ln : Ch xt khi di bn ngang c L>4,6m , hoc bn lm vic theo phng dc cu . y L 0,03yCff,Vy mt ct tha mn v hm lng ct thp ti thiu C ly ti a gia cc thanh ct thpTheo TCN 5.10.3.2 trong bn c ly gia cc ct thp khng c vt qu 1,5 chiu dy cu kinhoc 450mm.Smax 1,5x200 =300mm2.1.3. B tr ct thp phn b dc bn mt cu (tnh cho 1m ngang cu) +Phi t ct thp ng hng, fy >= 400 MPa +Ct thp t cng gn cc m ngoi cng tt nhng phi m bo lp b tng bo v. +Lp y: Theo tnh ton th ct thp theo phng ngang( thp chu lc trong bn ) l 6 thanh 12, din tch l 678,24 mm2, theo phng dc cu b tr thp 410 trn 1 mt ngang cu; a=200,c din tch l 314 mm2 > 25% x 678,24 = 169,56 mm2. Tho. +Lp nh: B tr tng t lp y Khong cch ln nht gia cc ct thp l 250mm2.2. Kim tra iu kin khng ct:Kim tra theo cng thc: VVn Trong : V Lc ct tnh ton -h s sc khng ct c ly theo bng 5.5.4.2-1, =0,9 Vn sc khng ct danh nh c tnh theo iu 5.8.3.3Sc khng ct danh nhVn phi c xc nh bng tr s nh hn ca :Vn =Vc + VS+VpVn = 0,25 fc .bv.dv. +VpTrong : Vc:sc khng ct ca b tng ; Vc =0,083. c f . bv.dv VS:sc khng ct danh nh ca ct thp VS =sg g dv fy Av sin ). cot (cot . . +Trong :bv-b rng sn dm nh nht trn chiu cao dvTrang

an mn hoc:Thit k Cu BTCT dv-chiu cao chu ct hu hiu c xc nh trong iu(mm)s-c ly ct thp ai (mm) -h s ch kh nng ca b tng b nt cho truyn lc ko c quy nh trong -gc nghing ca ng sut nn cho c xc nh trong iu 5.8.3.4()

-gc nghing ca ct thp ngang i vi trc dc()AV-din tch ct thp chu ct trong c ly s (mm2) Vp-thnh phn d ng lc hu hiu trn hng lc ct tc dng,l dng nu ngc chiu lc ct (N)V bn khng b tr ct thp d ng lc nn ta b qua thnh phn VP +c bV=1000m +dv=chiu cao chu ct hu hiu,c ly bng c ly o thng gc vi trc trung ha gia hp lc ko v lc nn do un,nhng khng cn ly t hn tr s ln hn ca 0,9de hoc 0,72h(mm). Chn dV max t 3 gi tr sau: 0,9de = 0,9.(200-60)=126(mm) 0,72h = 0,72.200 =144(mm) 200-60-25=115(mm). Vy dv=144 mmTa c Vn xc nh theo 5.8.3.3-3 l:Vnl= Vn = 0,25 fc .bv.dv. = 0,25.40.1000.144=1440000N=144T+Xc nh v -phng php n gin i vi nhng mt ct khng d ng lci vi cc mt ct b tng khng d ng lc khng chu ko dc trc v c t nht mt lng thp ngang ti thiu trong quy nh hoc c tng chiu cao nh hn 400mm,c th dung cc gi tr sau y:

=2,0= 450 Ta c h =200mm nn =2,0 : = 450 . +=900. VC= 0,083.2. 40 .1000.144= 151182,17N=151,18 KN Vc=151,18 KN > 57,924 KNkhng cn phi tnh VS naVy iu kin khng ct c m bo. 2.3. Kim tra bn mt cu theo trng thi gii hn s dng ( Kim ton nt):Theo TCN 5.5.2 cc vn phi kim tra theo trng thi gii hn s dng l nt, bin dng v ng sut trong b tng.Cc cu kin phi c cu to sao cho ng sut ko trong ct thp trng thi gii hn s dng saf khng c vt qu :1/30, 6( . )s sa ycZf f fd A Trong :cd: Chiu cao phn b tng tnh t th ngoi cng chu ko cho n tm ca thanh hay si t gn nht; nhm mc chtnh ton phi ly chiu dy tnh ca lp b tng bo v cd khng ln hn 50mm.Trang

an mn hoc:Thit k Cu BTCT Z: Thng s b mt vt nt (N/mm) .Ly Z=23000N/mm i vi cc cu kin trong mi trng khc nghit v khi thit k theo phng ngang. + saf: ng sut ko trong ct thp trng thi gii hn s dng+ A: din tch phn b tng c cng trng tm vi ct thp ch chu ko v c bao bi cc mt ct ca mt ct ngang v ng thng songsong vi trc trung ha chia cho s lng cc thanh hay si (2mm ).Vic tnh ng sut ko trong ct thp do ti trng s dng da trn c trng tit din nt chuyn sang n hi (A5.7.1 ).Dng t s moodun dn hisEca ct thp l 200.000 MPa (A5.4.3.2) Moodun dn hi ca cE c cho bi: Ec= 0,043.'25 , 1.c cf =0,043x24001.540 = 31975,35MPaVy n = 200000/31975,35 = 6,25Dng n = 6,252.3.1. Kim ton nt i vi momen dng:- Momen dng ln nhtsdLM5 , 0 =[DC1.DC1.MDC1 +DW.DW.MDW +LL(1+IM).LL.MLL]=1.(1,25.3,728.0,451+1,5.2,752.0,451+1,75.1,25.29,945.0,26) = 20,995(KN.m)-Mu= 0,5 .20,995 = 10,497(kN.m)+ Tnh fs :- Tng momen tnh i vi trc i qua cnh di ca mt ct: S = b.h.(h/2) + n.As.d + n.As.d. Vi d = (25 + 12/2) = 31 mmd = (200-60-12/2) = 134 mmAs = 678,24 mm2As = 678,24 mm2 S = 1000.200.200/2 +6,25.678,24.31+6,25.678,24.134 => S = 20,699.106 (mm3)+ Din tch mt ct : A = b.h + n.As+ n.As = 1000.200 + 6,25.678,24+6,25.678,24 = 0,208478.106 (mm2)- Khong cch t trc trung ha n mp di ca mt ct:y = AS=6610 . 208478 , 010 . 699 , 20 = 99,286 (mm)- Momen qun tnh ca mt ct: Icr =( )3b. h y12+n.As.(y-d)2+ n.As.(d-y)2 =12) 286 , 99 200 ( 10003+ 6,25.678,24(99,286-31)2 +6,25.678,24.(134-99,286)2 = 1,1.108 (mm4)- ng sut ko ca ct thp di bng:Trang

an mn hoc:Thit k Cu BTCT fs = n.

,_

crId) - M.(y= 6,25x

,_

81,1.1031) - (99,286610,497.10= 40,73 (Mpa)- de = d = 31(mm) < 50 (mm)+ Din tch b tng c cng trng tm vi ct thp ch chu ko v c to bicc mt ct ca mt ct ngang v ng thng song song vi trc trung ha, chia cho s lng cc thanh :A = 62200 . 31 . 2= 22733 (mm2)- Z = 23000 (N/mm)=> fsa =1/3cZ(d .A)= 31) 22733 . 31 (23000= 258,45 Mpa > 0,6.fy= 0,6.420 = 252 MPafsa = 258,45 Mpa fs= 64,69 (Mpa) => tha mn.2.3.2. Kim ton nt i vi momen m:05 , 0 LM=[DC1.DC1.MDC1 +DW.DW.MDW +LL(1+IM).LL.MLL]=1.(1,25.3,728.0,451+1,5.2,752.0,451+1,75.1,25.32,01.0,26)= 22,169 (KN.m)sdLM5 , 0 = -0,8 .22,169 = -17,735 KN.m- Momen m ln nhtMu= - 17,735(kN.m)- Khong cch t trc trung ha n mp trn ca mt ct:y = 200 99,286 = 100,714mm- Momen qun tnh ca mt ct: Icr =( )3b. h y12+n.As.(y-d)2+ n.As.(d-y)2=12) 714 , 100 200 ( 10003+ 6,25.678,24.(100,714-31)2 +6,25.678,24.(134-100,714)2=1,068.108 (mm4)- ng sut ko ca ct thp di bng:fs=n.

,_

crId) - M.(y=6,25

,_

+ 81,068.10617,735.10 ) 2 / 12 60 ( 714 , 100 (= 36,028 (Mpa) - de = d = 66(mm) >50 (mm)- chn de = d = 50(mm)+ Din tch b tng c cng trng tm vi ct thp ch chu ko v c to bicc mt ct ca mt ct ngang v ng thng song song vi trc trung ha, chia cho s lng cc thanh :A = 62200 . 50 . 2= 36667(mm2)- Z = 23000 (N/mm)=> fsa =1/3cZ(d .A)=31) 36667 . 50 (23000= 187,92 Mpa < 0,6.fy= 0,6.420 = 252 MPafsa = 187,92Mpa fs= 59,19 (Mpa) => tha mnTrang

an mn hoc:Thit k Cu BTCT Chng II: THIT K DM CH BTCH ST Thit k dm ch gia (s 03) cng sau Phng n 1 nhp 34 m1. Cc c trng vt liu ca dm ch :1.1. Thp :I.1.1.Thp ng sut trc :S dng thp tao 15,2mm .Dintch 1 tao 140mm2-Cng ko quy nh ca thp ng sut trc :fpu= 1860 Mpa-Gii hn chy ca thp ng sut trc:fpy= 0,9.fpu=1670 Mpa-M un n hi ca thp ng sut trc :Ep= 197000 Mpa-S dng thp c chng thp ca hang VSL :Tiu chun ASTM A416 Grade 270-ng sut trong thp ng sut khi kch :Trang

an mn hoc:Thit k Cu BTCT fpj = 0,8fpu =1488 Mpa-ng sut trong thp sau cc mt mt trong cc giai on khc :0,8.fpy=0,8.1760=1336 Mpa-Chiu di tt neo :neo m L 1 / 002 , 0 I.1.2.Thp thng :Gii hn chy ti thiu ca ct thp thanh :fy = 420 Mpa.M un n hi :Es=200000 Mpa.1.2.B tng :T trng ca b tng :c=24 KN/m3Cng chu nn ca b tng quy nh tui 28 ngy fc= 40 MpaCng chu nn ca b tng lc bt u t tihoc to ng sut trc :fci=0,85. fc =34 Mpa .M un n hi ca b tng lm dm :Ec=0,043.1,5c ' fc= 31975,35 Mpa .M un n hi ca b tng lm dm lc cng ko :Eci = 0,85.Ec = 0,85x31975,35 = 27179,05 Mpa .H s quy i hnh khi ng sut (5.7.2.2):1 = 0,85 0,05x7) 28 f' ( c 0,764 Mpa .Cng chu ko khi un : ff = 0,63. ' fc= 3,98 Mpa .2. B tr chung mt ct ngang cu :Chiu di ton dm l 34 m hai u mi u 0,4 m k ln gi chiu di tnh ton ca nhp l 33.2mCu gm 6 dm T ch to bng b tng c fc =40 Mpa .Lp ph mt cu gm lp phong nc dy 0,4 cm v lp ph o ng bng b tng nha dy 5cm .1 > Chnmt ct ngang dm ch nh chn trong phn thit k s b :Chiu cao ti thiu (gm c chiu dy bn ) hmin = 0,045.L = 0,045.33,2 = 1,49 m .Chiu rng bn cnh c hiu [A.4.5.2.6.1 ]Chiu di nhp c hiu 33,2 mDm gia: b rng bn cnh hu hiu c th ly gi tr nh nht ca : 1/4 nhp c hiu = 0,25.33,2 =8,3 mb { 12tS +0,5,bf = 12.0,2+0,5.1,6/2 = 2,8 m }Tim n tim dm ch = 1,9 m b rng bn cnh be= 1,9 m3.T hp ti trng :3.1.Tnh ton ni lc dm ch do tnh ti : + Ti trng bn thn dm ch DCdc DCdc = 2 , 3381 , 9 . 916 , 77= 23,022kN/m + Ti trng do dm ngang DC1dn DCdn =6 . 2 , 3381 , 9 . 9339 , 12 = 0,637kN/m + Ti trng do lan can tay vn DC2 Trang

an mn hoc:Thit k Cu BTCT DC2 =0(do gi thit rng ton b ti trng lan can tay vn do dm bin chu ) + Ti trng ca lp ph DW DW = 681 , 9 . 9172 , 2 = 4,769kN/mBng tng kt :DC1 (dm ch) 23,022 kN/mDC1(dm ngang) 0,637 kN/mDW(pmc) 4,769 kN/mCc h s tnh ti c ly theo 22TCN- 05 Loi ti trng TTGH CD1 TTGH S dngDC:cu kin v cc thit b 1,25 : 0,9 1,0DW: Lp ph mt cu 1,5 : 0,651,03.2.Xc nh ni lc :Tnh ton dm ch ti 4 mt ct:L21; L83;L41;L81;ti gi v cch gi 2,7 m .- xc nh ni lc ta v cc ng nh hng cho cc mt ct cn tnh ri xp tnh ti ri uln ng nh hng .+Ni lc xc nh theo cng thc sau :Trng thi gii CI+M men : Mu = (DC DC + DW DW)+Lc ct: Vu = (DC DC + DW DW) Trng thi gii hn s dng+M men : Mu = ( DC + DW)+Lc ct: Vu = ( DC +DW) Mc ch to hiu ng ln nht.-din tch ah m men ti mt ct ang xt+-din tch ah dng ta mc ang xt--din tch ah m ti mc ang xt- h s lien quan n tnh do ,tnh d xc inh theo TCN 1.3.2=i. d. R 0,953.2.1.M men :ng nh hng m men ti cc mt ct : :L21;L41;ti gi v cch gi 0,8m . 8.3DCDWDAHL/2ng nh hng ti mt ct L/2Trang

an mn hoc:Thit k Cu BTCT

DAHL/4DWDC6,225ng nh hng ti mt ct L/4 DAHCchgoi0,8mDWDC0,781 ng nh hng ti mt ct cch gi 0,8 mTrng thi gii CI+M men : Mu = (DC DC + DW DW) = 0,95. (1,25.DC + 1,5.DW)Trng thi gii hn s dng+M men : Mu = ( DC + DW) = 0,95.(DC + DW)Ta c kt qu tnh ton mmen bng sau:Tit dinL(mm)XK(mm)L-XK(m)YK(m)(2m )McdI(KN)Msd(KN)L/2 33200 16600166008.300137.78 4807.282 3721.024L/4 33200 8300249006.225103.34 3605.636 2790.9030,8 m 33200 800 32400 0.781 12.96 452.1874 350.0107Gi 33200 0 33200 0 0 0 0Max 4807.282 3721.0243.2.2. T hp lc ct:ng nh hng lc ct ti cc mt ct : :L21;L41;ti gi v cch gi 0,8 m .Trang

an mn hoc:Thit k Cu BTCT DAHL/20.5DC4,15 m20.5DW4,15 m2ng nh hng ti mt ct L/21,038 m2DW0,759,338 m2DC0.25DAHL/4ng nh hng ti mt ct L/4ng nh hng ti mt ct L/80,016 m2DW0,96115,568 m2DCDAH0,8m ng nh hng ti mt ct x=0,8mDAH0mDC16,6 m21DWng nh hng ti mt giTrang

an mn hoc:Thit k Cu BTCT Trng thi gii CI+Lc ct: Vu = 0,95.((1,25.DC + - 0,9DC.-)+(1,5DW.+ -0,65DW.-)Trng thi gii hn s dng+Lc ct: Vu = 0,95.(DC.+ -DC.- + DW+ -DW.-) Ta c kt qu tnh ton lc ct bng sau:Tit dinL(m)XK(mm)L-XK(m)YtrYph-(2m )+(2m )Vsudung(KN)VCDI(KN)L/2 33.2 16.616.60.500 0.5004.150 4.150 048.63074L/4 33.2 8.324.90.250 0.7501.038 9.337224.1278301.72890,8 33.2 0.832.40.039 0.9610.016 15.568420.0066542.8217Gi 33.2 0.033.20.000 1.0000 16.600448.3096579.2006max448.3096579.20063.2. Tnh ton ni lc dm ch do hot ti :3.2.1.Tnh h s phn b hot ti theo ln:Nhng kch thc lin quan : hdc= 1,7 m ;khong cch gia cc dm S= 1,9m ;chiu di nhp tnh ton L= 33,2 m ; khong cch t tim dm ti mp trong ca lan can de = 0,95-0,5 = 0,45m3.2.1.1. H s phn b hot ti i vi mmen un:-Mt ln xe cht ti:H s phn b ngang mg c xc nh theo cng thc sau:gm1lan=0,06+ 0,10,4 0,33. .4300 .gsKS SL Lt _ _ _ , , ,Trong : S - khong cch gia cc dm ch; S = 1900 mmL - chiu di nhp tnh ton; L = 33200 mm gK- tham s cng ) . .(2g g g gA e I n K + ,ccEEn Trong :+ Ec l mduyn n hi vt liu dm (MPa)+ ,cEl mduyn n hi vt liu bn mt cu (MPa).Trang

an mn hoc:Thit k Cu BTCT +gI : Mmen qun tnh ca dm (cm4).+eg : khong cch gia trng tm ca dm v bn mt cu.+ gA : din tch dm ch.Mt ct ch T sau khi tnh i nh sau :1138,24350600211,762502006001600 1600Din tch ca mt ct tnh i : Ag = 60.35 + 20.113,824 +21,176.160 = 7764,64 cm2 Xc nh v tr trc trung ha:3 2 132 1F F FQ Q QYxx xc+ ++ +Trong : 11 1.c xy F Q = 21,176.160.159,412 =3388,16.159,412=540113,36 3cm 22 2.c xy F Q = 113,824.20.91,912= 2276,48.91,912= 209235,83 3cm 33 3.c xy F Q = 35.60.17,5 = 2100.17,5 = 36750 3cmQ= 540113,36 + 209235,83 + 36750 = 786099,19 cm3Vy: 2100 48 , 2276 16 , 3388786099,19+ +cY= 101,24 cmMomen qun tnh ca dm:23) 24 , 101 412 , 159 .( 16 , 338812176 , 21 . 160 + gI + 23) 24 , 101 912 , 91 .( 48 , 227612824 , 113 . 20 + +Trang

an mn hoc:Thit k Cu BTCT +23) 24 , 101 5 , 17 .( 21001235 . 60 + = 29188372,03 4cmeg = 170 - 101,4 -21,176/2 = 58,172 cmn = 1( )2. .g gK n I Ae += 1.(31199239,41.104 + 8399,92.102 .58,1722 .102 ) = 5,5487.1011 mm4 1 , 03.

,_

sgt LK=1 , 0311200 . 3320010 . 5487 , 5

,_

= 1,076- Mt ln thit k chu ti:gm = 0,06 +( ) 076 , 1 .332001900.430019003 , 0 4 , 0

,_

,_

= 0,389- Xt hai ln chu ti :gm = 0,075 + 1 . 032 . 0 6 . 0)..( ) .( )2900(sgt LKLS S= 0,075 + 1 . )332001900.( )29001900(2 . 0 6 . 0,076 = 0,5463.2.1.2. H s phn b ngang ca hot ti i vi lc ct:-Xt mt ln chu ti :gv = 0,36+ 7600S=0,36 + 76001900 = 0,61- Hai ln chu ti :gv = 0,2 +2)10700(7600S S= 0,2 + )107001900(760019002 = 0,478 3.2.2. H s phn b ca ti trng ngi i b:Trang

an mn hoc:Thit k Cu BTCT 1900 9500,8421S dng phng php n by,tnh cho c mmen v lc ct.Coi ti trng phn b ngi l lc tp trung ,suy ra:gPL = 0,842.1,5 = 1,263Vy ta c bng tng hp h s phn b ca hot ti v ngi i b i vi dm gia:Mmen un gM0,546Lc ct gV0,61Ngi i b gPL1,2632.2 .Xc nh ni lc :a) T hp m men :* ng nh hng m men mt ct gia nhp:- Xt ( xe 3 trc hoc xe 2 trc ) :17,5 kN72,5 kN9.3KN/m 72,5 kN7,9365,7866,5148,38,39.3KN/m 55 kN55 kN8,08,0 Pi.yi = max( Pi.yi(3 trc); Pi.yi(2 trc)) Pi.yi(3 trc)= (7,936+6,514).72,5 + 17,5.5,786 = 1148,88 Pi.yi(2 trc)= 2.8.55 = 880 Vy : Pi.yi =1148,88KN.m = 33,2.8,3/2 = 137,78m2* Msdht = mgLL(1+IM) Pi.yi+mgLL 9,3 +gPl PL Trang

an mn hoc:Thit k Cu BTCT = 0,546(1+0,25)1148,88 + 0,546. 9,3.137,78 +1,263.4,5.137,78 = 2266,80 KN.m* McdIht =(LL mgLL(1+IM) Pi.yi+ LL mgLL 9,3. +PL.gPl PL )=1.(1,75.0,546.(1+0,25)1148,88+1,75.0,546.9,3.137,78 +1,75.1,263.4,5.137,78)= 3966,91 KN.m* ng nh hngmmen ti mt ct L/4:5,7759.3KN/m6,0756,2255,6792,45455 kN55 kN5,33272,5 kN9.3KN/m 72,5 kN17,5 kN Pi.yi = max( Pi.yi(3 trc); Pi.yi(2 trc)) Pi.yi(3 trc)= (5,679 + 5,332).72,5 + 17,5.2,454 = 841,243 Pi.yi(2 trc)= (5,775+ 6,075).55 = 651,75Vy : Pi.yi =841,243KN.m = 33,2.8,3/2 = 103,335m2* Msdht = mgLL(1+IM) Pi.yi+mgLL 9,3 + gPl PL = 0,546(1+0,25)841,243+ 0,546. 9,3.103,335 +1,263.4,5.103,335= 1686,16KN.m* McdIht =(LL mgLL(1+IM) Pi.yi+ LL mgLL 9,3. + PL.gPl PL )=1.(1,75.0,546.(1+0,25)841,243+1,75.0,546.9,3.103,335 + 1,75.1,263.4,5.103,335 )= 2950,79 KN.m* ng nh hngmmen ti mt ct cch gi 0,8 m:0,763472,5 kN55 kN55 kN9.3KN/m 72,5 kN17,5 kN0,7810,7819.3KN/m0,752 Pi.yi = max( Pi.yi(3 trc); Pi.yi(2 trc)) Pi.yi(3 trc)= 162,5.0,7634 = 124,05 Pi.yi(2 trc)= (0,781+ 0,752).55 = 84,315Vy : Pi.yi =124,05KN.m = 12,965m2Trang

an mn hoc:Thit k Cu BTCT * Msdht = mgLL(1+IM) Pi.yi+mgLL 9,3 + gPl PL = 0,546(1+0,25)124,05+ 0,546. 9,3.12,965 +1,263.4,5.12,965= 224,17KN.m* McdIht =(LL mgLL(1+IM) Pi.yi+ LL mgLL 9,3. + PL.gPl PL )=1.(1,75.0,546.(1+0,25)124,05+1,75.0,546.9,3.12,965 + 1,75.1,263.4,5.12,965 )= 392,32 KN.mBng tng hp mmen do hot ti:Tit din PiyiMCDIMSDL/2 137.78 1148.88 3966.91 2266.80L/4 103.335 841.243 2950.79 1686.160,8m 12.965 124.05 392.32224.17Gi 0 0 0 0b. T hp lc ct:+ ng nh hng ca lc ct ti cc mt ct :L/2 ;3L/8 ;L/4 ; L/8 ;cch gi 2,7m;ti gi : * Lc ct ti mt ct gia nhp :Vxe tai =Pi.yiTi trng ln : Vlan = 9.3. Din tch ng nh hng dng ca lc ctPi Trng lng cc trc xeYi Tung ng nh hng* Xp ti ln ah lc ct mt ct L/2:0,46390,555 kN55 kN0,2410,37050,572,5 kN17,5 kN72,5 kN

Pi.yi = max( Pi.yi(3 trc); Pi.yi(2 trc)) Pi.yi(3 trc)= (0,5+0,3705).72,5 + 17,5.0,241 = 67,329 Pi.yi(2 trc)= (0,5+0,4639).55 = 53,0145Vy : Pi.yi = 67,329 KN + = 33,2.0,5/2.2 = 4,15m2Vsdht = mgLL(1+IM) Pi.yi+mgLL 9,3 + gPl PL.=0,61.(1+0,25).67,329 + 0,61.9,3.4,15 +1,263.4,5.4,15= 98,468KNVcdIht =.(LL mgLL(1+IM) Pi.yi+ LL mgLL 9,3 + PL gPl PL.)=1(1,75.0,61.(1+0,25).67,329+1,75.0,61.9,3.4,15 +1,75.1,263.4,5.4,15)Trang

an mn hoc:Thit k Cu BTCT = 172,319KN* Xp ti ln ah lc ct mt ct L/4:0,750,7140,4910,6210,7555 kN55 kN17,5 kN72,5 kN72,5 kN Pi.yi = max( Pi.yi(3 trc); Pi.yi(2 trc)) Pi.yi(3 trc)= (0,75+0,621).72,5 + 17,5.0,491 = 107,99 Pi.yi(2 trc)= (0,75+0,714).55 = 80,52Vy : Pi.yi = 107,99 KN + = 9,338 m2Vsdht = mgLL(1+IM) Pi.yi+mgLL 9,3 + gPl PL.=0,61.(1+0,25).107,99 + 0,61.9,3.9,338+1,265.4,5.9,338= 188,389kNVcdIht =.(LL mgLL(1+IM) Pi.yi+ LL mgLL 9,3 + PL gPl PL.)=1(1,75.0,61.(1+0,25).107,99 +1,75.0,61.9,3.9,338 + 1,75.1,263.4,5.9,338)= 329,681kN*Xp ti ln ah lc ct mt ct x=0,8m0,7060,8330,96117,5 kN72,5 kN72,5 kN55 kN55 kN0,9610,925 Pi.yi = max( Pi.yi(3 trc); Pi.yi(2 trc)) Pi.yi(3 trc)= (0,961+0,833).72,5 + 17,5.0,706 = 142,42 Pi.yi(2 trc)= (0,961+0,925).55 = 103,73Vy : Pi.yi = 142,42KN + = 15,568 m2Vsdht = mgLL(1+IM) Pi.yi+mgLL 9,3 + gPl PL.=0,61.(1+0,25).142,42+ 0,61.9,3.15,568+ 1,263.4,5.15,568Trang

an mn hoc:Thit k Cu BTCT = 285,393kNVcdIht =.(LL mgLL(1+IM) Pi.yi+ LL mgLL 9,3 +PL gPl PL.)=1(1,75.0,61.(1+0,25).142,42+1,75.0,61.9,3.15,568 + 1,75.1,263.4,5.15,568= 499,438kN* Xp ti ln ah lc ct mt ct tai gi: 0,96410,7410,870155 kN55 kN72,5 kN17,5 kN72,5 kN Pi.yi = max( Pi.yi(3 trc); Pi.yi(2 trc)) Pi.yi(3 trc)= (1+0,87).72,5 + 17,5.0,741 = 178,54 Pi.yi(2 trc)= (1+0,964).55 = 108,02Vy : Pi.yi = 178,54 KN + = 16,6 m2Vsdht = mgLL(1+IM) Pi.yi+mgLL 9,3 + gPl PL.=0,61.(1+0,25).178,54+ 0,61.9,3.16,6+1,263.4,5.16,6= 324,655kNVcdIht =.(LL mgLL(1+IM) Pi.yi+ LL mgLL 9,3 + PL gPl PL.)=1(1,75.0,61.(1+0,25).178,54+1,75.0,61.9,3.16,6+ 1,75.1,263.4,5.16,6= 568,146KnBng tng hp lc ct do hot ti:TTGH Cng I TTGH s dngL/2 L/4 0.8m Gi L/2 L/4 0.8m Gi172,319 329,681 499,438 568,14698,468 188,389 285,393324,655 2.3. T hp ni lc :M=Mtnh ti +Mhot tiV=Vtnh ti +Vhot tiMmen:TTGH s dngL/2 L/4 0,8 m GiMtt(kN.m) 3721.024 2790.903 350.0107 0Mht(kN.m) 2266.80 1686.16 224.32 0M (kN.m) 5987.824 4477.063 574.3307 0TTGH cng IL/2 L/4 0,8 m GiMtt(kN.m) 4807.282 3605.636 452.1874 0Mht(kN.m) 3966.91 2950.79 392.32 0Trang

an mn hoc:Thit k Cu BTCT M(kN.m) 8774.192 6556.426 844.5074 0Lc ct:TTGH s dngL/2 L/4 0,8 m GiVtt(kN) 98.468 188.389 285.393 324.655Vht(kN) 0 224.1278 420.0066 448.3096V (kN) 98.468 412.5168 705.3996 772.9646TTGH cng IL/2 L/4 0,8 m GiVtt(kN) 48.63074 301.7289 542.8217 579.2006Vht(kN) 172,319 329,681 499,438 568,146V(kN) 220.9497 631.4099 1042.26 1147.3474.Chn v b tr cp d ng lc:4.1. Chn s b s lng cp d ng lc + Xc nh theo K cng I:p dng cng thc gn ng : Ta c : Aps h fMpuU. 9 , 0 . . 85 , 0 . =1 : h s sc khng i vi cu kin chu un,chu ko stMu : sc khng tnh ton c h s theo TTGH cng Ifpu :cng chu ko tnh ton ca thp DULh : chiu cao dm ch Aps : din tch ca ct thp chu koTa c : Aps h fMpuU. 9 , 0 . . 85 , 0 . Aps 7 , 1 . 9 , 0 . 10 . 1860 . 85 , 0 . 1192 , 87743=0,003627 m2 = 3627 mm2+ Xc nh theo K ng sut nn gii hn trong b tng theo TTGH s dng:Gii hn ng sut ko trong b tng TTGH s dng l : 0,5. cf '= 0,5. 40 = 3,162 MPa (TCN 5.9.4.2.2) m bo ng sut ko th di khng vt qu gii hn 3,162th tr s nh nht ca lc ko trc Ffc biu din nh sau : fbg = 162 , 3) (. . + Iy MuIy e FAFdd g fgf MPaTrong : + Ag : Din tch ca mt ct tnh i : Ag = 60.35 + 20.113,824 +21,176.160 = 7764,64 cm2 + I l mmen qun tnh ca mt ct quy i , I = 29188372,03 cm4 + Mu l tnh ton trong TTGHSD , Mu = 5987,824 kN.m. + eg khong cch t trng tm dm n trng tm ct thp DUL Trang

an mn hoc:Thit k Cu BTCT gi thit a= 20 cm ( khong cch tm thp DUL n y dm) eg = 101,24 20 = 81,24cm.Thay vo cng thc v gii ta c: Ff 4288,37 kNGi thit US trong b sau cc mt mt l :0,6fpu = 0,6.1860 = 1116 MPaAps puffF6 , 0=111637 , 4288.103 = 3842 mm2 >3726 mm2Xt 2 trng hp trn ta thy TTGH cng I khng nguy him.i vi loi b cp tao 12,7 mi tao c tit din 98,71 mm2S tao cpn = pspsaA = 71 , 983842 = 38,92 tao ,ta chn 42 tao Cc tao c tp hp thnh 6 b, mi b 7 tao 12,7 mm6 b thp, mi b 7 tao, c psA= 6.7.98,71 = 4145mm2Chn ng bc bng thp ng knh ngoi D= 60 mm, A =24D = 2827mm24.2 . B tr cp d ng lc :+ Trong mt ct ngang dm.+ Trong mt ct dc dm :R1=34000R1=40000 B tr ng cong trc cp DUL : ng cong gy khc c vut trn :-chn v tr neo u dm.Trang

an mn hoc:Thit k Cu BTCT -chn v tr im gy ca ng trc, l im B c c l1,2 ( ) 0,15 0, 4 L L l chiu di dm- Ni BC suy ra im A, bit c h- Chn trc T= 2m ri suy ra R theo cng thc : i ih htg arctgl l 22t ttg RRtg Chiu di cung trn : 002360Rd Kt qu c lp thnh bng : s hiu b cpa (mm)a'(mm)h(mm)l(mm)()t(mm)R(mm)D(mm)1 240 250 1210 12070 5,725 2000 40000 39972 100 550 1050 8900 6,728 2000 34000 39923 v 45 v 66.3.Xc nh c trng hnh hc ca tit din dm :Tit din dm ch T c ct thp cng sau khi b tng, tit din hnh thnh cng theo 2 giai on :6.3.1.Xt mt ct gia nhp:a)Giai on 1 ( cha cng ct thp) : Khi cha gim yu: Ag = 8399,92 cm2, Khi gim yu tr i cc l : Din tch l tr i do theo DUL:Aps = 6.28,27 = 169,62 cm2 Din tch tit din tr l : A0 = Ag Aps = 8399,92 -169,62 = 8230,3 cm2Trng tm ca cc ng thp: at at =2 12 2 1 1. .A Aa A a A++=2827 . 6240 . 2827 . 3 100 . 2827 . 3 += 170mm =17 cmTrang

an mn hoc:Thit k Cu BTCT Bng gi tr cc thng s tit din (n v : cm)dd1 tsbe b1bw at170 35 21,176 190 60 20 17Mmen tnh i vi trc i qua y tit din : ps T s s eA adb bdb t d t b b Q + + 2) 1 (2) 5 , 0 .( ). (21W2W W0 062 , 169 . 17235) 20 60 (2170. 20 ) 176 , 21 . 5 , 0 170 .( 176 , 21 ). 20 190 (220 0 + + Q

=884486,91 cm3V tr trc trung ho : yd0-0 =0QA=38 , 7630884486,91= 107,47 cmyt0-0 = d yd =170 - 115,92 = 62,53 cmMmen qun tnh ca tit din khng k l :ps T d dts t s eseA a y d y d b bdb bdyyb t y t b btb b I + + + + + 2 0 0 210 01 W 131W 133W2 0 0W3W0 0) ( ) 5 , 0 .( ) (12). ( )3 3( ) 5 , 0 .( ) (12). ( Thay cc s liu ta c: I0-0=29839049,91 cm4 Sc khng un ti th trn,th di ca tit din gia nhp0 00 00 0ttyIS= 477174,02 cm30 00 00 0ddyIS= 277657,40 cm3 Khong cch t trng tm thp Dul n trng tm dm: Trang

an mn hoc:Thit k Cu BTCT e = 115,92 - 17 = 90,47 cm b)Giai on 2 : ( cng ko ct thp v bm va ): Tit din tng ng:Atd = Ag+ nps.Aps Trong :Ag: din tch tit din nguyn =8399,92cm2nps : h s tnh i t thp DUL sang btng( nps= 16 , 64 , 31975197000 cpsEE)Aps : din tch thp DUL; Aps = 41,45 cm2 Atd = 8399,92 + 6,16.41,45= 8655,25 cm2Mmen tnh i vi trc i qua y tit din : ps T ps s s eI IA a ndb bdb t d t b b Q + + + 2) 1 (2) 5 , 0 .( ). (21W 2W W Thay cc thng s trn ta c : QI-I =891711,09 cm3V tr trc trung ho : ydI-I =tdI IAQ=8655,25891711,09= 103,03 cmytI-I = d yd =170-103,03 = 66,97cmMmen qun tnh ca tit din khng k l :ps TI Id psI IdtsI It s eseI IA a y n d y d b bd b bdyyb t y t b btb b I + + + + + + 2 21 1 W 131 W 133W 2W 3W ) ( ) 5 , 0 .( ) (12 / ). ( )3 3( ) 5 , 0 .( ) (12). ( Thay cc s liu ta c: II-I = 33538082,19cm4 Sc khng un ti th trn,th di ca tit din gia nhpI ItI II ItyIS=500758,48cm3

I IdI II IdyIS= 325532,07 cm3 Khong cch t trng tm thp Dul n trng tm dm: e = 103,03 - 17 = 86,03 cmMt ct gia nhpGiai on I( 0-0)Giai on II( I-I )n vDin tch TD tng ng (Atd ) 8230,3 8655,25 cm2Mmen tnh d/v y TD ( Q ) 884486,91 891711,09 cm3K/c t trc trung ho n y TD (yd) 107,47 103,03 cmTrang

an mn hoc:Thit k Cu BTCT Mmen qun tnh I 29839049,91 33538082,19 cm4Mmen khng un th trn ( St ) 477174,02 500758,48 cm3Mmen khng un th di (Sd) 277657,40 325532,07 cm36.3.2. Xtmt ct gi:a)Giai on 1 ( cha cng ct thp) : Khi cha gim yu: Ag = 12952,88 cm2, Khi gim yu tr i cc l : Din tch l tr i do theo DUL:Aps = 6.28,27 = 169,62 cm2 Din tch tit din tr l : A0 = Ag Aps = 12952,88-169,62 = 12783,26 cm2Trng tm ca cc ng thp: at at=4 3 2 14 4 3 3 1 2 1 1A A A Aa A a A a A a A+ + ++ + +=2827 . 61450 . 2827 1150 . 2827 240 . 2827 . 2 100 . 2827 . 2 + + += 546,7 mm = 54,67cmTa c cc thng s ng vi tit din gi:(n v : cm)dd1 tsbe b1bw at170 0 21,176 190 60 60 54,67Mmen tnh i vi trc i qua y tit din : ps T s s eA adb bdb t d t b b Q + + 2) 1 (2) 5 , 0 .( ). (21W2W W0 0Trang

an mn hoc:Thit k Cu BTCT 62 , 169 . 67 , 54235) 60 60 (2170. 60 ) 176 , 21 . 5 , 0 170 .( 176 , 21 ). 60 190 (220 0 + + Q

=1296568,98 cm3V tr trc trung ho : yd0-0 =0QA=26 , 127831296568,98= 101,43 cmyt0-0 = d yd =170 - 101,43 = 68,57 cmMmen qun tnh ca tit din khng k l :ps T d dts t s eseA a y d y d b bdb bdyyb t y t b btb b I + + + + + 2 0 0 210 01 W 131W 133W2 0 0W3W0 0) ( ) 5 , 0 .( ) (12). ( )3 3( ) 5 , 0 .( ) (12). ( Thay cc s liu ta c: I0-0 = 36305376,57 cm4 Sc khng un ti th trn,th di ca tit din gia nhp0 00 00 0ttyIS= 529442,04 cm30 00 00 0ddyIS= 357945,53 cm3 Khong cch t trng tm thp Dul n trng tm dm: e = 101,43 - 54,67 = 46,76 cm b)Giai on 2 : ( cng ko ct thp v bm va ): Tit din tng ng:Atd = Ag+ nps.Aps Trong :Ag: din tch tit din nguyn =12952,88 cm2nps : h s tnh i t thp DUL sang btng( nps= 16 , 64 , 31975197000 cpsEE)Aps : din tch thp DUL; Aps = 41,45 cm2 Atd = 12952,88+ 6,16.41,45= 13208,21 cm2Mmen tnh i vi trc i qua y tit din : ps T ps s s eI IA a ndb bdb t d t b b Q + + + 2) 1 (2) 5 , 0 .( ). (21W 2W W Thay cc thng s trn ta c : QI-I =1319801,11 cm3V tr trc trung ho : ydI-I =tdI IAQ=13208,211319801,11= 99,92 cmTrang

an mn hoc:Thit k Cu BTCT ytI-I = d yd =170-99,92 = 70,08 cmMmen qun tnh ca tit din khng k l :ps TI Id psI IdtsI It s eseI IA a y n d y d b bd b bdyyb t y t b btb b I + + + + + + 2 21 1 W 131 W 133W 2W 3W ) ( ) 5 , 0 .( ) (12 / ). ( )3 3( ) 5 , 0 .( ) (12). ( Thay cc s liu ta c: II-I = 38026995,53cm4 Sc khng un ti th trn,th di ca tit din gia nhpI ItI II ItyIS=542644,09 cm3

I IdI II IdyIS= 380563,87 cm3 Khong cch t trng tm thp Dul n trng tm dm: e = 99,92 - 54,67 = 45,25 cm Ta c bng kt qu sau : Mt ct gia nhpGiai on I( 0-0)Giai on II( I-I )n vDin tch TD tng ng (Atd ) 12783,26 13208,21 cm2Mmen tnh d/v y TD ( Q ) 1296568,98 1319801,11 cm3K/c t trc trung ho n y TD (yd) 101,43 99,92 cmMmen qun tnh I 36305376,57 38026995,53 cm4Mmen khng un th trn ( St ) 529442,04 542644,09 cm3Mmen khng un th di (Sd) 357945,53 380563,87 cm3IV.4TNH TON MT MT NG SUT :Tng mt mt trong cc cu kin ko sau c quy nhtheo TCN.5.9.5.1

ES PT PF PA P PSR PCR PRf f f f f f f + + + + + Trong : Mt mt tc thi( thi cng ) gm : + Mt mt do thit b neo PAf + Mt mt do ma st PFf + Mt mt do co ngn n hiES Pf Mt mt theo thi gian ( s dng ) gm + Mt mt do co ngt PSRf + Mt mt do t bin ca b tng PCRf + Mt mt do chng ng sut PRf 1.Mt mt ng sut do bin dng ca neo :Trang

an mn hoc:Thit k Cu BTCT Gi thit trt ca neo a gy bin dng trn ct thp cng cao c chiu di L gy mt mt ng sut :fPA =La .EPTrong :a = 3- 10 mm (6mm) EP: M un n hi ca thp cng caoEP =197000 MpaL .Chiu di ca b cp ly gn ng L= 34000mmSuy ra :fpA=197000 .340006 = 34,76 (Mpa)2. Mt mt do nn n hiKhi ko cc b ct thp cng cao khng ng thi cng s gy ra cc mt mt ng sut nh tc dng nn vo b tng dm v c xc nh :fPES =ciPEENN.21 .fcgpTrong :N. S b d ng lc c c trng ging nhau (N=6)EP .M un n hi ca ct thp cng caoEP =197000 MpaEci .M un n hi ca b tng lc truyn lcTa c fc = 40Mpafci Cng lc cng ko ct thpfci = 0,8.fc = 32 MpaEci = 0,85.Ec = 0,85.31975,35 = 27179,05 Mpafegp . Tng ng sut trng tm cc b thp d ng lc do lc ng sut trc sau kch v ti trng ca cu kin cc mt ct c Mmax

.( . ).gi icgpg g gM eF F e efA I I + Fi : lc ko trc khi truyn Fi = 0,7.fpu.Aps =0,7 .1860 .4145. 10-3

= 5396,79 kNe khong cch t trng tm dm n trng tm b ct thp DUL + Tit din gia nhp : Mg = ( DC + DW)vi DC = 23,659 KN/m ;DW= 4,769 KN/m Tit dinL(mm)XK(mm)L-XK(m)YK(m)(2m )MCDI(KN)Msudung(KN)L/2 33200 16600 16600 8.300 137.78 4807.282 3721.024 Mg= 3721,024kNm Trang

an mn hoc:Thit k Cu BTCT Ag = 8399,92 cm2 Ig = 29839049,91 cm4 e = 115,92 - 17 = 90,47 cm1 29839049,947 , 90 . 100 . 024 , 37211 29839049,947 , 90 . 79 , 539692 , 839979 , 53962+ cgpf=-0,78kN/cm2=- 7,8 MPa 8 , 7 .05 , 271791970002 . 6) 1 6 ( PESf = 23,56Mpa+ Tit din gi: Mdc1 = 0Ag = 12952,88 cm2 Ig=36305376,57 m4 e = 101,43 - 54,67 = 46,76 cm

7 36305376,576 , 46 . 79 , 539688 , 1295253962 cgpf = - 0,742 kN/cm2 = - 7,42 MPa 42 , 7 .27179,05197000.2 . 61 6 PESf = 22,41 MPa3.Mt mt ng sut do ma st gia thp d ng lc v thp ng-Khi cng ko ct thp d ng lc mt mt ng sut do ma st vi ng bc c th xc nhnh sau :( ).(1 )KxPF pjf f e + Trong : fpj .ng sut trong b ct thp d ng lc tnh t u kch n tit din tnh tonpjf= 1376,4 MPaK .H s ma st trn on cong v on thng.H s ma st tra bng 5.9.2.2b-1=0,2K= 6,6.10-7 . Tng gia tr tuyt i ca thay i gc nghing b ct thp d ng lc tnh t u kch n im ang xt.e .C s logarit t nhin .Tnh cho mt ct gia nhp :x =12,07/cos 5,7250 +17 12,07 = 17,061 (m)Tnh cho mt ct gix = 0,4 mmVi chiu di x tnh t bng ta cc b cp d ng lc sau khi un cong+Tnh b s 1:mt ct l/2 gi ( rad) 0.1 0.1x (mm) 17061 402PFf 43,19 27,61Trang

an mn hoc:Thit k Cu BTCT Tnh ton tng t cho cc b thp ta c kt qu mt mt ng sut do ma st ca cc b v mt mt trung bnh :Mt ct gi l/2B 1 27,61 42,36B 2 32,19 46,89B 3,4,5,6 0,36 15,36Trung bnh tng b PFf (MPa) 10,21 25,124.Mt mt ng sut do co ngt :Mt mt ng sut b tngtrong cu kin ko sau c xc nh theo cng thc sau :fpsr = 93 - 0,85. HH. m tng i bao quanh kt cu c ly trung bnh hng nm :H=80%fpsr =93-0,85.80 = 25(Mpa)5.Mt mt ng sut do t bin:+Mt mt ng sut do t bin trong b tng l mt mt theo thi gian v ph thuc vo nhiu yu t :Bin php bo dng ,tui th b tng,hm lng N/X +Theo bng 5.9.5.4.3.1 mt mt ng sut do t bin l theo cng thc sau:fpcr =12.fegp - 7.fcdpTrong :fcgp ng sut btng ti trng tm thp DUL lc truyn lc (MPa)cdpf thay i ng sut btong ti trng tm thp d ng lc do tnh ti cht thm DC v lp ph bn mt cu DW

( )1 W0. . 'DC DC cl D clcdptdM M e M efI I MDCTng mmen do tnh ti MDC1 Tng mmen do trng lng bn thn dm MDW Tng mmen do trng lng cc lp ph mt cu. eCL ,eCLkhong cch t trc trung ho n trng tm ct thp DUL Xt ti gia nhp th eCL =115,92 - 17 = 90,47 cm eCL = 103,03 - 17 = 86,03 cm I0=29839049,91 Itd = 33538082,19MDC3721,024 KNm I029839049,91 ecl 90,47 MDC13171,971 KNm Itd 33538082,19 ecl 86,03 Mdw 657,072 K NmThay vo ta c cdpf -2,0732 MPaTrang

an mn hoc:Thit k Cu BTCT 12. 7.pCR cgp cdpf f f = 12.7,8 7(-2,0732) = 108,11 MPa +Ti gi: 0 cdpfDo : 12. 7.pCR cgp cdpf f f = 12 .7,42 = 89,04 MPa6.6. Mt mt ng sut do chng ng sut ct thp DL:PRf = 1 PRf +2 PRf Trong : 1 PRf : Mt mt do chng khi cng 2 PRf : Mt mt do chng sau khi cng a/ Ti thi im truyn lc:i vi tao thp chng thp : log24.(10,55).40pjpjpytfPRfff Trong :t : thi gian tnh theo ngy t khi cng n khi truyn lc, gi nh t = 4 ngy.fpy cng chy quy nh ca b thp, fpy = 1674 MPafpj ng sut ban u trong b thp cui giai on cng, tc l : fpi = 0,74 fpu -pESf -pFf -pAf +Xt gia nhp: fpi = 0,74.1860 23,56 25,12 -34,76 = 1292,96MPa 96 , 1292 ). 55 , 0167496 , 1292(404 . 24 log1 PRf = 14,25 MPa+ Ti gi:fpi = 0,74.1860 22,41 10,21 34,76 = 1309,02 MPa 02 , 1309 ). 55 , 0167402 , 1309(404 . 24 log1 PRf = 15,05 MPab/ Sau khi truyn lc:(TCN5.9.5.4.4c)i vi tao c kh ng sut, ko sau: 20, 3(138 0, 4. 0, 3 0, 2( ))PR pES pF pSR pCRf f f f f + + Ti gia nhp:

)) 11 , 108 25 ( 2 , 0 12 , 25 . 3 , 0 56 , 23 . 4 , 0 138 ( 3 , 02+ PRf = 28,32 MPa+ Ti gi: )) 04 , 89 25 ( 2 , 0 21 , 10 . 3 , 0 41 , 22 . 4 , 0 138 ( 3 , 02+ PRf = 30,94 MPa6.Tng hp cc mt mt ng sut :Trang

an mn hoc:Thit k Cu BTCT mt ct gi l/2PAf 34,76 34,76PFf 10,21 25,12ES Pf 22,41 23,56PSRf 25 25PCRf 89,04 108,111 PRf 15,05 14,252 PRf 30,94 28,32tng mt mt 227,41 259,12IV.5.KIM TRA THEO TRNG THI GII HN CNG 1Trng thi gii hn cng 1 c xem xt m bo cng v s n nh c v cc b v tng th c d phng chu cc t hp ti trng quan trng5.1.Kim ton cng un:Cng thc kim ton trng thi cng 1 MU MnM men qun tnh Mu trng thi gii hn cng 1+Tnh ton kh nng chu un:*ng sut trong b ct thp co dinh kt :fps = fpu.(1-k.pdc)Trong :K= 2(1,04-)pupyff=2(1,04-pupuff . 9 , 0) = 0,28Xt ti mt ct gia nhp :Ta c phng trnh:C =ppups w cf w c c c c y s pu psdfA k b fh b b f f A f A f A. ' . 085 , 0). ( ' . 85 , 0 ' ' .11+ +Fy :Gii hn chy ca ct thp (Mpa)dp:khong cch t th ngoi cng n trng tm ct thp ng sut trc (mm)Trang

A'sApsAs0,85.f'cAps.fpsA's.f'y0,85. 1..f'c(b c-b)As.fyAps.fpsdebds dpd' sbc an mn hoc:Thit k Cu BTCT dp= h-y =1800-200 = 1600 mmKhi ta c :C = 160018606828 28 , 0 200 764 , 0 40 85 , 0208 ) 200 2500 ( 40 764 , 0 85 , 0 0 0 1860 6828x x x x xx x x x x+ + += 36,83 (mm)Vi c min(1,2Mcr ; 1,33Mu) Vy mt ct gia nhp tha mn v hm lng thp ti thiu.8.1.3.Tnh ct ai v kim ton ct TTGH cng I: TCN 5.8.2Cng thc tnh khng ct : .r nV V Trong : : h s sc khng quy nh trong TCN 5.5.4.2, =0,9. Vnsc khng danh nh quy nh trong TCN 5.8.3.3 Sc khng ct danh nh phi c xc ng bng tr s nh hn ca : n c s pV V V V + + 0, 25. '. .n c v v pV f b d V + Trong :'0, 083. . .c c v vV f b d Vs : sc khng ct danh nh ca ct thp thng . do b qua ct thp thng nn Vs = 0Trang

an mn hoc:Thit k Cu BTCT Vc : sc khng danh nh ca b tng Tnh Vc : '0, 083. . .c c v vV f b d bv :b rng dng c hiu , bv= 600mmdv: chiu cao chu ct c hiu, l khong cch t trng tm CT vng chu ko n trng tm CT vng chu nn v ( 0,9de hoc 0,72hdm).Xt ti mt ct ti gi :Ta c phng trnh:C =ppups w cf w c c c c y s pu psdfA k b fh b b f f A f A f A. ' . 085 , 0). ( ' . 85 , 0 ' ' .11+ +Fy :Gii hn chy ca ct thp (Mpa)dp:khong cch t th ngoi cng n trng tm ct thp ng sut trc (mm)dp= d- aT = 1800 701,4 = 1098,6 mmKhi ta c :C = 6 , 109818606828 28 , 0 600 764 , 0 40 85 , 0200 ) 200 2500 ( 40 764 , 0 85 , 0 0 0 1860 6828x x x x xx x x x x+ + += 39,9 (mm)Vi c gii hn ng sut ko 1,38 Mpa+ Gii hn ng sut nn: 0,55fci =-0,55 x 36 = - 19,8 MpaMDC1(KN.m) St0(cm4) FPS(KN A0(cm2) e0(cm)494067 623420,15 9310,86 9359,05 105,78ng sut ca b tng th trnVi FPS=Aps.(0,8fpu-fmatmat) viFmatmat=fPE+fPA+fPESfti=MDC1/St0FPS/A0+FPS.e0/St0-2,075 Mpa tha mnMDC1(KN.m) Sd0 (cm4) FPS(KN A0(cm2) e0(cm)494067 289473,08 9310,86 9359,05 105,78ng sut ca b tng th di:Vi FPS=Aps.(0,8fpu-fmatmat) viFmatmat=fPE+fPA+fPESfdi=+MDC1/St0-FPS/A0-FPS.e0/St0=-26,29 Mpa gia nhp:giai on 2+ Gii hn ng sut ko trong btng:0,5'cf=0,5. 40 =3,162 Mpa+ Gii hn ng sut nn trong btng:0,45fC = -0,45 x 40 = 18 MpaTrang

an mn hoc:Thit k Cu BTCT MDC1 (KN.cm) St0 (KN.cm) Ft KN) A0 (cm2) e0 (cm)494067 623420,15 7405,03 9359,05 105,78MDC2(KN.cm) MDW (KN.cm) Mht (KN.cm) St1 (cm4)24781 115695 353511 353511ng sut ca b tng th trn Vi FPS=Aps.(0,8fpu-fmatmat)fti= -MDC1/St0-FPS/A0+FPS.e0/St0-Mdc2/St1-(Mht+Mdw)/St1-10,57MpaMDC1 (KN.cm) St0 (KN.cm) Ft KN) A0 (cm2) e0 (cm)494067 623420,15 7405,03 9359,05 105,78MDC2(KN.cm) MDW (KN.cm) Mht (KN.cm) Sd (cm4)24781 115695 353511 378954,90ng sut ca b tng th di Vi FPS=Aps.(0,8fpu-fmatmat)fdi=+Mdc1/Sd0-Ft/A0-Ft.ecl/Sd0+MDC2/Sd1+(Mht+Mdw)/Sd1 -4,866Mpa8.2.2. Kim tra vng:- Bin dng do ti trng khai thc qu ln nn h hng mt cu, nt cc b trong bn mt cu gy cm gic khng an ton cho ngi li xe. hn ch iu ny, quy trnh kin ngh: + vng do hot ti ca dm n gin < Lnhp /800. + vng do hot ti ti u dm hng < Lnhp /300.Khi tnh vng do hot ti cn so snh gia : + Mt xe thit k ( c xt IM ) + 25% (mt xe thit k c xt IM v ti trng ln). 8.2.2.1.Tnh vng tc thi do hot ti v xung kch ca dmx =( )2 2 2.6x b LEILPbx L= 35,2 m; xe 3 trc c cc P ln lt l 35kN, 145kN, 145kN., Ti trng ln q=9,3kNm.Vi fc =40MPa, c E= 31975MPa.I = 43742234

cm4EI= 1,3986579 x 1011 kN.cm2 Ti cc v tr t ti trng xe ta c vngx l:Pi(kN) 35 145 145Trang

an mn hoc:Thit k Cu BTCT x(cm) 1330 1760 2190b(cm) 1760 1760 1760x(cm) 0.208675 0.941983 0.850772 vng do ti trng ln :4ln5384qlxEI = 114 210 3986579 , 1 3843520 10 3 , 9 5x xx x=1,3292 cm = 13,292 mm vng tng cng do ti trng xe gy ra: =2,08675+9,41983+8,50772 = 20,0143 mmDo tt c cc ln xe thit k u cht ti v tt c dm ch cng gi thit chu ti trng bng nhau nn h s phn b vng l : DF=LGNN=3/6 = 0,5H s xung kch : (1+IM) = 1,25 vng gia dm do xe ti thit k gy ra, c xt IM l: 1g =0,5 x 1,25 x 20,0143 =12,51 mm vng gia dm do 25%(xe ti thit k +ln)gy ra:2g =0,25 x 0,5 x (1,25 x 20,0143 +13,292) = 4,78 mmTa thy :1 2ax( , )g gm 12,51 mmTa li c 800L=80035200= 44 mm > 1 2ax( , )g gm 12,51 mm Vy dm m bo vng tc thi do hot ti v lc xung kch.Trang