02 Cong Thuc Tinh Toan Btct 2256

7/31/2019 02 Cong Thuc Tinh Toan Btct 2256

1/21

CNG THC TNH TON CC CU KIN

KT CU B TNG CT THP

I- CU KIN CHU NN NG TM.1. S b xc nh din tch tit din:

n

bR

kNF =

k : l s k ti mmen un.T chn s b kch thc tit din b, h hoc D.k = 1,1 - 1,5 :ct trong nh : k = 1,1ct bin : k = 1,3ct gc : k = 1,52. Kim tra iu kin n nh:Tit din vung, ch nht:

mnh : 300

= bl

Tit din khc:

mnh : 120min

0 =r

l

Lin kt hai u khp : lo = l(chiu di thc); nu l ct th lthay bng H.Lin kt hai u ngm : l0 = 0,5lLin kt mt u ngm mt u khp : l0 = 0,7lLin kt mt u ngm kia t do : l0 = 2lCt nh nhiu tng nhiu nhp l0 = 0,7l;Ct nh mt tng l0 ly theo bng .

3. Cc loi bi ton:a- Kim tra kh nng chu lc:N (RnFb+ R aFa)Khi cnh ct < 30cm, c theo phng ng thay Rn bng 0,85RnH s un dc tra bng .Bng : H s

=b

lo 8 10 12 14 16 18 20 22 24 26 28 30

=D

lo 7 8,5 10,5 12 14 15,5 17 19 21 22,5 24 26

1 0,98 0,96 0,93 0,89 0,85 0,81 0,77 0,73 0,68 0,64 0,59

b- Tnh ct thp dc:+ Bit Fb, lo, N, Rn, R a

Fa =

a

n

R

FbRN

'

+ Chn v b tr ct thp+ Kim tra hm lng 0,4% a 3,5%

V d :


2/21

Mt ct c hai u lin kt ngm c chiu cao H = 7m, tit din hnh vung 30x30 cmchu mt lc nn N l 100T. Dng b tng mc 200 thp CII (Ra= 2600kg/cm2). Tnh ct thpchu lc ca ct.

Gii:lo = 0,5 x H = 0,5 x 7 = 3,5m.

b = 30

350=

b

lo

= 11,7; j = 0,97

Fa =2600

30.30.9097,0

100000

= 8,91cm2

Chn 4 18 c Fa = 10,18cm2 > 8,91cm2

Bng : Chiu di tnh ton ca ct nh mt tng

c trng ca nh v ct

l0 khi tnh ct trong mt phng

Ca khungngang

Thng gc vi khung ngangKhi c Khi khng c

Lin ktt trong mt phngca hng ct dc

1 2 3 4 5 6 7

1. Nh c cu chyKhi c k nTi trng cu chy

Phn ct didm cu chy

Lin tcKhng lin tc

1,5H11,2H1

0,8 H10,8 H1

1,2H10,8H1

Phn ct trndm cu chy

Lin tcKhng lin tc

2,0H22,0H2

1,5H21,5H2

2,0H22,0H2

1. Nh c cu chyKhi khng k nti trng cu chy

Phn ct didm cu chyca nh

Mt nhpNhiu nhp

1,5H1,2H

0,8 H10,8 H1

1,2H1,2H

Phn ct trndm cu chy

Lin tcKhng lin tc

2,5H22,0H2

1,5H21,5H2

2,0H21,5H2

2. Nh khng ccu chy

Ct c git cp

Phn ct di

ca nh

Mt nhp

Nhiu nhp

1,5H

1,2H

0,8 H

0,8 H

1,2H

1,2HPhn ct trn 2,5H2 0,8H2 2,5H2Ct c tit dinkhng I

Nh mt nhpNh nhiu nhp

1,5H1,2H

0,8 H0,8 H

1,2H1,2H

Ghi ch:H- Chiu cao ton b ct t mt mng n kt cu miH1 - Chiu cao phn ct di t mt mng n mt vai ct (Hd)H2 - Chiu cao phn ct trn t vai ct n kt cu mi (Ht)


3/21

II- CU KIN CHU NN LCH TM (Tit din ch nht).1. t thp i xnga- Tnh lnh tm ban u eoeo = e01 + eng

lnh tm do ni lc e01 =N

M

lch tm ngu nhin eng =25h (do sai s thi cng) nhng lun lun 2cm

b- Tnh h s un dc:

=thN

N1

1

Lc nn ti hn:

Nth = )(4,620

aabb

dh

JEJEK

S

l+

S l h s ti lnh tmKhi eo < 0,05h ly S = 0,84

Khi 0,05h < eo < 5h ly S =

h

e1,0

11,0

0+

Khi e0 > 5h ly S = 0,122Kdh : l h s k ti tnh cht di hn ca ti trng

Kdh = 1+

2

2h

NM

hNM dhdh

+

+

Nu khng tch ring Mdh , Ndh th ly Kdh = 2Nu Mdh ngc du vi M th Mdh mang du m.Nu Kdh < 1 phi ly Kdk= 1.Mdh; Ndh l mmen v lc dc do ti trng di hn gy ra.M un n hi ca thp Ea = 2,1 x 106 kg/cm2

M men qun tnh ca thp: Ja = tbh0 (0,5h - a)2

Gi thit t = 0,8 1,2% (hm lng thp tng cng)

c- Tnh lch tm tnh ton:

e = eo + 2h

- a

e = eo -2

h+ a

d- Xc nh trng hp lch tm

x =bR

N

n .

Nu x < oho th lnh tm lnNu x oho th lch tm b

Bng : Tr s oCng chu ko tnh ton ca

ct thp (kg/cm3)Tr s o ng vi b tng

200# 250# - 300# 350# - 400# 500# 3000 0,62 0,58 0,55 0,52


4/21

e- Tnh ct thp dc, Trng hp lch tm ln (x < oho)- Nu x > 2a

Fa = Fa =)'ah('R

)x5,0he(N

oa

o

+

- Nu x 2aFa = Fa =

)'ah(R

'Ne

oa

- Kim tra li hm lng min = 0,4% max = 3,5%

% =o

aa

h.b

'FF +100%

V t ( l hm lng tng cng)Nu khc nhiu vi t gi thit th dng tnh li Nth v ( ch nn ly 0,25%), Trng hp lnh tm b (x > oho)

- Tnh x, nu eo 0,2h0 thx= h - 00

0

e4,1h

h5,08,1

+

nu e0 > 0,2h0 thx = 1,8 (eogh - eo) +ohoeogh = 0,4 (1,25h -oho)

Fa = Fa =)'ah('R

)'x5,0h('bxRNe

oa

on

Kim tra li

V d :Tnh ct thp i xng cho mt ct lp ghp c tit din b = 40cm, h = 60cm, b tng

mc 200, ct thp nhm A-II, chiu di tnh ton l0 = 7,8m. Ni lc tnh ton M = 26Tm, N =96T, trong Mdh = 12Tm, Ndh = 61,3T.

Gii:Tra cc s liu: Rn = 90kg/Cm2; Ra = 2800kg/cm2; Eb= 240000 kg/cm2

Ea = 2100000 kg/cm2; 0 =0,62;Ao = 0,428. lch tm eo1 = M/N = 26/96 = 0,27m = 27cm. lch tm ngu nhin ly bng eng =

h/25 = 60/25 = 2,4cm. lch tm eo = 27 + 2,4 = 29,4cm.Gi thit a =a = 4cm; ho = 60 - 4 = 56cm.

604,290 =

h

e= 0,49

Tnh S =286,0

0491,0

11,01,0

1,0

11,0

0

=+

=++

h

e

Kdh= 1 +3,09626

3,03,6112

+

+

= 1,555

Jb =12

6040

12

33 =

bh= 720.000cm4

Gi thit t% = 1%, tnh Ja = tbh0 (0,5h - a)2 = 0,01 x 40 x 56 (30 -40)4 = 15142 cm4Tnh lc dc ti hn


5/21

Nth = 78493910151421,2720240555,1

286,0

720

4,6 62

=

+ kg

=139,1

939,784

961

1

1

1=

=

thN

N

e = 1,139 x 29,4 + 30 -4 = 59,5 cmXc nh chiu cao vng chu nn:

x = cmbR

N

n

6,264090

000.96=

=

x < 0h0 = 0,62 x 36 = 34,7 cm; x> 2a = 8cmXy ra trng hp nn lch tm ln. Tnh Fa

Fa = Fa =)456(2800

)3,13565,59(96000

)'ah(R

)x5,0he(N

0a

0

+

=+

= 11,08 cm2

Kim tra: =5640

08,11

= 0,00495 = 0, 495% > min = 0,2%

t = 1005640

08,1108,11

+

= 0,99%, tc l sai lch so vi gi thit 1% l khng ng k.

Chn ct thp mi pha 3 22 (Fa = 11,4cm2). Ct ai dng 6 (khng di 1/4 x 22 =5,5mm) vi khong cch u = 30cm (nh hn 15 x 2,2 = 33cm).

4. t thp khng i xnga. Tnh lch tm ban u e0 (nh mc 1)b. Tnh h s un dc (nh mc 1)c. Tnh lch tm tnh ton e, e(nh mc 1)d. Xc nh trng hp lch tm.

Nu e0 e0gh = 0,4 (1,25h - 0h0) cu kin chu nn lch tm ln.Nu e0 < eogh cu kin chu nn lch tm be. Tnh ct thp dc) Trng hp lch tm ln

Fa =)'(' 0

2

0

ahR

bhRANe

a

no

Fa ='

a

a

'

a

a

0n0 FR

R

R

NbhR+

) Trng hp lch tm b

Khi e0 0,2h0 tnh xx= h - (1,8 +

0

5,0

h

h- 1,4 0) e0

Khi e0 > 0,2h0x= 1,8 (e0gh - e0) + 0h0

Fa =)'ah(R

)x5,0h(bRNe

0

'

a

0n

Khi e0 0,15h0, Fa t theo cu to. Khi e0 < 0,15h0

Fa =)'ah(

)ax5,0(bR'Ne

0a

n


6/21

a = aRh

e'1

0

0

Kim tra li hm lnga v a phi > 0,002 bh0min < = a +a < max

> 0,25% tnh li Nth v Vi =

2

t+

V d :Thp s liu nh v d 2 nhng yu cu tnh ct thp Fa v F a khng i xng.Gii:Tnh e0 = 1,139 x29,4 cm,tnh e0gh = 0,40 x (1,25 h - 0h0)= 0,40 (1,25 x 60 - 0,62 x 56) = 16,1 cm < e0 = 33,4cm

Nh vy phi tnh ct thp theo trng hp lch tm ln.Fa =

2

2

0

'

a

2

0n0 cm04,6)456(2800

564090428,05,5996000

)'ah(R

bhRANe=

=

Kim tra a% = 1005640

04,6

= 0,267 % > min = 0,2%

Fa = ''

0

a

a

a

a

on FR

R

R

NbhR+

= 04,62800

9600056409062,0+

= 16,39cm2

Chn ct chu nn l 2 20 (Fa = 6,28cm2

) v ct chu ko l 2 25 + 2 22 (Fa =17,42cm2). Chn ct ai nh sau: ng knh 8mm khong cch 30cm.

V d :Cc s liu u ging nh v d 2 nhng ni lc tnh ton l: M = 9,36Tm; N = 260T

trong Mdh = 5Tm; Ndh = 180 TGii:Tnh e0 c th n lch tm ngu nhin:

e0 cm6260

93660

25

1=+

S = 65,01,0

60

61,0

11,0=+

+

Kdh = 1+ 68,13,026036,9

3,01805=

++

S dng nhng kt qu tnh v d trn

Nth = KG66

210218,110151421,2720240

68,1

65,0

720

4,6=

+

=27,1

1218

260

1

1=

e0 = 1,27 x 6 = 7,62


7/21

eogh = 16,1 cm ; h >e0 tc l ri vo trng hp lch tm b.e0 < 0,15h0 = 0,15 x 56 = 8,4cmTnh Fa vi x c tnh nh sau:

x = h - cm8,4862,762,04,156

605,08,1 =

+

e = e0 + ah

2 = 7,62 + 30 - 4 = 33,62

Fa =291,21

)456(2800

)8,485,056(8,48409062,33260000cm=

Fa c tnh nh sau:e = 0,5h - e0 - a = 30 - 7,62 - 4 = 18,38cm;

a =Ra2

0

0 /241956

62,7128001 cmKG

h

e=

=

Fa = 49,9)456(2419

)48,485,0(8,48409038,18260000=

cm2

Famin = 0,002 x 40 x56 = 4,48 cm2< FaChn ct thp Fa l 2 28 + 225 (Fa = 22,14cm2), chn ct thp Fa l 2 25 (Fa =

9,82cm2, ct ai chn 8, bc u = 30cm.


8/21

III- CU KIN CHU KO. (Tit din ch nht)1. Cu kin chu ko ng tm

Fa =aR

N; min = 0,4%

2. Cu kin chu ko lnh tm (tit din ch nht)

eo =N

Mkhi eo 0,5h a: lch tm b

khi e0 > 0,5h a: lch tm lna- Lch tm b

Fa =)'ah('R

Ne

oa

Fa =)'ah(FR

Ne

oaa

'

e = 0,5h eo a

e = 0,5h + eo - a = a + a min = 0,1%.b- Lch tm ln

Fa =)'ah(R

bhRANe

o

'

a

2

0no

e= eo 0,5h + a

Fa =a

aaono

R

FRbhRN ''++

c- Kim tra kh nng chu lc

x =bR

N'FRFRn

a

'

aaa

Khi 2a x < ohoNe Rnbx (ho 0,5x) + RaFa (ho a)Khi x > oho thay x = oho vo cng thc NeKhi x < 2a; Ne RaFa (ho a)d- Tnh theo lc ctiu kin Q koRn bhoko = 0,35 vi BT 400#.Khi Q k1Rkbh0 0,2N, t ai theo cu to nh cu kin chu un.

Khi Q > k1Rkbh0 0,2N, tnh ai m bo iu kin:Q 2,8 d0ok qh)N2,0bhR( k1 = 0,6 i vi thanh chu kok1 = 0,8 i vi bn chu koq tnh nh trong cu kin chu un


9/21

IV- CU KIN CHU UN. (Tit din thng gc)1. Tit din ch nhth0 = h - a

A = 20bhR

M

n

Nu A A0 tnh theo ct nNu A0 < A < 0,5 tng h hoc tnh theo ct kpDng thp c Ra 3000 Kg/cm3 thA0 = 0,428 khi BT- 200#A0 = 0,412 khi BT = 250 300#a. t ct n:- T A tra bng 4-11 c hoc, hoc tnh = 1- A21 ; = 0,5 (1 + A21 ); l t s ca chiu cao vng nn (x) v chiu cao tnh ton ca

tit din (h0)Bi ton:

- Tnh din tch ct thp dc Fa

Fa =Ra

bhRn 0

hoc Fa =0hR

M

a

Kim tra >min ; max =a

n

R

R0

0 = 0,62 khi BT- 200#0 = 0,58 khi BT-250 300#

Bi ton:- Kim tra kh nng chu lc lc khi bit b, h, Fa, b tng v thp

=0bhR

FR

n

aa, t tra bng 4-11 ra A hoc A =(1- 0,5)

[M] = ARnb 20h

V d :Tnh ct thp (Fa) cho dm c tit din ch nht vi kch thc b x h = 25 x 50cm. Dng

mc b tng 200, thp nhm CII, mmen tnh ton l M = 17,6Tm.Gii:

B tng 200 c Rn = 90Kg/cm3;gi thit a = 4cm; h0 =504= 46cm

A =2462590

1780000

= 0,37 < A0 = 0,428

= 1 - 37.021 = 0,49 25mm.


10/21

V d :Mt dm c tit din ch nht vi kch thc b x h = 20 x 45cm, trong tit din vng

ko t 320 nhm AII, mc b tng 200; h0 = 45 - 3 = 42cm.Gii:B tng mc 200 c Rn = 90kG/cm3Thp nhm AII c Rn 2800kG/cm3

3 20 c Fa = 9,41 cm2

=422090

280041,9

= 0,349 < 0 = 0,42

A = 0,349 (1- 0,5 0,349) = 0,288Mgh = 0,288 90.20.422

= 914458 kgcm = 9,14 Tm

b- t ct kpBi ton: Tnh din tch ct thp dc:

Ct chu nn: Fa =)'(

0

'

2

00

ahRbhRAM

a

n

Ct chu ko: Fa = 0'0

a

a

n

a

n FR

R

R

bhR+

Bi ton: Kim tra kh nng chu lc khi bit b, h, Fa, Fa b tng, thp.

=0

''

bhR

FRFR

n

aaaa

Nu > 0 [M] = A0Rnb 'a'

a

2

0 FRh + (h0 a)

Nu 2,73Tm - khng bo m kh nng chu lc, phi tng ct thp v tnh

li.Tng ct ai thnh 10, f = 0,785cm2. Tng ct dc thnh 4 22, Fa = 15,2cm2.Tnh li c m = 0,0000338; x = 15,76cm.

Mt =120C

882C55694016x12

+

Tm c C = 89,7cm; Mt = 3,38Tm.Kim tra Mx = 3 < Mtd = 3,38Tm. Tit din kh nng chu lc.


16/21

MT S CNG THC V BNG TRA THIT K KT CU B TNG CT THP.

SN1. an sn n lm vic hai phng:Mmen nhp trong phng ngn Mi1 = mi1PMmen nhp trong phng di Mi2 = mi2PMmen gi trong phng ngn M i1 = -ki1 PMmen gi trong phng ngn M i2 = -ki2 PCc h s mi1, mi2, ki1, ki2 xem bng 1 - 19 (i l loi bn tu theo lin kt xung quanh).P = (g + p) l1l22. an sn lin tc lm vic hai phng.a- Mmen nhp.Trong phng ngn: Mi1 = m11P + mi1PTrong phng di: Mi2 = m12P + mi2Pm11, m12, mi1, mi2 tra bng 1 - 19

P = 212ll

Pg

+

P = 21.2ll

P

g, p ti trng thng xuyn v tc thi trn 1m2 an sn.b- Mmen gi tip gip:

2'ii MMM

+=

=1iM -ki1P

=2iM -ki1P3. Truyn ti trng t an sn hai phng v dm di dng tng ng.

Khi hai pha c ti trng dng tam gic qt = 185 ql

Khi hai pha c ti trng dng hnh thang qt = k.ql1

Bng : H s k truyn tiL2/l1 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2

K 0,625 0,681 0,725 0,761 0,791 0,815 0,835 0,852 0,867 0,880 0,891

DM4. Tnh Mmen ca dm lin tc theo phng php gn ng

K hiu:S khi dm gi t doS khi dm gi ln dn ln hnS khi dm c cng ctCng thc Mmen: M = kql2

Dm 2 nhp

CT


17/21

MNGMng na. Mng n chu ti ng tm

Din tch mng Fm=cmtbd

tc

HR

N

R cng t nntb= 2T/m3.Fm = A x B;A = (1 1,6)Hom chiu su chn mng Chiu cao lm vic ca mng theo iu kin xuyn thng

Hom = 0,5 ( )

+

+cc

k

bhPR

N5,0

75,0

P=mF

N; hc v bc l kch thc tit din ct.

Chiu cao lm vic theo iu kin chu un

Hom =ncRh

AP

4,0

.

l1 =2

chA ; A l cnh ln ca mng

Thp y mng

Trong phng di Fa A=oma

A

HR9,0

M

Trong phng ngn FaB=oma

B

HR9,0

M

MA = 0,125 pB(A- hc)2MB = 0,125 pA (B - bc)2

b. Mng n chu ti lch tm Kch thc mngA = e0 (2 + 5,2055,1 k )

k =( ) 2

0omtbd

tc

meHR2,1

N

e0 =m

AB

N

Mtc

tc

=; ; m = 1 1,6

Kim tra

=

A

e

BA

N 061.min

max

dR2,1max

dRmin Chiu cao mng

Hom = l1nc

tb

Rh

A

4,0

'

tb = min + (max - min)

+ A

hc25,075,0


18/21

1) Kt cu khng chu tc ng trc tip v thng xuyn ca ma nng:Bng : Khong cch ln nht gia cc khe co gian snhit cho php khng cn

tnh ton (i vi h kt cu khng chu tc ng trc tip v thng xuyn ca manng)

Kt cuKhong cch ln nht gia cc

khe co gin (m)

1. Khung lp ghp(k c trng hp c mi bng kim loi hoc g) 70

2. Kt cu lp ghp bng cc tm c 603. Khung ton khi hoc na lp ghp 604. Kt cu tm c ton khi hoc na lp ghp 50

2) Kt cu chu tc ng trc tip v thng xuyn ca ma nng:i vi kt cu chu tc ng trc tip v thng xuyn ca ma nng nh: Lp mt mi

nh, ban cng, mth ng, khong cch khe co gin nhit m phi ph hp vi tiu chunTCVN 5718 - 1993: Mi v sn b tng ct thp trong cng trnh xy dng - Yu cu k thutchng thm nc. (Bng )

Bng : Khong cch ti a ca khe co gin nhit m, theo hai chiu vung gc(i vi kt cu chu tc ng trc tip v thng xuyn ca ma nng)

Loi kt cu Khong cch ti a (m)- Lp b tng chng thm ca mi khng c lpchng nng.- Tng chn mi bng b tng ct thp

9

- Lp b tng chng thm ca mi c lp chng nng tyu cu k thut, quy nh ti iu 4 ca TCVN 5718 -1993

- Kt cu b tng ct thp khc chu tc ng trc tip cabc x mt tri.

18

Bng : Cp chng nt v gii hn ca b rng khe nt

Loi kt cuCp chng nt v gi tr ca

b rng khe nt gii hn (mm)ng vi loi ct thp c dng

Thpthanh, dy

thpthng

Dy thpcng

caod 4mm

Dy thpcng

caod 3mm

1. Kt cu chu p lc ca cht lng hoc hI Cp 1 Cp 1 Cp 12. Kt cu nm di mc nc ngm3. Kt cu chu trc tip p lc ca vt liu ri Cp 3

0,25Cp 20,10

Cp 20,05

4. Kt cu ngoi tri hoc trong t, trn mc ncngm

Cp 30,30

Cp 20,15

Cp 20,05

5. Kt cu ni c che ph Cp 30,35

Cp 30,15

Cp 20,15


19/21

Ghi ch:(1). B rng khe nt gii hn cho trong bng ng vi tc dng ca ton b ti trng, k c

di hn v ngn hn. i vi kt cu cp 3 khi ch kim tra ring vi ti trng di hn, gii hnb rng khe nt c gim i 0,05mm.

(2). nhng vng chu nh hng ca nc mn, gim b rng khe nt gii hn 0,1mm

i vi cp 3, gim 0,5mm i vi cp 2. Nu sau khi gim m b rng khe nt gii hn bngkhng th nng kt cu ln thnh cp 1.(3). i vi nhng cng trnh tm c nin hn s dng di 20 nm cho php tng b

rng khe nt gii hn ln 0,5mm.Bng : Tr s gii hn ca bin dng fgh

Loi cu kin Gii hn vng1. Dm cu trc vIa/ Cu trc quay tay

b/ Cu trc chy in(1/500)L(1/600)L

2. Sn c trn phng, cu kin ca mi v tm tng treo (khi tnh tmtng ngoi mt phng), nhp L:

a/ L < 6mb/ 6 L 7,5mc/ L > 7,5m

(1/200)L3cm

(1/250)L3. Sn vi trn c sn v cu thang, nhp L:a/ L < 5m

b/ 5 L 10mc/ L > 10m

(1/200)L2,5cm

(1/400)L

Ghi ch:(1). L l nhp tnh ton ca dm hoc bn k ln 2 gi. i vi cc cng xn, dng L = 2

L1 vi L1 l vn ca cng xn.(2). Khi thit k kt cu c vng trc th lc kim tra v vng cho php tr i vng nu khng c nhng hn ch g c bit.

(3). i vi cc cu kin khc khng nu trong bng th gii hn vng c quynh tu theo tnh cht v nhim v ca chng nhng gii hn khng c ln qu 1/150nhp hoc 1/75 vn ca cng xn.

(4). Khi quy nh vng gii hn khng phi do yu cu v cng ngh sn xut v cuto m ch do yu cu v thm m th tnh ton f ch ly cc ti trng tc dng di hn.

Bng : Chn kch thc tit din (b h.cm) ca dm b tng ct thpTI

trngt snkg/m

Nhp dm (m)

3 3,5 4 4,5 5 5,5 6 6,5 7

1000 10 25 10 30 15 30 15 35 20 35 20 40 20 40 20 45 20 451200 10 30 10 30 15 30 15 35 20 35 20 40 20 45 20 45 20 451400 10 30 15 30 15 35 15 35 20 40 20 40 20 45 20 45 20 501600 15 30 15 30 15 35 15 40 20 40 20 45 20 45 20 50 20 501800 15 30 15 35 20 35 20 40 20 40 20 45 20 45 20 50 20 502000 15 30 15 35 20 35 20 40 20 45 20 45 20 45 20 50 20 552400 15 35 20 35 20 40 20 40 20 45 20 45 20 50 20 50 20 55

2800 15 35 20 35 20 40 20 45 20 45 20 50 20 50 20 50 20 553200 20 35 20 40 20 40 20 45 20 50 20 50 20 50 20 55 20 603600 20 35 20 40 20 40 20 45 20 50 20 50 20 55 20 55 20 60


20/21

Bng : Chn chiu dy an sn loi lm vic mt phng (ld : ln > 2) (cm)Hot titrn sn(kG/m2)

Chiu di phng ngn ln (m)

1,6 1,8 2,0 2,2 2,4 2,6 2,8 3,0

200250300350400450500600700800900

1000

Bng : Tr s A, ,A A

0,01 0,995 0,010 0,32 0,840 0,2690,02 0,990 0,020 0,33 0,835 0,2750,03 0,985 0,030 0,34 0,830 0,2820,04 0,980 0,039 0,35 0,825 0,2890,05 0,975 0,048 0,36 0,820 0,2950,06 0,970 0,058 0,37 0,815 0301

0,07 0,965 0,068 0,38 0,810 0,3090,08 0,960 0,077 0,39 0,805 0,3140,09 0,955 0,085 0,40 0,800 0,3200,10 0,950 0,095 0,41 0,795 0,3260,11 0,945 0,104 0,42 0,790 0,3320,12 0,940 0,013 0,43 0,785 0,3370,13 0,935 0,122 0,44 0,780 0,3430,14 0,930 0,130 0,45 0,775 0,3490,15 0,925 0,139 0,46 0,770 0,3540,16 0,920 0,147 0,47 0,65 0,3590,17 0,915 0,156 0,48 0,760 0,3650,18 0,910 0,164 0,49 0,755 0,3700,19 0,905 0,172 0,50 0,750 0,3750,20 0,900 0,180 0,51 0,745 0,3800,21 0,895 0,188 0,52 0,740 0,3850,22 0,890 0,196 0,53 0,735 0,3900,23 0,885 0,204 0,54 0,730 0,3940,24 0,880 0,211 0,55 0,725 0,3990,25 0,875 0,219 0,56 0,720 0,4030,26 0,870 0,226 0,57 0,715 0,4080,27 0,865 0,235 0,58 0,710 0,412

0,28 0,860 0,241 0,59 0,705 0,4160,29 0,855 0,248 0,60 0,700 0,4200,30 0,850 0,255 0,61 0,695 0,424

7-8

6-7

8-9

9-10

10-11


21/21

0,31 0,845 0,262 0,62 0,690 0,428

Bng : Din tch ct thp trn (cm2) khi bit khong cch v ng knh thp(Tnh cho 1 m chiu rng an)

Khongcch thp

(cm)

ng knh (mm)6 6/8 8 8/10 10 12 14 16

7 4,04 5,60 7,19 9,20 11,21 16,16 21,99 27,737,5 3,77 5,20 6,71 8,60 1,470 15,08 20,52 26,818 3,54 4,90 6,29 8,10 9,81 14,14 19,24 25,149 3,14 4,40 5,59 7,20 8,72 12,57 17,10 22,3410 2,83 3,90 5,03 6,40 7,85 11,31 15,39 20,1011 2,57 3,60 4,57 5,86 7,14 10,28 13,99 18,2812 2,36 3,30 4,19 5,40 6,54 9,42 12,83 16,76

12,5 2,26 3,10 4,02 5,20 6,28 9,05 12,32 16,0813 2,18 3,00 3,87 5,00 6,04 8,70 11,84 15,47

14 2,02 2,80 3,59 4,60 5,61 8,08 11,00 14,3615 1,89 2,60 3,35 4,30 5,23 7,54 10,26 13,4116 1,77 2,50 3,14 4,10 4,91 7,07 9,62 12,5717 1,66 2,30 2,46 3,80 4,62 6,65 9,05 11,8318 1,57 2,20 2,79 3,60 4,36 6,28 8,55 11,1719 1,49 2,10 2,65 3,40 4,13 5,95 8,10 10,0820 1,41 2,00 2,51 3,20 3,39 5,65 7,69 10,05

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02 Cong Thuc Tinh Toan Btct 2256