Chng m au
AI CNG VE KET CAU THEP
Khai niem Ket cau thep (KCT) dung e ch nhng ket cau chu lc cua cac cong trnh xay dng lam bang
thep hoac kim loai khac noi chung.
0.1. U VA KHUYET IEM CUA KET CAU THEP
0.1.1. u iem
Kha nang chu lc ln, o tin cay cao; Kha nang chu lc ln: vat lieu thep co cng o ln;
o tin cay cao: cau truc thuan nhat cua vat lieu, s lam viec an hoi va deo cua vat lieu gan sat
nhat vi cac gia thiet tnh toan.
Trong lng nhe; 1
Ket cau thep nhe nhat trong so cac ket cau chu lc nh:
BTCT, gach a, go.
(0.1)
Trong o:
: trong lng rieng thep;
f: cng o tnh toan thep;
oi vi thep: c=3.7*10-4 1/m
oi vi be tong: c=2.4*10-3 1/m
oi vi go: c=5.4*10-4 1/m
Tnh cong nghiep hoa cao;
Tnh c ong trong van chuyen, lap rap;
Tnh kn.
2
cf
0.1.2. Nhc iem
B an mon;
Chu la kem.
Thep khong chay nhng nhiet o t=(500600)0C, thep
chuyen sang deo, mat kha nang chu lc, ket cau b sup
o de dang.
0.2. PHAM VI NG DUNG
+ Nha cong nghiep.
+ Nha nhp ln.
+ Khung nha nhieu tang.
+ Cau ng bo - ng sat.
+ Ket cau thap cao.
+ Ket cau ban.
+ Ket cau di ong.
3
0.3. YEU CAU OI VI KET CAU THEP
Yeu cau ve s dung.
Thoa man cac yeu cau ve chu lc e ra do ieu kien s dung;
am bao o ben lau thch ang cua cong trnh;
ep, ac biet quan trong oi vi nha cong cong co ket cau lo ra ngoai;
Yeu cau ve kinh te.
Tiet kiem vat lieu;
Tnh cong nghe khi che tao;
Lap rap nhanh;
ien hnh hoa KCT;
4
Chng 1
VAT LIEU VA S LAM VIEC CUA KET CAU THEP
1.1. THEP XAY DNG
1.1.1. Phan Loai Thep Xay Dng
+ Thep va gang la hp kim en cua Fe va C, ngoai ra
con cac chat khac co t le khong ang ke nh: O, P, Si,
v.v
+ Qua trnh luyen gang va thep
T quang sat (Fe2O
3 , Fe
3O
4 ) luyen trong lo cao
gang (hp kim Fe, C vi lng C chiem tren 1,7%)
qua lo luyen thep e kh bt C trong gang thep.
5
a. Theo thanh phan hoa hoc cua thep
+ Thep cacbon, vi lng C
+ Thep tnh: trong qua trnh nguoi khong co hi boc ra
nh thep soi, do a c them nhng chat kh oxy nh
Si, Al, Mn, v.v Loai thep nay chu lc ong tot, kho b pha hoai gion.
+ Thep na tnh: la trung gian gia thep tnh va thep soi,
trong o oxy khong c kh hoan toan.
1.1.2. Cau Truc Va Thanh Phan Hoa Hoc Cua Thep
a. Cau truc cua thep
Thep co cau truc tinh the, thep gom co hai to chc
chnh:
+ Ferit (la sat nguyen chat), chiem 99% the tch, mau
sang, co tnh mem va deo.
+ Xementit, la hp chat Fe3C, rat cng va gion.
7
b. Thanh phan hoa hoc cua thep
Thep cacbon, ngoai hai thanh phan chnh la sat va
cacbon, con co cac thanh phan phu khac nh Mn, Si, P,
S, v.v
+ Mn, lam tang cng o va o dai cua thep. Neu ham
lng Mn vt qua 1.5%, thep tr nen gion.
+ Si, lam tang cng o cua thep nhng lam giam tnh
chong g, tnh de han. Ham lng Si khong qua 0.3%
oi vi thep cacbon thap.
+ P, lam giam tnh deo va o dai va cham cua thep,
ong thi lam thep tr nen gion nguoi (gion nhiet o
thap).
+ S, lam thep tr nen gion nong (gion nhiet o cao),
nen de b nt khi han va ren.
8
1.2. QUY CACH THEP CAN DUNG TRONG XAY
DNG
Ket cau xay dng c che tao t cac thep tam, thep
hnh co nhieu loai kch thc khac nhau. Thep can nong
bao gom cac loai thep sau:
+ Thep hnh;
+ Thep tam;
+ Thep hnh dap, can nguoi;
+ Thep pho thong;
9
10
x x
y
y
x 0
0 x y
0
y 0
b b
z 0
d
B
x y
y
b
0
y d
u
x 0
Hnh 1.2.a : thep goc eu canh Hnh 1.2.b : thep goc khong eu canh
y
Hnh 1.2.c : thep ch I
y
x x
b
h
d
t
y
x
y
z 0
b
h
d
Hnh 1.2.d : thep ch
d
Hnh 1.2.e : thep ong
D
1.2.1. Thep Hnh
a. Thep goc
Co 2 loai: eu canh va khong eu canh, vi t le hai canh khoang 1:1.5 en 1:2.
Thep goc eu canh gom 50 loai tiet dien t nho nhat la L20x20x3 en ln nhat la L250x250x35.
Thep goc khong eu canh gom 72 loai tiet dien t nho nhat la L30x20x3 en ln nhat la L200x150x25.
ac iem: canh co hai mep song song vi nhau, tien cho viec cau tao lien ket, chieu dai thanh thep goc t
413m.
Pham vi s dung: thanh cua dan, thanh cua he giang, lien ket vi cac loai thep khac e tao nen cac cau kien
to hp nh ghep vi cac ban thep thanh tiet dien cot
rong, tiet dien dam ch I,v.v
11
b. Thep ch I
Gom co 23 loai tiet dien, chieu cao t 100600mm
K hieu I30 (cao 30cm), I30a (cao 30cm, canh rong va day hn I30), chieu dai t 413m.
Co o cng theo phng truc x rat ln so vi phng truc y.
Pham vi s dung: lam dam chu uon, hoac cot (nen tang o cng oi vi truc y bang cach m rong them canh hoac ghep
hai thep I lai).
c. Thep ch
Gom co 22 loai tiet dien, t 5 en 40. Ky hieu 22 (cao 22cm), chieu dai t 413m.
Thep ch co mot mat bung phang va cac canh vn rong nen tien lien ket vi cac cau kien khac.
Pham vi s dung: lam dam chu uon, ac biet hay dung lam xa go mai chu uon xien hoac c ghep thanh thanh tiet dien
oi xng, dung lam cot, lam thanh dan cauv.v.
12
d. Thep ong
Co hai loai: khong co ng han doc va co ng han doc.
Thep ong co tiet dien oi xng, vat lieu nam xa truc trung hoa nen o cng tang, chu lc khoe, ngoai ra
chong g tot.
Pham vi s dung: dung lam cac thanh dan, ket cau cot thap cao.
1.2.2. Thep Tam
c dung rong rai v tnh chat van nang, co the tao ra
cac loai tiet dien co hnh dang va kch thc bat ky. Co
cac loai sau:
+ Thep tam pho thong, co be day =460mm, rong
B=1601050mm, dai L=612m. Thep tam pho thong co
bon canh phang nen s dung rat thuan tien.
13
+ Thep tam day, co =4160mm, B=6003000mm, L=48m. Thep tam day co be rong ln nen hay dung
cho ket cau ban.
+ Thep tam mong, co =0.24mm, B=6001400mm, L=1.24m. Thep tam mong dung e tao cac thanh
thanh mong bang cach dap, can nguoi, dung lp
mai,v.v.
1.2.3. Thep Hnh Dap, Can Nguoi
ay la loai thep hnh mi so vi thep can. T cac thep
tam mong, day =216mm, mang dap, can nguoi ma thanh.
+ Co cac loai tiet dien: thep goc eu canh-khong eu
canh, thep ch , thep tiet dien hop, v.v.
+ Thep hnh dap, uon nguoi co thanh mong, nen nhe
hn nhieu so vi thep can nong.
14
+ Pham vi s dung: dung chu yeu cho cac loai ket cau
thep nhe, cho nhng cau kien chu lc nho nhng can
co o cng ln.
+ Khuyet iem: Co s cng nguoi nhng goc b uon,
chong g kem. Cha co tieu chuan cho loai thep nay,
can tham khao them cac tieu chuan cua Nga, Anh,
Eurocode, v.v.
1.2.4. Thep Pho Thong
+ Co ng knh t 680mm.
+ Co 2 loai: trn va co gan.
+ Pham vi s dung: thanh cang cua vom, boulone neo,
boulone chu lc. Thng dung trong ket cau be tong
cot thep.
15
1.3. S LAM VIEC CUA THEP CHU TAI
TRONG
1.3.1. S Lam Viec Chu Keo Cua Thep
a. Bieu o ng suat bien dang khi keo (thep C thap)
16
tl
c
21
24
38
40
0
0 4 22 %16
b
B
C D
E
Hnh 1. Bieu o quan he gia ng suat va bien dangHnh 1.3.1. Bieu o ng suat bien dang khi keo
kN/cm2
ng suat =P/A, kN/cm2;
Bien dang t oi: =l/l, %;
Trong o:
P: tai trong;
A: tiet dien ban au cua mau;
L: chieu dai ban au cua mau;
l: o dan dai cua mau ng vi tng cap
tai trong;
+ oan t 0 en B: (, ) co quan he tuyen
tnh, =E, giai oan t le, tl (
h);
E: module an hoi;
Vi thep cacbon thong thng, E=2.06e6 daN/cm2;
17
l
l+
l
l
Hnh 1.3.2. Chieu dai mau trc
va sau khi keo
+ oan t B en C: (, ) co quan he phi tuyen, thep
khong con lam viec an hoi na, giai oan an hoideo;
+ oan t C en D: hau nh la oan nam ngang, giai
oan chay deo. tang, =const, gii han chay c;
+ oan t D en E: thep khong chay na, giai oan
cung co, gii han ben b ,
0=2025%;
b. Cac ac trng c hoc chu yeu cua thep
+ Gii han t le, tl h ;
+ Gii han chay c, o la ng suat ln nhat co the co
trong vat lieu, khong c phep vt qua (=0.2%);
+ Gii han ben b : con goi la cng o tc thi cua
thep, xac nh mot vung an toan d tr gia trang thai
lam viec va trang thai pha hoai;
18
+ Bien dang khi t 0
: ac trng cho o deo, o dai
cua thep;
+ Module an hoi E;
Tuy thuoc vao tr so cua , co the ap dung cac l thuyet tnh toan sau:
Khi tl: dung l thuyet an hoi, vi E=const;
Khi tl
* S lam viec chu nen cua thep khong khac s lam viec
chu keo, cung E, tl,
h,
c. Ch co trong giai oan cung
co th khong xac nh c b. Do o, trong giai oan
lam viec an hoi va an hoi deo, cac ac trng c hoc
tnh toan cua thep chu keo chu nen lay giong nhau.
1.3.2. S Pha Hoai Gion Cua Thep
S pha hoai gion la s pha hoai bien dang nho, kem
theo vet nt, vat lieu lam viec trong giai oan an hoi.
a. Hien tng cng nguoi
o la hien tng tang tnh gion cua thep sau khi b bien
dang deo nhiet o thng. Thep sau khi b bien dang
deo th tr nen cng hn, gii han an hoi cao hn va
bien dang khi pha hoai nho hn.
20
+ S cng nguoi xay ra khi gia cong nguoi cac cau kien:
uon nguoi, cat bang may cat, ot lo, v.v
b. Thep chu trang thai ng suat phc tap - s tap trung
ng suat
Trng hp hay gap cua trang thai ng suat phc tap la
trng hp ng suat cuc bo, gay bi cac bien oi ot
ngot cua hnh dang cau kien.
+ Khi cau kien co lo khuyet, ranh cat th ng lc (quy
ao cac ng suat chnh) se khong con song song eu
an, ma uon cong xung quanh cho cat. ng lc tap
trung chng to ng suat cho o tang cao va tai o ton tai
ng suat theo hai phng x va
y lam thep tr nen gion.
+ Ket cau chu tai trong ong lc th s tap trung ng
suat la nguy hiem v lam cho thep de b pha hoai gion.
21
22
Hnh 1.3.3. Cac quy ao ng suat khi keo
1.3.3. Thep Chu Tai Trong Lap
+ Khi thep chu tai trong lap, no co the b pha hoai ng
suat nho hn gii han ben o la s moi cua thep.
+ S pha hoai ve moi mang tnh chat pha hoai gion,
thng xay ra ot ngot va kem theo vet nt.
+ ng suat pha hoai moi cua thep goi la cng o moi ff,
ff phu thuoc vao so chu ky lap, tnh chat thay oi cua tai
trong va mc o tap trung ng suat. Gia tr cua ff, tra
bang.
1.3.4. S hoa gia cua thep
+ Theo thi gian, tnh chat cua thep thay oi dan: c,
b
tang len, o gian va o dai va ap giam i, thep tr nen
gion hn.
23
+ Nguyen nhan: trong cac tinh the ferit van con cac chat
C, N hoa tan. Cac chat nay dan dan tach ra va tao nen
cac lp cng gia cac hat ferit.
1.3.5. Anh hng cua nhiet o
+ nhiet o t=2003000C: tnh chat cua thep thay oi
rat t;
+ nhiet o t=3003300C: thep tr nen gion hn;
+ nhiet o t>3300C:
c,
b giam rat nhanh;
+ nhiet o t=6006500C:
c=0;
+ nhiet o t>15000C: thep bat au chuyen sang the
long;
+ nhiet o t
1.4. TNH TOAN CAU KIEN
1.4.1. Cau Kien Chu Keo ung Tam
Cau kien chu keo c kiem tra ben theo cong thc:
Trong o:
+ N: noi lc doc do tai trong tnh toan;
+ An: dien tch thc cau kien (a tr i cac giam yeu);
+ c: he so ieu kien lam viec, tra bang;
+ f: cng o tnh toan cua thp ly theo gii hn chy;
+ ft: cng o tnh toan cua thp ly theo sc bn ko t;
25
ben han gii theo
chay han gii theo
-
-
u
ct
c
nf
f
A
N
(1.1)
(1.2)
+ u =1.3, he so an toan;
1.4.2. Cau Kien Chu Uon
a. Tnh cau kien chu uon trong giai oan an hoi
Trong o:
+ M, V: moment uon va lc cat do tai trong tnh toan;
+ Wn: moment chong uon cua tiet dien thc;
+ I: moment quan tnh cua tiet dien nguyen;
+ S: moment tnh (nguyen) cua phan tiet dien trt oi
vi truc trung hoa;
26
c
n
fW
M
cvfIt
VS
(1.3)
(1.4)
+ t: be day thanh cau kien;
b.Tnh cau kien chu uon co bien dang deo
Trong o:
+ Wd
= 2S: moment chong uon deo;
Tiet dien ch nhat: Wd=1.5W;
Tiet dien ch I: Wd=1.12W;
+ : ng suat tiep;
27
c
d
fW
M
ctf 1513 22 ,
(1.5)
(1.6)
c.Tnh toan cau kien theo TTGH th hai
: o vong;
: o vong gii han cho phep, tra bang;
1.4.3. Cau Kien Nen ung Tam
a.Tnh ve ben
b.Tnh ve on nh
: he so uon doc, tra bang;
28
(1.7)
c
n
fA
N (1.8)
cfA
N (1.9)
1.4.4. Cau Kien Chu Keo Lech Tam Va Nen Lech Tam
a.Tnh cau kien chu keo lech tam va nen lech tam
+ Kiem tra o ben trong giai oan lam viec an hoi theo
cong thc:
+ Khi xet en bien dang deo:
He so c tuy thuoc vao dang tiet dien, tra bang;
29
c
n
fM
A
N
nW(1.10)
1
2/3
cncn fcW
M
fA
N
(1.11)
b.Tnh ve on nh cua thanh nen lech tam
+ Kiem tra on nh trong mat phang uon:
e: he so giam cng o tnh toan;
cr
e: ng suat ti han;
+ Kiem tra on nh ngoai mat phang uon:
y: he so uon doc khi nen ung tam;
30
ce fA
N (1.12)
f
e
cre
(1.13)
c
y
fAc
N
(1.14)
Chng 2
LIEN KET
Hien nay, trong ket cau thep dung hai phng phap lien
ket chnh la:
+ Lien ket han;
+ Lien ket boulone;
2.1. LIEN KET HAN
La s lien ket gia cac phan t cua cac kim loai b nong
chay (kim loai can han va que han).
2.1.1. u iem
+ Giam cong che tao va khoi lng kim loai;
+ Hnh thc cau tao lien ket n gian;
+ Ben, co tnh kn cao;
31
2.1.2. Nhc iem
+ Gay bien hnh han va ng suat han trong lien ket lam
tang tnh gion cua vat lieu;
+ Kho kiem tra chat lng ng han;
2.1.3. Cac Phng Phap Han Trong Ket Cau Thep
a. Han ho quang ien bang tay
32
Hnh 2.1. S o han ho quang ien bang tay
Tay cam
Nguon
ien
Day dan
Que han
Ho quang
Thep c
ban
+ Nguyen ly
Di tac dung cua dong ien ho quang ien lam
nong chay mep cua thep c ban va que han. Hai kim
loai long hoa lan vi nhau, nguoi lai tao thanh ng
han.
+ Que han (TCVN 3223:1994)
Dung que han (chieu dai L=200450mm) loi kim loai
(ng knh D=1.66mm) co thuoc boc day t=11.5mm
(thuoc han, gom khoang 80% la CaCO3).
b. Han ho quang ien t ong
+ Nguyen ly
Thuoc han c rai trc thanh lp day tren ranh han.
Day han c t ong nha dan theo toc o di chuyen
eu cua may han.
33
+ u iem
Toc o han nhanh (gap 510 lan han tay);
Chat lng ng han tot;
+ Nhc iem
Ch han c cac ng han nam thang hoac tron;
Khong han c cac ng han ng, ngc;
34
Hnh 2.2. S o han ho quang ien t
ong
Ong hut thuoc han
Day han tran
May han
Pheu rai thuoc
han
Ho quang
chm
Thuoc han
c. Cac yeu cau chnh khi han va phng phap kiem tra
chat lng ng han
+ Cac yeu cau chnh khi han
Lam sach g tren mat ranh han;
Cng o dong ien phai thch hp;
Gia cong mep ban thep ung qui nh;
Chon que han phu hp;
Phong nga bien hnh han;
+ Cac phng phap kiem tra chat lng ng han
Kiem tra bang mat;
Dung cac phng phap vat ly nh sieu am, ien t, v.v
35
2.1.4. Cac Loai ng Han Va Cng o Tnh Toan
a. ng han oi au
+ Cau tao
La ng han lien ket trc tiep hai cau kien cung nam trong mot mat phang;
ng han oi au co the thang goc hoac xien goc vi truc cua cau kien;
36
Hnh 2.3. ng han oi au
+ u va nhc iem
u iem
Truyen lc tot;
Lam viec giong nh thanh c ban;
Nhc iem
Gia cong mep ban thep (khi ban thep day, t = > 8mm);
+ Cng o tnh toan cua ng han oi au
Khi chu nen (khong phu thuoc vao phng phap kiem tra chat lng ng han)
fwc
= f (f, cng o tnh toan cua thep c ban);
Thep CCT34, fwc
= 2100daN/cm2;
C, nhom C;
CT, cacbon thng;
fu = 34kN/cm
2, cng o tieu chuan cua thep theo sc
ben keo t;
37
Khi chu keo
- Dung phng phap vat ly kiem tra chat lng
ng han
fwt
= f, thep CCT34, fwt
= 2100daN/cm2;
- Dung cac phng phap khac
fwt
= 0.85f, thep CCT34, fwt
= 1785daN/cm2;
Khi chu cat
fwv
= fv, thep CCT34, f
wv = 1200daN/cm
2;
fv, cng o tnh toan khi chu cat cua thep c ban;
38
b. ng han goc
+ Cau tao
La ng han nam goc vuong tao bi hai cau kien can han;
Tiet dien ng han la mot tam giac vuong can, canh cua tam giac goi la chieu cao ng han h
f;
39
Hnh 2.3. ng han goc
+ Chieu cao ng han
hfmax
1.2tmin
tmin
: chieu day nho nhat trong so cac ban thep c lien
ket;
40
Phng
phap
han
hfmin
khi chieu day cua ban thep tmax
, mm
46 610 1116 1722 2332 3340 4180
Tay 4 5 6 7 8 9 10
T
ong 3 4 5 6 7 8 9
Bang 2.1. Chieu cao nho nhat cua ng han goc
hfmin
, mm
Tuy theo v tr cua ng han so vi phng cua lc tac
dung ma chia ra:
ng han goc canh la ng han goc song song vi phng cua lc tac dung;
ng han goc au la ng han goc vuong goc vi phng cua lc tac dung;
41
ng han goc canh ng han goc
au
Hnh 2.4. Cac loai ng han goc
N
N
N N
+ S lam viec cua ng han goc canh
ng suat phan bo khong eu theo chieu rong, chieu dai ban thep;
Hai mut cua ng han chu max
;
42
Hnh 2.5. S phan bo ng suat trong ng han goc canh
Chu ong thi ca ng suat cat va uon. Trong tnh toan coi nh chung ch chu cat quy c va pha hoai theo hai
dang sau:
- mot trong hai tiet dien doc theo kim loai ng han
(tiet dien 1);
- theo bien nong chay cua thep c ban (tiet dien 2);
43
Hnh 2.6. Dang pha hoai va tiet dien lam viec cua ng
han goc canh
dang pha hoai cac tiet dien lam viec
+ S lam viec cua ng han goc au
Truyen lc eu theo be rong cua lien ket;
Chu ong thi ca ng suat cat, keo va uon. Trong tnh toan coi nh chung ch chu cat quy c va b pha hoai
theo tiet dien 1 va 2 giong ng han goc canh;
+ Cng o tnh toan cua ng han goc
ng vi tiet dien 1: cng o tnh toan chu cat cua thep ng han f
wf;
44
Loai que han theo TCVN 3223 : 1994 fwf
(daN/cm2)
N42, N42 - 6B 1800
N46, N46 - 6B 2000
N50, N50 - 6B 2150
Bang 2.2. Cng o tnh toan chu cat cua thep
ng han fwf
ng vi tiet dien 2: cng o tnh toan chu cat cua thep c ban f
ws = 0.45f
u;
fu: cng o tieu chuan cua thep theo sc ben keo t;
c. Cac cach phan loai ng han khac
+ Theo cong dung
ng han chu lc (e truyen lc);
ng han khong chu lc (e cau tao);
+ Theo v tr
ng han nam;
ng han ng;
ng han ngc;
+ Theo a iem che tao
ng han nha may;
ng han cong trng;
45
+ Theo tnh lien tuc cua ng han
ng han lien tuc;
ng han khong lien tuc;
Khoang cach ln nhat gia hai ng han, amax
:
amax
15tmin
: cau kien chu nen;
amax
30tmin
: cau kien chu keo hoac cac bo phan cau
tao;
tmin
: chieu day cua ban thep mong nhat;
46
47
Bang 2.3. Ky hieu cac loai ng han
2.1.5. Cac Loai Lien Ket Han Va Phng Phap Tnh
Toan
a.Lien ket oi au
+ Khi chu lc truc
Kiem tra ben:
(2.1)
48
Hnh 2.7. Lien ket han oi au thang chu lc truc
cwc
cwt
ww
wf
f
tl
N
A
N
b
Trong o:
N: lc keo hoac nen;
Aw: dien tch tnh toan cua ng han oi au;
t: be day tnh toan cua ng han, bang be day cua thep c ban (t = t
min);
lw: chieu dai tnh toan cua ng han, l
w = b - 2t;
b: chieu dai thc te cua ng han, chnh la chieu rong thep c ban;
c: he so ieu kien lam viec;
fwt
: cng o tnh toan cua ng han oi au khi chu
keo;
fwc
: cng o tnh toan cua ng han oi au khi chu
nen;
49
Khi cng tnh ton chu ko ca ng hn fwt
< f (f, cng
o tnh toan cua thep c ban), dung ng han xien;
(2.2)
50
Hnh 2.8. Lien ket han oi au xien chu lc truc
cwv
w
w
cwc
cwt
w
w
ftl
N
f
f
tl
N
cos
sin
Trong o:
w,
w: ng suat phap va ng suat tiep trong ng
han;
: goc nghieng cua ng han so vi phng cua lc truc N;
lw: chieu dai tnh toan cua ng han xien;
(2.3)
fwv
: cng o tnh toan cua ng han oi au khi chu
cat;
+ Khi chu M;
(2.4)
51
tb
lw 2sin
cwt
w
w fW
M
Trong o:
Ww: moment khang uon cua tiet dien ng han;
(2.5)
+ Khi chu M, V;
(2.6)
He so 1.15 ke en s phat trien cua bien dang deo
trong ng han.
52
6
2
w
w
tlW
ww
w
ww
w
cwtwwtd
tl
V
A
V
tl
M
W
M
f
2
22
6
15.13
b.Lien ket ghep chong dung ng han goc
+Tnh toan lien ket ghep chong chu lc truc
53
Hnh 2.9. Lien ket ghep chong
N N
a5tmin; t=25mm
t2 t1
Hnh 2.10. Cac tiet dien
lam viec
Tiet dien 1 (theo vat lieu ng han)
(2.7)
Tiet dien 2 (theo vat lieu cua thep c ban)
(2.8)
Trong o:
+ hf: chieu cao ng han goc;
+ lw: tong chieu dai tnh toan cua cac ng han;
+ f,
s: cac he so chieu sau nong chay cua ng han
ng vi cac tiet dien 1 va 2;
+ fwf
, fws
: cng o tnh toan chu cat quy c cua thep
ng han va thep c ban;
54
cwf
wff
flh
N
cws
wfs
flh
N
Khi thiet ke nen chon trc hf,
(2.8)
(fw)min
= min(ffwf
; sfws
);
lwmin
4hf va l
w 40mm;
lw 85
fh
f (ng han goc canh);
55
cwf
wfh
Nl
min)(
56 Bang 2.4. He so f va
s cua ng han goc
57
Bang 2.5. He so phan phoi noi lc N khi lien ket cac
thep goc vi thep ban
Loai thep goc Cach lien ket k 1 - k
eu canh 0.7 0.3
Khong eu canh
han theo canh
ngan
0.75 0.25
Khong eu canh
han theo canh
dai
0.6 0.4
c.Lien ket co ban ghep
e cac ban ghep truyen c lc, yeu cau:
Abg A (2.9)
Trong o:
Abg
: tong dien tch tiet dien cac ban ghep;
A: dien tch tiet dien cau kien c ban;
Tnh toan tng t lien ket ghep chong.
58
Hnh 2.12. Lien ket co ban ghep
Ban ghep
d.Lien ket hon hp
La lien ket oi au co them cac ban ghep vi cac ng
han goc.
+ Tnh toan
ieu kien ben:
(2.10)
59
Hnh 2.13. Lien ket hon hp
Ban ghep
N N
ccwt
bg
w fAA
N )(
fwt(c)
: cng o tnh toan cua ng han oi au khi chu
keo (nen);
Lc truyen qua ban ghep:
Nbg
= wA
bg (2.11)
Tong chieu dai can thiet cua ng han goc e lien ket mot ban ghep mot pha cua lien ket:
(2.12)
(fw)min
= min(ffwf
; sfws
);
e.Tnh toan lien ket han vi ng han goc chu moment
va lc cat
60
cwf
bg
wfh
Nl
min)(
+ Khi ch co M tac dung
Tnh theo vat lieu ng han (tiet dien 1)
(2.13)
Tnh theo vat lieu cua thep c ban (tiet dien 2)
(2.14)
Trong o:
(2.15)
(2.16)
Wwf(s)
: moment khang cua ng han theo tiet dien 1, 2;
61
cwf
wf
M fW
M 1
cws
ws
M fW
M 2
6
2
w
ffwf
lhW
6
2
w
fsws
lhW
+ Khi ch co V tac dung
Tnh theo vat lieu ng han (tiet dien 1)
(2.17)
Tnh theo vat lieu cua thep c ban (tiet dien 2)
(2.18)
Awf
, Aws
: dien tch tnh toan cua tiet dien ng han
tng ng vi cac tiet dien 1, 2;
Awf
= fh
flw (2.19)
Aws
= sh
flw (2.20)
+ Khi co M, V tac dung ong thi
62
cwf
wf
V fA
V 1
cws
ws
V fA
V 2
Tnh theo vat lieu ng han (tiet dien 1)
(2.21)
Tnh theo vat lieu cua thep c ban (tiet dien 2)
(2.22)
63
cwf
wfwf
td fA
V
W
M
22
cws
wsws
td fA
V
W
M
22
B. LIEN KET BOULONE
2.5. CAC LOAI BOULONE DUNG TRONG KET
CAU THEP
2.5.1. Cau Tao Chung Cua Boulone
a. Cau tao
64
Hnh 2.14. Cau tao cua boulone
d d0
Mu boulone
D
Phan b ren
l0
l
Than boulone: oan thep tron, d= 12 48mm; boulone neo co d 100mm;
d0: ng knh trong cua phan b ren;
Chieu dai cua phan ren: l0 2,5d;
Chieu dai boulone : l = 35 300 mm;
65
ecu (ai oc)
long en (em)
Hnh 2.15. Lien ket boulone
Thep c ban
Mu, ecu (ai oc) thng co hnh luc giac;
Long en (em): hnh tron phan phoi ap lc cua ecu len mat thep c ban;
b. Cac loai boulone
Tuy theo cach san xuat, vat lieu, tnh chat lam
viec cua boulone, co cac loai sau:
Boulone tho;
Boulone thng;
Boulone tinh;
Boulone cng o cao;
v.v
66
2.5.2. Boulone tho va boulone thng
c san xuat t thep cacbon bang cach ren, dap;
ng knh than boulone phai nho hn ng knh lo (lo loai C) t 2 3mm;
B bien dang nhieu khi lam viec chu trt;
ng dung:
Dung boulone (tho, thng) khi chung lam viec chu keo hoac e nh v cac cau kien khi
lap ghep;
Khong nen dung chung khi thep c ban co gii han chay f
y > 3800daN/cm
2;
67
2.5.3. Boulone tinh
Lam t thep cacbon, thep hp kim thap bang cach tien, o chnh xac cao;
ng knh than boulone phai nho hn ng knh lo (lo loai B) 0.3mm;
Khe h gia boulone va lo nho nen lien ket chat;
Co the lam viec chu cat;
ng dung:
Do tnh phc tap khi san xuat va lap at boulone
vao lo (phai dung bua go nhe) nen loai boulone
nay t dung.
68
2.5.4. Boulone cng o cao
c lam t thep hp kim, sau o gia cong nhiet;
e am bao kha nang chu lc cua lien ket boulone cng o cao, can gia cong mat cac
cau kien lien ket e tang tnh ma sat;
ng dung:
De che tao, kha nang chu lc ln, lien ket t bien dang nen c dung rong rai;
Thay the cho lien ket inh tan trong cac ket cau chu tai trong nang, tai trong ong;
69
2.6. S LAM VIEC CUA LIEN KET BOULONE
VA KHA NANG CHU LC CUA BOULONE
2.6.1. S Lam Viec Chu Trt Cua Lien Ket
Boulone (tho thng tinh)
a. Kha nang lam viec chu cat cua boulone
70
a. Kha nang lam viec chu cat cua boulone
71
Hnh 2.15. S pha hoai do cat cua boulone
a. Kha nang lam viec chu cat cua boulone
Khi ng knh boulone nho, ban thep day, boulone co the b pha hoai do cat ngang than;
Kha nang chu cat cua mot boulone c tnh theo cong thc:
[N]vb
=fvb
bAn
v (2.23)
Trong o:
fvb
: cng o tnh toan chu cat cua vat lieu
boulone;
b: he so ieu kien lam viec cua lien ket
boulone;
A: dien tch tiet dien ngang cua than boulone;
72
a.Kha nang lam viec chu cat cua boulone
nv: so lng mat cat tnh toan cua boulone, phu
thuoc vao so lng cau kien chu lc c lien
ket;
Khi co hai cau kien: nv = 1;
Khi co ba cau kien: nv = 2;
73
74
Bang 2.5. Cng o tnh toan chu cat fvb
va keo ftb cua
boulone
Trang
thai
lam
viec
Ky
hieu
Cap o ben
4.6 4.8 5.6 5.8 6.6 8.8 10.9
Cat fvb
150 160 190 200 230 320 400
Keo ftb
170 160 210 200 250 400 500
n v tnh: N/mm2
75
Bang 2.6. He so ieu kien lam viec b
76
Bang 2.7. Dien tch tiet dien cua boulone A, Abn
, cm2
(TCVN 1916:1995)
d, mm 16 18 20 22 24 27 30 36 42 48
p, mm 2 2.5 2.5 2.5 3 3 3.5 4 4.5 5
A 2.01 2.54 3.14 3.8 4.52 5.72 7.06 10.17 13.85 18.09
Abn
1.57 1.92 2.45 3.03 3.52 4.59 5.6 8.16 11.2 14.72
p: bc ren;
Abn
: dien tch thc cua tiet dien than boulone (a
tr giam yeu do ren);
b. Kha nang lam viec chu ep mat cua boulone
77
Hnh 2.16. S lam viec ep mat cua boulone
b. Kha nang lam viec chu ep mat cua boulone
Neu khoang cach gia cac lo boulone hoac t lo boulone en mep ban thep qua ngan th ban
thep co the b pha hoai trt (cat t theo cac
ng trt 2-3) do tac dung ep mat cua
boulone len thanh lo;
x,
y: cac ng suat trong ban thep;
Kha nang chu trt cua ban thep khi xem chieu dai trt l = a,
S = 2atfv (2.24)
Trong o:
a: khoang cach t trong tam lo boulone en
mep ban thep;
78
t: chieu day ban thep;
fv: cng o tnh toan chu cat cua thep lien ket;
Kha nang chu ep mat cua mot boulone c tnh theo cong thc:
[N]cb
= fcb
bd(t)min (2.25)
Trong o:
fcb
: cng o tnh toan chu ep mat cua boulone;
(t)min : tong chieu day nho nhat cua cac ban
thep cung trt ve mot pha;
79
80
Bang 2.8. Cng o tnh toan chu ep mat fcb
cua boulone
2.6.2. S Lam Viec Chu Trt Cua Lien Ket
Boulone Cng o Cao
Lc ma sat gia cac ban thep hoan toan tiep nhan lc trt do ngoai lc gay nen;
Boulone ch chu keo do s xiet chat ecu;
81
Hnh 2.17. S lam viec chu trt cua boulone cng o
cao
Kha nang chu trt cua mot boulone c tnh theo cong thc:
[N]b
= fhb
b1A
bn(/
b2)nf (2.26)
Trong o:
fhb
: cng o chu keo tnh toan cua vat lieu
boulone, fhb
= 0.7fub
;
fub
: cng o tc thi tieu chuan cua vat lieu
boulone;
: he so ma sat;
nf: so lng mat phang ma sat tnh toan;
Khi co hai ban thep lien ket: nf = 1;
Khi co ba ban thep lien ket: nf = 2;
82
b1
: he so ieu kien lam viec cua lien ket
boulone, gia tr phu thuoc vao so lng boulone
chu lc na;
b1
= 0.8 neu na < 5;
b1
= 0.9 neu 5 na < 10;
b1
= 1 neu na 10;
b2
: he so o tin cay cua lien ket;
83
84
Bang 2.9. He so ma sat va he so o tin cay b2
2.6.3. S Lam Viec Cua Boulone Khi Chu Keo
Kha nang chu keo cua mot boulone c tnh theo cong thc:
[N]tb
= ftb
Abn
(2.27)
ftb
: cng o tnh toan cua vat lieu boulone khi
lam viec chu keo;
85
Hnh 2.18. S lam viec chu keo cua boulone
2.7. TNH TOAN LIEN KET BOULONE
2.7.1. Tnh toan lien ket boulone chu lc truc
86
Hnh 2.19. Lien ket boulone chu lc truc
a. Chon ng knh boulone va kch thc cac
ban ghep
Cong trnh thong thng: d = (20 24)mm;
Cong trnh nang: d = (24 30)mm;
Kch thc ban ghep:
Abg A (2.28)
Trong o:
Abg
: tong dien tch tiet dien ngang cua cac ban
ghep;
A: dien tch tiet dien cua cau kien c lien ket;
Nen bo tr boulone theo phng vuong goc vi phng cua lc;
87
b. Tnh toan so lng boulone theo ieu kien
chu cat va ep mat
oi vi boulone (tho, thng, tinh), so lng boulone can thiet c tnh theo cong thc:
(2.28)
Trong o:
[N]minb
= min([N]vb
, [N]cb
);
Cau kien c ban b giam yeu do lo boulone, kiem tra ben cac ban thep theo cong thc:
(2.29)
88
cbNN
nmin
bl
n
fA
N
Trong o:
An: dien tch tiet dien thc cua ban thep c lay
nh sau:
oi vi boulone (tho, thng, tinh)
89
Hnh 2.20. Kiem tra ben ban thep
Khi boulone bo tr song song, tiet dien kiem tra la tiet dien 1-1:
An = A A
1 (2.30)
Trong o:
A1: dien tch giam yeu do cac lo boulone gay ra;
A1 = mtd
1 (2.31)
m: so lng lo tren mot hang boulone;
t: chieu day cau kien mong nhat;
d1: ng knh lo boulone;
Khi boulone bo tr so le th,
A1 = max(A
15; A
12345 s2t/4u) (2.32)
90
Trong o:
A15
: dien tch giam yeu do cac lo xep tren ng
15;
A12345
: dien tch giam yeu do cac lo xep tren
ng 12345;
91
Hnh 2.21. Cach xac nh dien tch thc
s: bc lo so le;
t: chieu day thanh thep co lo;
u: khoang cach ng lo;
bl: he so ieu kien lam viec, c lay nh sau;
+ bl = 1.1: dam ac, cot, ban noi;
+ bl = 1.05: ket cau thanh cua mai va san;
oi vi boulone cng o cao, so lng boulone can thiet c tnh theo cong thc:
(2.33)
[N]b: kha nang chu lc trt cua mot boulone;
92
cba
N
Nn
Kiem tra ben cac ban thep theo cong thc:
(2.34)
Khi chu tai trong tnh: An = A neu A
n 0.85A;
Khi An < 0.85A, tnh theo dien tch quy c
Ac = 1.18A
n;
Khi chu tai trong ong: An ;
bl = 1;
2.7.2. Tnh toan lien ket boulone khi chu keo
(2.35)
93
bl
n
fA
N
ctbNN
n
Trong o:
N: lc keo tac dung vao lien ket;
[N]tb
: kha nang chu keo cua mot boulone;
c: he so ieu kien lam viec;
2.7.3. Tnh toan lien ket boulone chu moment
va lc cat
M = Nili = N
1l1 + N
2l2 + + N
ili (2.36)
Trong o:
N1: lc tac dung len day inh ngoai cung;
Ni: lc tac dung len day inh th i;
li: canh tay on cua cac cap ngau lc N
i;
94
95
Hnh 2.22. Lien ket boulone chu moment va lc cat
Ni = N
1li/l
1 (2.37)
(2.38)
(2.39)
lmax
= l1: khoang cach gia hai day boulone
ngoai cung;
Goi m, so lng boulone tren mot day mot
pha cua lien ket;
Lc tac dung len mot boulone do M: (2.40)
96
2
1
122
2
2
1
1
1 ... ii ll
Nlll
l
NM
2
max
max1
il
MlNN
cbi
blM Nlm
Ml
m
NN min2
maxmax
oi vi boulone (tho, thng, tinh)
[N]minb
= min([N]vb
, [N]cb
); (2.41)
oi vi boulone cng o cao
[N]minb
= [N]b (2.42)
Lc tac dung len mot boulone do V:
NblV
= V/n (2.43)
n: so lng boulone tren mot na lien ket;
Lc tac dung len mot boulone do M, V: (2.44)
97
cbblVblMbl NNNN min22
98
Bang 2.10. Quy nh bo tr boulone
2.8. BO TR BOULONE
Khoang cach min
99
Hnh 2.23. Bo tr boulone dang song song
Khoang cach min
100
Hnh 2.24. Bo tr boulone dang so le
Khoang cach max (cau kien chu keo)
101
Hnh 2.25. Bo tr boulone cho cau kien chu keo
Khoang cach max (cau kien chu nen)
102
Hnh 2.26. Bo tr boulone cho cau kien chu nen
103
Hnh 2.27. Bo tr boulone cho thep goc
Chng 3
DAM THEP
3.1.AI CNG VE DAM VA HE DAM
3.1.1.Phan Loai Dam
Dam la mot loai cau kien c ban, chu uon la chu yeu;
Dam co cau tao n gian;
Dam dung lam dam san cong tac, dam cau chay, dam mai, dam cau, v.v
Chia dam lam hai loai: dam hnh, dam to hp;
104
a.Dam hnh
La dam c lam t mot thep hnh, tiet dien ch , ch , ch Z;
Dam ch co tiet dien oi xng theo ca hai truc, co W
x kha ln nen thng s dung cho
nhng dam chu uon phang nh lam dam san
nha, dam san cong tac, v.v
105 Hnh 3.1. Tiet dien dam hnh
Dam hnh ch , co tiet dien khong oi xng theo phng truc y-y;
Khi dam chu uon phang hien tng xoan;
Khi dam chu uon xien hp ly;
Dung lam xa go mai, dam tng,v.v
b.Dam to hp
La tiet dien c tao thanh t cac thep ban, thep hnh;
Dam to hp han boulone inh tan;
106
107
Hnh 3.2. Tiet dien dam to hp
3.1.2. He Dam Thep
a.He dam n gian
La he ch co mot he thong cac dam bo tr song song vi canh ngan cua o san;
Ban san lam viec nh ban ke hai canh;
108
Hnh 3.3. He dam n gian
b.He dam pho thong
109
Hnh 3.4. He dam pho thong
La he gom hai he thong dam at vuong goc vi nhau va song song vi hai canh cua o ban;
Ban san lam viec nh ban ke bon canh;
Dung he dam pho thong khi (L x B 36 x 12m) hoac khi san chu tai trong q 3000daN/m2;
c.He dam phc tap
Dung khi san chu tai trong q > 3000daN/m2;
Cac dam trong he dam c lien ket vi nhau bang ba cach:
Lien ket chong
Lien ket bang mat
Lien ket thap
110
111
Hnh 3.5. He dam phc tap
Lien ket chong
Lam tang chieu cao kien truc cua he san;
Ban san ch c goi len hai canh nen o cng va kha nang chu lc cua san khong cao;
112
Hnh 3.6. Lien ket chong
Lien ket bang mat
Giam chieu cao kien truc cua he san hoac co the tang c chieu cao cua dam;
Ban san ch c goi len bon canh nen o cng va kha nang chu lc cua san cao;
113
Hnh 3.7. Lien ket bang mat
Lien ket thap
Ban san ch c goi len hai canh nen o cng va kha nang chu lc cua san khong cao;
114
Hnh 3.8. Lien ket thap
3.1.3. Cau Tao Va Tnh Toan Ban San Thep
Khoang cach cac dam va chieu day ban san thep EJ, kha nang chu lc cua ban san;
Tnh toan ban san thep
Xac nh chieu day thep ban lam ban san t;
Nhp ban san l;
Tnh toan thiet ke cac dam ban san;
Thong ke vat lieu cho ban san, he dam;
115
Bieu thc gan ung gia l, t:
(3.1)
116
Bang 3.1. Quan he gia tai trong tac dung len
san va chieu day ban san thep
cqn
En
t
l4
0
10 72115
4
Trong o:
n0 = [l/];
= 0.3, he so Poisson cua thep;
117
21 1
EE
S o tnh toan ban san thep
118 Hnh 3.9. S o tnh toan ban san thep
Moment ln nhat gia nhp ban c xac nh theo cong thc:
(3.2)
Trong o:
l: nhp tnh toan cua ban;
: o vong gia nhp ban do tai trong tieu
chuan qc va lc keo H gay ra;
(3.3)
0: o vong gia nhp ban do tai trong tieu
chuan qc gay ra;
119
1
1
80
2
max MHql
M
1
10
(3.4)
: ty so gia lc keo H va lc ti han le Ncr
,
xac nh theo phng trnh sau:
(3.5)
H: lc keo tac dung tai goi ta ban;
(3.6)
(3.7)
Q: he so o tin cay cua tai trong;
120
x
c
IE
lq
1
4
0384
5
2
02 31
t
tEl
H
l
EIH
Q
x
1
22
2
2
4
Kiem tra o vong va o ben cua cau kien chu keo uon ong thi:
(3.8)
Trong o:
A, Wx: dien tch, moment khang uon oi vi truc
x-x cua dai ban day t, rong mot n v (1m);
[]: o vong gii han cho phep;
f: cng o tnh toan chu keo cua thep;
ng han goc co chieu dai mot n v, chieu cao h
f phai u chu lc keo H:
121
; fW
M
A
H
c
x
max
(3.9)
(f)min
= min[(f, f
wf); (
s, f
ws)]
f,
s, f
wf , f
ws : cac he so va cng o tnh toan
cua ng han goc;
3.2.CAC KCH THC CHNH CUA DAM
3.2.1. Chieu Dai Dam, Nhp Dam
Khoang cach nh v L gia hai goi ta nhp danh ngha;
L0: khoang thong thuy;
L1: chieu dai che tao, L
1 = L -
122
cf
f
Hh
min
123 Hnh 3.10. Kch thc chnh cua dam
: sai so che tao, = (5 10)mm;
l: nhp tnh toan, l = L;
3.2.2. Chieu Cao Cua Tiet Dien Dam
Chieu cao tiet dien dam, h:
hmin
h hmax ; h hkt (min)
hmin
: chieu cao am bao cho dam u cng trong
suot qua trnh s dung;
hmax
: chieu cao cho phep u e bo tr he dam va
ban san;
Xac nh chieu cao hmin
o vong ln nhat tai gia dam
124
(3.10)
Trong o:
gc, p
c: tnh tai va hoat tai tieu chuan tac dung
tren mot n v chieu dai dam;
l: nhp dam;
EI: o cng chong uon cua tiet dien dam;
Moment uon
M = (gc
g + p
cp)l
2/8 (3.11)
(3.12)
125
EI
lpg cc
384
5 4
)(48
5 2
p
c
g
c
cc
pgEI
pgMl
Quan he M = fW, I = Wh/2
(3.13)
tb
: he so vt tai trung bnh;
Cho = []
T (3.13) (3.14)
Xac nh chieu cao kinh te, hkt
(3.15)
126
tbEh
fl
24
5 2
p
c
g
c
cc
tb pg
pg
1
l
E
flh
tb24
5min
w
ktt
Wkh
Trong o:
k: he so phu thuoc vao cau tao tiet dien dam;
k = 1.15 1.2 dam to hp han;
k = 1.2 1.25 dam to hp boulone (inh tan);
tw: chieu day ban bung dam;
Xet anh hng cua chieu cao dam, hw va
chieu day ban bung dam, tw
(3.16)
w = h
w/t
w: o manh cua ban bung dam;
127
3
2
3 Wh wkt
128
Bang 3.2. Ty so chieu cao va chieu day ban
bung san thep
3.3. THIET KE DAM THEP HNH
3.3.1. Chon Tiet Dien Dam
Moment khang uon yeu cau
(3.17)
Khi ke en s phat trien cua bien dang deo cua thep cho phep tang kha nang chu M
(3.18)
Cac ieu kien ap dung khi s dung he so c1
Tai trong tnh
129
c
xyc
xf
MW
max
c
xyc
xfc
MW
1
max
3.3. THIET KE DAM THEP HNH
3.3.1. Chon Tiet Dien Dam
Thep lam dam co fy 53kN/cm2
Tiet dien khong oi
ieu kien on nh tong the c am bao
ng suat tiep, 0.9f
Chon Wx W
x
yc
130
131
Loi tit
din Hnh dng tit din c1
1
0,25
0,5
1,0
2,0
1,19
1,12
1,07
1,04
2
0,5
1,0
2,0
1,40
1,28
1,18
3
0,25
0,5
1,0
2,0
1,19
1,12
1,07
1,04
Bang 3.3. He so c1
w
f
A
A
y
y
x x
Af Aw
Af
x x
y
y
x x
y
y
Af
Aw 0,5Af
Af
Af 0,5Aw
x x
y
y
132
Loi tit
din Hnh dng tit din c1
4
0,5
1,0
2,0
1,40
1,28
1,18
5 - 1,47
6
0,25
0,5
1,0
2,0
1,47
0,5Aw
Af
0,25Af
y
y
x x
y
y
xx
y
x x
y
a) b)
y
x x
y
Af
0,5Aw 0,5Aw
w
f
A
A
Bang 3.3. He so c1 (tiep theo)
3.3.2. Kiem Tiet Dien Dam a Chon Theo ieu
Kien Cng o
a.Kiem tra ieu kien ben ve uon
(3.19)
Trong o:
M: moment uon tai tiet dien kiem tra;
Wnx
: moment khang uon cua tiet dien thc oi
vi truc x-x;
133
c
nx
c
nx
fWc
M
fW
M
1
3.3.2. Kiem Tiet Dien Dam a Chon Theo ieu
Kien Cng o
b.Kiem tra ieu kien ben ve cat
(3.20)
Trong o:
V: lc cat tai tiet dien can kiem tra;
S: moment tnh cua phan tiet dien nguyen ben
tren th can tnh ng suat cat oi vi truc x-x;
Ix: moment quan tnh cua tiet dien nguyen oi
vi truc x-x;
fv: cng o tnh toan ve cat cua thep lam dam;
tw: chieu day ban bung cua thep hnh a chon;
134
cv
wx
ftI
VS
3.3.2. Kiem Tiet Dien Dam a Chon Theo ieu
Kien Cng o
Trng hp tai tiet dien kiem tra, ban bung b giam yeu do khoet lo (inh tan, boulone)
(3.21)
= a(a d) (3.22)
Trong o:
a: khoang cach tam hai lo (inh tan, boulone);
d: ng knh lo inh;
135
cv
wx
ftI
VS
3.3.2. Kiem Tiet Dien Dam a Chon Theo ieu
Kien Cng o
c.Kiem tra ban bung dam chu ng suat cuc bo
136
Hnh 3.11. S o xac nh chieu dai quy c
chu tai cuc bo cua ban bung dam
3.3.2. Kiem Tiet Dien Dam a Chon Theo ieu
Kien Cng o
Khi ben tren canh dam co tai tap trung;
Ban bung khong co sn cng gia cng;
Kiem tra ieu kien ben cua ban bung
(3.23)
Trong o:
p: ng suat cuc bo;
F: gia tr cua tai trong tap trung phan bo trc tiep
tren chieu rong b;
lz: chieu dai phan bo quy oi cua tai trong tap
trung F;
137
c
zw
p flt
F
3.3.2. Kiem Tiet Dien Dam a Chon Theo ieu
Kien Cng o
Khi dam khao sat la dam thep hnh
lz = b + 2h
y = b + 2(t
f + r) (3.24)
Trong o:
tf: chieu day canh dam;
r: ban knh cong chuyen tiep t bung sang canh;
d.Kiem tra tiet dien dam chu ong thi (, , p )
Kiem tra ben theo cong thc
(3.25)
138
cpptd f 15.13222
d.Kiem tra tiet dien dam chu ong thi (, , p )
Trong o:
(3.26)
, p: mang dau (+) neu la keo, dau (-) neu la
nen;
Inx
: moment quan tnh cua tiet dien thc;
y: khoang cach t bien tren cua chieu cao tnh
toan cua bung dam en truc trung hoa;
139
yI
M
nx
3.3.3. Kiem Tra o Vong Cua Dam
(3.28)
/l: gia tr o vong tng oi cua dam, do to hp
cac tai trong tieu chuan gay ra;
140
ll
141
Loi cu kin vng cho php
Dm ca sn nh v mi:
1. Dm chnh
2. Dm ca trn c trt va, ch tnh vng cho ti trng tm thi
3. Cc dm khc, ngoi trng hp 1 v 2
4. Tm bn sn
L /400
L /350
L /250
L /150
Dm c ng ray:
1. Dm sn cng tc c ng ray nng 35 kg/m v ln hn
2. Nh trn, khi ng ray nng 25 kg/m v nh hn
L /600
L /400
X g:
1. Mi lp ngi khng p va, mi tm tn nh
2. Mi lp ngi c p va, mi tn mi v cc mi khc
L /150
L /200
Dm hoc gin cu trc:
1. Cu trc ch lm vic nh, cu trc tay, palang
2. Cu trc ch lm vic va
3. Cu trc ch lm vic nng v rt nng
L /400
L /500
L /600
Sn tng:
1. Dm tng xy
2. Dm tng nh (tn, fibr ximang), dm ca knh
3. Ct tng
L /300
L /200
L /400
Ghi chu: L l nhp ca cu kin chu un. i vi dm console th L ly bng 2 ln vn ca
dm.
Bang 3.4. o vong cho phep cua cau kien chu uon
3.3.4. Kiem Tra On nh Tong The Cua Dam
Kiem tra on nh tong the dam theo cong thc
(3.29)
Trong o:
Wc: moment khang uon cua tiet dien nguyen
cho th bien cua canh chu nen;
c = 0.95: he so ieu kien lam viec;
b: he so, phu thuoc vao tham so
1
(3.30)
: he so, phu thuoc dang tai trong he so ,v.v;
142
c
cb
fW
M
2
0
2
1lfI
hEI
x
y
143 Bang 3.5. He so cho dam I co hai truc oi xng
3.3.4. Kiem Tra On nh Tong The Cua Dam
Vi thep I can nong,
(3.31)
h: chieu cao tiet dien dam;
It: moment quan tnh xoan cua dam;
lo: chieu dai tnh toan ngoai mat phang dam cua
canh nen;
He so b lay nh sau
Neu 1 0.85, lay
b =
1
Neu 1 > 0.85,
b = 0.68 + 0.21
1 1 (3.32)
144
2
054.1
h
l
I
I
y
t
3.4. THIET KE DAM TO HP
3.4.1. Chon Tiet Dien Dam
145 Hnh 3.12. Tiet dien ngang dam to hp han
3.4. THIET KE DAM TO HP
3.4.1. Chon Tiet Dien Dam
a.Xac nh chieu cao dam
Chieu cao tiet dien dam, h:
hmin
h hmax ; h hkt
b.Xac nh chieu day ban bung dam
Chieu day nho nhat cua ban bung, tw c xac
nh theo ieu kien ban bung u chu Vmax
(3.33)
Khi h = (1 2)m (3.34)
146
cvw
wfh
Vt
2
3 max
1000
37
htw
3.4. THIET KE DAM TO HP
3.4.1. Chon Tiet Dien Dam
Neu khong dung sn e gia cng ban bung dam
(3.35)
c.Xac nh cac kch thc cua tiet dien canh
dam
Xac nh tiet dien canh dam han: tf, b
f
(3.36)
147
E
fht ww
5.5
122
23
max
2
ww
cfk
ff
ht
f
hM
htb
3.4. THIET KE DAM TO HP
3.4.1. Chon Tiet Dien Dam
Cac yeu cau cau tao
tf = (12 24)mm
bf 30mm
e thoa man ieu kien on nh cuc bo cua ban canh nen
(3.37)
e ng suat phap phan bo eu tren chieu rong canh keo va am bao on nh cuc bo cho
canh nen, chon:
bf 30t
f (3.38)
148
f
E
t
b
f
f
3.4. THIET KE DAM TO HP
3.4.1. Chon Tiet Dien Dam
Nham am bao ieu kien on nh tong the cua dam va de lien ket vi cac cau kien khac,
bf = (0.2 0.5)h; b
f 180mm; b
f 0.1h
Xac nh tiet dien canh dam inh tan (boulone)
Chon tiet dien thep goc canh dam
(3.39)
tg = t
w; (3.40)
149
hbg
12
1
9
1
gg bt
11
1
10
1
150
Hnh 3.13. Tiet dien dam to hp inh tan
3.4. THIET KE DAM TO HP
3.4.1. Chon Tiet Dien Dam
Chon tiet dien ban phu canh dam
Id = I I
w I
g (3.41)
(3.42)
Id = 0.5n
1b
th
2 (3.43)
Trong o:
Ig: moment quan tnh cua tiet dien mot thep
goc oi vi truc x-x;
Ag: dien tch tiet dien cua thep goc a chon;
151
ggogwwxd AaIhthW
I 23
4122
3.4. THIET KE DAM TO HP
3.4.1. Chon Tiet Dien Dam
Iog
: moment quan tnh cua tiet dien mot thep goc
oi vi truc trong tam cua chnh no, tra bang;
ag: khoang cach t truc trong tam thep goc en
truc trung hoa;
Id: moment quan tnh cua tiet dien cac ban phu
hai canh dam oi vi truc x-x;
n1: so lng ban phu moi canh dam;
h: khoang cach trong tam cac ban phu hai
canh dam, h = h (12 24)mm;
152
3.4. THIET KE DAM TO HP
3.4.1. Chon Tiet Dien Dam
Chieu rong can thiet cua ban phu
b 2b
g + t
w (3.44)
Khoang cach t tam inh tan ngoai cung en mep ban phu, a
1
a1 15t
(khi canh dam dung mot ban phu)
a1 8t
(khi canh dam dung hai ban phu)
3.4.2. Kiem Tra o Ben, o Vong Cua Dam To
Hp (tng t nh dam hnh)
153
3.4.3. Thay oi Tiet Dien Dam Theo Chieu Dai
Dam
154
Hnh 3.14. Cac cach thay oi tiet dien dam
Hnh 3.4.3.a Bien oi chieu cao dam theo bieu o M
Hnh 3.4.3.b Bien chieu day ban canh dam
Hnh 3.4.3.c Bien oi be rong ban canh dam
i
3.4.3. Thay oi Tiet Dien Dam Theo Chieu Dai
Dam
Giam tiet dien tai v tr co moment be;
Thay oi tiet dien dam bang cac cach sau
Giam chieu cao bung dam v tr au dam
Giam chieu day canh dam
Giam chieu rong canh dam
Cau tao chieu rong mi cua ban canh, bf1
bf1
180mm;
bf1
0.5bf;
bf1
0.1h
155
3.5. ON NH TONG THE CUA DAM THEP
3.5.1. Hien Tng Va Nguyen Nhan
156
Hnh 3.15. Mat on nh tong the cua dam
3.5.2. Tnh Toan Dam Theo ieu Kien On nh
Tong The
a. Kiem tra on nh tong the dam theo cong thc
(3.45)
Vi dam to hp han ch
(3.46)
Trong o:
hf: khoang cach trong tam hai canh dam;
a = 0.5hf;
157
c
b
fW
M
ff
w
ff
w
tb
at
bh
tl 32
0 18
3.5.2. Tnh Toan Dam Theo ieu Kien On nh
Tong The
b. Khi dam co mot trong cac ieu kien sau th
khong can kiem tra on nh tong the
Co ban san BTCT hoac ban san thep u cng lien ket mot cach chac chan vi canh nen cua
dam;
(3.47)
(neu bf/t
f
3.5.2. Tnh Toan Dam Theo ieu Kien On nh
Tong The
c. Bien phap tang cng on nh tong the
S dung ban san (BTCT, thep);
Hieu chnh cac ty so bf/t
f , b
f/h
f ;
Giam l0 bang cach bo tr them he giang, thanh
chong ngang;
159
3.6. ON NH CUC BO CUA BAN CANH, BAN
BUNG DAM TO HP
Ban canh nen chu tac dung cua ng suat nen;
Vung ban bung au dam chu tac dung cua ng suat cat;
Vung ban bung gia dam chu tac dung cua ng suat uon;
Cac ng suat tren ban canh, ban bung b venh ra ngoai mat phang cua no mat on nh
cuc bo cua dam.
160
3.6.1. On nh Cuc Bo Cua Ban Canh Nen
161
Hnh 3.16. Mat on nh cuc bo cua canh dam
3.6.1. On nh Cuc Bo Cua Ban Canh Nen
ieu kien ben cua ban canh nen dam
(3.48)
Chieu rong b0f = b
0 c lay nh sau
162
f
E
t
b
f
f5.0
0
163
3.6.1. On nh Cuc Bo Cua Ban Canh Nen
Bang 3.6. Gia tr gii han [b0/t
f]
164
hw
bo
o
r r
bo
hw
r ao
bo
hw
r
r r
bo
bo
r ao
ao
bo
bo
Hnh 3.17. S o tiet dien ngang cua nh hnh cong
3.6.1. On nh Cuc Bo Cua Ban Canh Nen
a.Mat on nh cuc bo do tac dung cua ng suat
tiep
165
3.6.2. Mat On nh Cuc Bo Cua Ban Bung Dam
Hnh 3.18. Mat on nh cuc bo cua ban bung
dam do ng suat tiep,
a.Mat on nh cuc bo do tac dung cua ng suat
tiep
166
e am bao on nh cuc bo, ban bung cua dam to hp phai c tang cng bang cac
sn cng theo cac quy nh sau
o manh quy c cua ban bung
(3.49)
Neu > 3.2 khi dam chu tai trong tnh;
Neu > 2.2 khi dam chu tai trong ong;
Ban bung phai c tang cng bang cac
sn cng ngang;
E
f
t
h
w
ww
w
w
a.Mat on nh cuc bo do tac dung cua ng suat
tiep
Khoang cach gia cac sn cng ngang
a 2hw khi > 3.2
a 2.5hw khi 3.2
Chieu rong sn
Khi bo tr cap sn oi xng
bsn
= bs = h
w/30 + 40mm (3.50)
Khi bo tr cac sn mot ben cua ban bung
bsn
= bs = h
w/24 + 50mm (3.51)
Chieu day sn, (3.52)
167
w
w
E
fbt ss 2
168
Hnh 3.19. S o dam c tang cng bang cac sn
cng
b.Mat on nh cuc bo cua ban bung dam do tac
dung cua ng suat phap
169
Hnh 3.20. Mat on nh cuc bo cua ban bung dam do tac
dung cua ng suat phap
b.Mat on nh cuc bo cua ban bung dam do tac
dung cua ng suat phap
Di tac dung cua , phan chu nen cua ban bung b phong len tao thanh cac song vuong
goc vi ban bung dam hien tng mat on
nh cuc bo cua ban bung dam do tac dung cua
ng suat phap;
Neu > 5.5, th ngoai sn cng ngang con phai tang cng ban bung bang cac sn cng
doc;
Kch thc sn cng doc
(3.53)
170
w
wsd tt 75.0
wsd tb 10
b.Mat on nh cuc bo cua ban bung dam do tac
dung cua ng suat phap
Khong can kiem tra on nh cuc bo cua ban bung dam khi
3.5, trong trng hp khong co ng suat cuc bo;
2.5, trong trng hp co ng suat cuc bo;
171
w
w
c.On nh cua ban bung dam do ,
172
(3.54)
(3.55)
(3.56)
, : ng suat (phap, tiep) cua th mep ban
bung tai tiet dien kiem tra;
(3.57)
(3.58)
M, V: gia tr trung bnh cua moment uon va lc
cat trong o kiem tra;
cr
, cr
: ng suat phap va ng suat tiep ti han
cua ban bung dam;
173
c.On nh cua ban bung dam do ,
Wh
Mhw
wwth
V
174
c.On nh cua ban bung dam do ,
(3.59)
175
c.On nh cua ban bung dam do ,
Bang 3.7. He so ccr
oi vi dam to hp han
Bang 3.8. He so
176
c.On nh cua ban bung dam do ,
(3.60)
177
c.On nh cua ban bung dam do ,
Hnh 3.21. S o dam c tang cng bang cac
sn cng
a, b) Lc F at canh chu nen, chu keo
178
c.On nh cua ban bung dam do ,
(3.61)
(3.62)
c,cr
: ng suat phap cuc bo ti han;
179
c.On nh cua ban bung dam do ,
(3.63)
(3.64)
(3.65)
180 Bang 3.9. He so c
1
181
c.On nh cua ban bung dam do ,
(3.66)
182 Bang 3.10. Gia tr
c /
183
Bang 3.11. He so c2
Trong moi trng hp cr
eu c tnh theo
kch thc thc cua o ban;
3.7.1. Lien Ket Canh Dam Vi Ban Bung
184
3.7. CAU TAO VA TNH TOAN CAC CHI TIET
CUA DAM
Hnh 3.22. S lam viec cua lien ket canh vi bung
dam to hp
3.7.1. Lien Ket Canh Dam Vi Ban Bung
Khi dam chu uon, ban canh co xu hng trt tng oi so vi ban bung, ng han phai chu
c lc trt o;
Goi T la lc trt tren mot n v chieu dai dam
Trong o:
V: lc cat tnh toan;
Ix: moment quan tnh cua tiet dien oi vi truc
trung hoa x-x;
185
x
f
wI
VStT (3.67)
Sf: moment tnh cua phan tiet dien b trt oi
vi truc trung hoa x-x;
Kha nang chu lc cua ng han
2hf(f
w)min
c T = VS
f/I
x (3.68)
(fw)min
= min[(ffwf
), (sfws
)];
Chieu cao can thiet cua ng han
(3.69)
Khi tren canh dam han co lc tap trung F
186
3.7.1. Lien Ket Canh Dam Vi Ban Bung
cxwf
fIf
VSh
min
2
(3.70)
Vi dam to hp inh tan (boulone)
Lc trt moi inh phai chu
(3.71)
Kha nang chu lc cua mot inh tan
(3.72)
187
cw
zx
f
ff
l
F
I
VS
h
min
22
2
3.7.1. Lien Ket Canh Dam Vi Ban Bung
aI
VSTaT
x
f
b
aI
VSTN
x
f
bcb min
Bc inh, a
(3.73)
188
3.7.1. Lien Ket Canh Dam Vi Ban Bung
f
xcb
VS
INa
min
a. Dam thep hnh
189
3.7.2. Cau Tao Va Tnh Toan Moi Noi Dam
Hnh 3.23. Noi dam hnh dung ng han oi au
Noi bung dam trc, noi cac ban canh dam sau (e giam ng suat han bien hnh han);
o ben chu keo cua ng han oi au ch lay bang 85% o ben chu keo cua thep lam
dam;
noi dam nhng tiet dien co M 0.85Mmax
190
a. Cau Tao Va Tnh Toan Moi Noi Dam Thep
Hnh
191
a. Cau Tao Va Tnh Toan Moi Noi Dam Thep
Hnh
Noi dam nhng tiet dien co M > 0.85Mmax
Hnh 3.24. Noi dam hnh dung ng han oi au va ban noi
bf bbn
Cac ng han oi au va ban noi phai chu toan bo M tai tiet dien noi, hnh 3.24c;
Moment do tiet dien ng han oi au noi canh va bung dam phai chu
Mw = W
wfwt
c (3.74)
Ww: moment khang uon cua tiet dien ng han
oi au;
fwt
: cng o chu keo cua ng han oi au;
Moment ma ban noi canh dam phai chu
Mbn
= M - Mw (3.75)
192
a. Cau Tao Va Tnh Toan Moi Noi Dam Thep
Hnh (M > 0.85Mmax
)
Dien tch tiet dien ban noi
(3.76)
hbn
: khoang cach trong tam hai ban noi hai
canh, hbn
= h + (12 20)mm (3.77)
Chieu rong ban noi
bbn
= bf - (16 20)mm (3.78)
Chieu day ban noi
tbn
= Abn
/bbn
(3.79)
193
a. Cau Tao Va Tnh Toan Moi Noi Dam Thep
Hnh (M > 0.85Mmax
)
cbn
bnbn
fh
MA
ng han goc lien ket ban noi vi canh dam phai u chu lc truyen qua ban noi, N
bn
Nbn
= Mbn
/hbn
(3.80)
Tong chieu dai ng han lien ket mot na ban noi vi canh dam
(3.81)
Thng chon trc hf t
bn
194
a. Cau Tao Va Tnh Toan Moi Noi Dam Thep
Hnh (M > 0.85Mmax
)
fcw
bnf
hf
Nl
min
195
bf bbn
a. Cau Tao Va Tnh Toan Moi Noi Dam Thep
Hnh (M > 0.85Mmax
)
Hnh 3.25. Noi dam hnh dung ng han oi au va ban noi
Xet hnh 3.24d, cac quan niem
Moment tac dung tai tiet dien noi do cac ban noi canh dam chu;
Lc cat tac dung tai tiet dien noi do cac ban noi bung dam va cac ng han goc chu;
Dien tch can thiet cua tiet dien ban noi canh
(3.82)
Chieu rong, chieu day ban noi, chieu dai ng han xac nh tng t nh s o hnh
3.24c;
196
a. Cau Tao Va Tnh Toan Moi Noi Dam Thep
Hnh (M > 0.85Mmax
)
cbn
bnbn
fh
MA
Chng 4
COT THEP
4.1. KHAI QUAT CHUNG
4.1.1. ac iem Chung
Cot la ket cau thang ng lam nhiem vu cac ket cau khac nh dam, dan, v.v va truyen tai trong t cac ket cau o xuong mong.
Cot co ba bo phan chnh
au cot;
Than cot;
Chan cot;
197
4.1. KHAI QUAT CHUNG
4.1.2. Cac Loai Cot
Theo s dung
Cot nha cong nghiep;
Cot nha khung nhieu tang;
Cot san cong tac;
Cot ng day tai ien;
v.v
Theo cau tao
Cot ac;
Cot rong;
198
Theo cau tao
Cot tiet dien khong oi;
Cot tiet dien thay oi;
v.v
Theo s o chu lc
Cot nen ung tam;
Cot nen lech tam;
Cot nen uon;
199
4.1. KHAI QUAT CHUNG
4.1.2. Cac Loai Cot
200
a.S o tnh
S o tnh cua cot la truc doc cua cot co cac
lien ket chan cot va au cot theo cac phng.
b.Chieu dai tnh toan
Chieu dai tnh toan cua cot l0 phu thuoc vao s
o tnh va noi lc doc trong cot.
oi vi cot tiet dien khong oi hoac cua cac oan cot bac, l
0
l0 = l (4.1)
201
4.1.3. S o Tnh, Chieu Dai Tnh Toan Va o
Manh Cua Cot
Trong o:
l: chieu dai hnh hoc cua cot;
: he so chieu dai tnh toan;
oi vi cot tiet dien thay oi, l0
l0 =
jl (4.2)
j: he so chieu dai tnh toan bo sung;
202
4.1.3. S o Tnh, Chieu Dai Tnh Toan Va o
Manh Cua Cot
203
204
S hnh dang cot l1/l Khi t s Imin/Imax bng
0,01 0,1 0,2 0,4 0,6 0,8 1,0
- - 1,35 1,24 1,14 1,08 1,02 1,0
- - 1,66 1,45 1,24 1,14 1,06 1,0
0,0 1,69 1,35 1,25 1,14 1,08 1,03 1,0
0,2 1,45 1,22 1,15 1,08 1,05 1,02 -
0,4 1,23 1,11 1,07 1,04 1,02 1,01 -
0,6 1,07 1,03 1,02 1,01 1,01 1,00 -
0,8 1,01 1,00 1,00 1,00 1,00 1,00 -
Imin Imax
ImaxImin
l1
l
ImaxImin
c.o manh cua cot
(4.3)
Trong o:
ix, i
y: cac ban knh quan tnh cua tiet dien cot
tnh theo truc x, y;
Cot nen ung tam: x =
y (4.4)
Cot lam viec bnh thng: max
[] (4.5)
205
4.1.3. S o Tnh, Chieu Dai Tnh Toan Va o
Manh Cua Cot
y
y
y
x
xx
i
l
i
l
206
a.Tiet dien dang ch H
207
4.2. COT AC CHU NEN UNG TAM
4.2.1. Hnh Thc Tiet Dien
a.Tiet dien dang ch H
De lien ket vi cac ket cau;
Thoa man cac yeu cau ve kien truc;
Hnh thc n gian, de che tao;
b.Tiet dien dang ch thap
208
Cau tao n gian;
Lien ket vi cac ket cau khac phc tap;
Kho thoa man cac yeu cau ve kien truc;
c.Tiet dien kn
209
b.Tiet dien dang ch thap
Co ban knh quan tnh ln hn tiet dien h cung dien tch;
ap ng c x
y
Hnh thc tiet dien gon;
Kho bao dng c mat ben trong cua tiet dien;
210
c.Tiet dien kn
a.Tnh toan ve ben
(4.6)
Trong o:
N: lc doc tnh toan;
An: dien tch tiet dien thc (a tr cac giam yeu);
f: cng o tnh toan cua vat lieu thep;
c: he so ieu kien lam viec cua cot;
211
4.2. COT AC CHU NEN UNG TAM
4.2.2. Tnh Toan Cot ac Chu Nen ung Tam
c
n
fA
N
b.Tnh toan ve on nh tong the
(4.7)
Trong o:
A: dien tch tiet dien nguyen (cha tr phan
giam yeu);
min
: he so uon doc nho nhat;
Cac cach xac nh min
Tnh theo cong thc
212
4.2. COT AC CHU NEN UNG TAM
4.2.2. Tnh Toan Cot ac Chu Nen ung Tam
cfA
N
min
b.Tnh toan ve on nh tong the
Khi
(4.8)
Khi
Khi
(4.10)
213
4.2. COT AC CHU NEN UNG TAM
4.2.2. Tnh Toan Cot ac Chu Nen ung Tam
5.20
E
f53.5073.01
5.45.2
2
53.50275.03.27371.01347.1
E
f
E
f
E
f
5.4
51
3322
b.Tnh toan ve on nh tong the
Trong o:
: o manh quy c, (4.11)
c.Tnh toan ve on nh cuc bo
Trong cac ban thep co ng suat phap nen, n;
n [
n] ban thep b bien dang ra ngoai mat
phang cot b mat on nh cuc bo;
e kha nang chu lc cua cot khong b han che bi ieu kien on nh cuc bo, [
cb] [
tt]
214
4.2. COT AC CHU NEN UNG TAM
4.2.2. Tnh Toan Cot ac Chu Nen ung Tam
E
f
(4.12)
Trong o:
hw: chieu cao tnh toan cua ban bung;
tw: chieu day ban bung;
[hw/t
w]: o manh gii han cua ban bung;
hw/t
w 2[h
w/t
w] t
w = const (neu cot am bao
ieu kien on nh tong the);
Khi o phan ban bung ch co oan 2c1 cung
tham gia lam viec vi canh;
215
c.Tnh toan ve on nh cuc bo
c.1.ieu kien on nh cuc bo cua ban bung
w
w
w
w
t
h
t
h
216
Hnh 4.5. Tiet dien cot ac to hp han
c1: phan ban bung hu dung;
(4.13)
Khi h > 1m ma ieu kien on nh cuc bo cua ban bung khong thoa gia cng bung cot
bang mot cap sn doc;
Kch thc cua sn doc
217
c.Tnh toan ve on nh cuc bo
c.1.ieu kien on nh cuc bo cua ban bung
w
ww
t
htc 5.01
wsd tt 75.0
wsd tb 10
218
Hnh 4.6. Sn gia cng ban bung cot
219
Bang 4.3. o manh gii han [hw/t
w] cua ban bung cot
ac nen ung tam
Khi bo tr sn doc th cac sn nay phai c ke vao tiet dien tnh toan cua cot;
gia tr o manh gii han cua ban bung cot la:
Tr so c xac nh nh sau:
Khi Isd
6hwtw
3
(4.14)
220
c.Tnh toan ve on nh cuc bo
c.1.ieu kien on nh cuc bo cua ban bung
w
w
t
h
3
3
3
1.01
4.01
ww
sd
ww
sd
th
I
th
I
Khi Isd
> 6hwtw
3 = 1
Isd
: moment quan tnh cua sn doc oi vi truc
bung cot vuong goc vi canh bsd
;
hw: chieu cao tnh toan cua bung cot khi cha
at sn doc;
Khi
can gia cng ban bung bang cac oi sn
ngang e cot khong b mat on nh cuc bo di
tac ong cua ng suat tiep, .
221
c.Tnh toan ve on nh cuc bo
c.1.ieu kien on nh cuc bo cua ban bung
f
E
t
h
w
w 3.2
Kch thc cua sn ngang
: khi bo tr cap sn oi xng
: khi bo tr sn mot ben
c.2.ieu kien on nh cuc bo cua ban canh
(4.15)
222
E
fbt snsn 2
mmh
b wsn 4030
mmh
b wsn 5024
c.Tnh toan ve on nh cuc bo
c.1.ieu kien on nh cuc bo cua ban bung
ff t
b
t
b 00
b0: chieu rong tnh toan cua phan ban canh nho
ra;
tf: chieu day ban canh;
[b0/t
f]: o manh gii han cua phan ban canh nho
ra;
223
c.Tnh toan ve on nh cuc bo
c.2.ieu kien on nh cuc bo cua ban canh
224
Bang 4.4. o manh gii han [b0/t
f] cua phan ban
canh nho ra
Kha nang theo ieu kien ben
[N]b = A
nf
c (4.16)
Kha nang theo ieu kien on nh tong the
[N] = minAfc (4.17)
Kha nang chu nen ung tam cua cot
[N] = min {[N]b; [N]} (4.18)
225
d.Kha nang chu nen ung tam cua cot ac
a.Chon tiet dien cot ( to hp)
Xac nh dien tch can thiet cua tiet dien cot
(4.19)
: he so uon doc c gia thiet trc hoac c xac nh theo
gt;
gt
= 100 120, khi N 1500kN;
gt
= 70 100, khi N = 1500 3000 kN;
gt
= 50 70, khi N = 3000 4000 kN;
gt
= 40 50, khi N 4000 kN;
226
4.2.3. Xac nh Tiet Dien Cot ac Chu Nen
ung Tam
c
ycf
NA
Xac nh kch thc tiet dien ban canh va ban bung
(4.20)
x,
y: cac he so, tra bang;
Theo yeu cau cau tao
h = (1 1.15)b
tf = (8 40)mm
tw = (6 16)mm
227
a.Chon tiet dien cot ( to hp)
gty
y
yc
lb
gtx
xyc
lh
228
Kiem tra ben; Kiem tra on nh tong the; Kiem
tra on nh cuc bo; Kiem tra o manh;
c.Xac nh tiet dien cot theo o manh
Xac nh Ayc
, byc
, hyc
; gt
= []
Kch thc tiet dien c chon
A Ayc
; ix i
xyc; i
y i
yyc
Trong o:
229
b.Kiem tra tiet dien cot
y
yyc
xxyc
li
li
Lien ket canh va bung cot to hp c lay theo cau tao
ng han dai suot chieu dai cot;
hf = (6 8)mm;
230
d. Lien ket canh va bung cot
231
4.3. COT RONG CHU NEN UNG TAM
4.3.1. Cau Tao Than Cot
232
Cot rong co he thanh bung (thanh giang) cot rong thanh giang;
Cot rong co cac ban giang cot rong ban giang;
Kch thc tiet dien cau tao cua ban giang
tb = (6 12)mm; t
b = (1/10 1/30)d
b; t
b 1/50b
b
db = (0.5 0.8)h
Trong o:
bb: chieu dai cua ban giang;
h: be rong mat rong cua cot;
233
4.3. COT RONG CHU NEN UNG TAM
4.3.1. Cau Tao Than Cot
a.S lam viec cua cot rong oi vi truc thc y-y
o manh cua cot oi vi truc thc y-y
(4.21)
Ban knh quan tnh cua tiet dien cot
(4.22)
Trong o:
Af: dien tch tiet dien nhanh; A
f = A/2
234
4.3. COT RONG CHU NEN UNG TAM
4.3.2. S Lam Viec Cua Cot Rong
y
y
yi
l
0
00
2
2y
f
y
f
y
y iA
I
A
Ii
iy0
, Iy0
: ban knh quan tnh va moment quan tnh
cua tiet dien nhanh oi vi truc y0 (y
0 trung y);
b.S lam viec cua cot rong oi vi truc ao x-x
o manh ban au cua cot oi vi truc ao x-x
(4.23)
(4.24)
o manh thc (o manh tng ng), 0
0 =
x
t (4.25)
235
4.3.2. S Lam Viec Cua Cot Rong
a.S lam viec cua cot rong oi vi truc thc y-y
x
xx
i
l
A
Ii xx
t: he so ke en anh hng bien dang cua he
bung rong;
(4.26)
1: goc trt cua tiet dien cot do V = 1 n v gay
ra;
236
4.3.2. S Lam Viec Cua Cot Rong
b.S lam viec cua cot rong oi vi truc ao x-x
2
2
11x
t
EA
237
c. o manh tng ng 0 cua cot rong ban
giang
= 1
= 1
Gia thiet: iem gia chieu dai cac oan nhanh
va ban giang co M = 0 va xem la khp.
o cng n v, n cua cac oan nhanh cot va ban giang
(4.27)
Trong o:
Ix0
: moment quan tnh cua tiet dien nhanh oi
vi truc x0-x
0;
Ib: moment quan tnh cua ban giang
Ib = t
bd
b
3/12 (4.28)
238
c. o manh tng ng 0 cua cot rong ban
giang
aI
CIn
b
x0
C: khoang cach trong tam hai nhanh cot;
a: khoang cach trong tam cac ban giang;
Goc trt, 1 do V = 1 n v gay ra
(4.29)
Trong o:
1 a/i
x0 : o manh cua nhanh (4.30)
ix0
: ban knh quan tnh cua tiet dien nhanh oi
vi truc x0 ;
He so, t
239
c. o manh tng ng 0 cua cot rong ban
giang
EA
n
12
1211
(4.31)
o manh tng ng, 0 cua cot rong ban
giang hai nhanh
(4.32)
Khi n 1/5, EIb
(4.33)
240
c. o manh tng ng 0 cua cot rong ban
giang
2
2
1182.01x
t n
nx 182.02
1
2
0
2
1
2
0 x
241
d. o manh tng ng 0 cua cot rong thanh
giang
Goc trt, 1
(4.34)
Trong o:
: bien dang doc truc cua thanh bung xien do lc cat V = 1 n v gay ra cho ca hai mat rong;
(4.35)
Nb: tong lc doc cua cac thanh bung xien hai
mat rong tren cung mot tiet dien do V = 1 gay
ra;
242
d. o manh tng ng 0 cua cot rong thanh
giang
sincos1
dla
1d
db
EA
lN
(4.36)
(4.37)
Trong o:
Ad1
: tong dien tch tiet dien cua cac thanh bung
xien hai mat rong;
Ad1
= 2At (vi he thanh bung tam giac);
At: dien tch tiet dien cua mot thanh bung xien;
: goc nghieng cua truc thanh bung xien vi truc nhanh cot;
243
sin
1bN
d. o manh tng ng 0 cua cot rong thanh
giang
2
1
1sincos
1
dEA
(4.38)
(4.39)
Trong o:
ld: chieu dai truc thanh bung xien;
o manh tng ng cua cot rong hai nhanh
(4.40)
244
d. o manh tng ng 0 cua cot rong thanh
giang
2
1
11xd
tA
A
2
3
2
2
1
10
cossin aC
ld
1
12
0
d
xA
A
(4.41)
An = 2A
fn
Afn
: dien tch tiet dien thc cua nhanh cot;
b.Tnh toan ve on nh tong the
(4.42)
min
xac nh theo max
= max{0;
y}
c.Tnh toan ve on nh cuc bo (nh cot ac)
245
4.3.3.Tnh Toan Cot Rong Chu Nen ung Tam
a.Tnh toan ve ben
c
n
fA
N
cfA
N
min
max
[]
o manh cua cac nhanh cot, 1 (4.42a)
Cot rong ban giang, 1 < 40 va
1 <
y
Cot rong thanh giang, 1 80 va
1
y
e. Kha nang chu nen ung tam cua cot rong
(tnh toan nh cot ac)
246
4.3.3.Tnh Toan Cot Rong Chu Nen ung Tam
d. Cac yeu cau ve o manh
a.Chon tiet dien cot
Xac nh dien tch tiet dien nhanh cot
(4.43)
y c xac nh theo
ygt = 40 90
Xac nh ban knh quan tnh yeu cau
(4.44)
247
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen
ung Tam
cy
fycf
NA
2
ygt
y
yyc
li
Chon nhanh cot va kiem tra cot theo truc thc
T Afyc
, iyyc
chon thep hnh lam nhanh cot sao cho thoa man ieu kien:
(4.45)
Trong o:
A = 2Af
y xac nh theo
y (theo tiet dien a chon);
iy = i
y0: ban knh quan tnh cua tiet dien nhanh
oi vi truc y0;
248
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen ung
Tam
a.Chon tiet dien cot
y
y
y
c
y
i
l
fA
N
Xac nh khoang cach hai nhanh, C
Can c vao s lam viec cua cot oi vi truc ao x-x;
ieu kien hp ly 0 =
y ;
Cot rong ban giang (n 1/5)
(4.46)
1: chon s bo theo (4.42a);
Cot rong thanh giang
(4.47)
249
2
1
2 yxyc
1
12
d
yxycA
A
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen ung
Tam
a.Chon tiet dien cot
S bo chon trc thep goc lam thanh bung xien
1 va A
d1;
Xac nh ixyc
(4.48)
Khoang cach yeu cau hai nhanh
(4.49)
(4.50)
ix0
: ban knh quan tnh cua nhanh oi vi truc x0;
250
xyc
xxyc
li
2
0
22 xxycyc iiC
x
xyc
yc
ih
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen ung
Tam
a.Chon tiet dien cot
He thanh giang va ban giang c tnh toan vi lc cat, V
f sinh ra khi cot b uon doc quanh truc ao;
(4.51)
Trong o:
N: lc doc tnh toan cua cot;
= f(0);
Lc cat, Vs tac dung tren mot mat rong cua cot
Vs = V
fn
r (4.52)
nr = 0.5 : cot rong hai nhanh;
251
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen
ung Tam
b. Tnh toan ban giang va thanh bung
N
f
EeV f
233015.7 6
252
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen
ung Tam
b.1. Tnh toan ban giang
Chon db, t
b , khoang cach cac ban giang a;
Chieu dai tnh toan lf;
Xem cac ban giang va hai nhanh
cot nh mot khung mot nhp nhieu
tang chu bien dang trt do Vf;
Moment uon, lc cat trong ban
giang
Mb = 0.5aV
s (4.53)
Tb = aV
s/C (4.54)
253
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen
ung Tam
b.1. Tnh toan ban giang
Kiem tra ben ban giang va tnh toan lien ket ban giang vi nhanh cot (M
b, T
b);
b.2. Tnh toan thanh bung
254
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen
ung Tam
b.1. Tnh toan ban giang
Lc doc trong thanh bung xien
(4.55)
Trong o:
nt = 1, he thanh bung tam giac;
nt = 2, he thanh bung hnh thoi;
He thanh bung ch thap co thanh ngang
(4.56)
255
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen
ung Tam
b.2. Tnh toan thanh bung
sint
sd
n
VN
fu
t
sd N
n
VN
sin
Nfu
: lc doc phu trong thanh xien;
(4.57)
Nf: lc doc trong mot nhanh cot;
(4.58)
Chon tiet dien thanh bung
Gia thiet max
= gt
150 min
;
(4.59)
256
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen
ung Tam
b.2. Tnh toan thanh bung
f
tfd
fuA
ANN
33
2
2Cl
al
d
dd
gt
dyc
lii
min
Dien tch tiet dien yeu cau cua thanh bung xien
(4.60)
T Atyc
, iyc
tra bang chon tiet dien
Kiem tra thanh bung
(4.61)
Tnh toan lien ket thanh xien vao nhanh (Nd);
257
4.3.4. Xac nh Tiet Dien Cot Rong Chu Nen
ung Tam
b.2. Tnh toan thanh bung
c
dtyc
f
NA
min
c
t
d fA
N
min
258
4.4. COT CHU NEN LECH TAM, NEN UON
4.4.1. Cau Tao
Kch thc tiet dien: b, h
h = (1/8 1/14)lc : cot rong;
h = (1/10 1/15)lc : cot ac;
b = (0.3 0.5)h
b = (1/20 1/30)lc
lc: chieu dai cot;
4.4.2. Tnh Toan Cot ac Chu Nen Lech Tam,
Nen Uon
a.Tnh toan ve ben
259
4.4. COT CHU NEN LECH TAM, NEN UON
4.4.1. Cau Tao
4.4.2. Tnh Toan Cot ac Chu Nen Lech Tam,
Nen Uon
a.Tnh toan ve ben
Tiet dien cot giam yeu;
o lech tam tnh oi me > 20;
cot mat kha nang chu lc
Me = m (4.62)
Trong o:
m: o lech tam tng oi;
(4.63)
: he so ke en anh hng cua hnh dang tiet dien en s phat trien bien dang deo;
260
cNW
MAm
ieu kien ben cua cot
(4.64)
Khi cot khong chu trc tiep tai trong ong;
0.5fv; f
y 5300daN/cm2;
N/Anf > 0.1
ke en s phat trien bien dang deo;
(4.65)
nx, c
x, c
y: cac he so phu thuoc dang tiet dien;
261
4.4.2. Tnh Toan Cot ac Chu Nen Lech Tam,
Nen Uon
a.Tnh toan ve ben
c
ny
y
nx
x
n
fxI
My
I
M
A
N
1minmin
nycy
y
nxcx
x
n
n Wfc
M
Wfc
M
fA
Nc
b.1.Cot chu (N, Mx)
Tnh toan oi vi truc x
(4.66)
e = f(
x, m
e) - tra bang;
Tnh toan oi vi truc y
(4.67)
c: he so ke en anh hng cua Mx va hnh dang
tiet dien;
262
4.4.2. Tnh Toan Cot ac Chu Nen Lech Tam,
Nen Uon
b.Tnh toan ve on nh tong the
c
e
fA
N
c
y
fcA
N
Khi mx 5,
(4.68)
, : cac he so;
Khi mx 10,
(4.69)
Khi 5 < mx
264
Bang 4.9. He so ,
b.2.Cot chu (N, My)
(4.71)
b.3.Cot chu (N, Mx, M
y)
(4.72)
(4.73)
exy
xac nh nh e;
265
4.4.2. Tnh Toan Cot ac Chu Nen Lech Tam,
Nen Uon
b.Tnh toan ve on nh tong the
c
x
fA
N
43 4.06.0 cceyexy
c
exy
fA
N
c.1.Cac ieu kien on nh cuc bo cua ban canh
(4.74)
Cot co tiet dien khong la hnh hop
[b0/t
f], phu thuoc va xac nh nh cot nen
ung tam;
Cot co tiet dien hnh hop
[b0/t
f], phu thuoc va m;
266
4.4.2. Tnh Toan Cot ac Chu Nen Lech Tam,
Nen Uon
c.Tnh toan ve on nh cuc bo
ff t
b
t
b 00
Khi m 0.3, [b0/t
f] lay nh tren;
Khi m 1 va 2 + 0.04m
(4.75)
Khi m 1 va > 2 + 0.04m
(4.76)
Khi 0.3 < m < 1, [b0/t
f] c noi suy;
267
c.1.Cac ieu kien on nh cuc bo cua ban canh
f
E
t
b
f
0
mf
E
t
b
f
01.013.04.00
Cot tiet dien ch H, hnh hop co Ix > I
y va kha
nang chu lc cua cot c quyet nh bi ieu
kien on nh tong the trong mat phang uon;
Theo bang tra (4.10)
Cot tiet dien ch H, hnh hop co Ix > I
y va kha
nang chu lc cua cot c quyet nh bi ieu
kien on nh tong the ngoai mat phang uon;
[hw/t
w] = f(m, , )
(4.77)
268
c.2. Cac ieu kien on nh cuc bo cua ban bung
1
(4.78)
(4.79)
Trong o:
y: khoang cach t truc x en th chu nen nhieu
nhat cua ban bung;
y1: khoang cach t truc x en th xa nhat cua
ban bung chu keo do Mx;
269
c.2. Cac ieu kien on nh cuc bo cua ban bung
yI
M
A
N
x
x
11 yI
M
A
N
x
x
Khi 0.5
[hw/t
w], lay theo bang (4.10);
Khi 1
(4.80)
Trong o:
= 1.4(2 - 1)/ (4.81)
= V/hwtw (4.82)
Khi 0.5 < < 1, [hw/t
w] c noi suy;
270
c.2. Cac ieu kien on nh cuc bo cua ban bung
fEE
t
h
w
w 8.342
1235.4
22
271
Thng chon cot tiet dien ch H (oi xng hoac
khong oi xng);
b. Xac nh tiet dien cot H (oi xng)
Chon b, h
h = (1/10 1/15)lc;
b = (1/20 1/30)lc; b = (0.3 0.5)h
Xac nh dien tch tiet dien cot
(4.83)
272
4.4.3. Xac nh Tiet Dien Cot ac Chu Nen
Lech Tam, Nen Uon
a. Chon dang tiet dien cot
ce
ycf
NA
e: xac nh theo
x va m
x = e
x/
x = M
x/N