Bạn đang xem bản rút gọn của tài liệu. Xem và tải ngay bản đầy đủ của tài liệu tại đây (163.67 KB, 3 trang )
<span class='text_page_counter'>(1)</span><div class='page_container' data-page=1>
TOM T A T :
Bai bao trinh biy vi?c khao sat bi^n dang
va idia nang chiu lUc cua cgt be tdng cot
thep xet anh hUdng cua cot dai theo tieu
chuan thi^t EC2, ACt318 va mdt so mo
hinh, qua do lam rd hon sU lam vigc ciia
cot BTCT va ki^n nghi v6i tieu chuan Viet
Nam.
ABSTRACT
The article analyzes the deflection and
load capacity survay of reinforced
concrete columns with the effect of
stirrup according to the designed codes
such as EC2, ACI 318 and some models.
Consequently responses of reinforced
concrete columns can be seen much more
clearly and suggested to the Viet Nam
TS. Nguyen Ngpc Phiitfng
TrUcfng DH Kien triic Ha Ndi
Di dong: 0903405450
Email: Phuong.nguyenngocphuong@
gmail.com
Dat van de
Cdt BTCT la cau kien chju lUC chinh trong
ket cau cong trinh, la cau ki6n chju nen, nen
-udn. Kha nang chiu k^o eiia be tdng kem n l n
toan b d lUc keo se do cot thep chiu, trong vUng
nen cd ca be tong va edt thep ciing cdng t i e
chiu tuc Do vay, neu nang cao dUOc eUdng d d
cua thep sir dung trong cdt se dan den hieu q u i
dang ke khi cdt lam viec. Theo tieu chuan t h i l t
ke ket eau be tong cot thep (BTCT] ciia Viet Nam
TCVN 5574 2012, vdi be tdng thUdng, bien dang
<i>eye han s* = 2.10 ^ mddun dan hoi e6a edt t h e p </i>
E = 2.10^ nen de dam b i o sU lam vi^c chung
giUa be tdng va cdt thep va han che lang phi,
Ung suat trong edt t h i p khdng qua 400 MPa
(cudng do tinh loan ve nen ciia cdt t h i p khdng
Idn hon 365 MPa) [1,2]. Vi vay, k h i nang chiu lUc
cda cdt BTCT khdng eao trong khi y l u cau ve
k h i nang chiu nen eiia edt, d i e biet vdi c6t nha
cao tang la lat Idn, dan den kich thUdc cdt Idn,
1 . Tieu chuSn M ^ ACI 318-2005 va chau
Au EC 2-2004
<i>1.1. Tieu chuan ACI 318-2005(3,6}: </i>
<i>- Ong suat eua be tdng khi cd kiem che n d </i>
<i>ngang- t\^ = V^+4,]o^ vdi: f'^ - cUdng d d chiu </i>
nen ciia b l t d n g ; o, - iing suat ciia cot dai:
sb. i: A - dien tich t i l t dien cot
dai, f - cudng d o cot dai, a - gdc nghieng cua
cot dai, s - k h o i n g each giCia cac cdt dai, b - kich
thudc canh eua Idi. sb^ - dien tich be mat l d i .
- Bien dang eua be tdng khi c6 Ung suat
kiem che n d ngang. e „ = - ^ vdi E - md d u n d i n
hdi ciia be tdng ^
- Kha nang chiu lUc cda cdt:
<i>[N]=0,8(0,85f'^i^^A^ -(- A^f^) - vdi \ - dienlkk </i>
t i l t dien cdt.
<i>1.2. Tieu chuan EC2-2004 [5,6]: </i>
<i>- Qng suat ciia be t d n g khi c6 kife cM </i>
n d ngang: f.k.c ^ ^ . k ^ + S ^ ) khi o^ s 0,OS|vi
f.k,. - f ^ ( 1 , 1 2 5 + 2 , 5 y i ) khi O; > 0,05f^^ \ffflfj\
cUdng d o chiu n l n ciia b l t d n g ; o^ - tiKingU
n h u Oj cda ACI.
- Bien dang ciia be t d n g khi c6 iing sui
<i>kiem che n d ngang: </i>
<i>^ciZf-^-= 0.002 </i>
- K h i nang chiu lUc cua c6t:
<i>[Nl=0,8(0,85f ; ^ / ^ + fiif) </i>
2 . M o t so m o h i n h
<i>2.1. Mo hinh cua Legeron vd Paultre (199SI </i>
cua cdt: 7 ^
<i>Hinh 1 Quan li& fing suat-bien dang cia be tong thfi </i>
liinh cua Legeron va Paultre
Md hinh i p dung cho cdt BT duoc kiSmc
1 0 B i n g 1. B i l n dang eiia b l t o n g khi cd kiem che n d nqanq
1
2
3
4
Tieu chuan va m d hinh
ACI 318-2005
EC2-2004
Legeron va Paultre
Salim Razvi v i Murat
Saatcioglu
" Sai so idn nhat glQa c i c t i l u
chuan v a m d hinh
B i l n dang eye han cda b l tdng £ „
M l
0,002
0,002
0,002
0,002
M2
0,0022
0,0024
0,0023
0,0030
36,4%
Sai sd so vdi M l
1 0 %
2 0 %
1 5 %
5 0 %
M3
0,0023
0,0027
0,0028
0,0037
50,9%
Sai sd so vdi M l
1 5 %
M4
0,0025
0,0030
0,0033
0,0045
8 0 %
Sai sd so vdi M l
2 5 %
5 0 %
6 5 %
1 2 5 %
B i n g 2. K h i nang chiu lye cOa cdt
- W K ( 1
lon9l}i[2
<i>' '4 </i>
khi(i,)M
T i l u chuan va m d hinh
ACI 318-2005
EC2-2004
Legeron va Paultre
Salim Razvi va Murat
Saatcioglu
betOKiiSai sd Idn n h i t giCfa c i c t i l u
' c h u a n v i m d h i n h
K h i nang chiu lye cua cdt (KN)
M l
2665
2438
2565
2665
M2
2846
2589
2884
2871
11.4%
Sai sd so vdi M l
6 , 8 %
6 , 2 %
8,2%
7 , 7 %
M3
Sai so so vdi M l
13,6%
12,4%
14,6%
13,8%
M4
3231
2910
3167
3196
1 1 %
Sai so so vdi M l
2 1 , 2 %
19,4%
18.8%
19,9%
=( . ( i l n 6 h i n h 1 . [ 3 , 4 ]
- iJng suc!t cda be t d n g khi cd kiem che
<i>^ ^ b ngang: r^ = [ 1 + 2 , 4 ( r / ' ] . f ; vdi i ; - chl so </i>
<i>leraiiriW -^'~^^*^ l3 3p iye han c h l n d ngang hieu </i>
ung, trong d d : A^^ - t o n g dien tich mat cat
gang ciia c i c tam v d boc theo phUdng tryc y
ong k h o i n g c i c h giUa cac cot dai s, c - dUdng
^, nh Idi b l t o n g han che n d ngang, f ^ - irng s u i t
\ Sng t r o n g cdt t h e p dai, K^ - he sd kiem c h l n d
<i>»^iB\gang hieu q u i : K=—~ voi M « ^ </i>
- -: ty' sd d i l n tfch cot t h i p doc tren dien tich b l
j n g han che n d n g a n g .
<i>BitifS' . Bi^n dang cda be t d n g khi cd <ing s u i t </i>
<i>i l m che n d ngang: i\^ = [1 +3,5(\\y-^].E\ </i>
<i><b>icotSTW 2.2. Mo hinh cua Salim Razvi vd Murat </b></i>
<i>iih'^^aatcioglu(1999): </i>
Signs' / • . !
hinga"* ,
;p|[ie(iic''~v
dij?**'
jjiJ^* tiinli 2. Quan hS ling suSt-bien dang cua be tong theo mo
hinh cua Salim va Murat Saatcioglu
Md hinh nay xet tdi t i t ca c i c yeu t d i n h
hudng n h u hinh dang cdt dai, ty- sd t h e tich cot
dai tren the tich Idi b l tdng, k h o i n g each va
gidi han ehay cua cot dai cung n h u cudng do
b l t d n g va kieh thUde hinh hoc cua cdt. Bieu dd
Ung s u i t - b i l n dang ciia be tdng theo m d hinh
nay duoc the hien d h i n h 2. [3,4]
- Cfng s u i t cua be t d n g khi cd k i l m
<i>che n d ngang: f'^ - f'^^ + k^f,^ vdi f ^^ = f'^ </i>
k,=5,7(fie)"''"; Ung s u i t kiem c h l nd ngang
tUdng dUOng f,^ = k^f, vdi f, - iing suat kiem che
<i>n d ngang bi d d n g , \hc djnh nhU o^ trong ACI; </i>
- 0 , 1 5 , <1,0
- Bien dang ciia be t o n g khi eo Ung s u i t kiem
, 40 , „
e h e n d n g a n g : £ = E (l-i-5k K) v d i k j = - : - < 1 . 0
v a K = -3—
<b>3. K h i o sat tinh t o a n : </b>
Khao sat b i l n dang eiia be t d n g cot va kha
nang chiu lUc cua cot cd hinh dang, kich thudc,
c i u tao va bo tri cot thep doc. dai n h u hinh 3.
Kich t h u d c tiet dien edt 400x400 m m . Tdng so
4 mau cot:
-I- Mau 1 ( M l ) chi cd edt doc, khong e d e d t
dai;
•1- M a u 2 ( M 2 ) : b 6 t r i c d t d a i , 4 ) 8 a l 0 0
<i>+ Mau 3 (M3): b o tri cdt d a i ; 4.8a50 </i>
•I- M a u 4 ( M 4 ) : b 6 t r i c d t d a i ( t > 1 0 a 5 0
-Thep doe chiu lUe ciia cdt sU d y n g 8iji20 va
edt dai sU dung t h i p cd cUdng d p c h i y deo f
= 295MPa (theo TCVN t u o n g d u o n g nhdm t h e p
CII).
- B l tdng:-)-Theo TCVN 5574-2012, si( d u n g
625: R^, = 25 MPa; R,, = 18,5 MPa
•H Theo ACI 318-2005: ^c ^ T ^ = T : ; ^ = ^0
<i>MPa ^'^^ ' ' ^ ^ </i>
•1- Theo EC2-2004: C20/25 cd f^^ = 20 MPa,
''icb* = 25 MPa, E,^ = 30x10^ MPa
Tinh toan theo ACI 318, EC2va eie m o hinh
neu tren. Cic k i t q u i tinh t o i n t h e hien trong
c i c bang 1 va bang 2.
Cd t h e thay rang khi CO su kiem ehe n d
ngang, bten dang cUc han eua be t d n g tang
Cd the thay rang k h i nang chiu lUc ciia cdt
theo EC2 la n h d nhat. Khi cd sy kiem c h l n d
ngang. k h i nang ehju luc ciia cot tang len, Idn
nhat la 21,2%. GiUa c i c t i l u chuan v i m d hinh
cd sy chenh lech nhau ve k h i nang chju lUc Idn
n h a t l a 1 l , 5 % .
Ket luan;
Khi cd sU kiem che nd ngang. bien dang va
cudng d o ciia be tdng duoc tang len. k h i nang
chiu lye cua cdt BTCT cung tang len, ed t h e tang
len k h o i n g 18 den 21 (%) va cd t h e sit d u n g
t h e p cd cudng d o cao han.
Gidi han c h i y ciia edt t h i p dai cd i n h h u d n g
B«20
BfflgQ . ? ^ \ *
SfflgQ
aesa
fl8Q50
8ggo
020 aim
<i>J 400 1 </i>
eiOo50
8050
Hinh 3. Cac man cot khao sat
dang ke den su k i l m che nd ngang ciia be tdng.
Viec cau tao cdt dai n h u dUdng kinh, khoang
each cdt dai theo phuang dUng va phuong
ngang, t J so giCfa ham lUOng edt dai va di&n tieh
Idi be tdng cd i n h hudng den viec kiem che nd
<i>ngang cUa b§ tdng. </i>
Cic k i t qua tren gdp phan cho cac ky sU
t h i l t k l ket cau trong nghien eUu ve sU lam viee
<b>T A I L I E U THAM KHAO </b>
LPhan Ouang Minh, Ngo The Phong, Nguyen Dinh Cong
<i>(2011), Ket ca'u be long cot thep, M. Khoa hot va ky thuat. Ha </i>
NOI
2. Tieu chuan Viel Nam (2012), TCVN 5574 2012, Ke't cau
be tong va be tong t o i thep -Tieu chuan thiet ke, Nxb. Xay dung,
Ha Noi.
3. ACI committee (2005), Building code reguirements
for structural concrete (ACI 318-05), Structrural Engineering
Handbook
4 Ed Chen Wai-Fah (1999), Structural cono¥te Des[gn,
Structrural Engtneering Handbook.
5 Eumtode 2. Design of contrete structures
6. MC Graw-Hill (1999), Ciifil Engineering Formulas,
Structrural Engineering Handbook.