' # • # # # KHOA HOC - CONG NGHE
KHAO SAT VA DANH GIA DO VONG CUA D A M THEP KHI LAM VIEC NGOAI GIOI HAN DAN H O I DANG THlTC NGHIEM
Tom tat: Bai bao trinh bay thi nghiem xac dinh dp vong cua dam thep chiu u6n dwai tac dung cua tai trong tap trung khi lam viec ngoai giai han dan hdi Tren ca sa do nhan xet vi sw bien thien do vong cua dim.
Tir khoa: Dam chju u i n , chuyen vj, ngoai gidi ban dan h i i , thye nghiem.
Abstract: This paper represents a test determining sag of flexural steel beam under lumped load in extra elastic limited condition. Basing on its results, carrying out consider the sag variation of beam.
Keyword; Flexural beam, displacement, extra elastic limited condition, experiment.
LDATVANDE
Trong ITnh v y c t h i i t k i va thi edng k i t c i u thep noi Chung va cau thep ndi neng t h u d n g gap bai toan d i m chiu uon. De tan dung tdi da kha nang lam viee cua vat lieu thep, c i n t h i i t xem xet danh gia s y lam viec cua d i m ngoai gidi ban dan h i i . Trong tieu ehuan t h i i t k i e l u d u d n g bd [1] cung da tinh d i n s u lam viee ngoai gidi han dan hdi cua vat lieu. Nghien euu d i m thep chiu uon ngoai gidi han dan hdi (GHDH) bang ly thuyet da duge de cap den trong n h i i u tai lieu [2,3,4], Tuy nhien nghien cii'u bang thye nghiem thi con it d u p e de cap den. Dac biet viec xac dmh dp vdng ciia dam chiu udn ngoai GHDH bang thye nghiem con it d u a c d i cap trong cac tai lieu. Bdi vay v i n d i danh gia chuyen vj ciia dam thep khi lam viee ngoai gidi han dan hdi bang thye nghiem la van d i rat dang d u a c quan tam.
2. BAI TOAN
Oe khao sat va danh gia dp vdng ciia d i m thep chiu uon ngoai GHDH, trong khudn kho ed ban ciia bai bao, nhdm tac gia lua chon bai toan d i m gian dan mat e l t c h u I, chiu tac dung ciia luc tap Irung P tai chinh giu'a nhip (Hinh 1), Gia trj luc P dupe tang dan de tif dd xac djnh cac gia tri lyc P khi dam lam viec ngoai GHDH, Nhdm tac gia chpn ehiiu dai nhip tinh toan L ^ i,4(w);
dam dwac che tao tir thep hinh chd' I sd hieu 10 theo TCVN 1655:1975. Kieh thude d i m thuc t i dwac xac dinh lai trudc khi thi nghiem nhu sau. c h i i u cao /i = 98.s4(m';d, chieu rpng ban canh h-^2,94(mm)-, c h i i u day ban canh t^4,l{mni)^ tai trong ban than
I S . NGUYEN MANH THl/dNG Vien ky thuat cong trmh dac biet NCS.OANGTHITHUHI^N
Hpc vien ky thuat quan su
Hinh 1. Mo hinh dam nhip gian dan.
52 94
Hinh 2. Mat cat dam
J
q^6,61(kg/m) = 0,061(kNIm). Md men quan tinh' / ^ 1 2 5 ( c w ' ) , mo men khang uon W, =25,29(cni'); Mo men tmh ciia nua mat c i t . S^ =]6,23(t:m'). Thep CT3 CO gidi han chay F, = 220(Mpa)3. PHANLYTHUViT
Trudc tien, giai bai toan tren theo phuang phap ly t h u y i t da d u a c d i cap d i n trong cac tai lieu [2,3,4] d i tim khoang gia tri ciia lyc P ma d i m lam viec ngoai GHDH, Xet dieu kien dac chac.
Ban canh'
6 ^ 5 2 ^ ^ ^ ^ ^ ; 3 ^ ,
( 4,7 V
Nhu vay d i i u ki^n /l/ < \,- thda man. N h u vay canh dac e h l c .Bung ., = - ^ = - ^ ^ ^ ^ = l''.78;,^=3.76^'A = 3,7.^1li^ = n3 Dieu kien K < '^p, thda man N h u vay bung dac chac.
Thda man dong thai 2 d i i u kien canh dae c h i c va bung dae chac. Nhu v§y, dam cd t i i t dien dac e h l c .
caui!
So 3 nam 2020 |SMII
Dam CO kha nang chiu d u a c md men deo ma khdng CO p h i n t u nao bj mat i n dmh cue bd.
D i m b i t d i u lam viec ngoai GHDH khi ung s u i t t h d bien dat tdi gia tr; u'ng s u i t chay F , tire la xuat hien b i i n dang deo tai d i i m each xa true trung hda n h i t . Md men chay M
U^ - f • Jf ^(220.iO')-(25,29.10"") = 5.564(A-.V-;«)'
Tir do tinh dug'c
Sau dd n i u mo men uon t i i p tuc tang, thi m i i n b i i n dang deo se ldn d i n va tien v i trong tam mat e l t . Cac thd bien t i i p tuc gian them nhung khdng tang u'ng s u i t . Nhieu thd dat d u a c gia trj F va vimg deo an sau vao trong t i i t dien T i i t dien lam viec trong viing dan hdi- deo Khi moi thd deu dat dug'c gia trj F , toan bg t i i t dien chay deo. Md men uon ldn n h i t luc nay ma d i m chiu d u a c ggi la mo men deo M^.
M^,^t\ Z , - F •(2-Xj = (220 10') (2 16,23 10 ")-7,l4l(W-;<i|
TLK dd tinh d u a e
4. P H A H THlTC NGHIEM
Nhdm tac gia che tao md hinh dam thep nhip gian dan, mat e l t chu" I trong phdng thi nghiem. Khi thi nghiem u6n d i m , trudc khi danh gia do vong, c i n phai xac dmh gia trj lyc P ma dam c h u y i n trang thai lam viec td' giai doan dan h i i sang ngoai dan hoi, do dd trudc het can xac dinh gia tn b i i n dang tuang doi cua d i m b i n g thye nghiem. Sii' dung cac trang thiet bi gdm: may ghi s i lieu SCXI 1000 DC va bo phin mim xu'ly s6 lieu tren may tinh Labview, tenzomet do bien dang tuang ddi kieu la dien tra FLA 5-11 g i n vao k i t eau, cam b i i n do chuyen Vj CDP 50 de do dp vdng, kich gia tai,..cfi xac dinh bien dang twang doi va chuyin vi tai mat cit chinh giira dim dwai tac dung cua cac cip tai trong P khac nhau, Nhdm tac gia da t i i n hanh nhieu l i n thi nghierri, gia tai vdi n h i i u gia tn tai trong P khac nhau, vdi n h i i u doan d i m khae nhau. Dia diem thi nghiem tai cac phdng thi nghiem eua Vien ky thuat edng trinh dac biet Duui day la mot s6 hinh anh thi nghiem-
5. CAC KiT QUA CHINH THU DlTdC
Trude khi danh gia dwoc gia tri do vong, cin biet gia tri bien dang tuang ddi E ciia d i m thep de tie do b i i t cac m i c gia tri eiia lyc P thue nghiem ma tai dd trang thai lam viec cua d i m thay doi tiF giai doan dan h i i sang giai doan chay deo. K i t qua thi nghiem thu d u o c gia trj b i i n dang tuang ddi E the hien trong bang 1.
Phan tieh k i t qua thi nghiem eho t h i y
-Trong giai doan dan hoi gia tri b i i n dang tuang ddi giu'a thi nghiem va thye t i chenh nhau khdng nhieu (9-12%). Tiy dd cho t h i y r i n g thi nghiem eho k i t qua kha ehinh xac Sai sd ed the c h i p nhan d\sac do thuc t i mo hinh thuc nghiem khdng dupe ly tudng hoan toan va sai s i cua t h i i t bi do.
-Theo k i t qua thuc nghiem, d i m b i t d i u lam viee ngoai GHDH khi P:" =i9,62faV; D i m m i t kha nang chju lyc theo thuc nghiem khi tai trgng P^'" =3l.88AA' (khi dd d i m bi b i i n dang hoan toan, giu nguyen trang thai dii da gid tai. nhung chua phat hien v i t dift gay).
Tren ea s d eae cap tai thu dug'c d tren, de danh gia gia tri do vdng ciia d i m , Nhdm tae gia thuc hien viec khao sat gia tri do vdng ciia dam phu thude vao tai trpng. K i t qua thu duae nhu trong bang 2 Dya vao bang 2 cho thay trong giai doan dan h i i gia trj dp vdng git^'a thi nghiem va thuc t i chenh nhau khdng n h i i u (11-13%). Tif dd eho t h i y r i n g thi nghiem cho k i t qua kha chinh xae. Sai sd cd t h i c h i p nhan duac do thye t i md hinh thye nghiem khdng dug'c ly tudng hoan toan va sai sd ciia thiet bj do.
Dp vong cua dam khi dat den GHDH xac dinh bing thuc nghiem khi gia tri iuc tac dung P'" = 1 9 , 6 2 k N . D i m bl bien dang hoan toan, khdng trd v i duac trang t h a i t r u d c d d d u c f a g / d f a / v d i t a i t r p n g p'" = 3 1 8 8 * ^
I So 3 nam 2020
Xay dung bieu d i b i i n thien dp vong cua dam nhu hinh d u d i day.
m i
KHOA HOC - CONG NGH^
Bang 1. Bang gia tn bien dang twang doi t
Gia trj (kN) 5 00 10 30 1511
15 85
19 62
20 36
Bien dang tircrng doic etllipc ngtiiem
Ely tliuyet 0 000309 1 0 00035
Chenh lech TN-LT
(%)
-11.67
LTng suat o athipc nghiem 61,713
a l y thuyet 69.870 0.000646,0.00072, -978 129.179 ' 143183 0 000915
0 001082 lOJ)0105_
0.00111
-12 74 182,986 209.708
216.328 219 985
Ghi chu
Theo ly thuyet ' dim bit diu lam
viec ngoai gidi ' han dan tiii | Theo thuc nghiem i
dim bit diu lam viec ngoai gidi
han dan hoi Theo ly thuyet , toan bp mat cat '
dam chay deo Bang 2. Bang gia tri do vong
Gia tri llJCP (kN) 5 00 10.30 15,11 15,85 19,62 20,36 23 74 29 23
Do vong f (mm) fthlFC ngtiiem
1.29
LiZL-
' " M S "
516
5,70 6,52 31,88 8,84
thuyet 1,14 2,36 3 45 3 62
Chenh lech TN-LT (%) 11.63 13,49 12.61
- - '
Ghi chu '
Theo ly thuyit d§m bit diu lam viec ngoai gidi han dan hoi Theo ttiLKC ngtiiem dam bat dau lam
viec ngoai gidi tian dan hii Theo ly thuyet toan bo mat cat dam |
chay deo I
1
Ttieo thu'C ngtiiem dim bj bien dang
hoan toan |
Bleu dd do vong dam
— f IV thu vet
— -Pv iv thuyet
Tai tfongP(kNl
Hinh 6. Biiu dd biin thien dd vong
6.KiTlUAN
Qua phan tich bieu do gia tn dp vdng thye nghiem ciia dam cd t h i nhan thay nhu sau,
- Theo thye nghiem dd vdng trong giai doan dan hoi bien thien t u y i n tinh. ngay sau giai doan ngoai GHDH, do vdng van cd the coi la b i i n thien t u y i n tinh, nhung s u b i i n thien cham han, d i n giai doan g i n gidi han chiu luc thi do vdng tro* nen b i i n thien khdng con t u y i n tinh nOa, va s y b i i n thien trd nen r i t nhanh.
- Ngoai giai doan dan hdi, dam v i n cd kha nang chiu lyc, chua bj du't gay khi dp vdng ldn han dp vdng cho phep trong tieu chuan
L ^ L ( 8 0 0 • 2 5 0 * ^ -
- Trong khudn kho bai bao cd han va cac dieu kJen khac, nhdm tac gia ehua thye hien khao sat sy thay doi ciia gia trj chuyen vj ung vd-i c h i i u dai nhjp khac nhau, mat cat d i m khac nhau. Khi dam lam viee ngoai GHDH nhdm tac gia chua kiem chu'ng dupe dp vdng theo ly thuyet, Nhdm tac gia r i t mong ed d u a c s y trao doi ciia cae d i n g nghiep v i cac v i n dh naya
Ttil LIEU THAM KHAO
[1], Tieu chuan Quoc gia TCVN 11823:2017. T h i i t k i cau d u d n g bd. 2017.[2]. K i t cau thep-Cau ki^n ca ban. Pham Van Hgi (chii bien).
NXB Khoa hpc va ky thuat 2009,
[3], Thiet k i ket cau thep theo quy pham Hpa ki AISC 2005.
Doan Dinh Kien ( Chu bien).
NXB Khoa hoc va ky thuat 2010,
[4]. SiKc b i n vat lieu. GS.TS Hoang Xuan Iup'ng, TS. T r I n Minh. Hgc vi0n KTQS 2003
LJIUJOIHJ®
So 3 nam 2020 I
