OANH GIA MLPC MO C O A D A U VAO TRONG PHAN TICH MO K^T CAU
GS.TS Nguyin VSn Phd Trudng Dai hgc XSy dt/ng ThS. Nguyen Xuan An Trung tSm Cdng ngh$ thdng tin Sd TSi nguydn Mdi trudng HS Ndi
Tdm tat: Trong eSc bSi bSo trudc [1, 2], eSc tSc giS dS trinh bSy quS trinh phSn tich md kit eiu. Mirc md cda diu ra pbu thudc vSo mirc md cda diu vSo, eSc dSc trung eda kit eiu vS thuSt toSn phSn tieh. Tmng bSi bSo nSy, eSc tSe giS di xuit mgt phuong phSp dSnh giS mire md eda diu vSo thdng qua dSnh giS mirc md eda diu m bdi mdt xSc suit Di minh hoa cho phuong phSp, mit thi du don giin dS dugv xdt
Summary: In the previous papers [1,2], authors have presented methods for fuzzy analysis of structures. The fuzzy level of output depends on fuzzy level of input, structural eharacterlsties and algorithm of the analysis. The present paper deals with a method for fuzzy level assessment of input in fuzzy analysis of structures by means of determining of fuzzy level of output by a probabilistic value. A simple example Is considered.
I.MOTDAU
Trong ly thuydt thdng tin [5], ngudi la dung dpi lupng entropi de do dp khPng xde dinh (dp b i t dinh). O l dua ra djnh nghTa entropi cua mpt hipn tugng ngdu nhiPn, ngudi ta dd dua theo gid tri cda xdc suit P(Ai),P(A2),...,P(An) Id xdc suit xult hiPn eua cdc ket cyc ed the Ai,A2,...,An cda mpt phdp thd'. Vdi cdch ldm nhu vpy, vipc md rpng khdi nipm entropi cho trudng hpp phdn tich md k i t d u Id r l t khd khdn, vi trong tinh todn md k i t d u , cae gia thiet chpt che eda ly thuylt xdc suit du dd dugc md rpng khd dupe Ihda mdn.
V i n dd phdn tich md k i t d u dd dugc trinh bdy trong cdc ldi lipu [1, 2, 3, 4,...], trong dp, ngudi ta chi xdt cdc thupt todn phdn tieh, chua ddnh gid mirc md cua dau vdo. Vide ddnh gid mu'C md cda d i u vdo cP mpt y nghla quan trpng, dpc biel trong vipc giai md (defuzifier).
Giii md Id qud trinh ehuyen dau ra md ve mpt (hode mpt sd) gid tri i l l dinh (deterministic), dgi dipn eho dgi lucng md. Neu vide ehuyen ndy ed sai sd ldn, khPng ddng tin cpy thi vipc giai md vd qud trinh phdn tich m i t het y nghTa. Do dP, van de ddnh gia dp ehinh xde cua vipc giai md trong ede d'ng dyng thyc te d n phai dugc quan tam nghien ed'u. Song dp chinh xdc cda k i t qua giai md dau ra Ipi phu thupc vdo mu'C md cda dau vdo, thupt todn phdn lich vd cdc dpc trung cda k i t c l u .
Trong bdi bdo ndy chdng tdi d l xult djnh nghTa dP tin cdy cua ket qua giai md d i u ra. Id"
dd xdc djnh v l md'C md cda d i u vdo eho mpt qud trinh phdn tich d'ng vdi mpt ket c l u va mpt thuPt todn xdc djnh ndo dP. Oe minh hpa, mpt thi dy ve dam den gian, chju tai trpng tdp trung vd phdn bd ddu dd dup'c xPt.
TAP CHf KHOA HOC C O N G N G H $ XAY DUNG Sd06 -12/2009 5
2. DO TIN CAY CUA KtT QUA GIAI MOf OAU RA
Ket qua phdn tich md ket d u d the la mdt dai lugng md, mpt vecta md, mdt qud trinh md,... KhPng m i t tinh chat tdng qudt, de dan gian d c h trinh bay, sau day ta chi xPt cho tn/dng hap dau ra Id mpt dai lugng md (sd md).
Viec phdn tich md ket d u dugc thyc hien theo sa dd 6 budc nhu da trinh bdy trong cdc tdi lipu [1,2]. Ouai day, ta chi chu y den khdu giai mg va dp chinh xdc eda nd. Hien nay cP nhieu phuang phdp giai md, trong dd ed hai phuang phap chinh la phuang phap trpng tdm vd phuang phdp diem cyc dai.
Gia sd" theo k i t qua phdn tieh vd sd' dyng phuang phdp hdi quy, ta xde djnh duge hdm thupc eda dau ra Id hdm thupc tam gidc ABC (hinh 1). lir hdm thupc ndy, ta se giai md bing phuang phdp trpng tdm.
H(x)
M J ^
Hinh 1. Tam giSc hSm thude diu ra
Ky hipu I Id trpng tdm lam gide, ket qua giai md Id hodnh dp XM eua diem I trPn taic hodnh. Gia sd' dp sai Ipch eho phpp Id ±S. Ky hipu cdc doan thing DH va EF la d c doan thing song song vdi dudng cao cda tam gidc xult phdt tu B, cdch IM ve hai phia mpt doan 5.
Gpi dipn tich cda tam gidc ham thupc Id SABC. gpi dipn tich cda da gidc OEFBH IP SQEFBH Ojnh nghTa: Od tin cpy cda gid tri giii md XM Id ty sd:
D _ ^DEFBH
(1)
Ro rdng 0<P <\. Cdn cu' vdo gid tri eua P ta d the ddnh gid miPC md cda dau vdo.
3. Danh gia mirc m a cua ddu vao
Neu P ldn thi dp phdn tdn thip nghTa Id dp tin cdy cua k i t qua giai md cao. Ngugc lai ndu gid tri P be thi dp phdn tan Ign, nghTa Id dp tin cdy cda ket qua giai mg thap.
Gid tri P phy thupc vdo cdc tham sd sau:
- O l u vdo (cdc dde trung md eua dau vdo).
Thudt lodn phdn tich (phuong phdp tinh todn k i t d u ) .
- Ode tnrng ket d u (hinh hpc, vdt lidu, tai trpng) da dugc dua vao dau vdo.
6 TAP CHf KHOA HOC C O N G NGHE XAY DUNG Sd06-12/2009
- Phugng phdp giai md (phuang phdp ehuyen md ve tat dinh). Ve thudt todn phdn tieh ta dung cdc thudt todn quen thupc cda eg hpc cPng trinh, nen sai sd Id cd t h i chip nhan duge. Ve phuang phdp giai md ta chpn phugng phdp thich hgp (dai dipn).
Oo dd, cd the ndi dp tin cdy eua gid tri giai md phu thupc ehd yeu vao mirc md eua d i u vdo. ThPng Ihudng d i u vdo cda qud trinh phdn tich la mpt td hgp gdm cdc dai lugng t i t djnh, nglu nhiPn vd md. Op bat dinh cua dai lugng ngdu nhiPn the hipn d gid tri eda dp Ipch chuin (cdn bpc hai cda phugng sai). OP bat djnh cda dai lugng md the hipn g khoang xdc djnh.
Sau ddy, chung tdi de nghi mpt thang gid tri cda P de ddnh gid md'C md eua ddu vdo theo dp tin cpy cua k i t qua giai md nhu sau:
Md-cl: 0.9999 < / " < ! Md'C 2: 0.999 <P< 0.9999 Md'C 3: 0.99 <P< 0.999 Md'C4: 0 . 9 < P < 0 . 9 9 Md'C 5: 0.75 <P<0.9 Mdc 6: 0.5 < / • < 0.75 Md'C 7: P<0.5
Thpt ra ddy chi Id quy ude, song np eP sy tugng ty trong phdn loai cPng Irinh theo dp tin cpy vd quy djnh trong cdc tiPu chuin thiet ke cdng trinh theo dp tin cdy.
Oe giam md'C md cua d i u ra, ta giam dp phdn tdn cda dau vdo. Trudng hgp dau vdo gdm nhilu tham sd, mdi tham sd cd mpt vai trd khdc nhau trong qud trinh phdn tich (dp nhay khde nhau). Oe tdng nhanh dp ehinh xde eda dau ra thi ta giam dp phdn tdn eda cdc tham sd d dp nhgy ldn.
4. THi o y
XPt mpt d i m dgn gian ed chieu ddi L, t i l l dipn hinh chQ' nhpt. D i m ehju tai trpng lpp trung P d giOa nhjp vd tai trpng phdn bd deu theo chieu ddi vdi cudng dd q . Vipc phdn tich md ddi vdi d i m dd duge xPt trong [2], sau ddy la chi xPt mirc md cda dau vdo.
Hinh 2. HSm thudc cda a„sK
O ddy, la chpn d i u ra Id Omax. Trong [2], bieu dd tan suit eua qudng an todn (safety margin) M=oo-am«x dd dugc thill ldp. VI oo dd b i l l ndn ta cd the edn cu' theo M de xPt a^ax hode
TAP CHf KHOA HOC C O N G N G H $ X A Y DUNG Sd06-12/2009
xPt tryc liep bieu dd tan s u i t cda Omax de suy ra hdm thupc cua Omax- Sd" dyng cdc k i t qua trong [2], thyc hipn phPp co [7] de llm hdm thupc Omax, ta nhdn dugc hdm thupc cda Omax nhu trdn hinh 2.
Theo phugng phdp trpng tdm ta gill md cho omax. tpa dp trong tdm cua tam gidc hdm thupc trPn tryc hodnh Omax Id 21,98. Neu ta chpn dp lech cho phPp \a S = ±1,80. thi dp tin cPy eda ket qua giai md Id:
3 42
P = ^ ^ « 0,653.
5,25
Theo thang gid tri eda P. ddu vdo cda bdi todn phdn tich thupc md'C md 6 Id mde md cao. Mudn giam md'C md thi ta phai giam dp phdn tdn cda dgi lugng n g i u nhidn vd dgi lugng md, nghtg Id giim md'C md cda cdc tham sd d i u vdo, hope (vd) tdng dp Ipch cho phPp 5.
5. K i T LUAN
1. o l u vdo cda phdn tich ket c l u Id mpt td hgp eda cdc dgi lugng tat dinh, ngdu nhiPn vd md. Do dd, vipe xde dinh mdc md Id xdc djnh cho ca mpt td hgp. Song khi d i l u chinh thi didu ehinh theo lung thdnh phin. Oe tdng nhanh hode giam nhanh mifc m d thi ta phai xdc djnh dp nhgy (sensitivity) eda cdc tham sd, dd Id bdi todn khdc d n duge nghiPn ed'u riPng.
2. Odnh gid sai sd trong bdi todn phdn tieh md ket d u Id bdi todn phu'c tgp, trong bdi ndy ehi Id nhOng de xuat budc d i u .
3. Cdc ket qua IrPn ddy hodn todn ed the dp dyng cho mpt hp Ihdng bat ky nhu kinh le, sinh thdi, mdi trudng, an ninh,...
4. Vipe phdn logi mdc md trong ede logi bdi todn khde nhgu, ndi chung, Id khdc nhau. Do ydu d u thyc tiPn vd y nghTa cua lung v i n de, thang gid In P cd the thay ddi sao cho phu hgp.
5. Phdn tich md Id ITnh vye rlt cd trien vpng trong phdng vd giam nhp thiPn tgi do biln doi khi hdu.
NgSy nhpn: 29/07/2009.
Tai lipu tham khao
1. Nguypn Vdn Phd, Nguyin Xudn An - Mgt phuong phSp phSn tich md kit eiu, lap ehi Khoa hpe - Cdng nghd Xdy dyng. Bp Xdy dyng. Sd 3 (2008).
2. Nguyin Vdn Php, Nguydn Xudn An - Mpt phuang phSp phSn tich kit du trong tinh tr^ng biin ddi khi hSu. Tgp chi Khoa hpc CPng nghp XPy dung. Trudng Oai hpc Xdy dyng. Sd 4 (2009).
3. Nguypn Vdn Phd, Ld Ngpc Hdng, LP Ngpc Thach, Tran Vdn LiPn - Mdt s6 vin dd cda Ca hge cdng trinh trong tinh trang biin ddi khi hpu. Tuyen tdp Cdng trinh Hpi nghj Cg hpe todn qudc, Ky nipm 30 ndm Vipn Cg hpc vd 30 ndm Tgp chi Cg hpc. Hd Npi, 8-9/4/2009.
4. Bernd Moller, Miehgel Beer Fuzzy Randomness. Uncertainty In Civil Engineering and Computational Mechanics. Springer. 2004.
S TAP CHf KHOA HOC C O N G N G H E X A Y DUNG Sd06-12/2009
5. A.M. laglom, I.M.Igglom Probability and Information. Science Edition. Moscow. 1960 (in Russign).
6. Bui Hung Cudng, NguyPn Dodn Phudc. He md, mang na ran vS ung dung. Nhd xult b i n Khog hpc Ky thupt. Hd npi. 2006.
7. Nguyen Vdn Phd, Nguydn Oinh Xdn, Nguypn Thgc Vu - Vi md hinh giao thoa tmng phSn tich di tin eSy md. Tuyen tdp Hpi nghi Ca hpc VRBD todn qudc i l n thd- 8. Thdi Nguyen, 2006.
TAP CHf KHOA HOC C O N G N G H S XAY DUNG Sd06 • 12/2009