07.1.kth.trang-phamthi

TP CH KHOA HC V CNG NGH, I HC NNG - S 1(30).2009

XY DNG CHNG TRNH TI U HO THEO CH TIU THI GIAN V CHI PH TRN S MNGESTABLISHING AN OPTMIZING PROGRAM BY TIME AND COST STANDARDS FOR NETWORK DIAGRAM Phm Th Trang

Trng i hc Bch khoa, i hc Nng

TM TT Ti u ho theo ch tiu thi gian - chi ph trn s mng l mt trong nhng gii php tng i hu hiu nhm rt ngn thi gian thc hin tng danh mc cng vic hay ton b cng trnh tng ng vi tng chi ph thp nht. Xut pht t vn hn ch v ngun vn u t trong xy dng, tnh cnh tranh khc lit v gi thnh v hiu qu ca vic rt ngn thi gian thi cng sm a cng trnh vo khai thc, nn vic nghin cu thit lp chng trnh tnh ton ti u ho s mng theo ch tiu thi gian vi chi ph tng thm nh nht l ht sc cn thit nhm mang li hiu qu kinh t cao trong vic t chc sn xut xy dng cng trnh. ABSTRACT Establishing an optimizing by time and cost standards for the network diagram is a relatively effective solution to reduce the implementation time for each category of work or the whole project at the lowest cost. Based on the limited building investment, high competion in terms price and effect of the reduced implementation time to put the project into early operation, it is necessary to study and establish an optimizing time and cost standards for the network diagram, in order to bring about high economic effect in organizing and implementing the construction.

1. t vn Nm 2007 Vit Nam gia nhp WTO. Ngun vn FDI tun chy o t vo nc ta em li c hi mi v nhiu thch thc to ln cho s pht trin ca th trng xy dng nc ta trong giai on sp ti. Hn th na, vic m ca th trng s to ra p lc cnh tranh rt cao cho tt c doanh nghip hin ang hot ng trong lnh vc xy dng. Cc doanh nghip c vn u t nc ngoi vi tim lc ti chnh mnh v phong cch qun l hin i s l nhng i th cnh tranh thc s i vi cc doanh nghip trong nc. Do vy i hi ngnh xy dng trong nc cn nng cao nng lc cnh tranh, pht trin ph hp vi tiu chun v thng l Quc t. Mt trong s nhng vn mu cht to nn nng lc cnh tranh ca doanh nghip xy dng chnh l vic rt ngn thi gian thi cng vi chi ph tng thm t nht nhm to hiu qu kinh t cao khi sm a cng trnh vo khai thc s dng. Ngy nay my tnh in t c s dng rt ph bin, cc chng trnh phn mm lin quan n lp k hoch tin , iu chnh v ti u ho k hoch tin c sn kh nhiu, tiu biu c phn mm Microsoft Project vi nhiu tnh nng u vit v48


tin dng nhng ch gii quyt c mt s trong nhng bi ton t ra v ti u ho s mng nh ti u ti nguyn, thi gian, n hn lc. Tuy nhin bi ton ti u ho theo ch tiu thi gian - chi ph trn s mng ang l vn ng quan tm trong nn kinh t th trng c tnh cnh tranh khc lit v gi thnh cng trnh. Vi chng trnh WinQSB gii quyt c bi ton ti u ho theo ch tiu thi gian - chi ph, tuy nhin n cn ti n nhiu mt hn ch, chnh v th bi bo ny cung cp mt m chng trnh tnh ton ti u ho theo ch tiu thi gian - chi ph hon thin hn v gii quyt nhng nhc im ca chng trnh WinQSB. 2. Mc tiu, i tng, phm vi v phng php nghin cu 2.1. Mc tiu nghin cu Thit lp chng trnh ti u ha s mng theo ch tiu thi gian - chi ph nhm gp phn to iu kin t ng ho qu trnh rt ngn thi gian thi cng xy dng. 2.2. i tng v phm vi nghin cu Lnh vc lp k hoch t chc v ch o thi cng cng trnh xy dng. 2.3. Phng php nghin cu Phng php s mng li: l m hnh p k hoch da trn c s l l thuyt th; cng thc ton hc; thut ton tm ng i di nht, l thuyt v lp k hoch ch o sn xut trong cc doanh nghip xy dng. 3. M hnh bi ton ti u ha theo ch tiu thi gian - chi ph trn s mng 3.1. Thit lp cc mi lin h v cc rng buc cho bi ton 3.1.1. iu kin mang tnh cng ngh: t i +t ij -t j 0 Trong : t i : Thi gian thc hin s kin i t j : Thi gian thc hin s kin j t ij: Thi gian thc hin cng vic ij 3.1.2. iu kin rng buc phm vi thay i thi gian ca cc hot ng: t min t ij t Trong : t min : Thi gian ti thiu thc hin cng vic ij t: Thi gian bnh thng thc hin cng vic ij 3.1.3. iu kin rng buc v thi gian hon thnh d n: t n - t 1 Tk Trong :49


t 1 :Thi gian thc hin s kin 1 t n :Thi gian thc hin s kin n Tk:Thi gian d nh hon thnh ton b cng vic 3.1.4. Mi lin h gia thi gian v chi ph: e ij = Trong : e ij : Chi ph b ca cng vic ij (ph ph) C ij : Chi ph thi cng khn trng ca cng vic ij Cijmin: Chi ph thi cng bnh thng ca cng vic ij t ij min: Thi gian thi cng khn trng ca cng vic ij t ij : Thi gian thi cng bnh thng ca cng vic ij. Chi ph b bi u th ci gi m ta phi tr khi r t ngn thi gian thc hin cng vic. 3.1.5. Mi lin h gia thi gian hon thnh ton b cng trnh vi thi gian thc hin tng danh mc cng vic: T G = max t ij 3.2. Xy dng chng trnh gii m hnh bi ton ti u theo ch tiu thi gian - chi ph trn s mng 3.2.1. Phn tch m hnh v phng php gii m hnh Bi ton c t ra l cn tm phng n rt ng thi hn thc hin ton b n cc cng vic i hi chi ph gia tng nh nht (rt ngn thi gian thi cng ngn nht vi gi thnh thp nht c th). Phng php thc hin vic rt ngn thi gian: Bc 1: Lp s CPM tm ng gng v cc cng vic trn ng gng. Bc 2: Tnh chi ph cho vic rt ngn ca tng cng vic, tnh chi ph b. Bc 3: Chn cng vic trn ng gng c chi ph b nh nht v rt ngn ti a cng vic ny nu c th hoc rt ngn thi gian hon thnh cng vic ny n mc tiu nh. Bc 4: Kim tra li xem ng gng m ta rt ngn c cn l ng gng khng, nu n vn l ng gng th quay v b c 3 v c lm nh vy cho n khi t mc tiu rt ngn cho trc.C ij C ij min t ij t ij min

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3.2.2. Xy dng thut ton ti u ha theo ch tiu thi gian chi ph trn s mng S i khi tng qutNhp 4 ma trn MTT, MTTmin, MTC ng gng Dijkstra Gn ma trn B Tnh chi ph b Gn Mng E GetVTE Ti uFalse

S khi thut ton ti uBEGIN

v=1False

True

Tdck ) or (test = True) and (d[t] = Tmax)

END

4. Th nghim chng trnh trn s liu thc t: Vn dng chng trnh rt ngn thi gian thi cng cho cng tc phn ngm cng trnh: Nh iu hnh in lc Nng Bng tng hp cc thng s u v cho bi ton Thi gian thi cng (ngy) Bnh thng 1 2 4 5 7 12 Khn trng 1 1 2 3 4 6 Chi ph thi cng (ng) Bnh thng 250.000 784.858 3.494.307 2.354.572 Khn trng 250.000 902.587 3.526.804 2.637.121

TT

Tn cng vic

K Hiu

1 Chun b 2 o t th cng t 1 3 o t bng c gi 4 Sa HM bng th cng 5 b tng lt mng 6 Lp t vn khun mng

1-2 2-3 3-4 4-5 5-6

9.952.642 10.201.145 4.445.639 4.745.533

7-8

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7 Lp t ct thp mng 8 b tng mng 9 Tho vn khun mng 10 Lp t t 1 11 Cng tc hm v sinh 12 Xy ging, dm mng 13 Lp t t 2 14 B tng dm,ging mng 15 p t tn nn nh

9-10 11-12 13-14 15-16 17-18 19-20 16-21 21-22 22-23

15 12 6 9 5 5 8 5 5

8 6 3 5 3 3 4 3 3

73.447.737 73.888.864 76.395.608 77.735.205 809.737 881.447

9.413.106 10.668.187 8.148.728 5.373.774 8.442.822 8.418.924 5.537.434 9.709.245

36.296.794 37.208.957 3.541.973 3.967.010

Kt qu tnh ton vi thi gian rt ngn l 15 ngy (theo yu cu ca ch u t)

Nh vy vi thi gian yu cu rt ngn t ra l 15 ngy so th chi ph tng thm l 1.375.120 ng. Chi ph hon thnh cc cng tc thuc phn ngm trc k h i r t ngn l:52


243.152.297 ng. Chi ph hon thnh phn ngm vi thi gian rt ngn 15 ngy l: 244.527.417 ng. Nh vy so vi khon c thng khi rt ngn tng tin theo qui nh trong hp ng k kt l 0,5% cho hn 10 ngy vt k hoch th khon chi ph tng thm ny l rt b so vi khon c hng do rt ngn tin . Do vy trong thc t bi ton ti u trn l rt c ngha . Vic rt ngn thi gian thi cng cng trnh sm a cng trnh vo s dng c ngha thc tin ln. N s gp phn lm gim hin tng ng vn thi cng cng trnh, to thun li cng trnh sm pht huy cng nng ca n, lm t ng hiu qu kinh doanh ca ch u t. 5. Kt lun v kin ngh Vi chng trnh tnh ton t iu ho s mng WinQSB, vic rt ngn thi gian lm thay i v xut hin nhiu ng gng mi, qu trnh ti u ho s lm cho cc cng vic dn tr thnh l nhng cng vic gng, th nhng s lng cc cng vic gng trong mt d n kh ln vt qu 10% thc s l mt vn bt cp m thc t trong cng tc t chc thc hin d n, cng trnh rt kh c th thc hin c do thi gian d tr qu t nn vi c thc hin d n l km an ton v cn mang nng tnh cht l thuyt. Vi chng trnh ti u ho s mng theo ch tiu thi gian - chi ph khng lm xut hin thm ng gng mi do vy t lm nh hng n thi gian d tr ca ton b d n, vic thc hin d n thc s bm st v mang tnh cht thc t nhiu hn, d thc hin hn v kt qu tnh ton ti u hn v mt chi ph. Nh vy vi cc thng s u vo ca mt d n l nh nhau, qua qu trnh phn tch v x l s liu tnh ton, hai ch ng trnh WinQSB v chng trnh Ti u ho s mng theo ch tiu thi gian - chi ph cho ra kt qu tnh ton v thi gian rt ngn ti a v ti thiu l nh nhau. Tuy nhin chi ph gia tng cho vic rt ngn l khc nhau v c s chnh lch nhau v mt gi tr, s d c nh vy l do qu trnh ti u ho c thc hin theo hai hng khc nhau v chng trnh ti u ho theo ch tiu thi gian - chi ph mang tnh th t hn, chnh l nt thnh cng ca chng c trnh. Do vy vic xy dng chng trnh tnh ton ti u ho s mng theo ch tiu thi gian - chi ph gp phn quan trng vo cng tc t chc thc hin d n thi cng cng trnh, gii quyt tt bi ton ti u v thi gian v chi ph, to th mnh cnh tranh trong tranh thu, m bo hot ng kinh doanh c li cho doanh nghip xy dng. Vn thi gian v gi thnh trong xy dng l mt vn rt quan trng, gia thi gian hon thnh thi hn xy dng cng trnh v gi thnh ton b c mi quan h cht ch. Thi cng ng thi hn vi chi ph nh nht s mang li nhng kt qu to ln v kinh t v chnh tr. V vy thi cng nhanh nht vi gi thnh r nht l mc tiu ca cc hot ng u thu trong xy dng. y l mt vn phc tp v hp dn ang i hi ngi lm cng tc t chc v iu khin xy dng quan tm n.53


TI LIU THAM KHO [1] Barry Benator and Albert Thumann (2003), Project Management and Leadership Skills for Engineering and Construction Projects, The Fairmont Press, the United States of America. [2] Flavio Cozzi (2008), Industrial Project Management: Planning, Design, and Construction, Stefano Tonchia University of Udine. [3] Keith Potts (2008), Construction Cost Management: Learning from case studies, by Taylor & Francis Group, in the USA and Canada. [4] Murray B. Woolf (2007), Faster Construction Projects with CPM Scheduling, The McGraw-Hill Companies, the United States of America. [5] Jonathan F. Hutchings (2004), Project Scheduling Handbook, Marcel Dekker Inc, the United States of America. [6] Thomas Euher (2003), Programming and scheduling techniques, Unsw Press, the United States of America.

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07.1.kth.trang-phamthi

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