«'ri-^^ Qt'-^
"Xac dinh dang du'o'ng phu hap mo ta chi phi tich luy cua nha thau"
Ngay nhan bai: 15/8/2014 Ngay sCra bai: 22/8/2014 Ngay chap nhan dang: 5/9/2014
Phan lu'dng Thuy, Le Hoai Long
T O M T A T :
Quan ly chi phi luon la mot trong nhCing van de quan tam hang dau cua cac doanh nghiep dii vdi bat ky quy m o nao. Viec c^n doi dong tien thu-chi la mot trong nhflng yeu to thiet yeu de dam bSo sU ton tai va phat t n e n ciia mpt doanh nghiep. Bai bao dUOc thuc hien n h i m dUa ra dang mo ta cho dUdng cong chi phi tich luy ciia mot dU an. Dfl lieu difcTc thu thap tii hOn ba miltJi dii an tii mot cong ty xay diing. Viec m o phong dang dudng cong diipc tien hanh. Sau ciing, ket qua p h i n tich chi ra rang dang diidng bac ba mo ta thich hop nhat vdi bo dfl lieu ducfc chon Tfl khoa: Dilclng cong S, Chi phi, Tich luy
ABSTRACT
Cost management is always one of top concerns of any business no matter what size. The balance of revenue-expenditure cash flow is one of the essential elements to ensure the survival and development of business. This paper was undertaken to give shape to the curve describing the cumulative cost of a project.
Data was collected from more than thirty projects from a construction company. The curve simulation was conducted.
Finally, the analysis results showed that cubic description best fits the data.
Keyword: S-Curve, Cost, Accumulate
KS Phan Tiicrng Thuy
Hoc vien cao hoc nganh Cong nghe va Quan ly Xay diing, khoa 2011
Triidng Dai hoc Bach Khoa, Dai hgc Quoc gia Tp. Ho Chi Minh D i d o n g 0915 724 082
Email ihuy,[email protected] TS Le Hoai Long
Pho Chii nhiem Bo mon Thi cong va Quan ly Xay ddng - Khoa Ky thuat Xay diing
Tni6ng Dai hoc Bach Khoa, Dai hoc Quoc gia Tp. Ho Chi Minh Di dpng: 0977 596 268
Email: lehoailong@hcmut,edu.vn
t . Gidi thieu
Tien mat la m p t trong nhQng n g u 6 n life quan trong nhat cila mj cong ty xay diTng, nhieu cong ty da phia sin vi thieu tinh thanh k l ^ trong viec ho trp cac cong viec hang ngay. Viec khong trS dUOc nOtm nen cong nghiep hien nay r a t d e xay ra hon b a o g i 6 h e t (KaltavSPnc 1993).
U6c tinti dong tien la rat thiet yeu cho sil t o n tai cua bat k>( niiJ thi nao trong tat ca cac giai cloan cua dU an. IVlpt each 1^' tUdng, viSc Uflctin nay c6 the dua tren chUOng trinh cua dUan va theo bang tien liiOngJol (Allsop, 1980). Da so cac mo hinh Ude tinh dong tien dUa tren di/£(ng««
S, dai dien cho cac gia t n cong viec tfch luy, sfl dung dOliSutCl cacdifi xay dung da hoan thanh (BIyth va Kaka, 2006).
Oaong cong S du'pc sfl dung rong rai de kiem soat d f l an quadcgi doan thflc thi. Phu'ang phap nay rat co gia tri cho q u i n ly dflSntrongvii bao cao tinh trang hien tai ciia d f l an va tien doan ve tflong lai Ngoa*
phuong phap nay con dUpc sfl dung de lap ke hoach cho viec baocfeti gia tn thuc te, gia t n dat duoc va gia tri ke hoach cho cac hoat dpng^Jii nhau ciia dfl an (Miskawi, 1989).
Tren nen tang do, nghien cflu dflpc thflc hien v6i mong muonfi dflng dupc du6ng cong thich h p p m o ta cho chi p h i tich luy ciladijl xay dflng. Ket qua t h u du'oc cho thay dang dUdng cong don bienl^
(Cubic) la dang duang mo ta thich hpp hon c3. DCf lieu dung de phSnli t t r o n g bai bao dupc lay t f l mot cong t y xay d u n g (Cong ty A).
C o n g t y A l a nha thau chuyen ve thi cong xay d u n g , von dieu lets 500 ty, tong nguon von tren 4,000 ty d o n g . Cong ty A chuyen tH}*
cac d f l a n chung cU, nha cao tang (ca phan ngSm, phan tho, hoSnP pham VI thi cong tr^i dai t f l nam ra b k .
Nghien cflu dflPc tten hanh dfla tren cong cu Curve EstimatiQnt phan mem SPSS, he so xac dinh R2 dflpc sfl d u n g d ^ danh gii !#(
t h u dflac. Gan 60% trflong hop cho thay dfldng cong bac 3 {CubK!
Ida chon thich hpp de m o ta chi p h i tich luy theo t h d i gian ciiadi/ai»
dflng. Tfl do, xay d u n g nen d u d n g cong S mo ta thich hpp xu liL/ftij' tra (chl phi) theo van hanh cua cong ty A noi rieng, va ap dung clw' cong ty co quy mo / pham vi hoat d p n g t u a n g t f l noi chung.
2.Tong quan
Barraza (2000) da phat trien mo hinh d f l d n g cong S xacsualE Curve). SS-curve cung cap phan phoi xac sual cho cac g i i tri chip*' t h d i gian ky vong. Quan ly viec thflc hien d f l a n dflpc thflc hien bSng"^
so sanh gia t n chi phi va t h d i gian c6 khS nang cao nhat, thu dU^ctilll phPi xac suat t u o n g flng cho tien trinh thuc t g , V chi phi tich K^*
lieu thuc su cua d p an.
I Trong bai bao cua m i n h , Cheng va cac -• - u { 2 0 n ) d a t W rang: cac phuang phap truyen t h o n g ve ,, , ^.^j ^ j ^^ j,|j[|j
fifl BHIIiEPSl 10.2014
dCing m p t m o hinh d o n nhat cho toan the dif in. Tuy nhi^n, m d t dif in xay difng, bao gdm nhieu giai doan khac nhau, se xufit hi^n c i c chi phf khac nhau, do do khong the nam b3t dflpc m^t each chinh xac chi bSng mot m o hinh dOn nh^t.
8anki v i Esmaeli (2009) cho rSng thdi gian . d i n h cho fldc doan ddng t i ^ n trfldc khi dau thau m p t c i c h chi tiet la rat gidi han. Do do, nha th3u can co mpt ky t h u i t nhanh va dPn gian cho phep ho fldc doan dong tien v6i 66 chinh x i c thich hpp. C i c tac g i i da thflc hien mpt nghien cflu t r o n g pham vi Iran, t h u thSp diJt lieu Ijch s f l t f l 20 d u i n da h o i n thanh, md hinh hoa S-Curve; va d l ra cong thflc de fldc d o i n dfldng cong S.
Dflong (2010) da thflc hi^n nghien cflu ve dfldng cong 5 fldc t i n h chi p h i cho c i c d f l i n dfldng bd t i n h Binh Dinh, Duong da t i ^ p can trflc t i l p sd li&u t f l Ban Q u i n Ly cong trinh giao thdng, t h u dflpc 81 b p sd l i l u , sau d 6 loc sd lieu Iheo t i l u c h u I n d o Jarrah (2007) d e xuat t l i u dflpc 63 bo so lieu. Duong l^i tiep tuc kiem tra
^d l i | u vdi c i c h i m sd do nhiSu t i c g i i d ^ nghi i h f l ; IVliskawi (1989), Bromilow (1974). Dflong :6n d l xucit v i l e h i f u chinh h i m da thde bac ittdn cua Bromilow.Tfl do t i m duac phflong trinh ilfldng cong S d y d o i n ddng tien chi t r i ciia (•"hu Dau Tfl cho nha thau trong sudt d f l i n . Tuy i^hiln, n g h i l n cflu ciia Du'dng dua tr6n gdc do ifldng cong T h u ' [chi t r i cOa Chu dau tfl), con
nghien cilu nhy duac thuc h i l n dira t r i n goc d p dfldng c o n g " C h i ° ( c h i p h i n h i thau p h i i bdra).
3. PhiTtfng phcip n g h i l n cihi 3.1. Thu thdp dOlieu
DCr lieu dfldc t h u t h i p t f l h i t h d n g phan m i m quan ly chuyen d u n g cua Cdng t y A, Cac d f l l i l u dupe trfch xuat theo tflng t h i n g . Do tinh chat thifc te v i n hanh, he thdng p h i n mem q u i n ly cda cdng t y tien h i n h hoat dpng chinh thflc la tir t h i n g 01/2011. Do do, d ^ e6 bp sd lieu day dfl t i ^ t h d l gian b i t d i u , c i c d f l i n dflpc chpn lam cp sd d f l lieu cd sd lupng khdng q u i Idn. L/dc tinh sd Ifldng v i o k h o i n g 35-40 d f l i n . D f l lieu dupc xuat t f l mpt module chuyen b i l t trong h i thdng q u i n ly d f l lieu. Trong moi Iflpt truy cap, d f l lieu chl dfldc trich xuat trong tifng t h i n g ddi vdi ti/ng d f l i n . Theo do, vdi 40 d u an dfldc chpn v i o t h d i diem ban d i u va trung binh 30 t h i n g / d f l i n = > can truy cap va thflc thi vi&c x u l t d f l lieu k h o i n g 1200 l l n .
Cudi cung, 36 bo d f l lieu tflong flng vdi 36 d f l an dflpc chon l i m ca sd d f l lieu dSu vao cho md hinh nghi&n cflu. (Ten c i c dif i n dflpc ma hda theo dang Proj.[S6 t h f l t f l trong h i thong chung cCia cdng ty])
3.2. Cdng cu nghien ciAi
P h i n m i m SPSS va Microsoft Excel dflpc sfl dung de thdng ke d f l l i l u v i fldc t i n h dang dfldng cong p h i i hpp, can cfl tren Ijy' thuyet hoi quy don bien. Ket qua duoc k i i m djnh b i n g g i i t n R2 (He sd x i c djnh - Coefficient of
Determination).
Gia trj R2 ( H I sd x i c djnh - Coefficient of Determination) l i dau h i l u cho thay mdi l i l n he gifla bien dde lap v i bien phu t h u d c Gia trj R2 cang cao eho thay md hinh (dudng cong) sfl dung cd k h i nang g i i i thich t o t k h i c b i l t ve b i l n phu thudc gifla c i c bi^n quan s i t .
4 . mid p h 6 n g & K^t q u i
Vdi mdi d f l i n , chi p h i dUdc cdng d d n theo tflng t h i n g d i cd dUdc g i i t n chi p h i tich luy.
Sau do quy ddi t h i n h t l le p h i n tram chi phf tich luy tUdng ung tai c i c mdc t h d i gian t f l 10-90%
ei^a d f l i n . Hinh 1 l i vf dg ve ket q u i sau quy doi v ^ c i c doan t h d i gian cOa m o t dif i n
Chi phf tfch IOy theo t h a i gian
Kinh 1.Oil phf tidi luy tai cac moc thdi gian cua dilanPrq. 68 Md phdng Curve-Estimation (SPSS) dflpc sfl dung de khai q u i t hda dang dUdng cong theo c i e bp d f l l i l u d i u vao.Trong bai b i o nay, bdn dang dfldng cong ddn g i i n dfldc chpn d u n g de kiem tra la:
B i n g I . K e t q u i m o phdng Curve-Estimation flng vdi 36 bd d f l lieu v i 4 dang dfldng cong
PrajUt 30 51 68 77 79 S2 83 84 85 86 87 88 89 90 91 91 196 ' 9 7
^98 IDS 108 114 ,115
U i w a r R2 0 885 0 789 0.923 0.969 0.969 0.786 0.835 0.845 0 9 6 8 0 765 0.901 0.689 0 863 0.566 0.884 0.870 0 87S 0 932 0.661 0 941 0 803 0 726 a 7 6 2
Ad|.R2 0,870 0 763 0 913 a 9 6 5 0.965 0 J 5 9 0.870 0.826 0 964 0.736 0 889 0 6 5 0 0.846 0.512 0.870 0 853 0.860 0.923 0 618 0 933 0 778 0A92 0.73J
F 61,350 30000 9 5 J 2 2 251 161 250 934
2 9 3 5 9 61.143 43 754 239 019 26.070 7 3 1 2 4 17 746 50.308 10.435 61.237 53,396 5 6 1 9 9 109.480 15.577 126.463 32 580 21,206 25JS7
Quadratk R2 0 940 0 9 9 3 0.929 0 9 6 9 0.970 0.961 0 897 0.9S4 0.983 0.974 0.962 0.961 0 990 0 799 0 9 9 9 0 9 9 2 0 992 0 972 0 857 0 952 0.957 0.975 0,977
A d j . R 2 0.923 0 9 9 0 O.909 0 9 6 1 0.962 0 950 0.867 0.979 0.978 0.967 0,951 0.950 0 987 0 741 0 9 9 9 O.990 0.990 0.964 0 8 1 6 0 939 0.945 0.968 0.971
F 54 753 465.161 46.144 111.161 1I3.BS4 86.153 30,345 212 064 199101 132,614 87 786 B6 710 356.435 13906 3660 000 454.067 434,347 121 032 20.994 69,721 77 698 138.221 151.246
Cubic R2 0 971 0 995 0.983 0 997 0 976 0.962 0-973 0.9SS 0995 0 992 0.986 0 997 0 991 0 902 0 9 9 9 0 9 9 4 0 9 9 3 0 9 7 6 0,857 0 986 0.961 0.996 0-990
Adj.RZ 0,955 0 992 0 9 7 5 0 996 0.963 0 9 4 2 0 9 5 9 0.977 0.992 0.989 0.979 0.996 0.987 0.853 0.999 0.990 0.989 0 9 6 4 0 786 0 979 0.942 0,994 0.98S
F 66,100 381,316 117,133 788159 80 024 49,997 71070 128,511 395.293 264183 139671 702.738 227.984 18 382 2091000 308 221 278 646 8 1 4 1 2 12009 138.841 49,613 474.818 193.226
S R2 0.924 0 9 9 3 0,867 0.817 0 889 0 949 0,907 0 988 0 921 0 990 0 980 0 959 0 991 0 874 0 990 0 975 0.993 0 698 0 8 6 0 0.963 0 951 0.990 0.991
A d j . l U 0 9 1 5 0.992 0,851 0 794 0,875 0 9 4 3 0.B95 0 987 0 911 0 989 0 977 0 954 0 990 0 858 0 939 D971 0 992 0.660 0.843 0 9 5 9 0 9 4 5 a 9 8 9 0 990
F 97 352 1154.000
52.232 35 645 63.779 148,813 77,861 67( .058 92.699 783,999 385.295 188807 931372 5 5 3 0 0 776401 307 291 1150000 18.456 49.184 210 298 155.878 801.708 877-274
Best fit curve M a x R Z
0 956 0 992 0 975 0 996 0 965 0.950 0.959 0,987 0.992 0 9 8 9 0 979 0 996 0 990 0.858 0.999 0 9 9 0 0 992 0 9 6 4 0.843 0,979 0.945 0 9 9 4 0 9 9 0
Cubic Cubic Cubic Linear Quad Cubic 5 Cubic Cubic Cubic Cubic S 5 Quad Quad S Quad
S Cubic Quad Cubic S
69
B i n g 1. Ket q u i md phdng Curve-Estimatio
Prague 127 129 131 136 138 139 141 142 143 145 146 153 169
R2 0 9O1
0 9 3 0 0 786 0 ^ 3 9 0 9 6 0 0 910 0 ^ 9 4 0 726 0 736 0 4 4 4 0.946 0936
0.921 07S9 0 819 0 955 0 899 0 « 5 0 * 9 1 0.703 0 3 7 4 0,939 0,928
41745 190.449 80,698 I S 1 I S 21146 22.288 6 3 8 8 139,870 116.935
n flng vdi 36 bd d f l lieu va 4 dang dfldng cong (tt) OuMlratii:
0993 0.983 0.963 0.963 0.978 0 9 6 7 0 774 0 9 6 3 0.936
0 9 8 4
0.991 0.978 0 953 0.953 0971 0 958 0 710 0952 0,918
F
280923
524069 202.503 9 Z I 5 8 9 1 7 3 4 153J01 102^27 11010 91.136 51.510
Cubic R2 0 981 0.990 0993 0.985 0994 0.998 0.977 0988 0 990 0 9 7 7 0 943 0.969 0 990
Adl.R2 0971 0.985 0 990 0 9 7 7 0,991 0 9 9 7 0966 0.981
F 100.704 201J22 285.587 127.861 319 979 963.923 84978 159 662 0.984 191 096 0.966 85-650 0.914
0.953 0985
32.844 62155 203,420
RZ 0.916 0 9 4 8 0 984 0 9 7 6 0 992 0.982 0.915 0 9 6 8 0.983 0 969 0.904 0 986 0 974
S A d i . R 2 0.906 0 9 4 1 0.982 0 973 0.991 0 9 8 0 0.904 0 9 6 4 0,981 0 965 0,892 0 984 0.971
F 87.S68 145.696 494106 321 177 1001 000 43S.981 85 953 241342 454 7S6 248.804 75 685 561,044 297.407
Best fit c u r w Uaum
0971 0.985 0 9 9 0 0.979 0 991 0 997 0 966 0.981 0.9&4 0 9 6 6 0.914 0 9 8 4 0.985
Tm Cubic Cubic CubK Quad Quad. Q * * " ' Cubic CuUc Cubic • Cubic •" cuble"^
s Cubic
-Linear. Y = b O + (b1 " t ) . - Quadratic. Y = bO + (bl • t) + (b2 • t').
-Cubic.Y = bO + ( b l * t ) + { b 2 " t ' ) + ( b 3 * t ' ) . - S-Curve. Y = e f " ' "-""i hoac ln(Y) = bO -»- ( b l / t ) .
Ket q u i dflpe danh g i i dfla tren he sd x i c dinh R', h^ sd x i e djnh h i l u c'htnh Adj.R', dUdc trinh bay trong B i n g 1
Nhan x l t
Theo dd, vdi 36 dfl i n ; k i t q u i dang dfldng phCihPpnhflsau:
-Linear: 1 d y i n -Quadratic: 7 d u i n
• C u b i c 2 1 d f l i n -S-curve; 7 d f l i n Mflt v i i trudng hop x i y ra k h i c thfldng, c h i n g han nhfl Proj.98, h i u h i t g i i tri R2 cda c i 4 loai dudng cong d i u thap so vdi cae trudng hpp tai c i e d f l an cdn lai; nguyen n h i n chinh la do tde dd chi phi dflpc sfl dung nhanh hon h i n so vdi c i c trfldng hop khie (Theo t i p d f l lieu ghi n h i n , d f l i n Proj.98 tai thdi diem 40% thdi gian da chi t r i hem 90% tdng luy ke chi phi). Dieu n i y l i m eho c i c md hinh deu khd g i i i thfch dupc sy bien t h i l n cua b i l n ehi p h i tfch luy theo thdi gian. Tinh hudng tUdng t f l dien ra ddi vdi dfl an Proj. 90 (dat tren 80% chi phi v i o thdi diem 40%
thdi gian)
V l mat t d n g q u i t , dang dfldng Cubic cd mfle dd b i l n t h i l n R^ dn djnh nhat (tfl 0.857- 0.999); bien thien bi^n do rpng nhat l i dang Linear (0.444-0.969). Hai dang dfldng cdn lai i i n lUOt l i Quadratic (0.774-0.999), S-curve (0.698- 0.993)
V i y Ifla chpn dang dfldng b i c 3 (Cubic): Y = bO + (bl • t) -1- (b2 • t2) + (b3 • t3) de md ta chi phf tfch lijy eda c i c d u i n xay dflng eua cdng ty A. Ddng thdi, cung Iflu y r i n g , vdi c i c d U i n co g i i t n R2 max khdng thudc dang dfldng Cubic, g i i tri R2 tuong flng cua dudng Cubic cung ed g i i tri rat cao, n i n v i l e Ifla chpn dfldng Cubic l i m dudng dai d i | n m d t i chung cho bd d f l lieu l i tflOng ddi phu hpp.
5 . K ^ t l u a n
Tif b d dCf l i l u 36 dfl i n cua Cdng Ty X i y DUng A, nghien cflu da x i c dinh dang dfldng cong bac 3 (Cubic) lam dang dfldng m d t i cho cho p h i t i c h luy cda mot dfl an xSy dflng.
Ket q u i md phdng dfldng cong cho t h i y vdi dang dfldng Cubic, g i i trj R2 bien dpng t f l 0.857 - 0.999, cho thay k h i n i n g g i i i thich sfl b i l n t h i l n cua t l le chi p h i tfch luy theo t h d i gian tUdng ddi rat manh, giiip dfl d o i n dflpc t r i n 85% phan tram ehi phf tich luy theo c i c mdc thdi gian tuang flng trong dfl i n .
N g h i l n cflu van cdn han che ve n h i l u m i t : do ehi x u i t p h i t t f l nhu cau thflc te cda ndi tai cdng ty, nen d f l l i l u chua bao q u i t duoc trong nhieu trudng hop khic. Ddng thdi, vdi ngay trong pham vi cdng ty A, bd dfl l i l u 36 d f l i n van cdn rat it de cd t h i dUa ra sif k h i i q u i t hda tuong ddi chfnh x i c .
Tuy n h i l n , nghien cflu l i tien d l cho c i c bflde p h i t trien v l sau: khi c i c bd d f l l i l u dfldc bd sung n g i y c i n g nhieu; cdng vdi v i l e ket hpp vdi ddng t i l n t h u (dudng cong doanh t h u tich luy), sfl k i t hop cfla hai dfldng cong thu-chi se ddng vai tro quan trpng trong v i l e x i c djnh so bd g i i tri thanh k h o i n can thiet tai c i c mdc thdi gian ciia d f l an, gop p h i n x i y dflng n i n chien Iflpc kinh te-tai chfnh can t h i l t cho cdng t y A ndi rieng, v i cae doanh nghiep xay dUng ndi chung.
Ngoai ra t f l ket q u i p h i n tich d tren cho t h i y c i c y l u t d dac trflng khi thflc h i l n d f l i n cung cd anh hudng d i n dang cua dfldng cong va d d phu hpp ciia dang dfldng cong. Cie y^u t d nay cd the la i p luc tien d d y l u cau, hinh thflc hop ddng (trpn gdi, theo don gia), hay vi t r i cCia d y i n . Nghien cflu tiep theo se cd g i n g xac djnh hinh dang d u d n g (phflong trinh dfldng cong) khi tich hop mdt sd y l u t d d i e triftig d f l i n v i o md phdng.
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