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Social and Behavioral Sciences
Procedia - Social and Behavioral Sciences 96 (2013) 785 - 789
13th COTA International Conference of Transportation Professionals (CICTP 2013)
Life-cycle Cost Analysis (LCCA) on Steel Bridge Pavement
Structural Composition
Dejia Zhanga, Fen Yeb*, Jingfen Yuanc
aTongji University, 4800 Cao An Highway, Shanghai P.R.and 201804, China bTongji University, 4800 Cao An Highway, Shanghai P.R.and201804, China (Corresponding author) cOutotec Shanghai Co..Ltd., 555 Loushanguan Road, Shanghai P.R. and200051,China
Abstract
In this paper, double-layer SMA structure a GA+ SMA EA+SMA are the main study object, and the net present value analysis is chosen, obtaining the life cycle cost net present value(NPV) of three pavement structural composition by determining cost structure, life cycle and discount rate. The results show that cost performance of double-layer SMA pavement structure is the best and the life-cycle cost of EA+SMA pavement structure is highest. The study can provide a reference for the selection of steel bridge deck pavement structure composition types.
© 2013The Authors.Published byElsevier Ltd.
Selectionand peer-reviewunderresponsibility of ChineseOverseas TransportationAssociation(COTA). Keywords:Steel bridge pavement; Life-cycle cost; NPV analysis; Structure combination; Rate of discount
1. Introduction
Bridge deck pavement act on the orthotropic steel deck plate directly, the status of stress and strain are both complex. Pavement structure is susceptible to damage under external environment and overload etc. Almost the entire steel bridge deck pavement appeared the disease of translation and rut diseases. Therefore, the construction of steel bridge pavement not only considers the current interest, but also pay attention to the life cycle cost.
2. NPV Analysis Method
NPV is equal to the present value of all future free cash flows less the investment's initial outlay. It measures the net value of a project in today's dollars,the net present value calculation model is shown in formula 1.
* Corresponding author. Tel.: 13774207317; E-mail address: zhang.sky@163.com
1877-0428 © 2013 The Authors. Published by Elsevier Ltd.
Selection and peer-review under responsibility of Chinese Overseas Transportation Association (COTA). doi: 10.1016/j.sbspro.2013.08.089
NPV = IC + Y-1t[MC+IC + FRC + UC] + —1-DC--—S (1)
Ù (1 + i)k (1 + i)n (1 + ) In the Eq: NPV—net present value; IC—initial construction cost; MC—maintenance costs;IC—test expense;FRC—big maintenance costs;UC—user cost; DC— demolition cost; S—salvage value; K—time domain; i— discount rate.
3. Life Cycle and Discount Rate
Life cycle of steel bridge deck pavement is often can not reach the designed working life, taking 20 years as life cycle in the consideration of actual use situation of steel bridge deck pavement.Standard discount rate is decided by interest rate and inflation rate, discount rate (I)= (interest rate - inflation rate)/(1 + the inflation rate). The relevant studies have shown that discount rate is between 3% and 5% usually. Selecting 5 as the discount rate of this paper.
4. Agency Cost Net Present Value
4.1. Initial Construction Cost
Initial construction cost is the unit price of pavement structure project. As shown in Table 1.
Tab.1 Initial construction cost of steel bridge pavements(material cost)
Pavement plan
Layer of structure
Cost (yuan/m2) Total cost (yuan/m2)
Double-layer SMA
SMA-13 (4cm SBR (0.3~0.5kg/m2) SMA-10 (4cm
Epoxy bonding layer (0.8~1.2kg/m2) zinc-rich epoxy primer Floor processing
83.1 80 80 50
SMA-13 (4cm SBR (0.3~0.5kg/m2) GA-10+SMA-13 GA-10 (3cm
Epoxy bonding layer (0.8~1.2kg/m2) zinc-rich epoxy primer Floor processing
240 80 80 50
EA-10+SMA-13
SMA-13 (4cm SBR (0.3~0.5kg/m2) EA-10 (2.5cm
Epoxy bonding layer (0.8~1.2kg/m2) zinc-rich epoxy primer Floor processing
250 80 80 50
4.2. Routine Test
Tests cost is relation to the construction quality, pavement structure, traffic load and environment.The pavement should be tested each 1 year according to the <city bridge maintenance technical specifications> (CJJ -2003), and the pavement structure need to be tested 19 times in life cycle. Tests cost of pavement structure is the same because of uniform pavement top layer.Assume that the tests cost is 0.20% of Plan 1 initial investment cost.
4.3. Routine Maintenance
Pavement should be maintained each 1 year, and can avoid the maintenance if it has a heavy repair in one year,so the maintenance times of pavement structure are different: Plan 1 is 16 times, Plan 2 is 17 times, Plan 3 is 17 times. Assume that the maintenance cost is 0.10% of Plan 1 initial investment cost.
4.4. Heavy Repair
Pavement need to has a heavy repair every 6~8 years according to the experience of experience of application of pavement structure. Assume that the heavy repair cost of pavement take up 20% of their initial investments. Cost and frequency of heavy repair are shown in Table 2.
Tab.2 Cost and frequency of heavy repair
Plan 1 2 3
Frequency(years) 6 7 8
Times 3 2 2
Cost 20% 20% 20%
4.5. Demolition Cost and Salvage Value.
Pavement structure should be demolished when it reach to the working life, demolition cost is 10% of the initial investment. By reason of the cyclic utilization, the salvage value of double-layer SMA structure takes up 3% of initial investment, and others take up 1%.
4.6. Agency Cost Analysis
Above all, agency cost net present value of pavement structures can be get by the calculation model formula (1), and the results are shown in Table 3.
Tab.3 Agency cost NPV of steel bridge pavements
Cost form Each event cost (yuan/m2) Net present value (yuan/m2)
Planl Plan2 Plan3 Plan1 Plan2 Plan3
Initial construction cost 382.2 539.1 549.1 382.2 539.1 549.1
Test 0.76 0.76 0.76 9.42 9.48 9.48
Maintenance 0.38 0.38 0.38 4.04 4.26 4.26
Heavy repair. 76.44 107.82 109.8 134.66 141.06 142.04
Demolition cost 38.2 53.91 54.9 14.66 21.78 23.48
Salvage value 11.46 5.39 5.49 4.4 2.18 2.35
Total - - - 549.38 717.86 720.71
5. User Cost Net Present Value
5.1. User Costs
User costs are made up of vehicle operating costs, delay costs, costs of traffic accidents and uncomfortable running.Calculation model are shown in formula 2,3,4
1) date delay cost: DDC = (L--L-)x ADTxNxW (2):
2) vehicle operating cost: VOC = (— L) x ADTxNxr (3)
3) traffic accidents cost: AC = LxADTxNx (Aa-An )x Ca (4)
In the Eq:L—road length that is being affected;Sa—vehicle speed during the period of bridge aintenance;Sn— normal vehicle speed;ADT—average traffic;N—maintenance days;W—driver per hour time value;R—vehicle weighted average cost;Aa—the accident rate during maintenance;An—normal accident incidence;Ca—every accident cost
5.2. User Cost Parameters
User cost parameters of pavement structures are shown in Table 4.
Tab.4 User cost parameters of steel bridge pavements
User cost parameters Plan1 Plan2 Plan3
Heavy repair (d/time) 7 10 35
Test (d/time) 2
Maintenance (d/time) 5
Road length that is being affected (mile) 2
Vehicle speed during the period of bridge maintenance (mile/h) 20
Normal vehicle speed (mile/h) 45
Average traffic (truck/d) 3200
Driver per hour time value ( dollar/h ) 6.25
Yehicle weighted average cost; (dollar/h) 8
Accident rate during maintenance (truck/mile) 2.2/106
Normal accident incidence (truck/mile) 1.9/106
Every accident cost (dollar/time) 10000
5.3. User Cost Net Present Value
User cost net present value can be get by formula 2,3,4. and the result is shown in Table 5.
Tab.5 User cost NPV of steel bridge pavements
User cost NPV (.10000 yuan) Plan1 Plan2 Plan3
DDC 100.47 103.36 139.50
VOC 128.60 132.30 178.56
AC 1.73 1.78 2.40
Total 230.80 237.44 320.47
Agency cost net present value of plan2 is equal to plan3 approximately ,and higher than planl. Plan2 is 1.307 times than plan1,plan3 is 1.312 times than planl.User cost net present value of planl is equal to plan2 approximately .Plan3 is higher than plan1 and plan2, plan3 is 1.39 times than plan1and 1.35 times than plan2.
6. Conclusions
1) The sequence of life cycle net present value cost : EA+SMA> GA+ SMA> double-layer SMA, double-layer SMA structure has a better cost performance, and EA+SMA structure is the highest price.
2) Agency cost net present value of plan2 and plan3 are higher than plan1 in that material price of EA and GA is more expensive than SMA. The construction technology of epoxy asphalt mixture is difficult to control, long-time to maintenance , high technology to repair. All this leads to the conclusion that user cost net present value of plan3 is higher than plan1 and plan2.
References
Wei Huang, in: Long-Span Bridge Steel Brijkdge Deck Pavement Design Theory and Method. edtied by Chinese Architecture Industry
Publications, Beijing (2004), in press. In Chinese.
Wenya Ye, Guoping Li: Highway Vol. 6 (2006), p. 101-104. In Chinese.
Jieyao Mingzhang Wu Lie Hou: Journal of Northern JiaoTong Vol. 6 (2009), p. 118-119. In Chinese.
Daojun Han: Xiamen Haicang Bridge Steel Bridge Deck Pavement Design and Implementation. Vol. 1 (2001), p. 7-10. In Chinese.
Bo Yao: Long-Span Steel Box Girder Bridge Deck Pavement Structure Optimization Design (Southeast University Master Degree Thesis
2005). In Chinese.
