LCC Methodology. Håkan Sundquist Structural Design and Bridges KTH. ETSI Methodology 1

Transcription

1 LCC Methodology Håkan Sundquist Structural Design and Bridges KTH 1

2 There are many requirements on a bridge 2

3 The classic task 3

4 The classic bridge design task 4

5 LCC optimization 5 LCC/Construction cost 100 %

6 Include maintenance and operation costs 6

7 Agency or owner costs 7

8 The bridge must also contribute economically to the society 8

9 Include society costs during maintenance and repair Include eventual accident costs 9

10 User benefit and cost 10

11 Costs for the society due to accidents and total failure Accidents are usually covered by the society and not by agencies like SRA or FinnRA 11

12 LCC Life Cycle Costing LCC is a technique which enables comparative cost assessments to be made over a specified period of time, taking into account all relevant economic factors initial capital costs future operational and maintenance costs owner costs user costs society costs future disposal cost Used methodology is usually the present value of the total cost of this asset over its lifetime 12

13 LCC scheme 13

14 Definitions LCC owner or agency LCC = LCCA + LSC + LCCC LCCA = is the cost for acquisition of the project (design, construction ) by the net present value calculated to a specified time usually the opening of the bridge LSC = (Life Support Cost) is the cost for future operation, maintenance and repair of the bridge, by the net present value calculated to a specified time usually the opening of the bridge. LCCC = (Life Cycle Cost Consequence), is the future costs for eventual negative consequences, by the net present value calculated to a specified time, usually the opening of the bridge. 14

15 LSC, the Life Support Cost LSC = CI + CN CI = is the investment in the necessary equipment and other resources for the future operation and maintenance CN is the future cost for operation, maintenance and repair, by the net present value calculated to a specified time, usually the opening of the bridge The investment part of the maintenance, CI, could be divided in parts 15

16 CI = Investment for operation and maintenance CI = CI r + CI v + CI d + CI t CI r = spare parts and material CI v = instrument, tools, vehicles that is needed for inspection and maintenance CI d = documentation i.e. drawings and instruction manuals needed for inspection and maintenance CI t = education of personnel for operation and maintenance 16

17 The costs are recalculated to one point in time usually the day of opening the bridge LCC owner = T t= 0 1 C + t r ( ) t C t the sum of all costs incurred at time t, p the real interest rate or a rate taking into account changes in the benefit of the structure and t is the time period studied, typically for a structure for the infrastructure the expected life span. 17

18 Interest rate p = pl p 1 + p i i p L interest rate for loans with long duration p i inflation Interest rate p p = p L pi 1 + p i p c p c increase of usefulness of the bridge i.e. increase of traffic 18

19 Net present cost for a cost of value=1,0 year 0 100,00 Cost 10,00 1,00 2,5% 4,0% 6,0% 8,0% 0,10 0, Interval between MR&R actions 19

20 User cost delay T L L LCC = ADT N r w + r w ( (1 ) ) user,delay t t L L L D t t= 0 vr vn (1 + r) 1 L v r v n ADT t N t r L w L w L T length of affected roadway the traffic speed during bridge work activity the normal traffic speed the average daily traffic, i.e. cars per day at time t the number of days of road work at time t the amount of commercial traffic is the hourly time value for commercial traffic the hourly time value for drivers studied time interval T 20

21 User costs, operation T L L LCC = ADT N r o + o + r o ( ( ) (1 ) ) user,operating t t L L G L D t t= 0 vr vn (1 + r) New notations: o L operating cost for the commercial traffic vehicles o G operating cost for transported goods o D operating cost for cars T time interval 1 21

22 Societal costs, accidents and T failure ( ) LCC = A A ADT N C society, accident r n t t acc t t= 0 (1 + r) New notations: A n the normal accident rate per vehicle-kilometres A r the accident rate during roadwork the cost for each accident for the society C acc n society, failure = j= 1 H, j j j LCC K R ( 1+ r) R j probability for a specified failure coupled to K H,j. K H,j cost for failure (One value for ultimate limit state and one for serviceability limit state) For normal bridges the probability of failure is so small that it could be omitted in the analysis!

23 Valuation Degradation models Knowledge on interest rents (100 year!!) Knowledge about the future of the traffic system! (will the traffic increase or decrease??) Knowledge on costs for operation, maintenance, inspection and repair 23

24 Soft values must also be included 24

25 Environmental issues must also be included! 25

26 Parameters needed for the LCC analysis Methodologies for dividing the bridge into different parts and giving measures of the components Costs for construction and repair different parts of the bridge Yearly operating costs Actions in time for MR&R actions Cost for disposal of the bridge User and societal costs 26

27 Foundation Foundation slab, plinth, pile cap Excavation, soil Excavation, rock Pile Erosion protection Slope and embankment Embankment, embankment end, backfill Soil reinforcement and slope protection Abutments and piers All concrete structures belonging to the substructure excl. foundation Main load-bearing structure Slab / deck Beam Truss Arch, Vault Cable system Pipe, Culvert Secondary load-bearing system Secondary load-bearing beam, cross beam Secondary load-bearing truss, Wind bracing Equipment Bearing and Hinge Edge beam Insulation, Water proofing Surfacing Parapet, Railing Expansion joint Drainage system Suggestion for bridge parts 27

28 Bridge parts and measures 28

29 Cross-section definitions Total bridge width Clear bridge width V K V S GC 29

30 Foundation 30

31 Materials for LCC Material Measure Quality Description Concrete m 3 C25 1 Cylinder strength in MPa Reinforcement steel ton Yield strength in MPa Steel for pre-stressing, tendons, ton 1700 Yield strength in MPa cables Steel ton Yield strength in MPa Sawn Timber m 3 Glue laminated timber m 3 Impregnated timber m 3 Backfill soil m 3 Pile m Type 4 Directly coupled to the structural element OBS, LCA requires added material definitions! 31

32 Costs Cost parameters should be given by the agencies hopefully in data bases updated every year!? Costs for construction Cost for MR&R actions Parameters for calculating the user costs Societal costs 32

33 Definition of actions Management Operation Inspections Repair Upgrading Final demolition and disposal 33

34 Operation Management is the owners own work for keeping the bridge inventory, the planning and other actions to manage the bridge stock. Usually this work can be assigned as percentage of the actual value to re-build the bridge stock. Operation is the yearly work to superficially and regularly inspect, clean, repair small damages of the bridges. The Swedish term is Drift 34

35 Examples of operation (yearly) actions Examples of operation maintenance actions. In the Swedish system this is called Egenskaper or properties Action Frequency Aim Remark Regular inspection Often Detect acute damages Cleaning of the bridge Rodding of dewatering system Cleaning of expansion joints Removal of plants and bushes, Once a year Once a year Once a year Once a year Removal of de-icing salt 35

36 Time between different MR&R actions Needed parameters: Life span Yearly operation actions Time interval between inspections Time between maintenance and repair 36

37 Methods for judging time between MR&R actions 1. Mechanistic or chemical models 2. Evaluation results from large field observations, 3. The up to day most applied method is to use experience from specialists, usually people deeply involved with inspection of bridges 37

38 LCC With everything in hand it is just to calculate the LCC for a bridge or maybe all bridges in a county or for a road network!! 38

39 GOOD LUCK! Trying and commenting our programs! 39