2.4. Objetivos de la investigación
2.4.1. Objetivo principal
discount the scheduled maintenance cost depending on the year in which the costs are scheduled. This is done according to Equation (3-5).
An example of the Maintenance costs schedule is shown in Table 11. Table 11, Maintenance cost schedule
Maintenance costs
schedule
year 0 1 2 3 4 …
Maintenance activity MCi (€)
Functional_inspection € 500.00 € 0.00 € 0.00 € 500.00 € 0.00 € 500.00 …
… … … …
Total nominal € 0.00 € 0.00 € 500.00 € 0.00 € 500.00 … Total discounted € 0.00 € 0.00 € 475.91 € 0.00 € 452.98 ...
The Assigned maintenance costs (MC) are calculated by summing up all the discounted yearly maintenance costs from the Maintenance schedule according to Equation (3-5). Next the appropriate percentages (see Paragraph 4.1.2) are added to cover unassigned and indirect costs.
The total Agency costs (AC) are then calculated by summing up the three sub-cost categories ICC, MC and EoLC as done in Equation (3-2).
For an example of the worksheet see Appendix B.
4.3.2.
U
SER COSTSIn the worksheet User costs the different user costs: Vehicle operation costs (VOC), Traffic delay costs (TDC) and Traffic accident costs (TAC) are calculated. This is done in a similar manner as with the Maintenance costs. A schedule similar to Table 11 is created for all the three types of user costs and the occurring costs in that schedule are then discounted and summed up according to Equation (3-8).
Summing up the VOC, TDC and TAC (Equation (3-8)) finally gives the total User costs (UC). For an example of the worksheet see Appendix B.
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4.3.3.
S
OCIETY COSTSIn the worksheet Society costs the total environmental costs are calculated. First the Environmental effects per material (EEi) are calculated by multiplying the Environmental effects per kg of material (EEi,j) as stored in the
worksheet Traffic and general input (
Table 10), by the material quantity per functional unit (Mqi) as calculated in the worksheet Bridge design (see Equation (3-16)).
Next these EEi are multiplied by the Shadow prices (SPi) as stored in the worksheet Traffic and general input
(Table 8) and summed up for every environmental effect category according to Equation (3-15). For an example of the worksheet see Appendix B.
4.3.4.
O
VERVIEWThe worksheet Overview finally displays all outputs into an easy to read page. The page shows the general characteristics of the bridge in question: the bridge deck material, the width and the span of the bridge. It also sums up the Agency costs (AC), User costs (UC) and Society costs (SC) into one total LCC value and finally graphs all occurring costs along the life cycle of the bridge.
For an example of the worksheet see Appendix B.
4.4.
C
ONCLUDING REMARKSThe tool described in this chapter is meant to allow the user to quickly and easily assess the LCC of different bridge designs. By having developed this tool the first research goal has been met. In the next chapter this tool will be applied to a specific case in order to meet the second objective of this research. The results of the case study in the next chapter will shed light on the general economic competitiveness of bridges with FRP bridge decks compared to bridges with concrete bridge decks.
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5.
CASE STUDY
The LCC tool - which has been developed in Chapter 3 and Chapter 4 – will now be used to analyse a specific case. In this chapter this case study will be described. The case under investigation in this research is the Trekvlietbrug. This case has been selected together with Grontmij to represent a rather average single span pre-stressed concrete beam bridges as good as possible.
In paragraph 6.1 a description of the case under investigation will be given. Paragraph 6.2 describes the design alternatives that were compared and which input variables have been used for these design alternatives. Paragraph 6.3 describes the traffic and general input variables used for this case.
5.1.
D
ESCRIPTION CASET
REKVLIETBRUGThe Trekvlietbrug is a vehicular traffic bridge situated at the edge of the Dutch city Leiden as part of the non-highway road Europaweg (N206). It crosses the waterway Trekvliet. According to the Provincie Zuid- Holland (2015) about 40,450 cars pass the bridge every day in 2011, rising with about 460 cars per year from 1995 until 2011. Several interventions are planned for infrastructure in the area to accommodate the rising traffic intensities. The Trekvlietbrug is one of the structures that is planned to see an upgrade in the near future. The base case in this research will be the new design for the Trekvlietbrug.
Currently the bridge consists of a draw bridge with 2 x 2 traffic lanes. The new bridge will be a simply supported single span concrete bridge. The bridge will provide for six traffic lanes and two cycle lanes and is designed to have a lifespan of 100 years.
The new bridge consists of a single sub-structure on which two separate bridge decks will be constructed, one of about 14.70 meters and the other 19.75 meter in width. The span of the bridge will be 32.50 meter. For calculation of the surface area of the bridge deck the design is simplified by assuming one single deck with a total width of 34.50 meter and a total span of 30 meters. For calculating the amount of meters of parapets and edge elements two separate bridge decks are still the assumption. Therefore these are assumed to be four times the span of the bridge.
The following information has been obtained from reference design documents and cost estimation data provided by Grontmij:
Foundation: 90 precast concrete piles (400x400 mm) with a length 18 meters.
Abutments: In-situ concrete abutments. Floor, 154.4 m2, 1250 mm thick, rebar 150kg/m3; wall, 87.24 m2, 600 mm thick, rebar 150kg/m3.
Deck: beams, SKK 1000,
Approach slabs: 5000x1000x350 mm, 67 pieces
Sheet piles: AZ37-700, length = 12meters, 104+114 meters
Sheet piles caps: 900x600 mm, 104 meters
Grouted anchors: 15 meters, 42+46 pieces
Groundwork: remove ground, 775 m3; apply ground, 200 m3
Asphalt: 120 mm thick, 1260 m2
Waterproof expansion joints: 69 meters
Sloped ground cover: 290 m2
Rainwater drainage: 4 pieces
Parapets: 144.6 meters
42 Asphalt layer Concrete deck system (depending on span) Epoxy wearing course FRP Core material
5.2.
D
ESIGN ALTERNATIVESTwo main design alternatives will be investigated in this case study. These two are: a bridge with a concrete deck (Figure 19) as also found in the reference design of the Trekvlietbrug provided by Grontmij (see Paragraph 5.1) and a similar bridge with the only difference being that the concrete deck has been replaced by an FRP bridge deck (Figure 20) based on the calculations provided in Chapter 2 (including a different top layer: epoxy vs asphalt). This means it is assumed that the rest of the bridge design (substructure and surrounding elements) stays exactly the same for both bridge design alternatives. In reality the substructure of the FRP design alternative can probably be optimized to fit the lighter FRP bridge deck. In this research this fact is not taken into account because this is determined to fall outside the scope of this research. A quick evaluation determined that the savings that might go along with a lighter substructure are expected to be rather minimal, but more research would be necessary to determine the actual cost saving possibilities. Of these two main design alternatives this research also investigates the influence that different bridge spans and differing service lives have on the LCC results. Of both main design alternatives span of 10, 15, 20, 25, and 30 meter are analysed. An overview of the different design alternatives is given in Table 12.
Table 12, Different design alternatives investigated in case study