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An important tram line rehabilitation project in Istanbul

Posted: 18 August 2008 | Veysel Arli, Track & Fixed Facilities Manager and Mustafa Polat, Tram Maintenance Chief, Istanbul Transportation Co. | No comments yet

The tram line which passes through Old Istanbul to the Eminönü coast and to Galata Bridge to Kabatas Wharf in the Historical Peninsula is an important railroad. The tram line was constructed stage-by-stage between 1992 and 1996.

Transportation demand in Istanbul is continuously increasing day-by-day and there are currently 385 trips each day (between 06:00a.m. and 00:00a.m.) with a 2.5 minute headway in peak hours. The tram line used to serve 190,000 passengers per day on a 14km track with 55 vehicles. It was awarded ‘Best Practice’ in providing high transportation demand by the International Association of Public Transport (UITP) in 2005, and now the daily number of passengers has risen to 250,000 according to 2007 figures.

The tram line which passes through Old Istanbul to the Eminönü coast and to Galata Bridge to Kabatas Wharf in the Historical Peninsula is an important railroad. The tram line was constructed stage-by-stage between 1992 and 1996. Transportation demand in Istanbul is continuously increasing day-by-day and there are currently 385 trips each day (between 06:00a.m. and 00:00a.m.) with a 2.5 minute headway in peak hours. The tram line used to serve 190,000 passengers per day on a 14km track with 55 vehicles. It was awarded ‘Best Practice’ in providing high transportation demand by the International Association of Public Transport (UITP) in 2005, and now the daily number of passengers has risen to 250,000 according to 2007 figures.

The tram line which passes through Old Istanbul to the Eminönü coast and to Galata Bridge to Kabatas Wharf in the Historical Peninsula is an important railroad. The tram line was constructed stage-by-stage between 1992 and 1996.

Transportation demand in Istanbul is continuously increasing day-by-day and there are currently 385 trips each day (between 06:00a.m. and 00:00a.m.) with a 2.5 minute headway in peak hours. The tram line used to serve 190,000 passengers per day on a 14km track with 55 vehicles. It was awarded ‘Best Practice’ in providing high transportation demand by the International Association of Public Transport (UITP) in 2005, and now the daily number of passengers has risen to 250,000 according to 2007 figures.

Existing track structure

RI60 grooved rails with a quality of 700A are used in the existing tram line. Rails are constructed on reinforced concrete blocks (30x15cm). Rubber layers were placed to provide elasticity between blocks and the rail and there is a 3-5cm of asphalt layer under blocks to arrange top level of the rail. Rails are connected to each other by gauge bars every 1.5m to keep the gauge up. The track is placed in a ‘U’ shaped concrete bedding which is C20 quality. Sand and hard cores were filled inside the concrete bedding and concrete stones were used as pavement.

Tram line deformations

Some geometrical deformations may occur in the track superstructure over time and the main reasons for this is a collapse under the block stones and slippage of the elastic layer between the rail and the blocks. In addition, increased gauge deformations may occur because of the broken gauge bars in tight curves and cant deficiency may occur with the collapse of the outer rail over time. In fact, besides geometrical deformations, the biggest problem is excessive rail wear. Here, lateral wear occurs at the narrow curves with less than 30m radius, and vertical rail wear occurs in ramps with more than a 4% slope. According to statistical data recorded over the last 10 years, the average velocity of vertical and horizontal rail wear is 2mm per year.

Maintenance studies

To decrease rail wear problems, there must be a periodical visual control and a maintenance programme related to inspections. The maintenance programme includes periodical preservative maintenances and corrective maintenances, which are conducted according to needs. 90% of these maintenances are corrective.

To decrease rail wear problems, rails over the wear tolerance are exchanged with RI59N (RI59 R13) hardened grooved rails, which are 900A quality and have a hardness of 340 HBN. Also, because the groove of new rails is 5mm wider, it reduces wear at the narrow curves. Also, stationary electronic lubrication pumps were installed to reduce wheel squeal and rail wear problem in curves with less than 100m.

According to data recorded over the last 10 years, geometrical repair intervals were taken every four years in the same location and repair costs of a 1km single sections was about €25,000 per year.

Tramway Rehabilitation Project

Transportation demand of the tram line is as much as a metro line, which is why the infrastructure is continuously harmed under the load of heavy traffic. As a solution, slab track systems were conducted. The main problem that we faced is that it is not possible to stop the service on such a line.

In Europe, similar rehabilitation projects were investigated on-site and it is possible to close rail operations during railway reconstruction. Alternatively, operations were completed on one way by temporary switches which were installed on both sides of a zone.

This alternative was evaluated for Istanbul’s own conditions but eventually not accepted because there are not enough suitable locations to install temporary switches. As a result, due to high transportation demand, Istanbul Transportation Co. decided to complete all works during night hours (working time is five hours per shift) without closing any operations. Reconstruction of 4km of line was been completed between 1998 and 2006 by our maintenance team.

In the direct fixation system, a system to carry railroad loads within the duration of digging, clearing out and arranging geometry of track and concrete getting harder was needed (see Figure 3 and 4). The wheel loads on the rail should not be applied to fresh concrete during the first phase; otherwise there will be flaccid on anchorage units. To avoid this risk, rail hanger fixings designed by our engineers and technicians started to be used in 2007. Istanbul Transportation Co. has appealed to get a patent for the system called ‘URAYSAS’. Rail hanger fixings is a system which carries vehicle loads and avoids anchorage units to get any load until concrete getting enough resistance. Also, the rail hanger fixings are very practical to arrange rail geometry in vertical and horizontal directions.

Meanwhile, labour service has been purchased and rail rehabilitation capacity has progressively increased. In 2008, rehabilitation is continuing by exceeding 1,000m per month. According to the work plan, it is estimated to renew the entire line by October 2009.

Rehabilitation cost for a 1km single section is approximately €300,000 and 30% of this cost is for labour and 70% of this is for material and equipment.

Rails are fixed on 20cm C30 ready concrete on the tram line rehabilitation project by an elastic rail fastening system (see Figure 5). A Pandrol SFC rail fastening system is used in the project and provided by Istanbul Transportation Co. Rail fastening spaces are 75cm each. Another concrete layer is poured on the top of the base concrete and as pavement; colored asphalt with a 5cm thickness is layered (see Figure 6). Meanwhile, old rails are replaced with 900A HSH (head hardened rail) rails.

Tramway operations are continuing by means of rail hanger fixings and do not cause any delays. We are proud of operating this project successfully in the city centre where there are lots of railway, roadway and pedestrian traffic and we know that such a project running with its own special conditions will be a special example for many new projects.

There are some priorities in the project because the tram line passes through residential zones and road vehicles also pass along the line.

Here is the priority order:

  • Work safety as a priority
  • Taking measures to not to disturb tramway, motorway and pedestrian traffic, for example, to do crossroads at the weekends
  • Taking care of environmental aesthetics

Conclusion

A ‘Life Cycle Cost Analysis’ is to be taken and in this analysis operating and maintenance costs (even environmental and social costs like vibration, noise and air pollution and comfort) are taken into calculation for each alternative. In short, not only the construction cost but also all costs during the service life should be calculated. This is a very important point that a railway with a poor infrastructure means more expensive and annoying maintenances during its lifetime. It is very hard to operate maintenance in city centres where there are lots of motorway and pedestrian traffic. Therefore, it is necessary to construct urban railways with slab track.

Istanbul Transportation Co. aims to provide safety and comfortable transportation for Istanbul citizens.

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