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12 Dec The Route To Operational Implementation

Posted at 22:31h in Features by

Modern mass transportation hubs, including railway stations and airports, form part of a progressive infrastructure network often encompassing contemporary retail and leisure facilities thus creating a unique passenger experience. This coming together of a mixed occupancy environment provides particular challenges to the design team, including the fire engineer, which must be addressed to satisfy international codes and best practice, local requirements and the employer’s requirements. Peter Stephenson, Associate Director of Buro Happold Engineering discusses these challenges with a focus on the Riyadh Metro network in the Kingdom of Saudi Arabia from the fire engineer’s perspective.

The question of “why invest in a new rail infrastructure across the GCC” is often asked and some of the primary motivators can be summarised as:

  • congested urban roads
  • increasing populations
  • greater appreciation for rail as a sustainable means of transport
  • the wish to propel economic development across the region
  • a blank canvas to build the world’s most advanced mechanised passenger and freight transport systems

The Kingdom of Saudi Arabia has ambitious plans for the future development of a modern rail network. The Saudi Rail Master Plan (SRMP) 2010-2040 identifies 19 individual railway lines with approximately 9,900km of tracks planned with a cost of circa 365bn SAR ($97.3bn). A Metro is proposed for each major city along with high speed rail track interfaces. Saudi Arabia is planning to have the regions premier freight line to assist the Kingdom as an attractor market helping to provide improved access to new and existing businesses and facilitate the growth of the leisure and tourism industry.

As part of the future Riyadh Public Transport Project (RPTP), Arriyadh Development Authority (ADA) is planning the development of an extensive metro system serving the city of Riyadh with 6 metro lines, 85 stations, a track length of 176km with a budget of 84.4bn SAR ($22.5bn).

The Project has been divided into three “Packages” as follows:

  • Package 1: Lines 1 and 2
  • Package 2: Line 3
  • Package 3: Lines 4, 5 and 6

The key project stakeholders involved with the packages are:

  • Client – Arriyadh Development Authority (ADA)
  • Authority Having Jurisdiction (AHJ) – The General Directorate of Civil Defence (GDCD)

This ambitious project consists of:

  1. Viaducts
  2. Elevated Stations
  3. Surface Stations
  4. Deep Underground Stations
  5. Iconic Stations
  6. Park & Ride
  7. Depots
  8. Track
  9. Tunneling & Egress Shafts
  10. Transit System
  11. Life Safety Design Basis
  12. Tunnel Ventilation Concept

features_riyda_mapTo give a brief insight into the project,

Line 1: Blue Line consists of:

  • 38 km
  • 13.75 km of Viaducts
  • 27 Stations
  • 3 Park & Ride Facilities
  • 2 Depots

Line 2: Red Line consists of:

  • 23.8 km
  • 4.72 km of Viaducts
  • 14 Stations
  • 2 Park & Ride Facilities
  • 1 Depot

Metro Design

Local and international building codes for typical buildings do not readily address the unique fire safety challenges associated with modern train station design.

NFPA 130, ‘Standard for Fixed Guideway Transit & Passenger Rail Systems’, represents best practice for the fire safety design of train stations, is used extensively internationally, and forms part of the NFPA suite of documents that are understood to be acceptable to Civil Defence in Saudi Arabia. Consequently, this NFPA standard forms part of the design basis for the metro stations including Olaya Riyadh Metro station, one of the mixed use iconic stations. There are however elements of the station design that are beyond the scope of NFPA 130, so additional codes need to be referenced.

Whilst NFPA 130 focuses on the fire safety design of platforms and concourse areas, the standard must be supported by a Building Code for the detailed design of areas that are ancillary to the platform and concourses. NFPA 101 ‘Life Safety Code’ has been adopted to support NFPA 130 for the fire safety design.

Building Description

The Olaya Metro Station will be designed to include the following:

  • station access at ground level
  • Line 1 and 2 platforms at the two lowest levels in the station pit (Line 1 circa. 30m below grade)
  • mezzanine and concourse levels providing access to the platform levels and the retail
  • four levels of retail around the perimeter of the station including a food court and ancillary accommodation, including offices, plant rooms and prayer rooms
  • three levels of underground car park, delivery and waste removal area for the retail
  • Technical (Plant) level underneath lowest car park level
  • ground floor external bus interchange and taxi ranks underneath roof structure
  • public roof top park

Demonstrating Compliance

Fire engineering employs performance based design solutions, where necessary, to achieve the life safety goals and objectives of prescriptive requirements within documents such as NFPA 130, and provide an equivalent or greater level of fire safety. The life safety goals and objectives of NFPA 130 should be given due consideration for the areas covered by that standard: Life safety goals; NFPA 130, Chapter 4.2 (Goals) and Life safety objectives; NFPA 130, Chapter 4.3 (Objectives).

When deviating away from code guidance a performance based design should achieve both the goals and objectives. This provides a performance based alternative to the prescriptive provisions of the Code. The performance based option is a process that can be used to determine whether the building design satisfies the fire safety goals and objectives specified in the Code. It is not the intention of the performance based approach to replace the prescriptive Code, but to demonstrate an equivalent, or better than, level of safety as the prescriptive guidance (NFPA), and as such provide design flexibility.

The key areas of Performance Based Design revolve around the use of evacuation and CFD modelling to determine the performance of the egress system and the tenability for this period.

The provision of sprinklers in a railway station requires careful consideration. NFPA 130: Clause 5.7.3.1 recommends that automatic sprinkler protection be provided in areas of stations used for the following: concessions , general storage,  refuse rooms and other similar areas with combustible loading, except train ways.  Where high ceiling levels are experienced and sprinklers are unlikely to be effective, their removal from the design should be robustly demonstrated to the AHJ with particular consideration given to the fire loading where it is not similar to areas listed in NFPA 130.

The fire strategy for the station under consideration should address credible scenario’s and may include the following:

  • Train-way fire – a fire occurring within the train way can occur in one of two ways, from either a stationary train within the station, or from a train arriving already on fire and necessitating evacuation of passengers. A fire which occurs on-board a moving train presents a greater risk to on-board passengers and passengers on the platform compared to a stationary vehicle fire, as the fire will have had time to develop prior to arriving at the station.
  • Platform (baggage) fire – fire load on platforms will consist of transient fire loads, mainly luggage. A fire involving such a hazard may not present a significant risk to passengers where the open nature of the platform and the smoke control systems are designed to keep tenable conditions during evacuation.
  • Public area fire – A fire within the public areas of the station can occur from two primary types:
  • transient fire hazards – including luggage or rubbish containers. These will present a relatively low fire load however are unenclosed and open to the concourse.
  • fixed fire hazards – can consist of retail concessions, ticket offices etc. These hazards may be enclosed in a fire resistant construction with active protection including smoke control, fire shutters and automatic sprinklers.

Fires occurring within such locations will initially only present a risk to occupants within the compartment of fire origin. Those within the main concourse will not be placed at immediate risk.

  • retail area fire – may often be split into a number of smaller units, rather than a single destination retail unit.  As such, phased evacuation of the retail areas and main station could be considered, focussed on the level of management available within the large retail unit.
  • car park – a fire in the multi-storey underground car park would be separated from the main station by fire-rated compartmentation and would present a risk to the people within the car park and the adjacent accommodation only and could be considered as a separate evacuation zone to that of the main station.
  • ancillary accommodation fire – all non-public areas will be separated from public areas with fire
    resistant constructions. A fire occurring in such areas will not immediately affect the greater concourse or platform population.

Looking Forward

The future commitment to the rail infrastructure in Saudi Arabia has been laid out in the SRMP and the design and build of the Riyadh Metro is well underway to achieve operational implementation in 2019. Fire safety professionals across the globe will continue to strive towards providing a safe and efficient rail system and realise the ambitions of the Middle East Region.