MODELLING THE EVACUATION CAPABILITY OF A LISTED BUILDING

This project involved undertaking an evacuation performance study of a Grade II listed building at the University of Greenwich Maritime Campus (known as the Cooper Building), using the buildingEXODUS evacuation model.

Evacuation analysis is often only considered important for the design of new buildings.  However, most buildings will undergo a change of use in their lifetime.  With the proposed change of use of the building comes a need to reassess the evacuation capability of the structure.  This is to ensure that either the current evacuation capability is sufficient to cater for the new use of the structure or to suggest structural or procedural changes that will need to be implemented.   When dealing with Listed Buildings, the analysis becomes more challenging as the scope for structural alterations can be rather limited.
 
Built originally to serve the Pathology needs of the adjacent Seamen’s hospital, the Cooper Building is now part of the Maritime Campus of the University of Greenwich.  While it has only been part of the University for a few years, it has already undergone several transformations, and it is now proposed that the usage of the building be changed to a student union facility. As such, the building will house a combination of offices and recreational facilities with a corresponding appropriate increase in the maximum building population. This paper explores the viability of different structure utilisation, exploring the impact of pre-movement delays upon evacuation performance and the impact of different combinations of exit loss.   The insight gained through this analysis allows context specific procedures and configurations to be created to expedite an evacuation.  One such configurational alteration that is recommended is that the disabled access ramps, which at present are situated adjacent to areas of high occupant flow, are moved to less critical areas.

In recent history, the Cooper Building was used by the University of Greenwich as part of the PSET School, including a main library and more recently as the home of a University research group (FSEG) and the University Estates Department.   The building has two floors and three main exits on the ground floor.  The upper floor has a range of offices and is served by a single main spiral staircase.  The ground floor has a range of large office spaces and a large open space used as the library.   The library space is accessed by two doors, one off each of the main corridors that run along the building (see figure).  The library is at a lower level to the main corridors and so several steps must be descended on passing from the corridor into the library.  Access ramps for the disabled are also placed at each of these exits.  A proposed use of the building is as the main student union facility at the Greenwich Campus including bar and recreational facilities.

The first set of scenarios briefly investigated the Cooper Building as an education building.  Typically this type of building would contain a mixture of staff offices, classrooms and laboratories.  A series of scenarios are developed to evaluate the evacuation performance of the building using an appropriate sample population for the proposed usage.  The evacuation capability of the structure in this use was shown to be adequate.

The project focused on the second set of scenarios that concern the utilisation of the Cooper Building as a student union facility.  Typically this type of building would contain a bar/dance floor, several lounge areas and various offices to support the student union’s services.  It is proposed that the bar/dance floor area be situated where the library was located.  As the building is listed as grade II, it will be assumed that no major physical alterations can be made to the fundamental structure.  A relatively large population, suitable for the proposed usage, was generated and the evacuation performance of the building reanalysed.

One of the key parameters in any evacuation analysis is the pre-movement time distribution.  Obtaining a definitive set of pre-movement delays for a particular structure is a difficult task.  Therefore when evaluating a building’s evacuation performance it is sensible to examine the impact of various levels of pre-movement delays.  As part of this analysis, a sensitivity study is undertaken and presented on pre-movement times.   Another sensitivity study undertaken concerns the possibility of the loss of an exit.  History is littered with disastrous examples of exits becoming blocked or inaccessible during real emergency evacuations.   Various exit loss scenarios are analysed and the results presented.

From the analysis it was apparent that two of the key internal exits performed exceptionally poorly.  From studying these results it was suggested that the placement of disabled access ramps adjacent to the internal exits could contribute to the poor exit performance predicted.  The hypothesis was tested through altering the building geometry and replacing the disabled access ramps with a step.  This was found to significantly improve the exit performance, confirming the hypothesis.   From this analysis, it is clear that the positioning of disabled access ramps requires careful consideration.

For more information about evacuation modelling and the EXODUS software visit the EXODUS Web Pages. For a complete listing of EXODUS and evacuation publications visit the FSEG Publications pages.