ACEI 2010 Awards for Excellence in Structural Design
Highly commended
Criminal Courts Complex
By DBFL Consulting Engineers
Introduction
The newly completed Criminal Courts Complex at Infirmary Road, Dublin 7 is the
largest Courts and Public Private Building Project completed in the history of the
State to date.
The 11 storey, 25,000m2 building contains 22 courtrooms, legal offices and
associated judicial accommodation is located at Parkgate Street / Infirmary Road.
The Circular form of the building and the stacked layout of the Courts solved the
architecturally difficult task of providing segregated routes for Judges, Jurors,
Accused Persons and the Public.
A central Great Hall with a diameter of 40m and a height of 28.4m provides a public
meeting space and access to the courtrooms at all levels.
Procurement Process
The project was procured under the PPP Process. Babcock and Brown (Amber
Infrastructure) were awarded the contact while PJ Hegarty and Sons Ltd acted as
Design and Build Contractors.
DBFL Consulting Engineers were the Civil, Structural and Transportation Consulting
Engineers and JV Tierney and Partners were the M+E Consultants. The award
winning design was produced by HJ Lyons, Architects.
The Site
The 0.95 Hectare site is located on the historic flood plain of the River Liffey and
the building straddles the original bank of the river.
Stiff black boulder clay at formation level at the original river bank and historic fill
material in the original flood plain area of the site decided the use of piles bearing
on the underlying limestone rock as the foundation solution.
DBFL Consulting Engineers liaised with Dublin City Council on the traffic and
transportation aspects and also produced traffic management plans for the
construction phase.
Site Services
A large underground surface water culvert serving the lake in the Phoenix Park
traversed the site. DBFL produced the design for the diversion of this live culvert
around the perimeter of the site to allow construction work to commence.
The density of the site required close coordination between the DBFL, the M+E
engineers and contractor to accommodate the large number and complexity of
underground services around the building.
Design Life
To meet the 100 year design life the main structure of the building is in RC. The RC
also provides the necessary acoustic values with the building.
Structural Form
The building is circular on plan with the courtrooms, service cores and offices
forming a ‘doughnut’ shape around the central Great Hall. The courtrooms are
separated by service cores that provide the segregated access routes. 27 lifts
provide vertical access up through the building.
The double storey height courtrooms are stacked 4 high above a 700mm thick RC
transfer slab. Precast concrete floor slabs in the courtrooms are supported on
275mm thick courtroom side walls. The legal offices are constructed using RC flat
slabs following the curved line of the building supported on circular reinforced
concrete columns.
Public access at the courtroom levels is provided in the Great Hall by continuous 5m
wide cantilevering RC walkways.
In the 50 week concrete construction programme 25,000m3 of concrete was cast
and 5,200 Tonnes of reinforcing steel were fixed in position.
Roof Structure
The roof over the offices and courtroom portion of the building is a reinforced
concrete flat slab to support the external mechanical plant provided at that level.
The roof over the central Great Hall is constructed using structural steelwork.
A north-light type roof design was chosen to provide natural light into the Great
Hall. A 3D frame analysis was required to be carried out by DBFL on this steel
framework to control deflections and to carry the 1300 Tonne roof loading.
Great Hall Footbridges and Feature Lifts
Glass floored footbridges link between the RC cantilevering walkways at courtroom
level in the Great Hall. Attached to these footbridges are glazed high speed feature
lifts. The structural design of these elements are interlinked as the top of the
feature lifts are not supported laterally by the main structure of the building thus
requiring a first principle analysis by DBFL of the movements of the bridges, lifts
and feature stairs to be carried out.
Great Hall Feature Stairs
A public access stairs is provided in the Great Hall between ground floor level and
the second floor level footbridge. This stairs is a three flight freestanding scissors
stairs with no support at the landings. The total stairs rise is 7.1m and the
cantilever from the supporting bridge is 10.25m. DBFL were able to use the
enclosed architectural shape of the stairs to structural advantage to design the
curved steel trusses in the solid balustrades to provide the necessary strength,
stiffness and frequency response for these stairs. The stairs have a stone finish on a
concrete filled steel tray and the balustrades are clad in timber.
Façade
The façade of the main portion of the building is a glazed twin skin system. The
external glazing is hung from a curved 14.5m max. span RC parapet beam. The
21m (6 storey) high faceted glazing panels have a stainless steel framework to hold
the individual glass panels. The design of the hung system was chosen to overcome
thermal movements in the framework due to solar gain in the cavity between the
twin skins and hence easing weatherproofing details between the panels.
Conclusion
The €140m project commenced on site in May 2007 and was completed for hand
over in November 2009 on budget and 3 months ahead of programme.
Article by
Derek Jones, Chartered Engineer
Director
DBFL Consulting Engineer