University of Exeter Forum Building (UK)

Client: University of Exeter Architect: Wilkinson Eyre Location: Exeter, United Kingdom Project cost: £48 million

Structural Engineer:  Buro HappoldMain Contractor/ Builder:  Sir Robert McAlpine Joinery Company:  Hazelwood Carpentry Contractors Ltd Wood Supplier:  Constructional Timber Manufacturers Ltd Gridshell roof contractor:  SH Structures

Project Details

Key facts State of the art development for Exeter

University’s campus Forum connects several facilities under an

extensive curved gridshell roof 2409 m3 - or 4,241,197 pints - of concrete

poured during project.

ARCHITECTS

Wilkinson Eyre Architects is one of the UK's leading architectural practices, based in London, England.

After gaining experience in a number of top UK practices, Chris Wilkinson set up Chris Wilkinson Architects in 1983, acting as sole principal. He

formed a partnership with Jim Eyre in 1987, with the practice registered as Wilkinson Eyre Architects

in 1999. Following an internal restructuring, the company was re-registered under the same name

in April 2006.

Designed around the theme of assembly and open debate, the Forum is a central part of the University of Exeter’s campus. The Forum Project saw several structures built or refurbished and enclosed under a stunning gridshell roof. As well as unifying these buildings and hosting a dramatic new reception, the roof shelters a range of state of the art teaching and discussion spaces.

INTRODUCTION

The University of Exeter Forum project provides a new heart for the University’s main campus.

Working with the steeply sloping site, the team created a series of concrete plateau structures that linked each of the existing building levels together

These plateaus were focused around a new triple height space covered by one of the country’s

largest timber grid shell roofs: a 3200m2 flowing form linking existing buildings and providing a new

covered street housing and academic facilities.  

Natural light pours in through triangular bays filled with EFTE roof lights by London-based Vector Foiled, chosen because they are lighter than

conventional double glazing. Each 48 square feet EFTE light consists of a three-layer cushion with a

random printed frit pattern. Double-glazed windows cover the triangular openings in teaching

and study areas to reduce rain noise.

Students originally envisioned more glass, but they ended up with half the number of light bays based on daylight modeling,. They can have too

much light, especially when students are working on computers.

Weathered, green-oak slats give the sun screen along the outer rim a feathery, natural look. The slats tie in to steel T-sections welded onto a 7.5-inch-diameter perimeter tube.

The team needed to stiffen the gridshell—to keep it from collapsing upon itself—without stretching

tension ties across the ends. They wanted a delicate junction where the roof oversails the

adjacent parapet walls. It’s all about making the shell structure as delicate as possible. The team propped the gridshell up with tubular steel pylon

columns that anchored into the ground.

The Forum’s roof encloses 3,500m² of column-free floor area

making it one of the largest timber roofs of its kind. Beneath

the roof’s copper cladding, lies an innovative hybrid timber structure which emulates the traditionally

all-steel construction of a gridshell roof, weaving between the

existing buildings of the campus.

THE ROOF copper-clad roof with ETFE

roof lights South plaza with auditorium

on right North plaza with reception on

right The naturally finished green-

oak curving roof edge filters and blocks sunlight

ETFE roof lights plug into the gridshell geometry to regulate internal daylight and mezzanine orientation spaces

Galleried indoor high street with spruce glulam members and oak cladding of gridshell roof overhead

The gridshell projects beyond the entrance glazing providing shelter and solar shading

Construction Details

The buildings and spaces in the Forum are related closely to the

campus topography, establishing an architectural language which is less about placing objects in the landscape and more about an

organic response to it.

The Forum was a result of a two-stage international design competition. The starting point for the architects was the undulating landscape of the campus, with the landscaped piazzas responding to the contours of the hillside setting. A new entrance building at the north western end of the piazza provides a reception area for the University and Great Hall. The curving roof form of the entrance building rises one storey, and then falls to trace the northern elevation of the Great Hall before merging with the Forum project.

WilkinsonEyre worked closely with glass artist Alexander Beleschenko to conceive and develop a

piece of art to sit in the outdoor sculpture trail across the Streatham Campus.

The piece is inspired by the colors of the university gardens, and has a ceramic frit on two surfaces to

give it a subtle shimmer. Sustainability was an important driver in the development of the

scheme, which has been designed to meet a series of a challenging environmental targets.

The complex, undulating roof form is made possible

by the galvanized node where all of the members’

rotation and changes in angle occur in order to tessellate the triangular

panels across the surface. Of the 150 nodes, around

20% are located outside the building, but even those

internally were exposed to the elements during the

erection and were subjected to the usual risks of

damage during transportation and

construction.

The naturally finished green-oak curving roof edge filters and blocks sunlight

The orientation, arrangement and form of The Forum respond to the contours of the rolling hills of Exmoor, which provide the setting for the building

and inspired the palette of materials specified.

The gridshell consists of prefabricated glulam timbers (twin-flitched spruce members doweled and secured with pairing screws) linked by round galvanized-steel nodes. Each node is 5 inches in diameter and contains six mounting plates for

receiving six timbers, which radiate out from the nodes like stout wagon spokes. When linked

together, the timbers form large triangular bays, which are subdivided by smaller beams.

What Is Gridshell Structure ?

A gridshell is a structure which derives its strength from its double curvature (in a similar way that a fabric structure derives strength from double curvature), but is constructed of a grid or lattice.

The grid can be made of any material, but is most often wood (similar to garden trellis) or steel.

Gridshells were pioneered in the 1896 by Russian engineer Vladimir Shukhov in constructions of

exhibition pavilions of the All-Russia industrial and art exhibition 1896 in Nizhny Novgorod.

Beneath the roof and behind the glass facades which now encapsulate the space between the existing buildings, the

Forum is an airy, galleried hall. The upper level gives access to the Great Hall, Student Guild and a new suite of learning labs and seminar spaces designed for discussion

and open debate.

The Forum has been a project of immense complexity, with countless conflicting functional requirements, a steeply sloping site, unforgiving box buildings for neighbours, a minimal disruption requirement during the four-year construction period

Wilkinson Eyre has resolved these with apparent ease, reinvigorating a number of outdated campus buildings while adding new future-proof facilities and introducing an identifiable contemporary image.

The struc-ture consists of a triangular grillage of straight glulam beams, which are pairs of 90 x 450mm deep GL32h glued laminated sections.The roof has a gentle flowing undulating

form. There are high stresses in the beams and some beams have a continues steel

plate.

The complex, undulating roof form is made possible by the galvanized node where all of the members’ rotation and changes in angle occur in order to tessellate the triangular

panels across the surface. Of the 150 nodes, around 20% are located outside the building, but even those internally were exposed to the elements during the erection and

were subjected to the usual risks of damage during transportation and construction.

This protective galvanized coating philosophy was also then carried through to the flitch plates that

were used for 10% of the beams in the most highly loaded areas and the plates used in the bolted

connections for the secondary to primary beam.

MATERIALS

The various buildings are linked by a stunning new grid shell roof, which is formed from a series of

triangular bays consisting of glulam timber members with steel nodes. The complex structure

has no standard parts with all the bays

Wilkinson Eyre Architects’ starting point was the natural features of Exeter’s hilly Streatham

campus, which strongly influenced the use of natural materials within the building, particularly

the prominent use of timber.

A plywood skin and standing-seam copper cover the roof. Beneath the plywood, the ceiling

comprises rigid thermal insulation, acoustical insulation, black acoustically transparent fabric, and finally the finished surface of 0.75-inch-by-

1.73-inch kiln-dried oak slats spaced 1.73 inches on center.

The Forum’s free flowing gridshell mirrors the rolling hills around the University of Exeter. The designers used European oak to create the effect of a wooded canopy and

capped the roof in copper, which will oxidize, form a green patina over time, and allow the building

to age in harmony with its surroundings.

The timber slats and triangular form of the roof soffit are referenced in the use of oak slats to the gallery balustrades and main internal staircases. Slatted oak cladding is also used in the new 400-seat auditorium, which has a curved and inclined brick facade, with low-level glazing.

Glulam (German spruce) external slats (Welsh oak) external green oak (Welsh) internal oak and lime-washed oak (English)

WOOD PRODUCTS USED

Glued-laminated timber, glulam, is fabricated from small sections of timber boards

(called laminates) bonded together with adhesives and laid up .Glulam has much lower embodied energy than reinforced concrete and

steel, although of course it does entail more embodied energy than solid timber. However,

the laminating process allows timber to be used for much longer spans, heavier loads, and

complex shapes.Why Glulam Timber ?

CONNECTIONS

Connections are made using steel flitch plates of thickness varying from 15mm to 40mm.

The Forum Project encompasses new and refurbished structures enclosed under a stunning

gridshell roof comprising a matrix of timber members joined by a series of galvanized steel

nodes.

Cont.……It was beneficial in generating all the plates and

Tees that went into the jigs, from which all the 162 different nodes, each carrying 6 primary timber

connections, were produced. There was a total of 14,724 drawings produced, which contained the details of 37,794 assemblies and subassemblies,

including the jig plates, which equated to 174 tonnes of steel, and over 180 cubic meters of

timber.

The bolted plate flitch joints are reinforced with vertical screws.

The roof covers around 2,000 m2 and has been built on a large load-bearing

‘birdcage’ scaffold that required rigorous dimensional control to ensure

that the various components fit together on site. The roof sun screen is

supported by a 193.7 mm diameter tube with steel tee sections welded to

it.

The ends of the primary flitch plates were site-welded to this perimeter tube, which, together with a series of internal columns,

creates a dramatic central feature of the new development.

Challenge As a central feature of the Forum, the vision for the roof was to create an enclosed street that links all of the facilities, while offering an outstanding environment for learning, teaching and research.

A key challenge at Exeter Forum was the need to design a campus that was as sustainable as possible. The client set our design teams very tough targets: to beat Part L energy guideline figures by 10% and to achieve 10% renewable energy onsite, with the aim to achieve the sought-after BREEAM ‘Excellent’ rating on completion.

Solution Due to the size and scale of the roof, and the need for it to allow lots of daylight into the space, it was vital to ensure that the internal spaces were not adversely affected by the conditions outside. Our acoustics team undertook cutting edge analysis to study the noise levels of rain on the roof, developing a digital auralisation for the client and architect to show the results and demonstrate our solutions. The work by our specialists led to the roof design being modified to use a combination of timber panels, ETFE and glass to offer an inspirational education environment.

To achieve the challenging environmental targets our sustainable design team worked closely with the architects to maximize the use of natural daylight and ventilation, thermal mass, earth tubes and ground source heat pumps (GSHPs). The GSHPs will reduce the amount of CO2 per KWh of delivered heat by 45% in comparison to a traditional gas condensing boiler.

Awards

Structural Wood Awards ,WINNER OF AWARD FOR

Education or Healthcare Structures - 2013 BREEAM Excellent accreditation

The Royal Institute of British Architects (RIBA)2013

REFERENCES

www.architecturejournals.com www.archituremagazine.com www.Wikipedia.com www.wilikinsoneyre.com

Group Members

1. Mehari Melaku ………………………………….07020102. Amanuel Tarekegn ……………………………..0701310

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