Technology transforms traditional materials.

Buro Happold has always been concerned with exploring new materials. Now, developments in design technology allow radical new uses for traditional materials.

The most traditional materials benefit from re-examination. Engineers with imagination -- and new data methods -- can extend and codify their potential. Stone, that traditional mass walling material, has, because of its weak performance in tension, been reduced to use as a veneer on most contemporary buildings. Characteristically it is backed with precast concrete (itself a product of ground and chipped stone) and hung as panels on the structure. But the walls of Queen's Building, Emmanuel College, Cambridge (AR February 1996) show how stone can be given back its integrity as a contemporary solid masonry wall. The building is a 200-seat concert hall adjacent to a seventeenth-century chapel by Wren, built of Ketton stone. Architects Michael Hopkins & Partners wished to use the same stone for the walls, with the advantage that its mass would give acoustic isolation from the nearby bus station. Ketton stone, a machinable oolitic limestone, was sampled and tested by Buro Happold for creep and strength characteristics and to decide on an appropriate mortar. Detailed structural analysis of stone proceeded. The result is a stone frame -- 28 stone columns with flat arches between them -- supporting the roof and the reinforced concrete floor slabs. Columns are given lateral stability by a 32mm diameter stainless-steel Macall oy bar which passes through each of them, posttensioned with a vertical 250 kN force. Loading is evenly distributed over the stonework by means of precast concrete kneeler blocks, placed at each floor level; circular stainless-steel sockets set in the blocks act as couplers to the Macalloy bars. The frame is filled in with triple glazing on the upper storey, with ashlar stone blocks on the first floor, and is left open on the ground floor to form a colonnade. The heavy(2.5kN/[m.sup.2]) roof of lead sheet pugging, membrane and oak ceiling boards, is supported by a composite truss of white American oak rafters, stainless-steel tie-rods and intermediate circular posts.

In 1981, furniture designer John Makepeace gave Ted Happold a brief to develop buildings for a school of Woodland Studies at Hooke Park Dorset, England using the most basic product--forest thinnings: thin Norwegian spruce saplings felled to allow other trees to grow large and which are usually used for fence posts. A prototype house and a workshop were designed with Richard Burton of ABK and Frei Otto to exploit the flexibility of thinnings used green (AR September 1990). The workshop, a column-free 45 x 15m space, is a shell structure of thin spruce poles, of about 165mm base diameter and 8m long. They were clamped at their bases to a concrete ring beam and bent while still green, tied together in pairs at the apex of the roof.

More recently, Westminster Lodge, an eight room student residence and seminar building at Hooke designed with Edward Cullinan Architects has been researched and tested. It is of roundwood logs and roofed with turf. Logs vary in thickness from 150 to 175mm diameter and are set on individual concrete pad foundations, then formed into a framework of walls and floors using raking struts and sliding wedges. Ends of the main frame posts are linked with steel bars, epoxy-bonded together. The roof comprises 90 to 110mm diameter roundwood poles, scarf-jointed into continuous lengths to make a double-layered timber grid which covers the 9m square seminar room in a shallow curve and supports the turf roof. The development of the raking joint and scarf joint techniques determined the shape and appearance of the finished building, revealing a new roundwood aesthetic.

In 1975 Frei Otto, with Ted Happold and Ian Liddell, then at Ove Arup & Partners, designed a timber lattice roof for the Mannheim Garden Festival, Germany, using a double-layer grid of 50 x 50mm hemlock laths at 500mm centres. This has been developed in two recent projects. The Weald and Downland Museum of historic buildings at Sussex, England with Edward Cullinan Architects, will start construction next year. In form, it is a blockwork-walled box, housing archives, set into the ground. Exhibits, including several large structures, stand on the lid of the box, which has a curved timber grid shell roof, 50m long, up to 15m wide and 9m high. The shell consists of two double layers of 40 x 20mm softwood laths at 400mm centres pin-jointed together with more than 1000 bolts. The prefabricated shell will be laid on the ground, and gradually raised, a process which will bend and twist the lath squares into diamond shapes. The fluid shape is restrained by glulam beams at the edges, and the grid is locked into place by horizontal rails supporting the cladding.

When Expo 2000 opens in Hanover next year, it will include a Japanese Pavilion with a 72 x 34m clear-span exhibition hall made of cardboard tubes, bordered by a raised viewing corridor. Working with Shigeru Ban, whose work in Japan on cardboard tube structures is well known (see for instance AR September 1996), a unique doubly-curved grid-shell structure of cardboard tubes with lightweight paper membrane cladding has evolved. The grid shell comprises two layers of cardboard tubes which act as armature to a series of wire-stiffened timber 'ladder' beams. The cardboard tubes have cross-over nodes at 1m centres along their lengths. Timber ladders are made of 75 x 60mm timber laths stiffened by tension wires to produce a lightweight and delicate support structure, providing the in-plane shear stiffness and out-of-plane bending stiffness necessary to prevent the cardboard tube shell from buckling. Ends of the shell are stiffened with laminated timber arches braced by a diagrid of tension cables from which hang en closing cardboard honeycomb panels. As required by the exhibition organization, every element is designed to be recycled -- the foundations are made of sand-bags for easy removal after use. This unique structure, in the words of the engineer, 'touches the ground lightly' in its minimalism and lightweight elegance and attempts to express 'design for planetary continuance'.

ted cullinan writes about working with buro happold

During the recent splurge of competitive tendering for professional services some engineers have turned themselves into "do it once, don't think, no dialogue, over design it, mind the insurance" monkeys. Not so Buro Happold, who seem to be inoculated against this dismal disease. It stems of course from the excellently eccentric Ted whom you could never imagine stopping from thinking, dreaming, calculating and experimenting. 'The extent to which he infected his partners with his delicious enthusiasm and the extent to which he chose them for being already infected we can only guess at. But the tragedy of his early death is surely lessened by the palpable feeling one has of the continuation of his amazing spirit when working with Buro Happold today.

'To Buro Happold you can send sketches by fax and by any other means and you know you will get a contributive response by fax, a response which spontaneously estimates the size of members in order to allow development of solutions to move forward.

'From them you get imaginative and inventive thoughts about how to build things. And in harness with Buro Happold we have made full-size live experiments with grid shells, green wood construction, jointings systems, coverings and erection sequence, in clearings in two different forests in Dorset and Sussex. And like in Ted's day, they still give great parties.'