Carisport Stadium Ceseria

Vittorio Legnani

Subject | The roofing over of sports grounds has always presented a great challenge for engineers and architects. On the one hand vast areas have to be spanned and acoustic and air conditioning reguirements met. On the other, roof design must satisfy aesthetic criteria but at the same time defer to what happens on the ground below.

Dr Lignano had already designed and built several covered sports stadiums in wood when Mr.Trevisani,the President of the Cassa di Risparmio in Cesena, commissioned him with the design and construction of an indoor sports ground to seat 4200 people. In Italy one of the activities of savings banks is to help finance social or public buildings, and it was from the bank that the stadium received its name: CAsa di Rlsparmia SPORT. Noteworthy in connection with this building is that the architect in charge of the planning also calculated the timber construction and then assigned its execution to the timber construction company Habitat Legno in Edolo, a firm renowned far beyond Italy's frontiers for its glued laminated wood structures. The whole of the detail planning of the timber connections was thus in the hands of this company and not in the architect's.

Structure | Here only the roof construction will be dealt with as an interesting solution for shells under tension between compression arches. The substructure with the spectators' seats is of reinforced concrete and is considered merely in its function as a support for the roof.

The roof itself may be described as two identical systems, each of which consists of two arches that open out and away from each other at an angle of 83° and support between them a taut membrane. The two arch systems are limited along the longitudinal axis of the building by tension and shear connections between the "main arches", which are inclined towards each other at a distance of 11-4.50 m. The lower "boundary arches" sweep down behind the seating, thus forming the lateral limits of the space covered. The span of the arches, that is, the longitudinal axis of the stadium is roughly 70 m. The hog, or camber, of the main arches is approx. 11.60 m, that of the boundary arches, corresponding to the spectator area, approx. 25 m.The geometry of the whole space is thus determined.

Location

Carisport, Cesena, Italy. Follow the signposts.

Client

Cassa di Risparmio, Cesena

Architect and Structural Engineer

Dr Ing. Vittorio Legnani, Studio Tecnici Associati, Bologna

Structural Details Angelo Micheletti

Timber Construction Habitat Legno, Edolo

Date of Completion 1983

Costs

According to the architect the costs of the whole stadium were 4300 million Lire.

From the structural point of view the main load-bearing structure is formed by the two higher main arches in line with the building's longitudinal axis. From these the boundary arches open out wing-like, suspended by the curved tie beams of the roof. The curve of the roof and thus that of the tie beams has been so chosen that the tie beams are subjected only to tension and the boundary arches only to pressure in the direction of the arch. The vertical forces are all transmitted as pressure forces to the supports of the boundary arches and as tensile forces via the beams to the central main-arch system. Here the tensile forces from each side more or less counterbalance each other, uneven load distribution caused by wind or snow being the only factor that can influence boundary arch position.

32 The boundary arches are thus secured against lifting or twisting - and only

Glulam Roofing Drawing

7 | Section of main arch, scale 1:25.1 Glulam roof tie beam 120 x 180 mm. 2 Glulam board-carrying members 120 x 240 mm (spacing 130 mm). 3 Roof construction: 25 mm boarding, vapour barrier, 100 mm heat insulation, two layers of waterproof sheeting. 4 Main arch comprising two 200 x 1500 mm glulam beams. 5 Boundary arch 140 x 540-210 x 800 mm. 6 Diagonal bracing 120 x 140 to 120 x 210 mm. The drawing showing the roof board-supporting members on the coupling beams dates back to an earlier planning stage. Now the roof boards are placed directly over the coupling beams and in between these on the additional timbers laid on the main arches.

8 | Section of boundary arch, scale 1:25.1120 x 180 mm glulam roof tie beam.

2 120 x 240 mm glulam roof board-supporting timbers.

3 Roof construction: 25 mm roof boarding, vapour barrier, 100 mm heat insulation, two layers of waterproof roof covering. 4 Boundary arch of two 210-1920 mm beams. 5 Sliding support of boundary arch to counteract lifting.

against such forces - by special sliding supports behind the seating areas. The main-arch supports are 4-m-high shear-wall-like abutments placed in the slant of the arches and duplicating as abutments for the boundary arches. They are designed to sustain pressure forces of some 148,000 kg each from the main arches.

Both main arches are 200 x 1500 mm glulam twin girders held apart at a distance of 10 cm by 100 x 400 x 400 mm and 100 x 100 mm spacers. 10 m apart at the bottom and 4 m apart at the apex, the main arches are coupled by means of glulam beams with a spacing of 3.10 to 3.70 m.The cross-section of the coupling beams ranges from 140 x 540 mm to 210 x 800 mm depending on their increase in length. In the spaces thus formed diagonal ties of 30 mm bar iron are provided for extra stability. Because the coupling beams are attached to the tops of the arch girders - that is, off centre - every second beam is stayed from the lower girder edge by a 120 x 140 to 120 x 210 mm diagonal beam. For easier transportation the arches were delivered in three sections and by means of wooden butt straps jointed together to form a rigid arch.

The boundary arches are also of twin glulam girder design but with a cross-section 210 x 1920 mm and no space between them. Since the connections on the roof and wall require smooth outer arch surfaces the timber fasteners of the arch sections are in the form of specially shaped flat steel plates that do not affect the cross section. The butt joints of the twin beams are staggered. The beams themselves are joined only by nailed flat iron plates, which together form the suspension element for the tie beams.

The curved 120 x 180 mm glulam tie beams are positioned where the coupling beams meet the main arches, i.e. with an average spacing of 3.50 m. By means of appropriate steel fasteners the tensile forces can thus be led away directly and, under normal conditions, free from torsion via the main arches. At a spacing of 1.30 m the tie beams carry the 120 x 240 mm glulam members that hold up the roof boarding. On this rests the vapour barrier sheeting, the 100-mm-thick heat insulation layer and the waterproofing in the form of two layers of moisture-proof sheeting. According to the architect, however, the non-ventilated roof design causes a considerable build-up of heat during the summer months.

Worth mentioning is the fact that the timbers that carry the roof boarding and are subject to bending forces display almost the same dimensions as the tie beams, which span much greater distances with no danger of buckling. The result is two spherical roof surfaces, each formed by a generously dimensioned lattice composed of similar members. As already mentioned, between the main arches in the middle of the building the timbers that carry the roof boards lie parallel to the coupling beams of the main arches, two per space and an average of 1.20 m apart. This change of direction of the roof boarding accentuates the optical effect of the central supporting timberwork and creates an interesting break between the two suspended roof surfaces.

Another point worth noting is that the steel fasteners are not concealed between the timbers but are fashioned as required by the statics of the building and by optimum manufacture. Such is the overall size of the structure and the lavish use of timber that the fasteners hardly warrant attention. They are rather a sign of artisan honesty. They may prove disturbing when near enough to catch the eye, in particular at the supports. In such cases they could shock the observer by their lack of finish but they would bring home to him the magnitude of the forces here in play.

9 | Concrete support of main and boundary arch. Just visible the lowest curved tie beam, which is more amply dimensioned.

10 | Butt joint between two boundary arch sections with hot-dip galvanised steel plates. Also visible, the staggered butt joint of the upper arch section.

11 | Fastener of hot-dip galvanized steel between boundary arch and roof tie beam. Only tensile forces are transmitted. Any deformation occurring is sustained by the screwed joint.

1 I Site plan, scale 1:3000.

2 I Section, scale 1:250.

3 | Plans, scale 1:750. Top: entrance level with changing and shower rooms as well as balcony and spectators' stand. Bottom: lower level with sports hall, weights room, offices, sports instructors' accommodation, medical facilities and services.

4 | The entrance: right, the sports hall; left, the ancillary block.
0 0

Post a comment