Long Span Structure - Case Study PALAZZETTO DELLO SPORT

His characteristic, lightweight, shell structures gain their strength from the strategic placement of structural ribs. Much like a groin vault in Gothic Cathedrals, the loads acting on Nervi’s structures are concentrated along the system of ribs.

1. BUILDING CONSTRUCTION – VI Long Span Structure

2. NOTES L ong-span buildings create unobstructed, column-free spaces greater than 30 metres (100 feet) for a variety of functions. These include activities where visibility is important for large audiences (auditoriums and covered stadiums), where flexibility is important (exhibition halls and certain types of manufacturing facility), and where large movable objects are housed (aircraft hangars). In the late 20th century, durable upper limits of span have been established for these types: the largest covered stadium has a span of 204 metres (670 feet), the largest exhibition hall has a span of 216 metres (710 feet), and the largest commercial fixed-wing aircraft has a wingspread of 66.7 metres (222 feet) and a length of 69.4 metres (228 feet), requiring a 75–80-metre- (250–266-foot-) span hangar. In these buildings the structural system needed to achieve these spans is a major concern . Structural systems for long-span buildings can be classified into two groups: those subject to bending, which have both tensile and compressive forces, and funicular structures, which experience either pure tension or pure compression. Since bridges are a common type of long-span structure, there has been an interplay of development between bridges and long-span buildings. Bending structures include the girder, the two-way grid, the truss, the two-way truss, and the space truss. They have varying optimum depth-to-span ratios ranging from 1 : 5 to 1 : 15 for the one-way truss to 1 : 35 to 1 : 40 for the space truss. The funicular structures include the parabolic arch, tunnel vault, and dome, which act in pure compression and which have a rise-to-span ratio of 1 : 10 to 1 : 2, and the cable-stayed roof, the bicycle wheel, and warped tension surfaces, which act in pure tension. Within these general forms of long-span structure, the materials used and labour required for assembly are an important constraint along with other economic factors . Long Span Structure

3. NOTES Steel is the major material for long-span structures. Bending structures originally developed for bridges, such as plate girders and trusses, are used in long-span buildings. Plate girders are welded from steel plates to make I beams that are deeper than the standard rolled shapes and that can span up to 60 metres (200 feet); however, they are not very efficient in their use of material. Trusses are hollowed-out beams in which the stresses are channeled into slender linear members made of rolled shapes that are joined by welding or bolting into stable triangular configurations. The members of trusses act either in pure compression or pure tension: in the top and bottom horizontal members the forces are greatest at the centre of the span, and in the verticals and diagonals they are greatest at the supports. Trusses are highly efficient in bending and have been made up to 190 metres (623 feet) in span. Two-way grids can be made of either plate girders or trusses to span square spaces up to 91 metres (300 feet) in size; these two-way structures are more efficient but more expensive to build. The highly efficient funicular forms are used for the longest spans. Vaults made of rows of parabolic arches, usually in truss form for greater rigidity, have been used for spans of up to 98.5 metres (323 feet). Steel truss domes, particularly the Schwedler triangulated dome, have been the choice for several large covered stadiums, with the greatest span being 204.2 metres (669 feet). Cable-stayed roof construction is another structural system derived from bridge building. A flat roof structure in bending is supported from above by steel cables radiating downward from masts that rise above roof level; spans of up to 72 metres (236 feet) have been built. Another funicular form is the bicycle-wheel roof, where two layers of radiating tension cables separated by small compression struts connect a small inner tension ring to the outer compression ring, which is in turn supported by columns. Tension-cable networks use a mesh of cables stretched from masts or continuous ribs to form a taut surface of negative curvature, such as a saddle or trumpet shape; the network of cables can be replaced by synthetic fabrics to form the tension surface. Long Span Structure

4. NOTES Another fabric structure using tension cables is the air-supported membrane. A network of cables is attached by continuous seams to the fabric, and the assembly of cables and fabric is supported by a compression ring at the edge. The air pressure within the building is increased slightly to resist exterior wind pressure. The increase can be as slight as 1.5 percent of atmospheric pressure, and it is possible to maintain this even in large buildings with relatively small compressors. The cables stiffen the fabric against flutter under uneven wind pressure and support it in case of accidental deflation. Reinforced concrete , because of its inherent strength in compression, is primarily used for long spans in funicular compression forms, including vaults, shells, and domes. Thin parabolic shell vaults stiffened with ribs have been built with spans up to about 90 metres (300 feet). More complex forms of concrete shells have been made, including hyperbolic paraboloids, or saddle shapes, and intersecting parabolic vaults. An example of the latter is the CNIT Exhibition Hall in Paris, which consists of six intersecting double-shell parabolic vaults built to span a triangular space 216 metres (708 feet) on a side with supports only at the apexes of the triangle. Reinforced concrete domes, which are usually also of parabolic section, are built either in ribbed form or as thin shells. The maximum span of these domes is about 200 metres (660 feet). Another funicular form used in concrete, though it is really a composite structure, is the inverted dome, or dish. As in the steel bicycle wheel, a concrete compression ring resting on columns at the perimeter of the structure supports radial steel cables that run inward and downward to a small steel tension ring at the centre, forming the dish shape. The cable network is stiffened against wind forces by encasing it in a poured concrete dish; structures of this type have been built with spans of up to 126 metres (420 feet ). Long Span Structure

5. Long-span auditoriums involve considerations in acoustics: audiences wish to hear speakers clearly and to hear music with appropriate tonality. Unfortunately, acoustic requirements for speech quality often conflict with those for music, and it is difficult to design an auditorium that is satisfactory for both. The best single measure of acoustic performance for auditoriums is the reverberation time, which is directly proportional to the volume of the hall and inversely proportional to the amount of sound absorbency within it, including wall and ceiling surfaces and the audience itself. Measured in the sound range of 500–1,000 hertz, rooms with short reverberation times of one to 1.5 seconds are good for the intelligibility of speech, while longer reverberation times of 1.5 to 2.5 seconds add richness of tone to musical performances. Thus , adding sound-absorbent material to a hall improves it for speech but detracts from its musical qualities. People are excellent sound absorbers, and thus the audience has a distinct impact on auditorium acoustics; to keep this effect constant with varying audience size, auditorium seats are usually upholstered to serve as surrogate spectators of the same sound absorbency. Curved surfaces, which tend to focus sound, are either avoided in auditoriums or covered with sound-absorbent material. Electronic sound-amplification systems can be used to assist speakers in large halls but generally are not satisfactory for music. Other long-span buildings, such as covered stadiums and exhibition halls, receive only minor acoustical treatment . Atmosphere systems in long-span buildings must handle the considerable heat and odour generation from population densities of less than one square metre (11 square feet) per person. Air must be moved fairly rapidly through the population zone to maintain an acceptable air-change rate. NOTES Long Span Structure

6. Long Span Structure – Case Study

7. PALAZZETTO DELLO SPORT Location – Rome, . Built in – 1957 Architects – Annibale Vitellozzi Span – 60 M diameter. Structural engineer - Pier Luigi Nervi Capacity - 3500 The  Palazzetto dello Sport   also known as the  PalaTiziano  or  PalaFlaminio ,  is an indoor arena that is located in Piazza Apollodoro, in Rome, Italy. It has a 3,500 seating capacity for basketball  games. The arena is constructed with a ribbed concrete shell dome, that is 61 meters in diameter, and is constructed of 1,620 prefabricated concrete pieces. Much of the structure was prefabricated, so that the dome was erected in 40 days.

8. Pier Luigi Nervi is to architects what Pete Maravich is to basketball players or Fritz Lang is to film directors – a technical virtuoso whose extraordinary work so fundamentally broke from architectural tradition that his influence is only fully appreciated generations later. Xf` wey tfms brmhd` treosa`rs h`eh/kmv` eoh`ovmrnol`otek knehs tn tf` drnuoh ms tf`knehs eit upno tf` irnssmod (sfnwo ebnv`mo bku`), tfms irnssmod b`dmos tn b`oh uoh`rtf` w`mdft na tf` knehs •  Tf`o tf` irnssmod b`dmos tn b`oh tfmsieus`s tf` inkulos (dr``o) tn b` mo t`osmnoeoh tec` tf` w`mdft na tf` irnssmod. •  Es tf` inkulos d`t pukk`h tfms mo turo pukkshnwo tf` st``k arel` struitur` (bkeic). •  Arnl f`r` tf` st``k arel` struitur`hmstrmbut`s tf` w`mdft eknod mts mot`roekstruitur` uok mt d`ts tn tf` i`l`otinkulos (r`h). • Arnl f`r` tf` i`l`ot inkulos wfmif er`burm`h h``p motn tf` drnuoh tec` tfmsw`mdft eoh treosa`r mt tn tf` drnuoh.  besmi struitur`                                                                                                                                                                                                           PALAZZETTO DELLO SPORT Pier Luigi Nervi Pete Maravich Fritz Lang

9. Xf` wey tfms brmhd` treosa`rs h`eh/kmv` eoh`ovmrnol`otek knehs tn tf` drnuoh ms tf`knehs eit upno tf` irnssmod (sfnwo ebnv`mo bku`), tfms irnssmod b`dmos tn b`oh uoh`rtf` w`mdft na tf` knehs •  Tf`o tf` irnssmod b`dmos tn b`oh tfmsieus`s tf` inkulos (dr``o) tn b` mo t`osmnoeoh tec` tf` w`mdft na tf` irnssmod. •  Es tf` inkulos d`t pukk`h tfms mo turo pukkshnwo tf` st``k arel` struitur` (bkeic). •  Arnl f`r` tf` st``k arel` struitur`hmstrmbut`s tf` w`mdft eknod mts mot`roekstruitur` uok mt d`ts tn tf` i`l`otinkulos (r`h). • Arnl f`r` tf` i`l`ot inkulos wfmif er`burm`h h``p motn tf` drnuoh tec` tfmsw`mdft eoh treosa`r mt tn tf` drnuoh.  besmi struitur`                                                                                                                                                                                                           PALAZZETTO DELLO SPORT Pier Luigi Nervi Pier Luigi Nervi And Concrete Reinforced concrete became the dominant material in many of Nervi’s buildings once he started his firm - and as he began his career, other architects and engineers were also gradually discovering its potential. However, what separated Nervi's work was his determination to use the material not only to create structurally sound buildings, but to express its beauty and use ingenious implementation methods to build to great lengths and heights. Known as both an architect and an engineer, Pier Luigi Nervi  explored the limitations of reinforced concrete by creating a variety of inventive structural projects; in the process, he helped to show the material had a place in architecture movements of the coming years. Nervi began his career in a time of technological revolution, and through his ambition and ability to recognize opportunity in the midst of challenge, he was able to have an impact on several disciplines and cultures .

10. Xf` wey tfms brmhd` treosa`rs h`eh/kmv` eoh`ovmrnol`otek knehs tn tf` drnuoh ms tf`knehs eit upno tf` irnssmod (sfnwo ebnv`mo bku`), tfms irnssmod b`dmos tn b`oh uoh`rtf` w`mdft na tf` knehs •  Tf`o tf` irnssmod b`dmos tn b`oh tfmsieus`s tf` inkulos (dr``o) tn b` mo t`osmnoeoh tec` tf` w`mdft na tf` irnssmod. •  Es tf` inkulos d`t pukk`h tfms mo turo pukkshnwo tf` st``k arel` struitur` (bkeic). •  Arnl f`r` tf` st``k arel` struitur`hmstrmbut`s tf` w`mdft eknod mts mot`roekstruitur` uok mt d`ts tn tf` i`l`otinkulos (r`h). • Arnl f`r` tf` i`l`ot inkulos wfmif er`burm`h h``p motn tf` drnuoh tec` tfmsw`mdft eoh treosa`r mt tn tf` drnuoh.  besmi struitur`                                                                                                                                                                                                           PALAZZETTO DELLO SPORT His characteristic, lightweight, shell structures gain their strength from the strategic placement of structural ribs. Much like a groin vault in Gothic Cathedrals, the loads acting on Nervi’s structures are concentrated along the system of ribs. Gothic Architecture

11. Xf` wey tfms brmhd` treosa`rs h`eh/kmv` eoh`ovmrnol`otek knehs tn tf` drnuoh ms tf`knehs eit upno tf` irnssmod (sfnwo ebnv`mo bku`), tfms irnssmod b`dmos tn b`oh uoh`rtf` w`mdft na tf` knehs •  Tf`o tf` irnssmod b`dmos tn b`oh tfmsieus`s tf` inkulos (dr``o) tn b` mo t`osmnoeoh tec` tf` w`mdft na tf` irnssmod. •  Es tf` inkulos d`t pukk`h tfms mo turo pukkshnwo tf` st``k arel` struitur` (bkeic). •  Arnl f`r` tf` st``k arel` struitur`hmstrmbut`s tf` w`mdft eknod mts mot`roekstruitur` uok mt d`ts tn tf` i`l`otinkulos (r`h). • Arnl f`r` tf` i`l`ot inkulos wfmif er`burm`h h``p motn tf` drnuoh tec` tfmsw`mdft eoh treosa`r mt tn tf` drnuoh.  besmi struitur`                                                                                                                                                                                                           PALAZZETTO DELLO SPORT The small seating capacity and incredible roof are largely responsible for this duality. The 60-meter diameter space is spanned by the paper lantern- esque , white-painted roof. The roofs are precasted in concrete and rested over the steel frame. Consisting of a series of prefabricated concrete pieces, the roof took a mere forty days to be snapped into place.

12. Xf` wey tfms brmhd` treosa`rs h`eh/kmv` eoh`ovmrnol`otek knehs tn tf` drnuoh ms tf`knehs eit upno tf` irnssmod (sfnwo ebnv`mo bku`), tfms irnssmod b`dmos tn b`oh uoh`rtf` w`mdft na tf` knehs •  Tf`o tf` irnssmod b`dmos tn b`oh tfmsieus`s tf` inkulos (dr``o) tn b` mo t`osmnoeoh tec` tf` w`mdft na tf` irnssmod. •  Es tf` inkulos d`t pukk`h tfms mo turo pukkshnwo tf` st``k arel` struitur` (bkeic). •  Arnl f`r` tf` st``k arel` struitur`hmstrmbut`s tf` w`mdft eknod mts mot`roekstruitur` uok mt d`ts tn tf` i`l`otinkulos (r`h). • Arnl f`r` tf` i`l`ot inkulos wfmif er`burm`h h``p motn tf` drnuoh tec` tfmsw`mdft eoh treosa`r mt tn tf` drnuoh.  besmi struitur`                                                                                                                                                                                                           PALAZZETTO DELLO SPORT The forces leading outward from the roof are picked up by Y-shaped flying buttresses that ring the perimeter of the building, another reference to ancient architecture Nervi was so fond of.