BIArch BT 01

BT.101 - The building structure Professor Dr. Architect AgustĂ­ Obiol Assistant professor Architect CecĂ­lia Obiol

exercise 01: conceptual analysis of 5 projects George Kallis

PART 01: BASIC FORM OF WORK

01. SANTA SOFIA CHURCH Antemio De Tralles & Isidoro De Mileto

Load distribution: (in all directions)

external load

internal forces

support reactions

buttresses: deploying axial + shear force

columns: mainly axial force

dome: uniform distribution in all directions

Basic form of work: a. Compression [domes, arches and columns] b. Bending moment [buttresses due to shear reaction] Loads are distributed uniformly in all directions from the main central dome to the main columns and secondary domes and columns. They are mainly distributed by compression forces due to the concaved geometry of the dome system. Bending moment is also deployed in the buttresses, because of the shear forces counterbalancing the horizontal components of the internal forces.

02. WASHINGTON DULLES AIRPORT Eero Saarinen

secondary direction main d

irection

Load distribution: (main direction)

external load column weight: counterbalancing tension force in the roof support reactions

internal forces: axial tension force [mainly]

Load distribution: (secondary direction) bending moment diagram

Basic form of work: a. Tension [roof-main direction] b. Bending moment [roof-secondary direction] c. Compression + Bending moment [columns] In the main direction, the geometry of the roof structure absorbs the external load by means of mainly axial tension force, which is then distributed to the columns. The columns are tilted so as to counterbalance the horizontal component of the tensile force, deploying a bending moment using the perpendicular tho them weight component. This way, their support to the ground could be simplified, however, large mass is needed to absorb all the load from the roof. The roof is already pre-stressed with tension and is quite heavy so as to minimize the deflections caused by the external loads.

03. MUNICH OLYMPIC STADIUM Frei Otto

Load distribution: (all directions)

support reactions: combination of tension (anchorage cables) and compression (pole mast)

external load internal forces: axial tension force

axial tension force in anchorages and pre-stressed roof elements

compression of pole mast

Basic form of work: a. Tension [roof and anchorages] b. Compression [pole masts] The load is distributed axially through the roof pre-tensed cables, therefore a force of tension is deployed. This forces are transferred to the ground through the large pole masts, which are compressed. The stability of the system is achieved by the anchorage cables which transfer tensional forces to the ground, counterbalancing the horizontal components of the tension forces deployed in the roof cables

04. PORTO ALEGRE CENTRAL MARKET Eladio Dieste

secondary direction

n

ctio

in

ma

e dir

Load distribution: (main direction) external load internal forces: axial compression force [mainly] shear force in cantilevered part causing bending moment support reactions: axial force + bending moment to support cantilever

(secondary direction)

internal forces: axial compression force [mainly] secondary bending moment due to roof curvature

Basic form of work: a. Compresion [roof-main direction] b. Bending moment [cantilevered part] c. Compression + Bending moment [columns - supports] In the main direction, the arched geometry of the roof structure absorbs the external load by means of mainly axial compression force, which is then distributed to the main beams and columns. The curved geometry of the roof in the secondary direction, makes also possible the load distribution mainly through compression. Some bending moment is deployed, mainly in the cantilevered section and in the roof’s secondary direction.

05. HUESCA PAVILION Enric Miralles

secondary

ection

main dir

direction

Load distribution: (main direction)

support reaction

external load

internal forces: axial tension force

support reaction: compression in the pole mast tension in the anchorage

Load distribution: (secondary direction)

bending moment diagram of secondary direction

Basic form of work: a. Tension [roof-main direction] b. Compression + Tension [pole masts + anchorage] c. Bending moment [roof-secondary direction] In the main direction, the geometry of the roof structure absorbs the external load by means of mainly axial tension force, which is then distributed to the support on the one hand, and to the pole mast and anchorage on the other, through axial compression and tension forces respectively. The couple of forces in the anchorage + mast absorb both vertical and horizontal components of forces. Bending moment is deployed in the roof in the secondary direction, where it works basically as a hyperstatic beam.

PART 02: COMPARISON + SIMILARITIES

01. SANTA SOFIA CHURCH Antemio De Tralles & Isidoro De Mileto

PORTO ALEGRE CENTRAL MARKET Similarities: Both projects use the arch as the basic construction element of the roof.

Therefore, the stress is mainly distributed through axial compression forces.

Also, the load is distributed to the earth through columns (or buttresses) in which compression forces and bending moment is being deployed Differences: Whereas Santa Sofia works in 3D in all directions in the same way because of the double symmetry of the dome, the market has a main direction and a secondary, i.e. the roof is a series of arched slabs, thus mainly working in 2D.

MUNICH OLYMPIC STADIUM Similarities: In both projects the load is distributed uniformly in all directions (in plan) without having a main and secondary one. Thus a 3D performance in both cases.

Differences: The load is transferred in the roof in completely opposite manners.

Pure compression for the church because of the dome and pure tension in the stadium because of the pre-stressed cables.

WASHINGTON DULLES AIRPORT Similarities: The use of heavy supports to absorb the roof load through compression and mending moment.

Differences: Compression forces are deployed in the church, whereas mainly tension (and bending moment) is deployed in the airport. The latter has a uniform cross-section repeated along an axis, Santa Sofia has a central point and almost double symmetry (2D vs. 3D structural system).

HUESCA PAVILION Differences: A lightweight roof stressed in tension (and bending moment) on the one hand and a strong dome stressed in compression on the other. Two structural directions for the pavilion (mainly 2D structure), one direction (plan) for the church (3D structure). Composite supports receiving axial forces in Huesca pavilion, Heavy supports receiving compression and bending moment in Santa Sofia church.

02. WASHINGTON DULLES AIRPORT Eero Saarinen

HUESCA PAVILION Similarities: In both projects the forces acting on the roof are in the form of axial tension in the main direction and bending moment in the secondary. Both roofs are “hung” on pole mast supports.

Differences: Airport’s support is heavyweight, receiving bending moment as well as compression, whereas the pavilion’s support has anchorage elements, thus deploying compression (in the pole mast) and tension (in the cables) to achieve stability.

MUNICH OLYMPIC STADIUM Similarities: In both projects the main forces acting on the roof are in the form of axial tension.

Differences: The stadium has a 3D performance, contrary to the airport which performs in 2D. Also, the stadium is lightweight, working only under axial stress, whereas the airport is heavier, absorbing bending moments as well.

PORTO ALEGRE CENTRAL MARKET Similarities: Both buildings have a mainly 2D performance, working as a series of repeated cross-sections. The load is transferred to the earth through compression and bending moment deployed in the columns.

Differences: Dulles airport’s roof mainly receives tensional forces, whereas Porto Alegre market’s roof works mainly under compression.

SANTA SOFIA CHURCH Similarities: The use of heavy supports to absorb the roof load through compression and mending moment.

Differences: Compression forces are deployed in the church, whereas mainly tension (and bending moment) is deployed in the airport. The latter has a uniform cross-section repeated along an axis, Santa Sofia has a central point and almost double symmetry (2D vs. 3D structural system).

03. MUNICH OLYMPIC STADIUM Frei Otto

HUESCA PAVILION Similarities: The roofs of both buildings are lightweight, stressed with mainly axial tension force. The load is transferred by means of pole masts, supported by prestressed cables, thus no bending moment is deployed in the supports.

Differences: The stadium has a 3D total performance, contrary to the pavilion which mainly performs in 2D. Also the stadium’s roof consists of pre-stressed cables in both directions, whereas Huesca pavilion’s roof has the cables only in one direction.

WASHINGTON DULLES AIRPORT Similarities: In both projects the main forces acting on the roof are in the form of axial tension.

Differences: The stadium has a 3D performance, contrary to the airport which performs in 2D. Also, the stadium is lightweight, working only under axial stress, whereas the airport is heavier, absorbing bending moments as well.

SANTA SOFIA CHURCH Similarities: In both projects the load is distributed uniformly in all directions (in plan) without having a main and secondary one. Thus a 3D performance in both cases.

Differences: The load is transferred in the roof in completely opposite manners.

Pure compression for Santa Sofia church because of the dome and pure tension in the stadium because of the pre-stressed cables.

PORTO ALEGRE CENTRAL MARKET Similarities: Use of light roof structure, benefiting from the geometry.

Differences: Tension members in Munich stadium, compression domes in Porto Alegre market. Overall 3D performance for the former and mainly 2D performance for the latter. Stadium’s supports consist of an anchorage system receiving axial forces, markets supports receive compression and bending moment.

04. PORTO ALEGRE CENTRAL MARKET Eladio Dieste

SANTA SOFIA CHURCH Similarities: Both projects use the arch as the basic construction element of the roof.

Therefore, the stress is mainly distributed through axial compression forces.

Also, the load is distributed to the earth through columns (or buttresses) in which compression forces and bending moment is being deployed Differences: Whereas Santa Sofia works in 3D in all directions in the same way because of the double symmetry of the dome, the market has a main direction and a secondary, i.e. the roof is a series of arched slabs, thus mainly working in 2D.

WASHINGTON DULLES AIRPORT Similarities: Both buildings have a mainly 2D performance, working as a series of repeated cross-sections. The load is transferred to the earth through compression and bending moment deployed in the columns.

Differences: Dulles airport’s roof mainly receives tensional forces, whereas Porto Alegre market’s roof works mainly under compression.

HUESCA PAVILION Similarities: The two buildings work mainly in 2D whereas their geometry tries to benefit from both directions. In both roofs, bending moment is partially deployed in the secondary direction.

Differences: The sports pavilion’s roof mainly receives tensional forces, whereas the market’s roof works mainly under compression. Also the pavilion’s supports are composed by pole masts and anchorage cables, whereas the market’s supports are columns which are compressed and deploy bending moment as well.

MUNICH OLYMPIC STADIUM Similarities: Use of light roof structure, benefiting from the geometry.

Differences: Tension members in Munich stadium, compression domes in Porto Alegre market. Overall 3D performance for the former and mainly 2D performance for the latter. Stadium’s supports consist of an anchorage system receiving axial forces, markets supports receive compression and bending moment.

05. HUESCA PAVILION Enric Miralles

WASHINGTON DULLES AIRPORT Similarities: In both projects the forces acting on the roof are in the form of axial tension in the main direction and bending moment in the secondary. Both roofs are “hung” on pole mast supports.

Differences: Airport’s support is heavyweight, receiving bending moment as well as compression, whereas the pavilion’s support has anchorage elements, thus deploying compression (in the pole mast) and tension (in the cables) to achieve stability.

MUNICH OLYMPIC STADIUM Similarities: The roofs of both buildings are lightweight, stressed with mainly axial tension force. The load is transferred by means of pole masts, supported by prestressed cables, thus no bending moment is deployed in the supports.

Differences: The stadium has a 3D total performance, contrary to the pavilion which mainly performs in 2D. Also the stadium’s roof consists of pre-stressed cables in both directions, whereas Huesca pavilion’s roof has the cables only in one direction.

PORTO ALEGRE CENTRAL MARKET Similarities: The two buildings work mainly in 2D whereas their geometry tries to benefit from both directions. In both roofs, bending moment is partially deployed in the secondary direction.

Differences: The sports pavilion’s roof mainly receives tensional forces, whereas the market’s roof works mainly under compression. Also the pavilion’s supports are composed by pole masts and anchorage cables, whereas the market’s supports are columns which are compressed and deploy bending moment as well.

SANTA SOFIA CHURCH Differences: A lightweight roof stressed in tension (and bending moment) on the one hand and a strong dome stressed in compression on the other. Two structural directions for the pavilion (mainly 2D structure), one direction (plan) for the church (3D structure). Composite supports receiving axial forces in Huesca pavilion, Heavy supports receiving compression and bending moment in Santa Sofia church.