fonctionnement des structures, typologies des treillis standard et non- standard

poinçon simple

• used during antiquité —> 15th

• 2 mailles where the length of the bar is a bit shorter than the length a franchir

poincon double:

• deux maille triangulaires and one maille quadrangulaire

• membrane inferieure isnt a poutre en flexion but a tirant en traction (more resistant)

poincons multiples

• palladio 1570

burr 1802

treillis+ arc aka combination d’ancien et nouveaux methode as a precaution

mc callum 1851

= polyganistion (imatation of curve via straigth lines aka poligon) de Burr

travaille par bar et triangulation = plus rigide

town 1820

• system petites lattes sous forme de treillis/ réseau dans 2 directions

• pieces plus mines + facile a produire/ trouver/ manipuler et assembler

• material from wood to acier later on

long 1830

• squared maille with croissement inside

• system hyperstatique (everything made with bars) → some bars replaced with cables and verticles par des tyrans

• can also précontrainte la structure = plus leger

town québécois 1905

add bars dans les croisments → too many not used → hyperstatique

Howe 1840

recherche structure isostatique> hyperstatique

diagonales en compression and verticales en traction

barre en compression thicker than traction

Pratt 1844

= diagonales en traction and verticale en compression

which one is better, pratt or howe?

pratt → howe has longer bars that are in compression (the diagonals) and qui dit compression dit flambement. we chose whoever has the least pieces en compression

EXCEPT for natural wood as il contient de noeuds = not good for traction. for wook howe’s system is better as the length of the bars in traction are shorter (as they are verticle)

brown 1857

verticle bars are removed or replaced with des tirants

croisement dans les diagonales = moins de flambements = plus fins

moisage= doubleling the diagonals aka plus de charge

smith 1869

• same system as brown but the effort tranchant is zero in the center —> remove diagonales in the center = plus de vue

neuville 1846 and Warren 1848

• thick bars for compression and thin for traction

• tech + facile to install thanks to larger mailles

• if mailles are too long= add des suspentes (tirants maybe idk) verticale pour dimnuer ses portées

howe-pratt vs warren

• poids comparable

• warren: plus flexibles a dessiner (aka more freedom in design) (due to proportions being optimales, well see that later in the chapter)

• ouvertures de mailles plus large vs howe-pratt: presence de barres verticales