MEMBRANES, SHELLS + GRIDSHELLS

membrane: spatial structure made of ten-sioned membranes (pneumatic structures, tensile membrane structures, and cable dome)

shell: small depth thickness compared to its other dimensions. The shell is typically unstressed unlike the membrane struc-ture.

gridshell: derives its strength from its double curvature. arrangement of material as in a grid of lattice.

cited sources:

https://en.wikipedia.org/wiki/Gridshellhttps://en.wikipedia.org/wiki/Membrane_structurehttps://en.wikipedia.org/wiki/Thin-shell_structure

https://www.metalocus.es/en/news/frei-otto-german-pavilion-expo-1967https://www.callwey.de/blog/frei-schwebend-olympiadach/https://en.wikipedia.org/wiki/Membrane_structure

MEMBRANEspatial structure - membrane in tension

biological - bubble

infrastructure - Frei Otto’s German Pavil-lion.

https://www.pinterest.com/pin/17521886024061557/shttps://www.pinterest.com/pin/17521886024061557/https://www.pinterest.com/pin/312507661622589961/

SHELLspatial structure - unstressed membrane deriving its strength from its cruvature

biological - seashells, coral

infrastructure - Felix Candela’s reinforced concrete shells.

GRIDSHELLspatial structure - grid of lattice

biological - mollusk fam-ily

infrastructure - Norman Foster’s Canary Wharf Crossrail

a gridshell case study

file:///C:/Users/ryanm/Downloads/canary-wharf_digi.pdf

Location: London

Architect: Foster + Partners

Engineer: Arup

Structural Material: Glulam

Structure Organization: Diagrid

file:///C:/Users/ryanm/Downloads/canary-wharf_digi.pdf

30 meter overhangs

file:///C:/Users/ryanm/Downloads/canary-wharf_digi.pdf

node connections

file:///C:/Users/ryanm/Downloads/canary-wharf_digi.pdf

notes from the engineer:

“structural analysis for the strucutre was challenging. With multiple levels of indeterminacy, the stiffness of eaach element influenced how the loads were distributed.... If the stiffness is increased at one locatoin, it attracts higher forces and simultaneously enighbouring areas will see reduced forced...”

+ triangle grids change in size according to location+ 300 different node types+ bending and torsion moments found in

all major and minor axis

karamba modeling

10x10

15x15

20x20

+ Dividing the surface helps localize stresses.

+ Not too many divisions due to beam material thickness.

+ Majority of stresses located on perimeter and edges.

DIVISIONS

Rx + Ry

Ry + Rz

Rz + Ry

+ Varying node releases causes a change in stress location

+ Node stiffness changes force attraction.

+ Stresses still concentrated at perimeter edges.

RESTRAINTS

2x2

4x4

8x8

+ Increasing member sizes reduces stresses...duh.

+ Localized stresses found at supports and perimeter.

+ Past member sizes 16x16 self weight is too heavy.

MEMBERS

OVERALL

+ stresses found to be localized at supports and perimeter.

+ interior members are not stresses, therefore can have larger openings, or perhaps different or lesser members.+ cantilever seems to be working, but next task is to load with different load combinations.

+ to explore the current shell further perhaps using a double shell where it touches ground.

+ streamline system according to stress hotspots.