FUNICULAR STRUCTURAL SYSTEM

FUNICULAR STRUCTURAL

SYSTEM• ARCH• VAULT• CATENARY CABLE• MEMBRANE• PNEUMATIC

Form active structures : structures in which load is taken by the form or the shape of the structure. non-rigid, flexible shaped in a certain way and secured at the ends can support itself and span space only tensile and compressive stresses persists.

funiculus - any of several body structure resembling a cord

ARCH STRUCTURES

ARCH• is a curved structure• the arch is an inverted string catenary• can span large openings while supporting weight : doorway• can be built into a wall or from its own base• made from wedge shaped pieces (voussoirs) that lean against each other• only suitable for resisting compression• arches only carry loads in compression : no tensile stresses (or only very small ones)

By corbelling out the masonry blocks as shown : A corbel is a stone which projects from masonry. It is a simple example of what has come to be called a cantilever

ANCIENT

The use of two inclined stone beams, method which also was used in the pyramids : with adequate depth of the stone "beams" no tensile stresses are produced, and this structure can therefore support heavier loads than can be supported by a horizontal beam. 

third stone, as shown in Fig. 4.4 (a). As long as there is sufficient resistance supplied to the thrust by the abutments, the stones can be said to support one another by their mutual com pression and cannot fall into the space below them. This can be said to be an intuitive approach to the problem. By using still more stones or bricks, longer spans can be bridged, as in Fig. 4.4 (b)

perfect SHAPE for an ARCH

Load distribution

A buttress is a thickening of a wall or an outside walls at right angles used to make a wall stronger. Very thick forming buttresses which can resist the sideways forces.

Stability of structures

A buttress slanting from a separate pier, typically forming an arch with the wall it supports

buttress

A D V A N T A G E S :• the strongest shape with the least amount of material known• the only shape that can use single individual modules of materials, like brick and stone• be used to span a distance that straight stone spans could never do• large expanses without the tensile limit presented by the material itself

D I S A D V A N T A G E S :• is the shape itself : The curve of an arch makes it difficult to erect and also if you are using steel or concrete you have to form the pieces to fit the curve

VAULT STRUCTURES

• an arched structure, usually of masonry or concrete, serving to cover a space.• an arched overhead covering, that resembles the architectural structure in form•consist of a series of arches, or a continuous arch, to form the ceiling of a structure

Six primary subsystems :

Barrel VaultsCross VaultsRib VaultsFan VaultsCurved Rib Vaults

* According to arrangement of the columns and arches, and the degree of subdivision of the surfaces in between

A barrel (or tunnel) vault which follows the main longitudinal direction of the nave.

A groin vault or groined vault (also sometimes known as a double barrel vault or cross vault) is produced by the intersection at right angles of two barrel vaults

The intersection of two or three barrel vaults produces a rib vault or ribbed vault

is a form of vault used in the Gothic style, in which the ribs are all of the same curve and spaced equidistantly, in a manner resembling a fan

Load distribution

A D V A N T A G E S :• able to cover long distances and large areas of roofing.

• large spatial area in rooms

D I S A D V A N T A G E S :• are a lot more expensive to maintain and when they develop a fault

• Complex measurements and formwork are required and so they are inefficient

CATENARY CABLES STRUCTURES

CATENARY • Latin for chain• natural shape of the cable or arch by itself, but the shape changes if additional external loads are also present • are loaded continuously along their length • shape assumed by any string or cable suspended freely between two points• thin tensile member that is unable to resist compression

CATENARY CABLES STRUCTURES

PARABOLA• funicular shape of a suspension cable• loaded uniformly across its horizontal span• ignoring the weight of the cable

Three categories:

Single curvatureDouble cableDouble curvature

SINGLE CURVATURE

• consist of two or more parallel catenary cables • spanning between primary supports

DOUBLE CABLE CURVATURE

• similar to single curvature with additional of stabilizing cables below the primary one• to resist wind uplift

DOUBLE CABLE CURVATURE

• anticlastic (saddle-shaped)• the suspension cables in one direction span between supports • prevent fluttering due to wind uplift

* anticlastic : curved in opposite ways in two directions, saddle shaped

A D V A N T A G E S :• light weight• able to support heavy load• good in tension force

D I S A D V A N T A G E S :• high cost• need a continuous maintenance

MEMBRANE STRUCTURES• The structure where the exterior shell is a fabric material spread over a framework• is a membrane which carries load developed from the tensile stresses.• the structure is loaded only in tension, with no requirement to resist compression or bending forces. • the membrane can only resistforces in tension, so forces perpendicular to themembrane cause large deformations and largemembrane forces.

Types of fabric structures:

Saddle RoofMast SupportedArch SupportedPoint SupportedCombination

Masts capable of resisting compression andbuckling forces. The magnitude of forces at the point support require distribution via rings or umbrellas

Load distribution

the fabric is maintained in tension in all direction to provide stability

Stability of structures

A D V A N T A G E S :• Light weight• aesthetic effect, artistic, unique design• energy-saving and environment-friendly • are used to cover a large area for public assembly

D I S A D V A N T A G E S :• little to no rigidity• loss of tension is dangerous for stability• thermal values limit use

PNEUMATIC STRUCTURES

• a soft envelope whose internal volume is supplied with atmospheric air from pumping equipment (fans, blowers, or compressors)

• structure that stands to the imposed load through its content of air.

• Membrane structure that is stabilized by the pressure of compressed air

• The envelopes of pneumatic structures are made of industrial fabrics coated with polymers, including rubber, or from reinforced films. Threads of synthetic fibers, or less frequently glass fibers, provide the reinforcement for the films and fabrics.

Principle• Its principle is the use of relatively thin membrane supported by a pressure difference.• Through increasing the inside air pressure not only the dead weight of the space envelope is balanced, but the membrane is stressed to a point where it cannot be indented by asymmetrical loading

Two primary subsystems :Air-supported pneumatic membranes

Air-inflated pneumatic membranes

Air-supported structures• supported by internal air pressure• formed by one or more layers of continuous flexible membranes – reinforced by a grid of cable acting in tension• anchored to the ground or to a wall• The air pressure within this bubble is increased slightly above normal atmospheric pressure and maintained by compressors or fans• Air must be supplied constantly because of the continuous leakage through needed openings• Air locks are required at entrances to prevent loss of internal air pressure

Air-inflated structures • formed by inflated tubes• are advanced constructions made with two layers of material with fabric formers perpendicular in between. • they are self-supporting and self-erectable•The internal volume of building air remains at atmospheric pressure. •The pressurized air in the pillow serves only to stabilizing the load carrying membrane. The covered space is not pressurized• structure is formed by tying the tubes together to increase their strength

SHELTER

EXHIBITION

Load distribution Subject to dead loads (self weight) and live loads (snow, rain, wind, temporary applied loads)

Distribute loads to support through air-pressurized membranes.

Its stabilization is done by pre stressing the membrane either by:-• applying an external force which pulls the membrane taut• internal pressurizing if the membrane is volume enclosing

Stability of structures

A D V A N T A G E S :• lightweight• Reusable• rapid assembly and portability• the possibility of covering large spans without internal supports exhibition buildings.• complete prefabrication• transparency to light and radio waves• can create artificial environments adaptable to human use•Suitable for temporary constructions because they are as easy to dismantle and establish.•The ability for self support

D I S A D V A N T A G E S :• sometimes develop air leaks which require prompt repair

• short service life : continuous maintenance of excess pressure in the envelope

• poor fire resistance and acoustic insulation

• life-cycle cost higher : operating and maintenance