Structures test 3

Hanging cables structures work primarily in

Tension

A hanging cable structure is fundamentally unstable

In the sideways direction

The cable has a lack of rigidity to ensure

That the structure does not move excessively

A cable will change its profile

if the loads that are applied to it change location

Funicular structures

Structures that respond to a particular load situation by setting up pure axial forces within its elements (in tension or compression)

Polygon

Parabola

Catenary

Circular

Parabola

A funicular shape of a suspended cable loaded uniformly across its horizontal span

Catenary

A funicular shape for an unloaded cable and is determined by the self weight of the cable.

Single-curvature

Consists of two or more parallel catenary cables spanning between primary supports

Double-cable

Stabilizing cables below the primary suspension cables to resist wind uplift

Double-curvature

Anticlastic - suspension cables in one direction span between supports while the stabilizing cables run in a perpendicular direction and pull downward to prevent wind uplift

Lateral stability in the longitudinal direction is required, transverse guy cables

Single curvature

Have upper and lower sets of cables of different curvatures, pretensioned by tires or compression to make them more rigid and resistant to flutter

Double-cable structures

depth of the sag determines

The horizontal thrust that is generated

The less the sag

The greater the horizontal thrust

The greater the sag

The less the horizontal thrust

Membrane structures

Thin flexible surfaces that carry loads primarily through the development of tensile stresses

Tent structures are

Membrane structures prestressed by externally applied forces

To avoid extremely high tensile forces

A membrane structure should have relatively sharp curvatures in opposite directions

Net structures

Are membrane structures that have a surface of closely spaced cables instead of a fabric material

Cable net are

anticlastic

Shallow anticlastic tensile membranes must be

Pre-stressed

Cable net is a

Three-dimensional cable structure

when are the suspended and the arched directions of the membrane considered to share the load equally

Under gravity loading

pneumatic structures

Membrane structures that are placed in tension and stabilized by the pressure of compressed air

Domes are surfaces of

Revolution usually generated by rotating an arc of a circle around a vertical axis

A dome is similar to a rotated arch except that

circumferential forces are developed which are compressive near the crown and tensile in the lower portion.

Meridional forces are always

Compressive under full vertical loading

Hoop forces, restraining the out-of-plane movement of the meridional strips in the shell of a dome, are

compressive in the upper zone and tensile in the lower zone.

A tension ring encircles the base of a dome to

contain the outward components of the meridional forces.

Shell

A thin curved surface structure that transfers loads to supports by tension, compression and shear only

shells resist

tension

Synclastic surfaces

Doubly-curved and have similar curvature in each direction

Synclastic surfaces

Developable surfaces

Singly curved. Straight in one direction curved in the other and can be formed by bending a flat sheet.

Cones and cylinders or barrels are

Developable surfaces

Anticlastic surfaces

Doubly curved and have opposite curvature in each direction

Saddle shapes are

Anticlastic

Canoids are generated by

Sweeping one end of a straight line along a curved path and the other end along a straight line

Hyperbolic paraboloids are generated by

sweeping a convex parabola along a concave parabola of the same curvature

stresses in hypars relate to

the direction of curvature

Compression stresses

follow the convex curvature (Arch action)

Tension stresses follow

the concave curvature (Suspension action)

free form surfaces are

not mathematically derived

free form surfaces

Pure compression form

An arch

Abutment

Pier

Voussoirs

Keystone

Crown

Span

Rise

Haunch of an arch

Spandrel

Weak arches and usually used for inferior work only

Rubble arches

Rubble arch diagram

Ashlar arch

Monolithic Concrete Arch

Reinforced Concrete Arch

metal arch

Wooden arch

Rubble arches

They are made of rubble stones and can also be used as relieving arches

Wedge-shaped or tapered, joined with cement mortar and fully dressed

Ashlar arches

Stone arches

Ashlar and rubble arches

Concrete arches

Monolithic and precast

Suitable for larger spans

Monolithic concrete block arches

Precast concrete block arches

cast in molds

Tensegrity

a stable three-dimensional space where cables are continuous but struts are discontinuous and do not touch each other

An island of compression inside an ocean of tension

Tensegrity

A cable structure

Cannot bend

what needs supports at its ends that are fairly stiff

A hanging rope, Cable, or chain