Introduction of Surface Structure

8/11/2019 Introduction of Surface Structure

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1. What is surface structure?

Surface structure is.

Structural element that is able to transfer loads primarily through membrane stresses.

A surface structure is made from a material having a very small thickness compared to

its other dimensions.

Flexible surface structures include mechanically or pneumatically pre-stressed

membranes.

Surface structure (abbreviated 'SS' and often called 'S-structure') refers to the mental

representation of a linguistic expression, derived from deep structure by transformational

rules.

Surface structure may also be made of rigid material such as reinforced concrete.

As such they may be shaped as folded plates, cylinders, or hyperbolic paraboloids, and

are referred to as thin plates or shells.These structures act like cables or arches since they support loads primarily in tension or

compression, with very little bending.

In spite of this, plate or shell structures are generally very difficult to analyze, due to the

three-dimensional geometry of their surface. Such an analysis is beyond the scope of this

text and is instead covered in texts devoted entirely to this subject.


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2. Characteristic and Types of Surface Structure

Characteristic

A surface structure is a structural element that is able to transfer loads primarily through

membrane stresses.

Surface structure may be shaped as folded plates, cylinders, or hyperbolic paraboloids,

and are referred to as thin plates or shells.

These structures act like cables or arches since they support loads primarily in tension or

compression, with very little bending.

Rigid surface structures are also called rigid shells; flexible surface structures include

mechanically or pneumatically pre-stressed membranes.

Types of Structure

Membrane structure

Plate structure

Shells structure


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1. Definition

Membranes structure are..

One sort of spatial structures made of tensioned membranes. The common membranes

include fabrics such as PVC coated polyester fabric, PVC coated glass fiber fabric and

PTFE coated glass fiber fabric.

There are also some constructions built with membrane, but it doesn't contribute to

supporting the framework.

According to different form-finding methods they can be divide into pneumatic structure,

tensile membrane structure, cable dome. In these three kinds of membrane structures

membranes work together with cables, columns and other construction members to find a

form.

Membrane structure is stabilized by the pressure of compressed air.


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2. History

This form of construction has only become well understood and widespread in large

structures in the latter part of the twentieth century.

Russian engineer Vladimir Shukhov was one of the first to develop practical calculations

of stresses and deformations of tensile structures, shells and membranes.

Antonio Gaudi used the concept in reverse to create a compression-only structure for the

Colonia Guell Church.

The concept was later pioneered by German architect and engineer Frei Otto, who first

used the idea in the construction of the German pavilion at Expo 67 in Montreal.

Steady technological progress has increased the popularity of fabric-roofed structures.

The low weight of the materials makes construction easier and cheaper than standard

designs, especially when vast open spaces have to be covered.

A very early large-scale use of a membrane-covered tensile structure is the Sidney Myer

Music Bowl, constructed in 1958.


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3. Typical Diagram

Uniform Arrangement Orthogonal Arrangement

Zigzag Arrangement

Lattice Arrangement


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4. Systems Work, Strength and Behaviour

To support broadly distributed dead load and live loads such as wind, drift forces,

ocean current, due to waves.

It should not be surprising that lightweight tension structures resemble biological

forms,since such forms also support loads by tension.

Because non-metallic materials used commonly for membranes have lower shear

strength,There often reinforced by cable nets in order to increase unsupported span length.


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Types of Membrane :

i. Pneumatic structure

Air-supported structures are supported by internal air pressure.

A network of cables stiffens the fabric, and the assembly is supported by a rigid

ring at the edge.

The air pressure within this bubble is increased slightly above normal atmospheric

pressure and maintained by compressors or fans.

Pneumatic structures are perhaps the most cost-effective type of building for very

long spans.

ii. Tensile membrane structure

A tensile structure is a construction of elements carrying only tension and no

compression or bending.

Most tensile structures are supported by some form of compression or bending

elements, such as masts (as in The O2, formerly the Millennium Dome),

compression rings or beams.

Tensile membrane structures are most often used as roofs as they can

economically and attractively span large distances .


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iii. Cable doom

The shape of doom that hanging by the cable capability.

Cables can be of mild steel, high strength steel (drawn carbon steel), stainless

steel,polyester oraramid fibers.

Structural cables are made of a series of small strands twisted or bound together

to form a much larger cable.
http://en.wikipedia.org/w/index.php?title=High_strength_steel&action=edit&redlink=1http://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Polyesterhttp://en.wikipedia.org/wiki/Aramidhttp://en.wikipedia.org/wiki/Aramidhttp://en.wikipedia.org/wiki/Polyesterhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/w/index.php?title=High_strength_steel&action=edit&redlink=1


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1.

Definition

Plates may be considered similar to beams, however:

Plates can bend in two directions and twist

Plates must be flat (or else they are shells)

Plates structure is bending in two directions. A concrete flat slab is an example of a plate.

Plates are understood by usingcontinuum mechanics,but due to the complexity involved

they are most often designed using a codified empirical approach, or computer analysis.

They can also be designed with yield line theory, where an assumed collapse mechanism

is analysed to give an upper bound on the collapse load. This is rarely used in practice.

Many of these elements can be classified according to form (straight, plane / curve) and

dimensionality (one-dimensional / two-dimensional).
http://en.wikipedia.org/wiki/Continuum_mechanicshttp://en.wikipedia.org/wiki/Continuum_mechanics


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2. History

Revolution time period and finds Euler performing free vibration analyses of plate

problems (Euler, 1766).

Chadni, a German physicist, performed experiments on horizontal plates to quantify their

vibratory modes. He sprinkled sand on the plates, struck them with a hammer, and noted

the reglular patterns that formed along the nodal lines (Chladni, 1802).

Bernoulli then attempted to theoretically justify the experimental results of Chladni using

the previously developed Euler-Bernoulli bending beam theory, but his results did not

capture the full dynamics (Bernoulli, 1789).

The French mathematician Germain developed a plate differential equation that lacked a

warping term (Germain, 1826).

Cauchy (1828) and Poisson (1829) developed the problem of plate bending using general

theory of elasticity.

Then, in 1829, Poisson successfully expanded the Germain-Lagrange plate equation to

the solution of a plate under static loading.

Some of the greatest contributions toward thin plate theory came from Kirchhoffs thesis

in 1850 (Kirchhoff, 1850). Kirchhoff declared some basic assumptions that are now

referred to as Kirchhoffs hypotheses. Using these assumptions, Kirchhoff: simplified

the energy functional for 3D plates; demonstrated, under certain conditions.


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3. Typical Diagram

Figure below shows a representative plate geometry.

Sample plate geometry showing the midplane, or middle surface, and typical Cartesian

coordinate axes.

Thin plates are usually characterized by the ratio a / h (the ratio between the length of aside, a, and the thickness of the material, h, falling between the values of 8 and 80.

Plate Structure : Reinforced concrete building construction


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A plate is a three dimensional body with

one of the plate dimensions much smaller than the other two

the curvature of the plate mid-surface in the reference configuration is zero

It is important to consider the loading as well as the slenderness of

the structure before classifying it as a plate or shell

Membrane and Bending response of Plate Structure

For a plate membrane and bending response are decoupled

For practical applications the membrane and bending response can be investigated

independently and later combined (two-surface model).


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1. Definition

Shells derive their strength from their form, and carry forces in compression in two

directions. A dome is an example of a shell.

They can be designed by making a hanging-chain model, which will act as a catenary in

pure tension, and inverting the form to achieve pure compression.

Thin-shell structures are light weight constructions using shell elements.These elements

are typically curved and are assembled to large structures.

Typical applications are fuselagesof aeroplanes, boat hulls and roof structures in some

buildings.

A thin shell is defined as a shell with a thickness which is small compared to its other

dimensions and in which deformations are not large compared to thickness.

A primary difference between a shell structure and a plate structure is that, in the

unstressed state, the shell structure has curvature as opposed to plates structures which

are flat.

Membrane action in a shell is primarily caused by in-plane forces (plane stress), though

there may be secondary forces resulting from flexural deformations.

Where a flat plate acts similar to a beam with bending and shear stresses, shells are

analogous to a cable which resists loads through tensile stresses.

Though the ideal thin shell must be capable of developing both tension and compression.
http://www.absoluteastronomy.com/topics/List_of_structural_elementshttp://www.absoluteastronomy.com/topics/Fuselagehttp://www.absoluteastronomy.com/topics/Roofhttp://www.absoluteastronomy.com/topics/Buildinghttp://www.absoluteastronomy.com/topics/Tensile_structurehttp://www.absoluteastronomy.com/topics/Tensile_structurehttp://www.absoluteastronomy.com/topics/Buildinghttp://www.absoluteastronomy.com/topics/Roofhttp://www.absoluteastronomy.com/topics/Fuselagehttp://www.absoluteastronomy.com/topics/List_of_structural_elements


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2. History

In building construction, a thin, curved plate structure shaped to transmit applied forces

by compressive, tensile, and shear stresses that act in the plane of the surface.

Shell structures are usually constructed of concrete reinforced with steel mesh. Shell

construction began in the 1920s; the shell emerged as a major long-span concrete

structure after World War II.

When World War II thin parabolic shell vaults stiffened with ribs have been built with

spans up to about 300 ft or equal as (90 m).

More complex forms of concrete shells have been made, including hyperbolic

paraboloids, or saddle shapes, and intersecting parabolic vaults less than 0.5 in. (1.25 cm)

thick. Pioneering thin-shell designers includeFelix Candela andPier Luigi Nervi.

Illustrator sketch of 1960's parabolic concrete shell building
http://encyclopedia2.thefreedictionary.com/Candela%2c+Felixhttp://encyclopedia2.thefreedictionary.com/Nervi%2c+Pier+Luigihttp://encyclopedia2.thefreedictionary.com/Nervi%2c+Pier+Luigihttp://encyclopedia2.thefreedictionary.com/Candela%2c+Felix


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3. Typical Diagram

Beijing Bird Nest Stadium, China Golden Terraces,Warsaw, Poland

Beijing Bird Nest Stadium, China Golden Terraces,Warsaw, Poland
http://www.interiordesign.net/article/CA6458388.htmlhttp://www.interiordesign.net/article/CA6458388.htmlhttp://www.interiordesign.net/article/CA6458388.htmlhttp://www.interiordesign.net/article/CA6458388.html


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A shell structure is one in which the strength reloads into the outer surface. They are

usually lighter than frame structures. For example, A turtle, an egg, an airplane, a boat, a

lobster or a car has a shell structure .

In a structure the form is very important. The resistance of the structure depends on its

form. A good example is an egg.

Test: Get an egg and place it vertically between your index finger and your thumb. Now

squeeze hard. You will see that however hard you squeeze, you will not be able to break the

egg. You can even do it with both hands, by interlacing your fingers and squeezing the egg

between them so that force is applied at both the lower and upper ends of the egg.

There are two main mechanisms by which a shell can support loads. On the one hand, the

structure can react with only in-plane forces, in which case it is said to act as a membrane.

In practice, however, real structures have local areas where equilibrium or compatibility

of displacements and deformations is not possible without introducing bending.

Local behaviour, however, is often critical in determining structural adequacy. Dimpling

in domes, or the development of the so-called Yoshimura patterns in compressed

cylinders, are phenomena related to localbuckling that introduce a new level of

complexity into the study of shells.

The theoretical limits of bifurcation of equilibrium that can be reached using

mathematical models are upper limits to the behaviour of actual structures; as soon as any

initial displacement or shape imperfection is present, the curve is smoothed.
http://www.eurocode-resources.com/buckling-a16.htmlhttp://www.eurocode-resources.com/buckling-a16.html


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Shell structures can usually be understood as a set of beams, arches and catenaries. Man-

made shell structures as used in various branches. Engineering structures and/or

architectural works whose structure is defined as Thin-shell structures from around the

world.

Localized bending stresses : -


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Surface structure can be produced by rigid material such as reinforced concrete.

Concrete structure may be shaped as folded plates, cylinders, or hyperbolic paraboloids, and are

referred to as thin plates or shells.These structures act like cables or arches since they support

loads primarily in tension or compression, with very little bending. A surface structure is a

structural element that is able to transfer loads primarily through membrane stresses. Surface

structure may be shaped as folded plates, cylinders, or hyperbolic paraboloids, and are referred to

as thin plates or shells.Types of Structures are Membrane structure, Plate structure and Shells

structure.

Membranes structure is one sort of spatial structures made of tensioned membranes. The

common membranes include fabrics such as PVC coated polyester fabric, PVC coated glass fiber

fabric and PTFE coated glass fiber fabric. Russian engineer Vladimir Shukhov was one of the

first to develop practical calculations of stresses and deformations of tensile structures, shells andmembranes. Membranes structure can support broadly distributed dead load and live loads such

as wind, drift forces, ocean current, due to waves. It should not be surprising that lightweight

tension structures resemble biological forms,since such forms also support loads by tension.

lates may be considered similar to beams, however, plates can bend in two directions

and twist and plates must be flat. Some of the greatest contributions toward thin plate theory

came from Kirchhoffs thesis in 1850 (Kirchhoff, 1850). Kirchhoff declared some basic

assumptions that are now referred to as Kirchhoffs hypotheses.A plate is a three dimensional

body with one of the plate dimensions much smaller than the other two and the curvature of the

plate mid-surface in the reference configuration is zero.


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Shells derive their strength from their form, and carry forces in compression in two

directions. A dome is an example of a shell. They can be designed by making a hanging-chain

model, which will act as a catenary in pure tension, and inverting the form to achieve pure

compression. Shell structures are usually constructed of concrete reinforced with steel mesh.

Shell construction began in the 1920s; the shell emerged as a major long-span concrete structure

after World War II. A shell structure is one in which the strength reloads into the outer

surface. They are usually lighter than frame structures. For example, A turtle, an egg, an

airplane, a boat, a lobster or a car has a shell structure .There are two main mechanisms by which

a shell can support loads. On the one hand, the structure can react with only in-plane forces, in

which case it is said to act as a membrane.


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P.M. Marcus (Author),F. Jona,Determination of Surface StructurePlenum Press; 1edition (March 1, 1984)

http://www.answers.com

http://www.britannica.com/EBchecked/topic/1382569/membrane-structure

Gould, P.L., Analysis of shells and plates, Springer Verlag, 1988

Ventsel, E., Krauthammer, T., Thin Plates and Shells: Theory, Analysis, and Applications,

CRC Press, 2001
http://www.amazon.com/s/ref=ntt_athr_dp_sr_1?_encoding=UTF8&sort=relevancerank&search-alias=books&field-author=P.M.%20Marcushttp://www.amazon.com/s/ref=ntt_athr_dp_sr_2?_encoding=UTF8&sort=relevancerank&search-alias=books&field-author=F.%20Jonahttp://www.amazon.com/s/ref=ntt_athr_dp_sr_2?_encoding=UTF8&sort=relevancerank&search-alias=books&field-author=F.%20Jonahttp://www.amazon.com/s/ref=ntt_athr_dp_sr_1?_encoding=UTF8&sort=relevancerank&search-alias=books&field-author=P.M.%20Marcus

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Introduction of Surface Structure