Advanced construction and materials

Unit – IIClass -5B.Arch VII sem Section – A & B

Folded plates

Folded structures are three-dimensional

structures - spatial structures and they

belong to the structural systems.

The term folded structure defines a folded form

of construction, including structures derived

from elements which form a folded

structure by their mutual relationship in

space.

There are different ways of constructing folded

structure in terms of their forms and the

application of different materials they are

made of.

History of folded plates

Design and construction of

folded structures occurs at the

beginning of the twentieth

century, and is associated with

the development of reinforced

concrete .

The basic idea of creating this

type of construction is striving

to achieve more constructive

height and greater rigidity

and reduce the net weight of

the structural element.

History of folded plates… Engineer Eudene Freyssinet performed

the first roof with the folded structure

in 1923 as an aircraft hangar at Orly

Airport in Paris.

In technological terms this folded

construction is made of prefabricated

elements, with pre-stressed structure,

which is a remarkable engineering

undertaking of the time .

Based on the application of this pre-

stressed structure Eudene Freyssinet

has been called "the father of pre-

stressed concrete.

About folded structures

Folded structures - the most cost-

effective constructions, they use

less material because of their high

stiffness in the plane of maximum

bending in the direction of the range.

Folded structures differ in:

geometric form, the form of a

base over which they are performed,

the manner of performance,

methods of forming stiffness,

function and position in the

building, and the material they

are made of.

Types of folded structuresBased on geometric shape folded structures can be divided into :

folded plate surfaces,

folded plate frames,

spatial folded plate

structures.

Types of folded structures

The shape of folded structures

affects the transmission of

load and direction of relying

of folded structures.

Based on these parameters we

can do the division in :

linear folded plate structure,

radial folded plate structure,

spatial folded plate

structure.

Folded Plate RoofsWith a number of folds folded plate roofs can be looked as slab. These roofs are also called as, prismatic shells, hipped plates and faltwerke.

In these structures bending is also reduced and lot of load gets transferred as membrane is in compression.

On the other hand folded plates are not as efficient as shells.

Given figure shows typical folded plate roofs.

Folded plates principle

Construction of thin, flat elements of concrete,

steel ,timber etc which are connected rigidly

at angles with each other forming a cross

section which is capable of carrying a load

over a large span.

Folded plates are assemblies of flat plates

rigidly connected together along their

edges in such a way so as to make the

structural system capable of carrying loads

without the need for additional supporting

beams along mutual edges.

Folded plates principle…

Folded plates principle..

The design of folded plate roof

structures is much simpler because

the elements are all essentially

beams.

Folded plate-north light is usually achieved for this roof

BASIC ELEMENTS

They consist of :

1) the inclined plates,

2) edge plates which must be used to stiffen the wide plates,

3) stiffeners to carry the loads to the supports and to hold the

plates in line, and

4) columns to support the structure in the air.

The structure above may have a simple span, as shown, or multiple spans of varying length, or the folded plate may cantilever from the supports without a stiffener at the end.

Folded structures made of reinforced concrete Concrete is the most commonly applied material for creases. A large

number of authors define folded construction as the construction made only from reinforced concrete.

The reason for this statement is the fact that most of the folded structures are made of this material.

Most commonly applied form of the crease is a "V" shape whose static height depends on the range and load.

If the dimensions of folded plates are not limited. We can get a great variety of types.

Shell structures- Introduction

The family of shells

Types of shells

Long span domes

What are vaults

Shell arches

Dome shells

Curved roof Applications

Sandwich shell materials

construction

Typical materials for shells

Beams and shells

Future work

Short Shell structures 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.

• An architectural problem of the short

shell structure is the proper design

of the end walls.

• On a long span structure there will be

large blank areas that require careful

architectural treatment to make

the structure pleasing.

Types of shells:1.Barrel vaults2.Short shells

Barrel vaults: Length of the barrel is longer in comparison to

the width.

Short shells: A cylindrical shell having a large radius in

comparison to the length

TYPE OF SHORT SHELLS:

PURE ARCH AND SHELL CANTILEVER ABUTMENT MASSIVE ABUTMENT RIGID FRAME

The principle parts of a short shell structure are: The abutment. The arch structure. The shell spanning between arches.

An edge beam may be provided at the springing level of the

shell for additional support.

This edge beam can be omitted in small structures if the

shell is thickened.

The short shell carries loads in two ways:

1. As an arch carrying load to the lower elements.

2. As a curved beam to the arches.

The thickness of the shell can be quite thin due to these

properties.

• The short shell serves only a minor role.

• The emphasis is on the arch shape.

• Many structures built with short shells, such a large

hangars and auditoriums, could have been built with little

more dead load by using a ribbed slab or other

lightweight concrete framing system rather than the

shell.

The architecture of short shells is based on the

exploitation of the shape of the arch rather than

on the shell itself.

Variation of thickness along the section

Shells and folded plates

FEW EXAMPLE

FEW EXAMPLE

FEW EXAMPLE

Geometrical Stairs. The most complicated and most

expensive stairways are those that are curved, commonly known as the geometrical stairway.

The geometrical stairway is a winding stairway, but it is so designed that the tread at the line of travel of all steps is the same width.

These staircases may be circular or elliptical and often are designed with landings to insure ease in ascending them.

A geometric staircase is generally the focal point of a house, with it's sweeping curves and flowing lines it becomes a piece of art to enhance any building.