Building Superstructures

5/19/2018 Building Superstructures

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Lecture 1:BUIILDING SUPER-

STRUCTURES


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Contents:

Nature of Buildings

Building Superstructures

Solid Superstructures

Skeleton Superstructures

Surface Superstructures

Advantages of Frame Structures Classification of Frames

Materials for Building Frames


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Function of Buildings

As a shelter / envelope

To meet primary physical needs

Must be well-designed as well as constructed

Building technology and building techniques are interrelated


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Functions of building

Enclose spaceso that the satisfactory internal environment may

be created relative to the purpose and intended function of the

building

The space within the building must be suitable for the

activitiesto take place with it

Comfortable, safe, stable

Must be designed in terms of size and shape, and environmental

factors


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Building Superstructures

General Definition - portion of a building that is above theground.

In Malaysian constructionrefers to the building primaryelements that transfers the building load to the sub-structure(foundations)

Mainly as the main building structuralcomponent


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Building SuperstructuresDesigned to provide:

1 . better use of structuralmaterials (steel, brick, timber, concrete etc)

2. an easier methodof construction and erection/expansion

3. reduce cost

4. answerto a particularproblem (such as provision of a clear floor area for

a warehouse or a factory)

5. conform with the requirements of the designer (architect) in search of

visual appeal (aesthetic)

6. withstandthe forcesthat the building will carry i.e. does not move in any

manner under loads


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Types of Superstructures

3 basic types of superstructure:

i) Solid

ii) Skeleton

iii) Surface


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Combines the load-carrying function with space enclosure

The loadsare transferredto and spread through the

walls/building frameto give a distributed load on the

substructure

The common types of solid structures:

i) cellular/box frame

ii) igloo

iii) cross wall


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SolidSuperstructure

TypesBox Framed Structures Load-bearing WallsCellular Box Structure

Cross Wall Structure

Igloo

Load bearing wall


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Cellular Box/Frame

the loads are transferred to the walls of the cells,

each wall being rigidly jointed to its neighbor

arrangementwhere both the internal and externalwalls are load-bearing and arranged to form a

cellular system

resulting structure is rigid and stable, suited

applications where large areas are not required or

alteration in layout are unlikely


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Cross-walls

A generic method of building

constructionusing a series of division or

party walls which transfer the floor loads

through the building to foundation or

transfer slab level.

The walls are ususlly built at standardised

centres and spacing thus allowing other

elements aslo to be standardised

division or party walls


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Load bearing walls A load-bearing wall(or bearing wall) is

a wall that bears a load resting upon it

Its weight is then transferred directly to the

foundation structure.

The materials most often used to constructload-bearing walls in large buildingsare concrete, block, or brick.

Depending on the type of building and thenumber of stories, load-bearing walls aregauged to the appropriate thickness to carrythe weight above them.


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Skeleton Structures

Comprise of a frameworkthrough which theloads are concentrated and transferred to the

supporting structure or substructure

The strength of the members of the

frameworkand their connectionsplays an

important part in the transmissionof the

applied loads

Common materials: timber, steel and

Reinforced concrete (RC)


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Skeleton Structures

Apex Frame

Rectangular Frame

Truss Frame

Portal Frame

Shed Frame

Grid Frame

Geodesic Frame

Suspension Frame


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Skeleton StructuresApex Frame

Framework of poles is jointedat or near one endto provide the

framework of a conical shape


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Apex Frame


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Skeleton StructuresRectangular Frame

A series of uprights and cross-members set up in mutually

perpendicularplanes

Provides the framework for support to the floors, walls and roofs


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Skeleton Structures

Truss Frame The truss frame a structure comprising one

or more triangular units

Constructed with straight members whose

ends are connected at joints referred to

as nodes.

External forces and reactions to those forcesare considered to act only at the nodes and

result in forces in the members which are

either tensile or compressive forces.


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Skeleton Structures

Portal Frame Portal frame construction is a method of building

and designing simple structures, primarily

using steelor steel-reinforced precast concrete

Similar to an arch, but consisting of two uprights

rigidly jointedby a horizontal, sloping or curvedthird

member

Each frame requires lateral support, usually in the

form of bracing


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Skeleton Structures

Shed Frame

Similar to portal

frame, but the third

member is in the

form of a roof truss


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Skeleton Structures

Grid Frame (Space Frames) Used for lightweight roof structure covering large

open floor areas

The frame comprises a series of triangular frames

set out in the form of a grid

The grid may be in the form of one, two or three

layers or of a space grid which comprises a six-

member frame joined to other similar frames

forming a strong rigid framework


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Skeleton Structures

Geodesic Frame Formed in the shape of a domeand comprising a

network of triangular frames in the form of spherical

triangles

i.e. portions of a sphere formed by the intersections

of great circles (great circles has a diameter equal to

that of the sphere it is drawn on)

The greater the number of triangles used in the

structure, the less the chance of collapse


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Skeleton Structures

Suspension Frame

Used in multi-storeyconstruction, it

comprises a central solid support structure

extending to the full height of the building

At the top of which a rigid horizontal

support structure is cantilevered out over

the plan area of the building


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Skeleton Structures

Functional Requirements The primary function of a skeleton frame is to carry all the loads imposed on the

building, without deforming excessively under load as a whole or in parts

Transfers all these loads to the building sub-structure (foundation)

To meet this function efficiently, it must have adequate design and construction

regarding:

i) strength and stability - appropriate materials & stiffness of joints

ii) fire resistance - for a period long enough for occupants to escape


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Surface Structures

Load carried by the roof and has thin skin

which is:

i. Sufficiently rigid to be self-supporting when

shaped and the shape provides additional

strength

ii. Sufficiently strong but flexible enough to support

load when stretched across a supporting

framework


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Surface Structures

Shell dome

Shell barrel vaultSuspension roofs and tents

Air-supported structure


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Surface Structures

Shell Dome


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Surface Structures

Barrel Vault

Both structures above use

their curved shape to obtainstrength e.g. principle of an

egg, when pressed by fingers

it will not break


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Barrel Vault

Surface Structures


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Surface Structures

Suspension Roofs & Tents

The membrane stretched oversome other skeleton framed

Form a structural component itself


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Air-Supported Structures
http://www.alibaba.com/catalog/11161717/Air_Supported_Structure.html


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Advantages of Skeleton

Frame StructureAdvantages over solid & surface structures:

1. Save in floor space

2. Flexible in plan and building operations (because of the

absence of the load bearing walls at any level)

3. Reduction of dead weight


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Classification of Frames

The building frames may be classified according to the stiffness or

rigidity of the joints between members (especially in columns andbeams)

Non-rigid frame

The nature of the joints is such that the beams are assumed to

be simply supported and the joints are non-rigid

Rigidity in the frame structure as a whole is ensured by the

inclusions of some stiffening elements in the structure, often inthe form of triangulating members bracing (normally in steel

and pre-cast concrete frame)


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Semi-rigid frame

Where some or all jointsachieved some degree ofrigidity

Normally used in steel framedbuildings where connection areof both bolt and weld)


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3. Fully Rigid Frame

- Where all joints are rigid

- Normally in steel where joints are

welded & conc. frame where

members are cast monolithically


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Choice of Structural Materials for

Building Frames1. Concrete

- Strength varies according to the mix

- Strong in compression weak in tension

- Compressive strength1/16 of steel

-Tensile strength 1/10 of its compressive strength

- Stiffness is low compared to steel

2. Steel

-Very strong and stiff

- Strong both in compression and tension

- Relatively economical

- Non-combustible; but at 427 C482 C it will lost strength


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Factors that Influence the Choice of Building Frame

Structural Materials

i. Availability of materials and labours

ii. Cost

iii. Speed of erection

iv. Possibility of standardizing the size of structural members

v. Size and nature of site

vi. Fire resistance required

Documents

Building Superstructures