PREPARED BY :

NOR AZAH BINTI AZIZKOLEJ MATRIKULASI TEKNIKAL KEDAH

2.0 ANALYSIS AND DESIGN2.2 STRUCTURAL ELEMENTS

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Load Paths

• The load path is simply the direction in which each consecutive load will pass through connected members.

• The sequence commences at the highest point of the structure working all the way down to the footing system, ultimately transferring the total load of the structure to the foundation.

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Load Paths

• Ultimately, the lowest structural member must be strong enough to support all members above it.

• This is why engineers often design the uppermost members first and progressively work their way down the structure following the load path.

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RAFTER

PURLIN

GROUND SLAB

STUMP

FOUNDATION

COLUMN

ROOF BEAM

ELEVATED SLAB

ROOF SHEET

GROUND BEAM WALL

Load analysis distribution and path

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Load Path Components in a Concrete structure

• Part of the load path in a typical multi-storey reinforced concrete structure is made up of the following components.

MAIN BEAMS

COLUMN

FLOOR SLABS

SECONDARY BEAMS

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Load Path in a Domestic Structure

The direction that loads are transferred through a structure is important and must be identified.

A simple domestic structure works on similar principles as a large concrete structure although the components are different:- the foundation supports the footings

- the footings support the flooring structure which consist of bearers, joists and flooring - the stud walls and bracing transfer their load to the flooring - the roof trusses support the battens which support the roof cladding and this load is transferred to the walls.

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Load Path• A diagram shows the

framing of the roof, wall, floor, footing and foundation of a building.

• The load of the path is shown in the diagram.

ROOF

WALL

FLOOR

FOOTING

FOUNDATION

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Load Path

STRUCTURALCOMPONENT

LOAD PATH

Roof Roof load are transfer to roof beam

Wall Wall load is transfer to beam

Floor Slab Carry direct applied load and transfer it to beam

Beam Carry load from floor slab and transfer it to column

Column Carry load from beam and transfer it to foundation

Foundation Carry and distribute building load to soil beneath

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Nature of Load- Point Load

• A point load - often abbreviated to P or L- is a load acting at a single point. - sometimes called a concentrated load.

• Example;- Roof truss supported on a top plate - As the contact area of a truss on the top plate is small, the load is assumed to be concentrated at a point.

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Nature of Load- Point Load• A diagram shows a plank of timber

appearing horizontally above a roof truss.

• At the end of the plank is an arrow showing the information P or L units kN.

• On either side of the roof truss is a top plate.

• Where the top plate and roof truss intersects is a an arrow indicating P or L.

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Nature of Load- Uniformly Distributed Load

• A uniformly distributed load (UDL) - is a load that is evenly spread along a length or across an area.

• For example, the loads supported by a typical beam include:• the beam’s own weight• the weight of the floor slab it is supporting• the live load supported by the floor slab.

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Nature of Load- Uniformly Distributed Load

• These loads are consistent along the entire length of the beam.

• The load may be represented as ;i) rate per linear metre (kN/m) for beamsii) rate per square metre (kN/m2) for slabs.

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Nature of Load- Uniformly Distributed Load

• A diagram shows a beam with the load distributed all along its length.

• The load is labelled UDL with units shown as kN/m or kN/m2.

• A reinforced concrete beam is displayed and labelled with UDL equal to 4.3 kN/m.

• A reinforced concrete slab is displayed and labelled 2.7 kN/m2.

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Nature of Load- Uniformly Varying Load

• A uniformly varying load - is a load that is distributed along the length of a linear element such as a beam, but instead of the load being evenly spread it varies in a linear fashion.

• Example ; Retaining wall. - is designed to hold back earth, which exerts a horizontal force on the back of the retaining wall.

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Nature of Load- Uniformly Varying Load

• A diagram shows a vertical section through a retaining wall.

• The retaining wall is in the shape of an upside down ‘T’. The earth to the left of the wall is labelled ‘retained earth pushes horizontally at back of wall’.

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Nature of Load- Uniformly Varying Load

• A diagram shows a symbolic representation of a uniformly varying load on a retaining wall.

• This shows a number of arrows pointing to the right. The length of these arrows indicates the strength of the load on the wall at different heights.

• The load is smallest at the top of the wall and greatest at the base of the wall.

• A right angled triangle is drawn around these arrows to further illustrate this point.

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• Moments are a measure of the turning effect of a force around a specified turning point or pivot.

• A moment is a force times a distance. The unit used to measure a moment is newton metres (Nm).

Nature of Load- Moments

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M = F x d

M = 10 N x 5 m

M = 50 Nm

Note that the units are Nm (newton metres) not N/m (newtons per metre).

Nature of Load- Moments

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• The direction of a moment is opposite to the direction of the force

Nature of Load- Moments

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• The convention is that:• clockwise moments are positive • anti-clockwise moments are negative.

Nature of Load- Moments

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MAIN BEAMSARE SUPPORTED BY COLUMN

BACK

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COLUMNARE ARRANGED IN A GRID PATTERN

BACK

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SLABSARE SUPPORTED BY THE MAIN BEAMS

BACK

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SECONDARY BEAMSARE SUPPORTED BY

THE MAIN BEAMS

BACK

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RoofThe roof load path flows

down through the walls to the foundation.

BACK

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WallThe wall load path flows

down through the floor to the foundation.

BACK

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FloorThe floor load path flows down through the footing

to the foundation.

BACK

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FootingThe footing load path

flows down through to the foundation.

BACK

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FoundationThe foundation

supports the footings.

BACK

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