FEM103 Construction Technology Revision Notes PDF

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Revision notes for May 2017 paper....

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FEM103 Construction Technology Revision Notes Study Unit 1 – Introduction

1

Structural Behaviour of Buildings 1) Different types of loadings 

Dead loads: the entire weight of the building itself which includes all the structural elements such as the walls, floors and the like.



Live loads: the expected weight of the occupants and the possessions such as furniture, fittings and the like.



Wind loads: this is an important factor to consider for tall buildings with large surface area.

2) These loads (or forces) may be 

Distributed over the full length or area of a structural member of a building or



They may be concentrated or point loads if the loads are applied at a single point or within a small area.

3) These forces may act on the building and its elements in vertical, horizontal or oblique directions, resulting in different types of effects such as: 

physical sliding movements,



tendency to overturn,



crushing and/or deformation.

Different types of loadings on a structural member of a building may cause: 1) Different types of stress on that member 

stretching (tensile force)



compressing (compressive force),



sliding (shear force)



twisting (torsional force)

2) Changes in length of the structural member, which is also known as strain 3) Turning or rotating motions, also called moments.

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2

Site Analysis Objectives: 1) Assess the viability of the project from the client’s perspective 2) Identify the most appropriate position for the building by avoiding or accommodating identified problems while making the best possibe use of the physical features on site and environmental conditions 3) Design the most suitable foundation system and service provisions 4) Ensure that safe construction methods are adopted 5) Identify the most suitable ways of dealing with any contaminants and problem material

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3

Types of Survey 1) Condition Survey 2) Land Survey 3) Photogenic Video Survey

4

Causes of ground movements that may lead to building settlement 1) Compression of the soil by load of the building 2) Seasonal volume changes in the soil 3) Mass movement due to unstable grounds 4) Grounds made unstable by adjacent excavations or by dewatering

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Study Unit 2 – Foundation Chapter 1 - Foundation 1

Shallow Foundation 1) Shallow foundations are those that transfer the load of the building directly to the earth at the base of the footing. 2) Each footing takes the concentrated load of the column and spreads it out over a large area, so that the weight on the soil does not exceed the safe bearing capacity of the soil. 3) They generally include individual pad footings, strip footings and raft foundations.

2

Deep Foundation 1) Deep foundations are those that transfer the load of the building to a layer of stronger soil or rock that is below the weak layer at the surface. 2) They include the different types of piles.

3

Shallow Foundation

3.1

Strip Foundations 1) Strip foundations consist of a continuous strip, usually of reinforced concrete, formed centrally under load bearing walls. 

Bearing capacity of the soil should be greater than the loads imposed by the building foundation.

2) Width of concrete strip foundation depends on the carrying capacity of the soil and the load on the foundation: 

the greater the bearing capacity of the soil, the lesser the width of the concrete strip foundation and vice versa.

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

If the thickness of the concrete strip foundation (without steel reinforcement) were less than its projected side of the wall, the concrete foundation might suffer shear failure caused by the weight of the wall.

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Accommodating tensile forces within strip foundations

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3.2

Pile Foundation 1) Pad foundations are designed to point loads. 2) They can also be designed such that the loads of the walls and the buildings are transferred through ground beams that rest on the pad foundations. 3) Pad foundations transfer the loads to a lower level where the soil is cable to carry the transmitted loads.

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3.3

Raft Foundation 1) A raft foundation consists of a raft of reinforced concrete under the whole building. 2) Normally used for buildings on compressible grounds. 3) The concrete raft is of uniform thickness and reinforced top and bottom against both upward and downward bending forces.

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3.4

Pile Foundation

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Chapter 2 - Floor 4

Functional Requirements of Floors 1) Strength and stability 

Depends on the characteristics of the materials being used for the structure of the floor.



Strong enough to carry the dead loads and anticipated live loads of the buildings.



To provide a horizontal surface, floors should have adequate stiffness to minimize deflections.



Should remain stable and horizontal under the dead and live loads of the building.



If necessary, the floors should also be able to support and accommodate services either in its depth, below or above the floor, without affecting its stability.

2) Resistance to weather and ground moisture 3) Durability and freedom from maintenance 4) Fire safety 

Resisting spread and passage of fire and providing stable support for occupants to evacuate

5) Resistance to passage of heat 6) Resistance to passage of sound 

Upper floors should act as a barrier to the transmission of sound.

5

Types of Floor Slabs

5.1

Ground Supported Concrete Slab

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1) Hardcore 

Provides stable bed for the concrete slab



Made up of materials such as: Crushed and Graded bricks / Tile Rubber, Gravel and Crushed Hard Rock / Concrete Rubble



Not readily absorb water



Insufficient of hardcore bed causes settlement cracking

2) Binding layer 

The layer that is applied on top of hardcore (before laying the concrete)



50mm thick of dry concrete / sand



Provide a smooth surface to lay damp-proof member



Prevent moisture from entering the hardcore layer

3) Damp-Proof Member (DPM) 

A barrier to prevent moisture from entering the building



Form a continuous layer to prevent moisture rising between edges of the slab and walls



Materials used as damp-proof membranes must be impermeable to both water in liquid and vapour form. (Materials eg. Polythene / Polyethylene sheets, recycled polyethylene sheets, bitumen)



Should be strong enough to withstand any accidental damage (eg puncture)

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5.2

Suspended Concrete Floor Slab

1) Usually form suspended concrete floor slab when the ground: -

is sloping Page 12 of 57

-

has poor bearing capacity

-

is liable to volume changes

2) Suspended concrete floors can be constructed using: -

precast reinforced concrete slabs

-

block and beam floor systems

-

in-situ reinforced concrete slabs

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Alternative arrangements for Beam and Block floors:

3) Floor Screeds -

Usually a wet sand-cement mix.

-

Provided to ensure surface to which a floor finish may be applied

-

Floor finishes means the materials that are being applied to a floor surface as a finished surface (Materials eg. Titles, woodblocks, rubbersheets)

-

Lay the screed after concrete floor has dried and hardened to prevent damaging it.

4 Types of screeds: 1) Bonded Screed

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2) Semi-Bonded Screed

3) Un-Bonded Screed

4) Floating Floor

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5.3

Suspended Timber Ground Floors

1) Sleeper walls 

Half-brick walls built directly 1.8 metres apart with gaps in the brickwork to allow free circulation of air below

2) Wall plate 

A continuous length that is softwood timber that place along the length of a wall



Provide a firm level surface to support the timber floor joist and to which the floor joists can be nailed to



Spreads the point loads from joists uniformly along the wall below

3) Floor Joists 

Rectangular sections of sawn softwood timber laid at regular intervals to carry the loads transmitted by the floor boards and transfer these loads to the supporting walls

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4) Floor Surface 

Formed by timber floorboards, medium density fibre (MDF) boards or plywood boards



Floorboards are cut with a projecting tongue on one end and a grove on the opposite edge and cramped together before being nailed to the joists to form a firm and level surface

5) Thermal Insulation 

The most practical method is to fix the insulating materials between the joists

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5.4

Reinforced Concrete Upper Floors

1) Precast ‘T’ beam and infill block floor 

Provides resistance to fire and air-borne sound



Usually use for smaller spans and loads

2) Hollow beam floor units

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3) Monolithic reinforced concrete floor 

A monolithic reinforced concrete floor is a continuous unbroken solid mass of various thickness, cast in-situ and reinforced with steel bars



To support the concrete while it is still wet and plastic after casting, formwork is used as temporary support

4) Steel ‘rib-deck’ concrete floors 

Profiled cold rolled steel decking is often used as permanent formwork



Profiled steel is placed between to support the walls and beams.



The profiled steel formwork becomes mechanically bonded to the concrete after the concrete was set



It also acts as reinforcement to concrete floor

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5.5

Timber Upper Floors

1) The strength and stability of a timber upper floor depends on the depth of the floor joists used.

2) It is convenient to use a steel or timber beam to provide intermediate support for the timber joists when the span of timber floor is greater than the length of timber available.

3) Maintain joists in the vertical position in which they were initially fixed, and timber strutting is used.

4) For stability, at the end of floor joists must have adequate support from walls or beams.

5) Joist hangers can also be used to build in the ends of timber joists as an alternative method.

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6) Notches and holes are usually cut into timber joists so that electric cables, water and gas pipes can pass through

5.6

Precast Prefabricated Construction 

Prefabrication is the practice of assembling components of a building structure in a factory off site and transporting the complete assembled components to the construction site where the structure is to be installed.



Precast concrete is a construction product produced by casting concrete in a reusable mould or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place.

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

1

Study Unit 3 – Walls

Functional Requirements of Walls 1) Strength and stability 

Determined by the type of materials used and the manner in which they are put together.



The safe working strength of the materials used is always considerably less than the ultimate strength in order to provide a factor of safety against variations in the strength of materials and their behavior under stress.



Stability of walls may be affected by:

–

movement of the foundations,

–

eccentric loading,

–

lateral forces such as wind,

–

expansions caused by temperature and moisture changes.

2) Resistance to weather and ground moisture

3) Durability and freedom from maintenance 

Ability of the wall to maintain its expected functional performance and acceptable appearance with least maintenance

4) Fire safety 

Provide fire protection from occupants



Two main principal considerations in wall designs:



-

structural integrity of the wall

-

surface spread of flame in a fire

Fire door should be able to resist collapse for a minimum of time

5) Resistance to the passage of heat 

Heat transfer through enclosed walls, roofs and floors.



By Conduction, Convection and Radiation

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6) Avoid condensation on the cold internal surface of walls

7) Resistance to airborne and impact sound 

Sound is transmitted as airborne sound and impact sound



Airborne is generated by cyclical disturbances of air (eg. Radio)



Impact sound is caused by contact with a surface (eg. Slamming a door)



Most effective insulation against airborne sound is a dense barrier (eg. Solid wall)



The denser the material, the more readily it will transmit impact sound



Absorbent (spongy) materials are needed to cushion the impact to interrupt the sound path

8) Security 

Walls, doors and windows help to provide a secure enclosure for the buildings



Commercial premises especially containing goods, forced entry to occur through walls and roofs

9) Aesthetics 

Walls form a visually important part of the overall building design and contribute to the character of the building



Choice of materials will depend on the functional and performance requirements or aesthetic goals of the client or designer

2

Damp-Proof Courses (DPC) 1) Act as a barrier to the passage of moisture between the parts being separated by DPC. 2) Commonly used materials 

Flexible materials (eg. Bitumen felts and plastic sheets)



Semi-rigid materials (eg. Asphalt and mastic)



Rigid materials (eg. Lead, copper, bricks, stones and slate)

3) Function of a DPC laid over wall thickness is to act as a barrier to the passage of moisture between the parts being separated by DPC 4) Where it is laid over larger areas, as in a floor, it is known as a Damp Proof Membrane (DPM)

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2

Stone and Stone Masonry Walls 1) Masonry is the term used for construction that involves individual units of bricks, stones and concrete blocks with mortar as a binding material. 2) Mortar is a mixture of cement, sand, lime and water. Mortar is a binding material that binds individual units together horizontally and vertically. 3) Masonry walls provides strength, durability and character to the structure. 4) Helps to keep the elements out and control he indoor and outdoor temperature.

2.1

Natural stones 1) Natural stones are used as a facing material bonded or fixed to a backing of brickwork or concrete. 2) Natural stones used in building can be classified as: 

Igneous (eg. Granite and basalt)



Sedimentary (eg. Lime stones and sandstones)



Metamorphic (eg. Slates and marble)

3) Stones generally has:

3



Considerable compressive strength



Highly durable as a walling material



Strong fire resistance



Dense stone such as granite does no absorb moisture easily

Type of Stone Walls 1) Rough or smooth finished 2) Irregular shaped and used as it is with blemishes such as cracks 3) Finished stones are put through a process of buffing, sanding and shaping 4) Walls made from finished stones have smooth and unified appearance, like a brick wall

3.1

Dry Stone Walls 1) It is constructed by stacking rocks in layers and rows. Help to keep the wall from shifting with the weight 2) They are assembled without the use of mortar 3) In a mortared wall, individual stone is sealed and bonded by the use of cement and sand mortar between each rock 4) They are more durable, but more labour intensive

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4

Bricks and Brickwork

4.1

Types of Bricks 1) Clay bricks 2) Concrete bricks 3) Calcium silicate bricks (sand-lime)

4.2

Bricks classifications

Types of Bricks

Common

Engineering

Facing

1) Common bricks 

Lower compressive strength and quality than engineering or facing bricks as no attempt to control the colour, texture or appearance



Not be used below ground level



No special attractive appearances

2) Engineering bricks 

Made from selected clay which have been carefully prepared and burned so that the finished brick is solid and hard



Mainly used for walls carrying heavy loads



Dense and strong as they are produced at extremely high temperature



Used as damp-proof materials



Chemical resistant and poor water absorption

3) Facing bricks 

Wide range as it includes any brick which is sufficiently hard to carry normal loads and have a pleasant appearance



Hard-burned and possess greater strength and durability to withstand all kinds of weather and environmental conditions



Mainly used for aesthetic purposes for attractive exterior

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4.3

Physical Properties of Bricks 1) Performance criteria: Durability, size and type, comprehensive strength, frost resistance, soluble salt and visual appearance 2) Comprehensive strength 

Crushing resistance varies from 3.5 N/mm2 for soft facing bricks up to 140 N/mm2 for engineering bricks

3) Water absorption and suction 

The level of water absorption is most critical for bricks below the dpc or the dpc to be used

4) Thermal and moisture movement 

Allowance must be made fo...