1.0INTRODUCTION

to STRUCTURES

Objectives:

1.Name types of forces.2.Name types of loads.3.Distinguish characteristics of

primary materials in main structural construction.

At the end of the lesson, students will be able to:

What is forces?Definiton:

Any influence that causes an object to undergo a certain change, either

concerning its movement, direction, or geometrical

construction.

Do you know the types of forces?

TENSION FORCE (daya regangan)Types Of Forces:

1Tension refers to when a force is applied that pulls

outward against the face of a structural element and

stretches it (e.g., stretching a rubber band).

COMPRESSION FORCE (daya mampatan)Types Of Forces:

2Compression represents when a force is applied

inward against the face of a structural element, thereby

shortening it.

SHEAR FORCE (daya ricihan)Types Of Forces:

3Shear is when a force is applied

in parallel to the face of a structural element at an angle that is perpendicular to either

compression or tension forces.

LOADS

1. Dead load

2. Live load

3. Wind load

4. Seismic load

Dead load What it means:Forces incurred due to the weight of all the materials used in the construction of a home.E.g: Roof, ceiling, floor, wall & partition.

What it affects:• A constant over the life

of the structure.• Big impact on the long-

term deflection/creep of framing members.

Live load What it means:Produced by the users of a home.E.g:People, furniture, storage items.

What it affects:• Exert force on almost

all of a house’s framing components.

• Goal: To design floor systems that limit deflection & vibration.

Wind load What it means:+ve @ -ve pressures exerted on a house when it obstructs the flow of moving air.

Act perpendicular to the surfaces of a house

What it affects:• Depends on: location,

height, roof pitch.• Most sig. impact: roof

framing, overhangs, large openings.

Seismic load What it means:The inertial forces acting on a house due to earthquake-induced ground motions.

Act horizontally on each element of the structure & are proportional to their mass.

What it affects:• All components of a

frame.• Shear-resisting elements

are most affected

Do you know the

characteristics of primary

materials in main structural construction?

1 1. TIMBER• The oldest of structural materials.• The properties of timber are non-linear and

very variable, depending on the quality, treatment of wood, and type of wood supplied.

• Wood is strong in tension and compression, but can be weak in bending due to its fibrous structure.

• Reasonable cost, ease of working, attractive appearance and adequate life if protected from moisture and insects.

• Wood is relatively good in fire as it chars, which provides the wood in the centre of the element with some protection and allows the structure to retain some strength for a reasonable length of time.

22. BRICKS

• A brick is a block, or a single unit of a ceramic material used in masonry construction, usually stacked together, or laid using various kinds of mortar to hold the bricks together and make a permanent structure.

• Made from: Various kiln-baked clay and shale mixtures.

• Typically produced in common or standard sizes in bulk quantities.

• Burnt-clay bricks have good resistance to moisture, insects and erosion, and create a good room environment.

• They are moderate in cost and have medium to high compressive strength.

• Long lasting

3 3. CONCRETE• Made by: Mixing cement paste

(portland cement & water) with aggregate (sand & stone).

• Concrete is used extremely widely in building and civil engineering structures, due to its:

Low cost, flexibility, durability, high strength, high resistance to fire, strong in compression, hardness, imperviousness and mouldability.

• Flaws: Very weak in tension.

1.Reinforced concreteReinforced concrete is concrete in which steel reinforcement bars ("rebars"), plates or fibers have been incorporated to strengthen a material that would otherwise be brittle. In industrialised countries, nearly all concrete used in construction is reinforced concrete. Due to its weakness in tension capacity, concrete will fail suddenly and in brittle manner under flexural (bending) or tensile force unless adequately reinforced with steel.

2. Prestressed concretePrestressed concrete is a method for overcoming the concrete's natural weakness in tension. It can be used to produce beams, floors or bridges with a longer span than is practical with ordinary reinforced concrete. Prestressing tendons (generally of high tensile steel cable or rods) are used to provide a clamping load which produces a compressive stress that offsets the tensile stress that the concrete compression member would otherwise experience due to a bending load.

4 4. STEEL• Iron alloy with between 0.2 and 1.7%

carbon.• Steel is used extremely widely in all types of

structures, due to its: Low cost, high strength to weight

ratio, speed of construction, strong in tension and compression.

Flaws: Weak in fires, very prone to corrosion (rust).

• Steel is a ductile material, which will behave elastically until it reaches yield (point 2 on the stress-strain curve), when it becomes plastic and will fail in a ductile manner (large strains, or extensions, before fracture at point 3 on the curve).

Stainless steel• An iron-carbon alloy with a minimum of 10.5% chromium content. • There are different types of stainless steel, containing different proportions of iron,

carbon, molybdenum, nickel. It has similar structural properties to steel, although its strength varies significantly.

• It is rarely used for primary structure, and more for architectural finishes and building cladding.

• It is highly resistant to corrosion and staining.