Post on 19-Jan-2016
TOPIC 1.3TOPIC 1.3
RESPONSE OF CIVIL ENGINEERING PROJECT
BY:NOR AZAH BINTI AZIZ
KOLEJ MATRIKULASI TEKNIKAL KEDAH
BY:NOR AZAH BINTI AZIZ
KOLEJ MATRIKULASI TEKNIKAL KEDAH
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Learning OutcomesLearning Outcomes
Identify and describe material response of modes primary failure due to:A) Concrete
i. Structure failure● Compressive● Tensile● Shear.ii. Performance failure● Creep● Shrinkage
Identify and describe material response of modes primary failure due to:A) Concrete
i. Structure failure● Compressive● Tensile● Shear.ii. Performance failure● Creep● Shrinkage
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CONCRETECONCRETE
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• Concrete is a construction material composed of cement (commonly Portland cement), coarse aggregate, fine aggregate, water and admixture.
• The cement and water form a paste that hardens and bonds the aggregates together.
• Concrete is the most widely used construction material in the world.
• Concrete is a construction material composed of cement (commonly Portland cement), coarse aggregate, fine aggregate, water and admixture.
• The cement and water form a paste that hardens and bonds the aggregates together.
• Concrete is the most widely used construction material in the world.
CONCRETECONCRETE
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• Concrete has strength, durability, versatility, and economy.
• It can be placed or molded into virtually any shape and reproduce any surface texture.
• Concrete has strength, durability, versatility, and economy.
• It can be placed or molded into virtually any shape and reproduce any surface texture.
CONCRETECONCRETE
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Concrete Structure Failure
i) Compressiveii) Tensileiii) Shear
i) Compressiveii) Tensileiii) Shear
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What is the Compressive Strength(CS)?
What is the Compressive Strength(CS)?
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Introduction
• Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength.
• When a specimen of material is loaded in such a way that it extends it is said to be in tension. On the other hand if the material compresses and shortens it is said to be in compression.
• Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength.
• When a specimen of material is loaded in such a way that it extends it is said to be in tension. On the other hand if the material compresses and shortens it is said to be in compression.
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• On an atomic level, the molecules or atoms are forced apart when in tension whereas in compression they are forced together. Since atoms in solids always try to find an equilibrium position, and distance between other atoms, forces arise throughout the entire material which oppose both tension or compression.
• the compressive strength of a material is that value of uniaxial compressive stress reached when the material fails completely
• usually obtained experimentally by means of a compressive test.
• On an atomic level, the molecules or atoms are forced apart when in tension whereas in compression they are forced together. Since atoms in solids always try to find an equilibrium position, and distance between other atoms, forces arise throughout the entire material which oppose both tension or compression.
• the compressive strength of a material is that value of uniaxial compressive stress reached when the material fails completely
• usually obtained experimentally by means of a compressive test.
Introduction
compression9
• The major difference between the two types of loading is the strain which would have opposite signs for tension (positive—it gets longer) and compression (negative—it gets shorter).
• Another major difference is tension tends to pull small sideways deflections back into alignment, while compression tends to amplify such deflection into buckling.
• The major difference between the two types of loading is the strain which would have opposite signs for tension (positive—it gets longer) and compression (negative—it gets shorter).
• Another major difference is tension tends to pull small sideways deflections back into alignment, while compression tends to amplify such deflection into buckling.
Introduction
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What is the Compressive Strength(CS) of Concrete?
• Concrete mixtures can be designed to provide a wide range of mechanical and durability properties to meet the design requirements of a structure.
• The compressive strength of concrete is the most common performance measure used by the engineer in designing buildings and other structures.
• CS is measured by breaking cylindrical concrete specimens in a compression-testing machine.
• Concrete mixtures can be designed to provide a wide range of mechanical and durability properties to meet the design requirements of a structure.
• The compressive strength of concrete is the most common performance measure used by the engineer in designing buildings and other structures.
• CS is measured by breaking cylindrical concrete specimens in a compression-testing machine.
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compression tests of cylinders of concrete which are crushed 28 days after they are made.
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• CS is calculated from the failure load divided by the cross-sectional area resisting the load (pound-force per square inch (psi) in US) and Customary units or megapascals (MPa) in SI units.
• Concrete CS requirements can vary from
2500 psi (17 MPa) for residential concrete to 4000 psi (28 MPa) and higher in commercial structures.
• Higher strengths up to and exceeding 10,000 psi (70 MPa) are specified for certainapplications.
• CS is calculated from the failure load divided by the cross-sectional area resisting the load (pound-force per square inch (psi) in US) and Customary units or megapascals (MPa) in SI units.
• Concrete CS requirements can vary from
2500 psi (17 MPa) for residential concrete to 4000 psi (28 MPa) and higher in commercial structures.
• Higher strengths up to and exceeding 10,000 psi (70 MPa) are specified for certainapplications.
What is the Compressive Strength(CS) of Concrete?
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What is the Compressive Strength(CS) of Concrete?
Compressive strength. The amount of force a material can support in a single impact
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• Compressive strength test results are primarily used todetermine that the concrete mixture as delivered meets therequirements of the specified strength in the jobspecification.
• Strength test results from cast cylinders may be used forquality control, acceptance of concrete, or for estimating the concrete strength in a structure for the purpose ofscheduling construction operations such as form removalor for evaluating the adequacy of curing and protectionafforded to the structure.
• Compressive strength test results are primarily used todetermine that the concrete mixture as delivered meets therequirements of the specified strength in the jobspecification.
• Strength test results from cast cylinders may be used forquality control, acceptance of concrete, or for estimating the concrete strength in a structure for the purpose ofscheduling construction operations such as form removalor for evaluating the adequacy of curing and protectionafforded to the structure.
Why is Compressive Strength(CS) Determined?
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Fractured Test Specimen at Failure
Why is Compressive Strength(CS) Determined?
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• Concrete structures, except for road pavements, are normally designed on the basis that concrete is capable of resisting only compression, the tension being carried by steel reinforcement.
• Concrete structures, except for road pavements, are normally designed on the basis that concrete is capable of resisting only compression, the tension being carried by steel reinforcement.
Why is Compressive Strength(CS) Determined?
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• applies to materials resulting in their compaction (decrease of volume).
• When a material is subjected to compressivestress then this material is under compression.
• Usually compressive stress applied to bars, columns, etc. leads to shortening.
• applies to materials resulting in their compaction (decrease of volume).
• When a material is subjected to compressivestress then this material is under compression.
• Usually compressive stress applied to bars, columns, etc. leads to shortening.
What is Compressive Stress?
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Tension
Compression
Loads
Component action
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Modes of failure of standard concrete cylinders
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What is Tensile Strength?
•Concrete has substantial strength in compression, but is weak in tensile.•The Tensile strength of concrete is roughly 10% of its compressive strength•Nearly all reinforce concrete structures are design on the assumption that the concrete does not resist any tensile forces.•Tension will create cracking of the concrete.
•Concrete has substantial strength in compression, but is weak in tensile.•The Tensile strength of concrete is roughly 10% of its compressive strength•Nearly all reinforce concrete structures are design on the assumption that the concrete does not resist any tensile forces.•Tension will create cracking of the concrete.
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What is Tensile Strength?
• Importance in design of concrete roadsand runways.
• E.g, its flexural strength or modulus of rupture(tensile strength in bending) is
utilized for distributing the concentrated loads over a wider area of road pavement.
• Importance in design of concrete roadsand runways.
• E.g, its flexural strength or modulus of rupture(tensile strength in bending) is
utilized for distributing the concentrated loads over a wider area of road pavement.
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What is Tensile Strength?
Tensile strength. The amount of stretching force a material can withstand
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What is Flexural Strength?
• FS is one measure of the tensile strength of concrete.• Measured on unreinforced concrete beam or slab to
resist failure in bending.• Is expressed as Modulus of Rupture(MR) in psi (Mpa)• Flexural MR is about 10 to 20 percent of CS
depending on size, type and volume of coarse aggregate used.
• FS is one measure of the tensile strength of concrete.• Measured on unreinforced concrete beam or slab to
resist failure in bending.• Is expressed as Modulus of Rupture(MR) in psi (Mpa)• Flexural MR is about 10 to 20 percent of CS
depending on size, type and volume of coarse aggregate used.
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What is Shear Strength?
• Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear.
• A shear load is a force that tends to produce a sliding failure on a material along a plane that is parallel to the direction of the force.
• Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear.
• A shear load is a force that tends to produce a sliding failure on a material along a plane that is parallel to the direction of the force.
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What is Shear Strength?
• the shear strength of a component is important for designing the dimensions and materials to be used for the manufacture/construction of the component (e.g. beams, plates, or bolts).
• In a reinforced concrete beam, the main purpose of stirrups is to increase the shear strength.
• the shear strength of a component is important for designing the dimensions and materials to be used for the manufacture/construction of the component (e.g. beams, plates, or bolts).
• In a reinforced concrete beam, the main purpose of stirrups is to increase the shear strength.
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What is Shear Strength?
Steel in place in a abeamStirrup and column ties 27
What is Shear Strength?
• Shear strength is the maximum shear stress that a material can absorb in one impact before failure ness of the material tested.
• Shear strength is the maximum shear stress that a material can absorb in one impact before failure ness of the material tested.
Shear strength. The maximum shear stress a material can absorb in one impact
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Concrete Performance failure
• Spalling• Shrinkage• Creep
• Spalling• Shrinkage• Creep
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Spalling Concrete ( concrete cancer)
• Concrete cancer can affect any building in which reinforced concrete is used.
• This includes floor slabs, stairs, balconies, walls, columns, beams and pathways.
• Essentially, the steel responsible for reinforcement has begun to rust.
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Spalling Concrete ( concrete cancer)
• Spalling concrete is concrete which has broken up, flaked, or become pitted.
• This is usually the result of a combination of poor installation and environmental factors which stress the concrete, causing it to become damaged.
• On a low level, concrete spalling can be purely cosmetic in nature. However, it can also result in structural damage such as damage to reinforcing bars positioned inside the concrete.
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Spalling Concrete ( concrete cancer)
• Spalling concrete is largely due to a natural deterioration process called carbonation.
• Carbon dioxide in the air diffuses into the concrete and reacts with the alkalis in it.
• The concrete becomes carbonated and this allows the embedded steel bars to corrode.
• These corroded steel bars expand and exert a force on the surrounding concrete causing the concrete to bulge and crack.
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Spalling Concrete ( concrete cancer)
• The early stages of spalling concrete will not affect the safety of the building. However, the spalling concrete should be repaired as soon as possible before the steel bars corrode further and damage larger areas hence the term 'concrete cancer'.
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Spalling Concrete ( concrete cancer)
Spalling Concrete - Concrete Cancer - Corrosion in Reinforced Concrete
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Spalling Concrete ( concrete cancer)
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Concrete Shrinkage
• Shrinkage of concrete is defined as the contraction due to loss of moisture.
• Due to the shrinkage of concrete, the prestress in the tendon is reduced with time.
Prestressed concrete• concrete with stresses induced in it before use so as to
counteract stresses that will be produced by load; often contains stretched steel bars or wires called tendons
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Concrete Shrinkage
• Due to water loss to atmosphere (volume loss).o Plastic shrinkage occurs while concrete is still “wet” (hot day, flat work, etc.)o Drying shrinkage occurs after concrete has seto Most shrinkage occurs in first few months (~80% within one year).o Reinforcement restrains the development of
shrinkage
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Concrete Shrinkage
• As concrete harden there is reduction in volume• It caused a shrinkage
- Absorption of the water by the concrete and the aggregate- Evaporation of the water which rises to concrete surface.
• This contraction can lead to cracks or breaks in the surface of the concrete, or in tiles and other floor finishes installed over the slab.
• To minimize cracks associated with concrete shrinkage, builders place control joints at specific intervals along the concrete.
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Concrete Shrinkage
• A wet mix makes pouring easier but it also tends to encourage shrinkage.
• The more shrinkage the higher chances of finding cracks later.
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Parallel cracking perpendicularto the direction of shrinkage
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Restrained shrinkage cracking
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Concrete Creep
• Creep of concrete is defined as the increase in deformation with time under constant load.
• Due to the creep of concrete, the prestress in the tendon is reduced with time.
• Basically, long term pressure or stress on concrete can make it change shape.
• This deformation usually occurs in the direction the force is being applied.
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Concrete Creep
• Like a concrete column getting more compressed, or a beam bending.
• Creep does not necessarily cause concrete to fail or break apart.
Creep is factored in when concrete structures are designed.
• creep deformation does not occur suddenly upon the application of stress. Instead, strain accumulates as a result of long-term stress. Creep is a "time-dependent" deformation.
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