This document provides an overview of prestressing concepts, materials, and systems. It discusses the basic concepts of prestressing including transforming concrete into an elastic material, combining high-strength steel with concrete, and achieving load balancing. The document describes the advantages and limitations of prestressing. It also summarizes the different types of prestressing in terms of the source of prestressing force, whether it is external or internal, pre-tensioned or post-tensioned, linear or circular, full or partial, and uniaxial, biaxial, or multiaxial. Finally, it discusses prestressing materials including concrete, aggregate, cement, water, admixtures, grout, and prestressing steel.
Prestressing Concept, Materilas and Prestressing SystemLatif Hyder Wadho
The document discusses prestressing concepts and materials used in prestressed concrete. It describes how prestressing applies an initial compressive stress to concrete prior to service loads to improve strength and durability. Common prestressing materials include high-strength steel strands/wires, which are assembled into tendons and anchored internally or externally before or after concrete casting for pre-tensioning or post-tensioning. Grout is also discussed for transmitting stress between steel and concrete.
Prestressed concrete has several advantages over reinforced concrete including being more crack-resistant, durable, and requiring smaller cross-sectional areas, allowing for longer spans and easier transport. However, it also has some disadvantages such as requiring specialized equipment, advanced technical knowledge, and skilled labor for construction, as well as more expensive prestressing reinforcement bars.
This document discusses column jacketing, which is a method of retrofitting and strengthening existing columns. It involves adding reinforced concrete, steel, or fiber-reinforced polymer around the column. The key steps are preparing the column surface, adding shear keys and reinforcement, applying a bonding agent, and casting the new concrete or installing the jacket. Column jacketing increases the strength and seismic capacity of the column. It improves confinement and increases axial, shear, and foundation load capacity without significant weight addition.
This document defines and describes various types and concepts related to prestressed concrete. It discusses:
1) Definitions of prestressing steel types like wires, strands, tendons, and cables. It also defines bonded and unbonded tendons.
2) Advantages of prestressing like increased strength, reduced cracking, and suitability for precast construction.
3) Limitations include needing skilled technology and higher material costs.
4) Types of prestressing based on force source, location, sequence, member shape, and direction. It provides examples of pre-tensioning and post-tensioning, internal and external prestressing, and linear and circular prestressing.
Prestressed concrete is concrete that is placed under compression prior to service loads being applied through tensioning of steel tendons. This counteracts tensile stresses from loads to improve the performance of the concrete. Eugene Freyssinet is considered the father of prestressed concrete, developing techniques like high strength steel wires and conical wedges for post-tensioning in the 1930s-1940s. Prestressing can be through pre-tensioning or post-tensioning, depending on if the steel is tensioned before or after the concrete is cast. Popular post-tensioning systems include Freyssinet, Magnel Blaton, Gifford-Udall, and Lee-McCall methods. Prestressed concrete provides
DESTRUCTIVE AND NON-DESTRUCTIVE TEST OF CONCRETEKaran Patel
The standard method of evaluating the quality of concrete in buildings or structures is to test specimens cast simultaneously for compressive, flexural and tensile strengths.
The main disadvantages are that results are not obtained immediately; that concrete in specimens may differ from that in the actual structure as a result of different curing and compaction conditions; and that strength properties of a concrete specimen depend on its size and shape.
Although there can be no direct measurement of the strength properties of structural concrete for the simple reason that strength determination involves destructive stresses, several non- destructive methods of assessment have been developed.
This document discusses different methods of constructing underground structures beneath existing surfaces without disrupting traffic, including box jacking, arched jacking, and thrust boring. Box jacking involves pushing pre-cast concrete boxes into the ground with hydraulic jacks to form the structure. Arched jacking and thrust boring use similar techniques to jack pipes through the ground. Freezing the soil is another method used to stabilize the ground and prevent issues like water seepage when constructing underground. Case studies demonstrate how these techniques have been applied to real projects.
The document discusses composite construction using precast prestressed concrete beams and cast-in-situ concrete. It describes how the two elements act compositely after the in-situ concrete hardens. Composite beams can be constructed as either propped or unpropped. Propped construction involves supporting the precast beam during casting to relieve it of the wet concrete weight, while unpropped construction allows stresses to develop under self-weight. Design and analysis of composite beams involves calculating stresses and deflections considering composite action. Differential shrinkage between precast and in-situ concrete also induces stresses.
Prestressing Concept, Materilas and Prestressing SystemLatif Hyder Wadho
The document discusses prestressing concepts and materials used in prestressed concrete. It describes how prestressing applies an initial compressive stress to concrete prior to service loads to improve strength and durability. Common prestressing materials include high-strength steel strands/wires, which are assembled into tendons and anchored internally or externally before or after concrete casting for pre-tensioning or post-tensioning. Grout is also discussed for transmitting stress between steel and concrete.
Prestressed concrete has several advantages over reinforced concrete including being more crack-resistant, durable, and requiring smaller cross-sectional areas, allowing for longer spans and easier transport. However, it also has some disadvantages such as requiring specialized equipment, advanced technical knowledge, and skilled labor for construction, as well as more expensive prestressing reinforcement bars.
This document discusses column jacketing, which is a method of retrofitting and strengthening existing columns. It involves adding reinforced concrete, steel, or fiber-reinforced polymer around the column. The key steps are preparing the column surface, adding shear keys and reinforcement, applying a bonding agent, and casting the new concrete or installing the jacket. Column jacketing increases the strength and seismic capacity of the column. It improves confinement and increases axial, shear, and foundation load capacity without significant weight addition.
This document defines and describes various types and concepts related to prestressed concrete. It discusses:
1) Definitions of prestressing steel types like wires, strands, tendons, and cables. It also defines bonded and unbonded tendons.
2) Advantages of prestressing like increased strength, reduced cracking, and suitability for precast construction.
3) Limitations include needing skilled technology and higher material costs.
4) Types of prestressing based on force source, location, sequence, member shape, and direction. It provides examples of pre-tensioning and post-tensioning, internal and external prestressing, and linear and circular prestressing.
Prestressed concrete is concrete that is placed under compression prior to service loads being applied through tensioning of steel tendons. This counteracts tensile stresses from loads to improve the performance of the concrete. Eugene Freyssinet is considered the father of prestressed concrete, developing techniques like high strength steel wires and conical wedges for post-tensioning in the 1930s-1940s. Prestressing can be through pre-tensioning or post-tensioning, depending on if the steel is tensioned before or after the concrete is cast. Popular post-tensioning systems include Freyssinet, Magnel Blaton, Gifford-Udall, and Lee-McCall methods. Prestressed concrete provides
DESTRUCTIVE AND NON-DESTRUCTIVE TEST OF CONCRETEKaran Patel
The standard method of evaluating the quality of concrete in buildings or structures is to test specimens cast simultaneously for compressive, flexural and tensile strengths.
The main disadvantages are that results are not obtained immediately; that concrete in specimens may differ from that in the actual structure as a result of different curing and compaction conditions; and that strength properties of a concrete specimen depend on its size and shape.
Although there can be no direct measurement of the strength properties of structural concrete for the simple reason that strength determination involves destructive stresses, several non- destructive methods of assessment have been developed.
This document discusses different methods of constructing underground structures beneath existing surfaces without disrupting traffic, including box jacking, arched jacking, and thrust boring. Box jacking involves pushing pre-cast concrete boxes into the ground with hydraulic jacks to form the structure. Arched jacking and thrust boring use similar techniques to jack pipes through the ground. Freezing the soil is another method used to stabilize the ground and prevent issues like water seepage when constructing underground. Case studies demonstrate how these techniques have been applied to real projects.
The document discusses composite construction using precast prestressed concrete beams and cast-in-situ concrete. It describes how the two elements act compositely after the in-situ concrete hardens. Composite beams can be constructed as either propped or unpropped. Propped construction involves supporting the precast beam during casting to relieve it of the wet concrete weight, while unpropped construction allows stresses to develop under self-weight. Design and analysis of composite beams involves calculating stresses and deflections considering composite action. Differential shrinkage between precast and in-situ concrete also induces stresses.
This document discusses prestressed concrete bridges. It begins with definitions of prestressed concrete as concrete with internal stresses introduced to counteract external loads. It then provides a brief history of prestressed concrete, noting key innovators. Examples of prestressed concrete bridges in India are given, including the famous Pamban Road Bridge. The document goes on to explain the basic principles, terminology, types, and methods of prestressing, as well as the advantages and disadvantages of prestressed concrete.
This document discusses losses in prestressed concrete, including short-term and long-term losses. It describes the differences between pre-tensioned and post-tensioned concrete. Losses include elastic shortening, friction, anchorage slip, creep, shrinkage, and relaxation. Total losses can be 15-20% of the initial prestress. Post-tensioned concrete experiences more types of losses but lower overall losses compared to pre-tensioned concrete. Proper design and materials are needed to minimize losses in prestressed concrete.
Pre-stressed concrete uses tensioned steel strands or bars to place concrete in compression and improve its tensile strength. There are two main methods - pre-tensioning and post-tensioning. Pre-tensioning tensions the strands before the concrete is poured, while post-tensioning tensions strands inside ducts after the concrete has cured. This compression counteracts tensile and flexural stresses from loads to reduce cracking and increase strength, allowing pre-stressed concrete to be lighter and more durable than reinforced concrete. It is commonly used in bridges, buildings, tanks, and other structures.
Prestressed concrete combines high-strength concrete and high-strength steel in an active manner by tensioning steel tendons and holding them against the concrete, putting it into compression. This transforms concrete from a brittle to a more elastic material. It allows for optimal use of each material's properties and better behavior under loads. Prestressed concrete was pioneered in the 1930s and its use has expanded, finding applications in bridges and other structures. Common methods are pretensioning and post-tensioning, using various tendon types, with bonded or unbonded configurations. Tensioning is done using mechanical, hydraulic, electrical or chemical devices.
Pre-stressed concrete uses tensioned steel strands or bars to place concrete in compression before application of service loads. This counters the tensile stresses induced by loads and prevents cracking. There are two main methods: pre-tensioning applies tension before pouring concrete, while post-tensioning tensions strands after concrete curing. Pre-stressed concrete allows for smaller and lighter structures that resist loads, deflection, and cracking better than reinforced concrete.
It is the presentation based on pre- stressed concrete construction which includes each and every point and scope which may be useful to civil engineering students
A system of prestressing involves tensioning tendons and securing them firmly to concrete. There are two main types: pre-tensioning and post-tensioning. Pre-tensioning involves pulling tendons tight between anchored abutments before concrete is poured. The Hoyer or long-line pre-tensioning system uses bulkheads to stretch wires over which molds are placed for concrete pouring. The Freyssinet system was the first post-tensioning method, using a cable of high-strength wires grouted into a duct within the concrete beam. Wires are anchored using conical plugs pushed into holes in concrete cylinders after jacking. The Magnel Blaton system tensions wires in pairs using sandwich plates
High density concrete, high strength concrete and high performance concrete.shebina a
The document discusses high density concrete, its components, types of aggregates used, admixtures, applications, advantages and disadvantages. High density concrete has a density over 2600 kg/m3 and offers greater strength than regular concrete. Its main components are cement, water, aggregates and admixtures. Natural aggregates come from iron ores while man-made aggregates include iron shots, chilcon and synthetic aggregates. Admixtures like water reducers are used to increase workability and reduce cement and water requirements. High density concrete has applications in radiation shielding, precast blocks, bridges and more due to its high strength and durability.
The document discusses different methods of post-tensioning concrete structures. It describes the Freyssinet system as the first introduced method using steel wires grouped into cables with a helical spring. The Magnel Blaton system stresses wires two at a time using sandwich plates and wedges. The Gifford Udall system uses single wires stressed independently with double-acting jacks and tube or plate anchorages. The Lee McCall system prestresses steel bars using threaded bars tightened with nuts against bearing plates.
Behavior of rc structure under earthquake loadingBinay Shrestha
The document discusses reasons why reinforced concrete (RC) structures fail during earthquakes and measures to improve their performance. Key points include:
1) RC buildings often fail due to design deficiencies like ignoring concepts of strong columns-weak beams or having soft stories, or construction defects like weak joints or improper reinforcement detailing.
2) Measures to improve performance include following design concepts of strong columns-weak beams and designing soft story elements to withstand higher forces, as well as improving construction quality of joints and reinforcement details.
3) Other factors that can lead to failure are short column effects, torsional forces from asymmetric shapes, and disturbance of the load path through the structure.
Prestressing is the intentional application of compressive force to a structure before external loads are applied in order to improve its strength and behavior. It works by counteracting the internal tensile stresses that would otherwise develop under external loads. Historically, prestressing techniques were used in structures like wooden barrels, bicycle wheels, and guyed ropes, where internal compression resisted tension from loads. Prestressed concrete applies this concept by compressing steel within a concrete structure to counteract the tensile stresses from loads, improving the structure's load capacity compared to reinforced concrete alone.
Prestressed concrete is concrete that is placed under compression using tensioned steel strands, cables, or bars. This is done through either pre-tensioning or post-tensioning. In pre-tensioning, the steel components are tensioned before the concrete is poured, while in post-tensioning, the steel components are tensioned after the concrete has hardened. Prestressed concrete provides benefits over reinforced concrete like lower construction costs, thinner structural elements, and longer spans between supports.
Shoring is the construction of a temporary structure to support an unsafe or unstable structure. There are three main types of shoring: raking shores, flying shores, and dead shores. Raking shores use inclined members called rakers to provide lateral support to walls. Flying shores provide temporary support between party walls when an intermediate building is demolished. Dead shores provide vertical support to walls and structures when the lower part of a wall is removed, such as to add an opening.
This document discusses different methods of prestressing concrete, including pretensioning and post-tensioning. Pretensioning involves stressing steel tendons before placing concrete around them, while post-tensioning involves stressing tendons after the concrete has cured using hydraulic jacks. Post-tensioning allows for longer spans, thinner slabs, and more architectural freedom compared to conventional reinforced concrete or pretensioned concrete. Common applications of post-tensioning include parking structures, bridges, and building floors and roofs.
Pile foundation -Types, Advantages & Load Carrying CapacitySHAZEBALIKHAN1
A pile foundation is a deep foundation that is relatively stronger and has a lesser settlement.
Types of piles- driven pile, bored pile, end-bearing pile, friction pile, tension pile, sheet pile, displacement pile, non-displacement pile etc.
Static & Dynamic methods for pile foundation load-carrying capacity. Pile load test method and sample report format.
A continuous beam has more than one span carried by multiple supports. It is commonly used in bridge construction since simple beams cannot support large spans without requiring greater strength and stiffness. Continuous prestressed concrete beams provide adequate strength and stiffness while allowing for redistribution of moments, resulting in higher load capacity, reduced deflections, and more evenly distributed bending moments compared to equivalent simple beams. Analysis of continuous beams requires determining primary moments from prestressing, secondary moments induced by support reactions, and the combined resultant moments.
The document provides instructions for conducting pull-out tests to determine the compressive strength of concrete. It states that pull-out tests should be confirmed to BS 1881 Part 207 and give a direct tensile strength value. It describes how inserts can be cast into wet concrete or positioned in hardened concrete using an under-reamed groove. When testing, at least four pull-out tests should be performed at each location and a loading rate of 0.5 ± 0.2 kN/s should be used for 25mm diameter inserts. The compressive strength can then be calculated from the direct tensile strength value obtained during testing.
Coffer dams are temporary structures built to retain water and soil in order to create a dry work area for construction projects. There are several types of coffer dams suited to different conditions, including earth-filled, sheet pile, and cellular designs. Key considerations in selecting a coffer dam include water depth, area size, soil/river bed conditions, and potential for erosion or flooding. Proper design is needed to withstand hydrostatic pressures and ensure structural integrity until the permanent structure is complete.
This document provides an introduction to prestressed concrete, including:
1) A prestressed concrete structure differs from reinforced concrete in applying an initial load to counteract stresses from use.
2) Prestressing concepts include transforming concrete to an elastic material, combining high strength steel with concrete, and load balancing.
3) Methods include pre-tensioning and post-tensioning, and materials include high strength steel tendons or bars, concrete, and grout.
Prestressed concrete is concrete in which internal stresses are introduced to counteract external loads. Tendons are stretched elements that impart prestress, and anchorage devices enable the tendons to impart and maintain prestress. There are two main methods - pretensioning, where tendons are tensioned before concrete is cast, and post-tensioning, where tendons are tensioned against hardened concrete. Prestressed concrete uses high-strength materials like cement, concrete, and steel tendons or strands to achieve its compressive strength and durability advantages over reinforced concrete.
This document discusses prestressed concrete bridges. It begins with definitions of prestressed concrete as concrete with internal stresses introduced to counteract external loads. It then provides a brief history of prestressed concrete, noting key innovators. Examples of prestressed concrete bridges in India are given, including the famous Pamban Road Bridge. The document goes on to explain the basic principles, terminology, types, and methods of prestressing, as well as the advantages and disadvantages of prestressed concrete.
This document discusses losses in prestressed concrete, including short-term and long-term losses. It describes the differences between pre-tensioned and post-tensioned concrete. Losses include elastic shortening, friction, anchorage slip, creep, shrinkage, and relaxation. Total losses can be 15-20% of the initial prestress. Post-tensioned concrete experiences more types of losses but lower overall losses compared to pre-tensioned concrete. Proper design and materials are needed to minimize losses in prestressed concrete.
Pre-stressed concrete uses tensioned steel strands or bars to place concrete in compression and improve its tensile strength. There are two main methods - pre-tensioning and post-tensioning. Pre-tensioning tensions the strands before the concrete is poured, while post-tensioning tensions strands inside ducts after the concrete has cured. This compression counteracts tensile and flexural stresses from loads to reduce cracking and increase strength, allowing pre-stressed concrete to be lighter and more durable than reinforced concrete. It is commonly used in bridges, buildings, tanks, and other structures.
Prestressed concrete combines high-strength concrete and high-strength steel in an active manner by tensioning steel tendons and holding them against the concrete, putting it into compression. This transforms concrete from a brittle to a more elastic material. It allows for optimal use of each material's properties and better behavior under loads. Prestressed concrete was pioneered in the 1930s and its use has expanded, finding applications in bridges and other structures. Common methods are pretensioning and post-tensioning, using various tendon types, with bonded or unbonded configurations. Tensioning is done using mechanical, hydraulic, electrical or chemical devices.
Pre-stressed concrete uses tensioned steel strands or bars to place concrete in compression before application of service loads. This counters the tensile stresses induced by loads and prevents cracking. There are two main methods: pre-tensioning applies tension before pouring concrete, while post-tensioning tensions strands after concrete curing. Pre-stressed concrete allows for smaller and lighter structures that resist loads, deflection, and cracking better than reinforced concrete.
It is the presentation based on pre- stressed concrete construction which includes each and every point and scope which may be useful to civil engineering students
A system of prestressing involves tensioning tendons and securing them firmly to concrete. There are two main types: pre-tensioning and post-tensioning. Pre-tensioning involves pulling tendons tight between anchored abutments before concrete is poured. The Hoyer or long-line pre-tensioning system uses bulkheads to stretch wires over which molds are placed for concrete pouring. The Freyssinet system was the first post-tensioning method, using a cable of high-strength wires grouted into a duct within the concrete beam. Wires are anchored using conical plugs pushed into holes in concrete cylinders after jacking. The Magnel Blaton system tensions wires in pairs using sandwich plates
High density concrete, high strength concrete and high performance concrete.shebina a
The document discusses high density concrete, its components, types of aggregates used, admixtures, applications, advantages and disadvantages. High density concrete has a density over 2600 kg/m3 and offers greater strength than regular concrete. Its main components are cement, water, aggregates and admixtures. Natural aggregates come from iron ores while man-made aggregates include iron shots, chilcon and synthetic aggregates. Admixtures like water reducers are used to increase workability and reduce cement and water requirements. High density concrete has applications in radiation shielding, precast blocks, bridges and more due to its high strength and durability.
The document discusses different methods of post-tensioning concrete structures. It describes the Freyssinet system as the first introduced method using steel wires grouped into cables with a helical spring. The Magnel Blaton system stresses wires two at a time using sandwich plates and wedges. The Gifford Udall system uses single wires stressed independently with double-acting jacks and tube or plate anchorages. The Lee McCall system prestresses steel bars using threaded bars tightened with nuts against bearing plates.
Behavior of rc structure under earthquake loadingBinay Shrestha
The document discusses reasons why reinforced concrete (RC) structures fail during earthquakes and measures to improve their performance. Key points include:
1) RC buildings often fail due to design deficiencies like ignoring concepts of strong columns-weak beams or having soft stories, or construction defects like weak joints or improper reinforcement detailing.
2) Measures to improve performance include following design concepts of strong columns-weak beams and designing soft story elements to withstand higher forces, as well as improving construction quality of joints and reinforcement details.
3) Other factors that can lead to failure are short column effects, torsional forces from asymmetric shapes, and disturbance of the load path through the structure.
Prestressing is the intentional application of compressive force to a structure before external loads are applied in order to improve its strength and behavior. It works by counteracting the internal tensile stresses that would otherwise develop under external loads. Historically, prestressing techniques were used in structures like wooden barrels, bicycle wheels, and guyed ropes, where internal compression resisted tension from loads. Prestressed concrete applies this concept by compressing steel within a concrete structure to counteract the tensile stresses from loads, improving the structure's load capacity compared to reinforced concrete alone.
Prestressed concrete is concrete that is placed under compression using tensioned steel strands, cables, or bars. This is done through either pre-tensioning or post-tensioning. In pre-tensioning, the steel components are tensioned before the concrete is poured, while in post-tensioning, the steel components are tensioned after the concrete has hardened. Prestressed concrete provides benefits over reinforced concrete like lower construction costs, thinner structural elements, and longer spans between supports.
Shoring is the construction of a temporary structure to support an unsafe or unstable structure. There are three main types of shoring: raking shores, flying shores, and dead shores. Raking shores use inclined members called rakers to provide lateral support to walls. Flying shores provide temporary support between party walls when an intermediate building is demolished. Dead shores provide vertical support to walls and structures when the lower part of a wall is removed, such as to add an opening.
This document discusses different methods of prestressing concrete, including pretensioning and post-tensioning. Pretensioning involves stressing steel tendons before placing concrete around them, while post-tensioning involves stressing tendons after the concrete has cured using hydraulic jacks. Post-tensioning allows for longer spans, thinner slabs, and more architectural freedom compared to conventional reinforced concrete or pretensioned concrete. Common applications of post-tensioning include parking structures, bridges, and building floors and roofs.
Pile foundation -Types, Advantages & Load Carrying CapacitySHAZEBALIKHAN1
A pile foundation is a deep foundation that is relatively stronger and has a lesser settlement.
Types of piles- driven pile, bored pile, end-bearing pile, friction pile, tension pile, sheet pile, displacement pile, non-displacement pile etc.
Static & Dynamic methods for pile foundation load-carrying capacity. Pile load test method and sample report format.
A continuous beam has more than one span carried by multiple supports. It is commonly used in bridge construction since simple beams cannot support large spans without requiring greater strength and stiffness. Continuous prestressed concrete beams provide adequate strength and stiffness while allowing for redistribution of moments, resulting in higher load capacity, reduced deflections, and more evenly distributed bending moments compared to equivalent simple beams. Analysis of continuous beams requires determining primary moments from prestressing, secondary moments induced by support reactions, and the combined resultant moments.
The document provides instructions for conducting pull-out tests to determine the compressive strength of concrete. It states that pull-out tests should be confirmed to BS 1881 Part 207 and give a direct tensile strength value. It describes how inserts can be cast into wet concrete or positioned in hardened concrete using an under-reamed groove. When testing, at least four pull-out tests should be performed at each location and a loading rate of 0.5 ± 0.2 kN/s should be used for 25mm diameter inserts. The compressive strength can then be calculated from the direct tensile strength value obtained during testing.
Coffer dams are temporary structures built to retain water and soil in order to create a dry work area for construction projects. There are several types of coffer dams suited to different conditions, including earth-filled, sheet pile, and cellular designs. Key considerations in selecting a coffer dam include water depth, area size, soil/river bed conditions, and potential for erosion or flooding. Proper design is needed to withstand hydrostatic pressures and ensure structural integrity until the permanent structure is complete.
This document provides an introduction to prestressed concrete, including:
1) A prestressed concrete structure differs from reinforced concrete in applying an initial load to counteract stresses from use.
2) Prestressing concepts include transforming concrete to an elastic material, combining high strength steel with concrete, and load balancing.
3) Methods include pre-tensioning and post-tensioning, and materials include high strength steel tendons or bars, concrete, and grout.
Prestressed concrete is concrete in which internal stresses are introduced to counteract external loads. Tendons are stretched elements that impart prestress, and anchorage devices enable the tendons to impart and maintain prestress. There are two main methods - pretensioning, where tendons are tensioned before concrete is cast, and post-tensioning, where tendons are tensioned against hardened concrete. Prestressed concrete uses high-strength materials like cement, concrete, and steel tendons or strands to achieve its compressive strength and durability advantages over reinforced concrete.
The document provides an overview of prestressed concrete structures including:
- Definitions of prestressing where internal stresses counteract external loads.
- The key terminology used including tendons, anchorage, pretensioning vs post-tensioning.
- The materials used including cement, concrete, and steel types.
- The stages of loading and advantages of prestressing over reinforced concrete.
- Details of pretensioning and post-tensioning systems including equipment, processes, and differences between the two methods.
The document discusses pre-tensioning systems and devices used in prestressed concrete. It describes the stages of pre-tensioning as anchoring tendons, applying tension, casting concrete, and cutting tendons to transfer stress. Key devices are prestressing beds, end abutments, jacks, and anchoring systems. An example of manufacturing pre-tensioned railway sleepers is provided with photos showing the process from tensioning strands to curing and storage of the finished sleepers.
This document discusses prestressed concrete, including:
- The basic concepts of prestressing including using metal bands, pre-tensioned spokes, and introducing stresses to counteract external loads.
- Design concepts like losses in prestressing structures from elastic shortening, creep, shrinkage, relaxation, friction, and anchorage slip.
- Provisions for prestressing in the Indian Road Congress Bridge Code and Indian Standard Code.
- Construction aspects like casting of girders, post-tensioning work, and load testing of structures.
Prestressed concrete is a structural material that allows for predetermined, engineering stresses to be placed in members to counteract the stresses that occur when they are subject to loading.
Pre stressed & pre-cast concrete technology - ce462Saqib Imran
1) Precast concrete consists of concrete elements that are cast and cured off-site and then transported for assembly. Prestressed concrete uses high-strength steel strands or bars that are tensioned to put the concrete in compression and improve its strength.
2) Common precasting techniques include pre-tensioning, where steel is tensioned before the concrete is poured, and post-tensioning, where steel is tensioned after the concrete cures.
3) Advantages of prestressed concrete include reduced cracking, lighter weight, and improved durability; disadvantages include higher material costs and need for specialized equipment.
This document provides information on prestressed concrete and the Freyssinet prestressing system. It discusses the principles of prestressing, including pre-tensioning and post-tensioning methods. It also describes the key components of the Freyssinet post-tensioning system, including prestressing steels, anchorages, ducts, supports, and couplers. The anchorages can be mono-strand or multi-strand and are designed to transfer prestressing forces to the concrete structure.
Pre stressed concrete- modular construction technologyAnjith Augustine
This document provides an overview of pre-stressed concrete, including its history, types (pre-tensioning and post-tensioning), materials, applications, advantages, and tensioning devices. Some key points include: pre-stressed concrete was developed in the 1930s-1940s and the first pre-stressed concrete bridge was built in India in 1948; it uses high-strength steel tendons to put concrete under compression and improve its tensile strength; common applications include bridges, buildings, and other structures; and advantages are increased strength, reduced cracking, and lighter/thinner designs.
This document discusses prestressed concrete, which involves applying an initial compressive load to concrete before it experiences tensile stresses from use. Prestressing concrete improves its strength in tension. There are two main types: pre-tensioned concrete uses steel tendons that are tensioned before the concrete is cast around them, while post-tensioned concrete uses tendons tensioned after the concrete is cast. Prestressing concrete allows for longer spans and greater loads than ordinary reinforced concrete.
This document provides an introduction to prestressed concrete, including:
- Prestressing concrete involves applying an initial compressive load to counteract tensile stresses during use. Ancient examples include metal bands on wood.
- Prestressing provides advantages over reinforced concrete like reduced cracking, increased strength and stiffness, and suitability for precast construction.
- It describes prestressing materials, common systems like pre-tensioning and post-tensioning, and concepts in the analysis and design of prestressed concrete like stress conditions and load balancing.
This document provides a brief history of prestressed concrete, beginning in 1824 with the development of Portland cement. It then outlines several important developments in prestressed concrete technology from the late 19th century through the mid-20th century by innovators from various countries. These include early uses of steel in concrete, prestressing methods like pre-tensioning and post-tensioning, and development of high-strength steel and anchoring systems. It also mentions increased use of prestressed concrete during World War 2 and establishment of professional organizations to support the field.
This document discusses prestressed concrete. It begins with a definition of prestressing as applying an initial load to a structure to counteract stresses during its service period. It then provides a brief history of prestressing including early attempts using metal bands on barrels and tensioning bicycle wheel spokes. The document outlines different materials and hardware used in prestressing including tendons, strands, wires, bars and anchoring devices. It describes various prestressing techniques such as pretensioning, posttensioning, bonded vs unbonded tendons. Applications of prestressed concrete include bridges, buildings, tanks, and more. Advantages are listed as increased strength, reduced cracking and deformation, while limitations include higher costs and need for skilled construction techniques.
Prestressed concrete uses tensioned steel tendons to put concrete structures into compression and improve their strength. There are two main types - pre-tensioned concrete where the tendons are tensioned before the concrete is poured, and post-tensioned concrete where the tendons are tensioned after the concrete has cured. Prestressed concrete allows for longer spans, uses materials more efficiently, and results in stronger, crack-resistant structures.
This document summarizes a presentation on prestressed concrete. It begins with an introduction to prestressed concrete and how it overcomes weaknesses in concrete in tension. It then describes the principles of prestressing by inducing compressive stresses with high-strength tendons before loads are applied. The document compares reinforced concrete with prestressed concrete and describes the methods of pre-tensioning and post-tensioning. It provides examples of prestressed concrete structures like beams, bridges and discusses advantages like reduced size and increased spans as well as disadvantages like higher material costs.
ANALYSIS & DESIGN ASPECTS OF PRE-STRESSED MEMBERS USING F.R.P. TENDONSGirish Singh
The purpose of this investigation is mainly a brief explanation about the advantages of FRP over steel. The various uses and advantages of FRP are explained in this project. In this project, we have taken a section of 3m length, 200mm width and 300mm depth and using a parabolic tendon of eccentricity 100mm at the centre. We have design the section for FRP as well as steel with the above data. The final stresses obtained is being verified with the help of Ansys software. We have shown the result of steel straight tendon only in this mini project.
Prestressing is a technique where tension is applied to concrete before hardening to improve its performance. There are two main types - pre-tensioning and post-tensioning. Pre-tensioning involves tensioning steel tendons before casting concrete, while post-tensioning tensions tendons after casting. There are losses in prestress over time from factors like elastic shortening, shrinkage, creep, and steel relaxation. Proper materials and design are needed to account for these losses and ensure structures perform as intended.
pre stress Concrete and losses of pre stress concrete . Manufacturng of pre t...Anoop Chhapola
This document discusses pre-stressed concrete and provides details on:
1. The different types of pre-stressing including pre-tensioning and post-tensioning. Pre-tensioning involves tensioning before concrete casting while post-tensioning tensions after casting.
2. The forms of prestressing steel used including wires, strands, tendons, and cables.
3. The common systems for pre-tensioning and post-tensioning including Freyssinet, Magnel, Gifford-Udall, and Lee-McCall systems.
4. The sources of losses in prestress over time including elastic shortening, friction, anchorage slip, creep of concrete, shrink
Post-tensioning is a technique for reinforcing concrete structures. The prestressing steel cables inside the sleeves or plastic ducts are positioned in the forms before placing the concrete. As the concrete gains strength, the cables are stressed to design forces before the application of the service load and are anchored att the outer edge region of the concrete.
This document provides an overview of pre-stressed and precast concrete. It discusses basic concepts like pre-stressing, uses of pre-stressed concrete, materials used including high-strength concrete and steel, and methods of prestressing like pre-tensioning and post-tensioning. It also covers topics like tendon profiles, advantages and disadvantages of pre-stressed concrete, losses in prestressing, types of prestressing steel, properties of prestressing steel, and use of non-prestressed reinforcement. The document is submitted by 5 students and contains 15 chapters with information on concepts, introduction, early introduction, uses, the basic idea, methods, profiles, advantages, disadvantages, losses, materials, types of
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3. A prestressed concrete structure is different from a
conventional reinforced concrete structure due to the
application of an initial load on the structure prior to its
use. The initial load or ‘prestress’ is applied to enable
the structure to counteract the stresses arising during its
service period.
The prestressing of a structure is not the only instance
of prestressing. The concept of prestressing existed
before the applications in concrete.
4. Force-fitting of metal bands on wooden barrels
The metal bands induce a state of initial hoop compression, to
counteract the hoop tension caused by filling of liquid in the
barrels.
Force-fitting of metal bands on wooden barrels
5. Pre-tensioning the spokes in a bicycle wheel
The pre-tension of a spoke in a bicycle wheel is applied to
such an extent that there will always be a residual tension in
the spoke.
Spokes in a bicycle wheel
6. Basic Concepts of Prestressing
There are three basic concepts of prestressing:
First Concept: Prestressing to transform
concrete into an Elastic Material.
Second Concept: Prestressing for Combination
of High Strength Steel with Concrete.
Third Concept: Prestressing to Achieve load
Balancing.
11. 1) Section remains uncracked under service
loads
Reduction of steel corrosion
Full section is utilised
Higher moment of inertia (higher stiffness)
Less deformations (improved serviceability).
Increase in shear capacity.
Suitable for use in pressure vessels, liquid retaining
structures.
Improved performance (resilience) under dynamic and
fatigue loading.
12. 2) High span-to-depth ratios
Larger spans possible with prestressing
buildings with large column-free spaces)
(bridges,
3) Suitable for precast construction
Rapid construction
Better quality control
Reduced maintenance
Suitable for repetitive construction
Availability of standard shapes.
13. Limitations of Prestressing
Prestressing needs skilled technology. Hence,
it is not as common as reinforced concrete.
The use of high strength materials is costly.
There is additional cost in auxiliary
equipment.
There is need for quality control and
inspection.
14. Types of Prestressing
Source of Prestressing Force
1)Hydraulic Prestressing
This is the simplest type of prestressing,
producing large prestressing forces.
The
hydraulic jack used for the tensioning of
tendons, comprises of calibrated pressure
gauges which directly indicate the magnitude of
force developed during the tensioning.
15. 2)Mechanical Prestressing
In this type of prestressing, the devices includes
weights with or without lever transmission, geared
transmission in conjunction with pulley blocks,
screw jacks with or without gear drives and wirewinding machines. This type of prestressing is
adopted for mass scale production.
3)Electrical Prestressing
In this type of prestressing, the steel wires are
electrically heated
and anchored before placing concrete in the molds.
This type of prestressing is also known as thermoelectric prestressing.
16. External or Internal Prestressing
External Prestressing
When the prestressing is achieved by elements
located outside the concrete, it is called external
prestressing. The tendons can lie outside the
member (for example in I-girders or walls) or
inside the hollow space of a box girder. This
technique is adopted in bridges and
strengthening of buildings. In the following
figure, the box girder of a bridge is prestressed
with tendons that lie outside the concrete.
18. Internal Prestressing
When the prestressing is achieved by elements
located inside the concrete member (commonly,
by embedded tendons), it is called internal
prestressing. Most of the applications of
prestressing are internal prestressing. In the
following figure, concrete will be cast around the
ducts for placing the tendons.
20. Pre-tensioning or Post-tensioning
Pre-tensioning
The tension is applied to the tendons before
casting of the concrete. The pre-compression is
transmitted from steel to concrete through bond
over the transmission length near the ends. The
following figure shows manufactured pretensioned electric poles.
22. Post-tensioning
The tension is applied to the tendons (located
in a duct) after hardening of the concrete. The
pre-compression is transmitted from steel to
concrete by the anchorage device (at the end
blocks). The following figure shows a posttensioned box girder of a bridge.
24. Linear or Circular Prestressing
Linear Prestressing
When the prestressed members are straight or
flat, in the direction of prestressing, the
prestressing is called linear prestressing. For
example, prestressing of beams, piles, poles and
slabs. The profile of the prestressing tendon may
be curved. The following figure shows linearly
prestressed railway sleepers.
26. Circular Prestressing
When the prestressed members are curved, in the
direction of prestressing, the prestressing is
called circular prestressing.
For example,
circumferential prestressing of tanks, silos, pipes
and similar structures.
28. Full, Limited or Partial Prestressing
Full Prestressing
When the level of prestressing is such that no tensile
stress is allowed in concrete under service loads, it is
called Full Prestressing.
Limited Prestressing
When the level of prestressing is such that the tensile
stress under service loads is within the cracking stress of
concrete, it is called Limited Prestressing.
Partial Prestressing
When the level of prestressing is such that under tensile
stresses due to service loads, the crack width is within the
allowable limit, it is called Partial Prestressing.
29. Uniaxial,
Biaxial
Prestressing
or
Multiaxial
Uniaxial Prestressing
When the prestressing tendons are parallel to one axis, it is
called Uniaxial Prestressing. For example, longitudinal
prestressing of beams.
Biaxial Prestressing
When there are prestressing tendons parallel to two axes, it
is called Biaxial Prestressing. The following figure shows
the biaxial prestressing of slabs.
Multiaxial Prestressing
When the prestressing tendons are parallel to more than two
axes, it is called Multiaxial Prestressing. For example,
prestressing of domes.
30. Pre-tensioning Systems and Devices
In pretensioning, the tension is applied to
the tendons before casting of the concrete.
31. Stages of Pre-tensioning
The various stages of the pre-tensioning operation
are summarized as follows.
1) Anchoring of tendons against the end abutments
2) Placing of jacks
3) Applying tension to the tendons
4) Casting of concrete
5) Cutting of the tendons.
33. Advantages
The relative advantages of pre-tensioning as
compared to post-tensioning are as follows.
Pre-tensioning is suitable for precast members
produced in bulk.
In pre-tensioning large anchorage device is not
present.
34. Disadvantages of Pre-tensioning
The relative disadvantages are as follows.
A prestressing bed is required for the pretensioning operation.
There is a waiting period in the prestressing bed,
before the concrete attains sufficient strength.
There should be good bond between concrete and
steel over the transmission length.
39. Post-tensioning Systems and Devices
In posttensioning, the tension is applied to the
tendons after hardening of the concrete.
40. Stages of Post-tensioning
The various stages of the post-tensioning operation
are summarized as follows.
1) Casting of concrete.
2) Placement of the tendons.
3) Placement of the anchorage block and jack.
4) Applying tension to the tendons.
5) Seating of the wedges.
6) Cutting of the tendons.
41.
42.
43. Advantages of Post-tensioning
The relative advantages of post-tensioning as
compared to pre-tensioning are as follows:
1)Post-tensioning is suitable for heavy cast-inplace members.
2)The waiting period in the casting bed is less.
3)The transfer of prestress is independent of
transmission length.
44. Devices
The essential devices for post-tensioning are as
follows.
1) Casting bed
2) Mould/Shuttering
3) Ducts
4) Anchoring devices
5) Jacks
6) Couplers (optional)
7) Grouting equipment (optional).
48. Concrete
Concrete is a composite material composed of
gravels or crushed stones (coarse aggregate), sand
(fine aggregate) and hydrated cement (binder). It
is expected that the student of this course is
familiar with the basics of concrete technology.
50. Aggregate
The coarse aggregate are granular materials
obtained from rocks and crushed stones. They
may be also obtained from synthetic material
like slag, shale, fly ash and clay for use in lightweight concrete.
The sand obtained from river beds or quarries is
used as fine aggregate. The fine aggregate
along with the hydrated cement paste fill the
space between the coarse aggregate.
51. The nominal maximum coarse aggregate size is
limited by the lowest of the following
quantities.
1) 1/4 times the minimum thickness of the
member
2) Spacing between the tendons/strands minus 5
mm
3) 40 mm.
52. Cement
In present day concrete, cement is a mixture of
lime stone and clay heated in a kiln to 1400 –
1600 ºC.
53. Water
Water used for mixing and curing shall be clean
and free from injurious amounts of oils, acids,
alkalis, salts, sugar, organic materials or other
substances that may be deleterious to concrete and
steel.
54. Admixtures
The admixtures can be broadly divided into two
types: chemical admixtures and mineral admixtures.
The common chemical admixtures are as follows.
1) Air-entraining admixtures
2) Water reducing admixtures
3) Set retarding admixtures
4) Set accelerating admixtures
5) Water reducing and set retarding admixtures
6) Water reducing and set accelerating admixtures.
55. The common mineral admixtures are as
follows.
1) Fly ash
2) Ground granulated blast-furnace slag
3) Silica fumes
4) Rice husk ash
5) Metakoline
56. Properties of Hardened Concrete
1) High strength
2) Durability
3) Stiffness
4) Minimum shrinkage and creep
57. High strength
The maximum grade of concrete is 60 MPa.
The minimum grades of concrete for
prestressed applications are as follows.
1)30 MPa for post-tensioned members
2)40 MPa for pre-tensioned members.
58. Stiffness of Concrete
The stiffness of concrete is required to estimate
the deflection of members. The stiffness is
given by the modulus of elasticity.
59. Durability of Concrete
The durability of concrete is of vital importance
regarding the life cycle cost of a structure. The
life cycle cost includes not only the initial cost
of the materials and labour, but also the cost of
maintenance and repair.
60. Creep of Concrete
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. Hence, the study of creep is
important in prestressed concrete to calculate the
loss in prestress.
The creep occurs due to two causes.
1. Rearrangement of hydrated cement paste
(especially the layered products)
2. Expulsion of water from voids under load
61. Shrinkage of Concrete
Shrinkage of concrete is defined as the contraction
due to loss of moisture. The study of shrinkage is
also important in prestressed concrete to calculate
the loss in prestress.
The shrinkage occurs due to two causes.
1. Loss of water from voids
2. Reduction of volume during carbonation
62. Grout
Grout is a mixture of water, cement and optional
materials like sand, water-reducing admixtures,
expansion agent and pozzolans. The water-tocement ratio is around 0.5. Fine sand is used to
avoid segregation.
63.
64. The desirable properties of grout are as
follows.
1) Fluidity
2) Minimum bleeding and segregation
3) Low shrinkage
4) Adequate strength after hardening
5) No detrimental compounds
6) Durable.
65. Prestressing Steel
The development of prestressed concrete was
influenced by the invention of high strength
steel. It is an alloy of iron, carbon, manganese
and optional materials. In addition to
prestressing steel, conventional non-prestressed
reinforcement is used for flexural capacity
(optional), shear capacity, temperature and
shrinkage requirements.
66. Wires
A prestressing wire is a single unit made of
steel. The nominal diameters of the wires are
2.5, 3.0, 4.0, 5.0, 7.0 and 8.0 mm. The different
types of wires are as follows.
1) Plain wire: No indentations on the surface.
2) Indented wire: There are circular or elliptical
indentations on the surface.
67. Strands
A few wires are spun together in a helical form to
form a prestressing strand. The different types of
strands are as follows.
1) Two-wire strand: Two wires are spun together
to form the strand.
2) Three-wire strand: Three wires are spun
together to form the strand.
3) Seven-wire strand: In this type of strand, six
wires are spun around a central wire. The central
wire is larger than the other wires.
68. Tendons
A group of strands or wires are placed together
to form a prestressing tendon. The tendons are
used in post-tensioned members.
Cables
A group of tendons form a prestressing cable.
The cables are used in bridges
69. Bars
A tendon can be made up of a single steel bar.
The diameter of a bar is much larger than that of
a wire. Bars are available in the following sizes:
10, 12, 16, 20, 22, 25, 28 and 32 mm.