Formwork is a temporary structure used to contain freshly poured concrete and shape it to the required dimensions. Proper formwork design and construction is critical to ensure concrete quality and structural performance. Common causes of formwork failure include improper stripping, inadequate bracing, excessive vibration, unstable supports, and poor concrete placement control. To prevent failures, formwork should be carefully inspected for defects, properly braced and supported, and able to withstand anticipated loads without excessive deformation. Worker safety must also be a top priority during all formwork operations.
Formwork is a temporary mold used to contain and shape wet concrete until it is cured, and gain sufficient strength to support its own weight. It is commonly made from timber or steel. Formwork must balance requirements like containment, strength, resistance to leakage, accuracy, ease of handling, finish, access for concrete, and economy. It is designed according to factors like the loads it will support, type of structure being built, and materials used. Formwork goes through stages of assembly, concrete placement, and stripping. Proper design, construction, and maintenance of formwork is important to produce high quality, safe concrete structures economically.
Formwork is a temporary mold into which concrete is poured and shaped. It must be strong enough to support the weight of wet concrete and construction loads. Common materials for formwork include timber, steel, plastic, and aluminum. Proper construction and removal of formwork is important for quality, safety, and economy of concrete structures. Failure to properly brace, support, or remove formwork can lead to collapse during construction.
The document discusses top-down construction, which is required when:
1) The distance between existing buildings and the new building line is small, requiring deep excavation and risking soil collapse.
2) It allows for more building and basement area, suitable for two or more basements.
3) The first basement slab acts as a strut, preventing soil collapse behind retaining walls.
The methodology involves:
1) Casting piles with dowels for retaining walls and slabs.
2) Excavating in stages and casting retaining wall panels with dowels between piles.
3) Pouring the first basement slab and then continuing excavation and construction from the bottom up
This document discusses shoring and underpinning methods used to provide temporary or permanent support to structures. Shoring provides temporary stability during construction or repairs using techniques like raking, flying, or dead shores made of timber or steel. Underpinning supports existing foundations by strengthening soils using pit, pile, or chemical methods to allow additions without disturbing the structure. Proper design, installation, and precautions are needed for both techniques.
The document discusses various methods for underwater repair of concrete structures. It describes six main methods: 1) Surface spalling repair which involves clearing damaged areas and applying cementitious mortar or epoxy. 2) Large scale repair for significant damage which requires careful material selection and formwork. 3) Preplaced aggregate concrete where aggregate is compacted and grouted in place. 4) Injection techniques using cement or epoxy grouts to fill cracks or voids. 5) Guniting or shotcrete application for large surface repairs. 6) Steel sleeve technique which places a sleeve around damaged piles or columns and fills the space with concrete. Proper preparation and material compatibility are essential for effective underwater concrete structure repairs.
The document discusses demolition techniques and provides details about various demolition methods. It defines demolition as the dismantling or wrecking of a building or structure using controlled methods. It notes that demolition is necessary when a structure is old, weak, or has exceeded its design life. The document outlines the demolition survey and plan process and describes factors that affect the selection of demolition methods. It provides details on various non-engineering and engineering demolition techniques, including manual demolition, wrecking ball, pusher arm, thermic lance, concrete sawing, deliberate collapse, pressure jetting, bursting, and implosion techniques. Safety measures for demolition are also discussed.
The document discusses the design of staircases. It begins by defining key components of staircases like treads, risers, stringers, etc. It then describes different types of staircases such as straight, doglegged, and spiral. The document outlines considerations for designing staircases like dimensions, loads, and structural behavior. It provides steps for geometric design, load calculations, structural analysis, reinforcement design, and detailing of staircases. Numerical examples are also included to illustrate the design process.
Formwork is a temporary mold used to contain and shape wet concrete until it is cured, and gain sufficient strength to support its own weight. It is commonly made from timber or steel. Formwork must balance requirements like containment, strength, resistance to leakage, accuracy, ease of handling, finish, access for concrete, and economy. It is designed according to factors like the loads it will support, type of structure being built, and materials used. Formwork goes through stages of assembly, concrete placement, and stripping. Proper design, construction, and maintenance of formwork is important to produce high quality, safe concrete structures economically.
Formwork is a temporary mold into which concrete is poured and shaped. It must be strong enough to support the weight of wet concrete and construction loads. Common materials for formwork include timber, steel, plastic, and aluminum. Proper construction and removal of formwork is important for quality, safety, and economy of concrete structures. Failure to properly brace, support, or remove formwork can lead to collapse during construction.
The document discusses top-down construction, which is required when:
1) The distance between existing buildings and the new building line is small, requiring deep excavation and risking soil collapse.
2) It allows for more building and basement area, suitable for two or more basements.
3) The first basement slab acts as a strut, preventing soil collapse behind retaining walls.
The methodology involves:
1) Casting piles with dowels for retaining walls and slabs.
2) Excavating in stages and casting retaining wall panels with dowels between piles.
3) Pouring the first basement slab and then continuing excavation and construction from the bottom up
This document discusses shoring and underpinning methods used to provide temporary or permanent support to structures. Shoring provides temporary stability during construction or repairs using techniques like raking, flying, or dead shores made of timber or steel. Underpinning supports existing foundations by strengthening soils using pit, pile, or chemical methods to allow additions without disturbing the structure. Proper design, installation, and precautions are needed for both techniques.
The document discusses various methods for underwater repair of concrete structures. It describes six main methods: 1) Surface spalling repair which involves clearing damaged areas and applying cementitious mortar or epoxy. 2) Large scale repair for significant damage which requires careful material selection and formwork. 3) Preplaced aggregate concrete where aggregate is compacted and grouted in place. 4) Injection techniques using cement or epoxy grouts to fill cracks or voids. 5) Guniting or shotcrete application for large surface repairs. 6) Steel sleeve technique which places a sleeve around damaged piles or columns and fills the space with concrete. Proper preparation and material compatibility are essential for effective underwater concrete structure repairs.
The document discusses demolition techniques and provides details about various demolition methods. It defines demolition as the dismantling or wrecking of a building or structure using controlled methods. It notes that demolition is necessary when a structure is old, weak, or has exceeded its design life. The document outlines the demolition survey and plan process and describes factors that affect the selection of demolition methods. It provides details on various non-engineering and engineering demolition techniques, including manual demolition, wrecking ball, pusher arm, thermic lance, concrete sawing, deliberate collapse, pressure jetting, bursting, and implosion techniques. Safety measures for demolition are also discussed.
The document discusses the design of staircases. It begins by defining key components of staircases like treads, risers, stringers, etc. It then describes different types of staircases such as straight, doglegged, and spiral. The document outlines considerations for designing staircases like dimensions, loads, and structural behavior. It provides steps for geometric design, load calculations, structural analysis, reinforcement design, and detailing of staircases. Numerical examples are also included to illustrate the design process.
Tall Structures
Usually structure or building having height more than 80m is considered as a tall structure.
Generally tall structure may be defined as one that because of its height it is affected by lateral.
Classification: 1. Multi storeyedresidential building.
2. Multi storeyedcommercial building.
3. Tall chimneys.
4. Transmission Towers
5. Cooling towers
Prestressed Concrete
•Prestressis defined as a method of applying pre-compression to control the stresses resulting due to external loads below the neutral axis of the beam tension developed due to external load which is more than the permissible limits of the plain concrete.
Demolition
•The action or process of destroying(demolishing)the building or other structures.
•In congested area, in particular, the quality of demolition technique becomes an essential element which determines the success of revitalization of city.
•In addition to efficiency in demolition, strategies must be adopted to avoid noise, vibration and dust which affect the surrounding environment and there must be efficient disposal of waste products
This presentation provides an overview of formwork, which is the mould used to support wet concrete until it cures. It discusses the requirements of good formwork including strength, rigidity, tight joints, and ease of removal. The economics of formwork are also covered, noting it can account for 30-100% of concrete costs depending on the project. The main types of formwork are then described - timber, steel, plywood, aluminum and plastic. Advantages and disadvantages of each type are listed. Construction details like propping, centering and stripping times are also summarized.
This document discusses various types of cracks that can occur in concrete structures. It begins by explaining that most cracks are caused by shrinkage as the concrete hardens. Cracks are then classified as either structural or non-structural. Non-structural cracks tend to be cosmetic while structural cracks can threaten safety. Several specific types of cracks are then described in detail, including those caused by sulfate attack, loading, plastic shrinkage, drying shrinkage, alkali-aggregate reaction, thermal effects, settlement, and corrosion of reinforcement steel. Factors that contribute to cracking and various prevention and repair measures are also outlined.
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.
The document describes the construction process for columns, slabs, and beams in reinforced concrete structures. It discusses the materials used and the typical steps involved, which include:
1) Layout and formwork installation
2) Placement of reinforcing steel based on structural designs
3) Pouring and finishing of concrete
4) Curing of concrete to gain full strength over 28 days
The columns transfer loads vertically through reinforced concrete that is mixed on site or delivered by ready-mix trucks. Slabs and beams are constructed through similar processes of steel reinforcement, formwork, concrete placement and curing.
Joints are easy to maintain and are less detrimental than uncontrolled or uneven cracks. Concrete expands & shrinks with variations in moisture and temp. The overall affinity is to shrink and this can cause cracking at an early age. Uneven cracks are unpleasant and difficult to maintain but usually do not affect the integrity of concrete.
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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.
This document discusses different types of reinforced concrete slabs, including one-way slabs, two-way slabs, flat slabs, and ribbed slabs. One-way slabs are supported on two sides and bend in one direction, while two-way slabs are supported on all four sides and bend in both directions. Flat slabs do not have beams and loads are transferred directly to columns, providing a plain ceiling. Ribbed slabs contain reinforced concrete ribs spaced no more than 1 meter apart between which the slab spans.
This document summarizes the key aspects of flat slab construction and design according to Indian code IS 456-2000. It defines flat slabs as slabs that are directly supported by columns without beams, and describes four common types based on whether drops and column heads are used. The main topics covered include guidelines for proportioning slabs and drops, methods for determining bending moments and shear forces, requirements for slab reinforcement, and an example problem demonstrating the design of an interior flat slab panel.
This document summarizes Indian Standard IS 4326:1993, which provides guidelines for earthquake-resistant design and construction of buildings. It covers terminology, general principles, special construction features, types of construction, categories of buildings, and masonry, timber, and precast construction. For masonry, it specifies use of strong materials and mortar, wall thickness, reinforcement, and strengthening with horizontal bands and vertical dowels. Vertical reinforcement is also required at wall corners and junctions.
The document discusses reinforced concrete columns, including their functions, failure modes, classifications, and design considerations. Columns primarily resist axial compression but may also experience bending moments. They can fail due to compression, buckling, or a combination. Design depends on whether the column is short or slender, braced or unbraced. Reinforcement is designed based on the column's expected loads and dimensions using methods specified in design codes like BS 8110.
The document discusses reinforced cement concrete (RCC), including its history, materials, specifications, and advantages/disadvantages. RCC uses steel reinforcement embedded in concrete to resist tensile, shear, and sometimes compressive stresses. François Coignet is considered a pioneer of RCC, building the first reinforced concrete structure in 1853. Proper proportions and mixing of cement, aggregates like sand and gravel, and water are needed to produce durable concrete. Precast concrete involves casting pieces off-site then transporting them for assembly.
Shear walls are vertical structural elements designed to resist lateral forces like winds and earthquakes. They work by transferring shear forces throughout their height and resisting uplift forces. Properly designed and constructed shear wall buildings are very stable and ductile, providing warnings before collapse during severe earthquakes. Common types of shear walls include reinforced concrete, plywood, and steel plate shear walls. Shear walls are an effective and efficient way to resist lateral loads in seismic regions.
The document discusses various types of construction defects such as cracks within structures and dampness defects. It provides 11 examples of cracking problems within structures like diagonal cracks in brick walls, horizontal cracks in mortar joints, random cracks in flooring, and cracks at joints between concrete and masonry. Each problem is described in terms of its causes and recommended remedies. It also discusses one example of a dampness problem involving dampness in ceilings below roof slabs, terraces or balconies and lists 6 potential causes such as improper roof slopes, choked rainwater pipes, lack of waterproofing of overhead tanks, and improper waterproofing treatment.
The document summarizes different methods of underpinning an existing foundation to support expansion of a building on the same land plot. It discusses five main underpinning methods: 1) Mass concrete underpinning which involves digging pits by hand and pouring concrete sequentially, 2) Helical piles which use steel shafts with helical flights screwed into the ground, 3) Micropiles which are small diameter drilled and grouted piles, 4) Jacked piles which involve driving steel pipes into the ground with a hydraulic jack, and 5) Bracket piles used for earth retention to support adjacent foundations during excavation. The document also lists potential causes of foundation failure such as poor drainage, weather conditions, poor soil conditions, transpiration
This document discusses prefabricated modular structures. Some key points:
1. Prefabricated structures have standardized components that are produced off-site in a controlled environment and then transported for assembly. This allows for faster, more efficient construction.
2. Precast concrete offers advantages like higher quality, less weather dependency, and unlimited design possibilities compared to site-cast construction.
3. There are different precast systems like large panel, frame, and lift-slab. Precast components include walls, floors, beams, and more.
This document provides an overview of the design of compression members (columns) in reinforced concrete structures. It discusses various types of columns based on reinforcement, loading conditions, and slenderness ratio. It describes the classification of columns as short or slender. The document also covers effective length, braced vs unbraced columns, codal provisions for reinforcement, and functions of longitudinal and transverse reinforcement. Key points include types of column reinforcement, minimum reinforcement requirements, cover requirements, and assumptions for the limit state of collapse under compression.
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.
The document discusses building maintenance, common defects, and remedial methods for RCC structures. It describes three main common defects: foundations, walls, and concrete/RCC frames. For foundations, common issues include differential settlement, uplift of shrinkage soil, and dampness. For walls, issues include cracking, dampness penetration, and failure during cyclones. For concrete frames, common problems discussed are seepage/leakage, spalling of concrete, and corrosion of steel reinforcement. The document provides detailed remedial methods and guidelines for investigating and classifying structural damage to determine appropriate restoration methods.
The document discusses building maintenance, common defects, and remedial methods for RCC structures. It describes three main common defects: foundations, walls, and concrete/RCC frames. For foundations, common issues include differential settlement, uplift of shrinkage soil, and dampness. For walls, issues include cracking, dampness penetration, and failure during cyclones. For concrete frames, common problems discussed are seepage/leakage, spalling of concrete, and corrosion of steel reinforcement. The document provides detailed remedial methods for addressing each of these defects.
Tall Structures
Usually structure or building having height more than 80m is considered as a tall structure.
Generally tall structure may be defined as one that because of its height it is affected by lateral.
Classification: 1. Multi storeyedresidential building.
2. Multi storeyedcommercial building.
3. Tall chimneys.
4. Transmission Towers
5. Cooling towers
Prestressed Concrete
•Prestressis defined as a method of applying pre-compression to control the stresses resulting due to external loads below the neutral axis of the beam tension developed due to external load which is more than the permissible limits of the plain concrete.
Demolition
•The action or process of destroying(demolishing)the building or other structures.
•In congested area, in particular, the quality of demolition technique becomes an essential element which determines the success of revitalization of city.
•In addition to efficiency in demolition, strategies must be adopted to avoid noise, vibration and dust which affect the surrounding environment and there must be efficient disposal of waste products
This presentation provides an overview of formwork, which is the mould used to support wet concrete until it cures. It discusses the requirements of good formwork including strength, rigidity, tight joints, and ease of removal. The economics of formwork are also covered, noting it can account for 30-100% of concrete costs depending on the project. The main types of formwork are then described - timber, steel, plywood, aluminum and plastic. Advantages and disadvantages of each type are listed. Construction details like propping, centering and stripping times are also summarized.
This document discusses various types of cracks that can occur in concrete structures. It begins by explaining that most cracks are caused by shrinkage as the concrete hardens. Cracks are then classified as either structural or non-structural. Non-structural cracks tend to be cosmetic while structural cracks can threaten safety. Several specific types of cracks are then described in detail, including those caused by sulfate attack, loading, plastic shrinkage, drying shrinkage, alkali-aggregate reaction, thermal effects, settlement, and corrosion of reinforcement steel. Factors that contribute to cracking and various prevention and repair measures are also outlined.
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.
The document describes the construction process for columns, slabs, and beams in reinforced concrete structures. It discusses the materials used and the typical steps involved, which include:
1) Layout and formwork installation
2) Placement of reinforcing steel based on structural designs
3) Pouring and finishing of concrete
4) Curing of concrete to gain full strength over 28 days
The columns transfer loads vertically through reinforced concrete that is mixed on site or delivered by ready-mix trucks. Slabs and beams are constructed through similar processes of steel reinforcement, formwork, concrete placement and curing.
Joints are easy to maintain and are less detrimental than uncontrolled or uneven cracks. Concrete expands & shrinks with variations in moisture and temp. The overall affinity is to shrink and this can cause cracking at an early age. Uneven cracks are unpleasant and difficult to maintain but usually do not affect the integrity of concrete.
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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.
This document discusses different types of reinforced concrete slabs, including one-way slabs, two-way slabs, flat slabs, and ribbed slabs. One-way slabs are supported on two sides and bend in one direction, while two-way slabs are supported on all four sides and bend in both directions. Flat slabs do not have beams and loads are transferred directly to columns, providing a plain ceiling. Ribbed slabs contain reinforced concrete ribs spaced no more than 1 meter apart between which the slab spans.
This document summarizes the key aspects of flat slab construction and design according to Indian code IS 456-2000. It defines flat slabs as slabs that are directly supported by columns without beams, and describes four common types based on whether drops and column heads are used. The main topics covered include guidelines for proportioning slabs and drops, methods for determining bending moments and shear forces, requirements for slab reinforcement, and an example problem demonstrating the design of an interior flat slab panel.
This document summarizes Indian Standard IS 4326:1993, which provides guidelines for earthquake-resistant design and construction of buildings. It covers terminology, general principles, special construction features, types of construction, categories of buildings, and masonry, timber, and precast construction. For masonry, it specifies use of strong materials and mortar, wall thickness, reinforcement, and strengthening with horizontal bands and vertical dowels. Vertical reinforcement is also required at wall corners and junctions.
The document discusses reinforced concrete columns, including their functions, failure modes, classifications, and design considerations. Columns primarily resist axial compression but may also experience bending moments. They can fail due to compression, buckling, or a combination. Design depends on whether the column is short or slender, braced or unbraced. Reinforcement is designed based on the column's expected loads and dimensions using methods specified in design codes like BS 8110.
The document discusses reinforced cement concrete (RCC), including its history, materials, specifications, and advantages/disadvantages. RCC uses steel reinforcement embedded in concrete to resist tensile, shear, and sometimes compressive stresses. François Coignet is considered a pioneer of RCC, building the first reinforced concrete structure in 1853. Proper proportions and mixing of cement, aggregates like sand and gravel, and water are needed to produce durable concrete. Precast concrete involves casting pieces off-site then transporting them for assembly.
Shear walls are vertical structural elements designed to resist lateral forces like winds and earthquakes. They work by transferring shear forces throughout their height and resisting uplift forces. Properly designed and constructed shear wall buildings are very stable and ductile, providing warnings before collapse during severe earthquakes. Common types of shear walls include reinforced concrete, plywood, and steel plate shear walls. Shear walls are an effective and efficient way to resist lateral loads in seismic regions.
The document discusses various types of construction defects such as cracks within structures and dampness defects. It provides 11 examples of cracking problems within structures like diagonal cracks in brick walls, horizontal cracks in mortar joints, random cracks in flooring, and cracks at joints between concrete and masonry. Each problem is described in terms of its causes and recommended remedies. It also discusses one example of a dampness problem involving dampness in ceilings below roof slabs, terraces or balconies and lists 6 potential causes such as improper roof slopes, choked rainwater pipes, lack of waterproofing of overhead tanks, and improper waterproofing treatment.
The document summarizes different methods of underpinning an existing foundation to support expansion of a building on the same land plot. It discusses five main underpinning methods: 1) Mass concrete underpinning which involves digging pits by hand and pouring concrete sequentially, 2) Helical piles which use steel shafts with helical flights screwed into the ground, 3) Micropiles which are small diameter drilled and grouted piles, 4) Jacked piles which involve driving steel pipes into the ground with a hydraulic jack, and 5) Bracket piles used for earth retention to support adjacent foundations during excavation. The document also lists potential causes of foundation failure such as poor drainage, weather conditions, poor soil conditions, transpiration
This document discusses prefabricated modular structures. Some key points:
1. Prefabricated structures have standardized components that are produced off-site in a controlled environment and then transported for assembly. This allows for faster, more efficient construction.
2. Precast concrete offers advantages like higher quality, less weather dependency, and unlimited design possibilities compared to site-cast construction.
3. There are different precast systems like large panel, frame, and lift-slab. Precast components include walls, floors, beams, and more.
This document provides an overview of the design of compression members (columns) in reinforced concrete structures. It discusses various types of columns based on reinforcement, loading conditions, and slenderness ratio. It describes the classification of columns as short or slender. The document also covers effective length, braced vs unbraced columns, codal provisions for reinforcement, and functions of longitudinal and transverse reinforcement. Key points include types of column reinforcement, minimum reinforcement requirements, cover requirements, and assumptions for the limit state of collapse under compression.
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.
The document discusses building maintenance, common defects, and remedial methods for RCC structures. It describes three main common defects: foundations, walls, and concrete/RCC frames. For foundations, common issues include differential settlement, uplift of shrinkage soil, and dampness. For walls, issues include cracking, dampness penetration, and failure during cyclones. For concrete frames, common problems discussed are seepage/leakage, spalling of concrete, and corrosion of steel reinforcement. The document provides detailed remedial methods and guidelines for investigating and classifying structural damage to determine appropriate restoration methods.
The document discusses building maintenance, common defects, and remedial methods for RCC structures. It describes three main common defects: foundations, walls, and concrete/RCC frames. For foundations, common issues include differential settlement, uplift of shrinkage soil, and dampness. For walls, issues include cracking, dampness penetration, and failure during cyclones. For concrete frames, common problems discussed are seepage/leakage, spalling of concrete, and corrosion of steel reinforcement. The document provides detailed remedial methods for addressing each of these defects.
This chapter discusses structural concrete design. It covers properties of concrete and reinforcing steel, proportioning and mixing concrete, flexural design of beams and slabs, columns under bending and axial load, shear and torsion, development of reinforcement, two-way systems, frames, brackets and corbels, footings, walls, and defining terms. The chapter aims to promote a unified approach to structural concrete design across different design approaches, techniques, and codes worldwide.
This document summarizes chapter 4 of the book "Structural Concrete Design" which covers various topics related to designing structural concrete including:
- Properties of concrete and reinforcing steel such as compressive strength, modulus of elasticity, creep, and tensile strength.
- Proportioning and mixing concrete, including using admixtures.
- Flexural and strength design of beams, slabs, columns, shear/torsion, development of reinforcement, two-way systems, frames, brackets/corbels, and footings.
- Additional concrete types such as lightweight and high-strength concrete.
presentation on retro fit and repair methodsKumarS250747
This document discusses repair, restoration, and retrofitting of structures. It defines key terms like repair, restoration, rehabilitation, and retrofitting. It describes common types of structural distress like cracking, corrosion, settlement, and provides examples of repair techniques. Case studies are presented on repairing industrial structures affected by differential settlement through soil excavation and replacement, and strengthening of slabs through jacketing and overlays. Basic retrofitting techniques like beam jacketing are also introduced.
Building crack,types,causes & its repairingGAUTAMSWALA
The document discusses different types of cracks in concrete structures, their causes, and repair methods. It describes structural cracks as wider than 3mm and caused by poor construction practices or overloading. Non-structural cracks are thinner and caused by moisture, thermal movement, or vegetation. Various crack repair techniques are outlined, including epoxy injection to fill hairline cracks, routing and sealing, stitching with metal anchors, grouting, and applying an overlay. The conclusion states it is impossible to completely prevent cracks but their development can be minimized by considering construction materials and techniques.
1) Concrete structures can develop defects due to poor construction practices, poor quality control, and poor structural design and detailing.
2) Common defects include honeycombs caused by improper vibration and workability, cracks due to various stresses, and efflorescence caused by leaching of lime compounds.
3) Defects can be repaired through methods like using non-shrink grouts for honeycombs, grinding surfaces for minor formwork errors, and epoxy bonding, routing, resin injection, or grouting for cracks.
Shuttering in concrete construction is used as a mould for a structure in which fresh concrete is poured to harden subsequently curing
It is a part of formwork, or you may call it as derivative of formwork. Shuttering is a vertical temporary arrangement which is arranged to bring concrete in a desired shape. or Formwork which supports vertical arrangement is known as shuttering.
This document provides information on formwork used for constructing concrete structures. It discusses the different types of formwork including wooden, plywood, steel and combined forms. It also describes requirements for proper formwork like being waterproof and strong enough to support loads. Common formwork systems are described for columns, beams, slabs, stairs and walls. Standards for stripping formwork from concrete structures are also outlined according to the Indian Standard code.
Formwork is used to support wet concrete until it cures and can support itself. It must be strong yet allow concrete to be placed accurately to shape. Common materials include timber, plywood, steel, aluminum and plastics. Proper formwork design considers strength, containment, leakage prevention, finish quality, and economics. Specialized formwork like climbing, sliding, and tunnel forms improve efficiency for structures like walls, columns, and buildings. Proper formwork selection and construction is essential for quality, safety, and cost-effectiveness in concrete projects.
Formwork is a temporary structure used to support wet concrete until it cures and can support itself. There are different types of formwork materials including timber, steel, and glass reinforced plastic. Proper formwork design and construction helps ensure safety, cost-effectiveness and quality of the finished concrete surface. Common causes of formwork failure include inadequate bracing, vibration, unstable soil or improper stripping. Safety precautions like secure fixing and inspections are important to prevent accidents. Permanent formwork is part of the permanent structure and remains in place for the life of the building, offering advantages like reduced construction time and costs.
Retrofitting rehabilitation and repair of structureKumarS250747
The document provides information on repair, restoration, and retrofitting of structures. It defines key terms like repair, restoration, rehabilitation, and retrofitting. It describes common types of structural distress like cracking, honeycombing, corrosion, and settlement. It also includes 3 case studies on repair works: 1) Settlement of industrial floors involving soil excavation and replacement, 2) Restoration of a residential building affected by unequal settlement, and 3) Treatment for seepage in a basement. The document is a useful reference for understanding various repair and retrofitting techniques.
special concrete and high performance concreteErankajKumar
GROUTING OF CONCRETE, advantage ofGrouting,Characteristics of Grouting, GUNTING OF
CONCRETE, Application of Guniting, Properties of Guniting, advantage and disadvantage of Guniting, UNDERWATER CONCRETING, Properties of underwater concrete, METHODS OF UNDERWATER CONCRETE, advantage and disadvantage of underwater concrete, HOT WEATHERING CONCRETE, precautions, COLD WEATHER CONCRETING, PUMPABLE CONCRETE, Requirements of Mix Design for Pumpable Concrete, Ready Mixed Concrete RMC, Types of Ready Mixed Concrete, advantage and disadvantage of ready mixed concrete, introduction in High performance concrete HPC, selection of materials, behaviour of fresh high performance concrete HPC , behaviour of Hardened High performance concrete HPC when to use High performance concrete HPC , application of HPC , Advantage of HPC , Limitations of HPC
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This document provides guidelines for identifying and controlling visible effects of consolidation on precast or cast-in-place formed concrete surfaces. It includes a summary of direct and indirect causes of surface imperfections such as honeycombing and air voids. The document emphasizes that proper planning, trained personnel, and consolidation techniques can minimize undesirable surface effects. It also contains photographs illustrating common concrete surface blemishes.
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2. Formwork is a complete system of
temporary structure built to
contain fresh concrete so as to
form it into the required shape and
dimensions and to support it until
it hardens sufficiently to become
self supporting. It includes the
surface in contact with the
concrete and all the necessary
supporting structure.
DEFINITION AS PER
IS 6461 ( PART 5)- 1972
3. Fresh concrete reflects the shape, texture
and finish of the surface against which it is
cast. The formwork system is critical to the
final appearance of the hardened concrete.
Any imperfection in the formwork, is
reflected when the formwork is stripped off.
“Concrete Expresses what Form Reflects”
is the Cardinal Principle of Formwork
Design
4. Practices used in all
stages of Concrete
Construction affect both
the appearance and
structural performance
of the Concrete.
When the concrete is
exposed then the role of
Formwork also attains
higher and greater
importance along with
structural performance.
7. Quality : Strength, Rigidity, Position,
Dimensions.
Safety : For both the workers and the
structure.
Economy : The least cost consistent with
quality and safety requirements.
OBJECTIVES OF FORM BUILDINGOBJECTIVES OF FORM BUILDING
Engineered Formwork in structures is required to
support loads such as fresh concrete, construction
materials, equipment, workers, impacts etc. and
should be able to withstand all these loads without
collapse or excessive deflection.
8. Formwork
Economics
Largest cost component of a concrete
structural frame
Cost of formwork exceeds the cost of the
concrete and/or steel
Design of formwork - proper design
considerations lead to a significant cost
saving.
Formwork efficiencies accelerate the
construction schedule
Increase jobsite productivity, improved
safety, better quality and reduced
potential for errors
Formwork cost accounts for 40 to 60
percent of the cost of the concrete frame
and for approximately 10 percent of the
total building cost
9. NUMBER OF
USES
COST PER
UNIT AREA
1 1.00
2 0.62
3 0.50
4 0.44
5 0.40
6 0.37
7 0.36
8 0.34
9 0.32
Effect of Reuse
on Concrete
Formwork Cost
Formwork
Economics
10. DEAD LOAD IMPOSED LOAD EXTERNAL LOAD
Self Weight of
Formwork
Lateral pressure due
to fresh concrete
Location Based
Weight of fresh
Concrete
Equipment placed
on Formwork
Wind Load
Weight of
Reinforcement
impact due to
vibrator operation
Snow Load
Any other
temporary work
supprted by
Formwork
Impact due to
Pumping of concrete
in case of RMC
Water Pressure
Heaping of concrete
before spreading
Earth Pressure
LOADS ON FORMWORK
11. DESIGN OF FORMWORK
Economy in formwork begins with the design of a
structure
And continues through the selection of form
materials, erection, stripping, care of forms
between reuses, and reuse of forms
It is possible to modify the design slightly to
achieve economy without impairing the usability
of the structure
The designer can integrate constructability into
the project by allowing three basic concepts:
Design repetition
Dimensional standards
Dimensional consistency
12. DESIGN CONSIDERATIONS
Formwork must be designed to
adequately support the loads as
discussed in the previous slide without
any deformation.
IS 875 (Part1) 1987 ; recommends
actual assessment of dead loads. In
the absence of which, 500 N/m2
can be
considered. Weight of freshly placed
concrete shall not be less than 26
kN/m2
. IS 875, Part 2 for assessing
imposed loads.
In case of moisture absorbing filler
materials, design should account for at
least 30% increase in weight of these
13. Form releasing agents to be selected
carefully to facilitate easy stripping,
avoiding damages and de-colorization
of the surface.
Greater care to be taken with respect
to tall elements as lateral pressure
from the fluid concrete is high and may
result in formwork deflections.
Slower rate of concrete placing in
Winter and faster rate of placing in
Summer is recommended.
Also to bear in mind that shallow
elements like beams can expel the
entrapped air more easily than tall
14. Care should be taken to ensure minimum
wall thickness in respect of proper
compaction, cover etc. to avoid
honeycombing.
Concrete accumulation on slab while
concreting cannot be more than 3 times
the depth of slab per sqm. In such cases,
code recommends 750 kN/m2
.
Permitted deflection in Formwork cannot
exceed 3mm as per IS 14687-1999.
No formwork to be released until the concrete
element has developed enough strength of at
least twice the stress to which concrete may be
subjected at the time of removal of form work.
15. # Strength # Ease of
stripping
# Stiffness # Patterns if
any
# Tolerance # Releasing agent
# Water tightness # Curing Method
# Robustness # Material
Suitability
# Surface Finish # Stripping
Time
Factors To Be Considered While
Designing Formwork In General
16. Requirements of a Good
Formwork
• Must be Water Proofed, so as to
prevent absorption of water from
the
concrete.
• Must be strong enough to sustain
the
live loads, Impact loads and dead
loads during the process of
concreting.
• Should be light and stiff.
• Should be easily removable and
reusable.
Should reflect the desired surface.
17. How Formwork Affects Concrete
Quality
Size, Shape, Line, Level, looks and Plumb.
The forms must be:
Sufficiently rigid under the construction
loads to maintain the designed shape of
the concrete,
Stable and strong enough to maintain large
members in alignment, and
Substantially constructed to withstand
handling and reuse without losing their
dimensional integrity.
The formwork must remain in place until the
concrete is strong enough to carry its own
weight, or the finished structure may be
damaged.
18. Repetition – increases productivity of crew
involved in making formwork.
External Disruptions like bad weather, accidents,
labor strike etc. decrease the productivity.
Internal Disruptions like improper sequencing,
untimely material supply/delivery, poor
coordination decrease productivity.
Rework is always detrimental to crew
productivity. It not only decreases productivity,
but also increases the cost. Formwork shape,
size, height, assembly and placement method
etc. also have significant impact on productivity.
Factors Affecting Productivity of
Formwork
28. Formwork Failure – CAUTION !!
Formwork failure occurs primarily while
placing concrete. In some cases, failure of
one support may lead to total collapse due
to cascading affect.
In most cases Formwork failures give
sufficient indications and GOOD engineers
are able to notice these. For Example;
Creaking sound while placing of
concrete.
Deflections of forms in localised
areas.
Buckling of formwork supports
29. The main causes of formwork failure in commonThe main causes of formwork failure in common
can be put under these 6 heads:can be put under these 6 heads:
1- Improper stripping and shore removal
2- Inadequate bracing
3- Excess Vibration
4- Unstable soil, shoring and out of plumb
5- Inadequate control of concrete placement
6- Lack of attention to formwork details.
30. • Rotation of stringers, beams or joists
• Deficient connections - Inadequate bracing or ties
• Single post shores (usually with flat heads)
• Shores on slopes or supporting sloping slabs
• Untested or misused proprietary components
• Unauthorized variations / poor workmanship
• Defective equipment - Differential settlement
• Cantilever loading - Vibration and impact
• Excessive rate of placing of concrete
• Improper sequence Of placing of concrete
COMMON CAUSES OF FORM WORKCOMMON CAUSES OF FORM WORK
FAILUREFAILURE
31. SURFACESURFACE
FINISHESFINISHES
Smooth Finish : Generally achieved by using
smooth finish form face such as Coated
Ply, Stainless or MS sheet etc. American
Codes classify Smooth Finish under
Class1 to Class 5. They also attach
parameters like ; Blow holes,
Flatness, Surface undulation, Face step,
plumb and deflection.
Textured Finish : This finish is achieved by providing
desired patterns on the form surface.
Textured finish is also obtained
subsequently using special tools.
Stained finish : This finish is obtained by
staining the form Surface.
Form-Liner Finish : Obtained by using permanent or
temporary form-liners.
33. DEFECTS IN FORMWORKDEFECTS IN FORMWORK
(1)(1)
1. Impermeable Formwork : Blow holes
2. Joint Leaks : Honeycombing / Grout
loss
3. Deformed Formwork : Misalignment
4. Poor thermal insulation : Plastic Cracking
5. Inadequate taper : Scaling and
Chipping
6. Wrong Form releasing : Color variation
agent
TIP : If concrete is placed in stages toTIP : If concrete is placed in stages to
reduce the lateral pressure, thenreduce the lateral pressure, then
placement methods are to be plannedplacement methods are to be planned
properly in respect of joints.properly in respect of joints.
34. 8. Stains, Rust, dirt etc. : Contamination
9. Retarder on form surface : Retardation
dusting.
10. Long Sun Exposure : Surface gets affected by
weathering and
starts giving away the
dust.
11. Oil as releasing agent : Affects bonding of
plaster
12. Lack of bracing : The whole system
fails to work as One single
supporting system.
13. Gaps in floor forms : Results in slurry leaking,
no cover, exposure of rebar.
14. Rebar touching form : Improper cover, exposed to
rust and deterioration of
concrete.
DEFECTS IN FORMWORKDEFECTS IN FORMWORK
(2)(2)
35. PREVENTING FORMWORK FAILURESPREVENTING FORMWORK FAILURES
CHECK LISTCHECK LIST
# Check whether right shuttering material is used
or not.
# Check whether forms used are free from defects
such
rusting, damages, dents, etc.
# Check whether the form work free from gaps to
ensure
water tightness.
# Check whether side shuttering of slabs and
beams are
properly fixed with stiffeners to avoid any
displacement, deformation, bulging etc.,
# Check whether right mould releasing agent is
used
36. PREVENTING FORMWORK FAILURESPREVENTING FORMWORK FAILURES
CHECK LISTCHECK LIST
# Check whether line, level and other parameters
are
correct.
# Check whether camber is provided in the form
work as
per design.
# Check whether de-shuttering can be done
keeping the
form work cycle in mind.
# Check whether duct boxes, sunken areas are
taken
care.
# Check line, level etc. once again after
reinforcement
37. PREVENTING FORMWORK FAILURESPREVENTING FORMWORK FAILURES
CHECK LISTCHECK LIST
In case of Concrete being poured by RMC,
ensure
whether extra supports are provided to
withstand
the impact pressure.
Check whether tie rodstie rods have been provided
for deeper sections.
Instruct all the concerned about the period
of de-shuttering specifically. This is very vital
in case of post tensioned slabs.
Check whether form surface is cleaned and
form releasing agent applied properly before
allowing tying of reinforcing steel.
38. The safety of workers is of prime concern.
Prepare a formwork plan that includes detailed
drawings, specifications for fabricating, erecting,
and dismantling of the formwork – by competent
engineer.
Follow all codes and ordinances and regulations
pertaining to formwork, shoring, and scaffolding.
Survey the jobsite for hazards, such as loose earth
fills, ditches, debris, overhead wires, and unguarded
openings Ensure adequate fall protection.
Inspect all shoring and scaffolding before using it.
Make a thorough check of the formwork system
after it is erected and immediately before a pour.
PREVENTING FORMWORK FAILURESPREVENTING FORMWORK FAILURES
CHECK LISTCHECK LIST
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