Helical reinforcement, also known as spiral reinforcement, is used in circular concrete columns. It consists of longitudinal bars enclosed within a continuously wound spiral reinforcement. Helical reinforcement is sometimes designed instead of normal links for columns because it provides increased strength and ductility. The spiral reinforcement acts compositely with the concrete core and allows the column to sustain higher loads than those with normal links. It also minimizes the risk of stirrups opening during seismic events. The document then provides details on the design of helical reinforcement for short concrete columns, including governing equations and an example problem.
This document discusses the design of compression members subjected to axial load and biaxial bending. It introduces the concept of biaxial eccentricities and explains that columns should be designed considering possible eccentricities in two axes. The document outlines the method suggested by IS 456-2000, which is based on Breslar's load contour approach. It relates the parameter αn to the ratio of Pu/Puz. Finally, it provides a step-by-step process for designing the column section, which involves determining uniaxial moment capacities, computing permissible moment values from charts, and revising the section if needed. It also briefly mentions the simplified method according to BS8110.
information on types of beams, different methods to calculate beam stress, design for shear, analysis for SRB flexure, design for flexure, Design procedure for doubly reinforced beam,
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 limit state design of reinforced concrete structures. It introduces limit states as conditions where the structure becomes unfit for use, including limit states of strength and serviceability. Limit state design involves characterizing loads and resistances as random variables and using partial safety factors on loads and resistances to achieve a target reliability. The document outlines the general principles of limit state design according to Indian Standard code IS 800, including defining actions, factors governing strength limits, and serviceability limits related to deflection, vibration and durability.
This document provides information on the structural design of a simply supported reinforced concrete beam. It includes:
- A list of students enrolled in an elementary structural design course.
- Equations and diagrams showing the forces and stresses in a reinforced concrete beam with a singly reinforced bottom section.
- Limits on the maximum depth of the neutral axis according to the grade of steel.
- Examples of analyzing the stresses and determining steel reinforcement for a given beam cross-section.
- A design example calculating the dimensions and steel reinforcement for a rectangular beam with a factored uniform load.
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.
Diaphragm wall: Construction and DesignUmer Farooq
The document discusses diaphragm walls, which are concrete or reinforced concrete walls constructed below ground using a slurry-supported trench method. Diaphragm walls can reach depths of 150 meters and widths of 0.5-1.5 meters. They are constructed using tremie installation or pre-cast concrete panels. Diaphragm walls are suitable for urban construction due to their quiet installation and lack of vibration. The document discusses different types of diaphragm walls based on materials and functions, and provides details on their design, construction process, and material requirements.
This document discusses the design of compression members subjected to axial load and biaxial bending. It introduces the concept of biaxial eccentricities and explains that columns should be designed considering possible eccentricities in two axes. The document outlines the method suggested by IS 456-2000, which is based on Breslar's load contour approach. It relates the parameter αn to the ratio of Pu/Puz. Finally, it provides a step-by-step process for designing the column section, which involves determining uniaxial moment capacities, computing permissible moment values from charts, and revising the section if needed. It also briefly mentions the simplified method according to BS8110.
information on types of beams, different methods to calculate beam stress, design for shear, analysis for SRB flexure, design for flexure, Design procedure for doubly reinforced beam,
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 limit state design of reinforced concrete structures. It introduces limit states as conditions where the structure becomes unfit for use, including limit states of strength and serviceability. Limit state design involves characterizing loads and resistances as random variables and using partial safety factors on loads and resistances to achieve a target reliability. The document outlines the general principles of limit state design according to Indian Standard code IS 800, including defining actions, factors governing strength limits, and serviceability limits related to deflection, vibration and durability.
This document provides information on the structural design of a simply supported reinforced concrete beam. It includes:
- A list of students enrolled in an elementary structural design course.
- Equations and diagrams showing the forces and stresses in a reinforced concrete beam with a singly reinforced bottom section.
- Limits on the maximum depth of the neutral axis according to the grade of steel.
- Examples of analyzing the stresses and determining steel reinforcement for a given beam cross-section.
- A design example calculating the dimensions and steel reinforcement for a rectangular beam with a factored uniform load.
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.
Diaphragm wall: Construction and DesignUmer Farooq
The document discusses diaphragm walls, which are concrete or reinforced concrete walls constructed below ground using a slurry-supported trench method. Diaphragm walls can reach depths of 150 meters and widths of 0.5-1.5 meters. They are constructed using tremie installation or pre-cast concrete panels. Diaphragm walls are suitable for urban construction due to their quiet installation and lack of vibration. The document discusses different types of diaphragm walls based on materials and functions, and provides details on their design, construction process, and material requirements.
The document discusses different methods of designing concrete structures, focusing on the limit state method. It describes the limit state method's goal of achieving an acceptable probability that a structure will not become unsuitable for its intended use during its lifetime. The document then discusses stress-strain curves for concrete and steel. It covers stress block parameters and equations for calculating the depth of the neutral axis and moment of resistance for singly reinforced concrete beams. The document concludes by providing examples of analyzing an existing beam section and designing a new beam section.
Slabs are structural members that support transverse loads and transfer them to supports via bending. They are commonly used as floors and roofs. One-way slabs bend in only one direction across the shorter span like a wide beam, while two-way slabs bend in both directions if the ratio of longer to shorter span is less than or equal to 2. Design of one-way slabs involves calculating bending moment and shear force, selecting reinforcement ratio and bar size, and checking deflection, shear, and development length.
This document provides guidance on the design of lacing and battens for built-up compression members. It discusses the key design considerations and calculations for both single and double lacing systems, including the angle of inclination, slenderness ratio, effective lacing length, bar width and thickness. Similar guidelines are given for battens, covering spacing, thickness, effective depth, transverse shear and overlap. The document also includes an example problem on designing a slab foundation for a column with given load and material properties.
The document discusses code provisions for calculating the effective span of slabs according to IS 456. It describes how to calculate the effective span for simply supported, continuous, and cantilever members. It also discusses load assumptions, reinforcement cover requirements, deflection limits, and provides an overview of one-way slabs, two-way slabs, flat slabs, and flat plates.
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Various design philosophies have been invented in the different parts of the world to design RCC structures. In 1900 theory by Coignet and Tedesco was accepted and codified as Working Stress Method. The Working Stress Method was in use for several years until the revision of IS 456 in 2000.
What are the Various Design Philosophies?
Working Stress Method
limit state method
ultimate load method
#civil insider
Footings are structural members that support columns and walls and transmit their loads to the soil. Different types of footings include wall footings, isolated/single footings, combined footings, cantilever/strap footings, continuous footings, rafted/mat foundations, and pile caps. Footings must be designed to safely carry and transmit loads to the soil while meeting code requirements regarding bearing capacity, settlement, reinforcement, and shear strength. A proper footing design involves determining loads, allowable soil pressure, reinforcement requirements, and assessing settlement.
This document discusses the design of flat slab structures. It begins by defining a flat slab as a type of slab supported directly on columns without beams. It then provides details on the types of flat slabs, their common uses in buildings, and benefits such as flexibility in layout and reduced construction time. The document goes on to discuss key design considerations for flat slabs including thickness, drops, column heads, and methods of analysis. It focuses on the direct design method and provides limitations for its use.
This document summarizes the design of a reinforced concrete overhead water tank located in Kalyani, West Bengal, India to serve a population of 1500 people. Key aspects of the design include a diameter of 12 meters, total height of 5 meters, capacity of 540000 liters, and a raft foundation. Load calculations and analysis of the dome shape determine that the meridional and hoop stresses are within code limits for the minimum M30 grade concrete. Nominal tensile reinforcement of 6-8mm bars at 180mm centers in both directions is sufficient. Design codes and references used are cited.
Footings are structural members that support columns and walls and transmit their loads to the soil in a way that does not exceed the soil's load bearing capacity or cause excessive settlement or rotation. There are two main types of isolated column footings: pad footings and sloped footings. The design process for isolated footings includes determining the size, net upward pressure, bending moment, depth, reinforcement, and load transfer requirements. The example provides specifications to design an isolated square footing to support a 400mm x 400mm column with an axial load of 800kn using M-20 concrete and Fe-250 steel, accounting for a soil bearing capacity of 120kn/m2.
This document provides information on industrial buildings, including their components and factors to consider in design. Key points include:
- Industrial buildings are used for manufacturing and storage by industries and include steel plants, warehouses, and factories.
- Site selection considers access, raw materials, utilities, land characteristics, and transportation.
- Major components include the roof, trusses, purlins, girts, bracing, and foundations.
- Design considerations cover roofing/wall materials, bay widths, structural framing, truss configurations, and bracing to resist lateral loads.
Circular slabs are commonly used as roofs or floors with a circular plan, such as water tanks. They experience bending stresses in two perpendicular directions - radially and circumferentially. Reinforcement is provided as a mesh of bars with equal cross-sectional area in both directions. Near the edges, additional radial and circumferential reinforcement may be needed if edge stresses are significant. Circular slabs are analyzed based on elastic theory, and deflect into a saucer shape under uniform loads, developing tensile and compressive stresses on the convex and concave surfaces respectively. Reinforcement must be provided in both radial and circumferential directions near the convex surface.
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.
This document provides design requirements for lacing and battening systems used in steel structural elements. It discusses two types of lacing systems - single and double. It outlines 9 design requirements for lacing per Indian code IS 800, including angle of inclination, slenderness ratio, effective length, width/thickness, transverse shear force, strength checks, and end connections. It also discusses 7 design requirements for battening systems, including transverse shear force calculation, slenderness ratio, spacing, thickness, effective depth, overlap for welded connections, and notes battening offers less shear resistance than lacing.
This document provides instruction on analyzing three-hinged arches. It defines a three-hinged arch as a statically determinate structure with three hinges: two at the supports and one at the crown. The document describes how to determine the reactions of a three-hinged arch under a concentrated load using equations of static equilibrium. It presents an example problem showing how bending moment is reduced in a three-hinged arch compared to a simply supported beam carrying the same load.
This document discusses the design of two-way slabs. It defines a two-way slab as having a ratio of long to short spans of less than 2. The main types of two-way slabs described are flat slabs with drop panels, two-way slabs with beams, flat plates, and waffle slabs. The basic steps of two-way slab design are outlined, including choosing the slab type and thickness, the design method, calculating moments, determining reinforcement, and checking shear strength. Two common design methods are described: the direct design method which uses coefficients, and the equivalent frame method which analyzes frames cut between columns.
This document discusses different types of columns used in construction. It defines a column as a structural member subjected to compressive axial loads. Columns are classified as long, short, or intermediate based on their length-to-minimum radius of gyration ratio. Long columns have a ratio greater than 50, short columns less than 15-50, and intermediate between 30-100. The document provides examples of column types and discusses effective length, radius of gyration, buckling load, and Euler's formula for calculating crippling load.
The document provides information about caissons, which are watertight structures used in construction projects involving excavation below water levels. It discusses different types of caissons including box caissons, open or well caissons, pneumatic caissons, and multiple well or monolith caissons. Methods of constructing and sinking each type are described. Advantages and uses of caissons are outlined. Health risks associated with working under compressed air in pneumatic caissons, known as caisson sickness, are also summarized.
The document provides details on the design procedure for beams. It discusses estimating loads, analyzing beams to determine shear forces and bending moments, and designing beams. The design process involves selecting the beam size and shape, calculating the effective span, determining critical moments and shears, selecting reinforcement, and checking requirements such as shear capacity, deflection limits, and development lengths. An example problem demonstrates designing a singly reinforced concrete beam with a span of 5 meters to support a working live load of 25 kN/m.
This document discusses the design of compression members under uniaxial bending. It notes that columns are rarely under pure axial compression due to eccentricities from rigid frame action or accidental loading. Columns can experience uniaxial or biaxial bending based on the loading. The behavior depends on the relative magnitudes of the bending moment and axial load, which determine the position of the neutral axis. Methods for designing eccentrically loaded short columns include using equations that calculate the neutral axis position and failure mode, or using interaction diagrams that graphically show the safe ranges of moment and axial load.
The document discusses the reinforcement requirements and design process for axially loaded columns. It provides guidelines on the minimum longitudinal and transverse reinforcement, including the pitch and diameter of lateral ties. Examples are given to calculate the ultimate load capacity of rectangular and circular columns based on the grade of concrete and steel. Design assumptions and checks for minimum eccentricity are also outlined.
The document discusses different methods of designing concrete structures, focusing on the limit state method. It describes the limit state method's goal of achieving an acceptable probability that a structure will not become unsuitable for its intended use during its lifetime. The document then discusses stress-strain curves for concrete and steel. It covers stress block parameters and equations for calculating the depth of the neutral axis and moment of resistance for singly reinforced concrete beams. The document concludes by providing examples of analyzing an existing beam section and designing a new beam section.
Slabs are structural members that support transverse loads and transfer them to supports via bending. They are commonly used as floors and roofs. One-way slabs bend in only one direction across the shorter span like a wide beam, while two-way slabs bend in both directions if the ratio of longer to shorter span is less than or equal to 2. Design of one-way slabs involves calculating bending moment and shear force, selecting reinforcement ratio and bar size, and checking deflection, shear, and development length.
This document provides guidance on the design of lacing and battens for built-up compression members. It discusses the key design considerations and calculations for both single and double lacing systems, including the angle of inclination, slenderness ratio, effective lacing length, bar width and thickness. Similar guidelines are given for battens, covering spacing, thickness, effective depth, transverse shear and overlap. The document also includes an example problem on designing a slab foundation for a column with given load and material properties.
The document discusses code provisions for calculating the effective span of slabs according to IS 456. It describes how to calculate the effective span for simply supported, continuous, and cantilever members. It also discusses load assumptions, reinforcement cover requirements, deflection limits, and provides an overview of one-way slabs, two-way slabs, flat slabs, and flat plates.
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Various design philosophies have been invented in the different parts of the world to design RCC structures. In 1900 theory by Coignet and Tedesco was accepted and codified as Working Stress Method. The Working Stress Method was in use for several years until the revision of IS 456 in 2000.
What are the Various Design Philosophies?
Working Stress Method
limit state method
ultimate load method
#civil insider
Footings are structural members that support columns and walls and transmit their loads to the soil. Different types of footings include wall footings, isolated/single footings, combined footings, cantilever/strap footings, continuous footings, rafted/mat foundations, and pile caps. Footings must be designed to safely carry and transmit loads to the soil while meeting code requirements regarding bearing capacity, settlement, reinforcement, and shear strength. A proper footing design involves determining loads, allowable soil pressure, reinforcement requirements, and assessing settlement.
This document discusses the design of flat slab structures. It begins by defining a flat slab as a type of slab supported directly on columns without beams. It then provides details on the types of flat slabs, their common uses in buildings, and benefits such as flexibility in layout and reduced construction time. The document goes on to discuss key design considerations for flat slabs including thickness, drops, column heads, and methods of analysis. It focuses on the direct design method and provides limitations for its use.
This document summarizes the design of a reinforced concrete overhead water tank located in Kalyani, West Bengal, India to serve a population of 1500 people. Key aspects of the design include a diameter of 12 meters, total height of 5 meters, capacity of 540000 liters, and a raft foundation. Load calculations and analysis of the dome shape determine that the meridional and hoop stresses are within code limits for the minimum M30 grade concrete. Nominal tensile reinforcement of 6-8mm bars at 180mm centers in both directions is sufficient. Design codes and references used are cited.
Footings are structural members that support columns and walls and transmit their loads to the soil in a way that does not exceed the soil's load bearing capacity or cause excessive settlement or rotation. There are two main types of isolated column footings: pad footings and sloped footings. The design process for isolated footings includes determining the size, net upward pressure, bending moment, depth, reinforcement, and load transfer requirements. The example provides specifications to design an isolated square footing to support a 400mm x 400mm column with an axial load of 800kn using M-20 concrete and Fe-250 steel, accounting for a soil bearing capacity of 120kn/m2.
This document provides information on industrial buildings, including their components and factors to consider in design. Key points include:
- Industrial buildings are used for manufacturing and storage by industries and include steel plants, warehouses, and factories.
- Site selection considers access, raw materials, utilities, land characteristics, and transportation.
- Major components include the roof, trusses, purlins, girts, bracing, and foundations.
- Design considerations cover roofing/wall materials, bay widths, structural framing, truss configurations, and bracing to resist lateral loads.
Circular slabs are commonly used as roofs or floors with a circular plan, such as water tanks. They experience bending stresses in two perpendicular directions - radially and circumferentially. Reinforcement is provided as a mesh of bars with equal cross-sectional area in both directions. Near the edges, additional radial and circumferential reinforcement may be needed if edge stresses are significant. Circular slabs are analyzed based on elastic theory, and deflect into a saucer shape under uniform loads, developing tensile and compressive stresses on the convex and concave surfaces respectively. Reinforcement must be provided in both radial and circumferential directions near the convex surface.
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.
This document provides design requirements for lacing and battening systems used in steel structural elements. It discusses two types of lacing systems - single and double. It outlines 9 design requirements for lacing per Indian code IS 800, including angle of inclination, slenderness ratio, effective length, width/thickness, transverse shear force, strength checks, and end connections. It also discusses 7 design requirements for battening systems, including transverse shear force calculation, slenderness ratio, spacing, thickness, effective depth, overlap for welded connections, and notes battening offers less shear resistance than lacing.
This document provides instruction on analyzing three-hinged arches. It defines a three-hinged arch as a statically determinate structure with three hinges: two at the supports and one at the crown. The document describes how to determine the reactions of a three-hinged arch under a concentrated load using equations of static equilibrium. It presents an example problem showing how bending moment is reduced in a three-hinged arch compared to a simply supported beam carrying the same load.
This document discusses the design of two-way slabs. It defines a two-way slab as having a ratio of long to short spans of less than 2. The main types of two-way slabs described are flat slabs with drop panels, two-way slabs with beams, flat plates, and waffle slabs. The basic steps of two-way slab design are outlined, including choosing the slab type and thickness, the design method, calculating moments, determining reinforcement, and checking shear strength. Two common design methods are described: the direct design method which uses coefficients, and the equivalent frame method which analyzes frames cut between columns.
This document discusses different types of columns used in construction. It defines a column as a structural member subjected to compressive axial loads. Columns are classified as long, short, or intermediate based on their length-to-minimum radius of gyration ratio. Long columns have a ratio greater than 50, short columns less than 15-50, and intermediate between 30-100. The document provides examples of column types and discusses effective length, radius of gyration, buckling load, and Euler's formula for calculating crippling load.
The document provides information about caissons, which are watertight structures used in construction projects involving excavation below water levels. It discusses different types of caissons including box caissons, open or well caissons, pneumatic caissons, and multiple well or monolith caissons. Methods of constructing and sinking each type are described. Advantages and uses of caissons are outlined. Health risks associated with working under compressed air in pneumatic caissons, known as caisson sickness, are also summarized.
The document provides details on the design procedure for beams. It discusses estimating loads, analyzing beams to determine shear forces and bending moments, and designing beams. The design process involves selecting the beam size and shape, calculating the effective span, determining critical moments and shears, selecting reinforcement, and checking requirements such as shear capacity, deflection limits, and development lengths. An example problem demonstrates designing a singly reinforced concrete beam with a span of 5 meters to support a working live load of 25 kN/m.
This document discusses the design of compression members under uniaxial bending. It notes that columns are rarely under pure axial compression due to eccentricities from rigid frame action or accidental loading. Columns can experience uniaxial or biaxial bending based on the loading. The behavior depends on the relative magnitudes of the bending moment and axial load, which determine the position of the neutral axis. Methods for designing eccentrically loaded short columns include using equations that calculate the neutral axis position and failure mode, or using interaction diagrams that graphically show the safe ranges of moment and axial load.
The document discusses the reinforcement requirements and design process for axially loaded columns. It provides guidelines on the minimum longitudinal and transverse reinforcement, including the pitch and diameter of lateral ties. Examples are given to calculate the ultimate load capacity of rectangular and circular columns based on the grade of concrete and steel. Design assumptions and checks for minimum eccentricity are also outlined.
The document discusses various types of compression members including columns, pedestals, walls, and struts. It describes design considerations for compression members including strength and buckling resistance. It defines effective length as the vertical distance between points of inflection when the member buckles. Various classifications of columns are discussed based on loadings, slenderness ratio, and reinforcement type. Code requirements for longitudinal and transverse reinforcement as well as detailing are provided. Two examples of column design are included, one with axial load only and one with spiral reinforcement.
The document discusses buckling of columns under axial compression. It describes:
1) Different buckling theories including elastic buckling, inelastic buckling using tangent modulus theory and reduced modulus theory. Shanley's theory accounts for the effect of transverse displacement.
2) Factors affecting buckling strength including end conditions, initial crookedness, and residual stresses. Effective length accounts for end restraint.
3) Local buckling of thin plate elements can reduce the column's strength before its calculated buckling strength is reached. Flange and web buckling must be prevented.
Design for Short Axially Loaded Columns ACI318Abdullah Khair
This document discusses the design of columns. It begins by defining columns and classifying them as short or long based on their slenderness ratio. Columns can be reinforced with ties or a spiral. Equations are provided for calculating the nominal axial capacity of columns based on the concrete compressive strength and steel reinforcement area. Minimum requirements are specified for reinforcement ratios, number of bars, concrete cover, and lateral tie or spiral spacing. Spirally reinforced columns can develop higher strength due to concrete confinement by the spiral. Design of the spiral pitch is discussed based on providing equivalent confining pressure.
rectangular and section analysis in bending and shearqueripan
The document discusses the design of reinforced concrete beams for bending and shear. It covers the analysis of singly and doubly reinforced rectangular beam sections. Key points covered include the concept of neutral axis, under-reinforced and over-reinforced sections, design of bending reinforcement, design of shear reinforcement including link spacing, and deflection criteria. Worked examples are provided to demonstrate the design of bending and shear reinforcement for rectangular beams.
The document discusses the design of reinforced concrete columns. It provides formulas to calculate the nominal capacity of concentrically loaded columns based on steel ratio and material strengths. Minimum and maximum steel ratios of 1-8% are recommended, with a reasonable range of 1-3%. Clear cover requirements of 40-75mm are outlined depending on soil contact. Tie design considerations include bar diameter, shape, and longitudinal spacing. Spiral reinforcement provides increased ductility and the document discusses formulas for calculating confined concrete strength based on spiral ratio and properties. Minimum spiral ratios and pitch requirements are also provided.
This document provides instruction on designing short axially loaded compression members according to Indian code IS 456. It discusses the assumptions made for concrete and steel strengths, and derives the governing equations for tied columns with rectangular/square cross-sections and spiral columns with circular cross-sections. Numerical examples are presented to demonstrate designing columns using direct computation from the equations and using design charts from SP-16.
This document provides a summary of reinforced concrete columns (RCC columns). It defines a column and describes different types of columns based on reinforcement and length. Short columns are less than 12 times the minimum thickness, while long columns are greater than 12 times the thickness. The document outlines preliminary sizing of columns and the functions of tie/spiral reinforcement. It includes design equations for axially loaded columns in working stress design (WSD) and ultimate stress design (USD). Two sample problems are worked through demonstrating column design using both methods.
This document discusses reinforced concrete columns. It defines different types of columns including tied, spiral, composite, and steel pipe columns. It describes the behavior and analysis of axially loaded columns, including elastic behavior, creep effects, and nominal capacity. Design provisions from the ACI code are presented for reinforcement requirements of tied and spiral columns. The behavior of columns under combined bending and axial loads is discussed, including interaction diagrams. Examples are provided to demonstrate the design of columns for various load cases.
Design of Beam- RCC Singly Reinforced BeamSHAZEBALIKHAN1
Concrete beams are an essential part of civil structures. Learn the design basis, calculations for sizing, tension reinforcement, and shear reinforcement for a concrete beam.
This document provides a summary of the design and verification of anchor bolts and a shear lug for a column base connection. It includes the geometry, loads, materials, and design calculations for the base plate, anchor bolts, and shear lug plate. The calculations show the base plate and anchor bolts satisfy strength requirements for bearing, tension, and shear. The shear lug plate is designed to resist the portion of shear load not resisted by friction, and calculations verify it satisfies strength requirements for bearing and shear.
Because of torsion, the beam fails in diagonal tension forming the spiral cracks around the beam. Warping of the section does not allow a plane section to remain as plane after twisting. Clause 41 of IS 456:2000 provides the provisions for
the design of torsional reinforcements. The design rules for torsion are based on the equivalent moment.
The document discusses key topics in reinforced concrete design including:
- Concrete properties like compressive strength and stress-strain behavior.
- Tensile strength of concrete and how steel reinforcement is used where tensile stresses occur.
- Types of steel reinforcement like deformed bars, welded wire fabric, and prestressing strands.
- Design of short reinforced concrete columns where the equilibrium of forces in the steel and concrete is considered.
- Parameters that influence column design like reinforcement ratio, concrete strength, and safety factors.
- Requirements for transverse reinforcement to resist buckling.
- The need for concrete cover to protect the steel.
- An example of designing a short concrete column for a given load.
The document discusses different types of columns based on bracing, length, and reinforcement. It describes braced and unbraced columns, long and short columns, and tied, spiral, and composite columns. Requirements for minimum reinforcement, lateral ties, and selection of column size are also summarized.
Struktur Rabgka Bangunan Bangunan Baja _13776666.pptGidion Turuallo
This document provides an overview of the design of columns including:
1. It describes different types of columns and their reinforcement including tied and spiral columns.
2. It discusses the behavior and strength of short columns and how an elastic analysis is not suitable due to creep and shrinkage of concrete over time.
3. It outlines the nominal capacity, reinforcement requirements, and design procedure for columns under concentric axial loads including load combinations, strength requirements, and expressions to calculate the required reinforcement.
This document discusses different types and classifications of columns. It defines a column as a vertical structural member primarily designed to carry axial compression loads. Columns can be classified based on their shape, reinforcement, and type of loading. Common shapes include square, rectangular, circular, L-shaped, and T-shaped sections. Reinforcement types include tied columns with tie bars, spiral columns with helical reinforcement, and composite columns with encased steel. Columns are either concentrically loaded with forces through the centroid, or eccentrically loaded off-center. The document also covers column capacity calculations, resistance factors, and provides an example problem.
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2. Helical Reinforcement
• The main longitudinal reinforcement bars are
enclosed within closely spaced and
continuously wound spiral reinforcement.
Circular and octagonal columns are mostly of
this type
• Helical reinforcement is also termed as spiral
reinforcement which is used only in the
circular column. In case of circular column,
number of minimum reinforcement should not
be less than 6 bars. The diameter of the
reinforcement should not be less than 12 mm
and maximum distance between the
longitudinal bars should not be greater than
300 mm. Spiral reinforcement is shown in the
below figure
3. Advantages of Helical Reinforcement
• Several important structures collapsed due to
stirrups opening when subjected to important
seismic actions. This risk is minimized in the case of
using spiral stirrups, since it consists of only one
wire as transversal reinforcement, throughout the
entire length of the element.
• The circular section concrete columns (or drilled
piles) with spiral transversal reinforcement are
easier to produce, require a shorter time to
assemble, and when subjected to lateral loads the
failure by stirrup opening is not an option. These
advantages could be obtained for usual rectangular
section by using the rectangular spiral
reinforcement.
4. • The use of links for column design is very popular.
However, engineers tend to use helical
reinforcement instead of normal links because helical
reinforcement has the potential advantage of
protecting columns/piles against seismic loads.
• Moreover, when the columns reach the failure state,
the concrete outside hoops cracks and falls off firstly,
followed by the eventual failure of the whole columns.
The peeling off of concrete outside helical
reinforcement provides a warning signal before the
sudden failure of columns. In addition, it can take up a
higher working load than normal link reinforcement.
• For instance, helical reinforcement is adopted in the
design of marine piles in Government piers.
Why is Helical Reinforcement sometimes designed instead of normal links ?
7. Assumptions:
(i) Plane sections normal to the axis remain plane after bending.
(ii) The maximum strain in concrete at the outer most compression fibre is taken
as 0.0035 in bending.
(iii) The acceptable stress-strain curve of concrete is assumed to be parabolic.
(iv) The tensile strength of concrete is ignored.
(v) The design stresses of the reinforcement are derived from the representative
stress-strain curves from Figs. 23A and B of IS 456:2000, for the type of steel used
using the partial safety factor γm as 1.15.
(vi) The maximum compressive strain in concrete in axial compression is taken as
0.002.
(vii) The maximum compressive strain at the highly compressed extreme fibre in
concrete subjected to axial compression and bending and when there is no
tension on the section shall be 0.0035 minus 0.75 times the strain at the least
compressed extreme fibre.
8. Slenderness Limits:
The code (Clause 25.3.1) specifies that the ratio of the
unsupported length (l) to the least lateral dimension (d) of a
column should not exceed a value of 60:
𝑙
𝑑
≤ 60
Furthermore, in case one end of a column is free in any given
plane, the code specifies (Clause 25.3.1) specifies that
𝑙 ≤
100𝑏2
𝐷
Where, D- depth of X-section measured in the plane of the
cantilever.
b- width (in perpendicular direction)
9. Minimum Eccentricity:
In practical construction, columns are rarely truly concentric.
Even a theoretical column loaded axially will have accidental
eccentricity due to inaccuracy in construction or variation of
materials etc.
Accordingly, all axially loaded columns should be designed
considering the minimum eccentricity as stipulated in cl. 25.4 of
IS 456 as given below –
ex min ≥ greater of: {l/500 + D/30) or 20 mm }
ey min ≥ greater of: {(l/500 + b/30) or 20 mm }
where l-the unsupported length,
D- larger lateral dimension
b-least lateral dimension
10. (a) Pitch:
Helical reinforcement shall be of regular formation with the turns of
the helix spaced evenly and its ends shall be anchored properly by
providing one and a half extra turns of the spiral bar. The pitch of
helical reinforcement shall be determined as-
• The maximum pitch of transverse reinforcement shall be the least
of the following:
(i) the least lateral dimension of the compression members;
(ii) sixteen times the smallest diameter of the longitudinal
reinforcement bar to be tied; and
(iii) 300 mm.
• The above criteria is valid for all cases except where an increased
load on the column is allowed for on the strength of the helical
reinforcement.
11. In such cases only,
• the maximum pitch shall be the lesser of -
(i) 75 mm and
(ii) one-sixth of the core diameter of the column,
• and the minimum pitch shall be the lesser of
(i) 25 mm and
(ii) three times the diameter of the steel bar forming the helix.
(b) Diameter:
The diameter of the polygonal links or lateral ties shall be not less than-
• one-fourth of the diameter of the largest longitudinal bar,
• and in no case less than 6 mm.
13. •Columns with helical reinforcement take more load than
that of tied columns due to additional strength of spirals
in contributing to the strength of columns.
•Accordingly, cl. 39.4 recommends a multiplying factor of
1.05 regarding the strength of such columns.
•The code further recommends that the ratio of volume of
helical reinforcement to the volume of core shall not be
less than 0.36 (Ag/Ac – 1) (fck/fy), in order to apply the
additional strength factor of 1.05 (cl. 39.4.1).
14. Accordingly, the governing equation of the spiral columns may
be written as-
Pu = 1.05(0.4 fck Ac + 0.67 fy Asc)
where, Pu = factored axial load on the member,
fck = characteristic compressive strength of the concrete,
Ac = area of concrete,
fy= characteristic strength of the compression reinforcement, and
Asc = area of longitudinal reinforcement for columns
The above equation, given in cl. 39.3 of IS 456, has two unknowns Ac and Asc to
be determined from one equation. The equation is recast in terms of Ag, the
gross area of concrete and p, the percentage of compression reinforcement
employing-
Asc = pAg/100 ...(10.5) Ac = Ag(1 – p/100) ...(10.6)
15. Earlier observations of several investigators reveal that the effect
of containing holds good in the elastic stage only and it gets lost
when spirals reach the yield point. Again, spirals become fully
effective after spalling off the concrete cover over the spirals due
to excessive deformation. Accordingly, the two points should be
considered in the design of such columns.
(i) the enhanced load carrying capacity taken into account by the
multiplying factor of 1.05.
(ii) maintaining specified ratio of volume of helical reinforcement
to the volume of core, as specified in cl.39.4.1 and mentioned
earlier.
16. The second point, in fact, determines the pitch p of the helical
reinforcement-
Volume of helical reinforcement in one loop = 𝝅 𝑫 𝒄 − 𝝓 𝒔 𝒑 𝒂 𝒔𝒑 …(10.9)
Volume of core =
𝝅
𝟒
𝑫 𝒄
𝟐
𝒑 … (10.10)
where Dc = diameter of the core (Fig.10.21.2b)
φsp = diameter of the spiral reinforcement (Fig.10.21.2b)
asp = area of cross-section of spiral reinforcement
p = pitch of spiral reinforcement (Fig.10.21.2b)
To satisfy the condition of cl.39.4.1 of IS 456, we have –
π Dc−ϕsp
asp
𝜋
4
𝐷 𝑐
2 𝑝
≥ 0.36(
Ag
Ac
− 1)(
fck
fy
)
17. which finally gives-
𝒑 ≤
𝟏𝟏.𝟏 𝐃 𝐜
−𝝓 𝒔 𝒑
𝒂 𝐬𝐩 𝒇 𝒚
𝑫 𝟐
−𝑫 𝒄
𝟐 𝒇 𝒄𝒌
… (10.11)
•Thus, Eqs.10.8 and 11 are the governing equations to
determine the diameter of column, pitch of spiral and
area of longitudinal reinforcement.
• It is worth mentioning that the pitch p of the spiral
reinforcement, if determined from Eq.10.11,
automatically satisfies the stipulation of cl.39.4.1 of IS
456. However, the pitch and diameter of the spiral
reinforcement should also satisfy cl. 26.5.3.2 of IS
456:2000.
18. Numerical
•Design a circular column of 400 mm diameter
with helical reinforcement subjected to an axial
load of 1500 kN under service load and live load.
The column has an unsupported length of 3 m
effectively held in position at both ends but not
restrained against rotation. Use M 25 concrete
and Fe 415 steel.
19. Soln.
Step 1: To check the slenderness ratio
•Given data are-
Unsupported length l = 3000 mm,
D = 400 mm.
Table 28 of Annex E of IS 456 gives effective length
le = l = 3000 mm.
Therefore, le/D = 7.5 < 12 confirms that it is a short
column.
20. Step 2: Minimum eccentricity
emin = Greater of (l/500 + D/30) or 20 mm = 20 mm
0.05 D = 0.05(400) = 20 mm
As per cl.39.3 of IS 456, emin should not exceed 0.05D to employ the
equation given in that clause for the design. Here, both the
eccentricities are the same. So, we can use the equation given in
that clause of IS 456 i.e., Eq.10.8 for the design.
21. Step 3: Area of steel
From Eq.10.8, we have
Pu = 1.05(0.4 fck Ac + 0.67 fy Asc) … (10.8)
Ac = Ag – Asc = 125714.29 – Asc
Substituting the values of Pu, fck, Ag and fy in Eq.10.8,
1.5(1500)(103) = 1.05{0.4(25)(125714.29 – Asc) + 0.67(415) Asc}
we get the value of Asc = 3304.29 mm2.
Provide 11 nos. of 20 mm diameter bars (= 3455 mm2) as longitudinal
reinforcement giving p = 2.75%.
This p is between 0.8 (min.) and 4 (max.) %. Hence o.k.
22. Step 4: Lateral ties
It has been mentioned in sec.10.22.4 that the pitch p of the helix determined
from Eq.10.11 automatically takes care of the cl.39.4.1 of IS 456.
Therefore, the pitch is calculated from Eq.10.11 selecting the diameter of helical
reinforcement from cl.26.5.3.2 d-2 of IS 456. However, automatic satisfaction of
cl.39.4.1 of IS 456 is also checked here for confirmation.
Diameter of helical reinforcement (cl.26.5.3.2 d-2) shall be not less than greater
of- (i) one-fourth of the diameter of largest longitudinal bar, and
(ii) 6 mm.
Therefore, with 20 mm diameter bars as longitudinal reinforcement, the
diameter of helical reinforcement = 6 mm.
23. From Eq.10.11, we have
Pitch of helix p ≤ 11.1(Dc - φsp ) asp fy/(D2 – 𝑫 𝒄
𝟐)fck
Where, Dc = 400 – 40 – 40 = 320 mm,
φ 𝑠𝑝 = 6mm, asp = 28 mm2 ,
fy = 415 N/mm2 , D = 400 mm,
fck = 25 N/mm2 .
So, p ≤ 11.1(320 – 6) (28) (415)/(4002 – 3202 ) (25) ≤ 28.125 mm
As per cl.26.5.3.2 d-1, the maximum pitch is the lesser of 75 mm and 320/6
= 53.34 mm and the minimum pitch is lesser of 25 mm and 3(6) = 18 mm.
We adopt pitch = 25 mm which is within the range of 18 mm and 53.34 mm.
So, provide 6 mm bars @ 25 mm pitch forming the helix.
24. Checking of cl. 39.4.1 of IS 456
The values of helical reinforcement and core in one loop are obtained
from Eqs.10.8 and 9, respectively. Substituting the values of Dc, φsp , asp
and pitch p in the above two equations, we have
Volume of helical reinforcement in one loop = 27632 mm3 and
Volume of core in one loop = 2011428.571 mm3 .
Their ratio = 27632/2011428.571 = 0.0137375
0.36(Ag/Ac – 1) (fck/fy) = 0.012198795
It is, thus, seen that the above ratio (0.0137375) is not less than
0.36(Ag/Ac – 1) (fck/fy).
25. Hence, the circular column of diameter 400 mm has eleven longitudinal
bars of 20 mm diameter and 6 mm diameter helix with pitch p = 25
mm. The reinforcing bars are shown in above Fig.
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