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 provides an overview of the design of steel beams. It discusses various beam types and sections, loads on beams, design considerations for restrained and unrestrained beams. For restrained beams, it covers lateral restraint requirements, section classification, shear capacity, moment capacity under low and high shear, web bearing, buckling, and deflection checks. For unrestrained beams, it discusses lateral torsional buckling, moment and buckling resistance checks. Design procedures and equations for determining effective properties and capacities are also presented.
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.
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.
This document provides an overview of different seismic analysis methods for reinforced concrete buildings according to Indian code IS 1893-2002, including linear static, nonlinear static, linear dynamic, and nonlinear dynamic analysis. It describes the basic procedures for each analysis type and provides examples of how to calculate design seismic base shear, distribute seismic forces vertically and horizontally, and determine drift and overturning effects. Case studies are presented comparing the results of static and dynamic analysis for regular and irregular multi-storey buildings modeled in SAP2000.
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.
This document discusses the design of beams. It defines different types of beams like floor beams, girders, lintels, purlins, and rafters. It describes how beams are classified based on their support conditions as simply supported, cantilever, fixed, or continuous beams. Commonly used beam sections include universal beams, compound beams, and composite beams. The document also covers plastic analysis of beams, classification of beam sections, and failure modes of beams.
The document provides details on the design of a reinforced concrete column footing to support a column with a load of 1100kN. It includes calculating the footing size as a 3.5m x 3.5m square to support the load, determining the reinforcement with 12mm diameter bars at 100mm spacing, and checking that the design meets requirements for bending capacity, shear strength, and development length. The step-by-step worked example shows how to analyze and detail the reinforcement of the column footing.
This document provides details on the design and construction of flat slab structures. It discusses the benefits of flat slabs such as flexibility in layout, reduced building height and faster construction. Key considerations for design include wall and column placement, structural layout optimization, deflection checks, crack control and punching shear. Analysis involves dividing the slab into strips and determining moment and shear distributions. Reinforcement is arranged in two directions and detailing includes reinforcement lapping and service penetrations.
This document provides an overview of the design of steel beams. It discusses various beam types and sections, loads on beams, design considerations for restrained and unrestrained beams. For restrained beams, it covers lateral restraint requirements, section classification, shear capacity, moment capacity under low and high shear, web bearing, buckling, and deflection checks. For unrestrained beams, it discusses lateral torsional buckling, moment and buckling resistance checks. Design procedures and equations for determining effective properties and capacities are also presented.
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.
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.
This document provides an overview of different seismic analysis methods for reinforced concrete buildings according to Indian code IS 1893-2002, including linear static, nonlinear static, linear dynamic, and nonlinear dynamic analysis. It describes the basic procedures for each analysis type and provides examples of how to calculate design seismic base shear, distribute seismic forces vertically and horizontally, and determine drift and overturning effects. Case studies are presented comparing the results of static and dynamic analysis for regular and irregular multi-storey buildings modeled in SAP2000.
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.
This document discusses the design of beams. It defines different types of beams like floor beams, girders, lintels, purlins, and rafters. It describes how beams are classified based on their support conditions as simply supported, cantilever, fixed, or continuous beams. Commonly used beam sections include universal beams, compound beams, and composite beams. The document also covers plastic analysis of beams, classification of beam sections, and failure modes of beams.
The document provides details on the design of a reinforced concrete column footing to support a column with a load of 1100kN. It includes calculating the footing size as a 3.5m x 3.5m square to support the load, determining the reinforcement with 12mm diameter bars at 100mm spacing, and checking that the design meets requirements for bending capacity, shear strength, and development length. The step-by-step worked example shows how to analyze and detail the reinforcement of the column footing.
This document provides details on the design and construction of flat slab structures. It discusses the benefits of flat slabs such as flexibility in layout, reduced building height and faster construction. Key considerations for design include wall and column placement, structural layout optimization, deflection checks, crack control and punching shear. Analysis involves dividing the slab into strips and determining moment and shear distributions. Reinforcement is arranged in two directions and detailing includes reinforcement lapping and service penetrations.
This document discusses bolted connections used in structural engineering. It begins by explaining why connection failures should be avoided, as they can lead to catastrophic structural failures. It then classifies bolted connections based on their method of fastening, rigidity, joint resistance, fabrication location, joint location, connection geometry, and type of force transferred. It describes different types of bolts and bolt tightening techniques used for friction grip connections. It discusses advantages and drawbacks of bolted connections compared to riveted or welded connections. The document provides detailed information on design and behavior of various bolted connections.
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.
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.
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.
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.
DESIGN AND ANALYSIS OF G+3 RESIDENTIAL BUILDING BY S.MAHAMMAD FROM RAJIV GAND...Mahammad2251
Structural design is the primary aspect of civil engineering. The foremost basic in
structural engineering is the design of simple basic components and members of a building viz., Slabs,
Beams, Columns and Footings. In order to design them, it is important to first obtain the plan of the
particular building. Thereby depending on the suitability; plan layout of beams and the position of
columns are fixed.
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 provides information about pile foundations, including:
- Piles transfer structural loads through weak soil layers into stronger soils and rocks below.
- Common types of piles include pre-cast concrete, cast-in-situ concrete (e.g. Raymond, MacArthur), steel, timber, and composite piles.
- Piles are selected based on factors like soil properties, loading conditions, costs, and availability of materials. Proper pile type and design are necessary to safely support structures.
The document discusses retaining walls and includes:
- Definitions of retaining walls and their parts
- Common types of retaining walls including gravity, semi-gravity, cantilever, counterfort and bulkhead walls
- Earth pressures like active, passive and at rest pressures
- Design principles for stability against sliding, overturning and bearing capacity
- Drainage considerations for retaining walls
- Theories for analyzing earth pressures like Rankine and Coulomb's theories
- Sample design calculations and problems for checking stability of retaining walls
Composite construction or Composite Structure/FrameAbdul Rahman
Composite structure of steel and concrete has been explained under this ppt with examples, type of structural members, advantages and comparison with other structures like R.C.C structure and Steel structures.
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 provides details on the design of staircases, including:
1. It describes the typical components of a staircase like flights, landings, risers, treads, nosings, waist slabs, and soffits.
2. It discusses different types of staircases like straight, quarter turn, dog-legged, open well, spiral and helicoidal.
3. It classifies staircases structurally into those with stair slabs spanning transversely or longitudinally and provides examples of each type.
4. It provides an example calculation for the design of a waist slab spanning longitudinally, including loading, bending moment calculation, reinforcement design and checks.
Compression members are structural members subjected to axial compression or compressive forces. Their design is governed by strength and buckling capacity. Columns can fail due to local buckling, squashing, overall flexural buckling, or torsional buckling. Built-up columns use components like lacings, battens, and cover plates to help distribute stress more evenly and increase buckling resistance compared to a single member. Buckling occurs when a straight compression member becomes unstable and bends under a critical load.
This document discusses structural analysis methods for statically indeterminate structures. It defines key terms like degree of static indeterminacy, internal and external redundancy, and methods for analyzing indeterminate structures. Specific methods discussed include the flexibility matrix method, consistent deformation method, and unit load method. Examples of statically indeterminate beams and frames are also provided.
Tension members are structural elements subjected to direct tensile loads. Their strength depends on factors like length of connection, size and spacing of fasteners, cross-sectional area, fabrication type, connection eccentricity, and shear lag. Failure can occur through gross section yielding, net section rupture, or block shear. Design involves selecting a member with sufficient gross area to resist factored loads in yielding, then checking strength considering net section rupture and block shear failure modes.
This document discusses shear wall analysis and design. It defines shear walls as structural elements used in buildings to resist lateral forces through cantilever action. The document classifies different types of shear walls and discusses their behavior under seismic loading. It outlines the steps for designing shear walls, including reviewing layout, analyzing structural systems, determining design forces, and detailing reinforcement. The document emphasizes the importance of properly locating shear walls in a building to resist seismic loads and minimize torsional effects.
This document discusses the design of two-way floor slab systems. It compares the behavior of one-way and two-way slabs, describing how two-way slabs carry load in two directions versus one direction for one-way slabs. Different two-way slab systems like flat plates, waffle slabs, and ribbed slabs are described. Methods for analyzing two-way slabs include direct design, equivalent frame, elastic, plastic, and nonlinear analysis. Design considerations like minimum slab thickness are discussed along with examples calculating thickness.
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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1) Two-way slabs are slabs that require reinforcement in two directions because bending occurs in both the longitudinal and transverse directions when the ratio of longest span to shortest span is less than 2.
2) The document discusses various types of two-way slabs and design methods, focusing on the direct design method (DDM).
3) Using the DDM, the total factored load is first calculated, then the total factored moment is distributed to positive and negative moments. The moments are further distributed to column and middle strips using factors that consider the slab and beam properties.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help boost feelings of calmness, happiness and focus.
- The document describes the design and detailing of flat slabs, which are concrete slabs supported directly by columns without beams.
- Key aspects covered include dimensional considerations, analysis methods, design for bending moments including division of panels and limiting negative moments, shear design and punching shear, deflection and crack control, and design procedures.
- An example problem is provided to illustrate the full design process for an internal panel with drops adjacent to edge panels.
This document discusses bolted connections used in structural engineering. It begins by explaining why connection failures should be avoided, as they can lead to catastrophic structural failures. It then classifies bolted connections based on their method of fastening, rigidity, joint resistance, fabrication location, joint location, connection geometry, and type of force transferred. It describes different types of bolts and bolt tightening techniques used for friction grip connections. It discusses advantages and drawbacks of bolted connections compared to riveted or welded connections. The document provides detailed information on design and behavior of various bolted connections.
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.
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.
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.
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.
DESIGN AND ANALYSIS OF G+3 RESIDENTIAL BUILDING BY S.MAHAMMAD FROM RAJIV GAND...Mahammad2251
Structural design is the primary aspect of civil engineering. The foremost basic in
structural engineering is the design of simple basic components and members of a building viz., Slabs,
Beams, Columns and Footings. In order to design them, it is important to first obtain the plan of the
particular building. Thereby depending on the suitability; plan layout of beams and the position of
columns are fixed.
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 provides information about pile foundations, including:
- Piles transfer structural loads through weak soil layers into stronger soils and rocks below.
- Common types of piles include pre-cast concrete, cast-in-situ concrete (e.g. Raymond, MacArthur), steel, timber, and composite piles.
- Piles are selected based on factors like soil properties, loading conditions, costs, and availability of materials. Proper pile type and design are necessary to safely support structures.
The document discusses retaining walls and includes:
- Definitions of retaining walls and their parts
- Common types of retaining walls including gravity, semi-gravity, cantilever, counterfort and bulkhead walls
- Earth pressures like active, passive and at rest pressures
- Design principles for stability against sliding, overturning and bearing capacity
- Drainage considerations for retaining walls
- Theories for analyzing earth pressures like Rankine and Coulomb's theories
- Sample design calculations and problems for checking stability of retaining walls
Composite construction or Composite Structure/FrameAbdul Rahman
Composite structure of steel and concrete has been explained under this ppt with examples, type of structural members, advantages and comparison with other structures like R.C.C structure and Steel structures.
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 provides details on the design of staircases, including:
1. It describes the typical components of a staircase like flights, landings, risers, treads, nosings, waist slabs, and soffits.
2. It discusses different types of staircases like straight, quarter turn, dog-legged, open well, spiral and helicoidal.
3. It classifies staircases structurally into those with stair slabs spanning transversely or longitudinally and provides examples of each type.
4. It provides an example calculation for the design of a waist slab spanning longitudinally, including loading, bending moment calculation, reinforcement design and checks.
Compression members are structural members subjected to axial compression or compressive forces. Their design is governed by strength and buckling capacity. Columns can fail due to local buckling, squashing, overall flexural buckling, or torsional buckling. Built-up columns use components like lacings, battens, and cover plates to help distribute stress more evenly and increase buckling resistance compared to a single member. Buckling occurs when a straight compression member becomes unstable and bends under a critical load.
This document discusses structural analysis methods for statically indeterminate structures. It defines key terms like degree of static indeterminacy, internal and external redundancy, and methods for analyzing indeterminate structures. Specific methods discussed include the flexibility matrix method, consistent deformation method, and unit load method. Examples of statically indeterminate beams and frames are also provided.
Tension members are structural elements subjected to direct tensile loads. Their strength depends on factors like length of connection, size and spacing of fasteners, cross-sectional area, fabrication type, connection eccentricity, and shear lag. Failure can occur through gross section yielding, net section rupture, or block shear. Design involves selecting a member with sufficient gross area to resist factored loads in yielding, then checking strength considering net section rupture and block shear failure modes.
This document discusses shear wall analysis and design. It defines shear walls as structural elements used in buildings to resist lateral forces through cantilever action. The document classifies different types of shear walls and discusses their behavior under seismic loading. It outlines the steps for designing shear walls, including reviewing layout, analyzing structural systems, determining design forces, and detailing reinforcement. The document emphasizes the importance of properly locating shear walls in a building to resist seismic loads and minimize torsional effects.
This document discusses the design of two-way floor slab systems. It compares the behavior of one-way and two-way slabs, describing how two-way slabs carry load in two directions versus one direction for one-way slabs. Different two-way slab systems like flat plates, waffle slabs, and ribbed slabs are described. Methods for analyzing two-way slabs include direct design, equivalent frame, elastic, plastic, and nonlinear analysis. Design considerations like minimum slab thickness are discussed along with examples calculating thickness.
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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construction joint vs expansion joint construction joint vs control joint sidewalk control joint spacing concrete wall control joints expansion joint concrete construction joint concrete concrete joints control joint
monolithic isolation joints isolation joint material isolation joint vs expansion joint isolation joint neo prene insulating joints pipeline isolation joint vs control joint isolation joints in concrete concrete slab isolation joint
construction joint vs expansion joint construction joint vs control joints idewalk control joint spacing concrete wall control joints expansion joint concrete construction joint concrete concrete joints control joint
concrete joint filler
concrete joint filler strips
control joint vs construction joint concrete
concrete control joint filler
concrete slab control joint detail
types of concrete expansion joints
construction joint concrete
control joints in concrete
1) Two-way slabs are slabs that require reinforcement in two directions because bending occurs in both the longitudinal and transverse directions when the ratio of longest span to shortest span is less than 2.
2) The document discusses various types of two-way slabs and design methods, focusing on the direct design method (DDM).
3) Using the DDM, the total factored load is first calculated, then the total factored moment is distributed to positive and negative moments. The moments are further distributed to column and middle strips using factors that consider the slab and beam properties.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help boost feelings of calmness, happiness and focus.
- The document describes the design and detailing of flat slabs, which are concrete slabs supported directly by columns without beams.
- Key aspects covered include dimensional considerations, analysis methods, design for bending moments including division of panels and limiting negative moments, shear design and punching shear, deflection and crack control, and design procedures.
- An example problem is provided to illustrate the full design process for an internal panel with drops adjacent to edge panels.
This resource material is exclusively for the purpose of knowledge dissemination for the use of Civil engineering Fraternity, professionals & students.
This file contains state of art techniques adopted & practiced as per IS456 code provisions for analysis design & detailing of flat slab structural systems.
The presentation aims to provide clear,concise, technical details of flat slabs design.
The presentation deals with structural actions & behavior of flat slabs with visual representations obtained through finite element analysis.
The knowledge gained can be used for designing building structures frequently encountered in construction.
The presentation covers an important feature of slab systems supported on rigid & flexible support & clearly demarcates the minimum beam dimensions required to consider the supports to be either rigid or flexible.
The presentation alsoincludes clear technical drawings to highlight the importance of detailing w.r.t. rebar lay out - positioning & curtailment. Typical section drawing through middle & column strips are also included for visualizing rebar patterns in 3 -d views.
This presentation is an outcome of series of lectures for undergrad & grad students studying in civil engineering.
My next presentation would be on Analysis & design of deep beams.
Kindly mail me ( vvietcivil@gmail.com) your questions & valuable feedback.
The document discusses flat grid or waffle slab systems. It defines waffle slabs as having two-directional reinforcement on the outside, giving it a waffle-like shape. This provides stability without using much material, making it suitable for large flat areas like foundations and floors. Waffle slabs are used in industrial and commercial buildings where large spans are needed with few columns. They provide features like using less concrete and steel than traditional slabs while providing strength and resistance to cracking and sagging. The document outlines the production, design, and construction process for waffle slabs and notes some iconic landmarks that have utilized this system.
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 provides a tutorial for punching shear reinforcement using links attached to a slab's main reinforcement mesh. Punching shear reinforcement consists of additional steel placed around columns in a slab to prevent slab-column connection failures. The tutorial demonstrates punching shear reinforcement for two examples (ID01 and ID02) showing the process for laying out and drawing the reinforcement in plans and sections, including handling differences in column dimensions, slab thickness, and openings between the examples.
This document discusses different types of flat slab structures including those without and with drops and column heads. It outlines direct design and equivalent frame methods for analysis and highlights advantages like cost savings and disadvantages like minimum span requirements. The document also notes applications of flat slab structures.
The document provides details on the site location, physical features, site plan, zoning, and climate responsive design of an institutional housing project located on a sloping site in Pune. Key aspects include a compact planned layout with residential areas oriented north-south, interconnected open courtyards, extensive use of local and sustainable materials, rainwater harvesting, and solar energy systems.
Waffle slabs are reinforced concrete slabs reinforced in two orthogonal directions, forming a ribbed plate. They are characterized by their total edge height, lightening block height, rib spacing, rib thickness, and compression layer thickness. Waffle slabs can adequately support distributed and point loads in two directions. Benefits include flexibility, light weight allowing longer spans, fast construction, slim depths, robustness, vibration control, thermal mass, and durability. Waffle slabs are constructed with ribs forming a grid pattern and solid fills at supports. Larger spans may use post-tensioning or joist construction. Proper design considers loads, materials, deformations, and tile installation compatibility.
This document describes an experimental study comparing the structural behavior of monolithic and precast concrete portal frames. Scaled models of a monolithic frame and two precast frames (one with a corbel connection and one without) were tested under a two-point load. Test results showed that the monolithic frame had the highest deflections but lowest load capacity, while the precast frame with a corbel connection had the lowest deflections but highest load capacity. Cracks were first observed in the monolithic frame, followed by the precast frame without a corbel, with the frame with a corbel cracking at the highest loads. In conclusion, the monolithic frame was found to be the most ductile but least stiff, while
Flat slabs are reinforced concrete slabs that are supported directly by columns without beams. They provide minimum depth, fast construction, and flexible column placement. There are four main types: slabs without drops and with column heads, slabs with drops and without column heads, slabs with both drops and column heads, and typical flat slabs. Column heads increase shear strength while drops increase shear strength and negative moment capacity. Flat slab systems can be either one-way or two-way depending on span ratios and load distribution. Advantages include simple formwork, no beams, and minimum depth, while disadvantages include potential interference from drops.
Prestressed hollow core slabs are a type of precast concrete slab used for floors in multi-story buildings. They are made off-site and assembled quickly, providing benefits such as lower costs, reduced construction time, less raw material usage, and good structural and acoustic properties. Hollow core slabs are well-suited for modern housing needs due to their advantages over traditional floor constructions.
This document provides an introduction and manual for the design of hollow core slabs. It discusses the manufacturing of hollow core slabs and the materials used. It then covers advantages of hollow core slabs and common framing concepts. The bulk of the document focuses on guidelines for designing hollow core slabs, including flexural and shear design, camber and deflection, composite design, and strand development. It also covers special design considerations like load distribution, effects of openings, continuity, and cantilevers. Finally, it discusses using hollow core slabs as diaphragms to resist lateral loads. The manual is intended to provide design guidance and reference material for engineers and producers working with hollow core slab systems.
Architectural case study of IIM ahemdabad by louis i khanRajat Katarne
This document provides details about the Indian Institute of Management in Ahmedabad, India, which was completed in 1963. It was designed by famous architect Louis Kahn, with B.V. Doshi and Anant Raje. The campus includes academic buildings such as classrooms and faculty blocks arranged around a central plaza, as well as dormitories, a library, auditorium, and management development center spread across 66 acres. Brick is the primary building material. The layout separates academic and residential areas while integrating social activities between students and staff.
Coffered ceilings and slabs are rigid, planar structures that use a series of intersecting ribs to distribute loads across a space. The document discusses the history and architectural uses of coffered ceilings. It also describes different types of coffered slab structures like waffle slabs and drop slabs that are used for their load bearing capacities in long span structures like schools and hospitals. Various coffered slab construction techniques are outlined, including the use of precast elements and how services can be run through the coffered spaces.
This document discusses various practical applications of post-tensioned concrete in buildings. It describes different types of post-tensioned slabs such as flat slabs, slabs with drop panels, slabs with post-tensioned beams, waffle slabs, and lightened slabs. It also discusses post-tensioned foundation rafts and transfer structures like beams and slabs. For each type, examples of real buildings are provided along with details like slab depths, spans, and loading capacities. The document aims to illustrate how post-tensioning techniques have been implemented successfully in a wide variety of building construction projects.
Design of reinforced flat slabs to bs 8110 (ciria 110)bmxforu
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms for those who already suffer from conditions like anxiety and depression.
This document discusses the design of flat plate slabs. Flat plates are concrete slabs that are carried directly by columns without beams or girders. They are commonly used for spans up to 25 feet and loads up to 100 pounds per square foot. The load is directly transferred to the columns, making punching shear at the column connections critical. Proper reinforcement detailing is required between the slab and columns. Moment determination and shear design are important steps in the flat plate slab design process. Advantages include simplified formwork and reduced story height, while limitations include increased thickness and weight.
A grid slab is a type of building material that has two-directional reinforcement in the shape of a waffle. It can be used as both ceilings and floors, especially in areas requiring large spans with fewer columns. Features include panels on a 1 meter grid with trench mesh or individual bars. Grid slabs use less concrete and steel than conventional slabs while providing strength and resistance to cracking and sagging. Construction involves arranging a framework, fixing connectors and pods, then removing forms. Services like HVAC, plumbing and wiring can be run through holes in modified grid slabs. Benefits include flexibility, lighter weight, speed of construction, vibration control and fire resistance. Famous structures using grid slabs include terminals,
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1. The panel size is 5m x 7m without drop or column head.
2. The width of the column strip is calculated as 0.25x7m = 1.75m on each side of the column.
3. The required reinforcement is calculated for bending moments in the column strip and middle strip along the longer and shorter spans based on the loading and design parameters. The reinforcement details are shown in diagrams.
1) Two-way slabs are slabs with reinforcement in two directions because bending occurs in both directions when the L/S ratio is less than 2.
2) The document discusses various types of two-way slabs and design methods, focusing on the direct design method (DDM).
3) DDM involves determining the total factored static moment, distributing it to positive and negative moments, then distributing those moments to column and middle strips based on ratios of flexural and torsional stiffness.
Design of column base plates anchor boltKhaled Eid
This document discusses the design of column base plates and steel anchorage to concrete. It covers base plate materials and design for different load cases including axial, moment, and shear loads. It also discusses anchor rod types, materials, and design for tension and shear loading based on calculations of the steel and concrete breakout strengths according to building codes.
This document provides information on the design of reinforced concrete columns, including:
- Columns transmit loads vertically to foundations and may resist both compression and bending. Common cross-sections are square, circular and rectangular.
- Columns are classified as braced or unbraced depending on lateral stability, and short or slender based on buckling resistance. Short column design considers axial load capacity while slender column design accounts for second-order effects.
- Reinforcement details include minimum longitudinal bar size and spacing and design of lateral ties. Slender column design determines loadings and calculates moments from stiffness, deflection and biaxial bending effects. Design charts are used to select reinforcement for columns under axial and uniaxial
This document discusses the design of column base plates and steel anchorage to concrete. It provides an introduction to base plates and anchor rods, including materials and design considerations. It then covers the design of base plates for different load cases such as axial load, axial load plus moment, and axial load plus shear. Finally, it discusses the design of anchor rods for tension and shear loading based on the requirements in the ACI 318 code. The design procedures aim to ensure adequate load transfer from the steel column to the concrete foundation.
The document discusses guidelines for detailing reinforcement in concrete structures. It begins by defining detailing as the preparation of working drawings showing the size and location of reinforcement. Good detailing ensures reinforcement and concrete interact efficiently. The document then discusses sources of tension in concrete structures from various loading conditions like bending, shear, and connections. It provides equations from AS3600-2009 for calculating minimum development lengths for reinforcing bars to develop their yield strength based on bar size, concrete strength, and transverse reinforcement. It also discusses lap splice requirements. In summary, the document provides best practice guidelines for detailing reinforcement to efficiently resist loads and control cracking in concrete structures.
This document discusses the design of two-way floor slabs and footings. It covers the direct design method for two-way slabs without beams, examples of slab design, shear failure mechanisms, design for two-way shear, and shear reinforcement options. For footings, it defines footing types, soil pressure distribution, design considerations including bearing capacity and reinforcement, sizing footings based on soil pressure, and design for one-way and two-way shear as well as flexural strength. It also addresses bearing capacity at the column base and dowel requirements.
Design of flat plate slab and its Punching Shear Reinf.MD.MAHBUB UL ALAM
This document provides design considerations and an example problem for designing a flat plate slab using the Direct Design Method (DDM). It discusses slab thickness, load calculations, moment distribution, and reinforcement design for a sample four-story building with 16'x20' panels supported by 12" square columns. The design of panel S-4 is shown in detail, calculating loads, moments, and reinforcement requirements for the column and middle strips in both the long and short directions.
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3. The main considerations for slab design discussed are effective span, deflection control, reinforcement requirements including minimum area, maximum bar diameter and cover, and load calculations.
This document provides an overview of the design of rectangular reinforced concrete beams that are singly or doubly reinforced. It defines key assumptions in the design process including plane sections remaining plane after bending. It also covers evaluation of design parameters such as moment factors, strength reduction factors, and balanced reinforcement ratios. The design procedures for singly and doubly reinforced beams are described including checking crack width for singly reinforced beams. Figures are also provided to illustrate concepts such as stress distributions and the components of a doubly reinforced beam.
This document defines key terms related to compression members, classifies columns based on reinforcement type, loadings, and slenderness ratio, and outlines design assumptions. It defines effective length, pedestal, column, and wall. It classifies columns as tied, helically reinforced, or composite. Columns are classified by loadings as subjected to axial load only, axial with uniaxial bending, or axial with bi-axial bending. Columns are classified as short or slender based on slenderness ratios. Design assumes minimum eccentricity and considers different failure modes.
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A column is a vertical structural member subjected to compression and bending forces. Short columns fail through crushing or splitting, while slender columns fail through buckling. The document provides examples of calculating required reinforcement area and diameter for a short reinforced concrete column. It also provides examples of calculating the critical buckling load of a rod and determining a suitable universal column section for a given load based on its effective length and slenderness ratio.
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1) The direct design method and equivalent frame method for determining moments at critical sections.
2) Distributing the total design moment between positive and negative moments.
3) Distributing moments laterally between column strips, middle strips, and beams.
4) A 5-step basic design procedure involving determining moments, distributing moments, sizing reinforcement, and designing beams if present.
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.
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Natural language processing (NLP) has
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In the world with high technology and fast
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choice for recruitment. E-Recruitment is being done
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Key Words : Talent Management, Talent Acquisition , E-
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1. 1.1 INTRODUCTION
Common practice of design and construction is to support the slabs by beams and support the beams
by columns. This may be called as beam-slab construction. The beams reduce the available net clear
ceiling height. Hence in warehouses, offices and public halls some times beams are avoided and slabs
are directly supported by columns. This types of construction is aesthetically appealing also. These
slabs which are directly supported by columns are called Flat Slabs. Fig. 1.1 shows a typical flat slab.
d
2
Critical section for shear
Fig. 1.1 A typical flat slab (without drop and column head)
The column head is some times widened so as to reduce the punching shear in the slab. The
widened portions are called column heads. The column heads may be provided with any angle from
the consideration of architecture but for the design, concrete in the portion at 45º on either side of
vertical only is considered as effective for the design [Ref. Fig. 1.2].
d
2
Critical section for shear
Concrete in this area is
neglected for calculation
90°
Fig. 1.2 Slab without drop and column with column head
1
Flat Slabs
CHAPTER
2. 2 Advanced R.C.C. Design
Moments in the slabs are more near the column. Hence the slab is thickened near the columns by
providing the drops as shown in Fig. 1.3. Sometimes the drops are called as capital of the column.
Thus we have the following types of flat slabs:
Critical section for shear
d
2
d
2
Critical section
for shear
Fig. 1.3 Slab with drop and column without column head
(i) Slabs without drop and column head (Fig. 1.1).
(ii) Slabs without drop and column with column head (Fig. 1.2).
(iii) Slabs with drop and column without column head (Fig. 1.3).
(iv) Slabs with drop and column head as shown in Fig. 1.4.
Critical section
for shear
45° 45°
d
2
Fig. 1.4 Slab with drop and column with column head
The portion of flat slab that is bound on each of its four sides by centre lines of adjacent columns is
called a panel. The panel shown in Fig. 1.5 has size L1 ´ L2. A panel may be divided into column strips
and middle strips. Column Strip means a design strip having a width of 0.25L1 or 0.25L2,
whichever is less. The remaining middle portion which is bound by the column strips is called middle
strip. Fig. 1.5 shows the division of flat slab panel into column and middle strips in the direction y.
3. Flat Slabs 3
L2a L2b
C of panel A C of panel B
Middle stripMiddle strip
Column strip
L2a
4
L2b
4
Column strip Column strip
y
xo
L1
but
L
< 1
4
but
L
< 1
4
Fig. 1.5 Panels, column strips and middle strips is y-direction
1.2 PROPORTIONING OF FLAT SLABS
IS 456-2000 [Clause 31.2] gives the following guidelines for proportioning.
1.2.1 Drops
The drops when provided shall be rectangular in plan, and have a length in each direction not less than
one third of the panel in that direction. For exterior panels, the width of drops at right angles to the non
continuous edge and measured from the centre-line of the columns shall be equal to one half of the
width of drop for interior panels.
1.2.2 Column Heads
Where column heads are provided, that portion of the column head which lies within the largest right
circular cone or pyramid entirely within the outlines of the column and the column head, shall be
considered for design purpose as shown in Figs. 1.2 and 1.4.
1.2.3 Thickness of Flat Slab
From the consideration of deflection control IS 456-2000 specifies minimum thickness in terms of
span to effective depth ratio. For this purpose larger span is to be considered. If drop as specified in
1.2.1 is provided, then the maximum value of ratio of larger span to thickness shall be
= 40, if mild steel is used
= 32, if Fe 415 or Fe 500 steel is used
If drops are not provided or size of drops do not satisfy the specification 1.2.1, then the ratio shall
not exceed 0.9 times the value specified above i.e.,
= 40 ´ 0.9 = 36, if mild steel is used.
= 32 ´ 0.9 = 28.8, if HYSD bars are used
It is also specified that in no case, the thickness of flat slab shall be less than 125 mm.
4. 4 Advanced R.C.C. Design
1.3 DETERMINATION OF BENDING MOMENT AND SHEAR FORCE
For this IS 456-2000 permits use of any one of the following two methods:
(a) The Direct Design Method
(b) The Equivalent Frame Method
1.4 THE DIRECT DESIGN METHOD
This method has the limitation that it can be used only if the following conditions are fulfilled:
(a) There shall be minimum of three continuous spans in each directions.
(b) The panels shall be rectangular and the ratio of the longer span to the shorter span within a panel
shall not be greater than 2.
(c) The successive span length in each direction shall not differ by more than one-third of longer
span.
(d) The design live load shall not exceed three times the design dead load.
(e) The end span must be shorter but not greater than the interior span.
(f) It shall be permissible to offset columns a maximum of 10 percent of the span in the direction
of the offset not withstanding the provision in (b).
Total Design Moment
The absolute sum of the positive and negative moment in each direction is given by
M0 =
WL
8
n
Where,
M0 = Total moment
W = Design load on the area L2 ´ Ln
Ln = Clear span extending from face to face of columns, capitals, brackets or walls but
not less than 0.65 L1
L1 = Length of span in the direction of M0; and
L2 = Length of span transverse to L1
In taking the values of Ln, L1 and L2, the following clauses are to be carefully noted:
(a) Circular supports shall be treated as square supports having the same area i.e., squares of size
0.886D.
(b) When the transverse span of the panel on either side of the centre line of support varies, L2 shall
be taken as the average of the transverse spans. In Fig. 1.5 it is given by
L L2 2
2
a b+b g.
(c) When the span adjacent and parallel to an edge is being considered, the distance from the edge
to the centre-line of the panel shall be substituted for L2.
Distribution of Bending Moment in to –ve and +ve Moments
The total design moment M0 in a panel is to be distributed into –ve moment and +ve moment as
specified below:
5. Flat Slabs 5
In an interior span
Negative Design Moment 0.65 M0
Positive Design Moment 0.35 M0
In an end span
Interior negative design moment
= 0 75
010
1
1
.
.
-
+
L
N
MM
O
Q
PPac
M0
Positive design moment
= 0 63
0 28
1
1 0.
.
-
+
L
N
MM
O
Q
PPac
M
Exterior negative design moment
=
0 65
1
1 0
.
+
L
N
MM
O
Q
PPac
M
where ac is the ratio of flexural stiffness at the exterior columns to the flexural stiffness of the slab at
a joint taken in the direction moments are being determined and is given by
ac =
K
K
c
s
∑
∑
Where,
Kc = Sum of the flexural stiffness of the columns meeting at the joint; and
Ks = Flexural stiffness of the slab, expressed as moment per unit rotation.
Distribution of Bending Moments Across the Panel Width
The +ve and –ve moments found are to be distributed across the column strip in a panel as shown in
Table 1.1. The moment in the middle strip shall be the difference between panel and the column strip
moments.
Table 1.1 Distribution of Moments Across the Panel Width in a Column Strip
S. No. Distributed Moment Per cent of Total Moment
a Negative BM at the exterior support 100
b Negative BM at the interior support 75
c Positive bending moment 60
6. 6 Advanced R.C.C. Design
Moments in Columns
In this type of constructions column moments are to be modified as suggested in IS 456–2000
[Clause No. 31.4.5].
Shear Force
The critical section for shear shall be at a distance
d
2
from the periphery of the column/capital drop
panel. Hence if drops are provided there are two critical sections near columns. These critical sections
are shown in Figs. 1.1 to 1.4. The shape of the critical section in plan is similar to the support
immediately below the slab as shown in Fig. 1.6.
d/2
d/2
Critical
section
Support section
column / column head
( )a
d/2
Support
section
Critical
section ( )b
Fig. 1.6
For columns sections with re-entrant angles, the critical section shall be taken as indicated in Fig. 1.7.
Critical
section
Support
section
d/2
d/2
( )a
d/2
d/2
d/2
Critical
section
Support
section
( )b
Fig. 1.7
In case of columns near the free edge of a slab, the critical section shall be taken as shown in Fig. 1.8.
d/2
d/2
Critical
section
Free
edge
( )a
Critical
section
Free
corner
Corner
column
( )b
Fig. 1.8
7. Flat Slabs 7
The nominal shear stress may be calculated as
tv =
V
b d0
where V – is shear force due to design
b0 – is the periphery of the critical section
d – is the effective depth
The permissible shear stress in concrete may be calculated as ks tc, where ks = 0.5 + bc but not
greater than 1, where bc is the ratio of short side to long side of the column/capital; and
tc = 0 25. fck
If shear stress tv < tc – no shear reinforcement are required. If tc < tv < 1.5 tc, shear reinforcement
shall be provided. If shear stress exceeds 1.5 tc flat slab shall be redesigned.
1.5 EQUIVALENT FRAME METHOD
IS 456–2000 recommends the analysis of flat slab and column structure as a rigid frame to get design
moment and shear forces with the following assumptions:
(a) Beam portion of frame is taken as equivalent to the moment of inertia of flat slab bounded
laterally by centre line of the panel on each side of the centre line of the column. In frames
adjacent and parallel to an edge beam portion shall be equal to flat slab bounded by the edge and
the centre line of the adjacent panel.
(b) Moment of inertia of the members of the frame may be taken as that of the gross section of the
concrete alone.
(c) Variation of moment of inertia along the axis of the slab on account of provision of drops shall
be taken into account. In the case of recessed or coffered slab which is made solid in the region
of the columns, the stiffening effect may be ignored provided the solid part of the slab does not
extend more than 0.15 lef into the span measured from the centre line of the columns. The
stiffening effect of flared columns heads may be ignored.
(d) Analysis of frame may be carried out with substitute frame method or any other accepted
method like moment distribution or matrix method.
Loading Pattern
When the live load does not exceed ¾th of dead load, the maximum moments may be assumed to
occur at all sections when full design live load is on the entire slab.
If live load exceeds ¾th dead load analysis is to be carried out for the following pattern of loading also:
(i) To get maximum moment near mid span
– ¾th of live load on the panel and full live load on alternate panel
(ii) To get maximum moment in the slab near the support
– ¾th of live load is on the adjacent panel only
It is to be carefully noted that in no case design moment shall be taken to be less than those
occurring with full design live load on all panels.
The moments determined in the beam of frame (flat slab) may be reduced in such proportion that
the numerical sum of positive and average negative moments is not less than the value of total design
8. 8 Advanced R.C.C. Design
moment M0 =
WLn
8
. The distribution of slab moments into column strips and middle strips is to be
made in the same manner as specified in direct design method.
1.6 SLAB REINFORCEMENT
Spacing
The spacing of bars in a flat slab, shall not exceed 2 times the slab thickness.
Area of Reinforcement
When the drop panels are used, the thickness of drop panel for determining area of reinforcement
shall be the lesser of the following:
(a) Thickness of drop, and
(b) Thickness of slab plus one quarter the distance between edge of drop and edge of capital.
The minimum percentage of the reinforcement is same as that in solid slab i.e., 0.12 percent if
HYSD bars used and 0.15 percent, if mild steel is used.
Minimum Length of Reinforcement
At least 50 percent of bottom bars should be from support to support. The rest may be bent up. The
minimum length of different reinforcement in flat slabs should be as shown in Fig. 1.9 (Fig. 16 in IS 456–
2000). If adjacent spans are not equal, the extension of the –ve reinforcement beyond each face shall be
based on the longer span. All slab reinforcement should be anchored property at discontinuous edges.
Example 1.1: Design an interior panel of a flat slab of size 5 m ´ 5 m without providing drop and
column head. Size of columns is 500 ´ 500 mm and live load on the panel is 4 kN/m2
. Take floor
finishing load as 1 kN/m2
. Use M20 concrete and Fe 415 steel.
Solution:
Thickness
Since drop is not provided and HYSD bars are used span to thickness ratio shall not exceed
1
0 9 32
1
28 8. .×
=
Minimum thickness required
=
Span
28 8
5000
28 8. .
= = 173.6 mm
Let d = 175 mm and D = 200 mm
Loads
Self weight of slab = 0.20 ´ 25 = 5 kN/m2
Finishing load = 1 kN/m2
Live load = 4 kN/m2
Total working load = 10 kN/m2
Factored load = 1.5 ´ 10 = 15 kN/m2
9. Flat Slabs 9
Minimum
percentage
of steel
at section
50
Remainder
WITHOUT DROP PANEL WITH DROP PANEL
d
b
75 mm max
150 mm
d
b
c
24 BAR DIA OR
ed
b b
e
b
150 mm min.
DROPbd
b e
150 mmg
e
b
300 mm min.
g
EDGE OF
DROP
75 mm max.
150 mm
75 mm max.
150 mm150 mm
(ALL BARS) (ALL BARS)
150 mm
75 mm max.75 mm max.
150 mm
c
c
c
c a
a cc
ff
D
C
D D
C C
Clear span - ln
Face of support
interior support
Exterior
support
MiddleStripColumnstripStrip
Type
ofbars
StraightbarsBentbars*StraightbarsBentbars*
50
Remainder
50
Remainder
50
Remainder
100
50
Remainder
50
Remainder
50
Remainder
Clear span - ln
Face of support
interior support
C
0.15 maxl
o.15 maxl
0.125lmax
300 mm min. ALL BARS
EDGE OF
24BAR DIA OR
[NO SLAB CONTINUITY] [CONTINUITY PROVED] [NO SLAB CONTINUITY]
Bar Length From Face of Support
Minimum Length Maximum Length
Mark a b c d e f g
Length 0.14 ln 0.20 ln 0.22 ln 0.30 ln 0.33 ln 0.20 ln 0.24 ln
* Bent bars at exterior supports may be used if a general analysis is made.
Note. D is the diameter of the column and the dimension of the rectangular column in the direction under consideration.
Fig. 1.9 Minimum bend joint locations and extensions for reinforcement in flat slabs
10. 10 Advanced R.C.C. Design
Ln = 5 – 0.5 = 4.5 m
Total design load in a panel W = 15 L2 Ln = 15 ´ 5 ´ 4.5 = 337.5 kN
Moments
Panel Moment M0 =
WL
kNmn
8
3375
4 5
8
18984= ´ =.
.
.
Panel –ve moment = 0.65 ´ 189.84 = 123.40 kNm
Panel +ve moment = 0.35 ´ 189.84 = 0.35 ´ 189.84 = 66.44 kNm
Distribution of moment into column strips and middle strip:
Column Strip in kNm Middle Strip in kNm
–ve moment 0.75´ 123.40 = 92.55 30.85
+ve moment 0.60´ 66.44 = 39.86 26.58
Checking the thickness selected:
Since Fe 415 steel is used,
Mu lim = 0.138 fck b d2
Width of column strip = 0.5 ´ 5000 = 2500 mm
Mu lim = 0.138 ´ 20 ´ 2500 ´ 1752
= 211.3125 ´ 106
Nmm
= 211.3125 kNm
Hence singly reinforced section can be designed i.e., thickness provided is satisfactory from the
consideration of bending moment.
Check for Shear
The critical section for shear is at a distance
d
2
from the column face. Hence periphery of critical
section around a column is square of a size = 500 + d = 500 + 175 = 675 mm
Shear to be resisted by the critical section
V = 15 ´ 5 ´ 5 – 15 ´ 0.675 ´ 0.675
= 368.166 kN
tv =
368166 1000
4 675 175
. ×
× ×
= 0.779 N/mm2
ks = 1 + bc subject to maximum of 1.
bc =
L
L
1
2
5
5
= = 1
ks = 1
tc = 0 25 0 25 20. .fck = = 1.118 N/mm2
safe in shear since tv < tc
675
675500
500
11. Flat Slabs 11
Reinforcement
For –ve moment in column strip:
Mu = 92.55 kNm
92.55 ´ 106
= 0 87 1. f d
bd
f
f
y st
st y
ck
A
A
−
L
NM O
QP
= 0.87 ´ 415 ´ Ast ´ 175 1
2500 175
415
20
−
×
×
L
NM O
QPAst
i.e., 1464.78 = Ast 1
21084 3
−
L
NM O
QP
Ast
.
i.e., Ast
2
– 21084.3Ast + 1464.78 ´ 21084.3 = 0
Ast = 1583.74 mm2
This is to be provided in a column strip of width 2500 mm. Hence using 12 mm bars, spacing
required is given by
s =
p 4 12
1583 74
2500
2
´
´
.
= 178 mm
Provide 12 mm bars at 175 mm c/c.
For +ve moment in column strip:
Mu = 39.86 kNm
39.86 ´ 106
= 0.87 ´ 415 ´ Ast ´ 175 1
2500 175
415
20
−
×
×
L
NM O
QPAst
630.86 = Ast 1
21084 3
−
L
NM O
QP
Ast
.
or Ast
2
– 21084.3 Ast + 630.86 ´ 21084.3 = 0
Ast = 651 mm2
Using 10 mm bars, spacing required is
s =
p 4 10
651
2500
2
´
´ = 301.6 mm < 2 ´ thickness of slab
Hence provide 10 mm bars at 300 mm c/c.
Provide 10 mm diameter bars at 300 mm c/c in the middle strip to take up –ve and +ve moments.
Since span is same in both directions, provide similar reinforcement in other direction also.
12. 12 Advanced R.C.C. Design
Reinforcement Details
It is as shown in Fig. 1.10
50005000 5000
5000
5000
5000
Column Strip Middle Strip Column strip
ColumnStripMiddleStripColumnstrip
10-300 c/c
10-300 c/c
500
10 - 300 cc
200
500
Cover -25
12-175 c/c
Section through column strip
500 500
30003000 10 - 300 c/c
section through middle strip
Top reinforcement
Sign convention
Bottom reinforcement
12-175 c/c
12-175 c/c
Fig. 1.10 Reinforcement details [all dimension in mm units]
Example 1.2: Design an interior panel of a flat slab with panel size 6 ´ 6 m supported by columns of
size 500 ´ 500 mm. Provide suitable drop. Take live load as 4 kN/m2
. Use M20 concrete and Fe 415
steel.
Solution :
Thickness : Since Fe 415 steel is used and drop is provided, maximum span to thickness ratio
permitted is 32
Thickness of flat slab =
6000
32
= 187.5 mm
Provide 190 mm thickness. Let the cover be 30 mm
Overall thickness D = 220 mm
Let the drop be 50 mm. Hence at column head, d = 240 mm and D = 270 mm
13. Flat Slabs 13
Size of Drop
It should not be less than
1
3
6´ m = 2 m
Let us provide 3 m ´ 3 m drop so that the width of drop is equal to that of column head.
Width of column strip = width of middle strip = 3000 mm.
Loads
For the purpose of design let us take self-weight as that due to thickness at column strip
Self-weight = 0.27 ´ 1 ´ 1 ´ 25 = 6.75 kN/m2
Finishing load = 1.00 kN/m2
Live load = 4.00 kN/m2
Total load = 11.75 kN/m2
Design (factored) load = 1.5 ´ 11.75 = 17.625 kN/m2
Clear span Ln = 6 – 0.5 = 5.5 m
Design load W0 = Wu ´ L2 ´ Ln
= 17.625 ´ 6 ´ 5.5
= 581.625 kN
Design Total Moment
Total moment
M0 =
W L0
8
581625 55
8
n
=
´. .
= 400 kNm
Total negative moment = 0.65 ´ 400 = 260 kNm
Total positive moment = 0.35 ´ 400 = 140 kNm
The above moments are to be distributed into column strip and middle strip
Column Strip Middle Strip
–ve moment 0.75´ 260 = 195 kNm 0.25´ 260 = 65 kNm
+ve moment 0.6´ 140 = 84 kNm 0.4´ 140 = 56 kNm
Width of column strip = width of middle strip = 3000 mm
Mu lim = 0.138 fck b d2
= 0.138 ´ 20 ´ 3000 ´ 2402
= 476.928 ´ 106
Nmm
= 476.928 kNm
Thus Mu lim > Mu. Hence thickness selected is sufficient.
Check for Shear
The critical section is at a distance
14. 14 Advanced R.C.C. Design
d
2
=
240
2
= 120 mm from the face of column
It is a square of size = 500 + 240 = 740 mm
V = Total load – load on 0.740 ´ 0.740 area
= 17.625 ´ 6 ´ 6 – 17.625 ´ 0.740 ´ 0.740
= 624.849 kN
Nominal shear = tv =
624 489 1000
4 740 240
. ×
× ×
= 0.880 N/mm2
Shear strength = ks tc
where ks = 1 + bc subject to maximum of 1
where bc =
L
L
1
2
= 1
ks = 1
tc = 0 25 20. = 1.118 N/mm2
Design shear stress permitted
= 1.118 N/mm2
> tv
Hence the slab is safe in shear without shear reinforcement also.
Shear strength may be checked at distance
d
2
from drop. It is quite safe since drop size is large.
Reinforcement
(a) For –ve moment in column strip
Mu = 195 kNm
Thickness d = 240 mm
Mu = 0.87 fy Ast d 1 −
×
×
L
NM O
QPAst y
ckb d
f
f
195 ´ 106
= 0.87 ´ 415 ´ Ast ´ 240 1
3000 240
415
20
−
×
×
L
NM O
QPAst
2250.38 = Ast 1
34698 8
−
L
NM O
QP
Ast
.
Ast
2
– 34698.8 Ast + 2250.38 ´ 34698.8 = 0
Ast = 2419 mm2
in 3000 mm width
500
500
500 740
740
120 120
15. Flat Slabs 15
Using 12 mm bars, spacing required is
s =
p 4 12
2419
3000
2
´
´ = 140.26 mm
Provide 12 mm bars at 140 mm c/c
(b) For +ve moment in column strip
Mu = 84 kNm = 84 ´ 106
Nmm. Thickness d = 190 mm
84 ´ 106
= 0.87 ´ 415 ´ Ast ´ 190 1
3000 240
415
20
−
×
×
L
NM O
QPAst
1224.5 = Ast 1
27469 9
−
L
NM O
QP
Ast
.
Ast = 1285 mm2
Using 10 mm bars
s =
p 4 10
1285
3000
2
´
´ = 183 mm
Provide 10 mm bars at 180 mm c/c
(c) For –ve moment in middle strip:
Mu = 65 kNm; Thickness = 190 mm
65 ´ 106
= 0.87 ´ 415 ´ Ast ´ 190 1
3000 190
415
20
−
×
×
L
NM O
QPAst
947.5 = Ast 1
27469 9
−
L
NM O
QP
Ast
.
Ast
2
– 27469.9 Ast + 947.5 ´ 27469.9 = 0
Ast = 983 mm2
in 3000 mm width
Using 10 mm bars
s =
p 4 10
983
3000
2
´
´ = 239.7 mm
Provide 10 mm bars at 230 mm c/c
(d) For +ve moment in middle strip
Mu = 56 kNm; Thickness = 190 mm
Provide 10 mm bars at 230 mm c/c in this portion also.
Since span is same in both direction, provide similar reinforcement in both directions. The details
of reinforcement are shown in Fig. 1.11.
16. 16 Advanced R.C.C. Design
6000
Column strip
Middle strip
Column strip
Columnstrip
Middlestrip
Columnstrip
6000 6000
6000
6000
6000
=Do p widthr=Do p widthr
=Dorpwidth=Dorpwidth
12 140 c/c–
10 230 c/c–
500 500
240
10 230@
12 @ 140 10 180 c/c@
190
Cover - 30
Section through column strip
10 230 c/c@
240
190
500 500
10 180c/c–
12 230c/c–
10–180c/c
Fig. 1.11 Reinforcement details
Example 1.3: Design the interior panel of the flat slab in example 1.2, providing a suitable column
head, if columns are of 500 mm diameter.
Solution: Let the diameter of column head be
= 0.25L = 0.25 ´ 6 = 1.5 m
It’s equivalent square has side ‘a’ where
π
4
152
× . = a2
a = 1.33 m
Ln = 6 – 1.33 = 4.67 m
W0 = 17.625 ´ 6 ´ 4.67 = 493.85 kN
M0 =
W Lo n
8
49385 4 67
8
=
×. .
= 288.3 kNm
17. Flat Slabs 17
Total –ve moment = 0.65 ´ 288.3 = 187.4 kNm
Total +ve moment = 0.35 ´ 288.3 = 100.9 kNm
The distribution of above moment into column strip and middle strips are as given below:
Column Strip Middle Strip
–ve moment 0.75´ 187.4 = 140.55 kNm 0.25´ 187.4 = 46.85kNm
+ve moment 0.60´ 100.9 = 60.54kNm 0.4´ 100.9 = 40.36kNm
Width of column strip = width of middle strip = 3000 mm
Mu lim = 0.138 fck bd2
= 0.138 ´ 20 ´ 3000 ´ 2402
= 476.928 ´ 106
Nmm > Mu
Hence thickness selected is sufficient.
Check for Shear
The critical section is at a distance
d
2
=
240
2
= 120 mm from the face of column head
Diameter of critical section = 1500 + 240 =1740 mm
= 1.740 m
Perimeter of critical section = p D
= 1.740 p
Shear on this section
V = 17 625 6 6
4
1742
. .´ - ´
L
NM O
QP
p
= 592.59 kN
tv =
592 59 1000
1740 240
. ×
× ×π
= 0.45 N/mm2
Maximum shear permitted = ks × 0 25 20.
= 1.118 N/mm2
Since ks works out to be 1
Since maximum shear permitted in concrete is more than nominal shear tv, there is no need to
provide shear reinforcement
Design of Reinforcement
(a) For –ve moment in column strip
Mu = 140.55 kNm; d = 240 mm
140.55 ´ 106
= 0.87 ´ 415 ´ Ast ´ 240 1
3000 240
415
20
−
×
×
L
NM O
QPAst
1622 = Ast 1
34698 8
−
L
NM O
QP
Ast
.
1500 120
18. 18 Advanced R.C.C. Design
Ast
2
– 34698.8 Ast + 1622 ´ 34698.8 = 0
Ast = 1705 mm2
Using 12 mm bars,
s =
π 4 12
1705
3000
2
×
× = 199 mm
Provide 12 mm bars at 190 mm c/c.
(b) For the +ve moment in column strip
Mu = 60.54 kNm; d = 190 mm
60.54 ´ 106
= 0.87 ´ 415 ´ Ast ´ 190 1
3000 190
415
20
−
×
×
L
NM O
QPAst
882.51 = Ast 1
27469 9
−
L
NM O
QP
Ast
.
Ast
2
– 27469.9 Ast + 882.51 ´ 27469.9 = 0
Ast = 913 mm2
Using 10 mm bars
s =
π 4 10
913
3000
2
×
× = 258 mm
Provide 10 mm bars at 250 mm c/c.
(c) For –ve moment in middle strip:
Mu = 46.85 kNm; d = 190 mm
46.85 ´ 106
= 0.87 ´ 415 ´ Ast ´ 190 1
3000 190
415
20
−
×
×
L
NM O
QPAst
683 = Ast 1
27469 9
−
L
NM O
QP
Ast
.
Ast
2
– 27469.9Ast + 683 ´ 27469.9 = 0
Ast = 701 mm2
Using 10 mm bars,
s =
π 4 10
701
3000
2
×
× = 336 mm
Provide 10 mm bars at 300 mm c/c.
(d) Provide 10 mm bars at 300 mm c/c for +ve moment in middle strip also.
As span is same in both directions, provide similar reinforcement in both directions. Reinforcement
detail may be shown as was done in previous problem.
Example 1.4: A flat slab system consists of 5 m ´ 6 m panels and is without drop and column head.
It has to carry a live load of 4 kN/m2
and a finishing load of 1 kN/m2
. It is to be designed using M20
grade concrete and Fe 415 steel. The size of the columns supporting the system is 500 ´ 500 mm and
floor to floor height is 4.5 m. Calculate design moments in interior and exterior panels at column and
middle strips in both directions.
19. Flat Slabs 19
Solution:
Thickness: Since Fe 415 steel is used and no drops are provided, longer span to depth ratio is not
more than 32 ´ 0.9 = 28.8
d =
6000
28 8.
= 208
Let us select d = 210 mm and D = 240 mm
Loads
Self weight 0.24 ´ 1 ´ 1 ´ 25 = 6 kN/m2
Finishing weight = 1 kN/m2
Live load = 4 kN/m2
Total = 11 kN/m2
Wu = 1.5 ´ 11 = 16.5 kN/m2
Panel Dimensions
Along length
L1 = 6 m and L2 = 5 m
Width of column strip = 0.25 L1 or L2 whichever is less.
= 0.25 ´ 5 = 1.25 m on either side of column centre line
Total width of column strip = 1.25 ´ 2 = 2.5 m
Width of middle strip = 5 – 2.5 = 2.5 m
Along Width
L1 = 5 m L2 = 6 m
Width of column strip = 0.25 ´ 5 = 1.25 m on either side
Total width of column strip = 2.5 m
Hence, width of middle strip = 6 – 2.5 = 3.5 m
INTERIOR PANELS
Moments Along Longer Size
L1 = 6 m L2 = 5 m
Ln = 6 – 0.5 = 5.5 m subject to minimum of 0.65 ´ L1 = 3.9 m
Ln = 5.5 m
Load on panel W0 = 16.5 ´ L2Ln
= 16.5 ´ 5 ´ 5.5 = 453.75 kN
20. 20 Advanced R.C.C. Design
M0 =
W L0
8
45375 55
8
n
=
´. .
= 311.95 kNm
Appropriation of Moment
Total –ve moment = 0.65 ´ 311.95 = 202.77 kNm
Total +ve moment = 311.95 – 202.77 = 109.18 kNm
Hence moment in column strip and middle strip along longer direction in interior panels are as given
below:
Column Strip Middle Strip
–ve moment 0.75´ 202.75 = 152.06 kNm 202.75 – 152.06 = 50.69kNm
+ve moment 0.60´ 109.18 = 65.51kNm 109.18 – 65.51 = 43.67kNm
Along Width
L1 = 5 m L2 = 6 m and Ln = 5 – 0.5 = 4.5 m.
Panel load = W0 = 16.5 ´ 6 ´ 4.5 = 445.5 kN
Panel moment M0 = W
L
0
8
4455 45
8
n
=
´. .
= 250.59 kN-m
Appropriation of Moment:
Total –ve moment = 0.65 ´ 250.59 = 162.88 kN-m
Total +ve moment = 250.59 – 162.88 = 87.71 kN-m
Moments in column strip and middle strip are as shown below:
Column Strip Middle Strip
–ve moment 0.75´ 162.88 = 122.16 kNm 0.25´ 162.88 = 40.72kNm
+ve moment 0.60´ 87.71 = 52.63kNm 0.40´ 87.71 = 35.08kNm
EXTERIOR PANELS
Length of column = 4.5 – 0.24 = 4.26 m
The building is not restrained from lateral sway. Hence as per Table 28 in IS 456-2000, effective
length of column
= 1.2 ´ length = 1.2 ´ 4.26 = 5.112 m
Size of column = 500 ´ 500 mm
Moment of inertia of column =
1
12
5004 4
× mm
21. Flat Slabs 21
kc =
I
L
1
12
= ×
500
5112
4
= 101844 mm4
LONGER SPAN DIRECTION
Moment of inertia of beam
Is = Moment of inertia of slab
=
1
12
6000 2403
× ×
Its length = L2 = 5000 mm
kc =
I
5000
s
= ´
´1
12
6000 240
5000
3
= 1382400 mm4
Live load
Dead load
=
4
7
< 0.75
Relative stiffness ratio is
ac =
k k
k
c c
s
1 2 2 1018844
1382400
+
=
×
= 1.474
a = 1
1
1
1
1474
+ = +
ac .
= 1.678
Hence various moment coefficients are:
Interior –ve moment coefficient = 0.75 –
01.
α
= 0.690
Exterior –ve moment coefficient =
0.65
α
= 0.387
Positive moment coefficient = 0.63 –
0.28
α
= 0.463
Total moment M0 = 311.95 kNm
Appropriation of moments in kNm is as given below:
Total Column Strip Middle Strip
Interior –ve 0.69´ 311.95 = 215.25 0.75´ 215.25 = 161.43 215.25 – 161.43 = 53.82
Exterior –ve 0.387´ 311.95 = 120.72 1.00´ 120.72 = 120.72 120.72 – 120.72 = 0
+ Moment 0.463´ 31.95 = 144.43 0.60´ 144.43 = 86.66 144.43 – 86.66 = 57.77
Shorter Span Direction
ks =
1
12
5000 240
6000
3
×
×
= 96000
ac =
k k
k
c c
s
1 2 2 1018844
960000
+
=
×
= 2.123
22. 22 Advanced R.C.C. Design
a1 = 1
1
+
αc
= 1.471
Interior –ve moment coefficient = 0.75 –
0 1
0 75
0 1
1 471
.
.
.
.a
= - = 0.682
Exterior –ve moment coefficient =
0.65 0.65
α
=
1 471.
= 0.442
Positive moment coefficient = 0.63 –
0.28 0.28
α
= −0 63
1 471
.
.
= 0.440
Total moment M0 = 250.59 kNm
Appropriation of moments in shorter span exterior panel in kNm is as given below:
Total Column Strip Middle Strip
Interior –ve 0.682´ 250.59 = 170.90 0.75´ 170.76 = 128.18 170.90 – 128.18 = 42.72
Exterior -ve 0.442´ 250.59 = 110.76 1.00´ 110.76 = 110.76 110.76 – 110.76 = 0
+ Moment 0.44´ 250.59 = 110.25 0.60´ 110.25 = 66.16 110.25 – 66.16 = 44.09
In the exterior panel in each column strips half the above values will act. These moments are
shown in Fig. 1.12
Strip
Col Middle
Strip
2.5
1.25
Strip
Col Middle
Strip Strip
Col
2.5 2.5 2.5
–120.72
–122.16
–53.82
52.63
–161.43 –15.06
2
–122.16
–50.69
52.63
–152.06
–122.16
86.66
2
–40.72
57.77
35.08
–40.72
43.67
35.08
65.51
–40.72
–152.06
–122.16
2
–128.18
–50.69
66.16
2
–161.43 –152.06
2
–122.16
2–128.18
66.16
2
52.63
2
–53.82120.72
–122.16
2
–128.18
86.66
2
–42.72
57.77
44.09
–42.72
43.67
44.09
65.51
–42.72
–152.06
–110.76
66.16
–50.69
–161.43
–152.06
2
–110.76
66.16
2
–53.82120.72
–4
–110.76
2.5 m
2.5 m
3.5 m
3.5 m
1.25 m
86 66
2
65 51
2
. .
+
86 66
2
65 51
2
. .
+
52 63
2
.
Fig. 1.12
23. Flat Slabs 23
REVIEW QUESTIONS
1. Design the typical interior panel of a flat slab floor of size 5 m ´ 5 m with suitable drop to
support a live load of 4 kN/m2
. The floor is supported by columns of size 450 mm ´ 450 mm.
Use M20 concrete and Fe 415 steel. Sketch the reinforcement details by showing cross sec-
tions
(i) at column strip
(ii) at middle strip.
2. Design the exterior panel of a flat slab of size 6 m ´ 6 m with suitable drop to support a live load
of 5 kN/m2
. The floor system is supported by columns of size 500 mm ´ 500 mm. Floor to
floor distance is 3.6 m. Use M20 concrete and Fe 415 steel.
3. For the flat slab system of size 6 m ´ 6 m provide suitable drop and fix up overall dimensions.
The floor system is supported by columns of size 500 mm ´ 500 mm, the floor height being 3.6 m.
Calculate the design moments at various strips in the interior and exterior panels. Give the plan
of the floor system showing these design moments.