This document discusses the design of reinforced concrete slabs. It begins by introducing different types of slabs used in construction like solid slabs, flat slabs, ribbed slabs, and waffle slabs. It then covers simplified analysis methods for slabs spanning in one or two directions using load and moment coefficients. The document also addresses shear design in slabs, discussing shear stresses and the need for shear reinforcement. It concludes by discussing punching shear analysis around concentrated loads and the importance of limiting span-depth ratios to control deflections in slabs.
The document summarizes a case study of a two-storey reinforced concrete bungalow located in Petaling Jaya, Selangor, Malaysia. Measurements were taken of the existing structure and 3D models were produced. The bungalow was extended on the sides and back. The structural system uses columns and beams, with identified structural elements including pads, beams, slabs, and stiffeners. An appraisal of the structural system is presented.
Lecture01 design of concrete deck slabs ( Highway Engineering )Hossam Shafiq I
This document discusses the design of deck slabs for bridges. It explains how truck loads are distributed across multiple stringers below the deck through load transfer mechanisms like the deck material, spacing of stringers and secondary members, and their relative stiffnesses. While load distribution can be calculated precisely, codes like AASHTO simplify this using distribution factors based on the deck type and stringer spacing. The document also mentions design considerations for reinforced concrete deck slabs, including drainage features and corrosion protection methods.
Reinforced concrete slabs are used in floors, roofs, and walls. They can span in one or two directions and be supported by beams, walls, or columns. This document discusses the design of reinforced concrete slabs, including types of slabs, load analysis, shear design, reinforcement details, and provides examples of designing solid slabs spanning in one direction. The goal is to teach students to properly design and analyze reinforced concrete slabs according to code.
This document provides methods for designing reinforced concrete slabs using working stress design and ultimate strength design. It discusses one-way and two-way slab design, including defining characteristics, load calculations, moment calculations, depth checks, and steel calculations. Formulas are provided for slab thickness selection, elastic constant calculation, load calculations considering dead and live loads, moment determination using code coefficients, minimum steel requirements, and distribution steel spacing.
This document provides information on the design of reinforced concrete beams, including:
1. It outlines the three basic design stages: preliminary analysis and sizing, detailed analysis of reinforcement, and serviceability calculations.
2. It describes how to calculate the lever arm, depth of the neutral axis, and required area of tension and compression reinforcement for singly and doubly reinforced beams.
3. It discusses considerations for preliminary sizing of beams, including required cover, breadth, effective depth, shear stress limits, and span-depth ratios. Trial calculations are suggested to determine suitable beam dimensions.
Development Length Hook Splice Of ReinforcementsSHERAZ HAMEED
This document discusses reinforcement development length, which is the minimum length required for bond stress to develop between steel reinforcement and concrete. It provides formulas to calculate development length based on factors like bar diameter, yield strength, concrete strength, and transverse reinforcement. The development length must be sufficient to prevent bar pullout under load. Standards like ACI Code specify minimum development lengths empirically related to these factors to ensure the bond can develop adequately.
Ring or circular rafts can be used for cylindrical structures such as chimneys, silos, storage tanks, TV-towers and other structures. In this case, ring or circular raft is the best suitable foundation to the natural geometry of such structures. The design of circular rafts is quite similar to that of other rafts.
This document presents information on the design of one-way slabs. It defines one-way slabs as having a ratio of longer to shorter side of at least 2.0 and experiencing load distribution in the direction perpendicular to supports. The minimum thickness is specified in the ACI code based on span length and support conditions. Loads assigned include dead and live loads. Temperature and shrinkage reinforcement is also required perpendicular to main reinforcement to control cracking. The design procedure involves calculating minimum thickness, factored loads, moments, steel ratios, required depth and detailing of reinforcement.
The document summarizes a case study of a two-storey reinforced concrete bungalow located in Petaling Jaya, Selangor, Malaysia. Measurements were taken of the existing structure and 3D models were produced. The bungalow was extended on the sides and back. The structural system uses columns and beams, with identified structural elements including pads, beams, slabs, and stiffeners. An appraisal of the structural system is presented.
Lecture01 design of concrete deck slabs ( Highway Engineering )Hossam Shafiq I
This document discusses the design of deck slabs for bridges. It explains how truck loads are distributed across multiple stringers below the deck through load transfer mechanisms like the deck material, spacing of stringers and secondary members, and their relative stiffnesses. While load distribution can be calculated precisely, codes like AASHTO simplify this using distribution factors based on the deck type and stringer spacing. The document also mentions design considerations for reinforced concrete deck slabs, including drainage features and corrosion protection methods.
Reinforced concrete slabs are used in floors, roofs, and walls. They can span in one or two directions and be supported by beams, walls, or columns. This document discusses the design of reinforced concrete slabs, including types of slabs, load analysis, shear design, reinforcement details, and provides examples of designing solid slabs spanning in one direction. The goal is to teach students to properly design and analyze reinforced concrete slabs according to code.
This document provides methods for designing reinforced concrete slabs using working stress design and ultimate strength design. It discusses one-way and two-way slab design, including defining characteristics, load calculations, moment calculations, depth checks, and steel calculations. Formulas are provided for slab thickness selection, elastic constant calculation, load calculations considering dead and live loads, moment determination using code coefficients, minimum steel requirements, and distribution steel spacing.
This document provides information on the design of reinforced concrete beams, including:
1. It outlines the three basic design stages: preliminary analysis and sizing, detailed analysis of reinforcement, and serviceability calculations.
2. It describes how to calculate the lever arm, depth of the neutral axis, and required area of tension and compression reinforcement for singly and doubly reinforced beams.
3. It discusses considerations for preliminary sizing of beams, including required cover, breadth, effective depth, shear stress limits, and span-depth ratios. Trial calculations are suggested to determine suitable beam dimensions.
Development Length Hook Splice Of ReinforcementsSHERAZ HAMEED
This document discusses reinforcement development length, which is the minimum length required for bond stress to develop between steel reinforcement and concrete. It provides formulas to calculate development length based on factors like bar diameter, yield strength, concrete strength, and transverse reinforcement. The development length must be sufficient to prevent bar pullout under load. Standards like ACI Code specify minimum development lengths empirically related to these factors to ensure the bond can develop adequately.
Ring or circular rafts can be used for cylindrical structures such as chimneys, silos, storage tanks, TV-towers and other structures. In this case, ring or circular raft is the best suitable foundation to the natural geometry of such structures. The design of circular rafts is quite similar to that of other rafts.
This document presents information on the design of one-way slabs. It defines one-way slabs as having a ratio of longer to shorter side of at least 2.0 and experiencing load distribution in the direction perpendicular to supports. The minimum thickness is specified in the ACI code based on span length and support conditions. Loads assigned include dead and live loads. Temperature and shrinkage reinforcement is also required perpendicular to main reinforcement to control cracking. The design procedure involves calculating minimum thickness, factored loads, moments, steel ratios, required depth and detailing of reinforcement.
This document provides guidance on designing reinforced concrete slab systems, including one-way and two-way slabs, using web-based software. It introduces common slab types, design methods, assumptions, and considerations. The document then gives step-by-step examples of designing a one-way continuous slab and a simply supported two-way slab. It demonstrates the software's input/output interface by guiding the user through the full design process for each example slab. The guidance concludes by listing additional slab design examples available on the web-based software.
This document provides details on the design of a continuous one-way reinforced concrete slab. It includes minimum thickness requirements, equations for calculating moments and shear, maximum reinforcement ratios, and minimum reinforcement ratios. An example is then provided to demonstrate the design process. The slab is designed to have a thickness of 6 inches with 0.39 in2/ft of tension reinforcement in the negative moment region and 0.33 in2/ft in the positive moment region.
Shear Strenth Of Reinforced Concrete Beams Per ACI-318-02Engr Kamran Khan
This document provides a 4 PDH course on the shear strength of reinforced concrete beams per ACI 318-02. It covers topics such as the different modes of failure for beams without shear reinforcement, the shear strength criteria, and calculations for the shear strength provided by concrete. The course content includes introductions to shear stresses in beams, Mohr's circle analysis, beam classifications, and equations for determining nominal shear strength based on the concrete strength and web reinforcement.
This document discusses the analysis and design of one-way and two-way concrete slabs. It describes how one-way slabs transfer loads in one direction while two-way slabs transfer loads in two perpendicular directions. The coefficient method is presented for analyzing bending moments in two-way slabs using moment coefficients from tables based on support conditions and span ratios. An example is provided to calculate moment coefficients and design a two-way slab using working stress and ultimate strength design methods.
The document discusses reinforced concrete slabs. It defines one-way and two-way slabs and their characteristics. One-way slabs are supported on two sides and have reinforcement in one direction, while two-way slabs are supported on all four sides and have reinforcement in both directions. The document provides steps for designing slabs, including calculating loads, moments, effective depth, and ensuring design strength is sufficient. It also discusses advantages and disadvantages of one-way and two-way slabs.
The document describes the design of a stepped footing to support a column with an unfactored load of 800 kN. A square footing with dimensions of 2.1m x 2.1m is designed with two 300mm steps. Reinforcement of #12 bars at 150mm c/c is provided. Checks are performed for bending moment, one-way shear, two-way shear, and development length which all meet code requirements. Therefore, the stepped footing design is adequate to support the given column load.
This document discusses different types of two-way slabs, including edge-supported slabs, column-supported slabs, flat plates, and waffle slabs. It provides details on when a slab is considered a two-way slab and how it is reinforced in two directions to resist bending moments in both directions. The document also discusses analysis methods for two-way slab design.
This document discusses different types of reinforced concrete slabs, including one-way slabs, two-way slabs, flat slabs, and ribbed slabs. One-way slabs are supported on two sides and bend in one direction, while two-way slabs are supported on all four sides and bend in both directions. Flat slabs do not have beams and loads are transferred directly to columns, providing a plain ceiling. Ribbed slabs contain reinforced concrete ribs spaced no more than 1 meter apart between which the slab spans.
This document 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.
This presentation summarizes the key aspects of one-way slab design:
1) One-way slabs have an aspect ratio of 2:1 or greater, where bending occurs primarily along the long axis. They can be solid, hollow, or ribbed.
2) Design and analysis treats a unit strip of the slab as a rectangular beam of unit width and the slab thickness as the depth.
3) The ACI code specifies minimum slab thickness, concrete cover, span length, bar spacing, reinforcement ratios, and other design requirements.
4) An example problem demonstrates the design process, calculating loads, moments, minimum reinforcement, and checking the proposed slab thickness.
5) One-
This document provides information on the design of reinforced concrete slabs. It discusses slab classification, analysis methods, general design guidelines, behavior of one-way and two-way slabs, continuity, and detailing requirements. Two example problems are included to illustrate the design of a simply supported one-way slab and a monolithic two-way restrained slab.
The document discusses reinforcement in two-way slabs and footing design. It describes two types of shear failure in slabs: one-way shear and two-way shear. One-way shear results in inclined cracking and pull-out of negative reinforcement from the slab. Two-way shear can result in either inclined cracking or the slab sliding down the column. The critical perimeter for two-way shear is located at d/2 from the column face, where d is the effective depth of the slab. Formulas are provided to calculate the nominal shear resistance Vn of slabs under two-way shear with negligible moment transfer.
Ch4 Bridge Floors (Steel Bridges تصميم الكباري المعدنية & Prof. Dr. Metwally ...Hossam Shafiq II
This chapter discusses bridge floors for roadway and railway bridges. It describes three main types of structural systems for roadway bridge floors: slab, beam-slab, and orthotropic plate. For railway bridges, the two main types are open timber floors and ballasted floors. The chapter then covers design considerations for allowable stresses, stringer and cross girder cross sections, and provides an example design for the floor of a roadway bridge with I-beam stringers and cross girders.
The document discusses proper detailing of reinforced concrete structures, which is essential for safety and structural performance. It provides guidelines and examples of good and bad detailing practices for common reinforced concrete elements like slabs, beams, columns, and foundations. Proper detailing is important to avoid construction errors and ensure the structural design works as intended under gravity and seismic loads.
The document describes the process used by a structural analysis program to design concrete beam flexural reinforcement according to BS 8110-97. The program calculates reinforcement required for flexure and shear. For flexural design, it determines factored moments, calculates reinforcement as a singly or doubly reinforced section, and ensures minimum reinforcement requirements are met. Design is conducted for rectangular beams and T-beams under positive and negative bending.
This document summarizes a lecture on flat slab design and analysis. It discusses key topics such as:
1. Definitions of flat slabs and their components like column strips and middle strips.
2. Methods of analyzing flat slabs including numerical methods and manual methods like the method of substitutive beams.
3. Design considerations for flat slabs including steel distribution above columns, welded mesh reinforcement, loading schemes, and punching shear design.
4. Different types of shear reinforcement that can be used at column heads like links, cages, and bent-up bars.
Prepared by madam rafia firdous. She is a lecturer and instructor in subject of Plain and Reinforcement concrete at University of South Asia LAHORE,PAKISTAN.
Design and Detailing of RC Deep beams as per IS 456-2000VVIETCIVIL
Visit : https://teacherinneed.wordpress.com/
1. DEEP BEAM DEFINITION - IS 456
2. DEEP BEAM APPLICATION
3. DEEP BEAM TYPES
4. BEHAVIOUR OF DEEP BEAMS
5. LEVER ARM
6. COMPRESSIVE FORCE PATH CONCEPT
7. ARCH AND TIE ACTION
8. DEEP BEAM BEHAVIOUR AT ULTIMATE LIMIT STATE
9. REBAR DETAILING
10. EXAMPLE 1 – SIMPLY SUPPORTED DEEP BEAM
11. EXAMPLE 2 – SIMPLY SUPPORTED DEEP BEAM; M20, FE415
12. EXAMPLE 3: FIXED ENDS AND CONTINUOUS DEEP BEAM
13. EXAMPLE 4 : FIXED ENDS AND CONTINUOUS DEEP BEAM
This document discusses the design of floor slabs including one-way spanning slabs, two-way spanning slabs, continuous slabs, cantilever slabs, and restrained slabs. It covers slab types based on span ratios, bending moment coefficients, determining design load, reinforcement requirements, shear and deflection checks, crack control, and reinforcement curtailment details for different slab conditions. The document is authored by Eng. S. Kartheepan and is related to the design of floor slabs for a civil engineering project.
Precast implementation by Elematic FinlandShridhar Rao
Why should you choose Precast construction in place of traditional Cast-in-Situ system and how Elematic can hand hold in this journey adopting Precast Technology and construction
First Single-storey Bungalow Project after 9 years since 2008.Teow Beng Hur
ONE OF THE WAY TO IMPROVE THE OUTFLOW OF CURRENCY IS THE UTILIZATION OF INDUSTRIAL BUILDING SYSTEM ( IBS ) :
- IBS is a system which suits all architectural demands. It is neither a machine nor component,
- IBS Superstructure In Malaysia 3in1 : HC PRECAST SYSTEM
- Load Bearing + Modular Shear Keys Wet Joint + Box System
This document provides guidance on designing reinforced concrete slab systems, including one-way and two-way slabs, using web-based software. It introduces common slab types, design methods, assumptions, and considerations. The document then gives step-by-step examples of designing a one-way continuous slab and a simply supported two-way slab. It demonstrates the software's input/output interface by guiding the user through the full design process for each example slab. The guidance concludes by listing additional slab design examples available on the web-based software.
This document provides details on the design of a continuous one-way reinforced concrete slab. It includes minimum thickness requirements, equations for calculating moments and shear, maximum reinforcement ratios, and minimum reinforcement ratios. An example is then provided to demonstrate the design process. The slab is designed to have a thickness of 6 inches with 0.39 in2/ft of tension reinforcement in the negative moment region and 0.33 in2/ft in the positive moment region.
Shear Strenth Of Reinforced Concrete Beams Per ACI-318-02Engr Kamran Khan
This document provides a 4 PDH course on the shear strength of reinforced concrete beams per ACI 318-02. It covers topics such as the different modes of failure for beams without shear reinforcement, the shear strength criteria, and calculations for the shear strength provided by concrete. The course content includes introductions to shear stresses in beams, Mohr's circle analysis, beam classifications, and equations for determining nominal shear strength based on the concrete strength and web reinforcement.
This document discusses the analysis and design of one-way and two-way concrete slabs. It describes how one-way slabs transfer loads in one direction while two-way slabs transfer loads in two perpendicular directions. The coefficient method is presented for analyzing bending moments in two-way slabs using moment coefficients from tables based on support conditions and span ratios. An example is provided to calculate moment coefficients and design a two-way slab using working stress and ultimate strength design methods.
The document discusses reinforced concrete slabs. It defines one-way and two-way slabs and their characteristics. One-way slabs are supported on two sides and have reinforcement in one direction, while two-way slabs are supported on all four sides and have reinforcement in both directions. The document provides steps for designing slabs, including calculating loads, moments, effective depth, and ensuring design strength is sufficient. It also discusses advantages and disadvantages of one-way and two-way slabs.
The document describes the design of a stepped footing to support a column with an unfactored load of 800 kN. A square footing with dimensions of 2.1m x 2.1m is designed with two 300mm steps. Reinforcement of #12 bars at 150mm c/c is provided. Checks are performed for bending moment, one-way shear, two-way shear, and development length which all meet code requirements. Therefore, the stepped footing design is adequate to support the given column load.
This document discusses different types of two-way slabs, including edge-supported slabs, column-supported slabs, flat plates, and waffle slabs. It provides details on when a slab is considered a two-way slab and how it is reinforced in two directions to resist bending moments in both directions. The document also discusses analysis methods for two-way slab design.
This document discusses different types of reinforced concrete slabs, including one-way slabs, two-way slabs, flat slabs, and ribbed slabs. One-way slabs are supported on two sides and bend in one direction, while two-way slabs are supported on all four sides and bend in both directions. Flat slabs do not have beams and loads are transferred directly to columns, providing a plain ceiling. Ribbed slabs contain reinforced concrete ribs spaced no more than 1 meter apart between which the slab spans.
This document 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.
This presentation summarizes the key aspects of one-way slab design:
1) One-way slabs have an aspect ratio of 2:1 or greater, where bending occurs primarily along the long axis. They can be solid, hollow, or ribbed.
2) Design and analysis treats a unit strip of the slab as a rectangular beam of unit width and the slab thickness as the depth.
3) The ACI code specifies minimum slab thickness, concrete cover, span length, bar spacing, reinforcement ratios, and other design requirements.
4) An example problem demonstrates the design process, calculating loads, moments, minimum reinforcement, and checking the proposed slab thickness.
5) One-
This document provides information on the design of reinforced concrete slabs. It discusses slab classification, analysis methods, general design guidelines, behavior of one-way and two-way slabs, continuity, and detailing requirements. Two example problems are included to illustrate the design of a simply supported one-way slab and a monolithic two-way restrained slab.
The document discusses reinforcement in two-way slabs and footing design. It describes two types of shear failure in slabs: one-way shear and two-way shear. One-way shear results in inclined cracking and pull-out of negative reinforcement from the slab. Two-way shear can result in either inclined cracking or the slab sliding down the column. The critical perimeter for two-way shear is located at d/2 from the column face, where d is the effective depth of the slab. Formulas are provided to calculate the nominal shear resistance Vn of slabs under two-way shear with negligible moment transfer.
Ch4 Bridge Floors (Steel Bridges تصميم الكباري المعدنية & Prof. Dr. Metwally ...Hossam Shafiq II
This chapter discusses bridge floors for roadway and railway bridges. It describes three main types of structural systems for roadway bridge floors: slab, beam-slab, and orthotropic plate. For railway bridges, the two main types are open timber floors and ballasted floors. The chapter then covers design considerations for allowable stresses, stringer and cross girder cross sections, and provides an example design for the floor of a roadway bridge with I-beam stringers and cross girders.
The document discusses proper detailing of reinforced concrete structures, which is essential for safety and structural performance. It provides guidelines and examples of good and bad detailing practices for common reinforced concrete elements like slabs, beams, columns, and foundations. Proper detailing is important to avoid construction errors and ensure the structural design works as intended under gravity and seismic loads.
The document describes the process used by a structural analysis program to design concrete beam flexural reinforcement according to BS 8110-97. The program calculates reinforcement required for flexure and shear. For flexural design, it determines factored moments, calculates reinforcement as a singly or doubly reinforced section, and ensures minimum reinforcement requirements are met. Design is conducted for rectangular beams and T-beams under positive and negative bending.
This document summarizes a lecture on flat slab design and analysis. It discusses key topics such as:
1. Definitions of flat slabs and their components like column strips and middle strips.
2. Methods of analyzing flat slabs including numerical methods and manual methods like the method of substitutive beams.
3. Design considerations for flat slabs including steel distribution above columns, welded mesh reinforcement, loading schemes, and punching shear design.
4. Different types of shear reinforcement that can be used at column heads like links, cages, and bent-up bars.
Prepared by madam rafia firdous. She is a lecturer and instructor in subject of Plain and Reinforcement concrete at University of South Asia LAHORE,PAKISTAN.
Design and Detailing of RC Deep beams as per IS 456-2000VVIETCIVIL
Visit : https://teacherinneed.wordpress.com/
1. DEEP BEAM DEFINITION - IS 456
2. DEEP BEAM APPLICATION
3. DEEP BEAM TYPES
4. BEHAVIOUR OF DEEP BEAMS
5. LEVER ARM
6. COMPRESSIVE FORCE PATH CONCEPT
7. ARCH AND TIE ACTION
8. DEEP BEAM BEHAVIOUR AT ULTIMATE LIMIT STATE
9. REBAR DETAILING
10. EXAMPLE 1 – SIMPLY SUPPORTED DEEP BEAM
11. EXAMPLE 2 – SIMPLY SUPPORTED DEEP BEAM; M20, FE415
12. EXAMPLE 3: FIXED ENDS AND CONTINUOUS DEEP BEAM
13. EXAMPLE 4 : FIXED ENDS AND CONTINUOUS DEEP BEAM
This document discusses the design of floor slabs including one-way spanning slabs, two-way spanning slabs, continuous slabs, cantilever slabs, and restrained slabs. It covers slab types based on span ratios, bending moment coefficients, determining design load, reinforcement requirements, shear and deflection checks, crack control, and reinforcement curtailment details for different slab conditions. The document is authored by Eng. S. Kartheepan and is related to the design of floor slabs for a civil engineering project.
Precast implementation by Elematic FinlandShridhar Rao
Why should you choose Precast construction in place of traditional Cast-in-Situ system and how Elematic can hand hold in this journey adopting Precast Technology and construction
First Single-storey Bungalow Project after 9 years since 2008.Teow Beng Hur
ONE OF THE WAY TO IMPROVE THE OUTFLOW OF CURRENCY IS THE UTILIZATION OF INDUSTRIAL BUILDING SYSTEM ( IBS ) :
- IBS is a system which suits all architectural demands. It is neither a machine nor component,
- IBS Superstructure In Malaysia 3in1 : HC PRECAST SYSTEM
- Load Bearing + Modular Shear Keys Wet Joint + Box System
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.
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.
This document discusses hollow block and ribbed slabs, which are concrete slabs reinforced with either hollow concrete blocks or concrete ribs. It outlines the benefits of hollow block slabs, including improved insulation, easier installation without formwork, and reduced weight. Various international codes have different limitations on the design of these slabs, such as the maximum distance between ribs. The document also provides pictures from construction sites and gives an overview of the design process and limitations for hollow block and ribbed slabs according to different codes like ACI, BS, and Eurocode. It concludes with a solved example problem.
The document discusses precast concrete buildings. It begins with an introduction to precast construction and its advantages over conventional construction. It then describes various precast elements like beams, columns, slabs, walls, and connections. It discusses construction methodology, design considerations, cost comparison to cast-in-situ, standards, and provides case studies of precast buildings in India and abroad.
This report compares design codes for hollow block and ribbed slabs. It includes:
- A comparison of limitations between Egyptian, British, Euro and American codes on rib spacing, slab thickness, and other parameters.
- Solved examples for one-way and two-way slabs according to different codes, finding the Egyptian code most economical.
- Analysis of using one or two cross-ribs, determining one rib at midspan is sufficient.
- Different modeling methods for the slabs in structural analysis software, with minor differences in results.
- Case studies presented for one-way, cantilever, two-way hollow block slabs, and ribbed slabs using
Diagrid Systems : Future of Tall buildings, Technical Paper by Jagmohan Garg ...Jagmohan Garg
The document discusses the DiaGrid structural system for tall buildings. A DiaGrid system uses a design of triangulated steel beams and horizontal support rings to construct large buildings. It creates a structural system of triangles that provides stability and resistance to lateral loads. Some key benefits of the DiaGrid system include column-free interior spaces, resistance to overturning forces, simpler construction, and better load redistribution compared to braced frame structures. While effective for buildings up to 70 stories, the DiaGrid system involves complicated joint connections.
The document summarizes the design of beam-and-slab systems. It describes how the one-way slab is designed as a continuous slab spanning the beam supports using moment distribution methods or a simplified coefficient method. Interior beams are designed as T-beams and edge beams as L-beams, which provide greater flexural strength than conventional beams. The beam and slab must be securely connected to transfer shear forces between them. The slab is reinforced as a one-way system and the beams are designed as simply supported beams spanning their supports.
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.
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.
Diagrid structural system strategies to reduce lateral forces on high rise bu...eSAT Publishing House
This document compares the structural performance of a 20-story building designed with a diagrid system versus a simple frame system. Analysis shows the diagrid building experiences less top displacement, inter-story drift, and shear forces compared to the simple frame building under wind and earthquake loads. The diagrid building also uses 13% less concrete and 58% less steel. Diagrid structures are more efficient at resisting lateral loads through axial forces in the diagonal members, unlike simple frames which rely on bending of vertical columns.
Bar Bending Schedule (BBS) is a chart which gives a clear picture of bar length, diameter of bar ,bar mark ,location of bar.
It allow workers to place steel properly.
This presentation summarizes the key aspects of one-way slab design. It defines one-way slabs as having an aspect ratio of 2:1 or greater, with bending primarily along the long axis. The presentation discusses the types of one-way slabs including solid, hollow, and ribbed. It also outlines the design considerations for one-way slabs according to the ACI code, including minimum thickness, reinforcement ratios, and bar spacing. An example problem demonstrates how to design a one-way slab for a given set of loading and dimensional conditions.
The superstructure of a building consists of elements above the foundation like beams, columns, lintels, roofing and flooring. Beams are horizontal members that carry loads and transfer them to columns or walls. Reinforced concrete beams are designed to resist both bending moments and shear forces from loads. There are different types of beams like simply supported, fixed, cantilever, continuous and overhanging beams which are designed based on how they are supported. Columns are vertical load bearing members that transfer loads from beams and slabs to the foundation. Common column types include long, short and intermediate columns. Lintels are short horizontal members that span small openings like doors and windows and transfer loads to masonry, steel or reinforced concrete
This document provides an overview of prefabricated modular structures. It discusses the introduction and features of prefabricated structures, comparing them to site-cast structures. It outlines the design concept, components, types of precast systems including large panel, frame, and lift-slab systems. It also discusses design considerations, equipment used, assembly process, scheduling, advantages including reduced costs and time, limitations, and concludes with examples of prefabricated hospital structures.
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.
This document provides an introduction to HVAC systems. It discusses the primary functions of HVAC systems to provide healthy and comfortable interior conditions while minimizing energy usage and emissions. It describes different types of HVAC systems including air systems, hydronic/steam systems, and unitary systems. It also discusses key HVAC components like air handling units, fans, pumps, ductwork, controls and their purposes.
1. Seismic design involves careful planning, analysis, detailing, and construction to create earthquake-resistant structures.
2. Key steps in planning include making the building symmetrical, avoiding weak stories, selecting good materials, and following code provisions.
3. Design considerations are analyzing structural elements, avoiding weak columns and strong beams, using shear walls and bracing, and designing for increased forces in soft stories. Ductility is increased through design and material choices.
1. Seismic design involves careful planning, analysis, detailing, and construction to create earthquake-resistant structures.
2. Key steps in planning include making the building symmetrical, avoiding weak stories, selecting good materials, and following code provisions.
3. Design considerations are analyzing structural elements, avoiding weak columns and strong beams, using shear walls and bracing, and designing for increased forces in soft stories. Ductility is increased through design and material choices.
1. Seismic design involves careful planning, analysis, detailing, and construction to create earthquake-resistant structures.
2. Key steps in planning include making the building symmetrical, avoiding weak stories, selecting good materials, and following code provisions.
3. Important aspects of design are analyzing structural elements to resist seismic forces, using techniques like shear walls and bracing, and ductile detailing of reinforcement.
4. Careful construction with quality materials and workmanship is also vital for seismic resistance.
- 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 sheet pile walls and braced cuts. It describes different types of sheet piles (timber, reinforced concrete, steel), their uses, and common sheet pile structures. Methods for analyzing the depth of embedment and bending moments in free cantilever sheet pile walls are presented for cases with the water table at a great depth or within the backfill. Approximate depths of embedment are provided based on relative soil density.
Pile&Wellfoundation_ManualUpdated as on 20.5.16.pdfDharmPalJangra1
This document provides guidelines for the design and construction of well and pile foundations for railway bridges in India. It covers topics such as the depth of well foundations, shapes and cross-sections of wells, allowable bearing pressures, types of pile foundations, pile spacing, and load carrying capacity of piles. The guidelines are intended to help transfer heavy bridge loads to deep soil strata in a safe and stable manner. Standards are provided for various aspects of well and pile foundation design to suit local soil and construction conditions in India.
Design of concrete structures governs the performance of concrete structures.
Well designed and detailed concrete structure will show less deterioration in comparison with poorly designed and detailed concrete, in the similar condition.
The beam-column joints are particularly prone to defective concrete, if detailing and placing of reinforcement is not done properly.
Inadequate concrete cover may lead to carbonation depth reaching up to the reinforcement, thus, increasing the risk of corrosion of the reinforcement.
Flat slabs were originally invented in the U.S. in 1906 and load tested between 1910-1920. They are reinforced concrete slabs supported by columns without beams. Flat slabs offer advantages like reduced construction costs, faster construction, and greater architectural freedom. They are classified as solid flat slab, solid flat slab with drop panels, solid flat slab with column heads, or banded flat slab. Analysis and design of flat slabs involves distributing moments from equivalent frame analysis to slab components and checking shear and punching resistance.
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.
The document defines different types of structural footings used to support columns, walls, and transmit loads to the soil. It discusses isolated, combined, cantilever, continuous, raft, and pile cap footings. It also covers footing design considerations like allowable bearing capacity, shear strength, bending moment, and reinforcement requirements. The document provides formulas and steps for calculating footing size, reinforcement, and checking design requirements.
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 factors to consider when choosing the type of foundation for a structure, including the nature of the structure, loads, soil characteristics, and cost. Shallow foundations such as footings and rafts are suitable if the soil can support the loads without excessive settlement. Deep foundations using piles or piers transmit loads to a deeper bearing layer if the top soil is weak. Floating foundations may be used if no bearing layer is found by removing and replacing soil under the structure. The document provides details on analyzing loads and designing shallow spread footings to resist shear, bond, and bending stresses.
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
Calulation of deflection and crack width according to is 456 2000Vikas Mehta
This document discusses the calculation of crack width in reinforced concrete flexural members. It provides information on:
1) Crack width is calculated to satisfy serviceability limits and is only relevant for Type 3 pre-stressed concrete members that crack under service loads.
2) Crack width depends on factors like amount of pre-stress, tensile stress in bars, concrete cover thickness, bar diameter and spacing, member depth and location of neutral axis, bond strength, and concrete tensile strength.
3) The method of calculation involves determining the shortest distance from the surface to a bar and using equations involving member depth, neutral axis depth, average strain at the surface level. Permissible crack widths are specified depending on exposure
This document summarizes design considerations for shear in reinforced concrete structures. It discusses shear strength provided by concrete alone (Vc), shear strength provided by shear reinforcement (Vs), and methods for calculating total shear strength (Vn). It also covers requirements for shear reinforcement spacing and minimum amounts. Design aids are presented for calculating shear capacity of beams, slabs, and members under combined shear and torsion.
Special moment frames are reinforced concrete frames designed to resist earthquakes through flexural, axial, and shearing actions. They have additional proportioning and detailing requirements compared to intermediate or ordinary moment frames to improve seismic resistance. This includes the strong column weak beam design where the sum of the flexural strengths of the columns at a joint must exceed 120% of the sum of the flexural strengths of the beams to ensure plastic hinges form in the beams before the columns. Proper hinge reinforcement is also required to allow hinges to undergo large rotations without losing strength.
This chapter discusses the design and analysis of retaining walls. It begins with an introduction to retaining walls, describing what they are used for and common types. It then discusses the types of retaining walls in more detail, including gravity, cantilever, counterfort, sheet pile, and others. The chapter covers design considerations such as definitions of wall parts, tentative dimensions for common wall types, and forces acting on walls such as earth pressures. It concludes with a discussion of stability considerations for external stability checks like overturning, sliding, bearing capacity, settlement, and rotational failure.
This document discusses composite construction, specifically composite steel and concrete beams. It provides definitions and examples of composite construction, explaining that it aims to make each material perform the function it is best suited for. It then describes the differences between non-composite and composite beam behavior. The document goes on to discuss elements of composite construction like decking and shear studs. It also summarizes the design process for composite beams, covering moment capacity, shear capacity, shear connector capacity, and longitudinal shear capacity calculations.
The document summarizes the design procedures for slab systems according to the ACI 318 Code, including:
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.
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.
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Reinforcedslab 100917010457-phpapp02
1. DESIGN OF REINFORCED CONCRETE SLAB
UNIT NO 3: DESIGN OF REINFORCED CONCRETE SLAB
3.1 INTRODUCTION
Reinforced concrete slabs are used in floors, roofs and walls of buildings and as the
decks of bridges. The floor system of a structure can take many forms such as in situ
solid slab, ribbed slab or pre-cast units. Slabs may span in one direction or in two
directions and they may be supported on monolithic concrete beam, steel beams, walls
or directly by the structure’s columns.
Continuous slab should in principle be designed to withstand the most unfavorable
arrangements of loads, in the same manner as beams. Because there are greater
opportunities for redistribution of loads in slabs, analysis may however often be simplified
by the use of a single load case. Bending moment coefficient based on this simplified
method are provided for slabs which span in one direction with approximately equal
spans, and also for flat slabs.
The moments in slabs spanning in two directions can also be determined using
coefficients tabulated in the code of practice, BS 8110. Slab which are not rectangular in
plan or which support an irregular loading arrangement may be analyzed by techniques
such as the yield line method or the Helliborg strip method.
Concrete slab behave primarily as flexural members and the design is similar to that for
beams, although in general it is somewhat simpler because;
1. the breadth of the slab is already fixed and a unit breadth of 1m is used in the
calculations,
2. the shear stress are usually low in a slab except when there are heavy concentrated
loads, and
3. compression reinforcement is seldom required.
3.2 LEARNING OUTCOMES
After completing the unit, students should be able to :
1. know the requirement for reinforced concrete slab design
2. design reinforced concrete slab
BPLK 66 DCB 3223
2. DESIGN OF REINFORCED CONCRETE SLAB
3.3 TYPES OF SLABS
Type of slab used in construction sectors are:
Solid slab
Flat slab
Ribbed slab
Waffle slab
Hollow block floor/slab
(a) Solid slab
(b) Flat slab
BPLK 67 DCB 3223
3. DESIGN OF REINFORCED CONCRETE SLAB
(c) Ribbed slab
(d) Waffle slab
Figure 3.1: Types of slab
Flat slab floor is a reinforced concrete slab supported directly by concrete
columns without the use of intermediary beams. The slab may be of constant
thickness throughout or in the area of the column it may be thickened as a drop
panel. The column may also be of constant section or it may be flared to form a
column head or capital. These various form of construction are illustrated in
Figure 3.2.
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4. DESIGN OF REINFORCED CONCRETE SLAB
Figure 3.2: Drop panels and column head.
The drop panels are effective in reducing the shearing stresses where the column
is liable to punch through the slab, and they also provide an increased moment of
resistance where the negative moments are greatest.
The flat slab floor has many advantages over the beam and slab floor. The
simplified formwork and the reduced storey heights make it more economical.
Windows can extend up to the underside of the slab, and there are no beams to
obstruct the light and he circulation of air. The absence of sharp corner gives
greater fire resistance as there is less danger of the concrete spalling an
exposing the reinforcement. Deflection requirements will generally govern slab
thickness which should not be less than 125 mm.
Typical ribbed and waffle slab are shown in Figure 3.1[(c), (d)]. Ribbed slabs,
which are two-way spanning and are constructed with ribs in both direction of
span. Ribbed slab floors are formed using temporary or permanent shuttering
system while the hollow block floor is generally constructed with block made of
clay tile or with concrete containing a light-weight aggregate. If the block are
suitably manufactured and have an adequate strength they can be considered to
contribute to the strength of the slab in the design calculations, but in many
designs no such allowance is made.
The principal advantage of these floors is the reduction in weight achieved by
removing part of the concrete below the neutral axis and, in the case of the hollow
block floor, replacing it with a lighter form of construction. Ribbed and hollow block
floors are economical for buildings where there are long spans, over about 5 m,
and light or moderate live loads, such as in hospital wards or apartment buildings.
They would not be suitable for structures having a heavy loading, such as
warehouses and garages.
Near to the supports the hollow blocks are stopped off and the slab is made solid.
This is done to achieve greater shear strength, and if the slab is supported by a
monolithic concrete beam the solid section acts as the flange of a T-section.
The ribs should be checked for shear at their junction with the solid slab. It is
good practice to stagger the joints of the hollow blocks in adjacent rows so that,
as they are stopped off, there is no abrupt change in cross-section extending
across the slab. The slabs are usually made solid under partitions and
concentrated loads. During construction the hollow tiles should be well soaked in
water prior to placing the concrete, otherwise shrinkage cracking of the top
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5. baypanel
DESIGN OF REINFORCED CONCRETE SLAB
concrete flange is liable to occur.
3.4 SIMPLIFIED ANALYSIS
BS 8110 permit the use of simplified load arrangement for all slabs of maximum
ultimate design load throughout all spans or panels provided that the following
condition are met;
a) in one-way slab, the area of each bay ≥ 30 m2
b) Live load, Qk ≤ 1.25 Dead load, Gk
c) Live load, Qk ≤ 5 kN/m2
excluding partitions.
If analysis is based on this singled load case, all support moments (except at a
cantilever) should be reduced by 20 per cent and span moments increased
accordingly. No further redistribution is then permitted, but special attention must
be given to cases where a span or panel is adjacent to a cantilever of significant
length. In this situation the condition where the cantilever is fully loaded and the
span unloaded must be examined to determine possible hogging moments in the
span.
To determine the value of bending moment coefficient and shear forces
coefficient, therefore very important to define the condition of panel type, location
and moment considered. Refer to BS 8110: Part 1: 1997, Cl 3.5.3.6 and 3.5.3.7
and also Table 3.14 and Table 3.15 for more information.
Figure 3.3: Slab definition
3.5 LOAD DISTRIBUTION FROM SLAB
Define the type of slab either one-way direction or two-way direction, for
determine the shape of load distribution from slab to beam.
If Iy / Ix < 2 → consider as two-way slab
Iy / Ix ≥ 2 → consider as one-way slab
where → Ix - length of shorter side
BPLK 70 DCB 3223
6. A
C D
B
lx
ly
lx
lx
/2
lx
Beam AC and BD
w = n lx
/ 3
450
C
A
D
B
E F
ly
lx
450
Beam AB and CD
w = n lx
/ 6 {3- (lx
/ ly
)2
}
DESIGN OF REINFORCED CONCRETE SLAB
Iy - length of longer side
a) One-way slab
b) Two-way slab
Figure 3.4: Load distribution of slab
BPLK 71 DCB 3223
Beam AB and CD
w = n lx / 2
7. DESIGN OF REINFORCED CONCRETE SLAB
3.6 SHEAR IN SLAB
The shear resistance of slab may be calculated by the procedures given in BS
8110, Cl.3.5.5.2. Experimental works has indicated that, compared wit beams,
shallow slab fail at slightly higher shear stresses and this is incorporated into the
values of design ultimate shear stress vc.(Refer to Table 3.9, BS 8110). The shear
stress at a section in a solid slab is given by;
v = V
b.d
where V is the shear force due to ultimate load, d is the effective depth of the slab
and b is the width of section considered (Refer to Table 3.17 and Cl. 3.5.5.2).
Calculation is usually based on strip of slab 1m wide.
The BS 8110 requires that for solid slab;
1. v < 0.8 √ fcu or 5 N/mm2
2. v < vc for a slab thickness less than 200 mm
3. if v > vc , shear reinforcement must be provided in slabs more than 200
mm thick.
If shear reinforcement is required, then nominal steel, as for beams, should be
provided when v < (vc + o.4) and ‘designed’ reinforcement provided for higher
values of v. Since shear stress in slab due to distributed loads are generally
small, shear reinforcement will seldom be required for such loads may, however,
cause more critical conditions as shown in the following sections. Practical
difficulties concerned with bending and fixing of shear reinforcement lead to the
recommendation that it should not be used in slabs which are less than 200 mm
deep.
3.6.1 PUNCHING SHEAR ANALYSIS
A concentrated load (N) on a slab causes shearing stresses on a section
around the load; this effect is referred to a punching shear. The initial
critical section for shear is shown in Figure 3.5 and the shear stress is
given by;
v = N / (Perimeter of the section x d) = N / (2a + 2b + 12d ) d
where a and b are the plan dimensions of the concentrated load. No
shear reinforcement is required if the punching shear stress, v < vc. The
value of vc in Table 3.9, BS 8110, depends on the percentage of
reinforcement 100As/bd which should be calculates as an average of a
tensile reinforcement in the two directions and should include all the
reinforcement crossing the critical section and extending a further
distance equal to at least d on either side.
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8. DESIGN OF REINFORCED CONCRETE SLAB
Check should also be undertaken to ensure that the stress v calculated
for the perimeter at the face of the loaded area is less than smaller of 0.8
√ fcu or 5 N/mm2
.
Figure 3.5 Punching shear
3.7 SPAN-EFFECTIVE DEPTH RATIOS
Excessive deflections of slab will cause damage to the ceiling, floor finishes and
other architectural details. To avoid this, limits are set on the span-depth ratios.
These limits are exactly the same as those for beams. As a slab is usually a
slender member the restrictions on the span-depth ratio become more
important and this can often control the depth of slab required. In terms of the
span-effective depth ratio the depth of the slab is given by;
minimum effective depth = span
________
basic ratio x modification factors
The modification factor is based on the area of tension steel in the shorter span
when a slab is singly reinforced at mid-span but if a slab has both top and bottom
steel at mid-span the modification factors for the areas of tension and
compression steel, as given in Tables 1.13 and 1.14, BS 8110, are used. For
convenience, the factors for tension steel have been plotted in the form of a
graph in Figure 3.6.
It can be seen from the figure that a lower service stress gives a higher
modification factor and hence a smaller depth of slab would be required. The
service stress may be reduced by providing an area of tension reinforcement
greater than that required resisting the design moment, or alternatively mild steel
reinforcement with its lower service tress may be used.
The span-depth ratios may be checked using the service stress appropriate to the
characteristic stress of the reinforcement, as given in Table 1.13, BS 8110. Thus
BPLK 73 DCB 3223
9. DESIGN OF REINFORCED CONCRETE SLAB
a service stress of 307 N/mm2
would be used when fy is 460 N/mm2
. However, if a
more accurate assessment of the limiting span-depth ratio is required the
service stress fs, can be calculated from;
fs = 2 x fy x Asreq x 1
3 x Asprov βb
where
Asreq = the area of reinforcement at mid-span
Asprov = the area of reinforcement provided at mid-span
βb = the ratio of the mid-span moments after and before any redistribution.
Figure 3.6: Modification factors for span-effective depth ratio
3.8 REINFORCEMENT DETAIL
To resist cracking of the concrete, codes of practice specify detail such as the
minimum area of reinforcement required in a section and limits to the maximum
and minimum spacing of bars. Some of these rules are as follows;
a) Minimum areas of reinforcement
Minimum area = 0.13bh / 100 for high yield steel
or
= 0.24bh / 100 for mild steel
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10. DESIGN OF REINFORCED CONCRETE SLAB
in both directions.
b) Maximum Spacing of Reinforcement
The maximum clear spacing given in Table 3.30, and Clause 3.12.11, BS 8110,
(apply to bars in beams when a maximum likely crack width of 0.3 mm is
acceptable an the cover to reinforcement does not exceed 50 mm), and are
similar to beams except that for thin slabs, or if the tensile steel percentage is
small, spacing may be increased from those given in Table 3.30, BS 8110 to a
maximum of the lesser of 3d or 750 mm.
c) Reinforcement in the flange of a T – or L-Beam
When the slab from the flange of a T or L beam the area of reinforcement in the
flange and at right angles to the beam should not be less than 0.15 percent of the
longitudinal cross-section of the flange.
d) Curtailment and anchorage of reinforcement
At a simply supported end the bars should be anchored as specified in Figure
3.7.
Figure 3.7: Anchorage at simple supported for a slab
3.9 SLAB DESIGN
3.9.1 SOLID SLABS SPANNING IN ONE DIRECTION
The slabs are design as if they consist of a series of beams of 1 m
breadth. The main steel is in the direction of the span and secondary or
distribution steel required in the transverse direction. The main steel
should from the outer layer of reinforcement to give it the maximum level
arm.
The calculations for bending reinforcement follow a similar procedure to
that used in beam design. The lever-arm curve of Figure 3.8 is used to
determine the lever arm (z) and the area of tension reinforcement is then
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11. DESIGN OF REINFORCED CONCRETE SLAB
given by;
As = Mu / 0.87 fy.z
For solid slabs spanning one way the simplified rules for curtailing bars as
shown in Figure 3.9 may be used provided the loads are substantially
uniformly distributed. With a continuous slab it is also necessary that the
spans are approximately equal the simplified single load case analysis
has been used.
The % values on the K axis mark the limit
for singly reinforced sections with moment
redistribution applied.
Figure 3.8: Lever-arm
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12. DESIGN OF REINFORCED CONCRETE SLAB
Figure 3.9: Simplified rules for curtailment of bars in slab spanning in one
direction
3.9.1.1 Simply Supported Solid Slab
The effective span of the slab is taken as the lesser of:
a) The centre-to-centre distance of the bearings, or
b) The clear distance between supports plus the effective depth of the
slab
The basic span-effective depth ratio for this type of slab is 20:1 (Refer to
Table 3.10 and Cl. 3.4.6.3 in BS 8110).
Example 3.1:
The slab is to be design to carry a live load 3.0 kN/mm2
, plus floor
finishes and ceiling load of 1.0 kN/mm2
. The characteristic
materials strength are fcu = 30 N/mm2
, fy = 460 N/mm2
. Length of
slab is 4.5 m
Solution :
Minimum effective depth, d = span / 20 x modification factor (m.f)
= 4500 / 20 m.f
= 225 / m.f
For high-yield reinforcement slab;
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13. DESIGN OF REINFORCED CONCRETE SLAB
Estimating the modification factor to be of the order of 1.3 for a
highly reinforcement slab.
Try effective depth d = 180 mm. For a mild exposure the cover =
25 mm.
Allowing, say, 5 mm as half the diameter of the reinforcing bar
overall depth of slab, h = 180 + 25 + 5 = 210 mm
self-weight of slab = 0.21 x 24 x 103
= 5.0 kN/m2
total dead load, Gk = 1.0 + 5.0 = 6.0 kN/m2
For a 1m width of slab
ultimate load = (1.4Gk + 1.6Qk) (4.5)
= (1.4 x 6.0 + 1.6 x 3.0)(4.5) = 59.4kN
M = (59.4 x 4.5)/8 = 33.4 kNm
1) Span-effective depth ratio
M = 33.4 x 106
= 1.03
bd2
1000 x 1802
From Table 3.11 BS 8110, for fs = 307 N/mm2
the span-effective
depth modification factor = 1.29. Therefore;
Allowable span / d > Actual span / d
20 x 1.29 > 4500 / 180
25.8 > 25.0
Thus d = 180 mm is adequate.
2) Bending reinforcement
K = M = 33.4 x 106
= 0.034 < 0.156
fcubd2
(1000)(1802
)(30)
z = d {0.5 + √ (0.25 – K / 0.9)}
= d {0.5 + √ ( 0.25 – 0.034 / 0.9)}
= 0.96d > 0.95d, so take z = 0.95d
BPLK 78 DCB 3223
14. DESIGN OF REINFORCED CONCRETE SLAB
As = M / 0.87fy z = 334 x 106
/(0.87 x 460 x 171) = 447 mm2
/m
Provide T10 bars at 150 mm centre, As = 523 mm2
/m
3) Shear
Shear, V = W / 2 = 59.4 / 2 = 29.07 kN
Shear stress, v = V / bd
= 29.07 x 103
/ (1000 x 180)
= 0.16 N/mm2
< 0.8 √ fcu
From Table 3.9, BS 8110,
100As /b d = 100 x 523 / 1000 x 180 = 0.29
vc = 0.51 N/mm2
, v < v c , so no shear reinforcement is
required.
4) End anchorage (Cl. 3.12.9.4, BS 8110)
v = 0.16 < < v c/2 → ok; therefore;
anchorage length > 30 mm or end bearing (support width)/3
end bearing = 230 mm
Therefore;
anchorage length = 230 / 3 = 77 mm ≥ 30 mm
→ beyond the centre line of the support.
Figure 3.10: End Anchorage
5) Distribution / Transverse Steel
BPLK 79 DCB 3223
15. DESIGN OF REINFORCED CONCRETE SLAB
From Table 3.27 BS 8110, fy = 460 N/mm2
Area of transverse high-yield reinforcement,
As min = 0.13bh/100
= 0.13 x 1000 x 210 /100
= 273 mm 2
/m
Provide T10 at 250 mm centre, As = 314 mm2
/m, top layer
6) Cracking check
The bar spacing does not exceed 750 mm or 3d and the
minimum reinforcement is less than 0.3%. (Refer Cl.
3.12.11.2.7 and Table 3.30, BS 8110).
Allowable clear spacing of bars = 3d = 3(180) = 540 mm
Actual clear spacing = 250 – 10 = 240 mm < 3d → ok
3.9.1.2 Continuous Solid Slab
For a continuous slab, bottom reinforcement is required within the span
and top reinforcement over the supports. The effective span is the
distance between the centre lines of supports. The basic span-effective
depth ratio is 26:1 (Refer to Table 3.10 and Cl 3.4.6.3).
If the simplified load arrangement for all slabs of maximum ultimate
design load throughout all spans or panels provided that the following
condition are met for the single load case analysis, bending moment an
shear forces coefficients as shown in Table 3.13, BS 8110 may be used.
Example 3.2 :
The four-span slab shown in Figure 3.11 support a live load 0f 3.0
kN/mm2
, plus floor finishes and ceiling load of 1.0 kN/mm2
. The
characteristic materials strength are fcu = 30 N/mm2
, fy = 460
N/mm2
.
BPLK 80 DCB 3223
16. DESIGN OF REINFORCED CONCRETE SLAB
Figure 3.11 Continuous slab - example
Solution :
From Table 3.10, BS 8110, basic span- effective depth ratio = 26
So depth, d = Span / 26 = 4500 / 26
= 173 mm
Try effective depth, d = 170 mm. Assume a mild exposure, cover,
c = 20 mm an diameter of bar, Ø = 10 mm
h = d + cover + Ø/2
= 170 + 20 + 5 = 195 mm, so taken h = 200 mm
Self-weight of slab = 0.2 x 24 = 4.8 kN/m2
Total dead load, Gk = 1.0 + 4.8 = 5.8 kN / m2
For 1 meter width of slab;
Ultimate load, F = (1.4gk + 1.6qk ) 4.5
= (1.4 x 5.8 + 1.6 x 3.0)(4.5)
F = 58.14 kN per metre width
1) Bending (Refer to CL 3.5.2.3, BS 8110)
Since the bay size > 30m2
, the spans are equal and qk < 1.25 gk
the moment coefficients shown in Table 3.13 Bs 8110 may be used.
Thus, assuming that the end support is simply supported, from
Table 3.13 for the first span:
M = 0.086FL = (0.086 x 58.14 )(4.5) = 22.5 kNm
K = M = 22.5 x 106
= 0.026 < 0.156
fcubd2
30(1000 )(170)2
z = d {0.5 + √(0.25 – K/0.9)}
= d {0.5 + √(0.25 – 0.026 / 0.9)}
= 0.97d > 0.95d, so take z = 0.95d
As = M / 0.87fy z = 22.5x106
/ (0.87 x 460 x 161.5)
= 348 mm2
/m
BPLK 81 DCB 3223
17. DESIGN OF REINFORCED CONCRETE SLAB
Provide T10 bars at 200 mm centre, As = 393 mm2
/m
2) Span-effective depth ratio
M = 22.5 x 106
= 0.778
bd2
1000 x1702
From Table 3.11 BS 8110, for fs = 228 N/mm2
the span-effective
depth modification factor = 1.68. Therefore;
Allowable span / d > Actual span / d
26 x 1.68 > 4500 / 170
43.68 > 26.5 → ok
Thus d = 170 mm is adequate.
Similar calculation for the support and the interior span give the
steel areas shown in Figure 3.12.
3) Distribution / Transverse Steel
From Table 3.27 BS 8110, fy = 460 N/mm2
Area of transverse high-yield reinforcement,
As min = 0.13bh/100
= 0.13 x 1000 x 200 /100
= 260 mm 2
/m
Provide T10 at 300 mm centre, As = 262 mm2
/m, top and
bottom layer
4) Shear (Refer Table 3.13 BS 8110)
Shear, V = 0.6 F = 0.6 (58.14) = 34.9 kN
Shear stress, v = V / bd
= 34.9 x 103
/ (1000 x 170)
= 0.21 N/mm2
< 0.8 √ fcu
From Table 3.9, BS 8110,
100As / bd = 100 x 393 / 1000 x 170 = 0.23
So, v c = 0.47 x (30/25)1/3
= 0.50 N/mm2
,
v < v c , so no shear reinforcement is required.
5) Cracking check
BPLK 82 DCB 3223
18. DESIGN OF REINFORCED CONCRETE SLAB
The bar spacing does not exceed 750 mm or 3d and the
minimum reinforcement is less than 0.3%. (Refer Cl.
3.12.11.2.7 and Table 3.27 BS 8110).
Allowable clear spacing of bars = 3d = 3(170) = 510 mm
Actual clear spacing = 300 – 10 = 290 mm < 3d → ok
Figure 3.12: Reinforcement detail in continuous slab
3.9.2 SOLID SLABS SPANNING IN TWO DIRECTIONS
When a slab is supported on all four of it sides it effectively spans in
both directions, and it is sometimes more economical to design the
slab on this basis. The amount of bending in each direction will depend
on the ratio of the two spans and the conditions of restraint at each
support.
If the slab is square and the restraints are similar along the four sides then
the load will span equally in both directions. If the slab is rectangular
then more than one-half of the loads will be carried in the stiffer,
shorter direction and less in the longer direction. If one span is much
longer than the other, a large proportion of the load will be carried in the
short direction and the slab may as well be designed as spanning in
only one direction.
Moments in each direction of span are generally calculated using
coefficients which are tabulated in the codes of practice, B 8110. Areas of
reinforcement to resist the moment’s are determined independently for
each direction of span. The slab is reinforced with bars in both
directions parallel to the spans with the steel for the shorter span placed
furthest from the neutral axis to give it greater effective depth.
The span-effective depth ratios are based on the shorter span and the
BPLK 83 DCB 3223
19. DESIGN OF REINFORCED CONCRETE SLAB
percentage of reinforcement in that direction.
With a uniformly distributed load the loads on the supporting beams may
generally be apportioned as shown in Figure 3.13.
Figure 3.13: Loads carried by supporting beams
Figure 3.14: Nine Types of slab panels
BPLK 84 DCB 3223
20. DESIGN OF REINFORCED CONCRETE SLAB
3.9.2.1 Simply Supported Slab Spanning In Two Directions
A slab simply supported on its four sides will deflect about both axes
under load and the corners will tend to lift and curl up from the supports,
causing torsion moments. When no provision has been made to prevent
this lifting or to resist the torsion then the moment coefficients of Table
3.14, BS 8110 may be used and the maximum moments are given by
equation 14 and 15 in BS 8110;
msx = αsx nlx
2
in direction of span lX
and
msy = αsy nlx
2
in direction of span ly
where msx and msy are the moments at mid-span on strips of unit width with
spans lx and respectively, and
n = (1.4Gk + 1.6Qk), that is, the total ultimate load per unit area
ly = the length of the longer side
lx = the length of the shorter side
The area of reinforcement in directions lx and ly respectively are;
Asx = msx / 0.87fyz per metre width
and
Asy = msy / 0.87fyz per metre width
The slab should be reinforced uniformly across the full width, in each
direction. The effective depth d used in calculating Asy should be less than
that for Asx because of the different depths of the two layers of
reinforcement.
At least 40 per cent of the mid-span reinforcement should extend to the
supports and the remaining 60 per cent should extend to within 0.1lx, or
0.1ly of the appropriate support.
Example 3.3 :
Design the reinforcement for a simply supported slab 200 mm
thick and spanning in two directions. The effective span in each
direction is 4.5 m and 6.3 m and the slab supports a live load of 10
kN/m2
. The characteristic material strengths are fcu = 30 N/mm2
and
fy = 460 N/mm2
.
Solution :
ly / lX = 6.3/4.5 = 1.4 < 2 → Two way slab
From Table 3.14, αsx = 0.099 and αsy = 0.051.
Self-weight of slab = 0.2 x 24 x 103
= 4.8 kN/m2
Ultimate load, n = 1.4Gk + 1.6Qk
BPLK 85 DCB 3223
21. DESIGN OF REINFORCED CONCRETE SLAB
n = (1.4 x 4.8) + (1.6 x10) = 22.72kN/m2
= 22.72 kN/m/m width
Short Span
1) Bending
From Table 3.4, BS 8110, mild exposure conditions,
cover, c = 25 mm. Assume Ø bar = 10mm.
dx = h – c - Ø/2 = 200 – 25 – 5 = 170 mm.
msx = αsx nlx
2
= 0.099(22.72)(4.5)2
= 45.5 kN.m/m
K = M = 45.5 x 106
= 0.052 < 0.156
fcubd2
30(1000 )(170)2
z = d { 0.5 + √ (0.25 – K/0.9)}
= d { 0.5 + √ (0.25 – 0.052/0.9)}
= 0.94d < 0.95d, so take z = 0.94d
Asx = msx / 0.87fy z = 45.5 x106
/ (0.87x 460)(0.94x170)
= 711.5 mm2
/m
Checking Asmin, from Table 3.27 BS 8110, fy = 460 N/mm2
Asmin = 0.13bh / 100
= 0.13(1000 x 200) / 100
= 260 mm2
/ m
Asx > Asmin → ok
Provide T10 bars at 100 mm centre, As = 786 mm2
/m
2) Deflection Checking
M = 45.5 x 106
= 1.57
bd2
1000 x1702
From Table 3.11 BS 8110, for fs = 221 N/mm2
the span-effective
depth modification factor = 1.41. Therefore;
Allowable span / d > Actual span / d
20 x 1.41 > 4500 / 170
28.2 > 26.5 → ok
BPLK 86 DCB 3223
22. DESIGN OF REINFORCED CONCRETE SLAB
3) Shear
Shear, V = WL / 2 = (22.72 x 4.5 ) / 2 = 51.12 kN
Shear stress, v = V / bd
= 51.12 x 103
/ (1000 x 170)
= 0.3 N/mm2
< 0.8 √ fcu
From Table 3.9, BS 8110,
100As / bd = 100 x 786 / 1000 x 170 = 0.46
So, v c = 0.63 x (30/25)1/3
= 0.67 N/mm2
,
v < v c , so no shear reinforcement is required.
Long Span
1) Bending
From Table 3.4 BS 8110, mild exposure conditions,
cover, c = 25 mm. Assume Ø bar = 10mm.
dy = h – c - Ø/2 = 200 – 25 -10 – 5 = 160 mm.
msy = αsynlx
2
= 0.051(22.72)(4.5)2
= 23.5 kNm/m
K = M = 23.5 x 106
= 0.031 < 0.156
fcubd2
30(1000 )(160)2
z = d { 0.5 + √ (0.25 – K/0.9)}
= d { 0.5 + √ (0.25 – 0.031/0.9)}
= 0.96d > 0.95d, so take z = 0.95d
Asy = msy / 0.87fy z = 23.5 x106
/ (0.87x 460)(0.95x160)
= 354 mm2
/m
Checking Asmin, from Table 3.27 BS 8110, fy = 460 N/mm2
Asmin = 0.13bh / 100
= 0.13(1000 x 200) / 100
= 260 mm2
/ m
Asx > Asmin → ok
Provide T10 bars at 200 mm centre, As = 393 mm2
/m
BPLK 87 DCB 3223
23. DESIGN OF REINFORCED CONCRETE SLAB
2) Checking for Transverse Steel
From Table 3.27, fy = 460 N/mm2
100As / bh = 100 (393) / 1000 x 200
0.19 > 0.13 (Asmin) → ok
3.9.2.2 Restrained Slab Spanning In Two Directions
When the slabs have fixity at the supports and reinforcement is added to
resist torsion and to prevent the corners of the slab from lifting then the
maximum moments per unit width are given by;
msX = βsXnlX
2
in direction of span lx
and
msy = βsynlX
2
in direction of span ly
where βsX and βSy are the moment coefficients given in Table 3.15 of BS
8110 for the specified end conditions, and n = (1.4Gk+ 1.6Qk), the total
ultimate load per unit area.
The slab is divided into middle and edge strips as shown in Figure 3.15
and reinforcement is required in the middle strips to resist msx and msy, In
the edge strips only nominal reinforcement is necessary, such that
100As/bh = 0.13 for high-yield steel or 0.24 for mild steel.
In addition, torsion reinforcement is provided at discontinuous corners and it
should;
1. consist of top and bottom mats, each having bars in both directions
of span.
2. extend from the edges a minimum distance lx / 5
3. at a corner where the slab is discontinuous in both directions have an
area of steel in each of the four layers equal to three-quarters of the
area required for the maximum mid-span moment
4. at a corner where the slab is discontinuous in one direction only, have
an area of torsion reinforcement only half of that specified in rule 3.
Torsion reinforcement is not, however, necessary at any corner where
the slab continuous in both directions.
Where ly /Ix > 2, the slabs should be designed as spanning in one direction
only.
Shear force coefficients are also given in BS 8110 for cases where torsion
corner reinforcement is provided, and these are based on a simplified
distribution of load to supporting beams which may be used in preference
to the distribution shown Figure 3.13.
BPLK 88 DCB 3223
24. DESIGN OF REINFORCED CONCRETE SLAB
Figure 3.15: Division of slabs into middle and edge strips
Example 3.4 :
The panel considered is an interior panel, as shown in Figure
3.16. The effective span in each direction is 5 m and 6 m and
the slab supports a live load of 1.5 kN/m2
. Given fcu = 30
N/mm2
, fy = 250 N/mm2
and slab thickness 150 mm. Design the
reinforcement for a continuous slab.
Figure 3.16: Continuous panel spanning in to directions
Solution :
ly / lX = 6 / 5 = 1.2 < 2 → Two way slab
Self-weight of slab = 0.15 x 24 x 103
= 3.60 kN/m2
20 mm asphalt = 0.48 kN/m2
50 mm insulting screed = 0.72 kN/m2
Ceiling finishes = 0.24 kN/m2
BPLK 89 DCB 3223
ly = 6m
lx =5m
a b
d c
25. DESIGN OF REINFORCED CONCRETE SLAB
Total dead load = 5.04 kN/m2
Ultimate load, n = 1.4Gk + 1.6Qk
n = 1.4x5.04 + 1.6x1.5 = 9.5 kN/m2
= 9.5 kN/m/m width
From Table 3.15, Case 1 applies;
+ ve moment at mid span
msx = 0.032(9.5)(5)z
= 7.6 kNm
msy = 0.024 (9.5)(5) = 5.7 kNm
- ve moment at support (cont)
a long AB & CD, msx = 0.042 (9.5)(5)2
= 10.2 kN.m
a long AD & BC, msx = 0.032 (9.5)(5)2
= 7.6 kN.m
Assume Øbar = 10 mm, and cover, c = 25 mm
dx = h - cover - Ø/2
= 150 - 25 - 10/2 = 120 mm
dy = h - cover – Ø- Ø /2
= 150 - 25 - 10 - 10/2 = 110 mm
Short Span, lx
1) At Mid-Span, msx = 7.6 kNm
K = M = 7.6 x 106
= 0.018 < 0.156
fcubd2
30(1000 )(120)2
zx = d { 0.5 + √ (0.25 – K/0.9)}
= d { 0.5 + √ (0.25 – 0.018/0.9)}
= 0.98d > 0.95d, so take z = 0.95d
Asy = msx / 0.87fy z = 7.6 x106
/ (0.87x 250)(0.95x120)
= 306.51 mm2
/mwidth
Checking Asmin, from Table 3.27 BS 8110, fy = 250 N/mm2
Asmin = 0.24bh / 100
= 0.24(1000 x 150) / 100
= 360 mm2
/ m
Asx < Asmin → so use Asmin
BPLK 90 DCB 3223
26. DESIGN OF REINFORCED CONCRETE SLAB
Provide R10 bars at 200 mm centre, As = 393 mm2
/m
2) At Support, msx = 10.2 kNm
K = M = 10.2 x 106
= 0.024 < 0.156
fcubd2
30(1000 )(120)2
zx = d { 0.5 + √ (0.25 – K/0.9)}
= d{0.5 + √ (0.25 – 0.024/0.9)}
= 0.97d > 0.95d, so take z = 0.95d
Asx = msx / 0.87fy z = 10.2 x106
/ (0.87x 250)(0.95x120)
= 411.37 mm2
/mwidth
Checking Asmin, from Table 3.27 BS 8110, fy = 250 N/mm2
Asmin = 0.24bh / 100
= 0.24(1000 x 150) / 100
= 360 mm2
/m
Asx > Asmin → ok
Provide R10 bars at 175 mm centre, As = 449 mm2
/ m
Long Span, ly
1) At Mid-Span, msy = 5.7 kNm
K = M = 5.7 x 106
= 0.016 < 0.156
fcubd2
30(1000 )(110)2
zy = d{0.5 + √(0.25 – K/0.9)}
= d{0.5 + √(0.25 – 0.016/0.9)}
= 0.98d > 0.95d, so take z = 0.95d
Asy = msy / 0.87fy z = 5.7 x106
/ (0.87x 250)(0.95x110)
= 250.78 mm2
/mwidth
Checking Asmin, from Table 3.27 BS 8110, fy = 250 N/mm2
Asmin = 0.24bh / 100
= 0.24(1000 x 150) / 100
= 360 mm2
/ m
Asy < Asmin → so use Asmin
Provide R10 bars at 200 mm centre, Asprov = 393 mm2
/m
BPLK 91 DCB 3223
27. DESIGN OF REINFORCED CONCRETE SLAB
2) At Support, msy = 7.6 kNm
K = M = 7.6 x 106
= 0.02 < 0.156
fcubd2
30(1000 )(110)2
zy = d { 0.5 + √ (0.25 – K/0.9)}
= d { 0.5 + √ (0.25 – 0.02/0.9)}
= 0.98d > 0.95d, so take z = 0.95d
Asy = msy / 0.87fy z = 7.6 x106
/ (0.87x 250)(0.95x110)
= 334.37 mm2
/mwidth
Checking Asmin, from Table 3.27 BS 8110, fy = 250 N/mm2
Asmin = 0.24bh / 100
= 0.24(1000 x 150) / 100
= 360 mm2
/m
Asy < Asmin → so use Asmin
Provide R10 bars at 200 mm centre, Asprov = 393 mm2
/ m
→Torsion reinforcement is not necessary because the slab is
interior panel.
→Edge strip, provide Asmin (R10 -200mm c/c).
Shear Checking (Critical at Support)
Normally shear reinforcement should not be used in slabs < 200 mm
deep.
From Table 3.16, βvx = 0.39, βvy = 0.33
Vvx = βvx.n.lx
= 0.39(9.5)(5) = 18.5 kN/m width
Vvx = βvy.n.lx
= 0.33(9.5)(5) = 15.7 kN/m width
Shear stress, v = Vmax / bd
= 18.5 x 103
/ (1000 x 120)
= 0.15 N/mm2
< 0.8 √ fcu
From Table 3.9, BS 8110,
100As / bd = 100 x 449 / 1000 x 120 = 0.374
BPLK 92 DCB 3223
28. DESIGN OF REINFORCED CONCRETE SLAB
So, v c = 0.6 x (30/25)1/3
= 0.64 N/mm2
,
v < v c , so no shear reinforcement is required.
Deflection Checking (Critical at Mi-span), Msx = 7.6 kN.m
M = 7.6 x 106
= 0.53
bd2
1000 x1202
From Table 3.11 BS 8110, for fs = 139 N/mm2
the span-effective
depth modification factor = 2.0. Therefore;
Allowable span / d > Actual span / d
26 x 2 > 4500 / 120
52 > 37.5 → ok
Cracking Checking (Cl 3.12.11.2.7)
The bar spacing does not exceed 750 mm or 3d and the
minimum reinforcement is less than 0.3%. (Refer Cl. 3.12.11.2.7
and Table 3.27 BS 8110).
Allowable clear spacing of bars = 3d = 3(120) = 360 mm
Actual clear spacing = 200 – 10 = 190 mm < 3d → ok
h = 150 mm < 250 mm (for Grade 30) →therefore no further
checks are required.
3.11 SUMMARY
In this unit we have studied method for reinforced concrete slab design. Summary of
reinforced concrete slab design are shown in Figure 3.17 below.
BPLK 93 DCB 3223
Decide concrete grade, concrete cover, fire
resistance and durability
Estimate slab thickness for continuous, L/d = 30
or for simply supported, L/d = 24, where L is
shorter span of the slab.
Load calculation and estimation
UBBL: 1984 or BS 6339:1984
Structural analysis using Table 3.15 and 3.16, BS
8110: Part 1: 1985
29. DESIGN OF REINFORCED CONCRETE SLAB
Figure 3.17: Flowchart for slab design
3.12 REFERENCES
1. W.H.Mosley, J.H. Bungery & R. Husle (1999), Reinforced Concrete Design (5th
Edition) : Palgrave.
2. Reinforced Concrete Modul, (1st
Edition). USM.
3. BS 8110, Part 1: 1985, The Structural Use of Concrete. Code of Practice for
Design and Construction.
BPLK 94 DCB 3223
Reinforcement deign
Check shear
Check for serviceability limit state