This document provides an overview of foundation design, including:
1) It defines the two major requirements of foundation design as sustaining applied loads without exceeding soil bearing capacity and maintaining uniform settlement within tolerable limits.
2) It differentiates between shallow and deep foundations, with shallow foundations including isolated, combined, strap, and strip footings and deep foundations including pile foundations.
3) It explains considerations for foundation design such as minimum depth, thickness, and determining bending moments and soil bearing capacity.
This document discusses the design of compression members subjected to axial load and biaxial bending. It introduces the concept of biaxial eccentricities and explains that columns should be designed considering possible eccentricities in two axes. The document outlines the method suggested by IS 456-2000, which is based on Breslar's load contour approach. It relates the parameter αn to the ratio of Pu/Puz. Finally, it provides a step-by-step process for designing the column section, which involves determining uniaxial moment capacities, computing permissible moment values from charts, and revising the section if needed. It also briefly mentions the simplified method according to BS8110.
This document describes the design of a pile cap by a group of civil engineering students. It defines a pile cap as a concrete mat that rests on piles driven into soft ground to provide a stable foundation. It then provides two examples of pile cap design, showing dimensions, load calculations, reinforcement requirements and construction details. The document concludes that a pile cap distributes a building's load to piles to form a stable foundation on unstable soil. It acknowledges the guidance of professors in completing this project.
This document presents an example of analysis design of slab using ETABS. This example examines a simple single story building, which is regular in plan and elevation. It is examining and compares the calculated ultimate moment from CSI ETABS & SAFE with hand calculation. Moment coefficients were used to calculate the ultimate moment. However it is good practice that such hand analysis methods are used to verify the output of more sophisticated methods.
Also, this document contains simple procedure (step-by-step) of how to design solid slab according to Eurocode 2.The process of designing elements will not be revolutionised as a result of using Eurocode 2. Due to time constraints and knowledge, I may not be able to address the whole issues.
Design of steel structure as per is 800(2007)ahsanrabbani
It does not offer resistance against rotation and also termed as a hinged or pinned connections.
It transfers only axial or shear forces and it is not designed for moment
It is generally connected by single bolt/rivet and therefore full rotation is allowed
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.
The document discusses the design of footings for structures. It begins by explaining that footings are needed to transfer structural loads from members made of materials like steel and concrete to the underlying soil. It then describes different types of shallow and deep foundations, including spread, strap, combined, and raft footings. The document provides details on designing isolated and combined footings to resist vertical loads and moments based on provisions in IS 456. It also discusses wall footings and combined footings that support multiple columns. In summary, the document covers the purpose of footings, various footing types, and design of isolated and combined footings.
The Manual explains the concept of transferring the load from the super structure up to the soil throughout Piles, which has a capacity of (End bearing, and Skin friction). It illustrates the steps needed to produce a full and safe foundation for your Super Structure.
The document discusses the design of slender columns. It defines a slender column as having a slenderness ratio (length to least lateral dimension) greater than 12. Slender columns experience appreciable lateral deflection even under axial loads alone. The design of slender columns can be done using three methods - the strength reduction coefficient method, additional moment method, or moment magnification method. The document outlines the step-by-step procedure for designing a slender column using the additional moment method, which involves determining the effective length, initial moments, additional moments, total moments accounting for a reduction coefficient, and redesigning the column for combined axial load and bending.
This document discusses the design of compression members subjected to axial load and biaxial bending. It introduces the concept of biaxial eccentricities and explains that columns should be designed considering possible eccentricities in two axes. The document outlines the method suggested by IS 456-2000, which is based on Breslar's load contour approach. It relates the parameter αn to the ratio of Pu/Puz. Finally, it provides a step-by-step process for designing the column section, which involves determining uniaxial moment capacities, computing permissible moment values from charts, and revising the section if needed. It also briefly mentions the simplified method according to BS8110.
This document describes the design of a pile cap by a group of civil engineering students. It defines a pile cap as a concrete mat that rests on piles driven into soft ground to provide a stable foundation. It then provides two examples of pile cap design, showing dimensions, load calculations, reinforcement requirements and construction details. The document concludes that a pile cap distributes a building's load to piles to form a stable foundation on unstable soil. It acknowledges the guidance of professors in completing this project.
This document presents an example of analysis design of slab using ETABS. This example examines a simple single story building, which is regular in plan and elevation. It is examining and compares the calculated ultimate moment from CSI ETABS & SAFE with hand calculation. Moment coefficients were used to calculate the ultimate moment. However it is good practice that such hand analysis methods are used to verify the output of more sophisticated methods.
Also, this document contains simple procedure (step-by-step) of how to design solid slab according to Eurocode 2.The process of designing elements will not be revolutionised as a result of using Eurocode 2. Due to time constraints and knowledge, I may not be able to address the whole issues.
Design of steel structure as per is 800(2007)ahsanrabbani
It does not offer resistance against rotation and also termed as a hinged or pinned connections.
It transfers only axial or shear forces and it is not designed for moment
It is generally connected by single bolt/rivet and therefore full rotation is allowed
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.
The document discusses the design of footings for structures. It begins by explaining that footings are needed to transfer structural loads from members made of materials like steel and concrete to the underlying soil. It then describes different types of shallow and deep foundations, including spread, strap, combined, and raft footings. The document provides details on designing isolated and combined footings to resist vertical loads and moments based on provisions in IS 456. It also discusses wall footings and combined footings that support multiple columns. In summary, the document covers the purpose of footings, various footing types, and design of isolated and combined footings.
The Manual explains the concept of transferring the load from the super structure up to the soil throughout Piles, which has a capacity of (End bearing, and Skin friction). It illustrates the steps needed to produce a full and safe foundation for your Super Structure.
The document discusses the design of slender columns. It defines a slender column as having a slenderness ratio (length to least lateral dimension) greater than 12. Slender columns experience appreciable lateral deflection even under axial loads alone. The design of slender columns can be done using three methods - the strength reduction coefficient method, additional moment method, or moment magnification method. The document outlines the step-by-step procedure for designing a slender column using the additional moment method, which involves determining the effective length, initial moments, additional moments, total moments accounting for a reduction coefficient, and redesigning the column for combined axial load and bending.
ETABS is structural analysis software used to analyze and design buildings. It was developed in 1975 by students and later released commercially in 1985 by Computers and Structures Inc. The Burj Khalifa in Dubai was one of the first major projects analyzed using ETABS.
To model a structure in ETABS, materials like concrete and steel must first be defined along with their properties. Frame sections for beams, columns, walls and slabs are then created. The grid is drawn representing the building plan. Beams, columns, walls and slabs can then be drawn by connecting nodes on the grid. Modeling tools allow modifying the structural model by merging joints, aligning elements, and editing frames.
This document provides an overview of design in reinforced concrete according to BS 8110. It discusses the basic materials used - concrete and steel reinforcement - and their properties. It describes two limit states for design: ultimate limit state considering failure, and serviceability limit state considering deflection and cracking. Key aspects of beam design are summarized, including types of beams, design for bending and shear resistance, and limiting deflection. Reinforcement detailing rules are also briefly covered.
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 will help you learn an introductory part and some detailed information on Shallow Foundations. As I am presenting this document to you I wish you all a Happy learning arena. It is highly recommended for students taking a bachelor degree in Civil Engineering, also it is a good document for students who are doing final touches for their examinations.
Peer review presentation for the strut and tie method as an analysis and design approach for the mat on piles foundations of the primary separation cell (vessel).
Diaphragm wall: Construction and DesignUmer Farooq
The document discusses diaphragm walls, which are concrete or reinforced concrete walls constructed below ground using a slurry-supported trench method. Diaphragm walls can reach depths of 150 meters and widths of 0.5-1.5 meters. They are constructed using tremie installation or pre-cast concrete panels. Diaphragm walls are suitable for urban construction due to their quiet installation and lack of vibration. The document discusses different types of diaphragm walls based on materials and functions, and provides details on their design, construction process, and material requirements.
This document discusses the design of biaxially loaded columns. It defines a biaxially loaded column as one where axial load acts with eccentricities about both principal axes, causing bending in two directions. Several methods for analyzing and designing biaxially loaded columns are presented, including the load contour method, reciprocal load method, strain compatibility method, and equivalent eccentricity method. An example problem demonstrates using the reciprocal load method to check the adequacy of a trial reinforced concrete column design subjected to biaxial bending.
This document provides a tutorial for modeling and analyzing a G+10 reinforced concrete building using the structural analysis software ETABS. It outlines the step-by-step process for creating an ETABS model, including defining materials, sections, geometry, loads, supports, and running the analysis. It also describes how to display and interpret the results tabularly and graphically. The tutorial uses the architectural plans and specifications of the example G+10 building to demonstrate modeling the building, assigning properties, meshing, applying loads, and checking the model before running the analysis in ETABS.
The document provides information on constructing interaction diagrams for reinforced concrete columns. It defines an interaction diagram as a graph showing the relationship between axial load (Pu) and bending moment (Mu) for different failure modes of a column section. The document outlines the design procedure for constructing interaction diagrams, including considering pure axial load, axial load with uniaxial bending, and axial load with biaxial bending. An example is provided to demonstrate constructing the interaction diagram for a given reinforced concrete column cross-section.
The document discusses the basics of foundation design. It defines a foundation as the part of a structure that interfaces with the soil or rock below to transfer loads without overstressing the subsurface materials. Foundations must be properly located, stable, and prevent excessive settlement. Shallow foundations like pad, strip, and raft foundations transmit loads to adjacent soil, while deep foundations like piles, piers, and caissons transfer loads to deeper soil layers or rock. The document also provides details on pad footing design.
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.
This document summarizes the key aspects of box culvert design and analysis. Box culverts consist of horizontal and vertical slabs built monolithically, and are used for bridges with limited stream flows and high embankments up to spans of 4 meters. They are economical due to their rigidity and do not require separate foundations. Design loads include concentrated wheel loads, uniform loads from embankments and decks, sidewall weights, water pressure when full, earth pressures, and lateral loads. The culvert is analyzed for moments, shears, and thrusts using classical methods to determine force effects from these various loading conditions.
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 design recommendations for an isolated square footing foundation, including:
- The allowable bearing capacity of the soil is 314 kN/m^2 at a minimum depth of 2 meters.
- For a given service load of 1230.3 kN dead load and 210.6 kN live load, the required base area is calculated as 5.18 m^2 and the footing size is determined to be 2.3x2.3 meters.
- The required thickness is determined to be 500 mm based on checks for one-way shear, two-way punching shear, flexure in the long direction, and flexure in the short direction. Steel reinforcement of 12 bars of
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
Because of torsion, the beam fails in diagonal tension forming the spiral cracks around the beam. Warping of the section does not allow a plane section to remain as plane after twisting. Clause 41 of IS 456:2000 provides the provisions for
the design of torsional reinforcements. The design rules for torsion are based on the equivalent moment.
Bearing capacity of shallow foundations by abhishek sharma ABHISHEK SHARMA
elements you should know about bearing capacity of shallow foundations are included in it. various indian standards are also used. Bearing capacity theories by various researchers are also included. numericals from GATE CE and ESE CE are also included.
The document provides a summary of modeling and analyzing slabs in ETABS, including:
1) Common assumptions made in slab modeling such as element type, meshing, shape, and acceptable error.
2) Steps for initial analysis including sketching expected results and comparing total loads.
3) Formulas and coefficients for calculating maximum bending moments in one-way and two-way slabs.
4) A process for designing solid slabs according to Eurocode 2 involving determining reinforcement ratios and areas.
The document appears to be technical specifications or standards for structural design supplied by Apple Supply Bureau under a licensing agreement. It includes repetitive information about the license date and document number.
The document discusses recommendations for improving the earthquake resistance of multistory reinforced concrete buildings based on deficiencies observed in past earthquakes. Key recommendations include:
1) Structural engineers and architects should be familiar with relevant seismic codes and consider soil conditions, foundation type, and structural system to avoid irregularities.
2) Soft first stories created by open ground floors or mid-height floors should be strengthened to avoid collapse due to stress concentration.
3) Floating columns and other discontinuities should be avoided to prevent large overturning forces.
4) Inertial forces from heavy rooftop tanks should be considered in design.
This document is a seminar report on foundations and their types. It discusses shallow foundations like isolated, wall, combined, and strap footings as well as raft foundations. It also discusses deep foundations like pile foundations. Pile foundations transfer loads through skin friction and end bearing. Piles can be friction piles that transfer load through skin friction or end bearing piles that transfer load through end bearing. The report provides details on pile foundation classification and properties that affect foundation selection like soil bearing capacity, properties, and distribution of base pressure. It aims to study different foundation types and their uses based on soil and structural load conditions.
ETABS is structural analysis software used to analyze and design buildings. It was developed in 1975 by students and later released commercially in 1985 by Computers and Structures Inc. The Burj Khalifa in Dubai was one of the first major projects analyzed using ETABS.
To model a structure in ETABS, materials like concrete and steel must first be defined along with their properties. Frame sections for beams, columns, walls and slabs are then created. The grid is drawn representing the building plan. Beams, columns, walls and slabs can then be drawn by connecting nodes on the grid. Modeling tools allow modifying the structural model by merging joints, aligning elements, and editing frames.
This document provides an overview of design in reinforced concrete according to BS 8110. It discusses the basic materials used - concrete and steel reinforcement - and their properties. It describes two limit states for design: ultimate limit state considering failure, and serviceability limit state considering deflection and cracking. Key aspects of beam design are summarized, including types of beams, design for bending and shear resistance, and limiting deflection. Reinforcement detailing rules are also briefly covered.
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 will help you learn an introductory part and some detailed information on Shallow Foundations. As I am presenting this document to you I wish you all a Happy learning arena. It is highly recommended for students taking a bachelor degree in Civil Engineering, also it is a good document for students who are doing final touches for their examinations.
Peer review presentation for the strut and tie method as an analysis and design approach for the mat on piles foundations of the primary separation cell (vessel).
Diaphragm wall: Construction and DesignUmer Farooq
The document discusses diaphragm walls, which are concrete or reinforced concrete walls constructed below ground using a slurry-supported trench method. Diaphragm walls can reach depths of 150 meters and widths of 0.5-1.5 meters. They are constructed using tremie installation or pre-cast concrete panels. Diaphragm walls are suitable for urban construction due to their quiet installation and lack of vibration. The document discusses different types of diaphragm walls based on materials and functions, and provides details on their design, construction process, and material requirements.
This document discusses the design of biaxially loaded columns. It defines a biaxially loaded column as one where axial load acts with eccentricities about both principal axes, causing bending in two directions. Several methods for analyzing and designing biaxially loaded columns are presented, including the load contour method, reciprocal load method, strain compatibility method, and equivalent eccentricity method. An example problem demonstrates using the reciprocal load method to check the adequacy of a trial reinforced concrete column design subjected to biaxial bending.
This document provides a tutorial for modeling and analyzing a G+10 reinforced concrete building using the structural analysis software ETABS. It outlines the step-by-step process for creating an ETABS model, including defining materials, sections, geometry, loads, supports, and running the analysis. It also describes how to display and interpret the results tabularly and graphically. The tutorial uses the architectural plans and specifications of the example G+10 building to demonstrate modeling the building, assigning properties, meshing, applying loads, and checking the model before running the analysis in ETABS.
The document provides information on constructing interaction diagrams for reinforced concrete columns. It defines an interaction diagram as a graph showing the relationship between axial load (Pu) and bending moment (Mu) for different failure modes of a column section. The document outlines the design procedure for constructing interaction diagrams, including considering pure axial load, axial load with uniaxial bending, and axial load with biaxial bending. An example is provided to demonstrate constructing the interaction diagram for a given reinforced concrete column cross-section.
The document discusses the basics of foundation design. It defines a foundation as the part of a structure that interfaces with the soil or rock below to transfer loads without overstressing the subsurface materials. Foundations must be properly located, stable, and prevent excessive settlement. Shallow foundations like pad, strip, and raft foundations transmit loads to adjacent soil, while deep foundations like piles, piers, and caissons transfer loads to deeper soil layers or rock. The document also provides details on pad footing design.
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.
This document summarizes the key aspects of box culvert design and analysis. Box culverts consist of horizontal and vertical slabs built monolithically, and are used for bridges with limited stream flows and high embankments up to spans of 4 meters. They are economical due to their rigidity and do not require separate foundations. Design loads include concentrated wheel loads, uniform loads from embankments and decks, sidewall weights, water pressure when full, earth pressures, and lateral loads. The culvert is analyzed for moments, shears, and thrusts using classical methods to determine force effects from these various loading conditions.
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 design recommendations for an isolated square footing foundation, including:
- The allowable bearing capacity of the soil is 314 kN/m^2 at a minimum depth of 2 meters.
- For a given service load of 1230.3 kN dead load and 210.6 kN live load, the required base area is calculated as 5.18 m^2 and the footing size is determined to be 2.3x2.3 meters.
- The required thickness is determined to be 500 mm based on checks for one-way shear, two-way punching shear, flexure in the long direction, and flexure in the short direction. Steel reinforcement of 12 bars of
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
Because of torsion, the beam fails in diagonal tension forming the spiral cracks around the beam. Warping of the section does not allow a plane section to remain as plane after twisting. Clause 41 of IS 456:2000 provides the provisions for
the design of torsional reinforcements. The design rules for torsion are based on the equivalent moment.
Bearing capacity of shallow foundations by abhishek sharma ABHISHEK SHARMA
elements you should know about bearing capacity of shallow foundations are included in it. various indian standards are also used. Bearing capacity theories by various researchers are also included. numericals from GATE CE and ESE CE are also included.
The document provides a summary of modeling and analyzing slabs in ETABS, including:
1) Common assumptions made in slab modeling such as element type, meshing, shape, and acceptable error.
2) Steps for initial analysis including sketching expected results and comparing total loads.
3) Formulas and coefficients for calculating maximum bending moments in one-way and two-way slabs.
4) A process for designing solid slabs according to Eurocode 2 involving determining reinforcement ratios and areas.
The document appears to be technical specifications or standards for structural design supplied by Apple Supply Bureau under a licensing agreement. It includes repetitive information about the license date and document number.
The document discusses recommendations for improving the earthquake resistance of multistory reinforced concrete buildings based on deficiencies observed in past earthquakes. Key recommendations include:
1) Structural engineers and architects should be familiar with relevant seismic codes and consider soil conditions, foundation type, and structural system to avoid irregularities.
2) Soft first stories created by open ground floors or mid-height floors should be strengthened to avoid collapse due to stress concentration.
3) Floating columns and other discontinuities should be avoided to prevent large overturning forces.
4) Inertial forces from heavy rooftop tanks should be considered in design.
This document is a seminar report on foundations and their types. It discusses shallow foundations like isolated, wall, combined, and strap footings as well as raft foundations. It also discusses deep foundations like pile foundations. Pile foundations transfer loads through skin friction and end bearing. Piles can be friction piles that transfer load through skin friction or end bearing piles that transfer load through end bearing. The report provides details on pile foundation classification and properties that affect foundation selection like soil bearing capacity, properties, and distribution of base pressure. It aims to study different foundation types and their uses based on soil and structural load conditions.
The document provides recommendations for safe design and construction of multistorey reinforced concrete buildings based on lessons learned from past earthquakes. Key contributing factors that led to poor performance of buildings during earthquakes are identified and recommendations are provided to address each factor. The main factors discussed are: ignorance of earthquake resistant design codes, soft base soil, soft first stories, structural irregularities, heavy rooftop tanks, lack of seismic design, improper reinforcement detailing, short columns, torsional failures, and pounding between adjacent buildings. Adhering to Indian design codes and accounting for all seismic forces is emphasized.
تقرير فني -تدعيم المبنى مع الرسوم ضد الزلازل.docxAdnan Lazem
This document provides an introduction to seismic design of buildings. It discusses key structural actions like bending moments, shear forces, and ductile behavior that allow structures to deform without losing strength. Response spectra are used to determine design seismic actions based on a structure's dynamic properties and site conditions. Ductile design allows structures to withstand major earthquakes through controlled cracking and yielding. Higher modes of vibration and P-delta effects are also considered in design.
Earthquakes effects on reinforced concrete buildingsAnoop Shrestha
Reinforced concrete buildings have become common in Nepal, particularly in urban areas. They consist of concrete reinforced with steel bars. During earthquakes, inertia forces develop at each floor level and accumulate downwards, resulting in higher forces at lower stories. Floor slabs are rigid elements that bend with beams but keep columns at the same level moving together. Masonry infill walls between columns and slabs resist horizontal movement but can crack under severe shaking. Proper design requires reinforcement on all faces of beams and columns to resist bending moment reversals from earthquakes. Columns must be stronger than beams, and foundations stronger than columns, to ensure the building can deform without collapse.
The document provides details about the Structural Design and Drawing course CE8703 taught at Vivekanandha College of Technology for Women. It includes the course objectives, units covered, outcomes, design and drawing exercises, textbooks and code books referenced. The key topics covered in the course are design and drawing of retaining walls, flat slabs, bridges, liquid storage structures, industrial structures, girders and connections. The course aims to provide students with knowledge of structural engineering design principles and skills to design and draw various reinforced concrete and steel structures.
The document discusses various earthquake resistant construction details for building foundations, soil stabilization, retaining walls, tanks, and isolating structures. It provides information on different types of foundations like stone masonry, brick masonry, and concrete block masonry foundations. It also describes methods for soil stabilization including dynamic compaction, vibro compaction, pressure grouting, and surcharging. Details of wood framed walls and connections between foundations and superstructures are presented.
manual pile, practice installation with different methodvalter gentile
The document provides a quality control manual for bridge foundations in Myanmar. It was developed as part of a 3-year project between 2016-2019 between the Myanmar Ministry of Construction and the Japan International Cooperation Agency. The manual includes sections on pile foundations, surveys for bridge foundations, and quality control procedures for precast and cast-in-place pile construction. It aims to improve quality and safety in the construction of bridges and concrete structures in Myanmar.
IRJET-Soil-Structure Effect of Multideck R.C.C. StructuresIRJET Journal
1. The document discusses the soil-structure interaction effects on multideck reinforced concrete structures. It models the soil as springs to capture the flexibility of the soil-foundation system and how it impacts the structural response.
2. Static and response spectrum analyses are performed on a 10-story building model considering bare frame, infill frame, and shear wall conditions. The building is analyzed considering soft soil conditions.
3. The results show that considering soil-structure interaction through flexible soil springs leads to reduced structural demands like base shear and displacements compared to fixed-base analysis. The presence of infill and shear walls further reduces the response.
Seismic performance of friction pendulum bearing by considering storey drift ...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
engineering structural details , details of lateral loadsmohammadzunnoorain
This document provides an overview of lateral load resisting systems for multi-storey buildings. It discusses traditional load resisting components like masonry walls and how modern buildings rely more on structural systems. Frame structures, shear wall structures, and braced frame systems are the main lateral load resisting structural systems described. Concentrically braced frames, eccentrically braced frames, and buckling restrained braced frames are the different types of braced frame systems explained in detail, along with their behavior and energy dissipation capabilities. Observations from the Christchurch earthquake on the performance of eccentrically braced frames in selected buildings are also summarized.
engineering structural details , details of lateral loadsmohammadzunnoorain
This document provides an overview of lateral load resisting systems for multi-storey buildings. It discusses traditional load resisting components like masonry walls and how modern buildings rely more on structural systems. Frame structures, shear wall structures, and braced frame systems are the main lateral load resisting structural systems described. Concentrically braced frames, eccentrically braced frames, and buckling restrained braced frames are the different types of braced frame systems explained in detail, along with their behavior and energy dissipation capabilities. Observations from the Christchurch earthquake on the performance of eccentrically braced frames in selected buildings are also summarized.
A foundation is the lowest part of the building structure. It is the engineering field of study devoted to the design of those structures which support other structures, most typically buildings, bridges or transportation infrastructure. It is at the periphery of Civil, Structural and Geo-technical Engineering disciplines and has distinct focus on soil-structure interaction.
This document provides an introduction to reinforced concrete, including:
- Concrete is a mixture of cement, sand and aggregate that gains strength through chemical bonding when water is added. Reinforcing concrete with steel overcomes its weakness in tension.
- The history of reinforced concrete dates back to 1855 when it was first used in a boat. Later developments included its use in buildings in the 1860s and the first theory published in 1886.
- Structures must be designed to safely carry all loads that will act on it over its lifetime, including dead loads from structural elements, live loads from occupants/contents, and loads from wind, earthquakes, etc.
- The properties and classification of concrete are discussed, noting
This document provides an introduction to reinforced concrete. It defines concrete, reinforced concrete, and prestressed concrete. It discusses the mechanical properties of concrete and steel. It also covers the different types of loads that act on structures, including dead loads, live loads, wind loads, and earthquake loads. The document emphasizes that structures must be designed to carry all anticipated loads throughout their design life while maintaining adequate strength, serviceability, and safety with consideration for uncertainties in analysis, design, construction, and loading.
This document provides an introduction to reinforced concrete, including:
- Concrete is a mixture of cement, sand and aggregate that gains strength through chemical bonding when water is added. Reinforcing concrete with steel overcomes its weakness in tension.
- The history of reinforced concrete dates back to 1855 when it was first used in a boat. Later developments included its use in buildings in the 1860s and the first theory published in 1886.
- Structures must be designed to safely carry all anticipated loads, including dead loads from structural elements, live loads from occupants/contents, and environmental loads like wind and earthquakes.
- Reinforced concrete structures form a monolithic three-dimensional system. For analysis, floors and
Reinforced Concrete (RC) design is the process of planning and specifying the construction of structures or components using reinforced concrete. Reinforced concrete is a composite material made up of concrete (a mixture of cement, water, and aggregates) and reinforcing steel bars or mesh, which enhances its strength and durability. RCC is commonly used in the construction of buildings, bridges, dams, highways, and various other infrastructure projects due to its versatility and strength.
It's important to note that RCC design can be quite complex and should be carried out by experienced structural engineers who have a deep understanding of the principles, codes, and standards related to reinforced concrete design. Additionally, local building authorities and regulations must be followed to ensure the safety and compliance of the structure.
Here are the key steps involved in RCC design:
Structural Analysis: The first step in RCC design is to analyze the structural requirements of the project. This involves determining the loads that the structure will need to support, such as dead loads (permanent loads like the weight of the structure itself) and live loads (variable loads like people, furniture, and equipment). Structural analysis helps in understanding the internal forces and moments acting on the structure.
Material Properties: Understanding the properties of the materials used in RCC is crucial. This includes knowledge of concrete mix design (proportions of cement, water, aggregates, and admixtures), as well as the properties of reinforcing steel (yield strength, tensile strength, etc.).
Design Codes and Standards: RCC design must adhere to local building codes and standards, which dictate safety and design criteria. These standards may vary by region or country, so it's important to consult the relevant codes for your project.
Structural Design: The structural design phase involves selecting appropriate dimensions for the structural elements (beams, columns, slabs, etc.) to withstand the anticipated loads. This involves calculations and considerations for factors like safety, serviceability, and economy.
Reinforcement Design: Once the structural elements are sized, the design of the reinforcement (rebar or mesh) is carried out. This includes determining the quantity, size, spacing, and placement of reinforcement to ensure the concrete can handle the expected tensile forces.
Detailing: Detailed drawings and specifications are created, specifying all the design details, including reinforcement layouts, concrete cover, joint locations, and more. Proper detailing is essential for construction contractors to follow the design accurately.
After construction, proper maintenance is essential to ensure the longevity and safety of the structure. This includes routine inspections, repairs, and protection against environmental factors like corrosion.
Quality control measures, such as testing concrete and inspecting reinforcement
This document discusses advanced concepts in plain, reinforced, and prestressed concrete. It begins by defining concrete as a mixture of cement, sand, and aggregate bound by water. While concrete has good compressive strength, it is weak in tension. Reinforced concrete overcomes this by adding steel bars for tension resistance. The document then discusses prestressed concrete, the history of reinforced concrete, types of loads on structures, and mechanical properties of concrete. It emphasizes the importance of serviceability, strength, safety, and statistical approaches to safety margins in structural design.
This document provides a student guide to pile foundation design. It begins with an introduction to pile foundations, including their purpose and various classifications. Piles can be classified based on how they transmit loads, their material type, and their installation method. Common materials are timber, steel, and concrete. Piles are either driven into the ground or bored. Later chapters will cover topics like load distribution, single pile design, pile group design, installation methods, and testing. The guide is intended to simplify complex pile foundation texts for undergraduate students.
Comparative Study of RC Structures with Different Types of Infill Walls with ...IRJET Journal
This document presents a comparative study of RC structures with different types of infill walls, including conventional bricks, cement concrete blocks, hollow blocks, and lightweight bricks. Linear static analysis, nonlinear static pushover analysis, and soil-structure interaction analysis were performed to understand the effect of earthquake loading. The results, such as base shear, natural period, displacement, and pushover curves are compared to determine the most suitable infill material for seismic-prone zones. The analysis found that structures with lightweight brick infill walls performed better than those with other infill materials, experiencing lower base shear and displacements.
3. Instructional Objectives:
At the end of this lesson, the student should be able to:
• explain the two major and other requirements of the design of foundation,
• identify five points indicating the differences between the design of
foundation and the design of other elements of the superstructure,
• differentiate between footing and foundation,
• differentiate between shallow and deep foundations,
• identify the situations when a combined footing shall be used,
• explain the safe bearing capacity of soil mentioning the difference
between gross and net safe bearing capacities,
• determine the minimum depth of foundation,
• determine the critical sections of bending moment and shear in isolated
footings,
• draw the distributions of pressure of soil below the footing for concentric
and eccentric loads with e ≤ L/6 and e > L/6,
• determine the soil pressure in a foundation which is unsymmetrical.
11.28.1 Introduction
Till now we discussed the different structural elements viz. beams, slabs,
staircases and columns, which are placed above the ground level and are known
as superstructure. The superstructure is placed on the top of the foundation
structure, designated as substructure as they are placed below the ground level.
The elements of the superstructure transfer the loads and moments to its
adjacent element below it and finally all loads and moments come to the
foundation structure, which in turn, transfers them to the underlying soil or rock.
Thus, the foundation structure effectively supports the superstructure. However,
all types of soil get compressed significantly and cause the structure to settle.
Accordingly, the major requirements of the design of foundation structures are
the two as given below (see cl.34.1 of IS 456):
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4. 1. Foundation structures should be able to sustain the applied loads,
moments, forces and induced reactions without exceeding the safe bearing
capacity of the soil.
2. The settlement of the structure should be as uniform as possible and it
should be within the tolerable limits. It is well known from the structural analysis
that differential settlement of supports causes additional moments in statically
indeterminate structures. Therefore, avoiding the differential settlement is
considered as more important than maintaining uniform overall settlement of the
structure.
In addition to the two major requirements mentioned above, the foundation
structure should provide adequate safety for maintaining the stability of structure
due to either overturning and/or sliding (see cl.20 of IS 456). It is to be noted that
this part of the structure is constructed at the first stage before other components
(columns / beams etc.) are taken up. So, in a project, foundation design and
details are completed before designs of other components are undertaken.
However, it is worth mentioning that the design of foundation structures is
somewhat different from the design of other elements of superstructure due to
the reasons given below. Therefore, foundation structures need special attention
of the designers.
1. Foundation structures undergo soil-structure interaction. Therefore, the
behaviour of foundation structures depends on the properties of structural
materials and soil. Determination of properties of soil of different types itself is a
specialized topic of geotechnical engineering. Understanding the interacting
behaviour is also difficult. Hence, the different assumptions and simplifications
adopted for the design need scrutiny. In fact, for the design of foundations of
important structures and for difficult soil conditions, geotechnical experts should
be consulted for the proper soil investigation to determine the properties of soil,
strata wise and its settlement criteria.
2. Accurate estimations of all types of loads, moments and forces are
needed for the present as well as for future expansion, if applicable. It is very
important as the foundation structure, once completed, is difficult to strengthen in
future.
3. Foundation structures, though remain underground involving very little
architectural aesthetics, have to be housed within the property line which may
cause additional forces and moments due to the eccentricity of foundation.
4. Foundation structures are in direct contact with the soil and may be
affected due to harmful chemicals and minerals present in the soil and
fluctuations of water table when it is very near to the foundation. Moreover,
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5. periodic inspection and maintenance are practically impossible for the foundation
structures.
5. Foundation structures, while constructing, may affect the adjoining
structure forming cracks to total collapse, particularly during the driving of piles
etc.
However, wide ranges of types of foundation structures are available. It is
very important to select the appropriate type depending on the type of structure,
condition of the soil at the location of construction, other surrounding structures
and several other practical aspects as mentioned above.
11.28.2 Types of Foundation Structures
Foundations are mainly of two types: (i) shallow and (ii) deep foundations.
The two different types are explained below:
(A) Shallow foundations
Shallow foundations are used when the soil has sufficient strength within a
short depth below the ground level. They need sufficient plan area to transfer the
heavy loads to the base soil. These heavy loads are sustained by the reinforced
concrete columns or walls (either of bricks or reinforced concrete) of much less
areas of cross-section due to high strength of bricks or reinforced concrete when
compared to that of soil. The strength of the soil, expressed as the safe bearing
capacity of the soil as discussed in sec.11.28.3, is normally supplied by the
geotechnical experts to the structural engineer. Shallow foundations are also
designated as footings. The different types of shallow foundations or footings are
discussed below.
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6. 1. Plain concrete pedestal footings
Plain concrete pedestal footings (Fig.11.28.1) are very economical for
columns of small loads or pedestals without any longitudinal tension steel (see
cls.34.1.2 and 34.1.3 of IS 456). In Fig.11.28.1, the angle α between the plane
passing through the bottom edge of the pedestal and the corresponding junction
edge of the column with pedestal and the horizontal plane shall be determined
from Eq. 11.3.
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10. These footings are for individual columns having the same plan forms of
square, rectangular or circular as that of the column, preferably maintaining the
proportions and symmetry so that the resultants of the applied forces and
reactions coincide. These footings, shown in Figs.11.27.2 to 11.27.4, consist of a
slab of uniform thickness, stepped or sloped. Though sloped footings are
economical in respect of the material, the additional cost of formwork does not
offset the cost of the saved material. Therefore, stepped footings are more
economical than the sloped ones. The adjoining soil below footings generates
upward pressure which bends the slab due to cantilever action. Hence, adequate
tensile reinforcement should be provided at the bottom of the slab (tension face).
Clause 34.1.1 of IS 456 stipulates that the sloped or stepped footings, designed
as a unit, should be constructed to ensure the integrated action. Moreover, the
effective cross-section in compression of sloped and stepped footings shall be
limited by the area above the neutral plane. Though symmetrical footings are
desirable, sometimes situation compels for unsymmetrical isolated footings
(Eccentric footings or footings with cut outs) either about one or both the axes
(Figs.11.28.5 and 6).
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12. When the spacing of the adjacent columns is so close that separate isolated
footings are not possible due to the overlapping areas of the footings or
inadequate clear space between the two areas of the footings, combined footings
are the solution combining two or more columns. Combined footing normally
means a footing combining two columns. Such footings are either rectangular or
trapezoidal in plan forms with or without a beam joining the two columns, as
shown in Figs.11.28.7 and 11.28.8.
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13. 4. Strap footings
When two isolated footings are combined by a beam with a view to
sharing the loads of both the columns by the footings, the footing is known as
strap footing (Fig.11.28.9). The connecting beam is designated as strap beam.
These footings are required if the loads are heavy on columns and the areas of
foundation are not overlapping with each other.
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14. 5. Strip foundation or wall footings
These are in long strips especially for load bearing masonry walls or
reinforced concrete walls (Figs.11.28.10). However, for load bearing masonry
walls, it is common to have stepped masonry foundations. The strip footings
distribute the loads from the wall to a wider area and usually bend in transverse
direction. Accordingly, they are reinforced in the transverse direction mainly,
while nominal distribution steel is provided along the longitudinal direction.
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15. 6. Raft or mat foundation
These are special cases of combined footing where all the columns of the
building are having a common foundation (Fig.11.28.11). Normally, for buildings
with heavy loads or when the soil condition is poor, raft foundations are very
much useful to control differential settlement and transfer the loads not
exceeding the bearing capacity of the soil due to integral action of the raft
foundation. This is a threshold situation for shallow footing beyond which deep
foundations have to be adopted.
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17. As mentioned earlier, the shallow foundations need more plan areas due
to the low strength of soil compared to that of masonry or reinforced concrete.
However, shallow foundations are selected when the soil has moderately good
strength, except the raft foundation which is good in poor condition of soil also.
Raft foundations are under the category of shallow foundation as they have
comparatively shallow depth than that of deep foundation. It is worth mentioning
that the depth of raft foundation is much larger than those of other types of
shallow foundations.
However, for poor condition of soil near to the surface, the bearing
capacity is very less and foundation needed in such situation is the pile
foundation (Figs.11.28.12). Piles are, in fact, small diameter columns which are
driven or cast into the ground by suitable means. Precast piles are driven and
cast-in-situ are cast. These piles support the structure by the skin friction
between the pile surface and the surrounding soil and end bearing force, if such
resistance is available to provide the bearing force. Accordingly, they are
designated as frictional and end bearing piles. They are normally provided in a
group with a pile cap at the top through which the loads of the superstructure are
transferred to the piles.
Piles are very useful in marshy land where other types of foundation are
impossible to construct. The length of the pile which is driven into the ground
depends on the availability of hard soil/rock or the actual load test. Another
advantage of the pile foundations is that they can resist uplift also in the same
manner as they take the compression forces just by the skin friction in the
opposite direction.
However, driving of pile is not an easy job and needs equipment and
specially trained persons or agencies. Moreover, one has to select pile
foundation in such a situation where the adjacent buildings are not likely to be
damaged due to the driving of piles. The choice of driven or bored piles, in this
regard, is critical.
Exhaustive designs of all types of foundations mentioned above are
beyond the scope of this course. Accordingly, this module is restricted to the
design of some of the shallow footings, frequently used for normal low rise
buildings only.
11.28.3 Safe Bearing Capacity of Soil
The safe bearing capacity qc of soil is the permissible soil pressure
considering safety factors in the range of 2 to 6 depending on the type of soil,
approximations and assumptions and uncertainties. This is applicable under
service load condition and, therefore, the partial safety factors fλ for different
load combinations are to be taken from those under limit state of serviceability
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18. (vide Table 18 of IS 456 or Table 2.1 of Lesson 3). Normally, the acceptable
value of qc is supplied by the geotechnical consultant to the structural engineer
after proper soil investigations. The safe bearing stress on soil is also related to
corresponding permissible displacement / settlement.
Gross and net bearing capacities are the two terms used in the design.
Gross bearing capacity is the total safe bearing pressure just below the footing
due to the load of the superstructure, self weight of the footing and the weight of
earth lying over the footing. On the other hand, net bearing capacity is the net
pressure in excess of the existing overburden pressure. Thus, we can write
Net bearing capacity = Gross bearing capacity - Pressure due to overburden
soil (11.1)
While calculating the maximum soil pressure q, we should consider all the
loads of superstructure along with the weight of foundation and the weight of the
backfill. During preliminary calculations, however, the weight of the foundation
and backfill may be taken as 10 to 15 per cent of the total axial load on the
footing, subjected to verification afterwards.
11.28.4 Depth of Foundation
All types of foundation should have a minimum depth of 50 cm as per IS
1080-1962. This minimum depth is required to ensure the availability of soil
having the safe bearing capacity assumed in the design. Moreover, the
foundation should be placed well below the level which will not be affected by
seasonal change of weather to cause swelling and shrinking of the soil. Further,
frost also may endanger the foundation if placed at a very shallow depth.
Rankine formula gives a preliminary estimate of the minimum depth of foundation
and is expressed as
d = (qc/λ ){(1 - sinφ )/(1 + sinφ )}2
(11.2)
where d = minimum depth of foundation
qc = gross bearing capacity of soil
λ = density of soil
φ = angle of repose of soil
Though Rankine formula considers three major soil properties qc, λ and
φ , it does not consider the load applied to the foundation. However, this may be
a guideline for an initial estimate of the minimum depth which shall be checked
subsequently for other requirements of the design.
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19. 11.28.5 Design Considerations
(a) Minimum nominal cover (cl. 26.4.2.2 of IS 456)
The minimum nominal cover for the footings should be more than that of
other structural elements of the superstructure as the footings are in direct
contact with the soil. Clause 26.4.2.2 of IS 456 prescribes a minimum cover of 50
mm for footings. However, the actual cover may be even more depending on the
presence of harmful chemicals or minerals, water table etc.
(b) Thickness at the edge of footings (cls. 34.1.2 and 34.1.3 of IS 456)
The minimum thickness at the edge of reinforced and plain concrete
footings shall be at least 150 mm for footings on soils and at least 300 mm above
the top of piles for footings on piles, as per the stipulation in cl.34.1.2 of IS 456.
For plain concrete pedestals, the angle α (see Fig.11.28.1) between the
plane passing through the bottom edge of the pedestal and the corresponding
junction edge of the column with pedestal and the horizontal plane shall be
determined from the following expression (cl.34.1.3 of IS 456)
tanα 0.9{(100 q≤ a/fck) + 1}1/2
(11.3)
where qa = calculated maximum bearing pressure at the base of pedestal in
N/mm2
, and
fck = characteristic strength of concrete at 28 days in N/mm2
.
(c) Bending moments (cl. 34.2 of IS 456)
1. It may be necessary to compute the bending moment at several
sections of the footing depending on the type of footing, nature of loads and the
distribution of pressure at the base of the footing. However, bending moment at
any section shall be determined taking all forces acting over the entire area on
one side of the section of the footing, which is obtained by passing a vertical
plane at that section extending across the footing (cl.34.2.3.1 of IS 456).
2. The critical section of maximum bending moment for the purpose of
designing an isolated concrete footing which supports a column, pedestal or wall
shall be:
(i) at the face of the column, pedestal or wall for footing supporting a
concrete column, pedestal or reinforced concrete wall, (Figs.11.28.2,
3 and 10), and
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20. (ii) halfway between the centre-line and the edge of the wall, for footing
under masonry wall (Fig.11.28.10). This is stipulated in cl.34.2.3.2 of
IS 456.
The maximum moment at the critical section shall be determined as
mentioned in 1 above.
For round or octagonal concrete column or pedestal, the face of the
column or pedestal shall be taken as the side of a square inscribed within the
perimeter of the round or octagonal column or pedestal (see cl.34.2.2 of IS 456
and Figs.11.28.13a and b).
(d) Shear force (cl. 31.6 and 34.2.4 of IS 456)
Footing slabs shall be checked in one-way or two-way shears depending
on the nature of bending. If the slab bends primarily in one-way, the footing slab
shall be checked in one-way vertical shear. On the other hand, when the bending
is primarily two-way, the footing slab shall be checked in two-way shear or
punching shear. The respective critical sections and design shear strengths are
given below:
1. One-way shear (cl. 34.2.4 of IS 456)
One-way shear has to be checked across the full width of the base slab on
a vertical section located from the face of the column, pedestal or wall at a
distance equal to (Figs.11.28.2, 3 and 10):
(i) effective depth of the footing slab in case of footing slab on soil, and
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21. (ii) half the effective depth of the footing slab if the footing slab is on piles
(Fig.11.28.12).
The design shear strength of concrete without shear reinforcement is
given in Table 19 of cl.40.2 of IS 456.
2. Two-way or punching shear (cls.31.6 and 34.2.4)
Two-way or punching shear shall be checked around the column on a
perimeter half the effective depth of the footing slab away from the face of the
column or pedestal (Figs.11.28.2 and 3).
The permissible shear stress, when shear reinforcement is not provided,
shall not exceed ks cτ , where ks = (0.5 + cβ ), but not greater than one, cβ being
the ratio of short side to long side of the column, and cτ = 0.25(fck)1/2
in limit state
method of design, as stipulated in cl.31.6.3 of IS 456.
Normally, the thickness of the base slab is governed by shear. Hence, the
necessary thickness of the slab has to be provided to avoid shear reinforcement.
(e) Bond (cl.34.2.4.3 of IS 456)
The critical section for checking the development length in a footing slab
shall be the same planes as those of bending moments in part (c) of this section.
Moreover, development length shall be checked at all other sections where they
change abruptly. The critical sections for checking the development length are
given in cl.34.2.4.3 of IS 456, which further recommends to check the anchorage
requirements if the reinforcement is curtailed, which shall be done in accordance
with cl.26.2.3 of IS 456.
(f) Tensile reinforcement (cl.34.3 of IS 456)
The distribution of the total tensile reinforcement, calculated in accordance
with the moment at critical sections, as specified in part (c) of this section, shall
be done as given below for one-way and two-way footing slabs separately.
(i) In one-way reinforced footing slabs like wall footings, the reinforcement
shall be distributed uniformly across the full width of the footing i.e.,
perpendicular to the direction of wall. Nominal distribution reinforcement shall be
provided as per cl. 34.5 of IS 456 along the length of the wall to take care of the
secondary moment, differential settlement, shrinkage and temperature effects.
(ii) In two-way reinforced square footing slabs, the reinforcement
extending in each direction shall be distributed uniformly across the full
width/length of the footing.
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22. (iii) In two-way reinforced rectangular footing slabs, the reinforcement in
the long direction shall be distributed uniformly across the full width of the footing
slab. In the short direction, a central band equal to the width of the footing shall
be marked along the length of the footing, where the portion of the reinforcement
shall be determined as given in the equation below. This portion of the
reinforcement shall be distributed across the central band:
Reinforcement in the central band = {2/( β +1)} (Total reinforcement in the short
direction)
(11.4)
where β is the ratio of longer dimension to shorter dimension of the footing slab
(Fig.11.28.14).
Each of the two end bands shall be provided with half of the remaining
reinforcement, distributed uniformly across the respective end band.
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23. (g) Transfer of load at the base of column (cl.34.4 of IS 456)
All forces and moments acting at the base of the column must be
transferred to the pedestal, if any, and then from the base of the pedestal to the
footing, (or directly from the base of the column to the footing if there is no
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24. pedestal) by compression in concrete and steel and tension in steel.
Compression forces are transferred through direct bearing while tension forces
are transferred through developed reinforcement. The permissible bearing
stresses on full area of concrete shall be taken as given below from cl.34.4 of IS
456:
brσ = 0.25fck, in working stress method, and
(11.5)
brσ = 0.45fck, in limit state method
(11.6)
It has been mentioned in sec. 10.26.5 of Lesson 26 that the stress of concrete is
taken as 0.45fck while designing the column. Since the area of footing is much
larger, this bearing stress of concrete in column may be increased considering
the dispersion of the concentrated load of column to footing. Accordingly, the
permissible bearing stress of concrete in footing is given by (cl.34.4 of IS 456):
brσ = 0.45fck (A1/A2)1/2
(11.7)
with a condition that
(A1/A2)1/2
2.0
(11.8)
≤
where A1 = maximum supporting area of footing for bearing which is
geometrically similar to and concentric with the loaded area A2, as
shown in Fig.11.28.15
A2 = loaded area at the base of the column.
The above clause further stipulates that in sloped or stepped footings, A1 may be
taken as the area of the lower base of the largest frustum of a pyramid or cone
contained wholly within the footing and having for its upper base, the area
actually loaded and having side slope of one vertical to two horizontal, as shown
in Fig.11.28.15.
If the permissible bearing stress on concrete in column or in footing is
exceeded, reinforcement shall be provided for developing the excess force
(cl.34.4.1 of IS 456), either by extending the longitudinal bars of columns into the
footing (cl.34.4.2 of IS 456) or by providing dowels as stipulated in cl.34.4.3 of IS
456 and given below:
(i) Sufficient development length of the reinforcement shall be provided to
transfer the compression or tension to the supporting member in accordance with
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25. cl.26.2 of IS 456, when transfer of force is accomplished by reinforcement of
column (cl.34.4.2 of IS 456).
(ii) Minimum area of extended longitudinal bars or dowels shall be 0.5 per
cent of the cross-sectional area of the supported column or pedestal (cl.34.4.3 of
IS 456).
(iii) A minimum of four bars shall be provided (cl.34.4.3 of IS 456).
(iv) The diameter of dowels shall not exceed the diameter of column bars
by more than 3 mm.
(v) Column bars of diameter larger than 36 mm, in compression only can
be doweled at the footings with bars of smaller size of the necessary area. The
dowel shall extend into the column, a distance equal to the development length
of the column bar and into the footing, a distance equal to the development
length of the dowel, as stipulated in cl.34.4.4 of IS 456 and as shown in
Fig.11.28.16.
(h) Nominal reinforcement (cl. 34.5 of IS 456)
1. Clause 34.5.1 of IS 456 stipulates the minimum reinforcement and
spacing of the bars in footing slabs as per the requirements of solid slab
(cls.26.5.2.1 and 26.3.3b(2) of IS 456, respectively).
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26. 2. The nominal reinforcement for concrete sections of thickness greater
than 1 m shall be 360 mm2
per metre length in each direction on each face, as
stipulated in cl.34.5.2 of IS 456. The clause further specifies that this provision
does not supersede the requirement of minimum tensile reinforcement based on
the depth of section.
11.28.6 Distribution of Base Pressure
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27. The foundation, assumed to act as a rigid body, is in equilibrium under the
action of applied forces and moments from the superstructure and the reactions
from the stresses in the soil. The distribution of base pressure is different for
different types of soil. Typical distributions of pressure, for actual foundations, in
sandy and clayey soils are shown in Figs.11.28.17 and 18, respectively.
However, for the sake of simplicity the footing is assumed to be a perfectly rigid
body, the soil is assumed to behave elastically and the distributions of stress and
stain are linear in the soil just below the base of the foundation, as shown in
Fig.11.28.19. Accordingly, the foundation shall be designed for the applied loads,
moments and induced reactions keeping in mind that the safe bearing capacity of
the soil is within the prescribed limit. It is worth mentioning that the soil bearing
capacity is in the serviceable limit state and the foundation structure shall be
designed as per the limit state of collapse, checking for other limit states as well
to ensure an adequate degree of safety and serviceability.
In the following, the distributions of base pressure are explained for (i)
concentrically loaded footings, (ii) eccentrically loaded footings and (iii)
unsymmetrical (about both the axes) footings.
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28. (i) Concentrically loaded footings
Figure 11.28.20 shows rectangular footing symmetrically loaded with
service load P1 from the superstructure and P2 from the backfill including the
weight of the footing. The assumed uniformly distributed soil pressure at the base
of magnitude q is obtained from:
q = (P1 + P2)/A
(11.9)
where A is the area of the base of the footing.
In the design problem, however, A is to be determined from the condition
that the actual gross intensity of soil pressure does not exceed qc, the bearing
capacity of the soil, a known given data. Thus, we can write from Eq.11.9:
A = (P1 + P2)/qc
(11.10)
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29. From the known value of A, the dimensions B and L are determined such
that the maximum bending moment in each of the two adjacent projections is
equal, i.e., the ratio of the dimensions B and L of the footing shall be in the same
order of the ratio of width b and depth D of the column.
(ii) Eccentrically loaded footings
In most of the practical situations, a column transfers axial load P and
moment M to the footing, which can be represented as eccentrically loaded
footing when a load P is subjected to an eccentricity e = M/P. This eccentricity
may also be there, either alone or in combined mode, when
• the column transfers a vertical load at a distance of e from the centroidal axis
of the footing, and
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30. • the column or the pedestal transfers a lateral load above the level of
foundation, in addition to vertical loads.
Accordingly, the distribution of pressure may be of any one of the three
types, depending on the magnitude of the eccentricity of the load, as shown in
Figs.11.28.21b to d. The general expression of qa, the intensity of soil pressure at
a distance of y from the origin is:
qa = P/A (Pe/I± x)y
(11.11)
We would consider a rectangular footing symmetric to the column. Substituting
the values of A = BL, Ix = BL3
/12 and y = L/2, we get the values of qa at the left
edge.
qa at the left edge = (P/BL) {1 - (6e/L)}
(11.12)
It is evident from Eq.11.12, that the three cases are possible:
(A) when e < L/6, qa at the left edge is compression (+),
(B) when e = L/6, qa at the left edge is zero, and
(C) when e > L/6, qa at the left edge is tension (-).
The three cases are shown in Figs.11.28.21b to d, respectively. It is to be noted
that similar three cases are also possible when eccentricity of the load is
negative resulting the values of qa at the right edge as compression, zero or
tension. Evidently, these soil reactions, in compression and tension, should be
permissible and attainable.
Case (A): when | e | ≤ L/6
Figures 11.28.21b and c show these two cases, when |e| < L/6 or |e| =
L/6, respectively. It is seen that the entire area of the footing is in compression
having minimum and maximum values of q at the two edges with a linear and
non-uniform variation. The values of q are obtained from Eq.11.11.
In the limiting case i.e., when |e| = L/6, the value of qa is zero at one edge
and the other edge is having qa = 2P/BL (compression) with a linear variation.
Similarly, when e = 0, the footing is subjected to uniform constant pressure of
P/BL. Thus, when |e| = L/6, the maximum pressure under one edge of the footing
is twice of the uniform pressure when e = 0.
Version 2 CE IIT, Kharagpur
31. In a more general case, as in the case of footing for the corner column of
a building, the load may have biaxial eccentricities. The general expression of qa
at a location of (x,y) of the footing, when the load is having biaxial eccentricities
of ex and ey is,
qa = P/A ± P exy/Ix ± P eyx/Iy
(11.13)
Similarly, it can be shown that the rectangular footing of width B and
length L will have no tension when the two eccentricities are such that
6ex/L + 6ey/B ≤ 1
(11.14)
Case (B): when | e | > L/6
Version 2 CE IIT, Kharagpur
32. The eccentricity of the load more than L/6 results in development of tensile
stresses in part of the soil. Stability, in such case, is ensured by either anchoring
or weight of overburden preventing uplift. However, it is to ensure that maximum
compressive pressure on the other face is within the limit and sufficient factor of
safety is available against over turning. Accordingly, the maximum pressure in
such a case can be determined considering the soil under compression part only.
Further, assuming the line of action of the eccentric load coincides with that of
resultant soil pressure (Fig.11.28.22) we have:
qmax = P/L'B + 12P(0.5 C)(1.5 C)/BL' = 2P/L'B
(11.15)
where L' = 3C
(11.16)
(iii) Unsymmetrical footings
It may be necessary to provide some cutouts in the foundation to reduce
the uplift pressure or otherwise. The footing in such cases becomes
unsymmetrical about both the axes. It is possible to determine the soil pressure
distribution using the structural mechanics principle as given below.
qa(x,y) = P/A {(M± yIx - MxIxy)(x)/(IxIy - )} + {(M2
xyI xIy - MyIxy)(y)/(IxIy - )}
(11.17)
2
xyI
where Mx = moment about x axis,
My = moment about y axis,
Ix = moment of inertia about x axis,
Iy = moment of inertia about y axis,
Ixy = product of inertia
11.28.7 Practice Questions and Problems with Answers
Q.1: (A) What are the two essential requirements of the design of foundation?
(B) Mention five points indicating the differences between the design of
foundation and the design of other elements of superstructure.
A.1: See sec. 11.28.1.
Q.2: Draw sketches of different shallow foundations.
Version 2 CE IIT, Kharagpur
33. A.2: Figure Nos. 11.28.1 to 11.
Q.3: Explain the difference between gross and net safe bearing capacities of soil.
Which one is used for the design of foundation?
A.3: See sec. 11.28.3.
Q.4: How would you determine the minimum depth of foundation?
A.4: See sec.11.28.4.
Q.5: What are the critical sections of determining the bending moment in
isolated footing?
A.5: See part (c)2 of sec.11.28.5.
Q.6: Explain the one-way and two-way shears of foundation slabs.
A.6: See part (d) of sec.11.28.5.
Q.7: Draw the actual distributions of base pressures of soil below the footing in
sandy and clayey soils. Draw the assumed distribution of base pressure
below the footing.
A.7: Figure Nos. 11.28.17 and 18.
Q.8: Draw the distributions of pressure in a footing for concentric and
eccentric loadings (e ≤ L/6 and e > L/6).
A.8: Figure Nos. 11.28.20 and 21.
Q.9: How would you determine the pressure at any point (x,y) of a foundation
which is unsymmetrical?
A.9: See part (iii) of sec.11.28.6.
11.28.8 References
1. Reinforced Concrete Limit State Design, 6th
Edition, by Ashok K. Jain,
Nem Chand & Bros, Roorkee, 2002.
2. Limit State Design of Reinforced Concrete, 2nd
Edition, by P.C.Varghese,
Prentice-Hall of India Pvt. Ltd., New Delhi, 2002.
3. Advanced Reinforced Concrete Design, by P.C.Varghese, Prentice-Hall of
India Pvt. Ltd., New Delhi, 2001.
Version 2 CE IIT, Kharagpur
34. 4. Reinforced Concrete Design, 2nd
Edition, by S.Unnikrishna Pillai and
Devdas Menon, Tata McGraw-Hill Publishing Company Limited, New
Delhi, 2003.
5. Limit State Design of Reinforced Concrete Structures, by P.Dayaratnam,
Oxford & I.B.H. Publishing Company Pvt. Ltd., New Delhi, 2004.
6. Reinforced Concrete Design, 1st
Revised Edition, by S.N.Sinha, Tata
McGraw-Hill Publishing Company. New Delhi, 1990.
7. Reinforced Concrete, 6th
Edition, by S.K.Mallick and A.P.Gupta, Oxford &
IBH Publishing Co. Pvt. Ltd. New Delhi, 1996.
8. Behaviour, Analysis & Design of Reinforced Concrete Structural Elements,
by I.C.Syal and R.K.Ummat, A.H.Wheeler & Co. Ltd., Allahabad, 1989.
9. Reinforced Concrete Structures, 3rd
Edition, by I.C.Syal and A.K.Goel,
A.H.Wheeler & Co. Ltd., Allahabad, 1992.
10.Textbook of R.C.C, by G.S.Birdie and J.S.Birdie, Wiley Eastern Limited,
New Delhi, 1993.
11.Design of Concrete Structures, 13th
Edition, by Arthur H. Nilson, David
Darwin and Charles W. Dolan, Tata McGraw-Hill Publishing Company
Limited, New Delhi, 2004.
12.Concrete Technology, by A.M.Neville and J.J.Brooks, ELBS with
Longman, 1994.
13.Properties of Concrete, 4th
Edition, 1st
Indian reprint, by A.M.Neville,
Longman, 2000.
14.Reinforced Concrete Designer’s Handbook, 10th
Edition, by C.E.Reynolds
and J.C.Steedman, E & FN SPON, London, 1997.
15.Indian Standard Plain and Reinforced Concrete – Code of Practice (4th
Revision), IS 456: 2000, BIS, New Delhi.
16.Design Aids for Reinforced Concrete to IS: 456 – 1978, BIS, New Delhi.
11.28.9 Test 28 with Solutions
Maximum Marks = 50, Maximum Time = 30 minutes
Answer all questions.
TQ.1: (A) What are the two essential requirements of the design of foundation?
(5
marks)
(B) Mention five points indicating the differences between the design of
foundation and the design of other elements of superstructure.
(5 marks)
A.TQ.1: See sec. 11.28.1.
TQ.2: How would you determine the minimum depth of foundation? (10
marks)
Version 2 CE IIT, Kharagpur
35. A.TQ.2: See sec.11.28.4.
TQ.3: What are the critical sections of determining the bending moment in
isolated footing?
(10 marks)
A.TQ.3: See part (c)2 of sec.11.28.5.
TQ.4: Explain the one-way and two-way shears of foundation slabs. (10
marks)
A.TQ.4: See part (d) of sec.11.28.5.
TQ.5: Draw the distributions of pressure in a footing for concentric and
eccentric loadings (e ≤ L/6 and e > L/6).
(10 marks)
A.TQ.5: Figure Nos. 11.28.20 and 21.
10.26.11 Summary of this Lesson
This lesson explains the two major and other requirements of the
design of foundation structures. Various types of shallow foundations and pile
foundation are discussed explaining the distribution of pressure in isolated
footings loaded concentrically and eccentrically with e ≤ L/6 and e > L/6. The
gross and net safe bearing capacities are explained. The equation for
determining the minimum depth of the foundation is given. Various design
considerations in respect of minimum nominal cover, thickness at the edge of
footing, bending moment, shear force, bond, tensile reinforcement, transfer of
load at the base of the column, and minimum distribution reinforcement are
discussed, mentioning the codal requirements. The actual and the assumed
distributions of base pressure are discussed. The distributions of base pressure
for concentric and eccentric loads with eccentricity ≤ L/6 and > L/6 are
explained. Determination of bearing pressure of soil for unsymmetrical footing is
also discussed.
All the discussions are relevant in understanding the load carrying
mechanism of the foundation and the behaviour of soil. These understandings
are essential in designing the foundation structures which is taken up in the next
lesson.
Version 2 CE IIT, Kharagpur