Design of Staircase and Flat Slabs

Design of Staircase and Flat Slabs

Contents

Recall various components of a Staircase. 1

Classify Staircase 1

Describe guidelines for the provision of components of a Staircase as per IS: 456-2000 6

Recall the conditions for an effective span of a Staircase. 8

Describe the different loads on a Staircase. 9

Recall the steps to design a Staircase. 9

Describe different Components of Flat Slab along with their Function. 10

Describe the Moment calculation along with the Column strip and Middle strip in the following Panels: i. Interior Panel ii. Exterior Panel 11

Recall IS Guidelines for Flat Slab Reinforcement. 12

Recall the concept of Shear in Flat Slab. 13

Describe the Openings in Flat Slab. 14

Describe the steps to design the Flat Slab. 15

Recall various components of a Staircase.

A staircase is a set of steps used for vertical transportation between floors or levels in a building. The various components of a staircase include:

  1. Treads: The flat horizontal surface of each step, where a person places their feet when climbing or descending the staircase.
  2. Risers: The vertical surface that separates each tread.
  3. Stringers: The structural members that support the treads and risers. They are usually located on either side of the staircase and are typically made of steel or concrete.
  4. Balustrade: The railing system along the sides of the staircase that provides safety and stability. It can be made of various materials, such as wood, glass, or metal, and is supported by balusters.
  5. Balusters: The vertical posts that support the balustrade.
  6. Newel Posts: The larger, more robust posts that provide additional support to the balustrade and mark the beginning and end of the staircase.
  7. Handrails: The horizontal railing located at waist height on the sides of the staircase, which provides a handhold for stability while climbing or descending the staircase.
  8. Landings: The flat platform located between flights of steps. Landings provide a rest area and can also serve as a turning point for changing direction in the staircase.

Classify Staircase

Stairs are classified on the basis of their geometrical and structural configurations.

On the basis of their geometric configuration the stairs are:

  1. Single Flight/ straight stairs
  2. Quarter Turn
  3. Dog legged
  4. Spiral
  5. Helicoidal
  6. Straight stairs: Generally for small houses, available width is very retractable. So, this type of straight stairs are used in such conditions which runs straight between two floors. This stair may consist of either one single flight or more than one flight with a landing.
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  7. Quarter turn stairs: A quarter turn stair is the one which changes its direction either to the right or to the left but where the turn is affected either by introducing a quarter space landing or by providing winders. In these types of stairs the flight of stairs turns 90 degrees at landing as it rises to connect two different levels. So it is also called the L-stair. Again these quarter turn stairs are two types
  8. Newel quarter turn stairs

These types of stairs have clearly visible newel posts at the beginning of flight as well as at the end. At the quarter turn, there may either be quarter space landing or there may be winders.

  1. Geometrical quarter turn stairs: In geometrical stairs, the stringer as well as the handrail is continuous without any newel post at the landing area.

3. Dog-legged stairs

Because of its appearance in sectional elevation this name is given. It comes under the category of newel stairs in which newel posts are provided at the beginning and end of each flight

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4. Spiral Stairs:spiral stairs are usually made either of R.C.C or metal, and is placed at a location where there are space limitations. Sometimes these are also used as emergency stairs, and are provided at the back side of a building. These are not comfortable because all the steps are winded and provide discomfort.

5. Helical Stairs: A helical stair looks very fine but its structural design and construction is very complicated. It is made of R.C.C in which a large portion of steel is required to resist bending, shear and torsion.

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Structural Configuration:

  1. Stair slab Opening Transverse: Transverse stairs are located remotely from each other and connect the two wings of the building. Wing stairs are one or two stairs located at the front and rear of each wing. Isolated stairs provide access limited to apartments served by the stairs and there is no access to other wings.
  2. Stair slab Opening Longitudinally:

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Describe guidelines for the provision of components of a Staircase as per IS: 456-2000

following are some of the general guidelines to be considered while Design of staircase:

The respective dimensions of tread and riser for all the parallel steps should be the same in consecutive floor of a building.

The minimum vertical headroom above any step should be 2 m.

Generally, the number of risers in a flight should be restricted to twelve.

The minimum width of the stair should be 850 mm, though it is desirable to have the width between 1.1 to 1.6 m. In public building, cinema halls etc., large widths of the stair should be provide

Step 1:Tread
Dwelling Houses and Factories Tread = 250 mm
Public Building Tread = 270 mm
Riser
Public Building Riser = 150mm
Factories Riser = 190 mm
Residential Building = 160 mm
These values are not fixed, but used for reference purposes.

Tread is also known as Going (G) > we can also check design parameter according to a popular formula given below

It should follow 2R+G>550 The mm and 2R+G<700 mm i.e. 550mm<2R+G<700mm
It also depend on (i) the Span of staircase and (ii) Height of Building
(i) How to calculate Effective Span
In case 1: If value of x and y is less than 1(one), then Effective span = x+y+Going length
If value of x and y is greater than 1(one), then Effective span = 1+1+Going length
so Effective span should not be more than (Going length + 2)
In case 2: Effective Span = center to center distance of beam
Thickness of waist
Assume Span/Effective depth = 30
so depth = Effective depth – cover – bar dia/2

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Recall the conditions for an effective span of a Staircase.

An effective span of a staircase refers to the maximum distance that a staircase can span without intermediate support. The conditions for an effective span of a staircase are as follows:

  1. Load capacity: The effective span of a staircase must be able to support the expected loads, including the weight of users, any additional loads such as furniture or equipment, and any environmental loads such as wind or snow. The loads should be calculated based on the appropriate design codes and standards.
  2. Material strength: The material used to construct the staircase must have sufficient strength to support the expected loads. For example, concrete, steel, and wood are commonly used materials for staircase construction, and their strength must be sufficient to support the effective span.
  3. Deflection: The effective span of a staircase must not exceed the maximum allowable deflection, which is the amount that the staircase can bend or deform under load. The maximum allowable deflection is specified in the appropriate design codes and standards and must be taken into consideration when determining the effective span.
  4. Vibration: The effective span of a staircase must not exceed the maximum allowable vibration, which is the amount of movement or sway that the staircase can experience without causing discomfort or safety concerns for users. The maximum allowable vibration is specified in the appropriate design codes and standards and must be taken into consideration when determining the effective span.
  5. Stiffness: The effective span of a staircase must have sufficient stiffness to prevent excessive deformation or movement under load. The stiffness can be achieved by increasing the thickness of the staircase components, using stronger materials, or by using additional support elements such as beams or columns.

These conditions must be met in order for a staircase to have an effective span. It is important to consider these factors when designing and constructing a staircase to ensure its stability, safety, and functionality.

Describe the different loads on a Staircase.

A staircase is subject to various loads that must be taken into consideration when designing and constructing it. The different loads on a staircase can be divided into the following categories:

  1. Dead load: The dead load is the weight of the staircase itself, including all its components such as treads, risers, handrails, balusters, and any other elements. This load is constant and does not change over time.
  2. Live load: The live load is the weight of users and any other objects or equipment that may be carried on the staircase. This load is variable and can change depending on the number of users and the type of objects being carried.
  3. Environmental loads: Environmental loads are loads that come from external sources, such as wind, snow, and earthquakes. These loads must be considered when designing the staircase, especially for structures located in areas prone to these types of loads.
  4. Impact load: The impact load is the load that is created when objects or users fall onto the staircase. This load is typically much higher than the live load and must be taken into consideration when designing the staircase.
  5. Temporary loads: Temporary loads are loads that are temporary in nature and can be removed after a specified period of time. Examples of temporary loads include construction equipment, scaffolding, and other materials used during construction or maintenance.

These loads must be considered when designing a staircase to ensure its stability, safety, and functionality. The loads must be calculated and analyzed to determine the appropriate size and strength of the staircase components, and to ensure that the staircase can support the expected loads.

Recall the steps to design a Staircase.

The design of a staircase involves several steps that must be followed to ensure its stability, safety, and functionality. The steps to design a staircase are as follows:

  1. Determine the purpose and use of the staircase: This step involves determining the purpose and intended use of the staircase, such as residential, commercial, or industrial use. This information is important in determining the size and type of staircase needed, as well as the materials and components required.
  2. Determine the location and size of the staircase: This step involves determining the location and size of the staircase based on the intended use and the available space. The location and size of the staircase will impact the overall design and functionality of the staircase.
  3. Determine the load capacity: The load capacity of the staircase must be determined based on the expected loads, including the weight of users, any additional loads such as furniture or equipment, and any environmental loads such as wind or snow. The loads should be calculated based on the appropriate design codes and standards.
  4. Determine the material: The material used to construct the staircase must be determined based on the load capacity, the intended use, and any specific requirements such as fire resistance, durability, or maintenance requirements. Common materials used for staircase construction include concrete, steel, and wood.
  5. Determine the components: The components of the staircase, such as treads, risers, handrails, balusters, and any other elements, must be determined based on the load capacity, the material used, and any specific requirements such as slip resistance, durability, or maintenance requirements.
  6. Determine the support system: The support system for the staircase must be determined based on the load capacity and the size of the staircase. The support system can include beams, columns, or walls, and must be designed to provide adequate support and stability for the staircase.
  7. Determine the finishes: The finishes for the staircase, such as paint, wallpaper, or tiles, must be determined based on the intended use, the material used, and any specific requirements such as durability, maintenance, or slip resistance.

These steps must be followed in order to design a staircase that is safe, stable, and functional. It is important to consult with an engineer or architect who is knowledgeable in the design of staircases to ensure that the design meets all relevant codes and standards.

Describe different Components of Flat Slab along with their Function.

A flat slab is a type of reinforced concrete floor system that is used in construction. It consists of several components that work together to provide strength, stability, and support to the floor system. The different components of a flat slab, along with their functions, are as follows:

  1. Slab: The slab is the main component of the flat slab and provides the flat surface for the floor. It is typically made of reinforced concrete and is poured in one solid piece.
  2. Drop panels: Drop panels are smaller, rectangular sections of the slab that are separated from the main slab by cuts or joints. They are used to reduce the span of the slab and to provide additional support.
  3. Columns: Columns are vertical supports that transfer the load of the slab to the foundation. They are typically made of reinforced concrete and are placed at the corners or along the edges of the slab.
  4. Beams: Beams are horizontal members that transfer the load of the slab to the columns. They are typically made of reinforced concrete and are placed along the edges of the slab or around the drop panels.
  5. Reinforcing steel: Reinforcing steel, also known as rebar, is used to reinforce the concrete and to provide additional strength and stability to the slab. The reinforcing steel is placed in the slab and in the beams and columns and is anchored to the foundation.
  6. Stirrups: Stirrups are circular or rectangular steel members that are placed around the reinforcing steel in the slab and beams. They provide additional support and stability to the slab and help to prevent cracking.

These components work together to provide a strong, stable, and supportive floor system. The design of the flat slab must take into consideration the loads and stresses that will be applied to the slab, including the weight of the users, any additional loads, and any environmental loads such as wind or earthquakes. The components must be designed and constructed to meet the relevant codes and standards and to ensure the safety and stability of the flat slab.

Describe the Moment calculation along with the Column strip and Middle strip in the following Panels: i. Interior Panel ii. Exterior Panel

The moment calculation in flat slab systems involves determining the bending moment in the slab and the beams. Bending moments are forces that cause a structure to bend or deform due to applied loads. In flat slab systems, the bending moment is determined by considering the load distribution on the slab and the span of the slab and beams.

The column strip and middle strip are terms used to describe the different sections of the slab. The column strip is the portion of the slab closest to the columns, while the middle strip is the portion of the slab in the middle between the columns.

  1. Interior Panel: An interior panel is a panel located within the building and is surrounded by other panels on all sides. The moment calculation for an interior panel involves considering the load distribution on the slab, the span of the slab and beams, and the dimensions of the panel. The column strip of an interior panel will typically have a higher moment than the middle strip due to the presence of the columns.
  2. Exterior Panel: An exterior panel is a panel located on the exterior of the building and is surrounded by other panels on three sides. The moment calculation for an exterior panel involves considering the load distribution on the slab, the span of the slab and beams, and the dimensions of the panel. The middle strip of an exterior panel will typically have a higher moment than the column strip due to the longer span between the columns.

In both interior and exterior panels, the moment calculation must take into consideration the load distribution and the span of the slab and beams to ensure that the flat slab system is designed and constructed to provide adequate strength and stability. The calculation of moments must also be in accordance with the relevant codes and standards to ensure the safety and stability of the flat slab.

Recall IS Guidelines for Flat Slab Reinforcement.

The Indian Standard (IS) Guidelines for Flat Slab Reinforcement provide the specifications and guidelines for the design and construction of flat slab systems in India. The IS guidelines outline the requirements for the reinforcement of flat slabs, including the minimum amount of reinforcing steel required, the placement of reinforcing steel in the slab, and the design of stirrups and other reinforcement details.

Some of the key guidelines for flat slab reinforcement in IS 456-2000 include:

  1. Minimum reinforcement: The IS guidelines specify the minimum amount of reinforcing steel required in the slab and beams, based on the span of the slab and the loads that will be applied to the slab. The minimum amount of reinforcement is determined based on the thickness of the slab and the size of the beams.
  2. Reinforcing steel placement: The IS guidelines specify the placement of reinforcing steel in the slab, beams, and columns. The reinforcing steel must be placed in the slab and beams so that it is adequately distributed and provides adequate support and stability to the slab.
  3. Stirrups: The IS guidelines specify the design of stirrups and other reinforcement details. Stirrups are circular or rectangular steel members that are placed around the reinforcing steel in the slab and beams. They provide additional support and stability to the slab and help to prevent cracking.
  4. Cover: The IS guidelines specify the minimum cover required for the reinforcing steel in the slab and beams. The cover is the distance between the surface of the slab or beam and the reinforcing steel. The minimum cover is determined based on the type of structure and the environment in which the structure is located.
  5. Design load: The IS guidelines specify the design load that must be used when calculating the load distribution on the slab and determining the required reinforcement. The design load includes the weight of the slab, the weight of any additional loads, and any environmental loads such as wind or earthquakes.

These guidelines provide the specifications and requirements for the design and construction of flat slab systems in India, and must be followed to ensure the safety and stability of the flat slab. The IS guidelines are updated periodically to reflect advances in construction technology and materials, and to ensure that the guidelines remain relevant and effective.

Recall the concept of Shear in Flat Slab.

Shear is a critical concept in the design of flat slab systems. Shear refers to the forces that act perpendicular to the plane of the slab and can cause failure or instability in the slab. The concept of shear is important because flat slabs are more susceptible to shear forces than other types of slab systems, such as beam and slab systems or ribbed slab systems.

There are two main types of shear forces that can occur in a flat slab: shear forces along the column strip and shear forces along the middle strip. The column strip is the area of the slab that is closest to the columns, and the middle strip is the area of the slab that is located between the columns.

In order to design a flat slab that is resistant to shear forces, it is important to properly reinforce the slab with reinforcing steel and stirrups. The reinforcing steel provides the strength and stability necessary to resist shear forces, and the stirrups provide additional support and stability to the slab, helping to prevent cracking and failure.

In addition to proper reinforcement, the thickness of the slab and the size of the columns can also play a role in the resistance of a flat slab to shear forces. The thickness of the slab must be sufficient to provide adequate strength and stability, and the size of the columns must be large enough to provide adequate support to the slab.

The design of the slab must also take into account the loads that will be applied to the slab, including the weight of the slab and any additional loads, such as wind or earthquakes. The design must be able to resist these loads and ensure that the slab remains stable and secure.

In summary, the concept of shear is a critical aspect of the design of flat slab systems, and must be properly addressed in order to ensure the safety and stability of the slab. Proper reinforcement, slab thickness, column size, and load calculations are all important considerations in the design of a flat slab that is resistant to shear forces.

Describe the Openings in Flat Slab.

Openings in flat slabs refer to any cuts or holes in the slab, such as doorways, windows, vents, or other architectural features. These openings can significantly affect the structural performance of a flat slab and must be properly designed and integrated into the overall design of the slab system.

When designing openings in a flat slab, there are several factors that must be considered, including the size and location of the opening, the type of loading that will be applied to the slab, and the overall strength and stability of the slab.

The size and location of the opening will determine the amount of reinforcing steel that is required to maintain the structural integrity of the slab. For example, larger openings will require more reinforcing steel to resist shear forces and prevent cracking or failure of the slab. Additionally, the location of the opening can affect the distribution of loads and the stability of the slab.

The type of loading that will be applied to the slab, such as dead loads, live loads, and wind loads, must also be taken into account when designing openings in a flat slab. The design must be able to resist these loads and maintain the stability of the slab.

In addition to reinforcing steel, the design of the slab must also consider the impact of the opening on the overall strength and stability of the slab. For example, a large opening in the center of the slab may weaken the slab and affect its stability. In such cases, additional measures, such as increasing the slab thickness or reinforcing the slab with additional steel, may be necessary to maintain the strength and stability of the slab.

In conclusion, openings in flat slabs can have a significant impact on the structural performance of the slab and must be properly designed and integrated into the overall design of the slab system. Factors such as the size and location of the opening, the type of loading that will be applied to the slab, and the overall strength and stability of the slab must all be considered in the design of openings in a flat slab.

Describe the steps to design the Flat Slab.

The steps to design a flat slab are as follows:

  1. Determine the loads on the slab: The first step in designing a flat slab is to determine the loads that will be imposed on it. This includes dead loads, live loads, and any other loads that may be specific to the structure being designed.
  2. Determine the slab thickness: The thickness of the slab is determined based on the loads that will be imposed on it. This information is used to calculate the required reinforcement and overall stability of the slab.
  3. Determine the span: The span of the slab is determined based on the length of the clear space between supports. This information is used to determine the size of the beams and columns required to support the slab.
  4. Determine the type of slab: There are two types of flat slab systems: one-way and two-way. The type of slab required is determined based on the span and the loads that will be imposed on it.
  5. Design the beams and columns: The beams and columns that will support the slab must be designed to resist the loads that will be imposed on them. This includes determining the size, shape, and reinforcement required for each member.
  6. Design the reinforcement: The reinforcement required for the slab is determined based on the loads that will be imposed on it and the span of the slab. This includes the placement and spacing of reinforcement bars, as well as the size of the bars.
  7. Check for deflection: The final step in the design process is to check the slab for deflection. This involves calculating the maximum deflection under the design loads and comparing it to the maximum allowable deflection. If the calculated deflection is greater than the allowable deflection, additional reinforcement may be required.