Reinforced Concrete Staircases Design Spreadsheet

Reinforced Concrete Staircases Design Spreadsheet

 

A stair flight is a The simplest type of staircase consists of an inclined, reinforced concrete slab. It is supported at its ends by beams, and steps are formed on its upper surface. …

The units become monolithic through the action of the reinforcing steel and site cast concrete of the column.

 

Download Link

Bending And Axial Force Spreadsheet

Bending And Axial Force Spreadsheet

 

Axial tension force can be defined as the force acting on a body in its axial direction. It’s a pulling force that will cause the body to elongate linearly in the positive direction causing a change in its dimension.

Axial–Flexual Response of Cross-Sections

The actual bending in a flexural member is about a single axis, defined earlier as the Neutral Axis, which is in line with the major principle axis. If this neutral axis happens to be parallel to one of the coordinate axes, then we call this “uniaxial” bending.

 

Download Link

What is Footing ? Types Of Footings

What is Footing ? Types Of Footings

 

Introduction:

 

Foundation is the main part of any type of structure (Buildings, bridges, tunnels…). It distributes the weight of the structure over a large area of soil, avoid unequal settlement, increase structural stability and prevent lateral movement of structure.

There are different types of soil and for each individual one, soil bearing capacity is different. So, depending on the soil profile, size and load of the structure, engineers choose different types of foundation which can be shallow foundation or deep foundation.

Shallow foundation system consists of two main types: Footings and raft or mat foundation.

Footing is one of the most important parts of a structure which transfers loads of a structure to the underlying soil.

The selection of footing depends on the following factors:

  • The depth of the soil at which safe bearing strength exists.
  • The type and condition of soil.
  • The type of the superstructure.

Types Of Footings:

 

The different types of footings used for building construction are listed below:

  • Wall footing / Strip footing
  • Spread Footings
  • Isolated Footings
  • Stepped Footings
  • Combined Footings
  • Sloped Footings
  • Strapped Footings

Wall footing / Strip footings

 

Strip footings (known as strip foundations) are a shallow foundation type, usually boasting a foundation level that is no greater than 3m from the ground surface.

Strip foundations can be used for most subsoils, but are most suitable for soil which is of relatively good bearing capacity. They are particularly suited to light structural loadings such as those found in many low-rise or medium-rise domestic buildings – where mass concrete strip foundations can be used. In other situations, reinforced concrete may be required.

Very broadly, the size and position of strip foundations is typically related to the wall’s overall width. The depth a traditional strip foundation is generally equal to or greater than the overall wall width, and the foundation width is generally three times the width of the supported wall. This results in the load being transmitted at 45º from the wall base to the soil.

Wide strip foundations may be required where the soil is soft or of a low bearing capacity, so as to spread the load over a larger area. Wide strip foundations will typically require reinforcement.

Strip footing foundation

Spread Footings

 

The spread footing is utilized to support the column & walls and additionally to convey & disseminate the load coming to the structure to the soil below it.

With loads provided within the upward direction, this footing actually acts like an inverted cantilever, and this sort of footing is typically a rigid element & they’re orthogonal just in case of symmetric footing.

As the name suggests, a spread is given under the base of the foundation so that the load of the structure is distributed on wide area of the soil in such a way that the safe bearing capacity of soil is not exceeded.

 

Isolated Footings

 

Isolated footings (also known as Pad or Spread footings) are commonly used for shallow foundations in order to carry and spread concentrated loads, caused for example by columns or pillars.

Isolated footings can consist either of reinforced or non-reinforced material. For the non-reinforced footing however, the height of the footing has to be bigger in order to provide the necessary spreading of load.

Its thickness is constant and its shape can be circular, rectangular or square. It is economic and requires less excavation but its size is highly depended on the load and it is less resistant in lateral forces.

 

Stepped Footings

 

This type of footing includes the construction of a footing step by step until it reaches the desired width. This technique is mostly used in residential buildings but its utilization has been decayed over the last decades.

The stepped footing is a simple type of isolated footing which is provided over soil having less bearing capacity. Because of low soil capacity load need to be transferred on the larger area.

Stepped footings are also used to keep metal columns away from direct contact with soil to save them from corrosion effects. This type of footing carries the load of metal columns and transmit this load to the underground.

Stepped Footing Foundation

 

Combined Footings

 

Whenever two or more columns in a straight line are carried on a single spread footing, it is called a combined footing. Isolated footings for each column are generally the economical. Combined footings are provided only when it is absolutely necessary, as

  • When two columns are close together, causing overlap of adjacent isolated footings
  • Where soil bearing capacity is low, causing overlap of adjacent isolated footings
  • Proximity of building line or existing building or sewer, adjacent to a building column.

Combined Footing Foundation

Sloped Footings

 

The strapped footings having sloping top or side faces are known as sloped footings. This type of footing is useful in the construction of formwork.

Sloped or trapezoidal footings are designed and executed with utmost attention to maintain a top slope of 45 degrees from all sides. The amount of reinforcement and concrete used in the sloped footing construction is less than that of plain isolated footing. Therefore, it decreases the utilization of concrete and reinforcement.

Sloped Footing Foundation

Strapped Footings

 

A strap footing usually supports two columns, so it’s a special type of combined footing. If a property line exists at or near the edge of an exterior column, a normal isolated footing would be placed eccentrically under this column and it would tend to tilt.

This problem may be prevented by connecting this footing with the adjacent interior footing with a strap concrete beam. The use of a strap footing may be justifiable where the distance between columns is long and a regular combined footing is impractical due to the required large excavation.

Strap Footing Foundation

 

 

 

 

 

 

 

 

 

 

What is a Retaining Wall ? Types of Retaining Walls

What is a Retaining Wall ? Types of Retaining Walls

 

Introduction:

A Retaining Wall is a structure that is designed and constructed to withstand lateral pressure of soil or hold back soil materials.

The lateral pressure could be also due to earth filling, liquid pressure, sand, and other granular materials behind the retaining wall structure.

Retaining walls are vertical or near-vertical structures designed to retain material on one side, preventing it from collapsing or slipping or preventing erosion. They provide support to terrain where the soil’s angle of repose is exceeded and it would otherwise collapse into a more natural form. The principal characteristic of a retaining wall is being able to withstand the pressure exerted by the retained material, which is usually soil.

The most important consideration in proper design and installation of retaining walls is to recognize and counteract the tendency of the retained material to move downslope due to gravity. This creates lateral earth pressure behind the wall which depends on the angle of internal friction (phi) and the cohesive strength (c) of the retained material, as well as the direction and magnitude of movement the retaining structure undergoes.

Lateral earth pressures are zero at the top of the wall and – in homogenous ground – increase proportionally to a maximum value at the lowest depth. Earth pressures will push the wall forward or overturn it if not properly addressed. Also, any groundwater behind the wall that is not dissipated by a drainage system causes hydrostatic pressure on the wall. The total pressure or thrust may be assumed to act at one-third from the lowest depth for lengthwise stretches of uniform height.

It is important to have proper drainage behind the wall in order to limit the pressure to the wall’s design value. Drainage materials will reduce or eliminate the hydrostatic pressure and improve the stability of the material behind the wall. Drystone retaining walls are normally self-draining. As an example, the International Building Code requires retaining walls to be designed to ensure stability against overturning, sliding, excessive foundation pressure and water uplift; and that they be designed for a safety factor of 1.5 against lateral sliding and overturning.

There ara various types of retaining wall structures which are used for numerous goals.

Gravity Retaining Wall :

Gravity retaining wall depends on its self weight only to resist earth pressure.

Commonly, gravity retaining wall is massive because it requires significant gravity load to counter act soil pressure.

Slidin, overturning and bearing forces shall be taken into consideration while this type of retaining  wall structure is designed.

It can be constructed from different materials such as concrete, stone and masonry units.

Crib retaining wall, gabions and bin retaining wall are types of gravity retaining walls.

Gravity Retaining Wall

Crib Retaining Wall :

Crib Retaining Walls are low cost, of open web construction and can be quickly and inexpensively erected. They can be used almost anywhere a retaining wall is needed – driveways, building sites, garden areas, and when planted out will add beauty and value to your property.

Crib walls are gravity retaining walls constructed from interlocking precast concrete components, filled with free draining material and earth backfill, eliminating the hazards of hydrostatic pressure building up behind the wall.

Crib Retaining Wall

Gabion Retaining Walls :

Gabion retaining walls are multi-celled, rectangular wire mesh boxes which are filled with rocks or other suitable materials.

It is employed for construction of erosion control structures and used to stabilize steep slopes.

Gabion Retaining Walls

Cantiliver Retaining Wall :

Cantiliver retaining wall is composed of stem and base slab and is constructed from reinforced concrete, precast concrete or prestress concrete.

Cantiliver retaining wall is the most common type used as retaining walls.

Sometimes cantilevered walls are buttressed on the front, or include a counterfort on the back, to improve their strength resisting high loads. Buttresses are short wing walls at right angles to the main trend of the wall. These walls require rigid concrete footings below seasonal frost depth. This type of wall uses much less material than a traditional gravity wall.

The portion of the base slab beneath material is termed as heel, and the other part is called toe. It is economical up to height of 10m. Similar to gravity wall, sliding, overturning and bearing pressure shall be taken into consideration during its design.

There are 3 different types of cantiliver retaining walls :

  • T – shaped cantiliver retaining wall
  • L – shaped cantiliver retaining wall
  • T – shaped cantiliver retaining wall with shear key

Cantiliver Retaining Wall

Counter-fort / Buttressed Retaining Wall :

It is a cantiliver retaining wall but strengthened with counter forts monolithic with the back of the wall slab and base slab.

Counter fort spacing is equal or slightly larger than half of the counter-fort height. It’s height ranges from 8 to 12m.

Counter-fort Retaining Wall

A buttress wall is the modified version of the counter-fort retaining wall in which the counter-forts, known as the buttresses, are provided at the other side of the backfill.

A buttress wall is more economical when compared to a counter-fort retaining wall. Buttress walls are not much preferred due to the provision of buttresses in the wall. These buttresses reduc the clearance on the front side of the wall.

Buttresses are short wing walls at right angles to the main trend of the wall. These walls require rigid concrete footings below seasonal frost depth. This type of wall uses much less material than a traditional gravity wall.

Anchored Retaining Wall :

This type of retaining wall is used when the space is limited or thin retaining wall is required.

Anchored retaining wall is suitable for loos soil over rocks. Considerably high retaining wall can be constructed using this type of retaining wall structure system.

Deep cable rods or wires are driven deep sideways into the earth, then the ends are filled with concrete to provide anchor.

Anchors (tiebacks) actes against overturning and sliding pressure.

Advantages of anchored retaining walls

  • Mostly used for slope protection and earth retaining works of deep excavations.
  • Thin walls or very light structures can be designed in combinations with anchored walls.
  • Anchored walls are one of the most economical system of earth retention.
  • Combination with sheet piles, cantilever retaining walls, piled retaining walls etc are very much useful for very deep excavations to provide a safe working area

Anchored Retaining Wall

Piled Retaining Wall :

Pile retaining wall is constructed by driving reinforced concrete piles adjacent to each other. Piles are forced into a depth that is sufficient to counter the force which tries to push over the wall.

Sheet pile walls are built using steel sheets into a slope or excavations up to a required depth, but it cannot withstand very high pressure. They are economical till height of 6m.

Piled Retainng wall

Mechanically Stabilized Earth (MSE) Retaining Wall :

It is among the most economical and most commonly constructed retaining walls. Mechanically stabilized earth retaing wall is supported by selected fills (granular) and held together by reinforcements, which can be either metallic strips or plastic meshes.

Types of MSE retaining wall include panel, concrete block and temporary earth retaining walls.

Mechanically Stabilized Earth (MSE) Walls

Hybrid Systems :

Retaining walls that use both mass and reinforcement for stability are termed as Hybrid or Composite retaining wall systems.

 

 

What is LIDAR? How it works?

What is LIDAR? How it works?

 

Introduction:

LIDAR or Light Detection And Ranging uses lasers to measure the elevation of things like the ground forests and even buildings. It is lot like sonar which uses sound waves to map things, or radar which uses radio waves to map things, but a LIDAR system uses light sent out from a laser.

For the record, there are different ways to collect LIDAR data: from the ground, from an airplane or even from space.

Airborne LIDAR data are the most commonly available LIDAR data and airborne LIDAR data will also be freely available through the National Ecological Observatory Network or NEON. Many other sources are becoming free for many countries.

The four parts of LIDAR Sytem:

To understand how lasers are used to calculate height in airborne LIDAR, we need to focus on the four parts in the system.

1. LIDAR Unit – Scans the ground:

First, the airplane contains the LIDAR unit itself which uses a laser to scan the earth from side to side as the plane flies. The laser system uses either green or near infrared light because these wavelengths or types of light reflect strongly off of vegetation.

2. Global Positioning System – Tracks planes x,y,z position:

The next component of a LIDAR system is a GPS receiver that tracks the altitude and X,Y location of the airplane.

The GPS allows us to figure out where LIDAR reflections are on the ground.

3. Inertial Measurement Unit (IMU) – Tracks Plate Position:

The third component of the LIDAR system is what’s called an inertial measurement unit or IMU.

The IMU tracks the tilt of the plane in the sky it flies which is important for accurate elevation calculations.

4. Computer – Records Data:

Finally, the LIDAR system includes a computer which records all that important height information that the LIDAR collects as it scans the earth’s surface.

 

How these four parts of the system work together to get fantastically useful later dataset?

 

The laser in the LIDAR system scans the earth actively emitting light energy towards the ground. Now before we go any farther, let us get two key LIDAR terms associated with this emitted light energy out of the way.

First, let’s define the word “pulse”. A pulse simply refers to a burst of light energy that is admitted by the LIDAR system.

And second, lets define the word “return”. Return the first reflected light energy that has been recorded by the LIDAR sensor.

Pulses of light energy travel to the ground and return back to the LIDAR sensor.

To get height the LIDAR system records the time that it takes for the light energy to travel to the ground and back. The system then uses the speed of light to calculate the distance between the top of that object and the plane.

To figure ground elevation, the plane’s altitude is calculated using the GPS receiver and then we subtract the distance that the light travel to the ground.

There are two more things in a LIDAR system to consider when calculating height. First, the plane rocks a bit in the sky as it flies due to turbulence in the air. These movements are recorded by the inertial measurement unit or IMU so that they can be accounted for when height values are calculated for each LIDAR return.

An airborne system scans the earth from side to side to cover a larger area on the ground when flying. So while some light pulses travel vertically from the plane to the ground or directly at nadir, most pulses leave the plane angle or off nadir. The system needs to account for pulse angle when it calculates elevation.

How a LIDAR system works?

The LIDAR system emits pulses of light energy towards the ground using a laser, it then records the time it takes for the pulse to travel to the ground and return back to the sensor. It converts this time to distance using the speed of light.

The system then uses the plan’s altitude, tilt, and the angle of the pulse to calculate elevation. It also uses a GPS receiver to calculate the object’s location on the ground.

All this information is recorded on that handy dandy computer also mounted on the airplane.

error: Content is protected !!
Exit mobile version