15 Jan 2019

Environmental engineering

Environmental Engineering


Environmental Engineering

Definition
                         Environmental Engineering is the branch of Civil Engineering refers to the use of scientific processes to help improve the Earth’s environment to provide healthier land, water and air for human use and to find new ways to pollution free environment. It uses the scientific and engineering principles for protection of peoples from adverse environmental effects and improve the environment for standard living.

Scope and importance

                   The scope and importance of Environmental Engineering is actually larger than one might think and largely deals with the topics that were listed above. It is broad and scope and deals with major issues such as the treatment of water and air pollution to smaller but still completely relevant issues like recycling everyday items and storing solid wastes in landfills.

                        Environmental engineers work variety of environments because of the nature of tasks. The employment of environment engineers is expected to grow from 15% to 22% by 2022. Apart from social and ecological impact, environmental engineers are also involved in protection of wildlife. They also work as consultants and provide their services to clients to protect our environment from various environmental hazards, and clean up hazardous sites.

Importance of E.Engineering

Environment Impact and Mitigation

                             Engineers and scientists apply scientific and engineering principles to evaluate if there are likely to be an adverse impact on water, air, soil, land quality, flora and fauna, ecological impact, noise impact or visual impact. The overall goal of environmental engineers is to identify, assess and evaluate the environmental impacts of man made plans, projects and laws to see if there are any affects whatsoever on water, air, habitat, agriculture, plants and animals, and the ecosystem. In this sense, environmental engineering encompasses the protection of human health and preserving the natural environment using scientific and engineering processes.

Water Supply and Treatment

                              Environmental engineers work to portable and agricultural use. It is their job to assess water within a water basin and determine supply of available water, the cycles of water movement throughout the seasons, and the treatment of water for various uses. This is done to severely minimize the risk of diseases that can be caught from the drinking and/or contact of water. This is why water distribution systems are built to meet irrigation standards for civilian use.
Water Purification
Water Pollution
                                 Water pollution is closely tied to water supply and treatment. It essentially deals with the waste put into water from sewer systems, outhouses and septics in both rural and urban areas. Environmental engineers design specific systems to carry the polluted water away from civilized areas and release the waste into the environment, most often into the ocean, and in more landlocked areas, rivers and lakes.
Polluted Water


Air Pollution Management

                         Environmental engineers design manufacturing and combustion processes to ensure the air pollutants are at acceptable levels in the atmosphere where the toxins can have minimal effects on people. These include emissions from automobile exhausts, No2, So2, organic compounds, and organic acids.
Air Pollution

Solid Waste Management

                       Solid waste management deals with solid waste materials produced by human activity, whether straightforwardly or obliquely. Solid waste management also focuses on the recovery of resources to delay the human consumption of natural resources. Different methods are used to limit the harmful solids that are released into the environment. The objective of solid waste management is to reduce the harmful effects of solid, liquid or gaseous substances on the environment.

                      Solid waste management also encompasses reuse and recycling of everyday materials, the minimization of waste, the storage and transfer of wastes, disposing of solid wastes at landfills, and policies and regulations regarding the above.

Solid Wastes


14 Jan 2019

Shear wall


Shear wall
Shear walls

Definition
                     Shear wall is a structural member in a reinforced concrete framed structure to resist lateral forces such as wind forces and earthquake forces.

OR                       Shear walls are the resistant element to the horizontal forces acting on it due to severe winds or earthquake.

Structural Mechanism of Shear Wall

                   In concrete buildings construction, a rigid vertical diaphragm capable of transferring lateral forces from exterior walls, floors, and roofs to the foundation in a direction parallel to their planes. Examples are the reinforced-concrete wall or vertical truss. Lateral forces caused by wind and earthquake, and uneven settlement loads. These forces can shear a building apart. Reinforcing a frame by attaching or placing a rigid wall inside it maintains the shape of the frame and prevents rotation at the joints. Shear walls are especially important in high-rise buildings. 
The lateral and gravity load-resisting system consists of reinforced concrete walls and reinforced concrete slabs. Shear walls are the main vertical structural elements with a dual role of resisting both the gravity and lateral loads.
Structural Mechanism of Shear wall

Types of Shear Walls

Based on type of material used, shear walls are classified into following types.
  1. Reinforced Concrete Shear Wall
  2. Concrete Block Shear Wall
  3. Steel Shear Wall
  4. Plywood Shear Wall
  5. Mid-Ply Shear Wall.

1) Reinforced Concrete Shear Wall

Reinforced concrete shear walls are widely used shear walls for residential buildings. The reinforcement is provided in both horizontal and vertical directions. But at the end of each wall, bars are closely spaced and anchored. So, the end zones of RC shear wall is called as boundary elements or barbells.
RC Shear Walls

2) Concrete Block Shear Wall

Concrete block shear walls are constructed using Hollow concrete blocks along with Steel reinforcement bars. Reinforcement is generally used to maximize the effect of concrete block masonry against seismic loads.
RC block Shear Wall

3) Steel Shear Wall

Steel shear wall consists of a steel plate wall, boundary column and horizontal floor beam. The action of steel shear wall is more like a plate girder. Steel plate wall acts as web of plate girder, boundary columns acts as flanges and horizontal beams acts as stiffeners of plate girder.
Steel Shear Wall

4) Plywood Shear Wall

Plywood shear walls are traditional type walls which are also called as timber shear walls. It consists of plywood sheets and studs. Plywood sheets transfer shear force while studs resists the tension or compression.
Plywood Shear Wall

5. Mid-Ply Shear Wall
Mid-ply shear wall is an improved version of normal plywood shear wall. In this case, extra plywood sheet is arranged at the center of normal plywood wall and series of pairs of studs are positioned on the both sides of mid-ply. Studs joint the mid-ply with outer plywood sheets standard shear walls and lateral load carrying capacity is higher for mid-ply shear walls.
Mid-Ply Shear wall
Shear Walls Location in a Building
 Structurally, the best position for the shear walls is in the centre of each half of the building.
Locationof shear walls


Limitation for Shear Walls:

  • Limitations on the use of building,
  • Adverse effects on the behavior of non-load bearing elements,
  • Degradation in the appearance of the building,
  • Discomfort for the occupants.
Generally, the relative lateral deflection in any one storey should not be more than the storey height divided by 500.
Limit for Shear Wall

Retrofitting

Retrofitting
Retrofitting Technique


Definition

               In Civil engineering  Retrofitting referred the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes.
OR
               Due to passage of time the Structure got deteriorated due to which it lose its strength and  also aesthetic view.

Intruduction

Civil engineering structures may be damaged due to various causes such as earthquakes, cyclones, blasting, etc. This kind of loading collapses the structure prematurely or causes extensive damage to them. When the damage is minor, it is possible to retrofit the structure.



 Problems in RC Structures

The following are the major types of problems observed during earthquakes in RCC frame buildings:                absence of ties in beam column joints
                inadequate confinement near beam column joint
                inadequate lap length and anchorage and splice at inappropriate position
                low concrete strength
                improperly anchored ties (90o hooks)
                inadequate lateral stiffness
                inadequate lateral strength
                irregularities in plan and elevation
                irregular distribution of loads and structural elements          

other common structural deficiencies such as soft storey effect, short column effect, strong beam-weak column connections etc.
Deteriorated Structure
RC Structures Resistance to Earthquake Enhanced by

1)      Increasing seismic capacity of the building
It increase the lateral force resistance of the building structure by increasing stiffness, strength and ductility and reducing irregularities. This can be done by two ways

i)       Strengthening of original structural members
ii)      Introduction of New structural elements  

2)      Reducing seismic response of the building
Increasing damping in the building by means of energy dissipation devices, reducing mass, or isolating the building from the ground enhance the seismic structural response. A more recent approach includes the use of base isolation and supplemental damping devices in the building.

Earthquake Resistant Structure

 RETROFIT STRATEGIES    

                   The following retrofit strategies for RC buildings are widely used after recent earthquakes in several places:

1) Jacketing

                 Jacketing of existing structural members may be of reinforced concrete, steel case or carbon fiber reinforced polymer (CFRP).

Reinforced Concrete Jacketing

                 This method involves addition of a layer of concrete, longitudinal bars and closely spaced ties on existing structural elements. The jacket increases both the flexural strength and shear strength of the column and beam.

Columns: The jacketing not only increases the flexural strength and shear strength of the column but also increases its ductility. The thickness of the jacket also gives additional stiffness to the concrete column.
Column Jacketing



Beams: Beams are retrofitted to increase their positive flexural strength, shear strength and the deformation capacity near the beam-column joints. The lack of adequate bottom bars and their anchorage at the joints needs to be addressed.

Beam and Column Jacketing

Steel Profile Jacketing


                       Steel profile jacketing refers to encasing frame elements with steel plates and filling the gap with non-shrink grout. This is generally used for improving ductility and shear strength and it provides confinement to structural element.

Columns: Steel profile jacketing of column consists of four longitudinal angles profiles placed one at each corner of the existing reinforced concrete column and connected together in a skeleton with transverse steel straps.

Beams: Steel plate reinforcement is a new technique which can be used for beams subject primarily to static loading to improve their shear strength or mid-span flexural strength.
Steel Profile Jacketing


CFRP Jacketing (Fiber Reinforced Polymer)

              Seismic resistance of frame buildings can be improved significantly by using Fiber Reinforced Polymer overlays on RC elements of the building. FRP is light weight, high tensile strength material and has a major advantage of fast implementation.

2) Addition of RC Shear Wall

                  Adding shear walls is one of the most popular and economical methods to achieve seismic protection. Their purpose is to give additional strength and stiffness to the building and could be added to existing and new buildings.

Adding Shear Wall


3) Bracing

            In this method diagonal braces are provided in the bays of the building. Diagonals stretch across the bay to form triangulated vertical frame and as triangles are able to handle stresses better than a rectangular frame the structure is also supposed to perform better. Braces can be configured as diagonals, X or even V shaped. Braces are of two types, concentric and eccentric. 
Bracing of existing Structure




12 Jan 2019

Foundations : Types, Uses, Objectives

Foundation: Types, Use, Objectives

Foundations


Definition & Introduction

                    Foundation are structural elements, which transfer loads to the soil from columns, walls or lateral loads from earth retaining structures.                   A structure essentially consists of two parts, namely the super structure which is above the plinth level and the substructure which is below the plinth level. Substructure is otherwise known as the foundation and this forms the base for any structure. Generally about 30% of the total construction cost is spent on the foundation.The soil on which the foundation rests is called the “foundation soil”.

Types of Foundation

         The two main types of foundation are :
  • Shallow foundation/Footings
  • Deep foundation

Shallow Foundation

                     Shallow Foundation are usually located no more than 6 ft below the lowest finished floor OR Depth (D) of foundation is less than or equal to its width (B). When the soil bearing capacity of soil upto low depth is sufficient to take the structure load then it is provided.


Types of Shallow foundation
  1. Isolated  spread footing 
  2. Combined footing
  3. Cantilever or strap footings
  4. Wall footings
  5. Raft or Mat foundation
Isolated Shallow Footung


Use of Shallow Foundation

            A shallow foundation system generally used when
  1.   The soil close the ground surface has sufficient bearing capacity 
  2.   Underlying weaker strata do not result in undue settlement. The shallow foundations are         commonly used most economical foundation systems.
Combined Footing



Combined Shallow footings

Deep Foundations

           The shallow foundations may not be economical or even possible when the soil bearing capacity near the surface is too low. In those cases deep foundations are used to transfer loads to a stronger layer, which may be located at a significant depth below the ground surface. The load is transferred through skin friction and end bearing.
Deep Pile Foundation

Types of Deep foundation 
  1. Pile foundation
  2. Pier foundation
  3. Types of Pile foundation :
  4. Friction pile
  5. Load bearing pile

Objectives of a foundation

  • To distribute the total load coming on the structure on a larger area.
  • To support the structures.
  • To give enough stability to the structures against various disturbing
  • forces, such as wind and rain.
  • To prepare a level surface for concreting and masonry work.
Deep Foundations

Deep Foundations



11 Jan 2019

Autocad

Autocad in Civil

 Autocad the computer program that is used in everyday life for many different projects. This article is going to show the basics of this program about use in Civil Engineering Projects. It will also show how to create a pentagon, star, and moon all connected with one another, as well as making them different colours. Civil and Architect both use it to draw 2D and 3D design of bulidings, bridges, roads etc.
Image result for Autocad 3d

Related image

Use of AutoCad in Civil

AutoCAD is widely used in the civil engineering field because of its ability to plan sites a lot easier then hand drawings. The main thing is that if you want to draft any civil engineering structure (2D, 3D) such as buildings, bridges, roads, drainage, pipeline, dams, intersection etc. with accuracy, speed and that can be easily edited, AutoCAD is the best option. I could talk for a day about the importance of AutoCAD, still may miss some of the points.

  • AutoCAD as an 2D-engineering drafting tool: You can use AutoCAD to draw accurate 2D drawings for any engineering domain and also use AutoCAD to render to 3D models to help in visualization of the end product. It helps engineers to design, analyse and solve design issues resulting in accurate designs.

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Above fig: 2D drafting of building plan, intersection and contour lines

  • 3D View: AutoCAD help model 3D objects with colors, materials and/or textures applied to various surfaces making them vivid and easier for the user to visualize the end product.

3d Design
Above fig: 3D drafting of building and bridge repectively.
  • Accuracy: AutoCAD enables you to draw with fractional dimensions and also define precision to any number of decimal places, which is not possible to achieve in hand-drafted manual drawings, hence offering accuracy in all dimensions.
  • Speed.
  • Easy to use and edit:
  • Powerful Graphics and realistic view:

Default AutoCAD Shortcuts

AutoCAD commands can often be long winded and hard to type especially if they are being used repeatedly. As such command shortcuts have been part of the software for some time now.
 Many users do not make use of them (some Keyboard Kings included). The table below shows some of the One Key Shortcuts included within the software by default:




Alias

Command

Alias

Command

Alias

Command

AARCHHATCHQQSAVE
BBLOCKIINSERTRREDRAW
CCIRCLEJJOINSSTRETCH
DDIMSTYLELLINEVVIEW
EERASEMMOVEWWBLOCK
XEXPLODETMTEXTZZOOM
FFILLETOOFFSET
GGROUPPPAN
 Default AutoCAD One Key Aliases (Shortcuts)  


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3D Design