A vision towards sustainable concrete prepared by Mr. G.Jein Jenish 

Concrete is the most used man-made material on earth. It forms the foundations of cities and connects communities. Without it, many of the elements of modern life we take for granted today wouldn’t be possible – safe buildings and homes, roads, tunnels and bridges, clean water, and clean energy. Concrete will also play a vital role in providing solutions to the challenges of the future and in building a sustainable world of tomorrow. Concrete has amazing sustainability benefits and we are working hard to make it even more sustainable.

Three-phase soil system

Three-phase soil system Prepared by Mr.Bright Winsley

Soil is a three-phase system consisting of solid particles (called soil grains), water, and air. The void space between the soil grains is filled partly with water and partly with air. However, if we take a dry soil mass, the voids are filled with air only. In the case of perfectly saturated soil, the voids are filled completely with water.

  

 

wind rose diagram

A wind rose diagram is a tool which graphically displays wind speed and wind direction at a particular location over a period of time. The diagrams normally comprises of 8, 16 or 32 radiating spokes, which represent wind directions in terms of the cardinal wind directions (North East South West) and their intermediate directions. Meteorologist use wind rose diagrams to summarise the distribution of wind speed and direction over a defined observation period. Data is taken from a weather station, which should be a near as possible to your project /site.

What do the Spokes Represent?

Each ‘Spoke’ shows:

1. How often the wind blows from each direction
2. How often the wind blows within each pre-defined wind speed range (bins). This is shown by the colour bands on each spoke.

A wind rose diagram uses a polar coordinate system, whereby data is plotted a certain distance away from the origin at an angle relative to north.

It is possible to create these plots using costly purpose-made software or, alternatively, very basic wind rose diagrams can be made using Microsoft Excel. Wind Rose Excel also provides 2 paid options:

1. WRE Web App – allows users to fetch data from 30,000 different weather stations and create wind rose diagrams within a web application.
2. WRE v1.7 – allow users to copy their own data into a macro-enabled excel workbook in order to produce wind rose diagrams.

 

Interpreting an Example Wind Rose Diagram

 

In Diagram 1 the westerly spoke and its colour bands provides the following information:

• The wind blows from the west (a “westerly”) 12% of the time at location x
• Westerly wind speed distribution for location x:
• 1% of total time the wind blows at 0-2 knots from the west
• 1% of total time the wind blows at 2-3 knots from the west
• 1.5% of total time the wind blows at 4-6 knots from the west
• 3.5% of total time the wind blows at 7-10 knots from the west
• 3% of total time the wind blows at 11-66 knots from the west
• 1% of total time the wind blows at 17-22 knots from the west
• 1% of total time the wind blows at >23 knots from the west

What is Possible using Excel?

 

PREFABRICATED STRUCTURES

Prefabricated construction is the practice of assembling a variety of components of a structure at a manufacturing site and transporting those sub-assemblies to the location of the construction jobsite. Prefabricated construction is sometimes thought of as a low-end and mass produced mode of construction. In reality however, it is quite the opposite. Prefabricated construction is becoming more common, improving in quality and has become available in a variety of budgets. Despite the perception of prefabrication, there are numerous benefits to this type of construction. This article assesses the advantages that prefabricated construction presents for both businesses and customers.

 

Eco-Friendly

Modular construction is often commended for energy efficiency and sustainable construction. Traditional construction methods require extra materials that lead to increased waste. However, since prefabricated sub-assemblies are constructed in a factory, extra materials can be recycled in-house. This is a considerable improvement over sending waste directly to a landfill from a traditional construction site. Also, the controlled environment of a factory allows for more accurate construction, tighter joints and better air filtration, which in turn allows for better wall insulation and an increase in energy efficiency.

Financial Savings

One of the greatest advantages of prefabricated construction would be financial savings. Although the perception of custom-made pieces may seem expensive, with prefabricated or modular construction, this is not the case. Modular construction targets all budgets and price points, creating an affordable option. Prefabrication manufacturers often receive bulk discounts from material suppliers which then trickles down to the cost of a construction project. Modular construction also sidesteps the possibility of unreliable contractors and unproductive staff. Additionally, the reduction in construction time can significantly save on construction financing costs.

Flexibility

Modular construction can be easily be disassembled and relocated to different sites. This significantly reduces the demand for raw materials, minimizes expended energy and decreases time overall. Also, modular construction allows for flexibility in the design of the structure allowing for a limitless number of opportunities. Since prefabricated construction units can be used in different spaces, its neutral aesthetics is able to blend in with almost any building type.

Consistent Quality

Since prefabricated construction occurs in a controlled manufacturing environment and follows specified standards, the sub-assemblies of the structure will be built to a uniform quality. Construction site-built structures are dependent upon varying skill levels and the schedules of independent contractors. These all contribute to the craftsmanship and overall quality of given structure. With prefabrication, each sub-assembly is built by an experienced crew in a weather-resistant factory, with multiple quality checks throughout the entire process. Some components of the building are constructed using precise machine equipment to ensure conformity to building code.

Reduced Site Disruption

Since many components of a building are completed in the factory, there is significantly less truck traffic, equipment and material suppliers around the final construction site. This limits the disruption of traditional jobsites that suffer from noise, pollution, waste and other common irritants. This streamlined approach to construction provides a far more efficient atmosphere for productivity, and eliminates unnecessary distractions and interference that are typical of construction sites.

Shorter Construction Time

Portable construction takes significantly less time to build than on-site construction. In many instances, prefabrication takes less than half the time when compared to traditional construction. This is due to better upfront planning, elimination of on-site weather factors, subcontractor scheduling delays and quicker fabrication as multiple pieces can be constructed simultaneously. Shorter construction times allows construction companies to take on multiple projects at once, allowing businesses to grow rather than putting all their focus and resources on one or a few projects at a time.

Safety

Since sub-assemblies are created in a factory-controlled environment utilizing dry materials, there is less risk for problems associated with moisture, environmental hazards and dirt. This ensures that those on the construction site, as well as a project’s eventual tenants are less likely to be exposed to weather-related health risks. Also, an indoor construction environment presents considerably fewer risks for accidents and other liabilities. There are strict factory processes and procedures that protect the worker from on-the-job injury. At a construction site, although safety is of utmost importance, workers are subjected to weather-related conditions, changing ground conditions, wind and other crew members who are at the site.

Final Thoughts

With the continued popularity of prefabricated construction, it is likely that it will only continue to grow in popularity. Customers who choose this option are able to enjoy a high quality, quicker, cost-effective, and eco-friendly construction method. Furthermore, construction companies may soon increase their investment in modular construction processes, benefiting both their business and customer relationships. Prefabricated construction is proving to be an extremely viable option, and as manufacturing technology continues to improve, expect to see its benefits and advantages rise in the future.

 STEEL CONNECTIONS

The steel structures are constructed by properly connecting the available standard sections. The connections are an important part of steel structure and are designed more conventionally than any individual members. There is a discrepancy between the actual behaviour and the analysis of steel structure is large, therefore the connections are complex to analyse and design. When the structural member fails in case of overloading then there is a general practice to prefer the individual member rather than the connections, therefore this kind of practice affects many structural members. The cost of structural steel consists of major portion of connections and that is the reason primary importance should be given to the design of connections for safety and economy of structure.

The connections are generally provided in the following cases:

• When there is the requirement to cater the heavy load and long span then the built-up sections are to be provided. In this case, this section should be connected together to get a good section.
• In case of longer span, the length of standard section needs to be connected with other section. In this case to connect the multiple sections proper design of connections are important.
• The different members need to be connected at the end (for example secondary beams to be connected to primary beam, column, footings, etc).

The classification in the connections provided in the steel structure is as follows:

• Riveted connections
• Bolted connections
• Welded connections
• Pinned connections

Shear and bending moment diagrams

Shear and bending moment diagrams are analytical tools used in conjunction with structural analysis to help perform structural design by determining the value of shear force and bending moment at a given point of a structural element such as a beam.

 Sedimentation 

Sedimentation is also called clarification. Sedimentation removes settleable solids by gravity. Water moves slowly through the sedimentation tank/basin with a minimum of turbulence at entry and exit points with minimum short-circuiting. Sludge accumulates at the bottom of the tank/basin. Typical tanks or basins used in sedimentation include conventional rectangular basin, conventional center-feed basins, peripheral-feed basin, and spiral-flow basins.

In conventional treatment plants, the amount of detention time required for settling can vary from 2 to 6 hours. Detention time should be based on the total filter capacity when the filters are passing 2 gpm per square foot of superficial sand area. For plants with higher filter rates, the detention time is based on the filter rate of 3 to 4 gpm per square foot of sand area. The time requirement is dependent on the weight of the floc, the temperature of the water, and how still the basin is. Effective sedimentation is critical to optimize pathogen removal and to enhance filter effluent quality.

A number of conditions affect sedimentation: 1) uniformity of flow of water through the basin, 2)stratification of water due to difference in temperature between water entering and water already in the basin, 3) release of gases that may collect in small bubbles on suspended solids, causing them to rise and float as scum rather than settle as sludge, 4) disintegration of previously formed floc, and 5) size and density of the floc.

Sedimentation basins are designed to provide idle conditions, such as a uniform low velocity, proper detention time, no short circuits, and no surface turbulence to the flocculated water for an effective sedimentation. Velocity varies from 1 to 3 ft/minute. Detention time (the time it takes to fill the tank) ranges from 1 to 6 hours, depending on the design of the basin. A short circuit is the flowing of incoming water through the tank, without proper stratification of the water in the basin. Short circuits are generally caused by the stratification of the water in the basin and are common during summer and winter. There should be a proper mixing and baffling of the influent with the water in the basin. Surface turbulence is due to wind action and movements of the equipment. An adequate wind-breaking height of the basin wall above the water surface and the proper maintenance of equipment are very helpful.

Sediments settle to the bottom of the basin, and the effluent is strained from the top. These basins have inlet and outlet valves for flow control, and the bottom floor slopes to a hopper (pit) for the sludge collection. Sedimentation basins are classified as primary and final sedimentation basins, according to their functions. A primary sedimentation basin receives the flocculated water and discharges it to the final sedimentation basin.