SUB-WORK / SUB CONTRACTOR

A subcontractor is a person or a company hired by a general contractor to perform part of the work of a construction job. For example, a contractor might be building a house, but might hire a firm or a person specializing in electrical engineering to install the electrical systems needed in the house. Generally the subcontractor will either relieve the main contractor of part of the building work, or will be able to perform work at lower expense or at a greater skill level than the general contractor could.

Often, a subcontractor, whether an individual or a business, forms relationships with several general contractors. The general contractor working with a subcontractor does not employ the subcontractor as a regular employee in most cases. Instead the subcontractor is either an independent contractor, or is a company that provides its employees with required benefits like health insurance coverage.

Not having to extend benefits to a subcontractor is one way that the general contractor saves money on a job. However, if problems occur because of faulty work on the part of the subcontractor, usually the general contractor is held liable for such problems. The general contractor may attempt to seek redress with the subcontractor, or have defined terms in the contract with a subcontractor stipulating that the liability would be more evenly shared.

Frequently, though, hiring a subcontractor, or several, is a way to avoid problems in construction. Specialized workers like plumbers, electricians, or people who install heating and cooling devices, often called HVAC workers, tend to have more knowledge and training in their given field. While simply building something requires training and knowledge, people who are specialists better perform certain types of work.

The subcontractor and the general contractor are served well by being able to form good working relationships with each other. For the general contractor, access to a reliable subcontractor can mean finishing jobs on time and on budget. For the subcontractor, a good reputation among contractors means greater opportunities for consistent work.

A subcontractor often holds licenses in his or her specialty field. He or she might hold a general license to conduct work in a state, and also hold advanced licensing. Such licensing implies a certain amount of hours practicing his or her trade and knowledge regarding state building codes.

In some cases, one may also refer to a person hired for a few days of work, without a specialized field as a subcontractor. Really the more accurate term is independent contractor. The person is usually a temporary employee of the contractor, hired to finish work on time, or to temporarily replace another worker who is ill. This type of subcontractor may not have a general contractor’s license but may be hired for his or her carpentry skills.

TYPES OF ESTIMATES

There are several kinds of estimating techniques; these can be grouped into two main categories:

Approximate Estimates

An approximate estimate is an approximate or rough estimate prepared to obtain an approximate cost in a short time. For certain purposes the use of such methods is justified.

Detailed Estimate

A detailed estimate of the cost of a project is prepared by determining the quantities and costs of everything that a contractor is required to provide and do for the satisfactory completion of the work. It is the best and most reliable form of estimate. A detailed estimate may be prepared in the following two ways

1. Unit Quantity Method

In the unit quantity method, the work is divided into as many operations or items as are required. A unit of measurement is decided. The total quantity of work under each item is taken out in the proper unit of measurement. The total cost per unit quantity of each item is analyzed and worked out. Then the total cost for the item is found by multiplying the cost per unit quantity by the number of units.

For example, while estimating the cost of a building work, the quantity of brickwork in the building would be measured in cubic meters. The total cost (which includes cost of materials. labour, plant, overheads and profit) per cubic meter of brickwork would be found and then this unit cost multiplied by the number of cubic meters of brickwork in the building would give the estimated cost of brickwork. This method has the advantage that the unit costs on various jobs can be readily compared and that the total estimate can easily be corrected for variations in quantities.

2. Total Quantity Method

In the total quantity method, an item of work is divided into the following five subdivisions:

1. Materials
2. Labour
3. Plant
4. Overheads
5. Profit

The total quantities of each kind or class of material or labour are found and multiplied by their individual unit cost. Similarly, the cost of plant, overhead expenses and profit are determined.

TESTING CONCRETE AGGREGATES

Samples of the fine and coarse aggregates approved by the Engineer shall be kept on the Site and shall give a fair indication of the approved quality of the aggregate for comparison with the aggregate delivered during the course of the works.

Should a sample fail to comply with any of tests, the Engineer may at his own discretion reject the batch from which sample was taken, or order it to be washed and/or screened, or permit such to be used with variations in the proportions of the concrete mixes specified, all a the Contractor’s expense. Any batch of aggregate rejected by the Engineer shall be removed from the site forthwith and replaced entirely at the Contractor’s expense.

All sample and testing of aggregates shall be carried out in accordance with ASTM C33.

Preliminary aggregate tests

As soon as the source of supply of aggregate have been approved, the Contractor shall instruct the testing agency to carry out the following tests for compliance with “Specification of Concrete Aggregates” (ASTM C33).

• Sieve analysis
• Tests for clay silt and dust content
• Tests for organic impurities
• Tests for salt content (chloride and sulphate ions)

The results of these tests shall be submitted for approval as soon as available. Test (1) and (2) with tests for the moisture content of each aggregate shall be carried out on the sample used for each trial mix.

Testing samples of aggregate

The contractors shall carry out such tests on aggregate samples as are necessary for the production of the specified concrete. The minimum incremental frequency of tests on each type of concrete used for the works shall be:

• Sieve analysis: at least once weekly
• Moisture content: at least once weekly
• Tests for clay silt and dust content: at least once fortnight
• Tests for organic impurities: at least once monthly
• Tests for salt content (chloride and sulphate ions): for every 500 cubic meters of concrete placed.

If for any reason the Engineer is not satisfied with the works concrete, he may instruct the Contractor to further increase the rate of sampling. Conversely, the rate of sampling may be reduced by the Engineer when consistent high quality been well established.

TYPES OF CONSTRUCTION

Construction is an industry method that consists of assembling or building infrastructure. It has many types such as heavy or civil construction, building construction and industrial construction. Construction works are managed by project managers and supervised by a construction engineers, construction managers, project architects or design engineers.

What is heavy Construction?

Heavy or civil construction is a procedure of adding infrastructure to the environment of a building. The builders are usually government agencies both at the local or national level. These also have legal and financial considerations. This project primarily serves the public interest. They are undertaken and supervised by some large private corporations such as power companies and whoever oversees the construction of access dams, roads and railroads.

What is Industrial Construction?

Industrial construction requires highly specialized skill in construction, planning and design. Holders of this project are normally industrial, for profit or large corporations. This corporation can be found in industries such as chemical, medicine, power generation and petroleum manufacturing.

What is building Construction?

Building construction is a process of adding small or big structures to land or real property. Most of the building construction jobs are small reconstructions like adding bathroom or reconstruction of a room. Often times, the titleholder of the property acts as a designer, paymaster and labourer for the entire job. However, all the building construction jobs include several elements in legal consideration, financial and usual design.

Building constructions are procured publicly or privately using different delivery methodologies such as management contracting, hard bid, construction management at risk, design & build bridging, and negotiated price.

Residential construction technologies, resources and practices should conform to the codes of practice and local building authority regulations. The materials used are widely accessible in the market. The common materials used are timber, stone and brick. The cost of construction is on a “per square foot” basis.This is since homes can vary significantly on local site considerations, conditions, and economies of scale.

PREFABRICATED CONSTRUCTION METHOD

Prefabricated construction is a building process in which elements or modules of the structure are prefabricated at plants, and then transported to the construction site for installation. Using this method can reduce the time of building, also saving construction cost. Prefabricated construction is now widely applied for new houses or other building structures like bridge, tunnels, culverts, water supply system.

The benefits of prefabricated construction method are from the fabrication of standard components on factory floor. This production is less time consumption compared to actual condition of construction process. The prefabricated elements are transported to the site for installing process. At the site, the modules are unloaded, moved into position with the support of heavy cranes, and assembled to form a designed building.

Together with the fast assembly, prefabricated construction also saves a lot of money on the construction project. By using standard patterns, the building materials are saved at the manufacturing factories. This help to reduce the waste in formwork and other materials that can occur during traditional building procedures.

Another considerable profit using prefabricated construction method is the energy efficiency. Because the prefab elements of a panelized home are precut, they fit snugly together, making for a tighter edifice. This means less effort for heating and cooling resulted in lower energy bills.

The rapid development of prefabricated houses has led to the increasing of construction templates that homeowners have more choice for designs of their houses. By combining these templates, it is possible to design the layout of the house, specify the dimensions of each room, and build a home that is exactly to the specification of the owners. There are also complex building plans for prefabricated constructions that can be adjusted slightly and still have the benefit of using materials of standard lengths, widths, and textures.

CONSTRUCTION EQUIPMENTS

The selection of the appropriate type and size of construction equipment often affects the required amount of time and effort and thus the job-site productivity of a project. It is therefore important for site managers and construction planners to be familiar with the characteristics of the major types of equipment most commonly used in construction.

Construction tools and other equipment

Air compressors and pumps are widely used as the power sources for construction tools and equipment. Common pneumatic construction tools include drills, hammers, grinders, saws, wrenches, staple guns, sandblasting guns, and concrete vibrators. Pumps are used to supply water or to dewater at construction sites and to provide water jets for some types of construction.

Automation of equipment

The introduction of new mechanized equipment in construction has had a profound effect on the cost and productivity of construction as well as the methods used for construction itself. An exciting example of innovation in this regard is the introduction of computer microprocessors on tools and equipment. As a result, the performance and activity of equipment can be continually monitored and adjusted for improvement. In many cases, automation of at least part of the construction process is possible and desirable. For example, wrenches that automatically monitor the elongation of bolts and the applied torque can be programmed to achieve the best bolt tightness. On grading projects, laser controlled scrapers can produce desired cuts faster and more precisely than wholly manual methods

Choice of equipment

• Size of the job: Larger volumes of excavation will require larger excavators, or smaller excavators in greater number. 
• Activity time constraints: Shortage of time for excavation may force contractors to increase the size or numbers of equipment for activities related to excavation. 
• Availability of equipment: Productivity of excavation activities will diminish if the equipment used to perform them is available but not the most adequate. 
• Cost of transportation of equipment: This cost depends on the size of the job, the distance of transportation, and the means of transportation. 
• Type of excavation: Principal types of excavation in building projects are cut and/or fill, excavation massive, and excavation for the elements of foundation. The most adequate equipment to perform one of these activities is not the most adequate to perform the others. 
• Soil characteristics: The type and condition of the soil is important when choosing the most adequate equipment since each piece of equipment has different outputs for different soils. Moreover, one excavation pit could have different soils at different stratums. 
• Geometric characteristics of elements to be excavated: A functional characteristic of different types of equipment makes such considerations necessary. 8. Space constraints: The performance of equipment is influenced by the spatial limitations for the movement of excavators. 
• Characteristics of haul units: The size of an excavator will depend on the haul units if there is a constraint on the size and/or number of these units. 
• Location of dumping areas: The distance between the construction site and dumping areas could be relevant not only for selecting the type and number of haulers, but also the type of excavators. 
• Weather and temperature: Rain, snow and severe temperature conditions affect the job-site productivity of labour and equipment.

ASHLAR MASONRY

The stone masonry in which finely dressed stones are laid in cement or lime mortar is known as ashlars masonry. In this masonry are the courses are of uniform height, all the joints are regular, thin and have uniform thickness. This type of masonry is much costly as it requires dressing of stones.

Ashlars masonry is further sub divided into the following types:

• Ashlars fine or coarse ashlar masonry 
• Random coarse ashlars masonry 
• Rough tooled ashlar masonry 
• Rock or quarry faced ashlars masonry 
• Chamfered ashlars masonry 
• Block in coarse masonry 

Ashlar fine or coursed ashlar masonry

In this type of stone masonry stone blocks of same height in each course are used. Every stone is fine tooled on all sides. Thickness of mortar is uniform throughout. It is an expensive type of stone masonry as it requires heavy labour and wastage of material while dressing. Satisfactory bond can be obtained in this type of stone masonry.

Random coursed ashlar masonry

This type of ashlar masonry consists of fine or coursed ashlar but the courses are of varying thicknesses, depending upon the character of the building. 

Rough tooled ashlar masonry

This type of ashlar masonry the sides of the stones are rough tooled and dressed with chisels. Thickness of joints is uniform, which does not exceed 6mm.

Rock or quarry faced ashlar masonry

This type of ashlar masonry is similar to rough tooled type except that there is chisel-drafted margin left rough on the face which is known as quarry faced

Chamfered ashlar masonry

It is similar to quarry faced except that the edges are bevelled or chamfered to 450 for depth of 2.5 cm or more.

Block-in coarse masonry

It is the name given to a class of ashlar masonry which occupies an intermediate place between rubble and ashlars. The stones are all squared and properly dressed. It resembles to coursed rubble masonry or rough tooled ashlar masonry.

Ashlar facing

Ashlar facing is the best type of ashlars masonry. Since this is type of masonry is very expensive, it is not commonly used throughout the whole thickness of the wall, except in works of great importance and strength. For economy the facing are built in ashlars and the rest in rubble.

3D CONCRETE PRINTING

A free form construction process using a layered manufacturing technology has been developed recently with the aim of fabricating building components and structures directly from Computer-Aided-Design (CAD) data sources. In a free form construction process, components are built up without form work unlike conventional concrete construction methods. Building materials are extruded through a nozzle as self-compacting filaments which form horizontal layers, and these layers when laid down sequentially can create large 3D building components. The free form construction process allows the following possibilities. (a) Reduce materials usage and site work; (b) produce novel internal and external finishes; (c) reduce costly remedial works; and (d) give greater design freedom. Possible applications include acoustic structures, structural insulated walls, and multifunctional cladding panels.

A high-performance printing concrete has been developed for an innovative free form construction process that utilizes digital fabrication methods for building large components. The concrete has a maximum particle size of 2 mm and contains up to 1.2 kg/m3 of polypropylene fiber The fresh concrete was successfully printed through a 9 mm diameter nozzle to build free form concrete components by layers. The fresh state of concrete had an open time of 1.5 hours to let it be printed smoothly. The average compressive strength of the cast and in-situ printed specimens were in the range of 100~110 MPa and 80~88 MPa, respectively whilst the flexural strengths were not significantly different and in the range of 12~13 MPa.

NANOTECHNOLOGY IN CONSTRUCTION

The use of nanotechnology in construction involves the development of new concept and understanding of the hydration of cement particles and the use of nano-size ingredients such as alumina and silica and other nano particles. With the help of nanotechnology, concrete is stronger, more durable and more easily placed, steel is made tougher, glass is self cleaning and paints are made more insulating and water repelling.

Two nano-sized particles that stand out in their application to construction materials are titanium dioxide (TiO2) and carbon nanotubes (CNT’s). The former is being used for its ability to break down dirt or pollution and then allow it to be washed off by rain water on everything from concrete to glass and the latter is being used to strengthen and monitor concrete. Carbon nanotubes (CNTs) are cylindrical in shape with diameter in nanometers and length can be in several millimetres. When compared to steel, the Young’s modulus of CNTs is 5 times, strength is 8 times while the densite is 1/6th times. Along the tube axis the thermal conduction is also very high. 

Titanium dioxide is widely used as white pigments. It can also oxidize oxygen or organic materials, therefore, it is added to paints, cements, windows, tiles, or other products for sterilizing, deodorizing and anti-fouling properties and when incorporated into outdoor building materials can substantially reduce concentrations of airborne pollutants. Additionally, as TiO2 is exposed to UV light, it becomes increasingly hydrophilic (attractive to water), thus it can be used for anti-fogging coatings or self cleaning windows.

Nanotechnology and Concrete 

As said in the above paragraph much analysis of concrete is being done at the nano-level in order to understand its structure using the various techniques developed for study at that scale such as Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB). The understanding of the structure and behaviour of concrete at the fundamental level is an important and very appropriate use of nanotechnology. One of the advancements made by the study of concrete at the nanoscale is that particle packing in concrete can be improved by using nano-silica which leads to a densification of the micro and nanostructure resulting in improved mechanical properties.

Nano-silica addition to cement based materials can also control the degradation of the fundamental C-S-H (calcium-silicatehydrate) reaction of concrete caused by calcium leaching in water as well as block water penetration and therefore lead to improvements in durability. Related to improved particle packing, high energy milling of ordinary portland cement (OPC) clinker and standard sand, produces a greater particle size diminution with respect to conventional OPC and, as a result, the compressive strength of the refined material is also 3 to 6 times higher (at different ages).

INTELLIGENT TRANSPORT SYSTEMS - INDIA

India, the second most populous country in the world, and a fast growing economy, is seeing terrible road congestion problems in its cities. Building infrastructure, levying proper taxes to curb private vehicle growth and improving public transport facilities are long-term solutions to this problem. These permanent solution approaches need government intervention. 

The Government of India has committed Rs.234,000 crores in the urban infrastructure sector. Bus Rapid Transit (BRT), metro rails and mono rails are being built in different cities to encourage the use of public transport. But still there is a steep growth of private vehicles. Some cities like Bangalore, Pune, Hyderabad and Delhi-NCR, with their sudden growths in the IT sector, also have a steep growth in population, further increasing transportation needs. Meeting such growth with infrastructure growth is seemingly in-feasible primarily because of space and cost constraints. Intelligent management of traffic flows and making commuters more informed about traffic and road status, can reduce the negative impact of congestion, though cannot solve it altogether. 

This is the idea behind Intelligent Transport Systems (ITS). ITS in India, however, cannot be a mere replication of deployed and tested ITS in the developed countries. The non-lane based disorderly traffic with high heterogeneity of vehicles, need the existing techniques to be adapted to the Indian scenario, before they can be used. Thus ITS in the Indian context needs significant R&D efforts.

ITS applications

Indian traffic can benefit from several possible ITS applications. One set of applications is for traffic management.

• Intersection control - At intersections, deciding the total signal cycle and the split of green times among different flows, is one of the most basic traffic management applications.
• Incident detection - Pinpointing locations of accidents or vehicle breakdown is important to handle the emergency situations.
• Vehicle classification – Knowing what kind of vehicles, and in what proportions, ply a certain road stretch, helps to choose appropriate road width and pavement materials.
• Monitoring - Pollution and road quality monitoring are necessary for taking corrective measures.
• Revenue collection - Toll taxes for infrastructure maintenance and fines for rule enforcement need to be collected.
• Historical traffic data - Long term data helps to plan new infrastructure, calibrate traffic signal times, and add public transport and so on.

Another set of applications can aid the commuters on roads. 

• Congestion maps and travel time estimates -These help commuters in route selection. 
• Public transport information - Information about arrival of public transport helps in choice of travel mode and reduces wait delays.
• Individual vehicle management - Getting information about parking places or estimates of carbon footprint help owners of private vehicles.
• Accident handling – Emergency services after accidents are a vital necessity.

Traffic congestion is an important problem in Indian cities. The characteristics of Indian roads and traffic make the problem interesting to solve. There is scope for evaluating existing ideas in different and challenging traffic scenarios, innovate new solutions and empirically evaluate ideas in collaboration with public and private sectors.

WASTE WATER TREATMENT

This post is concerned with liquid wastes as found at permanent locations. The waste water discussed in this section is predominantly of domestic origin. Varying amounts of industrial and laboratory waste waters can be collected and treated with the sanitary sewage. The primary purpose of the treatment of sewage is to prevent the pollution of the receiving waters. Many techniques have been devised to accomplish this aim for both small and large quantities of sewage.

In general, these processes are divided into three stages: preliminary (physical), primary (physical) treatment and secondary (biological) treatment. Minimally, waste water should receive primary (physical removal/settling) and secondary (biological) treatment, which can be followed by disinfection before discharge. More advanced processes (advanced or tertiary treatment) may be required for special wastes. When the effluent from secondary treatment is unacceptable, a third level of treatment, tertiary treatment, can be employed. There are many basic types of sewage treatment plants employing both primary and secondary treatment stages that are in use today for treating large quantities of sewage.

The purpose of a sewage collection system is to remove waste water from points of origin to a treatment facility or place of disposal. The collection system consists of the sewers (pipes and conduits) and plumbing necessary to convey sewage from the point(s) of origin to the treatment system or place of disposal. It is necessary that the collection system be designed so that the sewage will reach the treatment system as soon as possible after entering the sewer. If the length of time in the sewers is too long, the sewage will be anaerobic when it reaches the treatment facilities.

Sanitary sewage collection systems should be designed to remove domestic sewage only. Surface drainage is excluded to avoid constructing large sewers and treating large volumes of sewage diluted by rainwater during storms. Sewers which exclude surface drainage are called sanitary sewers, and those which collect surface drainage in combination with sanitary sewage are called combined sewers.

Except for force mains, sewers are laid to permit gravity flow of their contents. Unlike water in a water distribution system, the contents of a sewer do not flow under pressure. Usually the slope is such that a flow rate of 0.03 meter (m) per second or more is maintained when the line is flowing half full to full. This is a self-cleansing velocity and prevents solids from settling in the sewer pipes. To the maximum extent practical, sewers are laid in straight lines. Corners and sharp bends slow the flow rate, permit clogging, and make line cleaning difficult.

Removing grease from sewage is essential to the proper functioning of sewage systems. At fixed installations, grease is collected by ceramic or cast iron grease interceptors installed at kitchens and other facilities that generate grease and by concrete or brick grease traps outside the building. Approximately 90 per cent of the grease will be removed from greasy wastes by properly maintained grease interceptors and traps.

RANDOM RUBBLE MASONRY

Stone

The stone shall be of the type specified such as granite, trap, limestone, sand stone, quartzite, etc; 'and shall be obtained from the quarries, approved by the Engineer - in -Charge. Stone shall be hard, sound, durable and free from weathering decay and defects like cavities, cracks, flaws, sand holes, injurious veins, patches of loose or soft materials and other similar defects that may adversely affect its strength and appearance. As far as possible stones shall be of uniform colour, quality or texture. Generally stony shall not contain crypst crystalline silica or chart, mica and other deleterious materials like iron-oxide organic impurities etc. Stones with round surface shall not be used. The compressive strength of common types of stones shall be as per table I and the percentage of water absorption shall generally not exceed 5% for stones other than specified in table I. For laterite this percentage is 12%.

Size of stones

Normally stones used should be small enough to be lifted and placed by hand. Unless otherwise indicated, the length of stones for stone masonry shall not exceed three times the height and the breadth or base shall not be greater than three fourth the thickness of wall, or not less than 15cm. The height of stone may be up to 30cm. 

Random Rubble Masonry shall be uncoursed or brought to courses as specified. Uncoursed random rubble masonry shall be constructed with stones of sizes as referred and shapes picked up random from the stones brought from the approved quarry. tones having sharp comers or round surfaces shall, however, not be used. 

Random rubble masonry brought· to the course is similar to uncoursed random rubble masonry except that the courses arc roughly levelled at intervals varying from 30cm to 90cm in height according to the size of stones used.

Dressing

Each stone shall be hammer dressed on the face, the sides and the bed. Hammer dressing shall enable the stones to be laid close to neighbouring stones such that the bushing in the face shall not project more than 40mm on the exposed face and 10mm on the face to be plastered.

Laying

All stones shall be wetted before use. Each stone shall be placed close to the stones already laid so that the thickness of the mortar joints at the face is not more than 20mm. Face stones shall be arranged suitably to stagger the vertical joints and long vertical joints shall be avoided, Stones for hearting or interior filling shall be hammered down with wooden mallet into the position firmly bedded in mortar. Chips or sprawls of stones may be used for Filing of interstices between the adjacent stones in heartening and these shall not exceed 20% of the quantity of stone masonry. To form a bond between successive courses plum stones projecting vertically by about 15 to 20cm shall be firmly embedded in the heart erring at the interval of about one metre in every course. No hollow space shall be left anywhere in the masonry.

HIGHWAY CONSTRUCTION

The Road Construction Process

The type of road construction used varies from one job to another. The type of construction adopted for a particular road depends on: 

• The volume and nature of traffic to use road,
• The nature of the materials available, 
• The topography, 
• Foundation conditions, 
• Type and availability of construction equipment, and 
• Financing arrangements and timing.

Any road construction job consists of number of basic steps, although the relevant importance and the interaction between these steps will vary from job to job. These steps can be summarized as: 

• Planning, programming and pre-construction activities; 
• Site clearance; 
• Setting out;
• Earthworks; 
• Bridge construction; 
• Drainage structures; 
• Pavement construction; 
• Placement of road surfacing; 
• Placement of road furniture; and 
• landscaping. 

Earthworks

The eventual aim of the earthworks phase of the construction is to position the sub grade underlying the pavement layers in the right location and at the correct level, and to provide drainage. The operations to be performed are: 

• Formation of cuttings by excavating through high ground, 
• Formation of embankments by filling over low ground, formation of embankments by filling overflow ground,
• Shaping the finished surface to design levels, and 
• Excavating for drainage works. 
• The earthworks is often the largest task in the road building process and therefore careful planning and organisation are essential. Speed and efficiency depend very much upon the quantity and types of earth moving plant available earth moving plant available.
• Pavement Construction Pavement Construction
• Cement Concrete Pavements
• Manufacture: ready mixed batching plant. 
• Haulage: agitator truck. 
• Large quantities: site manufacture + normal trucks. 
• Placement: slip-form paver. 
• Compaction: internal vibrators + external screeds.

TRUSS

A truss is essentially a triangulated system of (usually) straight interconnected structural elements; it is sometimes referred to as an open web girder. The individual elements are connected at nodes; the connections are often assumed to be nominally pinned. The external forces applied to the system and the reactions at the supports are generally applied at the nodes. When all the members and applied forces are in a same plane, the system is a plane or 2D truss. The principal force in each element is axial tension or compression. When the connections at the nodes are stiff, secondary bending is introduced.

Use of trusses in single-storey buildings 

In a typical single-storey industrial building, trusses are very widely used to serve two main functions: 

• To carry the roof load
• Gravity loads (self-weight, roofing and equipment, either on the roof or hung to the structure, snow loads) 
• Actions due to the wind (including uplift due to negative pressure). 
• To provide horizontal stability: 
• Wind girders at roof level, or at intermediate levels if required 
• Vertical bracing in the side walls and/or in the gables.

Types of connections 

For all the types of member sections, it is possible to design either bolted connections or welded connections. Generally, bolted connections are preferred on site. Where bolted connections are used with bolts loaded perpendicular to their shank, it is necessary to evaluate the consequences of slack in connections. In order to reduce these consequences (typically, the increase of the deflections), solutions are available such as use of pre-stressed bolts, or limiting the hole size.

TOTAL QUALITY MANAGEMENT

To be competitive in today’s market, it is essential for construction companies to provide more consistent quality and value to their owners/customers. Now is the time to place behind us the old adversarial approach to managing construction work. It is time to develop better and more direct relationships with our owners/customers, to initiate more teamwork at the job site and to produce better quality work. Such goals demand that a continuous improvement (CI) process be established within the company in order to provide quality management. Recently CI has been referred to as Total Quality Management (TQM).

The construction industry has arrived late to TQM, probably due to the tendency to easily brush aside anything in management that is new, or to dismiss TQM as a fad. But the implementation of TQM in other industries shows clearly that the TQM is not a fad and confirm the benefits of implementing this philosophy and how much it can improve the customer satisfaction as the measure of business quality.

TQM principles and tolls in construction industry at two stages:

1. Planning and develop a conceptual design of small and large scale projects.
2. Construction and implementation of small and large scale projects.

Planning and develop a conceptual design stage

In planning and design stage it is extremely important to clearly identify the customer requirements and integrate it with the construct-ability knowledge and information to develop an effective design that meet the customer satisfaction.

Construction and implementation stage

In construction and implementation stage it is essential to implement TQM for controlling the process and reduce defects, rework, time, cost, and increase the quality of the product to meet the customer satisfaction.

TQM is not a fad and how much benefits that TQM can bring to your construction business (Improve business quality, increase customer satisfaction, reduce cost, save time and much more).

The reason that the construction industry has arrived late to TQM is that the construction professionals unaware of the TQM principles and techniques. To bring these benefits to the construction industry, more efforts must be made to spread the culture of TQM among the construction professionals and TQM courses must be in the engineering under graduated programs.

BUILDING MATERIALS

All the building structures are composed of different types of materials. These materials are either called building materials or materials of construction. It is very essential for a builder, may be an architecture or engineer or contractor, to become conversant thoroughly with these building materials. The knowledge of different types of material, their properties and uses for different purposes provides an important tool in the hands of the builders in achieving economy in material cost. The material cost in a building ranges 30 to 50 percent cost of total cost construction. In addition to material economy, the correct use of material results in better structural strength, functional efficiency and aesthetic appearance

Building stones are obtained from rocks occurring in nature and classified in three ways. 

1. Geological classification 
2. Physical classification 
3. Chemical classification

Bricks: 

Bricks are obtained by moulding clay in rectangular blocks of uniform size and then by drying and burning these blocks. As bricks are of uniform size, they can be properly arranged, light in weight and hence bricks replace stones.

Cement: 

Cement in its broadest term means any substance which acts as a binding agent for materials natural cement (Roman Cement) is obtained by burning and crushing the stones containing clay, carbonates of lime and some amount of carbonate of magnesia. The clay content in such stones is about 20 to 40 percent. Natural cement resembles very closely eminent hydraulic lime. It is not strong as artificial cement, so it has limited use in practice. Artificial cement is obtained by burning at very high temperature a mixture of calcareous and argillaceous materials in correct proportion. Calcined product is known as clinker. A small quantity of gypsum is added to clinker and it is then pulverized into very fine powder is known as cement. Cement was invented by a mason Joseph Aspdin of Leeds in England in 1824. The common variety of artificial cement is known as normal setting cement or ordinary cement or Portland cement.

Sand:

Sand is an important building material used in the preparation of mortar, concrete, etc.

Mortar: 

The term mortar is used to indicate a paste prepared by adding required quantity of water to a mixture of binding material like cement or Lime and fine aggregates like sand. The two components of mortar namely the binding material and fine aggregates are sometimes referred to as matrix the durability, quality and strength of mortar will mainly depends on quantity and quality of the matrix. The combined effect of the two components of mortar is that the mass is able to bind the bricks or stones firmly

Concrete: 

Cement concrete is a mixture of cement, sand, pebbles or crushed rock and water. When placed in the skeleton of forms and allowed to cure, becomes hard like a stone.

Timber:

Timber denotes wood, which is suitable for building or carpentry or various other engineering purposes like for construction of doors, windows, roofs, partitions, beams, posts, cupboards, shelves etc.

Metals: Metals are employed for various engineering purposes such as structural members, roofing materials, damp proof courses, pipes, tanks, doors, windows etc out of all the metals, iron is the most popular metal and it has been used in construction activity since pre-historic times.

REPAIR AND REHABILITATION

This post deals with the latest techniques in repair and rehabilitation of structures. The various causes of structural failure and the principles of rehabilitation of structures are discussed. 

A large stock of existing structures and infrastructure are deteriorated with use and time and might have passed their design life and require retrofitting and rehabilitation. The cost of retrofitting various infrastructures is estimated in the lakhs of rupees. To Overcome the ill effects caused by these deteriorated buildings Repair and Rehabilitation works are carried out from time to time. Many of the existing structures were designed to codes that have since been modified and upgraded. Change in use or higher loads and performance demands require modifications and strengthening of structural elements.

WHY DO SOME STRUCTURES FALL DOWN?

Site selection and site development errors: 

Failures often result from unwise land use or site selection decisions. Certain sites are more vulnerable to failure. The most obvious examples are sites located in regions of significant seismic activity, in coastal regions, or in flood plains. Other sites pose problems related to specific soil conditions such as expansive soils or permafrost in cold regions.

Design errors:

These failures include errors in concept; lack of structural redundancy; failure to consider a load or combination of loads; deficient connection details; calculation errors; misuse of computer software; detailing problems including selection of incompatible materials, failure to consider maintenance requirements and durability; inadequate or inconsistent specifications for materials or expected quality of work and unclear communication of design intent.

Construction errors:

Such errors may involve excavation and equipment accidents; improper sequencing; inadequate temporary support; excessive construction loads; premature removal of shoring or formwork; and non-conformance to design intent.

Material deficiencies:

While it is true that most problems with materials are the result of human errors involving a lack of understanding about materials, there are failures that can be attributed to unforeseeable inconsistencies in materials.

Operational errors:

Failures can occur after occupancy of a facility as the result of owner/operator errors. These may include alterations made to the structure, change in use, negligent overloading and inadequate maintenance.

PRINCIPLES OF REHABILITATION?

Elimination:

Remove the materials that cause damage to buildings. This is no easy matter, because everything from the floor to the roofing may contain various undesirable materials in the form of additives and admixtures.

Separation:

Some things just can't be eliminated, but can still be protected. Use sealants or foil backed drywall to separate structures from damage causing sources.

Ventilation:

Controlled, filtered ventilation may be the only way to insure that the air we bring indoors is ideal. High humidity air or extremely low humidity air can cause significant damage to concrete, plaster and brick walls.

GENERAL AREAS OF REPAIR/REHABILITATION WORK?

• Repair, removal, replacement and maintenance of mechanical supports, sanitary treatment plant and pipelines.
• Repair and modifications to diffuser ports, aeration systems, and discharge pipelines.
• Installation and maintenance of dewatering structures.
• Pile restoration and wood pile concrete encapsulation.
• Anode installation for cathodic protection.
• Repair and replacement of trash-rack and debris screen.

PROJECT MANAGEMENT

Project management is the application of knowledge, skills, tools, and techniques to project activities to meet project requirements. Project management is accomplished through the use of the following 5 processes: 

• Initiation
• Planning 
• Execution
• Controlling and
• Closure

The project team manages the various activities of the project, and the activities typically involve:

• Competing demands for: scope, time, cost, risk, and quality. 
• Managing expectations of stakeholders. 
• Identifying requirements. 

It is important to note that many of the processes within project management are iterative in nature. This is partly due to the existence of and the necessity for progressive elaboration in a project throughout the project life cycle; i.e., the more you know about your project, the better you are able to manage it. The term “project management” is sometimes used to describe an organizational approach to the management of ongoing operations. This approach treats many aspects of ongoing operations as projects to apply project management techniques to them. A detailed discussion of the approach itself is outside the scope of this document.

The project management processes common to most projects in most application areas are described here. The process interactions illustrated here are also typical of most projects in most application areas. 

• Initiating Processes: Authorizing the project or phase is part of project scope management. 
• Planning Processes: Planning is of major importance to a project because the project involves doing something that has not been done before. As a result, there are relatively more processes in this section. However, the number of processes does not mean that project management is primarily planning—the amount of planning performed should be commensurate with the scope of the project and the usefulness of the information developed. Planning is an ongoing effort throughout the life of the project.
• Executing Processes: The executing processes include core processes and facilitating processes. 
• Project Plan Execution - carrying out the project plan by performing the activities included therein. 
• Quality Assurance - evaluating overall project performance on a regular basis to provide confidence that the project will satisfy the relevant quality standards. 
• Team Development - developing individual and group competencies to enhance project performance. 
• Information Distribution - making needed information available to project stakeholders in a timely manner. 
• Solicitation - obtaining quotations, bids, offers, or proposals as appropriate.
• Source Selection - choosing from among potential sellers. 
• Contract Administration - managing the relationship with the seller. 
• Controlling Processes: Project performance must be monitored and measured regularly to identify variances from the plan. Variances are fed into the control processes in the various knowledge areas. Adjustments are made to the plan to the extent of the variances observed (i.e., those that jeopardize the project objectives). For example, a missed activity finish date may require adjustments to the current staffing plan, reliance on overtime, or tradeoffs between budget and schedule objectives. Controlling also includes taking preventive action in anticipation of possible problems. The controlling process group contains core processes and facilitating processes. 

The various interactions between core and facilitating processes are: 

• Integrated Change Control - coordinating changes across the entire project. 
• Scope Verification - formalizing acceptance of the project scope. 
• Scope Change Control - controlling changes to project scope. 
• Schedule Control - controlling changes to the project schedule. 
• Cost Control - controlling changes to the project budget. 
• Quality Control - monitoring specific project results to determine if they comply with relevant quality standards and identifying ways to eliminate causes of unsatisfactory performance.
• Performance Reporting - collecting and disseminating performance information. This includes status reporting, progress measurement, and forecasting.
• Risk Monitoring and Control - keeping track of identified risks, monitoring residual risks and identifying new risks, ensuring the execution of risk plans, and evaluating their effectiveness in reducing risk.
• Closing Processes: The following components make the closing process. 
• Contract Closeout - completion and settlement of the contract, including resolution of any open items. 
• Administrative Closure - generating, gathering, and disseminating information to formalize phase or project completion, including evaluating the project and compiling lessons learned for use in planning future projects or phase.

Project failures are all too common - some make the headlines whereas the vast majorities are quickly forgotten. The reasons for failure are wide and varied. These failures could be listed into four areas: People related or Process related or Product related or Technology related.

CONCRETE MIX

The physical properties of density and strength of concrete are determined, in part, by the proportions of the three key ingredients, water, cement, and aggregate. You have your choice of proportioning ingredients by volume or by weight. Proportioning by volume is less accurate, however due to the time constraints of a class time period this may be the preferred method.

A basic mixture of mortar can be made using the volume proportions of 1, water: 2 cement: 3 sand. Most of the student activities can be conducted using this basic mixture. Another "old rule of thumb" for mixing concrete is 1, cement: 2, sand: 3 gravel by volume. Mix the dry ingredients and slowly add water until the concrete is workable. This mixture may need to be modified depending on the aggregate used to provide a concrete of the right workability. The mix should not be too stiff or too sloppy. It is difficult to form good test specimens if it is too stiff. If it is too sloppy, water may separate (bleed) from the mixture.

Remember that water is the key ingredient. Too much water results in weak concrete. Too little water results in a concrete that is unworkable.

Suggestions: 

If predetermined quantities are used, the method used to make concrete is to dry blend solids and then slowly add water (with admixtures, if used).

It is usual to dissolve admixtures in the mix water before adding it to the concrete. Super plasticizer is an exception.

Forms can be made from many materials. Cylindrical forms can be plastic or paper tubes, pipe insulation, cups, etc. The concrete needs to be easily removed from the forms. Pipe insulation from a hardware store was used for lab trials. This foam-like material was easy to work with and is reusable with the addition of tape. The bottom of the forms can be taped, corked, set on glass plates, etc. Small plastic weighing trays or Dairy Queen banana split dishes can be used as forms for boats or canoes. 

If compression tests are done, it may be of interest to spread universal indicator over the broken face and note any colour changes from inside to outside. You may see a yellowish surface due to carbonation from CO2 in the atmosphere. The inside may be blue due to calcium hydroxide. 

To answer the proverbial question, "Is this right?" a slump test may be performed. A slump test involves filling an inverted, bottomless cone with the concrete mixture. A Styrofoam or paper cup with the bottom removed makes a good bottomless cone. Make sure to pack the concrete several times while filling the cone. Carefully remove the cone by lifting it straight upward. Place the cone beside the pile of concrete. The pile should be about 1/2 to 3/4 the height of the cone for a concrete mixture with good workability. 

To strengthen samples and to promote hydration, soak concrete in water (after it is set). 

Wet sand may carry considerable water, so the amount of mix water should be reduced to compensate. 

Air bubbles in the moulds will become weak points during strength tests. They can be eliminated by: 

1. Packing the concrete. 
2. Tapping the sides of the mould while filling the mould. 
3. "Roding" the concrete inside the mould with a thin spatula.

Special chemicals called "water reducing agents" are used to improve workability at low water to cement ratios and thus produce higher strengths. Most ready-mix companies use these chemicals, which are known commercially as super plasticizers. 

RISK MANAGEMENT

Managing risks in construction projects has been recognized as a very important management process in order to achieve the project objectives in terms of time, cost, quality, safety and environmental sustainability. However, until now most research has focused on some aspects of construction risk management rather than using a systematic and holistic approach to identify risks and analyse the likelihood of occurrence and impacts of these risks. This post aims to identify and analyse the risks associated with the development of construction projects from project stakeholder and life cycle perspectives. Based on a comprehensive assessment of the likelihood of occurrence and their impacts on the project objectives, this post identifies some major risk factors. 

Researchers found that these risks are mainly related to contractors, clients and designers, with few related to government bodies, subcontractors/suppliers and external issues. Among them, “tight project schedule” is recognized to influence all project objectives maximally, whereas “design variations”, “excessive approval procedures in administrative government departments”, “high performance/quality expectation”, “unsuitable construction program planning”, as well as “variations of construction program” are deemed to impact at least four aspects of project objectives. Researchers also found that these risks spread through the whole project life cycle and many risks occur at more than one phase, with the construction stage as the most risky phase, followed by the feasibility stage. It is concluded that clients, designers and government bodies must work cooperatively from the feasibility phase onward to address potential risks in time, and contractors and subcontractors with robust construction and management knowledge must be employed early to make sound preparation for carrying out safe, efficient and quality construction activities.

Risk Management Techniques 

• Risk Simulations and Analysis
• CPM Schedule Analysis
• Quantifying Expected Values and Modelling Risk Profiles
• Decreasing Risk Aversion
• Due Diligence

Risk Management Assessments

• Contract and Specification Requirements
• Constructability Review
• Budgetary and Final Project Costs
• Schedule Acceleration
• Change Order Identification and Approval
• Request for Information (RFI) Assessment
• Construction Methodology
• Delays and Disruptions
• Damages Assessment

As the most common and typical project types, construction projects have several characteristics such as specific objects time limit financial constraints and economic requirements, special organizational and legal conditions, complexity and systematic characteristics, For that each investment project itself is a complex system. Especially for the construction projects, there are many risk facets and complicated relations, which will influence it. The complicated relations include direct, indirect, obvious, implicit or unpredictable, What's more, the various risk factors will cause different severity of the consequences. If you do not consider these risk factors, or ignore the major factors, they all will cause damage because of decision-making errors. Quality targets, time targets, cost targets are the three objectives of project management. Especially in the construction project, the time objective is closely and inseparably related to the cost objective. Therefore, risk management of construction period is a key part in the risk management of construction

This post tells us what risks will occur during construction period. These risks have an effect on the cost and schedule of construction projects. I make my study and description mainly on the schedule. Then presenting what are the major and common risks influencing construction period that I choose from numerous factors. In the end, I got the answers like how to ensure as soon as possible how to make reasonable analysis and how to have a good control of these risks.