IM-5-CONSTRUCTION-METHODS-AND-OPERATIONS PDF

**COLLEGE OF ENGINEERING** **Bayombong Campus** **DEGREE PROGRAM** **BSCE** **COURSE NO.** **CMPM** -------------------- ---------- ------------------ ---------------------------------------- ------------ ------...

**COLLEGE OF ENGINEERING** **Bayombong Campus** **DEGREE PROGRAM** **BSCE** **COURSE NO.** **CMPM** -------------------- ---------- ------------------ ---------------------------------------- ------------ --------------- ------------ --- **SPECIALIZATION** **COURSE TITLE** CONSTRUCTION METHOD PROJECT MANAGEMENT **YEAR LEVEL** **4** **TIME FRAME** **24HRS** **WK NO.** **7-8/10-11** **IM NO.** 5 I. **UNIT TITLE/CHAPTER TITLE** A. Construction Methods and Operations II. **LESSON TITLE** A. Construction Methods and Operations III. **LESSON OVERVIEW** In this chapter we discuss about the Construction Methods and Operations includes Clearing the site, Locating the structure, Earthmoving, stabilizing earth and structure, Setting Foundation, Building Superstructure, Installing Utilities, Enclosing Frame superstructures, and finishing the project. IV. **DESIRED LEARNING OUTCOMES** 1. Discuss the construction project cycle from inception, planning, execution, testing and certification. 2. Identify and interpret construction plans, working drawings, and revise contract documents, estimates and technical specifications. V. **LESSON CONTENT** **INTRODUCTION** **CONSTRUCTION METHOD** - The procedures and techniques utilized during construction. Construction operations are generally classified according to specialized fields. These include preparation of the project site, earth-moving, foundation treatment, steel erection, concrete placement, asphalt paving, and electrical and mechanical installations. Procedures for each of these fields are generally the same, even when applied to different projects, such as buildings, dams, or airports.  **TYPES OF CONSTRUCTION METHOD** 1. Traditional/Conventional Construction Method 2. Advanced/Modern Construction Method **TRADITIONAL CONSTRUCTION METHOD** **Definition** Traditional construction refers to the methods and techniques employed for centuries to build houses and other structures. In the United States, builders sometimes refer to traditional construction methods as \"brick-and-mortar.\" Some developers call traditional methods \"stick by stick.\" This terminology refers to the fact that traditional construction methods, from the early design to the building process, are hands on. **Materials** A variety of materials can be used in the traditional construction process, from concrete floor slabs to brick walls. Concrete blocks are often used in building foundations or for load bearing walls due to their high level of strength and durability. Similar to concrete blocks, lightweight aerated block, also known as aircrete block, is available. Aerated block can also be used for building foundations and walls, but has a higher level of insulation.  **Advantage** The advantage of traditional construction techniques, particularly in housing construction, but also in industrial building, is the level of uniqueness achieved. When working with an architect, a consumer has choice and freedom to modify; the architect has the option of creativity. When more modern construction techniques are utilised, most homes are built in a similar style. In the case of modular homes, the components are fabricated at a factory to be constructed on site quickly. The use of traditional construction techniques often results in a sturdier home of higher quality.  **Disadvantages** The disadvantage of using traditional methods of construction for housing and other building is that the process takes longer. The construction process is more involved and can require hiring higher-skilled designers and builders. This can add significant construction costs; materials and labour are more expensive. **MODERN CONSTRUCTION METHOD** Modern construction method is defined as those which provide an efficient product management process to provide more products of better quality in less time. It has been defined in various ways: pre-fabrication, off-site production and off-site manufacturing (OSM). http://www.bauhu.com/style/images/art/special.jpg Modern methods of construction fall into the following categories: 1\. **Off-site Manufacture (OSM):** The part of the production process that is carried out away from the building site in factory conditions. Examples include:  **2. Non Off-site Manufacture:** This approach encompasses building techniques and structural systems that cannot be placed in the category of off-site manufacture. The main characteristic of these methods is that of innovation. This could be through an innovative non OSM building technique or through the use of a method of construction that has been used in other industries, but not house building. By way of illustration, examples of non OSM include: **PROJECT MANAGEMENT** - is the application of knowledge, skills and techniques to execute projects effectively and efficiently. It's a strategic competency for organizations, enabling them to tie project results to business goals --- and thus, better compete in their markets. Project management processes fall into five groups: - Initiating - Planning - Executing - Monitoring and Controlling - Closing Importance of Project Management - Provides structure that promotes success. - Saves: money, time, & resources - Promotes good communication. - Keeps the focus on goals and outcomes. **PROJECT** is a collection of linked activities, carried out in an organized manner with a clearly defined start point and finish point, to achieve some specific results that satisfy the needs of an organization as derived from current business plan. A **project** is defined, whether it is in construction or not, by the following characteristics: \- A defined goal or objective. \- Specific tasks to be performed. \- A defined beginning and end. \- Resources being consumed. **Major Types of Construction Projects** In planning for various types of construction, the methods of procuring professional services, awarding construction contracts, and financing the constructed facility can be quite different. The broad spectrum of constructed facilities may be classified into four major categories, each with its own characteristics. 1. *Residential housing construction* includes houses and high-rise apartments. During the development and construction of such projects, the developers usually serve as surrogate owners and take charge, making necessary contractual agreements for design and construction, and arranging the financing and sale of the completed structures. Residential housing designs are usually performed by architects and engineers, and the construction executed by builders who hire subcontractors for the structural, mechanical, electrical and other specialty work. 2. *Institutional and commercial building* encompasses a great variety of project types and sizes, such as schools and universities, medical centers and hospitals, sports facilities, shopping centers, warehouses and light manufacturing plants, and skyscrapers for offices and hotels. The owners of such buildings may or may not be familiar with construction industry practices, but they usually are able to select competent professional consultants and arrange the financing of the constructed facilities themselves. Specialty architects and engineers are often engaged for designing a specific type of building, while the builders or general contractors undertaking such projects may also be specialized in only that type of building. 3. *Specialized industrial construction* usually involves very large scale projects with a high degree of technological complexity, such as oil refineries, steel mills, chemical processing plants and coal-fired or nuclear power plants. The owners usually are deeply involved in the development of a project, and prefer to work with designers-builders such that the total time for the completion of the project can be shortened. They also want to pick a team of designers and builders with whom the owner has developed good working relations over the years. 4. *Infrastructure and heavy construction* includes projects such as highways, tunnels, bridges, pipelines, drainage systems and sewage treatment plants. Most of these projects are publicly owned and therefore financed either through bonds or taxes. This category of construction is characterized by a high degree of mechanization, which has gradually replaced some labor intensive operations. **Construction Projects Participants** A. **The Owner** The owner is the individual or organization for whom a project is to be built under a contract. The owner owns and finances the project. Depending on the owners' capabilities, they may handle all or portions of planning, project management, design, engineering, procurement, and construction. The owner engages architects, engineering firms, and contractors as necessary to accomplish the desired work. **Two types of owner** 1. *Public owners* are public bodies of some kind ranging from agencies from the country level to the municipal level. Most public projects or facilities are built for public use and not sold to others. 2. *Private owners* may be individuals, partnerships, corporations. Most private owners have facilities or projects built for their own use or to be sold, operated, leased, or rented to others. B. **The Design Professionals** 1. *Architect*: An architect is an individual who plans and design buildings and their associated landscaping. Architects mostly rely on consulting engineers for structural, electrical, and mechanical work. 2. *Engineer*: The term engineer usually refers to an individual or a firm engaged in the design or other work associated with the design or construction. Design engineers are usually classified as civil, electrical, mechanical depending upon their specialty. There are also scheduling, estimating, cost, and construction engineers. a. The *structural engineer* acts as an advisor to the architect on all structural problems such as stability of the structure, suitability of materials proposed, structural feasibility of the proposed design and sizes of structural members for a construction project. In addition, the structural engineer performs structural design and supervises his or her specialist area of the construction project during production on site.  b. The *services engineers* (plumbing, electrical, heating and ventilating, air conditioning, sanitation, lifts and escalators and so on) contribute to the building design process to ensure that thermal and visual comfort are achieved effectively. For this reason, they analyze the client\'s requirement and priorities and advise the architect on the most appropriate design solution. They prepare diagrams of their proposals or services layout of the proposed construction project on the separate drawings c. The *quantity surveyor* is responsible for the study of the economies and financial implications of a construction project and, hence, he or she would be the appropriate construction professional to advise client/architect on matters relating to the economies and cost of a proposed construction project.  C. ***Engineering-Construction Firm***: An engineering-construction firm is a type of organization the combines both architect/engineering and construction contracting. This type of company has the ability of executing a complete design-build sequence.  D. **The Construction Professionals** The *Constructions Professional* are the parties that responsible for constructing the project. In traditional management where the owner, design professional, and contractors are separate companies, the contractor would be termed a *Prime Contractor*. The Prime Contractor is responsible for delivering a complete project in accordance with the contract documents. In most cases, the prime contractor divides the work among many specialty contractors called *subcontractors.* E. **The Project Manager** The Project Manager is the individual charged with the overall coordination of the entire construction program for the owner. These include planning, design, procurement, and construction. Among his/her duties: - Clear definitions of the goals of the project. - Investigate alternative solutions for the problems. - Develop a detailed plan to make the selected program reality. - Implement the plan and control the project. F. **Construction Manager** The construction manager is a specialized firm or organization which administrates the on-site erection activities and the consulting services required by the owner from planning through design and construction to commissioning. The construction manager is responsible for design coordination, proper selection of materials and methods of construction, contracts preparation for award, cost and scheduling information and control.  **Differences between Project Manager and Construction Manager** The main difference between these two roles is the level of authority. The construction manager directly oversees the day-to-day construction activities, while the project manager might supervise the construction manager. The project manager has more authority and responsibility than a construction manager typically does because he leads and motivates a team of managers or workers. The project manager oversees a project from inception to completion, while the construction manager is involved with just the construction phase. **CONSTRUCTION MANAGEMENT** *Construction management* refer to the contractual arrangement under which a firm supplies construction management services to an owner. However, in its more common use, it refers to the act of managing construction process. The construction manager, who may be a contractor, project manager, superintendent, or one of their representatives, manages the basic resources of construction. These resources include workers and subcontractors, equipment and construction plant, material, money (income, expenditure, and cash flow) and time. Poor construction management practices often result in one or more of the ff; - Project delays that increase labor and equipment cost - High material cost caused by poor purchasing procedures - Increased subcontractor cost and poor subcontractor relations - High insurances costs resulting from a poor safety record - Low profit margin or loss on construction volume. Organization for construction  **CONSTRUCTION METHOD and OPERATION** ***Project Construction Method and Operation from start to completion includes the ff:*** 1. Clearing the site 2. Locating the structure 3. Earthmoving 4. Stabilizing earth and structure 5. Setting Foundation 6. Building Superstructure 7. Installing Utilities 8. Enclosing Frame superstructures 9. Finishing the project 1. **CLEARING THE SITE** Site factors (things about the site) are important to those who prepare and clear the site. The size of the site, the amount of the natural growth, man-made and natural obstacles, the location of the site, and what is around the site are examples of important site factors. What site clearing practices are used depend upon the problem found on a particular site. The contractor must know all about the site and about site clearing practices. The [most common site clearing practices] are (1) Demolishing, (2) Salvaging, (3) Cutting, (4) Burning, (5) Earthmoving and (6) Disposing. We will look examples of these operation. **Demolishing** *Demolishing* means destroying. If we demolish by using high explosive, we call this operation blasting. When bulldozers or wrecking balls are used, it is called wrecking. Using explosive has become popular for small project in recent years. Blasting can be used both to create and to destroy. Wrecking can be done with many mechanical devices. A crowbar is a hand tool which often used by men in the wrecking field. A crawler tractor with a bulldozer blade is often used. For tall structures, a crane with a wrecking ball is used. This heavy steel metal ball hung on the end of cable is swung as a battering ram against the structure to be wrecked. **Salvaging** There are many times that the things on a site have some value and should be saved for used another project. Saving things from being demolish (destroyed) is called salvaging. This can be done by tearing down, taking apart, or removing the wanted material from the site. When a building is to be demolished, most electrical switchboards, plumbing fixtures, doors, and windows are salvage. **Cutting** Cutting has many uses. In wooded areas, cutting means bringing down timber by using axes, explosives, or saws. Cutting also can be done with torch to cut through pieces of metal. For example, old steel towers or bridges are cut this way. Special equipment can be used, when areas are cleared where were is not much timber or brush. Crawler tractors with bulldozers blades can push over trees up to 18" to 20" in diameter. When trees are not too large, two crawler tractors with a heavy steel cable connecting the two can be used. Usually a heavy steel ball is placed on the cable halfway between two tractors. The tractors, along parallel lines, pull the cable and the ball. The ball keeps the cable down close to the ground and tramples the small trees. The cable slices through the brush and pushes over small trees. **Burning** When wood cannot be used or vegetation has to be cleared, one of the best ways of destroying is by burning. This can be done by setting a fire under controlled conditions. By using special fuels, vegetation-even when green-can be set on fire. After the fire has burned everything that it can, bulldozers are used to clean up the site. **Earthmoving** Earthmoving is used in clearing many sites. In addition, earthmoving may be can a major part of the construction work on heavy construction projects such as highways, tunnels, and earthen dams. Earthmoving will be studied in a future assignment which is all about earthmoving practices. **Disposing** *Disposing* means removing from the site materials that are not wanted. Disposing may be done by burying, burning, or hauling away. **Examples of preparing and clearing** An important point to remember is that often more that one of the major operations is used to prepare and clear any one site. Sometimes there are also special problems. The following examples will give you a better understanding of many things involved in preparing and clearing. **Examples:** - To build dam, the flow of the river must be changed. - A structure being moved from its old site to a new site. - A helicopter is used to transport sections of a metal tower to a site that is hardtop reach. - A cofferdam is used to keep water from the construction site. The most popular methods are to provide caissons of cofferdams. [Caissons] are large tubes which are placed through water to solid ground. When the caisson is emptied of water, this gives a dry place for working. [Cofferdams] are a series of cells, or units, which sit on the bottom and are filled with soil and rock. These units are placed next to each other to make a wall around the site. The area within the cofferdam is then emptied of water to make a dry area. 2. **LOCATING THE STRUCTURE** [Surveyor] is the man with the training and equipment needed to do this job. Through his training and experience, and with the help of measuring equipment, he can take dimensions from a set of plans and mark on the site. A surveyor uses a measuring tape and transit to measure horizontal distances and angles. To measure vertical distance, he uses an engineer's level and a level rod. With surveying equipment, the surveyor shows construction workers the exact location and size of the structure they are build. The workers then are able to put materials in the right place to construct a building. **Surveying for highways** The first and most important part of laying out a highway is to find the correct direction. The surveyor does this by finding existing highways, trees, survey stakes already set, o other landmarks on the plans. The plans show the exact location of the highway to be built in relation to these landmarks or features. Once the surveyor has found these features, he uses them along with a transit and measuring tape, he uses them along with a transit and measuring tape to find the center line of the proposed highway. Stakes are then set along the whole center line about 50' to 100' apart. The most important along the center line are called [control points]. These usually show where two lines cross or where the center line turns. These control points are well marked with flags and stakes to keep construction equipment from running over or bumping them. All measurements are put in a notebook for future use. After the center line has been found, the surveyor measures horizontally from it to both sides and finds the edges of the pavement. The horizontal measurements needed for earthwork are then complete. The vertical measurements must then be made. There are also control points for vertical measurements as there are for horizontal measurements. These are called [bench marks]. *Bench marks* are points of known elevation or height above sea level. The location of several bench marks is shown on the plan. The surveyor uses his level and rod to find the height of the ground at each of the center line stakes. Then, by comparing the real elevations with those shown on the drawings, he can find how much cut or fill is needed to build according to the plans. The word cut means the amount of earth which must be cut away and removed to get the right elevation or height. The word fill means the earth which must be filled in to get the right height. The surveyor marks the amount of the cut or fill needed on each center line stake. The construction workers will later follow the surveyor's marks when they grade the ground. The surveyor then marks the amount of cut or fill on the stakes at each edge of the proposed pavement. The cut or fill should slope from these stakes to some point on the ground. Thus, stakes are also set at the place to where the cut or fill is to slope. These stakes are called [slope stakes] because they show the slope of the ground to be constructed. All vertical measurements are then put in a notebook for future use. When the cut, fill, and other earthwork is done, the surveyor must put up new stakes for the workers to follow while they are constructing the roadbed. This is done by beginning with the control points and setting sakes on each side of where the pavement should be. These stakes usually are set about 25' to 50' apart and 2' outside the edge of the proposed pavement. The tops of the stakes are set at the height that the finished pavement will be. The level of pavement will be at the top of the stakes. Other workers will then lay the pavement by following the surveyor's stakes. All earthwork and highway projects are surveyed in much the same way. Slope stakes are used for the earthwork, and then more stakes are put in to outline the pavement or structure to be built. **Surveying for buildings** Building plans generally show where the building will be in relation to the property line or some other feature. After the surveyor has marked where the structure is to be on site, he uses these markings to set control points. These are points from which to measure both horizontal and vertical distances. Control points are put any place where they will be safe from construction equipment. The actual layout of the building is done by using batter boards. These are made 2"x4" stakes driven part way into the ground. A board is fastened to the tops of these stakes. Then a nail is driven into the edge of this board, or a saw cut is made on the line that is being laid out. To stake a wall of a building, the surveyor locates it on drawings and then constructs batter boards beyond each end of the wall. The batter boards are placed far enough past the ends of the walls to let construction equipment work without bumping the walls. Nails are driven into each batter board or saw cuts are made where the exact line of the wall should be. Then construction workers sketch a wire or cord between the nails or saw cuts to find the wall line. The surveyor does this for each wall until the building is located. Corners are located by intersecting wires. Other marks may be put on the batter boards to mark the wall line, the foundations, or columns. Sometimes separate batter boards are constructed to mark each line. Batter boards and the marks on them must always be clearly titled to avoid confusing one batter board mark for another. Horizontal measurements and location have been described. Vertical measurements are also needed. Batter boards are usually set with the top board at a known elevation above the ground. A plumb bob then is hung from the wire which is stretched between the batter boards. Vertical measurements can be made along the plumb line. During the construction of large buildings, a surveyor looks through his transit to make sure that correct locations are maintained. The surveyor uses a level and rod to take vertical dimensions. He takes measurements from the plans and the bench mark to the actual building. The surveyor does this many times during construction, especially on multi-storeyed buildings where it is important that each floor be the right height. He may also do this to check how much the structure has settled during or after construction. Concrete dams, bridges, and many other structures are laid out in much the same way as that described for buildings. Often surveying records are kept so they can be used to check how much a project has settled or tilted. 3. **EARTHMOVING** Moving earth, both soil and rock, has always been important to man. Early man was limited in what earthmoving he could do because he relied highly on is muscle. Now man has huge pieces of machinery for earthmoving. It is now possible to do more work than was ever dreamed of by our ancestor. There many kinds of earthmoving equipment. The types range from small farm tractors with earthmoving attachments to large shovels which, in only one bite, can carry enough material to fill one railroad car. All this equipment is very much expensive to operate and maintain. Much of it is very specialized. The contractor, in many cases, will have only some pieces of basic equipment. When a job calls for special machines, the contractor goes to a sub-contractor or a leasing or rental agency who has them. Charges for rented machines are based upon the time the equipment is worked and how much it costs to bring unit to the site and to return it. **Transporting Equipment** Some earthmoving equipment is self-propelled and can be driven to the site. Other units must be hauled to the site on special flatbed trailer trucks. Still other equipment is towed to the site. The transporting of earthmoving equipment may be complicated by many conditions: (1) the distance to the site, (2) the access routes to the site, (3) the height and width of the equipment, (4) the speed of kind of wheels on the equipment, and (5) the total weight of the equipment. The limits of overhead utility lines, bridges, number of lanes of traffic, and other things to do with the road all have to be considered when moving. **Setting up Equipment** Before the equipment gets to the site, the contractor decides how he will use the machinery. All needed ramps, mats (which give support on soft soil), assembly areas, and parking aprons (used for servicing and storage) are made ready ahead of time. Once the equipment arrives, work is done very quickly. **Excavating** Earthmoving is usually done by excavating (digging) material in one area and transferring (moving) it to another place where it is either piled up, spread out, or used as fill material (disposing). Excavating is done (1) to reach a good base for a foundation, (2) to build basements, (3) to make cuts through hilly land for travel routes, and (4) to level uneven ground. Shovels, scrapers, draglines, clamshells, and hoes are some of the big machines used for this work. Tractors with special attachments, pumps, trenching machines and loaders, are some of the smaller units used. ***Excavating is classified seven basic ways:*** 1. *Bulk pit excavating*. This is the digging up of a wide and deep area. The loose material must be hauled away from the site. Access to this excavation is very limited. An example would be a basement being dug for a downtown building which is between two existing buildings. 2. *Bulk wide-area excavating*. These areas are wide but fairly shallow, and there is easy access to them. The process is mainly of levelling. An example is the grading for a highway or an airfield. 3. *Loose-bulk excavating*. The material is not hauled away, as in the above two, but it is piled into a new position. Wet clay is the type of matter that is moved. An example of this excavating practice is the way in which soil is moved in making dikes in order to form a pond. 4. *Limited-area vertical excavati*ng. This kind of excavation is done mainly by digging vertically. It may be used to dig a basement. The sides of the excavation may be braced or shored. The material is lifted up and over the sides of the excavation. 5. *Trenching*. In trenching, the excavation is long and narrow. The trench must be wide enough so that conduits, pipes, and other underground materials can be placed into it. The spoil (removed earth) is piled on the surface at the sides of the trench. It is used later to refill the trench. 6. *Dredging.* This kind of excavation deals with the removal of soil or other materials from under water. It is much the same as loose-bulk excavating. For example, this practice might be used in making harbors or river channels deeper. 7. *Tunnel excavating*. Tunnelling is not usually considered under the heading of general excavation, because it is done completely underground. Sometimes tough or dense material must be loosed before it can be excavated. The most common techniques for loosening these materials are: (1) blasting, (2) breaking, (3) scarifying, and (4) ripping. Blasting is done mostly to rock. An explosion cause, by high explosive placed as charges in special places in the material causes the rock to break into pieces. Breaking is the applying of strong blows to tear up hard materials. Air hammers are examples of breaking tools. In both the scarifying and ripping process, much tough or dense materials is loosened by running blades or teeth through it. This is like plowing. Scarifying is usually done in the upper 18" of soil. Ripping is done by pulling one or two large teeth with a tractor to loosen material down to depths of 2' to 3'. Ripping is used instead of blasting wherever ripping equipment can get the area and where materials are not too hard. New advances in heavy equipment and ripper design are making the ripper very popular in the field. Earth that is readily workable or which has been loosed is excavated. Then it is moved out of the way. **Transferring and Disposing** Excavating materials, called [spoil], are transferred or moved from one place to another. Then, they are disposed of. The spoil may be stored for reuse on the site for possible sale and later use on other sites. Spoil may be disposed of by using it for fill or top dressing. Filling is the levelling of low spots, while top dressing is the spreading of a thin coat over an area. Transferring and disposing are often some of the same equipment is used for both operations. Transferring liquid waste such as water from construction site takes different kinds of equipment and operation. Rain may cause problem such as collapsing of walls and filling of holes. Equipment may even get stuck in the mud. Pumping is a normal way to transfer water from the site. This allows work to continue. Portable sump pumps, which are operated by electrical or gasoline power, are easily lowered into the excavation. The water is pumped through lengths of piping to another location away from the working area or directly into storms sewers. On some construction sites, spoil may only be pushed or moved out of the way of the workers. This is done when the materials are to be used again on the site or when it is to be sold, dumped, or spread. A contractor will sometimes have the spoil arranged in mounds, slopes, or hills around the construction site. Topsoil might be put on it and grass and shrubs might be planted in it to make it attractive. Spoil also may be used to raise the general level of the construction site. Again, in this case, the topsoil is saved separately and used as the top layer to make landscaping easier. Spoil may also be used to fill old gravel pits, washed out trenches in the land, and other holes. 4. **STABILIZING EARTH AND STRUCTURE** **Trimming is done to make the excavation ready for the foundation** **Stabilizing is done to make the walls hold their form and to keep them from falling in. stabilizing protects men, equipment, and structures in or near the excavated area.** **Four major practices used for trimming and shaping the excavation bed and walls** 1. - remove mud from base rock. - This is done by high pressure water hosing 2. - compacting (packing), - grouting (filling with mortar), - scaling (scraping), or - filling (moving in loose earth). 3. 4. - It helps to stabilize the soil and keeps the earth from falling in. - It helps control water in the ground. **Five main ways of stabilizing earthworks** 1. 2. Common sheathing materials are metal panels and wood planks or panels. These are supported by bracing and shoring. 3. 4. Piling has two main purposes: - to improve the load-bearing capacity of the earth and - to help against uneven settlement of the structure. 1. Friction piles - support a load by the friction developed between the surfaces of the pile and the soil through which it is driven 2. End or point support piles - supports the load by having the other end rest on a firm layer of rock or earth below ground 5. 5. **SETTING FOUNDATION** **FOUNDATION** A [foundation] is the element of an architectural structure which connects it to the ground, and transfers loads from the structure to the ground. Foundations are generally considered either shallow or deep. [Foundation engineering] is the application of soil mechanics and rocks mechanics (Geotechnical Engineering) in the design of foundation elements of structures. The foundation of the structure is the part which supports the weight of the whole structure. It must cover enough area to spread the whole weight of the structure onto the earth on which it is built so that the structure will not sink into the soil. **Parts of Foundation** A foundation (substructure) can be divided into three parts; 1. The **bearing surface** (part of the earth on which the foundation rest, 2. The **footing** (flat part of the foundation which spreads the load of the structure above it, and 3. The **upright supports**, such as walls or piers. The upright supports rise above the footing to form the rest or the sub structure. **Footing** A footing is a foundation unit constructed in brick work, masonry or concrete under the base of a wall or a column for the purpose of distributing the load over a large area. A footing or a shallow foundation is placed immediately below the lowest part of the Superstructure supported by it. **Three kinds of footings** are used most often. **Spread Footings** Spread Footings are the simplest kind. They are used on bearing surfaces of rock or of soil that is packed solidly like hard clay. It is a pad which may be long and rather narrow to go under a wall, or it may be square or rectangular where it is to go under a pier or post. **Raft or Slab Footing** Where the soil of the bearing surface is soft or where there might be vibration due to an earthquake, a spread footing cannot be used. In such cases a raft or slab footing may be used. A raft footing spreads the weight of the structure over a very large area. It is used only with small, lightweight structures where the bearing surface is too soft for a spread footing. The raft footing usually covers a larger area than that of the structure it supports. **Pile Cap Footing** When the bearing surface is in marshy land, in sand, or under water as in river, lake, or along the ocean, we must find a good bearing surface. Piles are driven down through the soft or wet soil until a strong supporting layer of hard clay or rock is reached. A footing, like a spread footing, is then built on top of the piles, this footing is called a pile cap. **Foundation Materials** Different structures need different kinds of bearing surfaces, depending upon how heavy the structures are. The designer must decide what kind of bearing surface will support the weight of each structure. Today, concrete is the most common material used for footings. Sometimes only concrete is used, but It can be made stronger by burying steel rods in it for reinforcements. Most footings are horizontal. Sometimes, footings are vertical. Driven pilings are an example of vertical footings. May times vertical piers or walls are added to horizontal footings to build them up to grade level. Piers piles or foundation walls may be made of natural materials such as stone or wood. They also may be made of reinforced concrete or steel. **HOW TO SET FOUNDATION** The bearing surface is first prepared to support the footing. When the bearing surface has been prepared, the footing can be placed. Since most footings are made of concrete, let us see how they are made. Concrete footings are made in six steps. 1. Forms or molds are set in place 2. Rod setters place steel reinforcement in the forms where it is needed. 3. A mixer operator puts materials into a drum and mixes them to make concrete. 4. Concrete laborers and cement finishers place the concrete in the form, 5. The cement finishers compact the concrete in the form and finish the surface of the concrete. 6. After the concrete has set, the labourers remove the formworks. **Building Forms** **Giving Shape to Concrete** Concrete is made of stone, sand and water bound together with cement. When concrete has been freshly mixed and is still wet, we can handle it just as we would handle wet mud. Shortly, after it has been mixed, it begins to set. It finally becomes a hard as stone. In order to get the shape of the slabs, footings, walls and piers that we need, we must shape he concrete. Concrete is shaped by placing it into the forms while it is still wet. The forms of the concrete are something like the molds into which gelatin is poured. When the gelatin is set. It can be dumped out of the mold. It then has the shape of the inside of the mold. When we are shaping concrete, we do not simply pour it into the form (mold). We do not dump it out after it has become hard. Concrete must be carefully placed in the form. Also, we remove the form, piece by piece, leaving the concrete in the shape of the form. Therefore, the form must be strong enough to keep the concrete from bulging from the weight of the wet concrete. **Materials for Forms** Concrete foundation forms usually are made of wood. They also can be made of steel, or a combination of wood and steel. Wood is lighter in weight, easier to handle and less expensive than other materials. Also, It is easier to change the size and shape of wood by using hand tools unlike steel. ***Two kinds of wood or lumber used in building forms*** **1. Dimension Lumber** This is called dimension lumber because we speak the size of the piece by its dimension. **2. Plywood** This comes in large sheet 4' wide and 8' to 10' long. These sheets most commonly are ¼", ½", ¾" or 1" in thickness. They are used to cover the frame built of dimension lumber. Instead of plywood we may use a kind of dimension lumber called planking, sheating, or boards. These usually are 1", or 2" thick and may be of different widths from 4" to 12". **Preparing the Materials** The first step in building a forms is to prepare the materials. The lengths of the pieces of dimension lumber and the sizes of sheets of plywood that will be needed must be measured and cut. **Form Parts** Seven (7) main parts of a wood foundation 1. Plates 2. Studs 3. Walers 4. Ties 5. Braces or shores 6. Stakes 7. Facing  **Forms for a Slab Foundation** Forms for large slabs or for smaller spread footings are assembled in the same way. If the slab or footing is less than a foot in thickness, we may need only boards or facing materials, some stakes, and some bracing lumber. If the slab is thick, we will need all, or almost all, of seven parts of forms. **Forms for a Wall Foundation** A wall almost has the two sides. Therefore, two facings are needed inside a wall form. Sometimes, the earth forms one facing. The line for one side of the wall is marked on the concrete footing. The panels are placed in position along that line. Walers, in pairs, are nailed to the back of all the panels to keep them in line. Bracing and stakes then are put in to hold the wall in an upright position. After this one face of the form is in position, reinforcing steel is set. **Forms for a Pier Foundation** Piers may be square, rectangular, or round. Piers that are to be square or rectangular are formed with two short sets of wall forms. He forms may be built in place, or they may be prefabricated panels. When round pier is to be built, sections of metal or fiber tubes are used. These sections are assembled into what looks like a large piece of pipe. They are set in place on the footing and are plumbed so they stand straight. Then braces are used to hold them in position. **Setting Reinforcement** **Kinds of Reinforcing Steel** **1. Design Rods** -Used in wall, piers and slab foundation. **2. Reinforcing Mesh** -Mainly used in slab foundations and road slabs **Preparing Reinforcing Steel** **Placing Reinforcing Steel** In addition to concrete block supports, bent pieces of metal called chair may be used. - *High Chairs* are used where there are two levels of reinforcing steel in the same slab. They are used on the level near the top surface. - *Low Chairs* are used to support the bottom level. Because chairs are made of wire and wood to be pushed into the ground under the weight of the concrete, they cannot be used for slabs built on the ground. **Mixing Concrete** **Concrete** Concrete is made of crushed rock or gravel that is mixed with sand, Portland cement, and water. Each of these must be specially prepared before it can be used in the concrete. In addition to the basic ingredients, most modern concrete contains at least one admixture (special additive). These admixtures are used to change the basic nature of concrete. - Preparing Coarse Aggregates - Preparing Fine Aggregates - Preparing Cement - Using Admixtures - Measuring and Mixing Concrete **Preparing Coarse Aggregates** Gravel or crushed rock is used for coarse aggregate. Gravel (small stones) is found in natural deposits on the earth's surface. Crushed rock is manufactured by breaking rock into pieces into pieces into a rock crusher. Pieces of crush rock have sharp edges and may shaped much like cubes. This is the best shape for aggregate. If the rock is too soft, it will crush into powder which cannot be used. Some kinds of break up into thin, flat pieces which also should not be used for concrete. **Preparing Fine Aggregates** The sand that is used in concrete is called fine aggregate. Just as with coarse aggregate, fine aggregate has different sizes. It is graded (screened) to get the different sizes used in concrete. Generally, both the coarse aggregate and the fine aggregate are washed before being graded (sized). Washing removes particles that are too small. Rock dust or clay often found in stone or sand would be examples of such particles. The prepared aggregate is stockpiled until it is needed. **Preparing Cement** The cement used in concrete is Portland cement. Portland cement is made from a certain kind of limestone that is found in deposits under earth's surface. The limestone is quarried out of its solid deposit in pieces. Then it is crushed into a fine powder in a crusher. Some shale and clay is also crushed and mixed with the limestone in the right amounts. The mixture of limestone and clay is fed into a rotary kiln and heated at the temperature of 2700˚F. During the process, it forms a porous mass called clinker. The clinker is taken from the kiln and ground to a powder. Then a small amount of gypsum much like the lime used in masonry is added to make the Portland cement. When the Portland cement is mixed with water, it forms a paste that become firm or sets in for about two hours. After the paste sets up, it slowly becomes much harder. The setting up and the hardening of cement paste is caused by the chemical reaction between the cement and the water. This is called hydration. **Using Admixtures** Modern concrete technology has been expanded by the use of admixture or special additives which are to be found in most of the concrete placed today. Common admixtures are: - **Entraining Agents**- holds air bubbles in the concrete - **Water reducing agents**- thickens the mix - **Retarders**- slows the hardening of the mix - **Accelerators**- speeding the mix **Measuring and Mixing Concrete** When concrete is ordered to fill the forms for foundations, it is ordered by cubic yard. To find how much is needed, the dimensions or sizes of the space inside the forms are multiplied to get the volume of space in the forms. When concrete is mixed, each of the ingredients is measured or weighted in pounds. Even the water is included. The ingredients for concrete are mixed at a concrete mixing plant. The workers are able to figure the weight of the materials for any amount or kind of mix. **Placing and Finishing Concrete** - Unloading and Moving the Concrete - Placing and Consolidating the Concrete - Leveling Concrete - Floating Concrete - Finishing Concrete may be mixed on the site, at a batching plant or may even be mixed on the way to the construction site in a transit mix truck which has a large drum on it. The drum turns slowly during its trip from batching plant to the construction site to keep the concrete mixed. In unloading the concrete and placing it, every step must be carefully done to keep the heavy particles from separating from the rest of the mixture. **Unloading and Moving the Concrete** When the truck driver is ready to unload the concrete, he reverses the drum. This move the concrete out of the gate that has been opened to let the concrete flow from the truck. The truck also carries a small chute. One end of this chute fits under the gate, and concrete flows into it. The chute slopes down from the gate to the ground. At the lower end of the chute there must be a container to hold the flowing concrete. **Placing and Consolidating Concrete** In locations where the concrete is to be thick, it is placed in the layer for about 12" deep. After each layer is placed into the form, it is worked with rod or shaken by vibrator to consolidate the concrete. A vibrator is a tube that is closed at the end, about 12" in length and 2" or 3" in width. A long hose containing a flexible shaft is fastened to the open end and put over into the wet concrete. A shaft in the hose is turned by a gasoline engine or an electric motor which causes the tube or vibrator head to shake. The vibration forces the concrete tightly against the form and get rid of air bubbles. **Leveling Concrete** When all of the concrete has been placed, the concrete surface should be at the same level as the top of the form. To level the concrete, we use a straight edge rested on screeds (guides of leveling the surface). The straight edge is a long piece of wood or metal. One end of the straight edge rests on the opposite side of the form. Concrete finishers push the board back and forth over the concrete until the surface is level with screeds or top of the form. When a slab is very large, one straightedge will be too short to reach one side of the form to the other. The additional screeds must be set in between the form faces. These screeds are pieces of lumber or steel that are set parallel with one face of the form inside the area where the concrete is to be placed. The top of all the screeds are at the same level. After the concrete in the slab has been placed and has been smoothed by this process, the concrete soon sets up. When the surface is stiff but not hard, the screeds inside the form are then removed from the concrete, and the grooves they make are patched. **Floating Concrete** After the concrete has stiffened, floating is done by the cement finisher. A tool called a wood float moves back and forth over the surface until it is level and no coarse aggregates can be seen. Floating the surface is done to be sure that there is only a smooth mixture of cement, sand, and water on the surface. No coarse particle should show. After the concrete has been floated, a final finish can be put on. Sometimes, however, a float finish is used as the final finish. **Finishing** Usually a smooth finish like that found on a sidewalk is needed. A smooth finish is called a steel trowel finish. The smooth finisher makes it by moving a steel trowel back and forth over the surface. A troweled surface can also be made with a finishing machine. The finishing machine has an engine or motor that slowly turns a wheel which three or four steel trowels have been fastened. It can finish a large area in a short amount of time. The top of a foundation wall may be finished in the same way as a concrete slab. If we plan to put more concrete on top of a foundation wall, it should be left very rough on that the concrete will be able to bend or to stick to it. A float finish should be left on top of a wall if masonry, such as stone or brick is to be laid on it. For other kind of walls, we may wish to leave anchor bolts sticking up out of the top of the wall. Steel or wood for the superstructure can then be fastened to the bolts. Bolts must be put in before the concrete is placed for the foundation walls. When bolts are put into the top of a wall in a slab or in the top of the pier, they must put in very carefully. To do this, a wooden frame is nailed to the top of the form where the bolts are to be placed. Holes are drilled in the frame exactly where the bolts are needed. Since the bolts are to be anchored in the concrete, the buried part of the bolt has a hook on it. Before the concrete is placed, 2" or 3" of the bolt is pushed up through the hole which has been drilled in the frame. This part of the bolt is threaded so a nut may be put on it to hold the bolt to the frame. After the concrete has been placed and has hardened, the bolt cannot move. The nut is then taken off, and the frame is removed just before the wall forms are stripped. Nothing can be done to the other surfaces on the wall or pier until the forms have been removed. **Completing Foundations** After the concrete has been placed in the forms and the visible surfaces finished, there are still several important steps for completing of the foundation: - allowing the concrete to set - removing the forms - making sure that the concrete is properly cured and - treating the surfaces which were covered by the forms. **Allowing the Concrete to Set** Concrete is set when it will retain or hold the shape given to it by its particular form. Concrete which is set is firm, but it is not hard or strong. The amount of time needed for concrete to set depends upon the kind and amount of concrete used and the temperature and humidity during that time is in its form. However, concrete will set in 12 to 24 hours. It usually takes a much longer period of time for concrete to become hard and strong. The time needed for the concrete to become hard and strong is called the curing time. **Removing the Forms** The process of removing the forms from around the concrete is called [stripping the forms.] The workmen must not strip the forms until the concrete has properly set. In some cases, the concrete is allowed to cure before the forms are removed. Concrete which has set but has not cured is called green concrete. It is firm but not hard and strong. To strip the forms, the workers must knock the braces loose and pull out the stakes. Next, they break off the ends of the ties. Then they can separate the forms from the concrete. Using hammers, wrecking bars, nail pullers, pliers, and wrenches, the workmen then remove the walers, studs, plates and facing material. Form materials can be reused, and this reduces or lowers the cost of the foundations. The men must be very careful when they strip the forms from green concrete, because green concrete breaks and chips easily. [Curing] is the process through which the concrete becomes hard and strong. Curing is not the result of the concrete's dying out. Rather, it results from the chemical reaction of the elements within the concrete. In fact, curing will not be completed if the concrete dries out too quickly. Therefore, the concrete workers take steps to keep the concrete from drying out rapidly. They may use one of the several techniques to keep the moisture in the concrete: (1) curing with water and (2) curing with sealing membranes. Moist curing is done by spraying the concrete regularly with water or by covering the concrete with earth, sand, straw, or burlap and then keeping the covering damp. Curing with sealing membrane means that a thin, protective covering is sprayed on the surface of the concrete as soon as the forms are removed. This coating hold moisture in the concrete. Concrete must be kept moist for the first part of the 14-28 days it usually takes to properly cure it. The curing process may be speeded up with accelerators, special grades of improved cements, careful design of the mix, and by steam curing. Modern concrete technology makes it possible to produce in 24 hours or less concrete which will support 3000 psi. Because this can be done only with added expense, these techniques are saved for projects where shortening the curing time is worth the extra cost. **Treating the Formed Surface** Formed surfaces are those which touch the forms and can be seen only after the forms have been stripped. The first step that the concrete worker take in treating formed surfaces is patching holes caused by the form ties and any other defects which show in the concrete. The workers put a mixture of sand, Portland cement and water into holes and other chips which show after the forms have been removed. The final treatment depends on the location of the surface. If the surface will touch earth, it may be needed to be protected from moisture. Concrete is waterproof if a perfect job of placing and finishing is done. Usually, however, there are small defects which allow moisture to gradually seep through the concrete. Therefore, workmen waterproof the concrete by putting a layer of asphalt on the surface. Then men either brush or spray the asphalt onto the concrete. If a very durable or strong waterproofing is needed, the workers put on alternative layers of asphalt is needed. The workers put on alternate layers of asphalt and asphalt saturated paper to build up a thick coating on the concrete surface. If the surface of the concrete will not be in contact with the moisture and will be exposed to view, like the surface of the piers which support an elevated highway, it is treated in a different way. The workmen may treat the surface with a stoned finish, a sack-rubbed finish, or a special coating. To apply a stoned-finish, the workers wet the concrete surface thoroughly with water and then rub a mixture of sand, Portland cement and water over the surface. Then the surface is ground with a flat stone until it is smooth and all blemishes are removed. The concrete finishers apply a sack-rubbed finish by wetting the concrete surface, rubbing a thin mixture of sand, Portland cement and water over the surface with a piece of burlap or sponge float, and the rubbing a dry mixture of sand and cement over the same surface. Then the finishers have completed the sack-rubbed treatment, the surface has its appearance of sandpaper, but all holes have been removed. 6. **BUILDING SUPERSTRUCTURES** **Superstructures** The [superstructure] is built on top of the foundation or substructure. Towers such as those used for television broadcasting or for transmitting electricity, are mostly superstructure. The design of a superstructure depends upon the purpose for which the structure will be used. The substructure supports both the weight of the superstructure and the traffic. **KINDS OF SUPERSTRUCTURES** **1. Mass superstructures**-are made of large bodies of materials which generally cover large areas. Example of mass superstructures are earth or concrete dams and cast-in-place concrete retaining walls. Large monuments built of piled up stone, such as the pyramids of Egypt or the Washington Monument. Mass superstructures may have very little or no open space inside the mass of materials. **2. Bearing Wall Superstructures**-are made of masonry or other materials and usually built as walls, or walls and roofs. Bearing wall superstructures enclose a space. **3**. **Framed superstructures -**are those such as houses are built with a frame. The frame is like a skeleton. The parts serve the same purpose as do the bones in your body. Frames superstructures may be made of steel, reinforced concrete, or wood. The members of a frame are columns or posts with beams connecting one to another. **BUILDING MASS AND MASONRY SUPERSTRUCTURES** **Mass Construction Materials** ***Soil*** is very common and widely used construction material. It is available in large quantities and is not too expensive. Soil is used to build earth dams and other types of earth embankments. It is used to shape our highways and waterways. Even before putting down the substructure of a roadway, soil is moved, placed, and graded to give the correct slope to the road. Using soil in mass construction usually involves three steps**:** **(1) selecting good soil for the job,** **(2) excavating,** **(3) hauling,** **(4) spreading and mixing, and** **(5) compacting.** **Soil** has the proper water content in order to be packed as hard as possible. ***Rock*** can be excavated in large blocks or pieces by quarrying. *Quarrying means getting rock out of the earth.* These pieces can be used for massive or very large superstructures. Sometimes large pieces of quarried rock are needed where the shape of the block is no important. Breakwaters and jetties which slow up the erosion caused by ocean waves are superstructures made of irregular or odd-shaped blocks of stone piled loosely in a long heap. These blocks of stone can be quarried by drilling and blasting. Mass superstructures also may be built of cemented aggregates. Many kinds of aggregates and ways of cementing them are used for mass superstructures. Concrete is the most common kind of cemented aggregates. In primitive or early construction, mud and clay were held together by mixing them with straw, reeds, and brush. **Highway Superstructures** The surfaces of airports and highways are a kind of mass superstructures. To build a concrete road, the earth along it is shaped to make a foundation. The soil is compacted or pressed down until it is fairly hard. A substructure or crushed rock or gravel is then placed as a foundation. On this foundation forms are set along both sides of the strip where concrete is to be placed. These forms are made of heavy steel sheets which are bent so that the top edges are rounded like the rails of a railroad track. They are secured or fastened to the foundation surface with long steel pins driven into the earth. Another kind of roadway surface (superstructure) is made with bituminous concrete. This is a kind of cemented aggregate using crushed stone as a coarse aggregate and sand as a fine aggregate. Asphalt is used as a cementing agent instead of portland cement. ***Asphalt*** is a black tarry substance which can be found in pools or lakes on certain parts of the earth's surface. It also can be manufactured from petroleum or from coal. ***Bituminous concrete*** is prepared in mixing plants much like those used for making concrete. The aggregates are weighed and moved into a mixer on a conveyor belt. The asphalt is melted and brought to the right temperature and thickness before it is poured over the aggregates in the mixing tank. When the bituminous concrete has been mixed, it is poured into dumped trucks which take the mixture to the paving site. Bituminous concrete is usually placed in layers. The bottom layer has larger sizes of aggregates, and the top layer is made up of either small aggregates or of fine aggregates. For this reason, steel forms may not be needed along the edges of the paving. The truckload of bituminous concrete is hauled to the site and dumped into a paver. The paver spreads the bituminous concrete over the prepared road foundation surface in an even layer. Steel-wheeled rollers follow the paver and compact (pack down) the bituminous concrete while it is still warm. Rolling is continued until the bituminous concrete becomes a hardened mass with a smooth surface. **Bearing Wall or Masonry Construction** Bricks are used for building many bearing wall superstructures. However, they are not used in a large mass as brick were used in building the Tower Babel. In bearing walls small bricks are now used and each brick is carefully placed in position by masons or bricklayers. Many kind of stones of stone, solid concrete, and concrete blocks also are used to construct bearing walls. Most of the brick used to build bearing walls are 8'' long, 3 ¾ '' wide , and 2 ¼'' thick. There are six positions in which the bricklayer can place this brick in a wall, and each of these positions has a name. The positions of a brick are those the bricklayer would see looking at the front face of the wall. Brick is laid in *courses* in a bearing wall. If a brick is laid in a course in the flat position so that the 8'' dimension is along the course is 2 ¼ high, the brick is called a *stretcher*. The course is called a *stretcher course*. If we turn the brick on end so that the 8'' dimension is pointing up and down, the brick is called a ***soldier**.* If the brick is turned so that the end shows, with the 3 ¾'' along the course , the brick is called a ***header***. If the brick is then turned 90° so that the 2 1/4'' side lies along the course, it is called a *row-lock*. Two other positions in which a brick may be placed in a wall as a ***shiner*** or a ***sailor*** are not often used. Brick walls are generally built or laid up with stretcher courses. When they are only one brick wide, the walls are 3 ¾'' thick. This much of a wall is called a ***wythe***. Usually, two or three wythes are laid up together to form a bearing wall. However, often only one wythe is used to cover or put a face on a concrete or wood frame wall. Reinforced concrete walls may be used as bearing walls. They are formed and built as upward extensions, above ground, of the reinforced concrete foundations or substructures. Some of these forms arch over the entire enclosure, forming combined walls and roofs. Bearing walls can be thought of as a kind of brick aggregate cemented together by the mortar between each brick. The mortar, from ¼'' to ½'' thick, provides a bond between bricks and makes them stick together. When two wythes are built side by side to form as 8'' wall, ½'' of mortar is used between them. The mortar bonds (cements) one wythe to the other. **ERECTING STEEL FRAMES** Steel frames are generally erected at the construction site one piece at a time. Each piece of steel must be of proper size, and this preparing of each piece is usually done in a shop according to the engineer's design drawings. The steel used in a structural steel framework is made in long pieces called *shapes*. In cross section, common shapes look like the letter ''I,'' the letter ''H,'' the letter ''T,'' the block letter ''U,'' and the letter ''L.'' These long pieces of steel are cut into the lengths by power saws or by heavy shearing machines. Structural steel is often *assembled* by a subcontractor called a *structural steel erector*. He employs ironworkers to rig, handle, fasten, and plumb and brace the parts of the structural steel frame. **Rigging and Handling Steel Shapes** The columns for the lower levels of a steel frame usually are set in one piece. The beams connecting them are set by using a crane moving on wheels or crawlers. When we have a very tall building or tower to put up, a derrick is used for the higher part of the frame. The derrick is set on a level framework above the ground level. When all of the framework that can be reached by the boom at that level is finished, the derrick is taken apart and moved up to rest on the steel that has just been set. The derrick has two main parts, a mast and a boom. The mast is a tall pole that is held vertically upright by legs or by guy wires. The boom is another long pole that works like the boom on a crane. It is fastened to the bottom of the mast on a pivot joint so that it can move up or down or sideways. A piece of steel shape or an assembled section is hung from the hook and lifted into place. The steel shapes are hung on the hoisting cable by riggers who know how to safely attach the pieces. The rigging must be done so the piece will be in the correct position so it can be fastened in place. This requires special knowledge about hoisting frames, cables, and ropes, and about hand signals. The hand signals are used to tell the crane operator what to do. Often the crane operator is out of hearing range so hand signals are necessary. **Setting the Supporting Steel** Some parts of a steel frame support other parts of the frame. In a building, the columns support the beams. In a tower, the legs support the bracing that ties them together. In abridge frame, two or three beams may support all of the other beams or connecting pieces. To set up a steel skeleton, we must first set the bottom pieces of supporting steel. Anchor bolts are used to fasten the structural steel frame to the foundations. Columns for buildings or the legs of towers have a steel plate welded to the bottom of them. This is called a *base plate*. The base plate has holes drilled in it to match the position of the anchor bolts. To set the supporting pieces of steel, each piece is lifted off the truck with a crane. The base plate on the bottom is then set on the foundation so that the anchor bolts stick up through the holes in it. Base plates must be set at the correct height which may be 1'' or 2'' above the foundation concrete. The plates also must be set so they are level. To set a base plate, shims are placed between the bottom of the base plate and the concrete. Shims are small square pieces of steel plate or sheet steel. Each piece may be of a different thickness. A stack of shims is set under each of the four corners of the base plate using the thickness needed to set the base plate level and at the correct height. Then steel must be drawn down tightly against the base plate to hold it in place on the shims. **Setting the Connecting Steel** After the supporting members of a structural steel frame are set, the connecting pieces of the frame are placed. All members of the frame, whether partly assembled or not, are delivered to the site by truck or, on bridge construction, by barge. To help identify it, each piece has had a number mark on it at the steel shop. Using the numbers shown on the sop drawing, the foreman of the iron workers selects the right piece of section. A crane with a double sling of wire rope with a hook on each end is used to lift the piece. The two legs of the sling meet in a steel ring at the center. The hook on the lifting line of the crane is hooked into this ring, and the piece is lifted. To guide the piece or section of steel, a length of fiber rope is tied to one end. This is called a ***tag line***. **Fastening Steel Shapes** Each ironworker carries a ***spud wrench*** which is stuck into a holder on a leather belt. The spud wrench has jaws on one end that fit around a nut or the head of a bolt. The other end is a handle 12'' to 18'' long that tapers down to a rounded point. When one hole in the beam is lined up with the correct hole in the connecting piece, he pushes the point of the wrench handle through the two holes. This also lines up the other holes in the connection. The ironworker then takes bolts from a small pouch hanging from his belt and puts them through all the holes of the connection. He puts nuts on the threaded ends of the bolts and pulls the two pieces of steel together by turning the nut with the jaws of the spud wrench. An ironworker at the other end of the beam does the same thing at the same time. All connections between parts of a structure steel frame are made in the same way. The bracing pieces between the legs of a tower are connected between the columns of a building. Each piece in the frame for a bridge also is placed in this way. When sections have been assembled in a yard and hauled to the site, one section is connected to another in this way. After the pieces or sections are fastened together with bolts, they must be riveted, bolted, or welded together permanently, a torque wrench operates something like a very slow electric drill. It turns the nut down hard on the bolt until the two pieces of steel are pressed tightly together. If the frame is to be welded together, welding is done around the edges of the connecting pieces. **Plumbing and Bracing** Before the final riveting, bolting, or welding can be done, the first part of the frame to be braced must be leveled, plumbed, and then held in position with guy wires. Guy wires are made of steel wire rope. In a building frame, they may be fastened from the bottom of one column to the top of another column. Guy wires also may be fastened from the upper part of a column to a long iron stake driven into the ground some distance away from the column. The columns are plumbed by hanging a plumb bob from a string beside the column. When the face of the column lines up with the string, the column is plumb. The number or thicknesses of the shims under the base plate have to be changed to tilt the column until it is plumb. When the first part of the framework has been plumbed, leveled, and temporarily braced with guy wires, grout is forced in around the shims between the base plate and the concrete foundation. Grout is a mixture of sand and cement with very little water added to it. The grout will set up, like concrete, and hold the base plate in place. When the steel for the top of the structure has been set in place, the structure said to be ''topped out''. **ERECTING CONCRETE FRAMES** ***Materials for a Concrete Frame*** Concrete for the frames of superstructures is made in the same way as the concrete used in foundations. The only difference is that stronger concrete is needed. The strength is measured by how heavy a load it can support after it has hardened for 28 days. Concrete used in foundations is strong enough if it can support a weight of 2,000 pounds on each square inch of its surface. The concrete used in frames made by putting more cement into the same quantity of sand and gravel. ***Concrete Columns and Walls*** Concrete columns are also anchored to the foundation but in a different way. Pieces of reinforcing steel called dowels are placed in the foundation concrete so that they will stick up where the column is to be built. Around these dowels, the surface of the foundation concrete is left rough so that the concrete in the column will bond the concrete in the foundation. The long reinforcing bars that are used in the column are tied to the dowels with wire. The long bars are then held in place with hoops of smaller steel bars the same way that they were in the building of foundation piers. The panels are fastened together with short pieces of waler that are overlapped at the corners and nailed to each other. Panels also may be fastened together with metal bars called *column clamps*. Sometimes form ties may be used. The forms are plumbed and braced just as the pier forms were. Round columns use curved metal forms like those used for piers. ***Concrete Beams*** The connecting pieces for a concrete frame may be of any size or shape but they are called *beams*. They may connect columns, two pieces of wall, or a column and a piece of wall. Column or wall forms are built up to the level of the beams, and then the beam forms are built before any concrete is placed. The concrete is placed into the columns and the beams at the same time so they will be formed together. All of the concrete that was placed for the foundations was supported on a bearing surface or on a footing. Concrete beams are suspended in the air. The forms for the beams and the concrete has hardened and can support itself. Across the top of each shore is nailed or fastened a piece of lumber at right angles to the line of the beam. This piece is 24'' to 30'' longer than the width of the bottom of the beam. It is braced to the shore underneath with diagonal braces. **Fabricating the Beam Form** The form for a concrete beam is aide with a beam bottom and two beam side pieces. These are made from 2'' thick dimension lumber and are cut to the necessary width or height. The line of the beam has been marked on top of each 4'' x 4'' that rests on the shores. The beam bottom is nailed to the top of each 4'' x 4'' along that line. Then the beam sides are nailed to the beam bottom on each side. Each 4'' x 4'' will stick out beyond the beam sides about 12'' or 15''. The beam side is then braced to the outside of the 4'' x 4''. After the beam is formed, the reinforcing steel is set. The reinforcing steel bars in beams are called trussed bars. The same bar is bent so thath the central part of it is close to the bottom of the beam. Toward the ends the bar bends up on 45⁰ angle so that the ends are near the top of the beam. On the end of each bar, there is a large hook into the steel in the column. These bars may be fastened together with smaller bars like the hoops in a column. **Fabricating Suspended Slab Forms.** To build a slab form, we will start by placing shores every 4' in rows, and place a 4'' x 4'' on top of each row of shores. The 4'' x 4'' is called a stringer. At right angles to the 4'' x 4'', we will place a 2'' x 4'' or 2'' x 6'' every 16'' from one end of the slab to the other. These will be stood on edge and nailed to the stringers. These pieces are called joists. Over the joists, we will nail sheets of plywood to form the facing for the underside of the concrete slab. Where the slabs meets the beam, the beam side is cut down so that the plywood can be nailed to the top of it. The reinforcing steel for the slab is set on the plywood. These are straight bars set at intervals of 4'', 6'', or 8'' in both directions. The bars are fastened together where they cross. To keep them above the bottom of the concrete slab, they are set on small wire supports, called chairs, that rest on the plywood surface. **Placing the Concrete** Concrete is placed in forms for the frame of a structure in much the same way it was placed in the foundation. The concrete is placed in the column forms a short time before the concrete is placed in the forms for the beams and slabs. Concrete shrinks a little as it sets up. We let this shrinkage take place before the other concrete is placed. If the structure is not very high, we may place the concrete by using a crane with a long boom. A concrete bucket is hung from the hook on the lifting cable. For taller structures, we may have to use a hoists. A hoists is like an elevator in a tall building. **Finishing Concrete Frames** Some of the concrete surfaces in a structural concrete frame may be left exposed when the structure is finished. These surfaces will be finished in the same ways that were described for foundation concrete. The top surfaces of concrete slabs will usually be given a smooth, steel trowelled finish so that the tile or other flooring can be put over them. Generally, The columns, the underside of concrete slabs, and many of the beams will be covered by other surfacing materials and will not need to be finished by rubbing or trowelling. **Placing Concrete Shapes** Some parts of a concrete frame can be made in a manufacturing plant and hauled to the site for erection. These pieces are called precast concrete shapes. They are made of the same kind of concrete, but instead of using wood for the forms, metal is used. Concrete placed in foundations or in concrete frames is cured by wetting or coating it with curing compounds. Precast concrete is cured at the manufacturing plant with steam. Some precast concrete shapes are called prestressed concrete. Prestressed concrete is not reinforced with reinforcing rods such as those used in other kinds of concrete. It uses wires for reinforcing the concrete. Like the wires on a violin, these wires are stretched very tightly and then the concrete is poured in the forms around them. Instead of making a concrete slab when the concrete is placed, precast or prestressed concrete slabs or planks in 2' or 3' width can be used. The ends of these planks are supported on the concrete beams. Precast concrete shapes may be beams for highway bridges, slabs for steel or concrete frames, or T-beams for roofs or structures. **Building Wood Frames** Generally wood frames are used for small buildings such as houses. The frames(skeleton) for these buildings may be subdivided into three major parts: 1\. **Floor framing** Most floor framing is made up of horizontal members which are called joists. 2\. **Wall framing** Most wall framing is made up of vertical members which are called studs. 3\. **Roof framing** Most roof framing is made up of sloped members which are called rafters. The ***major steps in erecting wood frames at the site*** are: 1. Laying out and marking the locations and position of the framing members according to the blue print 2. Marking off the lengths of lumber, 3. Sawing the lumber, 4. Assembling the parts, and 5. Levelling and plumbing the frames **Setting Sills** To secure and hold wood framing to the foundation an anchor bolt is first set every 5' or 6' along the centre of the footing or wall. To begin construction of the frame, a sill is laid on top of the foundation. The sill is a horizontal piece of lumber and is the bottom piece of the frame. Holes are marked and drilled in the sill so that the sill can drop down over the anchor boards. A thin layer of grout, which is a mixture of sand, cement, and water, maybe placed under the sill to help level it. After the sill is levelled, it is held in place by tightening knots down on the threads of the anchor bolts. **Assembling Joists** Joists are planks set on edge. They are placed to give a base on which the flooring materials can rest. Joist rest on sills and extend from one foundation wall to the foundation wall on the other side. **Assembling Girders** When the distance between two foundation walls is great, a girder maybe used to support the joist. A girder is stronger than the joist used in a frame. **Laying Subflooring** A subfloor is nailed to the top of the joists. Because a second is always placed on top of it, this floor is called the rough flooring or subflooring. Boards or pieces of ply woods are used for the sub flooring. The boards have tongues and groove of the next boards. This keeps the boards from twisting and makes a tighter floor. 7. **INSTALLING UTILITIES** Utilities are services such as water, waste disposal, electricity, gas, and communications. Utilities need to be installed in many structures in order for them to serve the purpose for which they were constructed. The utility systems which provide the services also require much construction. Utilities are a part of and service almost all constructed works. For example: 1. Tunnels must be lighted and ventilated. 2. Highways need traffic controls and drainage for raising or opening them. 3. Bridges may need lighting and controls Most utility installation work is in connections with buildings. In many modern buildings, the cost of installing the utilities is more than the cost of the rest of the building. Utilities are installed both inside and outside buildings. For instance, all the electric power equipment which is outside a building is considered an ''outside utility.'' The wiring system within the building is an ''inside utility.'' Usually the electric power company provides the outside electrical system. The building owner, through the general contractor and the electrical subcontractor, provide the inside wiring system. In describing utilities, we shall assume that we have a building provided with ff basic utilities: 1. Water 2. Waste disposal system, 3. Electricity for lighting and air conditioning, 4. Gas to heat the building and to heat water, and 5. Communication like Telephone service, Internet and TV cable services The equipment, supplies, and labour for these utilities may be from one-third to two-thirds of the entire cost of a building. Thus, the architect or engineer designing the utilities systems has a job almost as bid as the task of designing the rest of the structure. **Water** A city usually draws its water from a river, a reservoir, or a system of wells. The water is pumped through an underground pipeline (a pipe of large diameter). After being purified, it is piped throughout the city in pipes of various sizes. These pipes, called ***water mains***, usually are laid beneath the streets. **Sewerage** A system of pipes which carries off excess or waste water. One branch of the system is called a *sewer*. There are two types. **(1) sanitary sewers and (2) storm sewers.** **Sanitary Sewers** Sanitary sewers carry waste water (sewage) away from plumbing fixtures and into sewer pipe leading from our imaginary building. This pipe is ''tapped'' into a city sewer man which usually lies under or close to a street. The sewer mains lead to a city sewage treatment plant. There the waste water is purified and discharged, usually into a stream. **Storm Sewers** Water falling as rain or snow on the roof of our building runs into gutters and downspouts. It is carried into a system of storm sewers which also drain water from the streets. **Electricity** Electricity is a form of energy. It involves the movement of electrons. Ordinary electric current is a controlled flow of electrons through a wire or other conductor. Power plants generate electric current by converting the energy of falling water, atomic fission or fossil fuels to electrical energy, or electricity. The fossil fuels include coal, petroleum, and natural gas. ***Voltage*** is a measure of the electrical force needed to push electric current through wires. Electric current is transmitted from a power plant at high voltage, in wires held up by high steel towers. When the electricity reaches the city, a transformer reduces the voltage. A transformer reduces the electrical force in the line. The electric power is then distributed throughout the city in wires strung on poles or buried underground. Underground wires usually are placed in a duct or conduit. Just before the power reaches our imaginary building, it goes to another transformer to lower the voltage to 240 volts. The utility company install a drop (made up of 3 wires) leading from the transformer to the building. Upon reaching the building, the wires are pulled through a metal conduit (pipe) to a meter. From the meter, the wires are connected t a fuse (circuit breaker) box. Workmen employed by the electrical subcontractors install the "inside utility". From the fuse box, they put wires in conduit or use flexible cable to distribute the power to all lighting fixtures, to air conditioning and heating equipment, and to all floor and wall outlets. **Gas** Some fuel gas is manufactured, but a great deal exists in a natural form underground. Most gas used today is natural gas produced by wells in certain parts of the country. From the gas fields, high-pressure pumps force the gas through large diameter pipelines to distant cities. There the pressure is reduced and the gas is distributed throughout the city in pipes under the streets, similar to water mains. To serve our building, the gas company "taps" the main and lays an underground line about 2" in diameter. As the gas line enters the building, the pressure is again reduced, and a meter is installed in the line. Through pipes installed by a subcontractor's men, the gas is piped to the gas burning appliances. **Heating and Air Conditioning** The furnace and the air conditioner may be separate units. Usually they are parts of the same unit. The burning of gas supplies heat, and compressors operated by electricity supply the cooled or "chilled" air. Both the furnace and the compressors may be controlled by setting a thermostat. The thermostat is a control device by which the temperature in the building may be kept constant. The heated or chilled air is carried about the building in sheet metal ducts. These ducts are rectangular or square and may vary in size from 4" x 10" to much larger. The air, at low pressure, moves slowly through these ducts from the furnace or air conditioner to the various rooms. The air enters through a grill device called a register. There are also other registers, either in room or in the halls, through which the air returns to the furnaces and the air conditioning unit. There is filtered (to remove dirt and dust) and again heated or cooled and circulated throughout the building. These ducts are called *return air ducts*. **Communications** From each telephone in our building, wires lead to one central point where they enter an equipment cabinet. The wires are connected to relays (used for switching) in the cabinet. The wires from the cabinet leave the building bound into a cable containing many individual wires. Central telephone offices may communicate with each other either through cables or by means of special radio broadcasting and receiving equipment. *Relay stations receive* and retransmit radio messages. **Other Utilities** A building may include many other utility systems such as: 1. Steam 2. Chilled water 3. Compressed air 4. Oxygen 5. Teletype and telegraph communications 6. Built-in television and radio cables. **Networks of Utilities** It should be easy to see why the utility lines within a building are a large part of the cost of the structure, sometimes the largest part. Utility lines must: 1. Operate satisfactorily and safely 2. Not interfere with each other 3. Generally, be hidden or blended into the floors, walls and ceiling. **INSTALLING PLUMBING SYSTEMS** Plumbing systems carry gases and liquids which move rapidly at pressures varying from the weight of the gas or liquid (gravity) to extremely high pressures. Sometimes the pressure is 5, 000 pounds upon each square inch of pipe. All plumbing and piping systems must be tight enough to prevent any leakage. **Major Kinds of Plumbing Systems** Plumbing systems are used to move the following: 1\. Fresh water, 2\. Hot water or steam, 3\. Water for fire protection, 4\. Gases 5\. Other fluids, and 6\. Sewage The piping material used depends upon (1) the type of plumbing system, (2) the designer system, and (3) local building codes and standard practices. **Who Does the Plumbing** The number, type, and location of plumbing fixtures, appliances, and equipment are determined by the architect. The piping needed to serve them is designed by an engineer who makes sure that building codes and good practice are followed. The general contractor usually subcontracts the plumbing to a plumbing subcontractor or a mechanical subcontractor, who also may do the sheet metal work. The subcontractors prepare detailed shop drawings of the plumbing. After the engineer approves his drawings, the plumbing subcontractor begins the installation. **Piping** Piping is used to make a plumbing system. Piping consists of (1) rigid straight lengths, (2) curved lengths of flexible tubing, and (3) fittings such as couplings, tees, ells (elbows) at various angles, Y's, crosses, reducers, and unions. A ***union*** is placed into a system of piping so that it can be taken apart, at that point, for repairs. Where a piping system is under pressure, ***valves*** are placed in the lines to shut off or turn on a part of the system. Pipe size is specified by a number which is called the ***nominal size***. It is related to the pipe diameter, but for many kinds of pipe and tubing, it is neither the inside nor the outside diameter. Installing Piping At the building site, copper tubing is cut to the lengths needed. Lengths of copper tubing are joined with couplings, tees, or cells at bends in the lines. All these fittings are made to slide over the end of the piping very tightly. Then they are sealed by a thin film of solder. This is called a ***sweated join***t. The soldering metal is called ***lead solder***, but it is actually an alloy of lead and tin. All pipe fittings are threaded by the manufacturer. A compound, often *called pipe dope*, is smeared on the pipe thread before the fitting is screwed onto it. When this pipe dope hardens, it seals the threads and prevents leaks. As the piping must be adjusted or tailored to each particular building, most pipe of less than 4'' diameter is cut, fitted, and threaded at the site. Pipe systems using pipe larger than 4'' diameter can be assembled by welding two lengths together at their ends or by welding flanges to the ends of two pieces of pipes. The flanged pieces of pipe are bolted together and can be taken apart. Cast-iron soil pipe systems are assembled using lead joints. Each length of cast iron soil pipe has a flared end called the *bell end*. The other end of the pipe is called the *spigot end.* The spigot end of one pipe or fitting is placed in the bell of the adjoining pipe or fitting. The space around the spigot end is packed with *oakum* (a greasy packing) for an inch or so. The rest of the bell is poured full of hot led. Clay pipe used for storm drainage is also of the bell and spigot type, but the joints are filled with a cement grout (a mixture of cement, sand, and water). Plastic pipe is now used in many applications. It has the advantages of flexibility and of not being affected by corrosive liquids or gases. Special techniques are required to assemble and install plastic pipe. Mastics or cements often are used to join plastic pipe. Also the pieces may be clamped together. If a structure is to built on a slab, some piping is installed before the concrete for the slab is placed. The parts of the piping which extend above the slab are called risers. The horizontal part of piping system is hung from the underside of floor slabs or from ceilings, using a pipe hanger. Where pipe runs vertically up a building, special hangers are used to fasten it to the wall. Piping systems must be fastened to the structures to prevent strains in the piping which can cause it to leak. All plumbing must be carefully installed. People and property maybe harmed by plumbing failures. **INSTALLING PIPING SYSTEMS** ***Trenching*** Two types of construction equipment are used to dig trenches for pipeline: The ***backhoe*** and the ***trencher**.* The backhoe has a long, jointed arm with a bucket on the end. The edge of the bucket is lined with teeth. In digging, the arm of the backhoe is first stretched out, and the bucket is dropped into the ground to rest on its teeth. The arm then is pulled in toward the machine to dig the trench. The trencher has a large wheel to which small buckets are attached. As the wheel revolves, the buckets dig into the ground and pick up earth which is then thrown into piles along the sides of the trench. As the trench is dug, bracing sometimes has to be placed between the sides of the trench to keep them from caving in. ***Laying Pipe*** Pipe usually is laid with a crane. It must be placed in the trench at exactly the correct height and slope. This is most important, particularly in sewer lines. Sewer pipes are laid at a slight slope so that the waste water will flow down toward the sewage treatment plant. Sometimes sewage has to be pumped, but this is avoided whenever possible. **Who Installs Pipelines** Pipelines are carefully designed by civil engineers. When designing piping systems, civil engineers will: 1\. Lay out the route, 2\. Specify pipe sizes, 3\. Choose locations for pumping, processing, or treatment plants, 4\. Select equipment for these plants. Pipelines are usually installed by mechanical contractors, some of whom specialize in pipeline construction. The craftsmen involved are the operating engineers who operate the construction machinery and the pipe layers, who may also be plumbers, pipe fitters, steam fitters, or boilermakers. Water systems usually use cast iron or concrete pipe, although steel, asbestos, cement, copper, or plastic pipe is sometimes used. Joints in cast iron pipe may be of three types: lead, mechanical, and compression. Lead joints are similar to those on cast iron soil pipe inside a building. Lead is poured into a space between pipes to seal them together. On mechanical joint pipe, bolts hold the two pieces of pipe together. A gasket, or piece of pliable material, seals the joint against leakage. A compression joint (connection) is made by forcing the plain end of one pipe into the bell of the adjoining pipe in which a rubber gasket has been placed. The gasket clamps tightly around the plain end and fits tightly into the bell to seal the joint. ***Sewerage*** A piping system which collects sanitary sewage or storm drainage is called a sewerage. The piping material is usually *vitrified clay*. The clay, which must be of a certain type, is mixed with salt. After shaping, it is fired (heated in a kiln to a high temperature). This process gives the pipe a hard, vitreous (glass-like) surface which cannot be corroded by most waste materials. Usually sewers are laid in a straight line from manhole. Manhole are placed at street corners and intermediate points, usually between 200' and 300' apart. They are made of brick, vitrified clay, or concrete pipe and are about 4' in diameter. Each manhole has a channel in the middle through which the sewage flows. Standing on the bottom of the manholes, men can push rods through the sewer to clear out any obstruction. A flexible steel wire (called a snake) , turned by a slow speed electric motor, also can be used to clear a clogged line. **Steam Lines** Steam lines must be insulated to prevent the heat in the water from being lost, or to prevent the steam from cooling and turning to water. The pipe may be wrapped with insulation which is then covered to protect it underground. Or the pipe may be set in various insulating materials which look like concrete and are made of lightweight aggregates. **Petroleum and Natural Gas** Pipelines many hundreds of miles long are built to transport petroleum from its place of origin to a refinery. Similar pipelines carries natural gas to cities where it will be used. These pipelines are made of black steel pipe in 30' lengths that are welded together. The same pipeline often carries several kinds of oil. When the pipeline operators have finished one kind of oil through the lines, a go-devil (like bottle brush) is forced through the pipeline with a volume of water behind it. **Records** A great many pipelines (as well as electrical and telephone cables) lie underneath the ground in cities and in some rural areas. Accurate records must be kept showing not only the pipelines themselves, but all valves, manholes, pumping stations, and other features. These records are usually in the form of drawings kept at one of the company's offices. Often the locations of pipelines are *monumented*. Monumented means that permanent marks are placed on the ground itself. **INSTALLING ELECTRICAL POWER SYSTEMS** ***Who Designed Electric Power Systems*** Everyone concerned with the design and installation of electric power must be fully qualified by both education and experience. Usually they must have a license which is granted only after passing a test. Electrical work is designed by an electrical engineer. The electrical engineer works with mechanical engineers in designing steam-generating plants and with nuclear engineers in designing atomic power plants. **Ownership** Usually an electric utility company owns the power plant and all the outdoor distribution system, up to the place where the electricity enters a structure. The electric utility company usually owns the meter which shows how much electricity each customer uses. The owner of a building owns the electrical system within the structure, except for the meter. **Construction Personnel** The electric utility company usually hires a general contractor to build a power plant. This general contractor usually subcontracts the electrical construction inside the power plant to an electrical subcontractor. The craftsmen who do electrical work are called electricians. There are two groups of electricians. *Linemen* do outside construction, and *wiremen* work inside. **Outside Construction** Electric current, measured in amperes, flows great distances to reach its consumers. Voltage is a measure of the force which causes the current to flow. Electricity is usually generated at moderate voltages. But the cheapest way to send electric power is at high voltage. Thus, beside a generating plant, there is usually a switchyard equipped with transformer to increase or decrease voltage. Power lines, called transmission lines, run from the switchyard transformer to cities or industrial areas where the power will be used. This lines are built across great distances, sometimes across several states. Transmission lines are built by teams of skilled workers according to plans and specifications set up by engineers. First the *right-of-way* is purchased from the various landowners. Electricity at very high volta