Azhar Shahzad

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About Azhar Shahzad

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  • Birthday 01/30/1989

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    Civil Engineer

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  1. Definition of BIM: Building information modelling (BIM) is a digital representation of physical and functional characteristics of a facility. A BIM is a shared knowledge resource for information about a facility forming a reliable basis for decisions during its life-cycle; defined as existing from earliest conception to demolition. BIM benefits: Faster drafting without loss of cost and quality High level of customization and flexibility Optimization of schedule and cost Seamless coordination and collaboration Conflict detection and risk mitigation Easy maintenance of building life cycle Here is the nice info-graphic which compares BIM based process to the 2D drawings based process: Learn more about BIM solutions for structural engineers
  2. It is already described under the heading of Traverse including figures.
  3. 1. BIM will be the backbone of future Construction Building Information Modeling is taking over the industry globally at the speed of light. In the UK, for example, the industry adoption rate has boomed from 13% in 2010 to 39% in only two years and many countries are introducing initiatives such as national BIM recommendations to push the adoption forward. It is reasonable to expect this trend to continue as the construction industry recovers from recession and as BIM continues its path towards becoming an industry requirement. Whether you are studying structural engineering, construction engineering or architecture, expect BIM to be a major factor and competitive advantage upon graduation. 2. The "I" in the BIM will become even more Significant While impressive illustrations and 3D models are a highly visible part of BIM, robust opportunities for collaboration, coordination, fabrication, as well as, integration to production automation systems and machinery is what really puts the “I” in BIM. Information management and Integration between models allows each professional to focus on what they do best while simultaneously improving clash checking and accuracy. BIM makes relevant information available to everyone when they need it. Models become more than a sum of their parts, making BIM a highly attractive tool for both companies and professionals in related industries. 3. The Industry will look for BIM experts instead of CAD Assistants With the industry changing at a rapid pace, companies start looking for skilful BIM users to keep up with this speed of change. To mention a few sought-after skills, employers start looking for experts who can create and develop different models and perform analyses and simulations based on these models. Companies who are at early adoption stages of BIM are looking for BIM specialists who are capable of implementing BIM, managing and modeling all project information and also educating others within the organization. Academia and schools need to meet this demand by delivering a new generation of professionals who are fluent in BIM. 4. With BIM You will... Practically everyone involved in the design and construction process will gain benefits from BIM. Engineers, architects and contractors can virtually walk through construction models, explore structural components and details, and identify any potential design, construction or operational issues. BIM allows builders to bring even to the most complicated structures into reality by enabling the high detail modeling of multiple materials while simultaneously saving time, resources and space. Users will be able to focus on the essential instead of the menial. Learn more about BIM solutions for structural engineers
  4. Study some basic mathematical topics like Geometry, Vectors, and Matrices etc. It will greatly increase your understanding towards engineering mechanics. Must read relevant theory first before attempting problems. Start from easy problems then go on as your concepts developed.
  5. Rock support for tunnels and underground cavern design is a demanding and very complex task. In principle, the problem can be approached from two directions: The first way is to define the relationship between geo-mechanical properties of the rock mass and the support methods used. This is mostly based on the utilization of statistical and empirical data gathered in similar conditions. The second way is to estimate the deformation characteristics of the rock structure, and then the related effect on supporting structures. This method typically requires very good rock property and rock mass property data. The most important factors affecting rock reinforcement method and design are: Geological factors, such as rock mass structure. Dimensions and geometry of excavated space. Location and direction of caverns in the rock mass. Excavation method. Use and expected lifetime of space. Common support methods in underground construction work are: Bolting. Sprayed Concrete. Steel Arches. Concrete Lining. Grouting. 1. BOLTING Rock bolting is one of the most common methods of rock reinforcement. The main principle of bolting is to reinforce loose rock or fractured in-situ rock to precent caving or spalling, and to assist the rock mass to form its own self-supporting structure. Bolts can be divided into three categories according to the way they behave in the rock, for example, grouted bolts, mechanically anchored bolts and friction bolts. 1.1 Cement-Grouted Bolts Cement-grouted rebar is still the most inexpensive and widely used rock bolt, because it is simple and quick to install and can be used with or without mechanized equipment. Correctly installed, a cement-grouted bolt gives rock support for years. The grout cement provides protection from corrosion. Special galvanized and/or epoxy coated bolts can be used in extremely severe conditions. The major disadvantages of the cement-grouted bolt is its relatively long hardening period. The grout takes between 15-25 hours to harden, therefore it does not provide immediate support. When immediate support and/or pre-tensioning is needed, a grouted wedge-type or expansion-shell bolt can be used. Mixing additives in the grout can reduce the hardening time, but it also increases bolting cost. The water/cement ratio considerably affects the quality of installed bolts. The best water/cement ratio is 0.3 (w/c). This grout density can be easily used and maintained when using mechanized bolting equipment. 1.2. Resin-Grouted Bolts Resin-grouted bolts give the required support relatively quick due to a short hardening time. When correctly installed with full-length grouting, the resin-grouted bolt is considered to give permanent support with a life span of 20 to 30 years. By using resins with two different hardening times, with faster one at the bottom of the hole and another that is slower at the stem, the bolts can be pre-tensioned. The same can be done for short-time support by only bottom-grouting the bolt. 1.3. Cable Bolts Cable or steel strained bolts are used to bind and secure large volumes of rock around large caverns. Cable bolts can be used both before and after excavation, and also used for preventing rock slides in mountain slopes and quarries. The anchor itself is a steel strand, typically two strands of 15.2 mm in diameter, with typical bolt length being between 10-25 meters. Today, with mechanizes equipment, the installation and grouting of cable bolts of any length is fast and efficient, and the cable bolt's bearing capacity clearly exceeds capacity of rebar steel bolts. Its lack of efficient protection against corrosion limits its extensive use in permanent rock support. 1.4. Mechanically-Anchored Bolts Mechanically anchored bolts are usually wedge or expansion-shell bolts that are point-anchored at the bottom of the hole. The bolt has an expanding anchor at its end. After insertion, the bolt is either rotated or pressed/hammered against the bottom of the hole. This expands the wedged end and anchors the bolt firmly to the end sides of the hole. To install anchored bolts successfully, the hole size must be accurate and the rock must be relatively solid. Wedge or expansion-shell bolts are typically meant for temporary rock support. Together with cement grouting, it provides both immediate and long-term support. 1.5. Friction-Type Bolts Typical examples of friction-type bolts are the split-set and Swellex bolts. Both are quick and easy to install and give instantaneous support. They can not, however, be used for long-term reinforcement. The split-set bolts is hammered into the hole, which has a slightly smaller diameter than bolt. Using the correct hole size for a specific bolt diameter is essential for successful installation. Split set bolts are very suitable for layered formations. The Split-set bolts provide immediate support but only for fairly short period of time. A disadvantage is that the split-set cannot be effectively protected against corrosion. The life span can somewhat be extended by using cement grouting. The Swellex bolt has a longer life span than the Split-set. It is installed by applying high-pressure water to bolt after inserting it to the hole. The high pressure expands the bolt to its final dimensions in the hole, therefore enabling it to utilize the roughness and fractures in the bolt hole surface. As with the Split-set bolt, poor corrosion protection limits this bolt. 1.6. Equipment for Bolt Installation Development of mechanized equipment began as early as the 1970s. Today there is a wide selection of fully mechanized equipment, and a wide variety of different methods for bolt installation. The main factors affecting the choice of method are usually tunnel size, amount of bolts to be installed and work cycle arrangement at this site. Manual operation, the hand-held drilling and installation of bolts, is typically used in small drifts and tunnels where drilling is also performed by hand-held equipment, and there is a limited amount of bolting work. Semi-mechanized installation is still typical at tunneling work sites. The drilling jumbo is used for drilling bolt holes, and bolt installation is performed from the jumbo's basket boom or from a separate utility carrier or truck. With today's full mechanized equipment, one operator can handle the entire bolting process from drilling to grouting and bolt installation. The operator is positioned away from the unbolted area under a safety canopy that protects him from failing rock. Although safety is a major reason for the development of mechanized bolting equipment, the superior installation technique of mechanized bolting rigs also produces consistently higher bolting quality. Thanks to powerful cement mixers, pumps and effective grouting methods, the bolts are securely fixed and grouted to their full length, providing a sound reinforcement structure, even with long bolts. 2. SCREENING Screening, which is the installation of wire mesh, is most typically used in underground mining, but also construction sites together with bolting and/or sprayed concrete. Screening is primarily performed manually by applying the wire mesh together with bolting of the tunnel. It can also be done by mechanized equipment, such as by having a screen manipulator on the bolting or shotcreting unit, or on a dedicated screening machine. 3. SPRAYED CONCRETE Sprayed concrete, otherwise called shotcreting, is widely used support method in construction. It is used for temporary or long-term support, lining and backfilling. Usually shotcrete is used together with bolting to obtain the best support or reinforcement. Shotcrete can be reinforced by adding steel fiber to the concrete. The most common forms of shotcreting are dry-mix and wet-mix methods. In the dry-mix method the aggregate, cement and accelerators are mixed together and propelled by compressed air. Water is added last through a control valve on spray nozzle. The dry method is suitable for manual shotcreting because the required equipment is usually inexpensive and small. On the other hand, dry method can pose a health hazards as it creates considerably more dust and rebound than the wet method. The quality also depends heavily on the shotcreting crew, and may vary widely. In the wet mix method, aggregate, cement, additives and water are measured and mixed before transport. Today, wet mix is more widely used because it is easy to mechanize and the capacity can easily out-do the dry method. Rebound rate is low and the quality procedure is even. Critical factors in shotcreting are: Water/cement ratio. Grain size distribution of aggregate. Rebound ratio. Grain size distribution. Mix design. Nozzle design. Nozzle distance and angle. Layer thickness. Manual shotcreting has been largely replaced by mechanized shotcreting machines. With mechanized equipment, multiple capacities per hour can be reached, together with consistent and even quality of the concrete layer. Safety, ergonomic and environmental conditions are other important aspects of shotcreting. These factor are efficiently improved with mechanized shotcreting units. 4. STEEL ARCHES Steel arches are common permanent support method for weak rock formations. These are usually installed in the tunnel immediately after each round, at the same time as rock bolting. Steel arches are also commonly installed during shotcreting to give temporary support before final concrete lining of e.g. traffic tunnels. 5. GROUTING Grouting is the method in which a solidifying liquid is pressure-injected into the rock mass. The main purpose of grouting is to prevent ground water leakage into the tunnel, and to increase overall rock mass strength. In grouting, a chemical agent or cement mass is pressure-pumped into the drill-hole to penetrate fractured and fill cavities. In drill and blast tunneling, grouting is typically performed before (pre-grouting) or after (post-grouting) excavation. 5.1 Pre-Grouting Pre-grouting means that rock mass is grouted before excavation begins. Usually, pre-grouting is done from the tunnel, but in situations with low overburden it is also possible to do it from the surface. Probe holes are drilled to map possible fractures and register water flow. This helps to analyze the need for grouting. Later, grout holes are drilled in conical-fan shape in front of the tunnel face. Typical grouting fan length is 15-25 meters. After drilling, the grouting agent is pumped into the hole until leakage has reached an acceptable level. Tunnel excavation can begin once the grouting mass has settled. Grouting fans overlap each other so that in 15-meter long grout holes, grouting is performed every second or every third round depending on the round length. 5.2 Grouting after Excavation (Post-Grouting) When grouting is done after excavation, grouting holes are drilled from the tunnel in a radial form. In good rock conditions with small water leakage, post-grouting is often adequate. Post-grouting enables better rock mass structure evaluation. On the other hand, water leakage blockage is more difficult because the water flow tends to flush away the grouting agent before it hardens. 5.3. Grouting Agents The grouting agents can be divided into two categories: Suspension and Chemical. Cement water or bentonite water suspension is the most typical in rock grouting because both are cost-effective and environmentally safe. The drawback is, however, a relatively large maximum grain size, which leads to poor penetration in small cracks. Penetration characteristics can, however, be improved by adding additives. Silicate-based chemicals are also used to speed up the hardening time. Chemical agents are silicate-based, resin polymers, polyurethane-based or lignin-based chemicals that typically penetrate very s cracks and have adjustable hardening times.
  6. By building up environment Civil Engineers play with nature... Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings. Why Become a Civil Engineer? 1. Civil engineers create the world around us Civil engineers are the unsung heroes of the engineering world. Yet this jack-of-all-trades discipline is an incremental part of creating everything from tall skyscrapers and complex stadiums to bridges, railways and tunnels. As a civil engineer, your work influences where people work, relax, learn and live. You will be a part of helping society to become more advanced by adapting the infrastructure to meet challenges brought on by new technologies, population growth and climate change. Civil engineers know that even the simplest structure can include hundreds of “unknowns” which they have to be able to identify and solve in order to ensure the structure is operational, stays safe and stands the trial of use, environment and age. In addition to all this, civil engineers also play a key role during emergencies like droughts or natural disasters by helping those affected to recreate their living environment and the infrastructure that provides for their basic needs. 2. Civil engineers never have a dull moment Civil engineers can work in a versatile range of positions and projects. Civil engineering specializations such as structural, environmental, geo-technical and transportation engineering all entitle challenging, constantly changing work environments and require creativity, adaptability, good problem-solving skills and ability to think on one’s feet. As a civil engineer, despite your area of specialization, you need to be sensitive to local and environmental challenges as well as to the requirements of different construction project participants. You need to have attention to detail while simultaneously understanding “the bigger picture”. In addition to the wide spectrum of challenges, the versatility of projects civil engineers can participate in ensures that you are unlikely to have a dull moment at work. You can work below the surface delivering tunnels, underground railways and energy and water supplies as well as above the surface creating roads, bridges, stadiums, hospitals, skyscrapers and many more. As a civil engineer, you are likely to be constantly on the move, sharing your time between the site, the office and perhaps even different geographical locations. 3. Civil engineers have a monument to show that they were there While civil engineering can be somewhat stressful, the profession includes a huge sense of accomplishment to make it all worthwhile. Throughout history, civil engineers have participated in some of the most ambitious and incremental projects known to mankind. World-known ventures such as the Hoover Dam, the Great Wall of China and the Hardanger Bridge are tokens of the hard work and expertise of civil engineers. While you might have to start your civil engineering career with slightly smaller projects, the fact remains that by the end of the day you will have a monument to prove that "you've been there". You know all the challenges and effort that went into transforming the blueprints into a fully functional structure. What do you think about Civil Engineering?
  7. Tunnel Sections Tunnels range in dimensions of cross-sections from those of small galleries driven by miners working with hand tools, to tunnels large enough to accommodate rail road trains, double lane of highway traffic, or to transport very large volume of water as in diversion structures in dams. A minimum size of tunnel is 9 ft high and 4 ft wide at the working face. Designed shapes or sizes of tunnels in x-section conform to a planned uses to tunnel and the some extent to the nature of the material that is anticipated will be encountered during excavation, x-sectional shapes vary from square or rectangular as for example in mining operations in strongly bedded sediment rocks, to circular. A common type of x-section is horse shoe shaped to provide maximum stability in the roof portion of the tunnel. Geological Exploration The geological conditions that are likely to met in any given work of construction must be predicted. The line of the tunnel and the neighboring ground is geologically surveyed and sub-surface data obtained by exploratory boring. Careful control of such trial boring operations is necessary in order to extract the maximum amount of information from the ground. The cost of tunneling in general is least where construction is carried out in sound rock, and in one kind of rock throughout. Straight forward geological conditions such as simply dipping strata allow cost to be estimate easily; more uncertainties arise in connection with folded and faulted beds. Geological structures such as faults and joints should be mapped along the line of a tunnel. Strongly developed joints systems are potential channels for underground circulation and should be recorded. Badly fractured ground is to be avoided if possible. If unavoidable it may require special timbering or other treatment, and a prediction of where faults are likely to met underground is therefore of greater importance. Hard rocks where excavated may stand with little support (some tunnels are unlined throughout) because they are strong enough to withstand the lateral pressure exerted by surrounding rocks but if soft bands are present there may be a tendency to slipping on these weaker layers and suitable support for the walls of the excavation will be necessary. Inter- bedded hard and soft rocks, such as sand-stones and shales may give rise to many difficulties. Ground-water percolating through the sand-stones soaks into the shales and softens them and hence the slipping is promoted.
  8. A tunnel is an elongated, narrow essentially linear underground opening with a length greatly exceeding its width or height. Most tunnels are nearly or exactly horizontal but for special purposes, tunnels may be driven at angles up to 30 degree from the earth's surface. The one which is greater than 30 degree from horizontal are designed as shafts. When rocks in tunnels are highly in-competent, especially when underground water is present, tunneling becomes a very costly and hazardous operation, and excavation and containment of such rocks present a challenge that requires maximum use of highly technical skills and ingenuity. History of Tunneling There is abundant archaeological evidence that in Europe stone age man sank shafts and drove tunnels to recover flint for the fabrication of sharp-edged implements such as knives, axes etc. later as an elementary knowledge of metallurgy was acquired by premature people, possibly for the first time central Asia, underground excavation became necessary to supply the increasing demands for metals and alloys. Very early underground excavations for metal-bearing have been identified in Caucasia, between the Black and Caspian Sea, and date back to approximately 3500 BC. Many tunnels were built in ancient times by the Babylonians, Indians, Persia and Egypt in search for precious metals. Stone-age man used very primitive tools in underground excavation. Particularly useful to him were picks made of deer antlers, flint axes and hammers and wedges made of bone and wood. The production of metals and alloys provided materials for increasingly efficient rock excavation. Later on explosives were used in the seventeenth century. For hundreds and perhaps thousands of years underground working in hard rocks, especially those containing few fractures and fissures, were advanced by building fires against rock faces to cause expansion and spalling. In some operations spalling of the heated rock was accelerated by dowsing it with water. The fractured rock was than separated from the working face with picks, gads and wedges. With the increasing use of explosives first the black powder later nitroglycerin, steel temping techniques were perfected and permitted efficient and economical hand drilling of holes for explosives. Tunneling machines have been used to excavated tunneling with diameters of about 6 ft to more than 36 ft. Rate of excavation of over 400 ft per day have been recorded in soft ground. In hard rocks it can be less as 100 ft per day. It includes a rotating cutter head and provision for controlling forward thrust and alignment. In the hardest of rocks, near the middle of the nineteenth century steam powered piston drills and later percussion drills, powered by compressed air, made their appearance and at the same time several tunneling machines such as moles were invented. Tunnels have been driven in a variety of natural materials ranging from unconsolidated water-soaked clay, sand and gravel to dry very hard un-fractured rocks. It is one of the most costly and at the same time one of the most hazardous of all engineering under-takings. In case of long tunnels in area of geological complexity, all types of uncertainties arise, including design and construction techniques and including estimate of cost. The location of a tunnel like the site of bridge often does not allow much freedom of choice. It becomes necessary at given place to maintain an alignment. Before designing and planning a tunnel the undesirable underground conditions must be anticipated. Tunnels through massive un-fractured granite or through horizontally layered sandstones that are well cemented and un-joint present no special problems in design and preparation of cost estimation; whereas in geological complex areas it is an art and intelligent guess work. Purpose of Tunneling Tunnels have been constructed for great variety of purpose, and they are classified as follows: Tunnels driven to gain access to economic mineral deposits and to provide haul-ways for extracted minerals. In some mining operations tunnels are driven to provide adequate circulation of air in underground workings. Transportation Tunnels, including pedestrian highness navigational and rail road tunnels. These are among the largest and at time the most difficult of all tunnels to excavate. Water or Sewage Tunnels: These tunnels may or may not be constructed so as to transport liquid under pressure, and a distinction is made between gravity flow tunnels and pressure tunnels. The latter are designed to contain without leakage water under hydrostatic pressure or force-pressure head. Military Tunnels: These tunnels are driven in connection with underground military operations. Tunnels to provide protection from atomic explosion. Utility Tunnels. Built to contain power and communication transmission line, gas line, etc.
  9. This file is in PowerPoint format, contains topics relating Flexural Behavior of Reinforced Concrete Beams and Transformed Section. Contents: Modulus of Elasticity. Flexural Behavior of Beams Under Service Load. Assumption for the Study of Flexural Behavior. General Procedure for the Derivation of Formula > When Both Steel and Concrete are in Elastic Range, When Cracks are Appeared on tension Side, When Compression Stresses Cross Elastic Range, Equation for Calculating Moment Capacity, Flexural/Bending Stress Formula, Shear Stress Formula. Different Types of Cracks > Pure Flexural Cracks, Pure Shear/Web Shear Cracks, Flexural Shear Cracks. Tensile Strength of Concrete > Split cylinder Test, Double Punch Test, Modulus of Rupture Test. Transformed Section > Modular Ratio, Un-cracked Transformed Section, Un-cracked Transformed Section, Cracked Transformed Section, Resisting Moment Capacity, Minimum Reinforcement of Flexural Members, Minimum Depth of Section, Determination of “k” value. Reduced Moment of Inertia Due to Cracking. Long Term Deflection. Download:
  10. Latitude and Departure In order to do start with Theodolite Traversing you should familiar with the Latitude and Departure which are discussed briefly below, OA is the line with whole circle bearing equal to θ. OC = Latitude = lCosθ OB = Departure = lSinθ By using the above formulae for Latitude and Departure with whole circle bearing, calculator will be giving aljebraic sign automatically for Latitude and Departure. For a closed Traverse ∑ of all Latitude is equal to zero and ∑ of Departure is also equal to zero. Consecutive co-ordinates When the Latitude and Departure are calculated at second point of a given line taking first point as a origin then it is called consecutive co-ordinates. Independent co-ordinates Independent co-ordinates are the Latitude and Departure of points of a traverse with respect to a common origin, so that all the values are +ve. These are used for plotting purposes. Bowdich Rule This rule is used to apply the correction in Latitude and Departure which states that correction in Latitude/Departure is equal to Length of Line multiply by Total correction in Latitude/Departure and then dividing by the perimeter. Traverse Table For the following traverse ABCD, I have applied the correction in Latitude and Departure using Bowdich rule. Line L(m) Beari.(° ′ ″) Latd. Depr. Corrections applied Consecutive co-ord. Independent co-ord. Latd. Depr. Latd. Depr. Latd. Depd. AB 148 115 30 -63.27 133.58 -0.26 - -63.98 133.58 500 500 BC 172 42 25 126.98 116.02 -0.30 - 126.68 116.02 628.68 616.02 CD 201 205 30 -181.42 -86.53 -0.36 - -181.7 -86.53 444.90 529.49 DA 202 306 15 119.44 -162.9 -0.36 - 119.08 -162.9 563.98 366.59 ∑ 723 +1.28 +0.17 -1.28 0 +0.17 As you can see, correction was not applied in Departure as the error was too small to be neglected. Using Bowdich rule we can apply correction in Latitude and Departure for respective line
  11. Traversing It is the method of establishing horizontal controls. Traverse Traverse is a series of connected lines forming or not forming a loop. In the first case it is called closed traverse (when the loop is formed) and in the second case it called open traverse (when loop is not formed). Vertical Control That is the reference point in vertical plane, it includes series of bench marks and points of known elevations. Horizontal Control It is the series of points in the horizontal plane of known co-ordinates. Types of Traversing Traversing can be further divided into two categories depending upon the type of instrument used, Compass Traversing Theodolite Traversing 1) Compass Traversing When prismatic compass is used for determining the direction of line, the method is called compass compass Traversing. 2) Theodolite Traversing When theodolite is used for measurement of angles or directions, the method is called theodolite traversing. By direction of line we mean the bearing of that line.
  12. Fore Bearing It is the bearing of line when the first letter of line say AB is taken as origin. This is to be written as Fore Bearing (F.B). Back Bearing It is the bearing of line when second letter of line say AB is taken as origin and this is to be written as Back Bearing (B.B). Theoretical difference between Fore Bearing (F.B) and Back Bearing (B.B) should be 180°. Local Attraction If the difference between magnetic Fore Bearing and Back Bearing of a line is not exactly 180°, it may be due to presence of local attraction at one of the both stations. If this difference is exactly 180° then both stations are free from local attraction. Local attraction may be due to following reasons. Overhead electrical wires Magnetic materials in the vicinity Practice Problem In the following table observed Bearings are given, we will compute the corrected bearings and Internal Angles. Line Observed Correction Corrected F.B B.B F.B B.B AB 70° 00′ 251° 00′ A= +30′ , B= -30′ 70° 30′ 250° 30′ BC 328° 00′ 145° 00′ - 327° 30′ 147° 00′ CD 225° 00′ 71° 00′ - 257° 30′ 77° 30′ DA 139° 00′ 316° 00′ - 136° 30′ 316° 30′ By observing the table, it may be noted that no line has a difference of exactly 180° between Fore Bearing and Back Bearing. In such a case, a line where the difference is closest to 180° is selected. Such a line is called line of least disagreement, for this line correction is assign to each of the two stations of that line with opposite sign. In the above table line AB is selected for error distribution. Now, we will compute internal angles from these corrected Bearings. A = (360° - 316° 30′) + 70° 30′ = 114° 00′ B = 327° 30′ - 250° 30′ = 77° 00′ C = 257° 30′ - 147° 30′ = 110° 00′ D = 136° 30′ - 77° 30′ = 59° 00′ Before computation of internal angles you need to draw a rough sketch of scheme based on corrected bearings so that you can judge which angle is lying in which quadrant.
  13. 1 - Tripod It should be of a rigid type capable of fixing the position of the instrument with a small lateral movement on its top when required. 2 - Foot screws These are provided for leveling the instruments. 3 - Plate level Provided for checking the level of the instrument. 4 - Horizontal clamp Provided to clamp the movement in horizontal plane. 5 - Vertical clamp For clamping movement in vertical plane. 6 - Slow motion screws These screws are used to move Theodolite either vertically or horizontally in small fractions. 7 - Telescope In a telescope vertical hair is used for horizontal angle measurement while horizontal hair is used for vertical angle measurement. Focusing arrangement for the object glass is usually provided in the body of the telescope. Collimeter is provided to bring the object in the field of view. 8 - Vertical axis It is the axis around which the telescope rotates in horizontal plane. 9 - Horizontal axis It is the axis around which telescope rotates in vertical plane. 10 - Optical plummet It is provided for centering the instrument over a ground station. 11 - Angle reading arrangement In screen display you can note angle measurements taken with Theodolite.
  14. Leveling It is the branch of Surveying in which relative elevations of points are determined. There are following Types of Leveling 1 - Ordinary Leveling It is general purpose Leveling and unless otherwise stated all types of Leveling will come into this category. 2 - Reciprocal Leveling This is done when a site is unusually long, i.e crossing the river. Sights are taken from the two banks by placing the staff on the opposite bank almost simultaneously and finding the average of appearant difference of level. This method eliminates the error due to curvature and refraction. 3 - Precise Leveling This is a special type of Leveling using very precise level fitted with parallel plate micrometer and using precise staff with invar strip This is used for establishing new bench marks and therefore is undertaken by state agencies. 4 - Barometric Leveling This type of leveling is used in higher surfaces of earth like mountains. Application of Leveling Longitudinal Sections (L-Sections) : It is done to determine the levels at given intervals along the center of level road. Cross Sections (X-Sections): These are the levels at a given cross section of a road or any engineering work Contouring Invert levels for sewers Head rooms from bridges: Staff is used in inverted position from the zero end touching the ceiling of the bridge, the reading is entered as -ve and R.L of that position is calculated in usual manner.
  15. 1 - Pacing Permissible error ≤ 1 feet in 20 feet. 2 - Chain Permissible error ≤ 1 in 1000. 3 - Metallic Tape Permissible error ≤ 1 in 1000. 4 - Steel Tape This tape is made of steel alloy of very small co-efficient of thermal expansion. Permissible error ≤ 1 in 1000. 5 - Invar Tape This tape is made of very expensive steel alloy of almost negligible co-efficient of thermal expansion and is used for very precise linear measurements. Permissible error ≤ 1 in 50,000. 6 - Techometry Permissible error ≤ 1 in 50,000. 7 - Electronic Distance Meter Permissible error ≤ 1 in 100,000.