Construction Technology: Building Process, Loads and Forces in Buildings, and Failure Modes - Assignment Example

CONSTRUCTION TECHNOLOGY Name Instructor Course Date i. Portfolio Checklist Item Comment Part 1: Questions Part 2: Building Process Part 3: Loads and Forces in Buildings Part 4: Failure Modes Part 5: Legislation Part 6: Terminology ii. Commentary Part 1: Questions This section answers questions on various calculation and theory problems related to construction Part 2: Building Process This part outlines the chronological process of coming up with the design of a building. Part 3: Loads and Forces in Buildings In this section, various forces and loads acting on a building are highlighted. Part 4: Failure Modes This part provides all the possible means through which failure may occur in a building. Part 5: Legislation This part touches briefly on the importance of legislations in construction industry and the Approved Documents that have been formulated to guide in building and construction. TABLE OF CONTENTS i.Portfolio Checklist 1 ii.Commentary 1 TABLE OF CONTENTS 2 1. Part 1: Questions 1. Densities in descending order Concrete Water Mahogany  Vermiculite  2. Mass of Lintel  Mass of rebars  3. Bulk density is a property used to describe materials existing in form of granules, powders or any other divide for. It is obtained by dividing the mass of all particles by the entire volume occupied. Total volume occupied includes the actual volume of particles, internal pore volume and antiparticle void volume. Solid density is the mass per unit volume of a solid material. 4. The three classes of stones are; igneous, metamorphic, and sedimentary. They are classified according to the process of formation, texture and chemical composition. Igneous stones are formed in the process of volcanic eruption. This is when magma cools down and condenses. They are further classified into two categories depending on the form in which they reached the earth surface. When magma cools and crystalize slowly on the earth crust, plutonic rocks are formed. On the other hand, volcanic rocks are formed when magma reaches the earth surface as fragmental ejecta or lava. Sedimentary rocks are results from deposition of organic matter, chemical precipitates, or clastic sediments and subsequent compaction of these particles. They are formed on the earth surface. Finally, metamorphic rocks are formed by subjecting other stones to extreme temperature and pressure conditions. 5. Out of the three classes of stones outlined above, sedimentary type of stones has the highest porosity ratio. The pores of sedimentary rocks are formed in the process of compaction and cementation. Therefore, there are numerous pores of varying sizes and shapes. 6. Examples Marbles are formed from metamorphic recrystallization of limestone. It falls in the category of metamorphic stones. Marble is very useful in construction especially as an aesthetic component. It is used more in decorative construction rather than structural usage. Sand stone is an example of sedimentary rock. It is a conglomerate of numerous sand grains bound together in a solid stone. Pumice is an example of igneous rock formed in the process of magma condensation. It is formed when lava cools slowly on the earth crust. Brick and Block 7. High porosity increases the value of water absorption coefficient. 8. Initial rate of absorption is the amount of water in grams absorbed over 30 square inches in one minute. Capillary action is the tendency of liquid to flow along a narrow tube or between the grains of stones. It occurs from intermolecular interaction between the liquid and solid material. The size of pores in a stone affects the rate of capillarity and initial rate of absorption. Initial rate of absorption is directly proportional to the sizes of pores. This implies that as the size of pores increase the initial rate of absorption increases too. Smaller sizes of pores increase the rate of capillarity. 9. Good bond is characterized by both chemical and mechanical elements. Water and cement which is the constituent of mortar get drawn in to the pores via capillary action. While hydration takes place, chemical bond is created between mortar and brick. Therefore, the brick must suck sufficient water and cement from the mortar to create a robust bond. Since IRA measures the rate of suction, it implies that the higher the Initial Rate of Absorption is, the stronger the bond. 10. Two adverse conditions arising from excess water in bricks The presence of too much water in the bricks prohibits the suction of water from the mortar. This implies that a strong bond cannot be created as required. 11. Metals Carbon is one of the constituents of steel. Various alloys have different impact on the ultimate properties of steel. For example the increase in amount of carbon in steel raises brittleness. In other words, steel with 0.3% carbon is less brittle that the one with 1-3%. Heat treatment processes 12. Heat treatment is the process of causing micro structural realignment by thermal alterations. Different heat treatment processes result in metals of varying properties. These heat treatment processes are; Annealing, Normalizing and Quenching. a) Annealing Annealing is a heat treatment process involving the heating of a metallic material to crystallization temperature. The temperature is held at this temperature for some time until the material is changed to either Austenite-Cementite or Austenite. The process is the n followed by slow cooling using natural convection at room temperature. The resultant structure is characterized by coarse Pearlite with Cementite or Ferrite. In this process, steel softens. b) Normalizing Normalizing is a heat treatment procedure whereby steel is heated up to approximately 100oF above Upper Critical Temperature. The process is the n followed by cooling in air until it attains room temperature. The process results in steel with improved machinability, refined grain structure and relatively desirable ductility without alterations of strength and hardness. c) Quenching Quenching is another heat treatment process involving heating the material to temperatures beyond Upper Critical Temperature and subjecting it to accelerated cooling by immersing it in water or oil. The process results in hardened and relatively more brittle steel than before. 13. High carbon steel is not suitable reinforcement for steel because it is brittle. High percentage of carbon in steel raises the levels brittleness in reinforcement steel. Reinforcement steel should be sufficiently ductile to be able to absorb shock without yielding. High carbon steel makes the structure to deform permanently in the event of excessive loading. On the other hand, low carbon steel can withstand loading for a long time without yielding. Even if it deforms, the deformation is not permanent because low carbon steel undergoes elastic deformation for a long time. Corrosion 14. When a metal is placed in an electrolyte, charge separation occurs suddenly around the areas of contact called interface. Although there is no current generated in the process, there is a notable dipole moment existing per unit area. This is due to the diffuse charge in the liquid and concentrated layer of charge with opposite sign in the solid metal. For alkali metals, the process leads to evolution of gas accompanied by continued dissolution of the metal. 15. Corrosion is the breaking down of material to form its constituent atoms because of chemical reaction with the environment. In metals, corrosion refers to electrochemical oxidation due to the interaction with oxidant such as oxygen. Corrosion is instigated by chemical reaction leading to disintegration of materials. Cathodic protection is a mechanism employed in controlling corrosion on metal surfaces through making the metal to be protected a cathode in electrochemical cell. Sacrificial anode is the material attached on a metal object such as an underground tank or boat to prevent corrosion. The anode is consumed electrolytically while the parent material is saved from corrosion. 16. Potential Hydrogen (pH), which is a measure of acidity of alkalinity of a substance, affects the rate of corrosion. As the pH of the surrounding tends to zero i.e. the acidity increases, the rate of corrosion increases. Cement, concrete and cement replacements 17. Cement replacement is the use sofa alternative materials in place of conventional Portland cement in concrete. The replacement can be partial or complete. Several materials have been identified as effective substitutes of The main reason of their use is because of their versatility. Use of cement replacement materials offers a variety of useful enhancements to the conventional Portland cement. 18. Hydration of cement entails the interaction of aluminate and anhydrous calcium silicate phases with water resulting in hydrated phases. Solid hydrates formed in the process of hydration occupy more space than anhydrous ones. Heat of hydration is refers to the heat generated in the chemical process associated to the setting of concrete between cement and water. Hydration process produces heat because the interaction of water and cement is an exothermic process. This is due to the fact that bond breakage is accompanied by release of heat energy. The amount of heat produced varies with different concrete mixes because the types of bonds broken are of different magnitudes. 19. Vulnerability of Portland cement to the attack of chlorides and sulphates can be reduced using GGBS and PFA. The pH of GGBS and PFA counteracts the acidic impact of chlorides and sulphates. 20. The amount of water in concrete affects the density, strength and durability of concrete. This is so because water is a critical component determining the bond formation and cement seepage into bricks. Excess water leads to detrimental impact on the quality of concrete. This is occasioned by additional shrinkage accompanying drying process. Aggregate 21. Characteristics of Aggregate Resistance to abrasion and degradation This characteristic is important in the determination of wear resistance on the pavements and floors. Resistance to freezing and thawing Resistance to freezing and thawing is important in determining roughness, surface scaling loss of section and most importantly, aesthetics. Resistance to disintegration by sulphates This characteristic determines the robustness against weathering action. It is a factor of whether there will be weight loss in concrete. 22. Porosity of concrete is the total volume of different forms of voids within the concrete. This may include capillary pores, entrapped air gel pores among others. It is given as a proportion of bulk rock volume without solid matter. It is given by; Where; Vs is the volume of solid, Vp is the pore volume given by Vp=V-Vs Grain shape is one of the characteristics determining the porosity of aggregate. Grain shapes are classified in to four types namely: sphere, cube, cylinder and disk. Each of these shape have different impact on porosity. Several studies have revealed that the porosity is larger on non-spherical grains than in spheres. For non-spherical grains porosity is higher on angular ones than in sub-spheres like cylinder and cubes. The table below shows how various shapes vary with porosity. Grain Shape Maximum porosity (fractional) Sphere ≥0.399 (depending on grain size) Cube 0.425 Cylinder 0.429 Disk 0.453 23. Chloride salts speeds up the rate of corrosion on reinforcing bar within concrete. Therefore, it has detrimental impact on the entire concrete. Chloride salts will always weaken the concrete. 24. Timber Cellular structure of hardwoods and softwoods from the transverse view 25. Coefficient of thermal expansion is the degree of expansion in a heated material per unit change in temperature. Although wood is known to resist temperature, its shift in temperature affects its strength. The strength of wood responds suddenly to changes in temperature. The strength decreases as temperature drops, and decreases with the increase on heat supplied. Changes in timber occurring because of temperature elevation are irreversible. 26. Modulus of elasticity is the tendency of a substance to deform temporarily upon the application of load. It is the ratio of stress against strain. Modulus of rapture is the measure of amount of load required to break a substance across its width.  M= Modulus of Rupture P=Breaking Load L=Distance between supporting edges b=Average Breadth of Specimen d=Average Depth of specimen 27. Forces of compression and tension acting would act on a timber sample during the static bending test 28. Plastics a) Nylon structure b) Polypropylene structure c) Polycarbonate 29. Plastics are poor conductors of heat. That is why they are chosen as insulation materials in most cases. There are those plastics which deform when subjected to fire while others are consumed by elevated temperatures. They are less hazardous as compared to timber. However, they can be good fuel in the event of fire outbreak. 30. Stress and Strain Curve The gradient of stress-strain graph is constant. It is usually referred to as Young’s Modulus denoted by E and expressed as: 2. Part 2 - Building Process 2.1 Members of a typical building team and their respective roles Project manager A project manager plays a very crucial role in a construction project. The project manager is responsible for the project in its initiation stage, planning stage, execution stage and also ensuring that the project will be completed in time and within the specified time allocation. For a project manager to be effective he or she must possess certain qualities. These qualities should include systematic management skills, ability to develop schedules, risk analysis, leadership skills, sequencing and planning. Project manager is appointed by the owner of the project and can be from outside or from within the owner’s staff members. The appointment of the project manager is done mostly in the feasibility stage of the project. He is responsible for advising the employer on the procurement of designs, time and cost estimates and in making the most appropriate choice on contact strategy. He is responsible to the employer in carrying out actions and decisions as is required of him. A close relation is maintained between a project manager and the employer so that the decisions he makes reflects the employer’s objectives. He also has the authority to give instructions to the contractor and to also change plans based on his engineering and managerial judgment (the engineering and construction contract, ECC). In reference to construction, a project manager is responsible for achieving the objectives of the project. Quantity surveyor A quantity surveyor is responsible of ensuring that the resources available at the construction site are utilized to the maximum advantage. He is also responsible for financial management of the project and the service of cost consultancy to the employer and the designer in the construction process. The quantity surveyor should ensure that he carries out feasibility studies on time labor and material in order to give a defined estimate. He is also responsible for preparing reports on preparation and also analysis cost for contacts and tenders. He is mandated to coordinate the work effort in the construction project and also providing advice on issues that relate to contractual and legal issues. Quantity surveyors should be equipped with qualities such as negotiation skills, financial, management skills and also a good knowledge of construction. The quantity surveyor plays a close role with the cost estimator as he prepares schedules that detail the quantities of the elements of the project. The quantity surveyor conducts his surveyor in various stages of the project. These stages include planning, designing and construction. Architect An architect is part of the human resources that are found in a construction project. He is the person who has had previous training in designing and planning. He is also responsible for overseeing constructions of buildings and any other physical structures. There are different roles that an architect fulfils. He has a role as a designer as he creates design concepts for clients and fulfilling their requirements. He also has the role in documentation. This means that he is responsible for giving detailed information on designs and drawings that are to be used by the contractors. The architect also plays the construction role. In this case he is responsible on the behalf of the client to place the projects on tenders. He reviews the progress of the construction and gives advice on the award to the contactor concerning the project. The architect also has the responsibility of ensuring that the drawings are accurate, complete and factual. Geo-technical specialist A geotechnical specialist plays an important role in engineering and construction as he applies geotechnical knowledge in soil and rock mechanics, engineering geology and other related disciplines. He then compounds the resulting information to give a report on whether the ground on which the construction is to take place is viable. Contractor The contactor has the sole responsibility for the actual construction of the project. He is usually in agreement with the proposed design and also in agreement to construct the design with the agreed sum of money. The contractor usually has a team of subcontractors, suppliers and fabricators who help him in executing the design. This is usually through the provision of materials with the architect’s documents. Cost estimator Due to the little information available, the cost estimator is responsible of conducting a final sum based on the completed and final contract. The accuracy for the cost estimator when placing the value on the complete final contract the value is reduced to +/- 10%. 2.2 Design process and the main principle requirements of a project Design process represents a chronological order of activities ranging from conceptualization stage to the actual ground breaking efforts. The details of a typical construction process are outlined below; Identification phase This is the genesis of any engineering project. All the parties must identify the kind of architectural object they need. Although it may not be detailed, the process must identify the overall feature of the building to be designed. For example, the owner may identify that he needs a two-bed roomed house. The identification must distinguish the structure to be developed from other conventional buildings. The identified building could be residential, commercial, institution, hospital or social hall. Definition phase Once the project has been identified, it is important to define the details of the project. This is the phase whereby the designer will apply the theoretical knowledge, experience and prevailing circumstances to define the details of the building. This phase is closely guided by the identified project in phase one. All the efforts at this phase are geared towards ensuring that the functional requirements of the final design are met. Specification phase Specification phase gives the precise details of the proposed design. The specifications must support the primary idea conceptualized by the owner. Furthermore, the specifications must meet the budgetary constraints of the project owner. Implementation Once the construction process has been designed, the most important part of implementation follows. In this process, the architectural models detailing design features may be developed. 2.3 Site Investigation Discuss the different types of site investigation and the purpose of each Desk-top study This is an investigation step whereby the concerned parties collect existing information of the site. Such documents as maps, drawings, aerial photos and public utilities are part of information portfolio critical to site selection. This study is important in determination of the suitability of the site in relation to the external environment. Site reconnaissance This entails a physical walk over the potential construction site to determine the visual look and topography and other natural features on the location. Ground and soil investigations This is the most technical investigation phase giving the precise details of the ground in which the construction will stand. On and off site tests on the soils and rocks found in the site are the most common activities of this phase. This kind of investigation helps in portraying the hidden feature of the ground which could not be seen with normal investigation. 2.4 Foundations Types of shallow foundations Isolated square footing Strip footing Combined footing Strap footing Types of deep foundations Large displacement Small displacement Non-displacement Shallow Foundations Shallow foundations are classified into two major types namely; Frost Protected Shallow Foundations (FPSF) and Conventional. FPSF is useful in protecting the building against adverse effects of frosting. It is ideal for the areas that are prone to frosting. On the other conventional shallow foundation is ideal for cases where comparatively less loads are anticipated. The two types of shallow foundations are illustrated below: Deep foundations Pile foundation Pier foundation 2.5 Ventilation Purpose of ventilation and the different types of ventilation Ventilation is a critical feature of every building. It ensures that there is adequate amount of fresh air within the building to sustain the occupants. It also offers a possibility of elimination of waste gases within the room. Approved Document F covers ventilation requirements within new dwellings, non-dwelling structures and existing buildings. Furthermore the document postulates that the mechanical ventilation control devises must pass testing and adjusting necessary to assure reliable functioning. The document classify ventilation into two types namely; infiltration and purpose-provided ventilation. Infiltration is the unmanaged interexchange of air between the internal and the external areas of a building through several air leakage channels. On the other hand, purpose-provided ventilation is the controllable interexchange of air between the outside and inside of a structure trough the use of mechanical devices or natural features. Discuss the term performance based ventilation It is a recommendation by the document to help in control of moisture and pollutants within the buildings. It postulates the acceptable levels of moisture and pollutants without causing harm to the occupants of the building. 3. Part 3 – Loads and Forces on Buildings 3.1 Types of loads and forces acting on a building 1. Compression, tension and shear 2. Bending, buckling and deflection 3. Moments 3.2 Compression and tension Compression is a force that tends to bring together the elements of a material to the closest possible distance. The direction of forces resulting from compression moves towards one another. Compressive force occurs in various parts of the building. The most common one is in the walls whereby the weight of the roofs imposes a compressive force on the side walls. The compressive force is as a result of the weight and reactive force from the ground. Tensional force occurs when force acting on opposing sides tends to pull an object apart. In a building, tensional forces occur during dry season whereby the surrounding ground shrinks. The shrinkage on the foundation imposes tensile force on the foundation. 4. Part 4 - Failure modes 4.1 Main aspects of behavior of plastics, steel, concrete and wood in fire conditions Different materials exhibit varying behaviors when subjected to extreme temperature like those of fire. The behavior is one of the yardsticks used in the selection of appropriate materials to be used in building. The main aspects are; flash point, ability to spread fire, and ability to with stand elevated temperatures. Plastics are the most vulnerable materials to fire consumption because their lash pints are lower. Slight increase in temperature can easily distort their shape and color. Wood products too have less resistance to fire as compared to other materials like steel and concrete. Their interaction with fire is a permanent change resulting in ash and charcoal depending on the amount of heat and oxygen supplied. 4.2 Failure modes that can occur within structures Failure mode is the manner in which failure has occurred. In the structures, failure can occur in either of the following modes; buckling, bending, cracking, shearing, twisting and breaking. The occurrence of any particular mode of failure is dictated by the type of force applied and the nature of failing member. 4.3 Failure Mode and Effect Analysis (FEMA) Failure mode and effect analysis is a detailed procedure used in safety engineering to ascertain the potential failure mode and their severity and likelihood of occurrence. 5. Part 5 – Legislation 5.1 Importance of the Building Regulations Building regulations are very critical in the construction industry. They help ensure that the buildings are constructed to the requirement of minimum standards. Since the regulations are enforceable by the law, contractors are left with no choice but to comply with these regulations. Among the many reasons why these regulations must be available is to ensure that the occupants are safe, the building materials and processes are environmental friendly and non-detrimental to the surrounding. 5.2 Different Approved documents 1. Approved Document A - Structure 2. Approved Document B: Volume 1 - Fire Safety: Dwelling houses 3. Approved Document B: Volume 2 - Fire Safety: Buildings other than dwelling houses 4. Approved Document C - Site preparation and resistance to contaminants and moisture 5. Approved Document D - Toxic substances 6. Approved Document E - Resistance to the passage of sound 7. Approved Document F - Ventilation 8. Approved Document G - Sanitation, hot water safety and water efficiency 9. Approved Document H - Drainage and waste disposal 10. Approved Document J - Combustion appliances and fuel storage systems 11. Approved Document K - Protection from falling, collision and impact 12. Approved Document L1A - Conservation of fuel and power in new dwellings 13. Approved Document L1B - Conservation of fuel and power in existing dwellings 14. Approved Document L2A - Conservation of fuel and power in new buildings other than dwellings 15. Approved Document L2B - Conservation of fuel and power in existing buildings other than dwellings 16. Approved Document M - Access to and use of buildings 17. Approved Document N - Glazing - safety in relation to impact, opening and cleaning 18. Approved Document P - Electrical Safety – Dwellings 19. Approved Document to support Regulation 7 - Materials and workmanship References Arya, C 2009, Design of Structural Elements: Concrete, Steelwork, Masonry and Timber, Taylor & Francis, Abingdon Ashby, MF 2007, Materials: Engineering, Science, Processing and Design, Butterworth- Heinemann, Oxford. Barry, R 2001, The Construction of Buildings, Blackwell Science Limited, Oxford Chung, Y 2007, Introduction to Materials Science and Engineering, Taylor & Francis, Oxford Domone, P & Illston, J 2010, Construction Materials: Their nature and Behaviour, Spon Press, Abingdon. Emmitt, S & Gorse, C A 2010, Barry’s Introduction to Construction of Buildings, Blackwell Publishing Ltd, Oxford. Hornbostel, C 1991, Construction Materials: Types, Uses, and Applications, John Wiley & Sons, Inc., London. Tunstall, G 2006, Managing the Building Design Process, Butterworth-Heinemann, Oxford Read More