Causality and logical fallacieis in old wives' tales and old farmer's Essay

Causality and logical fallacieis in old wives' tales and old farmer's tales (tales are given) - Essay Example y arise because of observing some instances where they became true, so people shared these stories as facts, and these beliefs are subsequently passed on to others. The flaws in the logical reasoning behind these tales are: first, non sequitur because conclusions about these superstitions do not necessarily follow from the premises; second, hasty generalization because anecdotal evidence does not support the external validity of superstitions; third, confusing cause and effect because factors that happen together are not always related as cause and effect; and fourth, appeal to fear because black cats are related to witchcraft and demons. The old wives’ tale about pregnant women shows non sequitur because the effect of having a child who becomes a musician does not always follow from the practice of listening to music while pregnant. The exact source of this superstition is not well-documented, although some of these stories are likely to come from European countries that are fond of listening to classical music in the past. These mothers might have been incidentally listening to music while pregnant, so when their children became musicians, they immediately attributed the latter’s musician skills to their pregnancy habits. Nevertheless, even if it was true for some mothers, it does not follow, which is non sequitur, that every mother who follows the same practice will also have children with musical skills. Believing in this relationship results to another fallacy called hasty generalization. Even if some pregnant mothers attest that they listened to music regularly while pregnant, and that this practi ce provided musical skills to their children, their small sampling cannot be applied to the entire population of mothers who follow the same habit. It will be hasty generalization to assume that the practice of a small group generates effects that are applicable for the whole population. Anecdotal evidence is not enough to prove the external validity of the

Environmental Problems, Mitigation Measures and Effectiveness Essay

Environmental Problems, Mitigation Measures and Effectiveness - Essay Example The other anthropogenic activity is destruction of the natural environment by unsustainable use of resources, a factor that has also resulted in world climate changes (Dalby, 2002: 44). Atmospheric pollution is the main cause of global warming; it results from the accumulation of carbon IV oxide and other greenhouse gases in the atmosphere, trapping heat from the sun in the earth’s atmosphere. Greenhouse gases are by-products of industrial combustion, which means that the extent to which a country contributes to global warming by these gases depends on the level of industrialization; a high level of industrialisation causes increased consumption of fossil fossils. Fossil fuels like natural gas, oil and its products have a high carbon content that is released in huge quantities and at a faster rate than can be sequestered by natural carbon sinks like forests and oceans. In this case, first world nations and rapidly developing third world nations are the main contributing agents to environmental degradation by industrial pollution. On the other hand, environmental degradation can occur due to unsustainable use of natural resources like forests and water bodies; this is a serious problem in developing countries (Adil, 2005: 315). The economies of these countries are primarily agricultural based; the high rate of population growth necessitates high agricultural production for food security. However, deteriorating climatic conditions have reduced the productivity of land in these areas, forcing people to clear more forests for agricultural purposes. Consequently, forests that play a role in precipitation are destroyed, and the areas receive less rainfall; this has a negative effect on agricultural productivity, which forces further clearance of forested areas. This cycle goes on and on until many of productive lands have become barren, especially due to poor farming practices and the dependence on rains for agriculture in these countries. Some of the effects of environmental degradation include loss of biodiversity; decreasing ice coverage on mountain tops and poles that pose a threat to sustenance of the hydrological cycle; and desertification by loss of vegetation cover. Moreover, it causes climatic changes like extreme weather conditions whereby dry areas get drier, hot areas hotter, and wet areas wetter; and a rise in sea level that destroys sceneries and property (Barry and Eckersley, 2005: 255). Based on the economic implications of these changes and their threat to survival of life in the planet, governments and international organisations have taken measures to mitigate the effects of the environmental problems that result from these changes (Carter, 2001: 282). These measures target the two main aspects of environmental degradation including pollution and unsustainable use of resources; there have been some level of success though with some limitations too. This paper discusses the measures taken by governments and internationa l organisations; the extent of success of these interventions; the limitations facing effective implementation of interventions; and the consequences of these measures. Intervention Measures Governments have come up with environmental policies that aim at encouraging adoption of environmentally sustainable approaches by their citizens. For instance,

Advantages of Composite Construction

Advantages of Composite Construction With regards to Civil and Structural Engineering, composite construction typically refers to the use of steel and concrete formed together so that the resulting component behaves as a single element. The aim of composite construction is to utilise the best properties of the different materials and to deliver performance that is greater than had the individual components been used together but not unified. In the case of steel and concrete, the best properties would be the tensile capacity of the steel and the compressive capacity of the concrete. (Nethercot, 2004) Composite construction is an effective method of construction and delivers good performance. The methodology for designing composite structures has been researched in great detail. For these reasons, composite construction is a very popular method of construction around the world. In order for the materials to behave as one element, it is necessary for some method of connecting the two materials. A shear connection between two materials will enable composite action between them. (The Institution of Structural Engineers) 2.1.1 Benefits of Composite Construction The benefits of composite construction include speed of construction, performance and value. Steel framing for a structure can be erected quickly and the pre-fabricated steel floor decks can be put in place immediately. When cured, the concrete provides additional stiffness to the structure. Additionally, the concrete encasement protects the steel from buckling, corrosion and fire. Service integration within the channels on the composite decks is another advantage to composite construction. Building quality standards can be adhered to easily by the use of pre-fabricated decks. Excessive deflections can be controlled by cambering the beams or by shoring the metal decks to limit deflection when concrete is poured. 2.1.2 Codes for the Design of Composite Structures The design of composite structures was governed by the British Standards. BS 5950-3-1 dealt with the design of beams whilst slabs were governed by BS 5950-4. Pre-fabricated decking used with composite structures was governed by BS 5950-6. Since the introduction of the Eurocode set of standards for the European Union, the design of composite structures is standardised by Eurocode 4. (BS EN 1994-1-2) (BCSA; TATA Steel; Steel Construction Institute) 2.1.3 The Principle of Composite Action The principle of Composite Action underpins the use of composite materials in construction. It relates to the interaction of two or more separate elements acting together and contributing together rather than separately. By physically connecting them, the strength of the beams and the resistance to bending, shear and torsion are significantly increased. The Principle of Composite Action is best illustrated as an example. The diagrams below shows two uniform concrete beams placed on top of each other and loaded with a uniformly distributed load. Both beams will resist the load independently and there will be relative movement between them. The bending strength will be the sum of the individual beams contribution. If the beams have width w and height h, the bending strength M will be: However, if the two beams are connected rigidly together by shear connectors and the relative movement between them is eliminated, the width remains w whilst the height becomes 2h. The bending strength M will be: This represents a doubling of the bending strength through the use of composite action. This is the principle behind the use of steel beams with reinforced concrete floor decks. The two are connected by shear connectors. The increase in strength due to composite action can be as much as 20%, resulting in lighter and thinner sections. (TATA Steel) Figure : The differences between identical beams when composite action is utilised. The beam on the left is comprised of two concrete beams that are not connected compositely. When loaded, there is relative slip between the beams. The component beams on the right are rigidly connected together by means of shear connectors. When loaded, there is no slip between the beams and the assemblage behaves as one large beam. Image from TATA Steel. 2.2 Composite Floor Deck Slabs Composite floor decks are comprised of either steel beams or concrete embedded steel beams together with a reinforced concrete slab. The profiled steel formwork that supports the concrete floor during casting is of vital importance as it also provides the shear bond to enable the materials to work compositely. The role that the profiled decking plays in fire resistance will be discussed in more detail in Section 3.3. Composite action is achieved between the beams and slab by the use of shear connectors that will be discussed in Section 2.4 in more detail. (Metal Cladding and Roofing Manufacturers Association, 2003) The profiled steel decking used in the construction of composite floor systems contributes significantly to the ease and speed at which the structure is construction. It acts as both the permanent formwork and contributes to the overall requirement of reinforcement. The performance of the steel decking when exposed to fire needs careful consideration and is dealt with in Section 3.2. Additional reinforcement is positioned in the troughs of the decking to ensure adequate performance in fire. Benefits associated with using profiled steel decking are reduced dimensions and weight of the overall structure. They also provide satisfactory performance in the areas of strength and economic constraints during construction. (Michel Crisinel, 2004) 2.2.1 Types of Composite Slabs The classification of composite slabs depends primarily on the geometry of the steel deck profile used. Shallow decks are classified by depths in the range of 120-200mm whilst deep decks are classified by depths in the range of 200-350mm. (Aida Rodera Garcia) The most common composite slab consists of the profiled steel decking and concrete cast in-situ. Once cured the concrete and decking act compositely. Sufficient interaction between the concrete is achieved by a chemical bond and a mechanical bond facilitated by the shape of the decking. In design, it is common to neglect the contribution from the chemical bond as it is unreliable. There are many different types of profiled decking available and contribute to the classification of the slab. (Nawy, 2008) Pre-cast concrete slabs can also be used to form a composite floor deck system. The slabs must be designed specifically so that they can interact with the beam system in place. The composite action in this case can be achieved by welded shear studs and transverse reinforcement across the floor deck. By utilising pre-cast concrete decks, hollow core slabs can be used. These can reduce the weight of the whole building whilst offering similar performance to solid slabs. Pre-Cast slabs are usually covered by a layer of concrete after installation to produce a more finished and aesthetic result. Figure : Examples of Hollow-Core Slabs The final type of composite floor slab is the Slim Floor. This consists of the supporting steel beam being encased in the concrete with the lower flange of the beam supporting the floor. Diagrams depicting the various composite slab types in use today are shown below. Figure 4: Proprietary Slim Floor System Slimdek- TATA Steel Figure 3: Example of Solid Slab with Topping and Encasement cast In-Situ Proprietary Slim Floor System Slimdek- TATA Steel http://ars.els-cdn.com/content/image/1-s2.0-S0143974X99000759-gr5.gif 2.2.2 Design Composite floor decks are comprised of permanent formworks of profiled steel decking. The decking serves to support the concrete during casting and before it has cured sufficiently to support itself. It is important to ensure that after curing sufficient interaction between the concrete and steel has developed so that the assembly behave compositely. The rebar is placed in the steel decking prior to pouring as is a steel mesh that serves to minimise cracking over supports and to increase the fire resistance of the floor deck. Most decks achieve a satisfactory degree of shear connection with the concrete by the presence of embossments and indentations along the profile of the decking. This type of shear connection is known as a shear bond. (Steel Construciton Institute, 1994) The decking also contributes to the stabilisation of the structure against lateral torsional buckling of the steel supporting sections and transfers wind loading forces to the walls and columns. The decking also serves to minimise cracking of the concrete slab during expansion and contraction such as during curing and fire. This will be further discussed in Section 3. (Aida Rodera Garcia) The steel decking is normally in the range of 0.9-1.5mm thick and has a yield strength of 280-350 N/mm2. Higher strength steels may be used if the spans are longer than the norm. Typical spans for a composite floor deck are between 2.7 and 3.6m although longer spans may be achieved by shoring the deck during construction. Galvanisation of the faces of the decking is done to prevent damage to the steel during pouring and in service. 2.2.2.1 Concrete Type Strength Both Normal Weight Concrete (NWC) and Light Weight Concrete (LWC) may be used in composite floor slab construction. The most convenient method for concrete placement is by pump. The concrete type and grade is an important design consideration as it affects the final stiffness of the deck system and the strength of the shear connection. 2.2.2.2 Steel Decking Resistance The elastic moment resistance of the steel decking may be calculated from the effective breadth of the steel elements in compression. Stiffeners are present in the deck design and contribute to increasing the effectiveness of the section. In designing a deck system, moment redistribution is not allowed. This results in an underestimate of the critical load for the decking. (ECCS, 1993) 2.2.2.3 Deflection Deflection limits for a composite slab are generally the span/180. However, by shoring the composite slabs during casting, this can effectively be reduced to zero. Increased deflection limits of span/130 are allowed if pooling of the concrete occurs in the middle of the span after pouring. (ECCS, 1993) 2.2.2.4 Transverse Reinforcement The strength of the concrete should be checked to ensure it is capable of receiving the force transferred from the shear connectors. Where the concrete may be susceptible to cracking, the provision of transverse reinforcement perpendicular to the beam is required. (Aida Rodera Garcia) 2.2.3 Failure The ultimate moment resistance of a composite slab is defined as the point at which less than 2mm of longitudinal slip has occurred between the concrete and the decking. Failure of a composite deck is deemed to have occurred when slip of more than 2mm occurs. Failure most commonly occurs during curing before the concrete has reached its design strength. 2.2.4 Fire Resistance of Composite Sections The minimum slab depth will be determined by the fire insulation requirements and the amount of reinforcement that is necessary to withstand loading at the fire limit state. This will be dealt with in more detail in Chapter 3. 2.3 Composite Beams A composite beam can be structurally described as a T-Beam, with the top flange composed of concrete in compression and the steel section in tension. Forces between the two materials are transferred by shear connectors. The principle of composite action with regards to beams leads to increased strength and stiffness of the system whilst using a smaller steel section. The two main variants of composite beams used today are shown in Figure 6. Beams are usually composed of a UKB or UKC section, partially or fully encased in concrete for strength and fire resistance purposes. (ECCS, 1993) 2.3.1 Design In composite beam design, the steel section is first sized to adequately support all the loads acting on it. No contribution is taken into account from the concrete as it has not gained adequate strength for composite action. A common value for the load applied to the beam from the concrete slab is 0.75kN/m2. Once the loading has been calculated, the beam is designed according to Eurocode 3. The presence of steel decking normal to the steel section provides lateral restraint to the beam. In this case, the beam can reach its full plastic moment. In cases where the presence of steel decking is parallel to the beam, the beam is only laterally restrained at the connections at either end and the buckling resistance of the beam must be calculated based on its effective length. The effective breadth of the concrete flange, taken from the supported slab, is approximated as the span/8 on both sides of the beam. This results in an effective breadth of span/4 for simply supported internal beams. 2.4 Shear Connectors Shear connectors are an essential element of composite construction if it is to perform adequately. The main purpose of the shear connector is to provide longitudinal shear resistance between the materials so that they act compositely and to facilitate the interaction between the different materials and to allow them to act as one. (MCRMA, 2003) The shear connection between steel beams and concrete slabs is typically achieved by headed steel studs, welded to the top flange of the steel beam and subsequently encased in concrete. The performance of the studs depends on their dimensions and the spacing along the flange of the beam. Near supports, where the shear forces are greatest, the spacing is reduced. Shear studs can be welded through steel decking. Welding shear studs to the steel beams has a number of limitations and guidelines. The flange of the steel beam has to be bare and can not contain any contaminants such as intumescient paint used as fire protection or moisture. This method also works best when the thickness of the steel decking is less than 1.25mm. Weather conditions will also affect the use of this method of connection. Excess moisture in the air can result in the finished weld being brittle and prone to sudden failure. Shear connectors can also be placed during production although mistakes in placement can be difficult and costly to correct. The purpose of a shear connector is to primarily resist lateral shear forces and displacement between the beam and concrete slab. However, they are also designed to prevent upward displacement of the slab from the beam as it has a tendency to do. For this reason, the studs are headed to provide vertical resistance to seperation. 2.4.1 Types of Shear Connectors In the past, the most common method of shear connection was a headed stud. As welding is only suitable for decking with a minimum thickness, where the decking is too thin, nailed studs are used instead. The choice of which shear connector is used ultimately depends on the shear resistance required and the grade and strength of concrete used. There are four main types of shear connector in use today. The most common is the headed stud. However, with the advent of thinner composite decks, the use of headed studs is not practical. This had led to the introduction of nailed sheets of shear connectors. The dimensions of the most common stud are 19mm x 125mm and the method of connection to the steel beam is ceramic disk welding. (Aida Rodera Garcia) 2.4.1.1 Headed Studs The most common form of connecting materials compositely is with the use of headed shear studs. The behaviour of headed studs does not vary significantly when concrete properties are changed. Resistance to shear depends on the number of studs used and performance is less that that achieved by more modern shear connectors such as the Perfobondstrip or a welded T-Section. (Zingoni, 2001) The advantages of stud connectors is that the welding process is quick and simple, the placement of the studs does not interfere with the placement of reinforcement within the slab and they provide uniform resistance to shear in all directions normal to the axis of the stud. (Johnson, 2004) 2.4.1.2 Oscillating Perfobondstrip The curved form of an oscillating perfobondstrip provides better force transfer between steel and concrete than a continuous strip. The load capacity of this connector is larger than a headed stud or welded T-Section. This form of connector is most suited to light weight concrete or high strength normal weight concrete. Problems with this form of connection are difficulties in welding the section to the steel beam. (Zingoni, 2001) 2.4.1.3 Continuous Perfobondstrip The continuous perfobondstrip is similar to the oscillating perfobondstrip but achieves lower resistance values in all categories of concrete type and grade used. For this reason it is not as widely used as the oscillating form although welding is easier. 3.3.1.4 Welded T-Section Welded T-Section connectors perform very well in comparison to headed studs and achieve the same load resistance as oscillating perfobondstrip. Load capacity increases when Light Weight Concrete or high strength concrete is used. The strength comparisons of the shear connectors described above are shown in Table 1 below. The results were obtained from Galjaard and Walraven (2001) from tests carried out to Eurocode 4 standards for push-out resistance. It can be seen that large differences in resistance and ductility were observed. (Aida Rodera Garcia) 2.4.2 Shear Connector Design The choice of which shear connector design is open so long as it possesses the ductility and provides the necessary shear and separation resistance to the composite system. Headed studs are the most common form of connection and the design of such will be dealt with in this section. The design of shear connectors and composite slabs is given in Eurocode 4. Partial safety factors (ÃŽÂ ³v) of 1.25 for ultimate, 1.0 for serviceability and 1.0 for fire are specified in the codes. (Steel Construciton Institute, 1994) 2.4.2.1 Spacing The correct placement of studs along the upper flange of the beam is of great importance. It is important that the flange of the beam be clean, dry and free of contaminants such as paint or fire protection material. A number of conditions for the placement of studs are described below. The upper flange thickness may not be less than 40% of the diameter of the headed stud. After pouring, the head of the stud should have a minimum of 20mm cover. The minimum edge spacing of the headed studs is 20mm, to facilitate welding. Transverse spacing of headed studs must be greater than or equal to four times the diameter of the headed stud. Longitudinal spacing of the headed studs must lie between the minimum of five times the diameter of the headed stud and the maximum of 800mm or six times the overall depth of the slab, whichever is smaller. (ECCS, 1993) 2.4.2.2 Resistance of Shear Connectors The failure of a composite floor deck slab and the failure of shear connectors occurs due to either the strength of the concrete being surpassed or the strength of the weld connecting the studs to the flange of the beam failing. Shear connection design resistances are taken as the minimum of either the concrete or the headed stud. The equations for the design resistance of the concrete and the headed stud are given below. Where: d is the diameter of the headed stud. The ultimate tensile strength (fu) is most commonly 450N/mm2 and should not exceed 500N/mm2. The characteristic cylinder strength of the concrete is given by fck. Ec is the mean value of the secant modulus of the concrete. The values for different concrete strengths are given in the Annex Table 4. The value for ÃŽÂ ± is governed by the ratio of the height of the slab to the depth. The values of ÃŽÂ ± are given below. For 3 à ¢Ã¢â‚¬ °Ã‚ ¤ h/d à ¢Ã¢â‚¬ °Ã‚ ¤ 4, ÃŽÂ ± = 0.2(h/d +1) For h/d > 4, ÃŽÂ ± = 1.0 The partial safety factor () given by 1.25 in the ultimate limit state. (ECCS, 1993) Figure 10: Bearing stress on the shaft of a Headed Stud Connector (Johnson, 2004) 2.4.2.3 Degree of Shear Connection The degree of shear connection is based on whether the required numbers of shear connectors necessary for the composite beam to develop its full plastic moment have been installed. If fewer than the required amount necessary have been installed, the moment resistance of the composite system will be less than the maximum. The degree of shear connection is given by the equations below. Where Rc denotes the compressive resistance of the concrete slab and Rs denote the tensile resistance of the steel section. Both values are given by the equations below. Where hc is the depth of the concrete slab above the profiled decking. Eurocode 4 also provides provision for the minimum for the degree of shear connection based on the span (L) of the composite beam. These ratios are given below. For: L à ¢Ã¢â‚¬ °Ã‚ ¤ 5m, N/Nf à ¢Ã¢â‚¬ °Ã‚ ¥ 0.4 5m à ¢Ã¢â‚¬ °Ã‚ ¤ L à ¢Ã¢â‚¬ °Ã‚ ¤ 25m, N/Nf à ¢Ã¢â‚¬ °Ã‚ ¥ 0.25 + 0.03L L > 25m, N/Nf à ¢Ã¢â‚¬ °Ã‚ ¥ 1.0 (ECCS, 1993) Chapter 3 Composite Steel Deck Floors in Fire 3.1 Background The performance of composite steel deck floors in fire has been much studied to assess the design considerations that must be implemented and for designing the rules for reinforcement placement. In general, composites perform well in fire due to the insulating properties of concrete and the role of correctly placed mesh reinforcement and metal decking. (BCSA, Corus, SCI, 2007) Research conducted in the UK has concluded that previous methods of designing composite floor decks for fire scenarios was over conservative and that composite floor performance in many common fire scenarios was satisfactory. (Steel Conctruction Institute, 1991) Composite steel deck floor systems are typically not provided any fire protection material although the supporting beam to which the floor is connected is fire protected. The profiled decking of a composite floor acts as some of the tensile reinforcement of the system. For this reason, it is important to account for the effects that elevated temperatures will have on the decking. (Steel Conctruction Institute, 1991) The main contributor to the fire resistance of a composite slab is the embedded rebar mesh in the slab. As the temperature of the profiled decking increases in a fire scenario, the resistance that it provides is neglected. Additional reinforcement in placed in the slab to compensate for the loss of strength of the decking at elevated temperatures. The embedded reinforcement mesh is insulated by concrete and maintains a temperature sufficient for load bearing at the fire limit state. The positioning of rebar within composite floors typically results in higher concrete cover compared to normal reinforced concrete slabs. This results in good fire performance as the temperature of the reinforcement will rarely approach critical levels. The positioning of the reinforcement in the upper of the slab also contributes to controlling spalling in fire. The decking of a composite does play an important role however in maintaining the integrity of the concrete slab during fire. It limits the passage of flame and hot gases into direct contact with the concrete and controls spalling. 3.2 Load Resistance in Fire Design of composite slabs in fire conditions is based on the ultimate limit state properties. A composite floor slab is assumed to behave in bending as either a simply supported or continuous element. The load resistance of a composite floor deck system is due to the floor behaving as a reinforced concrete slab with loads being resisted by the bending action of the slab. Failure of a slab in fire occurs as a result of reinforcement failure. (Corus Construction Industrial, 2006) 3.2.1 Methodology There are two main methods for calculating the fire resistance efficiency of a composite floor deck system, referred to as the fire engineering method and the simplified method. 3.2.1.1 Fire Engineering Method The fire engineering method is based on the assumption that in the fire limit state, the plastic moment capacity of the floor is reached at higher temperatures and that redistribution of moments occurs where the slab is continuous. Temperature gradient experiments have produced temperature profiles such as those present in the Eurocodes. These profiles can be used to calculate the capacities of the beam in both hogging and sagging bending. The capabilities of the beams in the fire limit state can then be assessed. 3.2.1.2 Simplified Method The simplified method involves little or no calculation and relies on test data of actual fires to design the reinforcement in the composite slab. The density of the mesh can be adjusted to account for point loads and increased moment around supports. In general, the simplified method will deliver a result that demands less reinforcement in the design whilst the fire engineering method will allow greater flexibility in positioning the reinforcement and customising fire resistance time periods. The use of different grades of concrete will affect the dimensions and composition of a composite slab. Light Weight Concrete (LWC) has better insulating properties versus Normal Weight Concrete and its use will result in thinner slabs. 3.2.1.3 Design Period Deflection Limits The fire resistance of a composite floor deck system is measured as the time that a floor system can maintain sufficient load-carrying ability, maintain its integrity or by limiting heat transfer through the slab. The load-carrying ability of the composite floor system is measured by the amount of deflection that the system undergoes during fire exposure. Deflection greater than the span/30 is deemed critical as is a deflection rate greater than span2/9000d mm/min between deflections equalling span/30 and span/20. The integrity of the composite floor is deemed satisfactory for fire resistance if it can limit the passage of flame and hot gases. The insulating properties of concrete are deemed sufficient for fire resistance if after fire exposure, the upper surface temperature of the concrete slab remains below 140 °C. (Steel Conctruction Institute, 1991) 3.2.1.4 Reinforcement Fire resistance of a composite deck is attributed to the positioning of reinforcement in a mesh configuration within the slab. The most common forms of mesh are A142 mesh (6mm wires at 200mm c/c) and A193 mesh (7mm wires at 200mm c/c), the numbers referring to the cross-sectional area of steel per metre run, although larger gauges may be used if necessary. The tensile strength of the reinforcement is typically 450-500N/mm2. The positioning of the mesh is in the upper portion of the slab with a minimum cover and can be arranged to resist hogging or sagging bending or a combination thereof. (Aida Rodera Garcia) 3.3 The Fire Engineering Method The fire engineering method for composite slab design is discussed in this section. The partial safety factors at the fire limit state for materials and loads are outlined below. Materials: Steel: ÃŽÂ ³mr = 1.0 Concrete: ÃŽÂ ³mc = 1.3 Loads: Dead: ÃŽÂ ³fd = 1.0 Imposed ÃŽÂ ³fi = 1.0 3.3.1 Materials In conjunction with a suitable design fire scenario, it is possible to account for the reduction in strength of both the reinforcement and the concrete in fire conditions. With elevated temperatures, a reduction factor K may be used to account for the loss of strength associated with the increase in temperature. The table of reduction factors is given in Annex Table 5. The equations used for assessing the design strengths of the reinforcement and concrete at elevated temperatures including the reduction factor (K) are given below. Reinforcement: Concrete (Steel Conctruction Institute, 1991) 3.3.2 Depth The minimum depth of the concrete slab is taken from the tables below. Different values are obtained depending on the type of decking used, such as trapezoidal or re-entrant, and the concrete grade. This minimum depth satisfies the insulation requirement for composite slabs during fire exposure. Alternatively, the minimum depth may be taken from experimental test results from buildings of a similar design. (Steel Conctruction Institute, 1991) (Aida Rodera Garcia) 3.4 The Simplified Method The simplified method consists of installing a layer of mesh (A142, A193 or similar) in the upper layer of the concrete. One of the main differences between the Fire Engineering Method and the Simplified Method is that relatively few calculations are required for the Simplified. An outline of the Simplified Method is a follows: Imposed loads on a composite floor deck slab should not exceed 6.7kN/m2. The mesh size is chosen based on the required fire resistance period and the span of the slab. The minimum cover to any part of the mesh must be at least 15mm and not greater than 45mm. The span of a composite floor slab designed using the Simplified Method is typically 3.6m although spans greater than this may be used if adequate calculation is carried out. 3.5 Comparison of Methods While no method is definitively better than the other, they both have advantages over the other. The Simplified Method is more economical and is based directly on test results and not on theoretical calculation, which has a tendency to under-estimate the strength of materials. The Simplified Method also takes into account the contribution from the profiled steel deck even though the contribution may be small compared to that from the reinforcement mesh. The Fire Engineering Method however allows great flexibility in the customisation of the reinforcement and fire resistance periods. It is generally more expensive to design using this method as opposed to the Simplified Method though will result in thinner slabs that utilise more reinforcement. 3.6 Shear Connectors in Fire The performance of shear connectors in fire has not been widely studied. One of the major research projects on shear connectors in fire was The Restrained Beam Test conducted by British Steel as part of the Cardington Fire Tests in January 1995. The test consisted of the heating of a secondary beam and an area of the surrounding slab on the seventh-floor of the test structure. The steel section tested was a 305165 UB40 that was heated along 8m of its 9m length. Only the top 70mm of the concrete slab was taken into account. This was the maximum height of the slab above the troughs of the profiled decking. (Huang, Burgess, Plank, 1999) The temperature distributions in the steel beam and concrete slab were taken as averages of the test results recorded across the cross-sections of the components. The temperature of headed studs exposed to fire was approximated as 75% of the temperature reached by the top flange of the steel section. (Huang, Burgess, Plank, 1999) The degree of shear connection in the heated beam was assumed to be partial whilst the rest of the composite floor deck systems in the surrounding area were modelled as having full shear interaction. Analysis of the test results showed that the deflection at the mid-span of the heated beam increased with temperature. It was concluded from this that the assumption that partial interaction was corre

WHITE BLOOD CELLS Essay -- essays research papers fc

White Blood Cells Bacteria exist everywhere in the environment and have continuous access to the body through the mouth, nose and pores of skin. Further more, many cells age and die daily and their remains must be removed, this is where the white blood cell plays its role.   Ã‚  Ã‚  Ã‚  Ã‚  According to this quotation, without white blood cells, also known as leukocytes, we would not be able to survive. White blood cells are our body’s number one defense against infections. They help keep us clean from foreign bacteria that enter our bodies. Statistics show that there are five to ten thousand white blood cells per micro liter of blood, however this number will increase during an illness. White blood cells can differ in many ways, such as, size, shape and staining traits. There are five different kinds of white blood cells that fall into two separate categories. One category is called, granular leukocytes, and the other is called agranular white cells.   Ã‚  Ã‚  Ã‚  Ã‚  There are three different types of granular leukocytes. Neutrophil is a phagocyte, produced in the bone marrow that ingests and destroys bacteria extremely fast. Neutrophil has a diameter, which is, about ten to twelve micrometers long. They make up about 60-70 percent of the total number of white blood cells in our body. Eosinphil is a type of white blood cell that secretes poisonous materials in order to kill parasites, allergies and phagocytosis of bacteria, which is when the...

Child Care

NCFE LEVEL 2 CERTIFICATE IN SUPPORTING TEACHING AND LEARNING IN SCHOOLS Support disabled children and young people and those with special educational needs Outline the legal entitlements of disabled children or those with SEN (1. 1) Legislation| Details| Education Act (Handicapped Children) 1970| | The Warnock Report (1978)| | Education Act (1981)| | Education Reform Act (1988)| | Children Act (1989)| | Education Act (1993)| | Disability Discrimination Act (1995)| | Special Educational Needs and Disability Act (SENDA)/Special Educational Needs (SEN) Code of Practice 2001| | Every Child Matters: Change for Children (2004)| |Describe the assessment and intervention frameworks for disabled children and those with SEN (1. 2) Assessment/Intervention Framework| Details| SEN Code of Practice 2001| | Early Years Action / School Action| | Early Years Action Plus / School Action Plus| | Statement of Special Educational Need| | The Common Assessment Framework (CAF)| | What are the benefits of e arly recognition and intervention for disabled children and young people and those with special educational needs? (1. 3)| Describe the purpose of individual plans for disabled children and young people and those with special educational needs? 1. 4)| Describe the principals of working inclusively with disabled children and young people and those with special educational needs. (1. 5)| Describe the relationship between disability and special educational needs? (2. 1)| Describe the nature of the particular disabilities and/or special educational needs of children and young people with whom you work (if you work with several different pupils base your answer on just 1 of them) (2. 2)| Describe the special provision required by the pupils that you work with (2. 3)| Child Care NCFE LEVEL 2 CERTIFICATE IN SUPPORTING TEACHING AND LEARNING IN SCHOOLS Support disabled children and young people and those with special educational needs Outline the legal entitlements of disabled children or those with SEN (1. 1) Legislation| Details| Education Act (Handicapped Children) 1970| | The Warnock Report (1978)| | Education Act (1981)| | Education Reform Act (1988)| | Children Act (1989)| | Education Act (1993)| | Disability Discrimination Act (1995)| | Special Educational Needs and Disability Act (SENDA)/Special Educational Needs (SEN) Code of Practice 2001| | Every Child Matters: Change for Children (2004)| |Describe the assessment and intervention frameworks for disabled children and those with SEN (1. 2) Assessment/Intervention Framework| Details| SEN Code of Practice 2001| | Early Years Action / School Action| | Early Years Action Plus / School Action Plus| | Statement of Special Educational Need| | The Common Assessment Framework (CAF)| | What are the benefits of e arly recognition and intervention for disabled children and young people and those with special educational needs? (1. 3)| Describe the purpose of individual plans for disabled children and young people and those with special educational needs? 1. 4)| Describe the principals of working inclusively with disabled children and young people and those with special educational needs. (1. 5)| Describe the relationship between disability and special educational needs? (2. 1)| Describe the nature of the particular disabilities and/or special educational needs of children and young people with whom you work (if you work with several different pupils base your answer on just 1 of them) (2. 2)| Describe the special provision required by the pupils that you work with (2. 3)| Child Care NCFE LEVEL 2 CERTIFICATE IN SUPPORTING TEACHING AND LEARNING IN SCHOOLS Support disabled children and young people and those with special educational needs Outline the legal entitlements of disabled children or those with SEN (1. 1) Legislation| Details| Education Act (Handicapped Children) 1970| | The Warnock Report (1978)| | Education Act (1981)| | Education Reform Act (1988)| | Children Act (1989)| | Education Act (1993)| | Disability Discrimination Act (1995)| | Special Educational Needs and Disability Act (SENDA)/Special Educational Needs (SEN) Code of Practice 2001| | Every Child Matters: Change for Children (2004)| |Describe the assessment and intervention frameworks for disabled children and those with SEN (1. 2) Assessment/Intervention Framework| Details| SEN Code of Practice 2001| | Early Years Action / School Action| | Early Years Action Plus / School Action Plus| | Statement of Special Educational Need| | The Common Assessment Framework (CAF)| | What are the benefits of e arly recognition and intervention for disabled children and young people and those with special educational needs? (1. 3)| Describe the purpose of individual plans for disabled children and young people and those with special educational needs? 1. 4)| Describe the principals of working inclusively with disabled children and young people and those with special educational needs. (1. 5)| Describe the relationship between disability and special educational needs? (2. 1)| Describe the nature of the particular disabilities and/or special educational needs of children and young people with whom you work (if you work with several different pupils base your answer on just 1 of them) (2. 2)| Describe the special provision required by the pupils that you work with (2. 3)|

Polyhydroxybutyrate Phb

Polyhydroxybutyrate PHB Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class. Progress Analysis: – Bacteria first used to make PHB in 1925 at Pastuer Institute in Paris. – In 1970’s adopted by Imperial Chemical Industries (ICI) – Alcaligenes Eutrophus grown in fermentation vats with Molasses – The bacteria is then starved of nutrients (glucose and nitrogen) – PHB is produced as an energy store for the bacteria. In 1980’s Maddison University (Virgina) successfully cloned the 3 genes of A. Eutrophus that control PHB production and transferred them to Escherichia coli – an easier bacteria to work with allowing easier manipulation of the polymer depended on the need. – In 1990’s the 3 genes were cloned into sugar beets and turnips – much larger scale production of polymer. Work continuing (with Monsanto – company bought patent) into cloning genes to corn. Production: The manufacturing process of PHB begins with sunlight.Through photosynthesis carbon dioxide from the atmosphere is converted to carbohydrates via sugar beets or sugar cane. These carbohydrates (like Lactose, Fructose and Glucose) are the raw material for the manufacturing of PHB. Uses: †¢In medicine, PHB is compatible with the blood and tissues of mammals. The monomer of PHB is a normal metabolic in the human blood. As the body reabsorbs PHB it might be used as a surgical implant, in surgery, as seam threads for the healing of wounds and blood vessels. In pharmacology, PHB can be used as microcapsules in therapy or as materials for cell and tablet packaging. †¢In packaging for deep drawing articles in the food industry, for example, bottles, laminated foils, fishnets, potted flower, hygiene, fast food, one-way cups, agricultural foils and fibres in textile. Advantages of PHB: †¢Good mechanical properties, especially when low density and price are taken int o account. †¢Recyclable, renewable and non-abrasive to manufacturing equipment. †¢PHB is hydrophobic, therefore protects natural ? res from moisture sensitivity. †¢Mechanical properties are comparable to other polymers used (e. g. PP). †¢PHB has a fast degradation rate compared to other plastics. (months in sewage and years in sea water) yet ultra violet light can speed up this process. †¢The main advantage in the medical field is that PHB is a biodegradable plastic which can be inserted into the human body and does not have to be removed again. †¢Can be manipulated genically therefore can be used for many things Disadvantages of PHB: †¢It has a tendency to be brittle. Costs four times as much as polyethylene (it’s major competitor) †¢Cheaper to produce necessary materials from petrochemical industry. †¢Large scale production in early stages. †¢Uses sugarcane which can decrease biodiversity such as in Brazil. Evaluative Conclu sion: PHB has huge potetial as polymer for future,this is due to its main advantages such as being biodegradable and it has an ease of manipulation. This is good although work must be done to make it cheaper. Also work must be done to reduce the very large scale production in the early stages of production.There needs to be a way to make this plastic from cellulose in plant cell walls rather than from sugarcane alone. As the petrochemical industry supplies become scarce the price of PHB will go down, which is good for future use. Links Used: http://sundoc. bibliothek. uni-halle. de/diss-online/02/02H017/t2. pdf http://en. wikipedia. org/wiki/Poly-3-hydroxybutyrate http://en. wikipedia. org/wiki/Biopolymer http://www. gotessays. com/essays/543/index. php http://umpir. ump. edu. my/696/1/Aimi_Salma_Awalludin. pdf

South AFrican anthem essays

South AFrican anthem essays Choose one song that for you that epitomizes South African Music. Nkosi sikelela, thina lusapho lwayo. O se boloke, O se boloke setjhaba sa heso, Setjhaba sa South Afrika - South Afrika. Nkosi Sikelel' iAfrika was composed in 1897 by Enoch Mankayi Sontonga , a teacher at a Methodist mission school in Johannesburg. It was one of many songs he composed, and he was apparently a keen singer who composed the songs for his pupils. The words of the first stanza were originally written in Xhosa as a hymn. In 1927 Samuel Mqhayi, a poet, later added seven additional Xhosa stanzas. Most of Sontonga 's songs were sad, witnessing the suffering of African people in Johannesburg, but they were popular and after his death in 1905 choirs used to borrow them from his wife. Solomon Plaatje, one of South Africa's greatest writers and a founding member of the ANC, was the first to have the song recorded. This was in London in 1923. A Sesotho version was published in 1942 by Moses Mphahlele.The Rev J L Dube's Ohlange Zulu Choir popularised Nkosi Sikelel' iAfrika at concerts in Johannesburg, and it became a popular church hymn that was also adopted as the anthem at political meetings. For decades it was regarded as the national anthem of South Afrika by the oppressed and it was always sung as an act of defiance against the apartheid regime. A proclamation issued by the State President on 20 April 1994 stipulated that both Nkosi Sikelel' iAfrika and Die Stem, The Call of South Africa, would be the national anthems of South Africa. In 1996 a shortened, combined version of the two anthems was released as the new National Anthem, Official Version.There are no standard versions or translations of Nkosi Sikelel' iAfrika so the words vary from place to place and from occasion to occasion. Generally the f ...