Painting and sculpture gallery - Essay Example

PAINTING AND SCULPTURE GALLERY Painting and Sculpture Gallery Building and construction industry requires accurate evaluation and analysis of materials, geographical aspects, climatic conditions, physical properties of materials, the structural aspect of the materials, the effects of heat, behavior udder load, the soil type and cost of materials. These properties help the structural engineer come up the most viable structural design to support the building. The critical evaluation of the structural loading imposed on all the structural elements of the building is important in erecting a building that is firm and stable. This evaluation involves determining the tensile and compressive forces acting on the structural members. A proper material selection contributes to the general stability of the building. Most architectural work is creative and differs greatly in terms of shape and size. The structural engineer has to develop the most suitable support system for the architect design. Lack of proper structural support lead to the collapse of building which may result to loss of lives and huge financial loses. For proper stability of the building, all structural elements must be subject to forces that will not result to them yielding. Tension, which is the degree of material deformation due to the material being subjected to a pulling force results changes in shape of the ties that are used during the construction of trusses, the tension should be accurately calculated to ensure that the deformation on the structural members does not exceed the yield point. According to hooks law, which states that the deformation of a material is directly proportional to the applied tensile force, when a material is subjected to a tensile force it becomes elongated. This elongation is coupled by a slight reduction in the cross sectional area of the structural member These effects of the tensile force on this structural member will depend on the elasticity of the tie. Elasticity can be defined as the ability of a structural member such as the tie to return to its original shape after the application of a tensile, compressive or a twisting force. When beams, struts and ties are subjected to tensile and compressive forces, they are deformed. The extent of the material elasticity greatly determines its stability under such a load. Continuous increase in the load applied to a structural element lead to an increased deformation. There is a limit reached where the material loses it elastic nature. This limit is refereed to as the elastic limit. Further stretching of the structural member beyond this limit results to permanent deformation of the material. Beyond the point of elasticity, hooks law ceases to apply, the material behaves in a plastic manner, plastic material do not return to their original shape after the load has been removed. At yield point the material may collapse. It is upon the structural engineer to perform comprehensive calculation of the loads applied to a building and come up with a suitable structure to resist the calculated load. There are two types of loads. There is the live and dead load. Structural elements are also subjected to compressive loads. This causes a decrease in the original size of these elements and a consequent increase in the cross-sectional area of the element. A compressive force in a building affects structural elements such as columns, struts and beams. Excessive compressive forces results to the buckling of these structural materials. The designer must calculate these compressive load and select materials that can withstand buckling. Creep is another structural effect that affects materials used in building and construction; udder creep the material is slowly and progressively deformed. This mainly occurs when structural members are subjected to high temperatures, continuous vibration from heavy machines and repeated cyclic stress. Creep leads to the gradual sagging of ties and beams and the loosening of bolts use to join the structural elements. The designer has therefore to take into account such unnoticeable changes that may lead to rapture of the material. Creep lead to material fracture. The progressive fracture of material leads to fatigue and finally the material fails. Structural materials must have an ability to resist changes due to the imposed loads. This ability is referred to as stiffness. Structural materials must also be selected carefully to ensures that the selected material don't have negative effects on the environment. The materials should also resist negative effects of the environment upon them. These include corrosion, rusting, chemical attack and effects of salty water and acidic soils. Structural materials must resist all these effects. In these design the beams used are coated at exposed points to reduce their contact to the environment. The materials selected for the design must also be able to resists fire; steel structures usually soften when heat is applied to them. It is necessary to design structures that resist the negative effects of heating. An example of this is the bombing of twin towers where the columns and beams yielded due to heat and finally the building collapsed. The use of steel alone subjects the material to weakness especially when fire erupts. To counter this effect there is need to use reinforced concrete that has very high thermal stability. This is necessary to allow the structure to withstand the effects of the fire. Another negative effect of heat and temperature is the expansion due to changes in temperatures, a positive change in temperature results to an equivalent increase in the size of the structural members while a decrease in temperature results to the shrinking of the material. For cantilever beams there is space for the materials to expand, but for simply supported beams. Where there is no space for expansion, the beam can be deformed. To prevent this space must be left to allow for this expansion and contraction. Another effect is the difference in expansion rate of two composite materials used together in construction, for example steel and concrete, given that these two materials have differing coefficient of expansion this may lead to slight defection of reinforced concrete resulting to cracking of the material (Heyman, 1999). Structural materials must be stable under different imposed loads, stability is the ability of a material to return to its original size and shape after the disturbing force has been withdrawn. Structural members such as ties and beams must be well balanced so that the compressive forces imposed on the struts cancels out with the tensile forces acing on the Ties. This equilibrium is critical in most of the building structures especially the roofing where the materials span for long distances without support. Critical analysis of the soil type in necessary to determine the maximum load that can be applied on these soils. The soil layers should be studied to a great extent to determine the different soil layers in the earth crust. The principle of super position states that the younger strata will always lie on top of the older strata in an un deformed sequence of strata. The principle simply indicates a clearly observable fact that the young sediments will always settle on top of the old sediments. It is important to sturdy this effect as it may affect the stability of a building in the long run. Different soils behave differently, loam soils are too weak to handle load imposed by the building, clay soils expand and become waterlogged when it rains and they shrink during the dry season, this lead to the cracking of building erected on this type of soil. Fill and peat are too weak and unstable and special foundation must be erected to ensure that the building does not crack or crumble. The computation of deformation, deflections and internal forces and stresses are important to allow the beams columns and other structural elements operate properly; the methods that can be used in this analysis are energy methods, flexibility method, direct stiffness method which encompass plastic analysis and finite element method (Charlton, 1973). In the energy principle method; the stresses, strains, displacement and deformations are expressed in terms of energy or work done by the external and internal forces. It is a convenient method of analyzing as energy is a scalar quantity. The principle of virtual work is applied. Virtual work results from virtual forces acting through real displacement or real forces resulting from virtual displacement. The forces applied maybe a force or a moment of a force whereas the displacement maybe linear or rotational. For particles to be in equilibrium. Where F = force, j represents the particle in equilibrium. By summation of each individual particles work and since the summation of virtual work must be zero, then From this expression, it can be seen that forces applied in a static system do no work; this is the principle of virtual work for a static system. For a system of rigid bodies, when a rigid system of body is subjected to compatible displacements the total virtual work for all the external forces is equal to zero, the body is in equilibrium (Reddy, 2002). Principle of virtual work for a deformed body For a deformable body, the principle of virtual work equation is Sum of external virtual work = Where represents a state where the body forces (f) and the external surface forces ( T )and internal stresses are in equilibrium Represent the continuous displacement of and the strains associated with these strains (Felippa, 2001). Materials For the design to be effective, the selection of materials to be used is important. The structural elements considered in this design are: Columns These structural elements are used for supporting beams and other structural elements such as the masonry. They are subjected to axial loads. Beams Beams are structural members subjected to pure bending. Some parts of the beam maybe in tension while other parts maybe in compression. Beams span across columns and are used in the roofing as well as in the steel framework support. There are different methods of supporting beams these include; Cantilever beams In this kind of support the beams are supported at one end Simply supported beams Beams are supported vertically at two points. Due to temperature effects one side of the beam may be allowed to move vertically to allow for thermal expansion. Struts and ties There are used to form a truss framework. Ties are subjected to tensile forces while struts are subjected to compressive forces. Angle sections are used to join the trusses forming the ties and struts. Truss units are used in excessively long spans where it would lead to sagging of beams or where the long spans necessitates the use of extremely large beam which are very expensive (Tauchert, 1974). Structural steel Steel is an alloy of carbon and iron. The addition of carbon to the pure iron improves the strength, hardness and toughness of iron bars. Different amount of carbon added to the iron results to differing properties of the steels. The heat treatment of steel also affects the properties of the steel. Slow cooling results to iron that is not hardened, whereas fast quenching results in hardened iron which is very brittle. The strength of steel is also affected by the shape of the steels. Different shapes of steel bars have different strength and resistance to tensile and compressive forces. The following types of structural steel are used in this design( Hosford, 2005). The universal beam (I) beam This is one of the strongest engineering beams, it is also referred to as the H section, it is used in the structural beams of this design and also as the column for the structural framework. Angle sections They have two shapes and assume an L shape. Trusses are formed using these sections T section Have a T shaped structure Railway profile They are similar to the universal beams but are asymmetrical, one of the faces is wider than the other, they include flanged T rail, grooved rail and the common railway rails. Bars They are rectangular in shape and relatively long. circular shaped bars are referred to as rods. Hollow sections The structures have hollow shape. The come in various shapes and sizes, they include rectangular hollow sections, square hollow sections, circular hollow sections and elliptical hollow sections. These sections are sometimes used as beams. Concrete This is a mixture of sand, cement and aggregate. The mixture is mixed with water and the hydration of cement result to a bond being created resulting to the bindings of sand and the aggregate. Reinforced concrete involves the use of steel bars to provide extra strength to the concrete, currently most building structures use reinforced concrete. Steel bars are first woven to form a metallic rebar; concrete is then poured to this rebar. Some of the most inherent property of reinforced concrete includes; Greater resistance to externally imposed stress as concrete firmly adheres itself to the steel bars upon solidification. This results to the transfer of the stress to the steel bars. Greater resistance to collision; upon solidification of concrete, an alkaline layer is formed round the steel bar preventing corrosion of the iron bars. The difference in expansion of the two elements that is steel and concrete may lead to cracking hence appropriate allowances are required. Glass This are used to allow light and ventilation to the house as well as to improve the aesthetic value of the house. Glass is made from silica and does not contribute to the support of the house. Aluminum Aluminum has great resistance to corrosion; it also has great strength and a good surface finish. It is used in formation of frames and other interior separations of building. it use is hampered by the fact that it is expensive. The design of different structural elements The two viable designs considered herein are The design of the structure using reinforced concrete Design of the structure using steel framework In both design, the wall are made of mansion and the roofing consists of sheets. Foundation After a detailed survey the soil type and layout is as given below 0.0m -0.3m topsoil 0.3-1.5 m sand 1.5m-onwards gravel The factors affecting the choice of the foundation include the soil type, the occurrence of ground water and the magnitude of the structural load imposed by the building. In this case no ground water was encountered hence it will not present unusual difficulties. The foundation, absence of clay, fill and peat makes this ground very stable. The foundation trenches will be dug 3 M as the storey houses has to be firmly fixed on the ground. The type of foundation is the spread footing foundation. This type of foundation has a concrete slab under every foundation column and a continuous slab under the wall that carries load. This is the most economical foundation. The figure below shows the structural details of this type of foundation. Fig 1 showing the spread foundation Along the wall, a concrete slab is also laid to support the walls which are also under load. The specific details of the speared footing are shown below Fig 2 showing the base of the spread footing foundation. The structure Two types of structures are considered herein (1) the use of reinforced concrete In this structure, the columns are assembled from reinforced concrete; the columns are spaced at distances equal to 3 meters. Since the structure has three different buildings each building requires a different support frame. The frame looking at section A-A is as shown in the figure below Fig 3 showing the reinforced concrete structure The wall structure shown above is the exterior wall of the gallery looking at section A-A, the columns are made of reinforced concrete. Between the columns stones or bricks are used to fill the columns. The encircled points indicates the points where beams running though the gallery, the shop and to the plant room are located. These beams are supported by struts and ties to form trusses which run along the building in the east west direction. The dimension of the whole structure is a shown in the diagram below. Fig 4showing the dimensions of the reinforced concrete structure The cross-section at the foyer shop is as shown in the diagram below. Fig 5 showing the structural members of the building along B-B Because the foyer shop does not have columns, beams running across the building from the exterior wall of the gallery to the interior wall of the plant room via the shop wall are used to support the roofing. The beams are vertically supported forming a frame work of simply supported beams which are supported at three points. Columns are located at the points but on the exterior walls. The plan view of this arrangement is a shown below Fig 6 showing the plan view and the arrangement of beams and trusses Due to the nature of the glass materials it is necessary to use stainless steel columns vertically erected at distances of 1 meter. The columns are supported by beams running horizontally and the glasses are bolted on these bars. Aluminum extrusions can also be used though they are expensive, they have they advantage of been light and very strong. The rear part resembles the front part. Stainless steel RSS are used as columns to support the glazing; beams are used to support the glazing horizontally. The beams are also made of aluminum or stainless steel. This is because the material corrodes less and therefore does not affect the glass particular at the bolted sections. Aluminum is preferred more than steel in that it is light, and has good structural properties. The sectional view along the C-C is as shown below Fig 7 showing the sectional view of along C-C The load of the floor is supported by the walls of exhibit floor, during construction a well reinforced concrete slabs is erected across the walls of the exhibit floor. Strong concrete is used together with a well meshed steel rebar to help support the floor. The roof for this section is supported by H section beams which are joined with ties and beams to aid in support. The walls are able to support the immense load of the floor due to the fact that there are columns providing vertical support. The roof The roofing consists of iron sheeting supported by a framework of trusses. The individual structural members of the roof are H section beams joined with struts and ties. This helps to prevent the beams from sagging. In general two types of trusses are used. There are four main trusses running along the wall of the building, these trusses slope along the walls and determine the slope of the roofing. The trusses are further subdivided into two, one layer covering the gallery, shop and the plant room, the other set of four trusses cover the gallery, foyer shop and the administration block. Fig 8 showing the roofing structural framing The metallic structure The above structure can also be made of a metallic frame work. The columns are made of steel H sections; these beams running transverse to the building are then used for the roof support. The metallic structure is also used for the roofing. The design resembles the concrete framework except that the instead of using reinforcing concrete columns steel columns are used. Discussion Comparing the two possible structural framework, reinforced concrete has more advantages as compared to the steel structural support framework. Reinforced concretes is much more cheaper as compared to the use of steel. When steel structures are exposed to air, water and chemicals rusting and corrosion occurs. Steel alone is not able to withstand high temperature. Reinforced Concrete structures have high thermal stability and do not crumble if exposed to fire for a long time. PART B The letter to the architect The expansion of the building to occupy the defined space has the following structural implications. The columns which vertically support the roof and the beams traversing across the house in the east west direction will have to be eliminated. To do this the existing roof has to be supported by a steel framework. The will offer temporary support as the existing wall is being replaced. There will be an extra cost in addition to the demolition in that extra money is required to purchase a steel framework to provide the support. The moving of the exterior wall 8 meters from it current location will also affect the stability of the building. The beams which were originally spanning 8 meters between two walls will have to span through 16 meters. This additional distance is far too long. Heavy beams must be used to prevent the roof from sagging. The structure of the roof can also be changed to be able to counter the increase in distance which increases the moment of the force applied especially at the center leading to sagging. The longer the beams span the greater the moment of force acting at the center of the beam. This moment is given by the product of the load and the perpendicular distance. For a simply supported beam this moment is greatest at the center of the beam. If reinforced concrete is to be used for the structural framework, then larger exterior pillars will be required. This will necessitate the use of larger steel bars for the rebar construction. This will lead to increased costs. If steel framework is used for the structural framing, heavier steel beams will be required for the column support as well as the for beams. Part C (A) The apex support bracket Two types of support bracket can be used The 16 sided bracket This type of bracket resembles the base of the structure. This ensures that all the sixteen beams can be joined each at its own side. The heavy beams are welded with a plate, which has bolt holes that coincide with those of the steel bracket. The beams are then joined together by fastening bolts. The figure below shows this arrangement. Fig 9 showing the bracket used to join the 16 beams Another form of joining the beams at the apex is described below Fig 10 showing the joining of the 16 beams at an apex Methods of constructing the construction The soil types are determined; this will help in the stetting of a strong foundation to support the building The foundation is excavated and hardcore is filled and compacted A steel rebar is then constructed Concrete is then added to the steel rebar and compacted. Steel beams are then erected and bolted on the concrete floor. A center post (temporary) is erected to help position the beams on the 16 square bracket The 16 beams are then bolted. One end of the beam is bolted to the column while the other part is bolted to the 16 sided steel brackets Lateral angle sections are then used to join the beams around the circumference; these are used for strengthening the conical structure, Suitable roofing materials are then fastened. References Charlton, T. (1973). Energy Principles in Theory of Structures. Oxford: Oxford University Press. Felippa, C. (2001). Introduction to Finite Element Method. [Online]. Available at: (Accessed 20 May 2009) Heyman, J. (1999). The Science of Structural Engineering. London: Imperial College Press Hosford, W. (2005). Mechanical Behavior of Materials. Cambridge: Cambridge University Press. Reddy, J. (2002). Energy Principles and Variational Methods in Applied Mechanics, NEW York: John Wiley. Tauchert, T. (1974). Energy Principles in Structural Mechanics. New York: McGraw-Hill. Read More