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INTRODUCTION
This report is about the assessment of a steel portal framed construction having a wide span which is already under construction or already completed. Some of the information of the building in question that will be considered in this assessment include footing system, structural system, floor system, wall system, services, and roof system. The building which will be used in the assessment is an already complete health facility located in Pretoria, South Africa. Figure 1 below shows an elevation of the health facility that is to be assessed in this report.
The health facility above is a five-storey building with a height of 85 feet above the ground. The construction of this facility cost approximately 10 million dollars with a provision of an occupant space of 78 000 square feet. The sections of the health facility which are assessed in this report include its footing system, structural system, floor system, wall system, services, and roof system (Ambrose, 2013).
Footing System
The footing system includes the structures that transfer the weight of the facility to the material of foundation which is mostly soil. The systems of footing should be designed to suit the variations of soil conditions and also offer enough tie-down for the health facility under the wind classification of the site. A good footing system attains these requirements while reducing the quantities of materials and site disturbance with huge embodies energy such as steel and concrete. For the adequate performance of the health facility, a firm foundation which includes installed footings of sufficient size which is involved in supporting the structure and preventing excessive settlement (Arya, 2014).
The foundations can be categorized as deep foundations or shallow foundations depending on the load-transfer member depth below the facility as well as the transfer load mechanism type. The system of foundation depends on the on the compressibility and strength of the soils around the facility, loading conditions proposed, and the performance criteria of the project. The designs of the foundation are based on the soil’s assumed bearing capacity at the site of the facility. The shallow type of foundation gives the most economical system of foundation and is used typically for commercial and residential buildings (Council, 2012).
During the construction of the health facility, the soil where the site was to be constructed has poor soil condition hence there was a need to use deep foundations for the provision of bearing capacity and limit settlement. The footing systems are normally covered in the code of the building and sized depending on the weight of the facility and the soil’s bearing capacity. The types of footing system that were used in the construction of the foundation of the health facility include grade beam footing, continuous spread footing and spot footings. These types of footings were used in the foundation as shown in figure 2 below:
The type of foundation that was used in the construction of the facility was the stem wall foundation which is also known as the continuous foundation walls. This type of foundation is constructed frequently of poured concrete or reinforced masonry, supported by footing that is continuously reinforced concrete as shown in figure 3 below.
Structural System
The structural system of the health facility entails the frame supports of the building’s loads as well as how the building resist wind loads. The type of frames implemented in the construction of the facility between the structural members such as column and rafter was portal frames. The portal frames are normally comprised of the horizontal and columns or even after that are pitched and joined through resisting connections of the moment. The resistance to the vertical and lateral actions is offered by the connection’s rigidity and the member’s bending stiffness which is improved by a deepening of the section of the rafter or suitable haunch (Ambrose, 2013).
The types of portal frames which can be implemented in any building depending on the specification of the building include cellular beam, curved rafter, mansard portal frame, propped portal frame, tied portal frame, and mono-pitched portal frame. Figure 4 below shows the cross-section of the portal frame as used in the health facility.
This type of structure of continuous frames is stable in its plane and gives a clear span which is bot unobstructed by the bracing. The portal frames were selected for the construction of the health facility due to its efficiency for enclosing huge volumes. The actions which will be controlled by the portal frames can be categorized as permanent actions or variable actions. The permanent actions involve the facility’s self-weight, cladding, and secondary steelwork. The variable actions include the accident actions, wind actions, snow actions, imposed roof loads, and fire. The wind actions affect the final design of the construction. The designer should make a careful choice between the use of simplification which eases the process of design, use of simplifications, and fully rigorous but make the loads more traditional (Arya, 2014).
Floor Systems
There are two categories of the system of floors which include suspended floors and those in contact with the ground. The choice of the system of flooring is dependent on numerous factors such as the economy, ease of erection, sound insulation needed, and thermal performance needed. The thickness of the floor framing for this case of health facility made of steel framing and concrete slab is as shown in figure 5 below.
The floors in contact with the ground surface involve reinforced slab on fill or the slab being dropped at the edge of the beams. This type of the floor system was used in the construction of the floor of the health facility. The suspended flooring system which is normally suspended concrete slabs were used in both upper floors and ground floor levels. The joints are interruptions on a continuous floor surface of the health facility. The design of the floor determines the design of the joint. The factors determining the floor design include environment, operations, owner specifications, site condition, and mix design (Council, 2012).
The major types of joints include expansion joints, isolation joints, contraction joints, and construction joints. The isolation joints are situated where the slab meets the surface that is vertical of the wall. The contraction joints are made by saw cutting at intervals amongst the joints of construction. The construction joints are the junction where a new pour meets an earlier placed pour. Figure 6 below shows the construction joints used on the floor of the facility (Council, 2012).
The floor finishes entails numerous materials that are utilized to cover the floor permanently. There are three major types of products used in floor finishes which include industrial-designed for warehouses, residential-designed for the family room, and commercial-designed for health facilities. The type of floor finishes used for this facility was ceramic tiles with the installation time of two days and durability of 10 to 15 years. The most appropriate floor finishes that should be used for this facility is PVC flooring due to its aesthetic value and can easily be scratched or dented if a heavy material is dragged on it (Ambrose, 2013).
Wall System
Majority of the walls being constructed are made up of the composite which is made of more than a single category of material. The walls of this health facility possess protective components and structured components which perform functions such as resistance to fire, insect attack, noise transfer, and thermal extremes. The solid wall system is made up of straw bale, AAC block, concrete brick, cavity brick, and solid brick. Some sections of the health facility were constructed using steel wall system especially the wall of the first floor until the fifth floor. The framings of the steel floor are used with the whole variety of unadventurous footings, concrete stumps, timber, piers, and dwarf walls (Arya, 2014).
The cavity systems were used in the construction of the ground floor. This system of cavity involves the construction of the wall using the motor as an agent of bonding. The dual walls, known as skins of leafs are held in position by cavity ties fixed into the joints between masonry’s courses which resist wind loads in tow perpendicular direction. The exterior leaf acts as a wall of weather while the cavity should inhibit any water that passes the external wall from reaching the interior (Arya, 2014).
The bricks are not resistant to the moisture and require to be protected from liquids to prevent dampness from getting into the dwelling. The procedures used in the prevention of moisture from getting into the dwelling through the wall is having a cavity amongst the two brickwork’s leaves to enable breaking of the contact and not permitting liquids from entering the inside face. To prevent rising damp from the foundation a course that is damp should be situated above the level of the ground but below the level of the floor (Council, 2012).
Services
The stormwater is collected by the use of gutter which is positioned from the rooftop and channelled to the ponding areas and retention or detention tanks. The water is then channelled to the water system from the retention tanks.
The capacity of the gutter is dependent on the quantity of stormwater in the region. The gutters are made from the rooftops to maximize water collected and prevent the damping of walls. The water collected by the gutter is collected through the downpipe from the edge of the roof to the construction’s base where it is collected (Ambrose, 2013).
The detention ponds specifically give control measures of the flood and can also be referred to as dry ponds. The detention ponds assist in controlling the flow rate by the use of the device control which maintains the rate of flow that is re-developed. The figure below shows the detention pond (Ambrose, 2013).
The retention ponds hold the pool water permanently and can also be referred to as a wet pond. The retention ponds are built in regions where the water table is high. The pond’s bottom is excavated beneath the elevation of the water table to create a permanent pool.
The power system of the facility is majorly composed of two generators which function simultaneously to provide sufficient and reliable power source within the health facility. The major reason for the use of generators and not the grid from the external power station is because of unpredictable nature of this source of electricity (Council, 2012).
Every turbine generator possesses its own auxiliary transformer that is involved in stepping down or stepping up of the voltages to be used in the facility. The water and gas pipeline system run parallel to each other in each and every room of the facility so as they can be used for numerous reasons (Arya, 2014).
The fire communication within the building is made possible by the use of fire alarm system which is connected to different sections of the building and all of them interconnected to a controller. In case of fire outbreak, the smoke and heat detectors detect the fire and send signals sounder circuit which warns the people on the building.
Roof System
Majority of buildings are made of roof structures of either steel or timber. For this health facility in a question, the roof system is made up of steel. Some of the types of roof system include a flat roof, gable roof, hip roof, and trussed roofs. The trussed roofs are currently prefabricated and are members of composite doing the work of huge simple members. The important components of the truss roofs include intermediate members which can be ties or struts, the bottom chord, and the top chord (Council, 2012).
The roofs may be enclosed by the conventional coverings of the roofs such as metal sheets and tiles and the choice of the type of cover depends on the trusses’ spacing. The components making up the roofing system include pitching point, web tie, top chord, roof batten, fascia, nail plates, ceiling, and roofing. The roofs of the truss are composed of numerous triangles nailed, bolted, and welded together to make a unit that is integral which spans across openings, support the combined weight of the roof covering and itself, and require to be specifically supported on perimeter walls and columns (Arya, 2014).
Roof cladding is normally used to provide the roof with a weatherproof layer and also to stop water from getting into the facility. The metal cladding is normally used; the types of metal cladding which can be used during roofing include mini orb, spandex, slake, and corrugated. The type of metal cladding that was used in roofing of the health facility was known as slate as shown in the figure below:
The gutter system that will be used in the collection of stormwater from the rooftop covers the entire roof system for maximum water harvesting and to prevent the damping of walls. The details of the gutter system are as shown in the figure below (Ambrose, 2013).
Conclusion
This report is about the assessment of a steel portal framed construction having a wide span which is already under construction or already completed. Some of the information of the building in question that has been considered in above assessment include footing system, structural system, floor system, wall system, services, and roof system. The building which has been used in this assessment is an already complete health facility located in Pretoria, South Africa.
Bibliography
Ambrose, J., 2013. Building construction: site and below-grade systems. Paris: Van Nostrand Reinhold.
Arya, C., 2014. Design of Structural Elements: Concrete, Steelwork, Masonry and Timber Designs to British Standards and Eurocodes, Second Edition. Colorado: CRC Press.
Council, R., 2012. Housing systems proposals for operation breakthrough. Michigan: U.S. Dept. of Housing and Urban Development.
