CPCCBC5018A: ASSESSMENT 82 Footings Detailed on the Plans for Project 3 Building structures are connected to the ground by use of foundations which basically transfers the loads from the building into the ground. There are different types of foundations including the shallow and the deep foundations. Deep foundations are normally constructed at a higher depths and transfers the loads deep into the soil while the shallow foundations are situated near the surface to transfer the loads at relatively shallow depths of the soil. Shallow foundations are sometimes referred to as footings and are categorized into strip, pad, cantilever or mat footings (Anderson, 2018). According to design plans provided for the construction of the Factory Complex, the pad and strip footings are to be used in the foundations during this project. The Type of Footing Detailed on the Plans The construction of the factory complex requires the use of shallow foundations and therefore various types of footings have been designed for use during constructions (Kim, 2017). According to the provided plans, two types of footings are provided namely the strip and pad footings. According to Halder (2019), strip footing is a type of footing which is used in the load bearing walls and when the construction involves a series of columns in a row which are very close to each other. The columns being closely spaced and it is therefore economical that a strip or continuous footing is provided covering all the columns in the row (Viana da Fonseca, Buttling, & Coutinho, 2014). In the plan strip footings are provided along the wall and the columns joining all the units, rooms and the offices in the complex. However, it is important to note that footing is stiffened with reinforcements and piers of 450 mm diameters are provided in to the soil strata to provide extra supports bellow the foundation (Far & Flint, 2017) .This due to
CPCCBC5018A: ASSESSMENT 83 weak soils under which the building is to be constructed. Section 3 of the Australian Standards, AS 2870 (2011) provides the various requirements for the design of strip footings for residential buildings and factory complexes. According to Killeen (2014), pad footings are usually used in the cases where columns are largely spaced. Pad footings have been provided in the plans for the construction of the foundation for the factory complex. Looking at the plans, only a few pad footings are to be provided especially in the columns that are largely spaced along the loading areas thus not connected with walls. Rectangular pads are used measuring 600mm x 1200 mm are utilised with reinforcements bars of Y16 sizes provided at both the top and the bottom. Also, a bar spacing of 200 mm need to be provided during the construction of the footing. The plan also provides for the inclusion of circular piers in the natural clay strata with piers having a 750 mm diameter such that the soil bearing strength restricted to a minimum of 250 kPa. The Australian Standards, AS2870 (2011) provides the requirements for the design of the pad footing under different load conditions. Footings Construction Method and Sequence The requirements for the construction of a strip footings are provided in the sections 6.5 of the Australian Standards AS2870 with size of the footings depending of the loads and the type of soil under which the structure is to be constructed (Sivakugan, Ameratunga, & Das, 2018). Some of the conditions that are critical for the construction of both pad and strip footings are that the foundation should provide 100 kPa of the allowable bearing pressure, the topsoil that contain grass roots should be completely removed and the excavated trenches should be cleaned and any water removed before concreted is placed (AS 2870, 2011).
CPCCBC5018A: ASSESSMENT 84 The general sequence of the construction of the footing involves the excavation of trenches into the ground around the structure perimeter, depending on the required depth of the footing typically below the frost line of the soil. This step is followed by the pouring of a thin concrete of appropriate mix design and thickness at the trench bottom. The concrete is then allowed for a period of time, typically a day to harden. This provides a flat and clean platform for the laying of the steel reinforcements and wire mesh for the footings. The stage next involves the establishment of the footing strip plate through the pouring of concrete in the laid mesh along the perimeter of the building foundation and allowed to harden. The reinforcements and formworks are established after the hardening of the footing plate based on the steel bar details provided in the plan after which the final concrete is poured and allowed to harden through the curing period. According to the specifications, inspections on the reinforcements must be carried out by the engineer prior to the pouring of the concrete. Generally, some of the typical components of the footing after the establishment of the reinforced concrete pad and strip socket include the 150 mm minimum hard-core, the 150mm concrete subfloor, a dump proof course, the 100 mm rigid insulation, a 75 mm concrete screed and a finished foot path or driveway path(Strip Foundation, 2018). Description of the Type of Plant and Equipment Necessary for Footings Construction A number of plants and equipment are required in the construction of footings including the ones needed for trenching, concrete pouring, formworks, reinforcements and the compactions. Such equipment include excavators, ready mixt concrete plant, plate compactors, concrete pump, water pumps and bowers ,mechanical activated vibrators ,bar bending machines
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CPCCBC5018A: ASSESSMENT 85 and dump trucks measuring equipment. Smaller tools such as harmers and pairs of pliers are also required for the wood formwork installation and linking of steel reinforcements (Priya, 2017). Excavators are needed for the footing excavations in the establishment of trenches for accommodating the footings based on the drawings. Concrete mixer plants is used in the mixing of concrete required in large quantities, concrete pumps convey the mixed concrete to the dug trenches while the water pumps and bowers provided the require water for mixing concrete. Also, the mechanical activated vibrators are used in the compaction of the poured concrete for the minimisation of voids or pores. The bar bending tools are necessary for measuring, cutting and bending of the reinforcement steel for the footings. Vibrating Plate compactor is necessary during the construction of the footing for the compaction of areas around the finished footing foundations. This compacting equipment can reach such confined points which cannot be accessed by larger vibrating rollers during constructions.The dump trucks transport he needed materials and equipment to the construction site and the excavated soil to the dumping sites. It is however worth noting that there are other smaller tools that the builders should equip themselves with including levelling tools. Method for the Placement of Steel ColumnsforPrecise Placement and Verticality The various methods for placing steel columns accurately and vertically are provided by the Australian Standards AS4100.According to Higgs (2015), the Structural, Mechanical and Engineering surveyors are tasked with ensuring the precise vertical positions of steel structures such as the steel columns. The methods used by the surveyors in determination of verticality
CPCCBC5018A: ASSESSMENT 86 depends on various factors including the site conditions, the available equipment and the time constraints. The methods for the determination of correct placement and verticality during the placement of the steel columns includes both traditional and modern technologies including positioning, plumbing and the remote methodologies. The accuracy of the methods are determined based on the section 15.3.2 of the AS 4100 , which states that the deviation of a steel column base from its value should not exceed 6 mm along the principal axes with reference to its position plan. Also, the deviation of any of the points above the compression member that is the column should not be more than height/500 (AS 4100, 1998). Looking at the positioning, the engineers need to ensure that the anchor bolts are correctly positioned during the placement of the steel column. However, only correct positioning of bolts may not guarantee accuracy due to construction variations .Therefore, other calculations of the column positions are necessary such as mearing the width and the breath of the column then marking the centre points. The positions of the marked points are then calculated relative to the positions provided in the design. For instance having a column A, when the measures are made in the X and Y exes it is found that the column deviates from its design positions to be 4mm and 2 mm in the Y and X axes respectively. According to AS 4100 the measurements are within +/- 6mm therefore the column correctly placed (Higgs, 2015).
CPCCBC5018A: ASSESSMENT 87 Figure 1: Column Positioning The verticality of the column should now be ensured after correct positioning and some of the methods of ensuring verticality is the use of plumb bob, the total station, the spirit levels and the mote methods. The plum bob and spirit methods involves the placement of the spirit levels directly on the column and checking its verticality as shown in figure 2. Figure 2: Column Verticality by Plumbing and Spirit Level
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CPCCBC5018A: ASSESSMENT 88 The remote methodology is important in cases where high accuracies are needed and the access difficulties. This method involves the use of digital machines and software which utilize the total station techniques where the machine is strategically positioned to pick chainages or points which are interpreted and drawn using the Computer-Aided Drafting software. Figure 3: Remote Methodology Suitable Method for the Temporary Support of the Concrete Wall Panels (For Project 3) The process of erection and connection of concrete wall panels calls for proper planning to ensure that everything is provided for during the process. The items that need to be adequately planned for include the methods of assembly and erection of the panels, the method of temporary support provision, final structural connections provision, the erection tolerance based on codes and the handling requirements such as adequate cranes (BCA-Australia,2015).
CPCCBC5018A: ASSESSMENT 89 The provision of temporary support during wall panel installation is very important before the stabilization of the wall when it is connected to the footings. Bracing or propping has been identified as the best method for the offering temporary supports to wall panels during their erection. Through this method, braces are provided in the panels which are allowed to remain in the panels throughout the period of erection and connection to the footings (Artemeva, 2018). The requirements for bracing of the concrete wall panels are provided by the Australian Standards AS 3850 -2003.The provided details should be considered including the loads required by the footings. The stabilization of a wall panel usually require two braces as the minimum number and it is efficient that they are fixed into the wall panels prior to the lifting for erection. The setting out of braces into a wall panel involve a number of steps, the first step being the location of the first brace at approximately 1/5 of the panel width from each sides. The second step is the establishment of the bracing inserts located at 2/3 of the height of the wall panels from the base. Finally, the braces are set such that they form about 60owith the footing in which the wall panel is to be connected.
CPCCBC5018A: ASSESSMENT 810 Figure 4: Brace Setting out During the erection of the panels, the braces should be adequately adjusted to ensure that there is no hanging of the braces beyond the panel level. Also, the braces should only be removed after ensuring that the connected wall panels are stable and free from falling(Design Guidelines for Wall Panel Connections, 2019).It is important for the engineers to calculate the forces acting on a given panel especially wind loads which vary from different sites of constructions. The forces include the wind pressure, tension and shear on the footing anchors and the overall force on the panel (Tilt-Up Concrete Association, 1998).
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CPCCBC5018A: ASSESSMENT 811 Considering the wind load W and a concrete wall panel of height, H Shear, v = W x (panel width/no. of braces) x 0.67H Ultimate shear, Vult = v x 1.5 Tension, T = v tan A Ultimate tension = Tult = T x 1.5 F= v/cos A = W x (panel width/no. of braces) x 0.67H/cos A Where A is the base angle usually 60o Wind loads design factors are normally obtained from Australian standard codes AS 1170 part 2 including the terrain, housing density and the panel size coefficients in the design of the braces.
CPCCBC5018A: ASSESSMENT 812 The Need for Termite Protection for the Building in Project 2 (Medium Rise Apartments) Termites have been identified as a major causes of damages to buildings and homes and therefore new buildings must be protected from them. The methods of protecting buildings against termites include the use of barriers such as granular and sheet materials and use of chemicals (Victorian Building Authority, 2019). The Building Codes of Australia provides for various elements of a building and the corresponding termite management systems. According to the code, building elements such as the ground concrete slab, the suspended floors and the various attachments to the building should be provided with a termite management system. Also, the Australian Standards AS 3660.1 outlines the requirements for various termite management systems. The slab perimeter of the ground floor ,various penetrations or joints and the areas below the slab the of the medium rise apartments need termite protection by use of components such as use of sheet an granular material or chemicals during the construction of the ground slab. The footing systems of the building should also be protected (BCA-2015).
CPCCBC5018A: ASSESSMENT 813 References Anderson, B. (2018). Concrete Footing - Guidelines for Building Concrete Footings. (2009, December 3). Retrieved from https://www.concretenetwork.com/concrete/footing_fundamentals/ Artemeva, M. (2018). Connections of wall precast concrete elements. AS-NZS 1170-2. (2011). Australia-New Zealand Standard Structural Design Actions Part-2: Wind Australia Standards (2014). AS 3660.1:2014 -Termite Management -New building work Australia Standards, (2003). AS 3850-2003 | Tilt-up concrete construction Australian Standard, A. S. (2011). 2870-2011.Residential Slabs and Footings, 12. BCA. (2015). Part3.1.3 -Termite Management Systems and Components BCA. (2018). Installation of Concrete Wall Panel. Retrieved from https://www.ccaa.com.au/imis_prod/documents/Library%20Documents/CCAA %20Technical%20Publications/CCAA%20Guides/CCAAGUIDE2001-T54-CPH10-12- TBR.pdf Charlie Higgs. (2015). The Position and Verticality of Structural Steel.Proceedings of the 20th Association of Public Authority Surveyors Conference (APAS2015) Coffs Harbour, New South Wales, Australia, 16-18 March 2015. Design Guidelines for Wall Panel Connections. (2019). Retrieved from https://ec.europa.eu/jrc/en/publication/design-guidelines-wall-panel-connections Far,H., & Flint,D. (2017). Significance of using isolated footing technique for residential construction on expansive soils.Frontiers of Structural and Civil Engineering,11(1), 123-129. doi:10.1007/s11709-016-0372-8
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CPCCBC5018A: ASSESSMENT 814 Halder, K., Chakraborty, D., & Kumar Dash, S. (2019). Bearing capacity of a strip footing situated on soil slope using a non-associated flow rule in lower bound limit analysis. International Journal of Geotechnical Engineering,13(2), 103-111. Killeen, M. M., & McCabe, B. A. (2014). Settlement performance of pad footings on soft clay supported by stone columns: a numerical study.Soils and Foundations,54(4), 760-776. Kim, Y., Park, H., & Jeong, S. (2017). Settlement behavior of shallow foundations in unsaturated soils under rainfall.Sustainability,9(8), 1417. Limited,S.A. (2014).Residential Slabs and Footings: Construction: (incorporating Amendments Nos 1, 2, 3 and 4). Priya, R. (2017). FOOTING CONSTRUCTION. (2017, November 11). Retrieved from https://www.slideshare.net/MdShadab25/footing-construction Sivakugan,N., Ameratunga,J., & Das,B.M. (2018). Site characterisation for residential slabs and footings – Australian practice.International Journal of Geotechnical Engineering, 1-4. doi:10.1080/19386362.2018.1432523 Standards of Australia. (1998). AS 4100-1998 - Steel Structures. Strip Foundation. (2018). Retrieved from http://constructionstudiesq1.weebly.com/strip- foundation.html Tilt-Up Concrete Association. (1998).Tilt-up Concrete Association's Guideline for Temporary Wind Bracing of Tilt-up Concrete Panels During Construction. Viana da Fonseca,A., Buttling,S., & Coutinho,R. (2014). Foundations: Shallow and deep foundations, unsaturated conditions, heave and collapse, monitoring and proof testing. Handbook of Tropical Residual Soils Engineering, 283-412. doi: 10.1201/b12302-8
CPCCBC5018A: ASSESSMENT 815 Victorian Building Authority (2019). Termites. (2019, September 16). Retrieved from https://www.vba.vic.gov.au/consumers/safety-guides/termites