Ass 5 - CPCCBC4011B ed 3 Apply structural principles to commercial low rise constructions PDF

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CPCCBC4011B ed 3 Apply structural principles to commercial low rise constructions...

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CPCCBC4011B: Assessment 5 Apply structural principles to commercial lowrise constructions

ALAN TAKACH TAFE ID No.: 375810077

17 January 2019

Table of Contents 1.

Introduction .................................................................................................................. 3

2.

Building Classification ................................................................................................ 3

3.

Footing system ............................................................................................................ 4 3.1

Soil type/ foundation typical of the area................................................................... 4

3.2

Footing system designed for this project ................................................................. 5

4.

Structural system......................................................................................................... 6 4.1

Slab-on-Ground including External Edge Beams .................................................... 6

4.2

Pad Footings........................................................................................................... 6

4.3

Columns ................................................................................................................. 8

4.4

Floor system ......................................................................................................... 10

5.

Floor System .............................................................................................................. 11

6.

Wall system ................................................................................................................ 13

7.

Services ...................................................................................................................... 15 7.1

Stormwater ........................................................................................................... 15

7.2

Power ................................................................................................................... 17

7.3

Water .................................................................................................................... 18

7.4

Gas ....................................................................................................................... 18

7.5

Fire Communications ............................................................................................ 18

7.6

Active Fire Protection ............................................................................................ 18

7.7

Passive Fire Protection ......................................................................................... 20

8.

Roof System ............................................................................................................... 21

9.

Conclusion ................................................................................................................. 22

10.

References .............................................................................................................. 22

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1.Introduction The purpose of this report is to analyse the design and construction of a reinforced concrete building. It will examine various aspects of the selected building including; its footing system, structural system, floor system, wall system, roof system, and its building services. The building selected as part of this project is an existing two-storey car park located in the suburb of Parramatta, NSW. Discussions included within this report will be supplemented with the use of photographs taken on-site, as well as hand drawn sketches for further clarification where required.

2.Building Classification The two-storey reinforced concrete car park selected for this project is located on George Street in the City of Parramatta and is currently used as a private parking space by local business. The building is classified as a Class 7a building as set out in the Building Code of Australia. The building falls under the category of “Type C” construction due to the rise in storeys not exceeding two.

Figure 1 Front Elevation of the two-storey car park

Figure 2 Side Elevation of the two-storey car park

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3.Footing system 3.1 Soil type/ foundation typical of the area To determine the soil type/foundation typical to the Parramatta area, a desktop study was undertaken based on published geological data from the Department of Resources and Energy. Specifically, reference was made to the Sydney 1: 100,000 Geological Map (Code 9130). A review of the above-mentioned geological map indicates that the soil typically comprises of black to dark-grey shale and laminite. Based on this description, we can assume that the depth of the clay profile at the subject site is less than 0.6 metres. Therefore, in accordance with Table D2 of AS 2870-2011, the soil in The Project area can be classified as Class S soil. Soils that fall under this classification are considered slightly reactive clay sites and may experience slight ground movement from moisture changes.

It should be noted, however, that the table above shall only be used as an aid, and that further geotechnical investigation/ borehole testing is required to confirm the soil classification.

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3.2 Footing system designed for this project The footing system utilised within this project consists of both pad footings and a slab-onground which includes external edge beams. The drawing below provides a typical section detail of the building’s structural framework including its footing, vertical columns, and suspended floor.

Figure 3 Structural Schematic

As shown in the structural schematic, the pad footings are “isolated” from the slab-on-ground as there is no structural connection between them. Steel reinforcement is installed within both the pad footings and slab- on-ground to provide tensile strength to the concrete. Details of the steel reinforcement, including bar diameters and spacing’s are specified in detail by the structural engineer within the design of the twostorey car park.

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4.Structural system The structural framework incorporated within the design and construction of the reinforced concrete car park will now be discussed, along with role of each structural member and its connection detail.

4.1 Slab-on-Ground including External Edge Beams External edge beams are installed around the perimeter of the slab- on-ground to comply with AS 2870. The edge beams include steel reinforcement which is tied into the slab- onground with the use of “Z” bars prior to the placement of concrete. The slab-on-ground is approximately 100mm thick and reinforced with top steel for shrinkage/temperature control, and bottom steel for tensile strength.

Figure 4 Edge Beam

4.2 Pad Footings Pad footings are incorporated within the design of the two-storey car park to support the point loads applied to them by the columns. Loads from the suspended slab are transferred to the pad footings, and ultimately the ground, via vertical columns positioned within the ground floor of the building. A separate pad footing is installed directly beneath each column so that the building’s loads are adequately supported. Each pad footing is approximately 500mm x 1000mm and founded on rock with an allowable bearing pressure which satisfies the structural engineer’s Page 6 of 22

specifications. The pad footings are isolated from the slab-on-ground, meaning that there is no structural connection between them. The Figure below shows a photograph of a pad footing prior to placement of concrete. Steel reinforcement is fixed into position at the base of the pad footing, and starter bars extend vertically to provide a structural connection between the pad footing and column.

Figure 5 Pad Footing prior to placement of concrete

The Figure below provides a typical pad footing design detail. There are close similarities within both images and we can assume that the builder has followed the structural design drawings with precision. Nonetheless, the structural engineer is required to provide sign-off on the work prior to concrete placement, and this will be undertaken via a hold point inspection.

Figure 6 Typical Pad Footing Detail

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4.3 Columns Concrete columns are incorporated within the design of the two-storey car park to carry the compressive loads imposed upon them by suspended concrete floor. The columns are built as off-form concrete, meaning that they are formed and cast in-situ. The finish requires formwork of a high quality, as well as a high level of workmanship, and proper concrete mix design.

Figure 7 Concrete Column

Reinforced concrete slabs are subject to various modes of failure. One mode of failure is known as “Punching Shear”. Punching shear is a type of failure of reinforced concrete slabs subjected to high localized forces. In flat slab structures, this occurs at column support points. The failure is due to shear. This type of failure is critical because no visible signs are shown prior to failure. To mitigate this risk, the two-storey car park was designed & constructed to include ‘drop panels’ at each column location. The drop panels are simply a projection below the slab which reduces the amount of negative reinforcement required over a column and increases the shear strength at that location. This will prevent columns from punching through the slab which is what can be seen when punching shear failures occur.

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Figure 8 Drop Panel at each column location

The Figure below provides a typical Column-Slab Termination detail. As shown, the steel reinforcement provides a structural connection between the column and suspended slab.

Figure 9 Column-Slab Termination Detail

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Figure 10 below shows the forces acting on the two-storey car park. As shown, there is a combination of both vertical and horizontal forces. The forces acting upon the building are countered by reaction forces in the pad footings. For example, Dead loads & live loads acting in the downwards direction are countered by an equal and opposite force from the building’s pad footings. Newtown’s third law of motion states that “for every action, there is an equal and opposite reaction”. This is clearly evident in the two-storey carpark, as the building is observed to be in static equilibrium and we can deduce that these reaction forces contribute to the overall stability of the structure.

Figure 10 Forces acting on structure

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5.Floor System The floor system installed within the two-storey carpark is a conventional concrete slab. This provides a durable surface for the vehicles to travel on and satisfies the design intent of the building. As with all concrete structures, formwork and reinforcement fixing are completed prior to a hold-point inspection. A structural engineer then reviews the work on-site and provides approval and/or recommendations prior to proceeding with the placement of concrete. Once engineer’s approval is obtained, the site supervisor places an order for concrete and organises a concrete pump to be available on the day of the pour. In relation to the two-storey car park, it would appear that the slab-on-ground and suspended slab are approximately 100mm thick, and we can assume that top and bottom reinforcement mesh was installed in accordance with the structural engineer’s specifications. In relation to the concrete finish, both slabs are sealed with a Clear Acrylic concrete sealer which extends the service life of the car park. In addition to this, line marking is applied to the concrete surface to delineate the car parking spaces.

Figure 11 Concrete Slab Floor System

During my site inspection, it was observed that the entry ramp had a rougher texture than the general car park area. The surface appeared to have been textured with a cove trowel finish. After some research, I found that the cove trowel finish increases the slip resistance Page 11 of 22

rating of the concrete, and provides a safe surface for vehicles to transverse particularly in wet weather. An image of the Entry/ Exit ramp is shown in Figure 12.

Figure 12 Cove trowel finish applied to Entry/ Exit ramp

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6.Wall system There is a small section within the car park where off-form concrete and blockwork walls have been installed. The purpose of these non-load bearing walls is to minimise the visual impact of the car park when viewed from the street, and provide security to a storage room and fire stair compartment within the building. The following section will describe in detail the various wall systems observed within the two-storey car park. Blockwork was observed predominantly on the southern side of the building adjacent to the street. It was clear from my site inspection that the blockwork was installed at this location to minimise the visual impact of the car park. The most likely reason for this is that it would have been a condition of the development consent issued by Parramatta City Council. As shown in Figure 13, 190mm wide blocks were laid directly on top of a 200mm wide concrete upstand. The blocks, which run up to the underside of the suspended slab are nonloadbearing and therefore, there is no requirement to reinforce or core-fill the blockwork.

Figure 13 Block wall (right)

In addition to block walls, the building appears to have feature wall panels which extend from Ground Floor to approximately three metres above the suspended slab. These are visible from the street, and help minimise the visual impact of the car park. The concrete feature walls are formed up using plywood formwork. Horizontal and vertical steel reinforcement is then fixed into position as per the structural specifications, ready for placement of concrete. A concrete pump is then used to pump the concrete from the street to the inside the walls. Page 13 of 22

The concrete mix used for walls is generally high slump (up to 150 mm) with a maximum 10mm aggregate. This allows the concrete to compact well into the formwork, and minimises air gaps and other defects associated with poor concrete compaction.

Figure 14 Reinforced Concrete Feature Wall Panels

There is also a combination of concrete upstands and galvanised handrails which have been installed around the perimeter of the two-storey car park. These provide vehicles with a physical barrier to minimise the risk of driving beyond the limits of the car park. Images of the concrete upstand and galvanised handrail are shown below.

Figure 15 Concrete Upstand

Figure 16 Galvanised Handrail

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7.Services 7.1 Stormwater Both levels of the two-storey car park have been fitted with drainage grates to capture stormwater runoff within the building. The drainage grates are generally situated in the centre of the slab at approximately 10 metres spacings. Stormwater is directed to the drainage grates with the assistance of a slight gradient of approximately 1% in the car park floor finish. Figure 18 below shows a typical photo of a drainage grate that has been cast into the concrete floor finish. As shown in blue arrows, stormwater is directed into the floor waste via a fall in the floor finish. Figure 18 shows a close-up photograph of a typical drainage grate spread evenly within the two-storey car park.

Figure 17 Fall in floor finish

Figure 18 Round drain grate

Stormwater that enters the drainage system is directed into a kerb inlet pit located at the street adjacent to the property. Figure 19 and Figure 20 show marked-up images of the stormwater flow through the Suspended Slab and Slab-on-ground respectively.

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DRAINAGE OF FIRST FLOOR SUSPENDED SLAB Figure 19 Stormwater drainage diagram from First Floor Suspended Slab

DRAINAGE OF SLAB-ON-GROUND Figure 20 Stormwater drainage diagram from Slab-on-Ground

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7.2 Power The two-storey car park is connected to the power distribution network via an underground electrical cable. The electrical cable is terminated at a switchboard which is securely located within a ground floor maintenance room in the carpark. The electrical meter, which measures the car park’s energy consumption, is also located within this room. Access into the room is via an Abloy key. The Figure below shows a typical electrical sub-board. This photo was taken from another site, but we can assume a similar sub-board and electricity meter is installed within the car park.

Figure 21 Typical photo of Electrical sub-board

Power consumption within the building is generally used for LED lighting installed throughout the lower level car park. Figure 22 shows LED lights installed on the soffit of the ground floor car park.

Figure 22 LED Lighting installed on the soffit of the ground floor car park

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7.3 Water The two-storey car park is connected to the Sydney Water network via an underground water main connection. Water supply within the two-storey car park is primary used to supply fire-fighting equipment with water. Such equipment include fire hydrants, fire hose reels, and a hydrant booster situated at the front the building. A few hose taps were also observed within the two-storey car park. It is assumed that these water supply points are installed within the building for car washing and regular maintenance/ cleaning of the concrete slabs.

7.4 Gas After a thorough review of the two-storey car park, it was determined that the building was not connected to Jemena’s gas supply network. This is most likely because the car park is simply used as secure area for vehicle parking. There is no requirement for gas heating or cooking appliances at this location, as such, a gas connection is not required.

7.5 Fire Communications After a thorough review of the two-storey car park, it was determined that the building is not serviced by any means of fire alarm or smoke detection system.

7.6 Active Fire Protection The images below show two means of active fire protection equipment located within the two-storey car park. Figure 23 shows a fire hydrant and hose reel fixed to an off-form concrete wall. The hose reel/ fire hydrant was observed to be installed on the ground floor adjacent to a fire stair case.

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Figure 23 A fire hydrant and hose reel

Figure 24 shows a fire hydrant booster installed at the main entrance to the building. The hydrant booster appears to be in an easily accessible location and can provide the fire brigade with additional water pressure in the event of a fire.

Figure 24 A fire hydrant booster facing the street

As part of this report, the National Construction Code was reviewed to determine if sprinklers were required to be installed within the two-storey carpark. It was determined that the Class 7a building fell under the category of an “open-deck carpark”, and as such, a sprinkler system was not required.

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7.7 Passive Fire Protection As per the table below, there is no requirement for any of the two-storey car park’s building el...