SCHOOL OF ARCHITECTURE, BUILDING AND DESIGNTHE ARCHITECTURE SCHOOL

BACHELOR OF QUANTITY SURVEYORING (HONOURS)

MODULE: CONSTRUCTION TECHNOLOGY 1 (BLD 60104)

LECTURER: Mr. LEONG BOON TIK

NAME: GOH JENG JHIEH

STUDENT ID: 0315080

EXISTING SLAB: FLAT SLAB

Flat slab is a reinforced concrete slab supported directly by concrete columns without the use of beams. It is made with reinforced concrete, in which rebar is intersected in the forms to provide support and reinforcement once the concrete is poured and hardened. The slab design is designed to be reinforced in several directions so that it can withstand stresses.

Pros:

- Flexible arrangements for services distribution as services do not have to divert around structural elements.

- More economic than other forms of construction- No restrictions on the positioning of horizontal services- Flexibility to the occupier who can easily alter internal layouts to

accommodate changes in the use of the structure- No beam to obstruct light and circulation of air- Less danger of concrete spalling and exposing reinforcement - No need skilled workers to build

Cons:

- Loads due to higher thickness of slab elements as required to control deflection

- Stiffness and weight consideration in earthquakes area- Excessive loads tend to try to punch through the slab

ALTERNATIVE WAY: TWO WAY SLAB

Two way slabs are the slabs that are supported on four sides and the ratio of longer span to shorter span is less than 2. In two way slabs, load will be carried in both the directions. So, main reinforcement is provided in both directions for two way slabs.

Pros:

- Forces are transferred to beams and it is more rigid- Small thickness of floor, save cost- Distribute forces equally to beams and then columns, lower rate of

punching shear than flat slab- Minimize deflection

Cons:

- Floor height is lost because need more height for installation of different piping

- Shear is critical in beam, which is hard to fix- Space of each area is limited due to installation of beam- More cost on formworks and beams- Higher labor cost

JUSTIFICATION:

Flat slab will be better choice than two way slab in terms of cost and time. Unlike two way slab, it requires more beam & formwork to build and skilled workers needed in this construction. Flat slab has no limitation to make changes since there is no beam to be considered. Floor height in two way slab is lower compared to flat slab due to the installation of different piping. This building is mainly for residential purpose, the deflection of slab would not be a big problem unless there are excessive loads. For example, commercial block needs superior strength to support each floor.

REFERENCE LINKS FOR SLAB:

http://keu92.org/uploads/Search%20engineering/DESIGN%20AND%20DETAILING%20OF%20FLAT%20SLAB.pdf

http://www.construct.org.uk/media/Flat_Slabs_for_Efficient_Concrete_Construction.pdf

http://www.concretecentre.com/technical_information/building_solutions/frame_elements/slabs/flat_slab.aspx

http://www.wisegeek.com/what-is-a-flat-slab

http://www.engr.psu.edu/ae/thesis/BIMTeam22010/Tech%20Assignments/BS-Tech-2.pdf

http://www.slideshare.net/yeasirmasud/flat-plate-slab-design-100103052

http://civilengineersforum.com/difference-between-one-way-slab-two-way-slab/

http://www.allinterview.com/showanswers/132093.html

http://www.slideshare.net/mtrego9441/slab

http://faculty.ksu.edu.sa/charif/Documents/Two%20way%20slabs.pdf

EXISTING FOUNDATION: PILING

Piling foundation is a group of piles that support a superstructure, normally used in multistory buildings. Its function is transmitting a foundation load to solid ground & resist vertical, lateral and uplift load. Waterlogged areas need this kind of foundation to deal with the geographical problem.

Pros:

- To withstand the heavy loads transmitting from top

- Can drive through dense layers to create stable foundation

- Most stable foundation

Cons:

- Expensive to construct this foundation

- Takes longer time to install

- Requires Sonotube or equivalent to shape the piling before pouring concrete

- Noisy installation

- Vibration can affect neighbor properties

ALTERNATIVE WAY: STRIP FOUNDATION

Strip foundations are by far the most common. The foundation is basically a strip, or ribbon, of insitu concrete running under the entire load bearing walls. These will normally include all the external walls and possibly some, or all of the internal walls. The depth and width of the strip depends on the building load and the nature of the ground. Normally used in strong soil base & non-waterlogged area and less than 4 story high building. Depth of foundation can be 600mm – 1200mm and the thickness of foundation in trench can be 150mm – 450mm.

Pros:

- No need skilled workers to build it

- Less expensive compared to piling

- More economic by using only concrete to construct

- Durability against chemical reaction

- Less impact on neighboring properties

Cons:

- Not suitable in weak and unstable soils

- Use in small or medium structures only

- Limited load carrying liability

- Weak against uplift force, wind forces and earthquake

ALTERNATIVE WAY: RAFT FOUNDATION

Raft foundation is an ideal foundation choice to support light weight buildings (3/4 stories high). It is a whole piece of concrete slab underneath superstructure and used in ground with very low bearing capacity or where excessive variations in ground conditions would cause unacceptable differential settlements.

Pros:

- Financially cheap due to the combination use of foundation as the floor.

- Shallow depth of foundation which needs lesser excavation compared to piling and strip

- Can cope with poor ground condition

- Easy to construct

Cons:

- Weak when it comes to support heavy loads

- Susceptible to edge corrosion

- Not intended to cope with high point loads

JUSTIFICATION:

Piling foundation seems to be the best choice since this building is 5 story high, which is a really huge burden to foundation. Strip and raft foundations are not constructed for high buildings because the requirement of the building itself does not suit. Piling foundation may cost more than strip and raft foundations but it is more beneficial in long term consideration. Piling can last longer when there are heavier loads exerting on it, where strip and raft foundation have their limits. So, piling foundation can be said that it is the most safety foundation to use in this case since water table in this area is not a huge consideration.

REFERENCE LINKS FOR FOUNDATION:

http://www.ekt.bme.hu/ArchEng/Foundations%20(S-D)-s.pdf

http://buildingcontractorsecrets.com/2008/03/types-of-foundation-and-their-uses/

http://constructionstudiesq1.weebly.com/strip-foundation.html

http://www.treadwellrollo.com/files/FileUpload/63/HJY%20-%20SEAONC%20Presentation%20-%20PowerPoint.pdf

https://environment7.uwe.ac.uk/resources/constructionsample/cd_hybrid_mini/topic_foundations/foundationtest.pdf

http://www.jwlowry.co.uk/wp-content/uploads/Brown-Field-Site-and-Suitable-Foundation-Types.pdf

EXISTING ROOF: PITCHED ROOF

Pitched roofs, which have at least 2 slopes that rise to meet at a peak, it is constructed in such a way to provide usable space for storage or additional living space. A pitched roof is also defined by having a roof pitch above 1.5 degrees or above fall of 1 in 40. Construction materials will differ depending on the pitch of the roof.

Pros:

- Longer lifespan than flat roof

- Durable

- Higher weather resistant

- Good ventilation of air and heat

Cons:

- Greater burden on foundation

- Higher cost to construct (more complex design, additional building materials and extra man-hours cost)

- Rafters and engineered trusses must be installed to support a pitched roof, more cost needed

ALTERNATIVE WAY: FLAT ROOF

Flat roofing is defined by having a roof pitch below 1.5 degrees or a fall of 1 in 40 and can comprise of different products. It consists of a horizontal base which is fixed to the ceiling joists underneath with a waterproof membrane applied on top.

Pros:

- Less expensive to install than pitched roof

- Less labor and materials cost

- Can be constructed supporting by beams

Cons:

- High maintenance fee

- Does not drain well, so water can easily accumulate

- Shorter lifespan

- Bigger surface of flat roof exposed to sun, which will absorb more heat and may cause uncomfortable heat

JUSTIFICATION:

Pitched roof is better to install in this residential building. Its higher degree of slope provides a better water evacuation compared to flat roof. It does not need much maintenance since the water cannot accumulate on top of it due to higher slope of pitched roof. Long term consideration is one of the factor that pitched roof is better because of less maintenance needed and longer lifespan. In this case, burden of pitched roof would not really affect the building structure since piling was using as its foundation.

REFERENCE LINKS FOR ROOF:

http://www.doityourself.com/stry/pitched-roof-vs-flat-roof#b

http://www.airm.ie/system/download_images/53/original/GFF%20-%20flat%20Roof.pdf?1393261490

http://homeguides.sfgate.com/pros-cons-flat-vs-pitched-roofing-6931.html

http://www.improvenet.com/a/why-pitched-roofs-are-better-than-flat-roofs

http://www.morganasphalte.co.uk/news/advantages-disadvantages-pitched-flat-roofing/

CONCLUSION:

From this research, important thing needs to show here is lower cost on time and time saving. It shows that both slabs provide the same functions. In comparing to each other, flat slab has more advantages against two way slab in terms of lower cost spent, lower man-hours cost, and unskilled workers will produce the same outcome. While in choosing best roof to be used, considering that Malaysia is a tropical country and raining happens. Rain will easily accumulate on roof especially at night since there is no heat to evaporate it. In foreign countries with 4 seasons, they need flat roof to prevent frozen on top, but in Malaysia, pitched roof provides higher ventilation of air since the high humidity may heat up from top and uncomfortable warm will be flowing out. Expensive during constructing pitched roof but less maintenance needed; cheap to construct flat roof but more maintenance fees to fix leaking flat roof. In choosing type of foundation to be used, considering that this building is 5 stories high, piling would be the best choice to support the heavy loads and burden from pitched roof which is heavier. While strip and raft foundation cannot provide such a heavy load bearing as piling does because they are not intended for high buildings. In term of safety, piling can be said the best among those 3 types of foundations mentioned. Piling foundation can also support the whole structure if the owner of any unit wishes to change its internal layout since it is flat slab, which may have heavier load added to the structure of building.

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