BACHELOR IN QUANTITY SURVEYING

Report Assignment

Name: Liew Yong Sheng 0315108

Davin Young Qiao Wei 0321065

Wong Geng Sen 0321690

Tay Sy Min 0320813

Kevin lee hee xian 0315192

Lecturer: Ms.Azrina

Subject: Construction Technology

Abstract

The purpose of the project is to analyse and understand the horizontal

structural elements of The Gardens Mall starting from Foundation, Slab and

finally Roof by first analysing the nature of the building and its environment.

Through research, the report also compile the possibility of substituting the

elements used with recommendations to explore the possibilities and result of

the usage of these elements by research and reasonable deduction alone.

Table of Content

Introduction 1

Part I: Visualization 2

Part II: Analysis

- Foundation

- Slab

- Roof

4

Part III: Recommendation

- Foundation

- Slab

- Roof

13

Conclusion 22

Appendix 23

References 28

Introduction

Within the hearts of Mid Valley City stood The Gardens Mall. Along with Mid Valley

Megamall, The Gardens Mall is 816,657 sq. ft. of let net lettable retail space and retail

tenants at 31st March 2012 and 8 storey height. The entire building are divided into eight

floors starting from the LG floor to 6th floor containing 200 outlets for fashions, food and

beverages, jewellery and time pieces and etc. Parking zone are divided to four lower floors

after lower ground floor from P1 to P4 under Zone B.

The Gardens Mall was built as a single mall with department stores anchoring on both ends

in symmetry. The Gardens Mall is a premium fashion mall and targets the upper-middle to

upper income families and relegate in nearby affluent residential area such as Seputeh,

Bangsar, Taman Desa and so on. Being connected to Mid Valley Megamall which is

connected to the KTM station, The Gardens Mall also gained traffic as high as Mid Valley

Megamall making The Gardens Mall a success among nobles.

The Gardens Mall, built after and also opposite of Mid Valley Megamall in Mid Valley City, is

surrounded by roads including Jalan Maarof, with Sungai Klang at the side, and Lingkaran

Syed Putra. Here we can deduce the soil condition around the area during the construction

of The Gardens Mall was considered man-made because of how close it is to Mid Valley

Megamall and Jalan Maarof. However, the soil condition within the area itself could be

deduced to be less suitable for construction. The deduction was made due to Sungai Klang

beside Jalan Maarof where the soil in underground level was more moisturized to be stable.

Part I: VISUALIZATION

Part II: ANALYSIS

Foundation

Foundation is required to transmit all the dead, superimposed, and wind load from a

building to soil on which the building rest. The choice of foundation used depends to a large

extent upon their properties relative to the environmental requirement of the building and

the strength property of which the foundation used.

To deduce the foundation used, we will need to first analyse the surrounding of The

Gardens Mall and it’s construction history. As mentioned in the introduction above,

Figure 2.1 Suitability of

foundation types to

various soil

The Gardens Mall, during its construction, are surrounded by man-made soil as could be

seen in the map in Part I. However, the soil on The Gardens Mall itself would be deduced to

be unsuitable for construction based on the Sungai Klang’s water moisturizing the soil of The

Gardens Mall even after the construction of Mid Valley Megamall.

Based on this figure, it is highly likely the soil used for The Gardens Mall was soft silt clay.

With this, we believe that if the wrong foundation is used, subsidence would occur. Next to

consider in choice of foundation would be plan and height of the building, The Gardens Mall

is a tall building consisting eight floors and four basement with the area of 800 thousand

sq.ft.

Through these analysis, we have come to a conclusion of the engineer’s choice of

foundation: Raft Foundation. Raft foundation consist of a raft of reinforced concrete under

the whole area of a building. Normally it is used when there are no firm bearing strata of soil

exists at reasonable depth below surface.

Figure 2.2 Sample of a raft

foundation

Usually supported by a compacted hardcore base which extends beyond the edge of the

raft. In order to allow the outer leaf of the wall to continue below reduced level, the edge of

the raft is stepped.

There are benefits when using raft foundation. Technically speaking, it is quicker to

construct and a lot faster to complete because it avoid planking and strutting in a self-

supporting soil as compared to conventional strip footing. In comparison to other

foundation, raft doesn’t need a deep excavation. This makes the project as large as The

Gardens Mall a lot more economic.

Slab

Slab is, by definition, a horizontal plane that is supported by vertical columns if suspended

that which consolidates and stable enough to bear dead and life load. Based on observation

alone (see appendix), we have come to a conclusion of the slab used would be a two way

slab.

Two way slab is a slab supported by 4 beams of 2 different directions, usually in ratio of

longer span to shorter span that is less than 2. The reinforcement bar are placed parallel to

the beams in two direction as well to ensure loads are distributed equally. By concept, the

loads are supported in two direction.

Figure 2.3 and 2.4 shows Two Way Concrete Slab with

labels and description

Two way concrete slab is generally more economic because of its large effective depth. It is

also best used when there is possibility of shear forced because the structure holds relative

ease with its beams could be reinforced against these forces. In addition, it provides great

amount of lateral stiffness due to the presence of beam and efficiency of beam-column

connection. However, the complexity of reinforced bar and formwork increases its

production price which would prove slight disadvantage of using this structure though we

should also remember that The Gardens Mall’s budget was supported with Mid Valley City’s

profit.

Roof

Regardless of the purpose of the building, be it commercial or industrial, roof is required.

There are several types of roofs in the building industry but all serve the same functions

which are:

1. To provide shelter for weather such rain, wind, snow and dust

2. To prevent excessive heat loss during winter

3. To keep the interior of the building cool in the summer.

4. Designed to accommodate all stresses encountered especially strong winds.

5. Designed to accept movement due to changes in temperature and moisture

content.

6. To provide lateral restraint and stability to adjacent walls

7. To resist penetration of fire and spread of flame from external sources

And also a few factors to consider when choosing the type of roof:

1. The size and shape

2. Aesthetic appearance

3. Economy

4. Function of Building

Gambrel Roof

A Gambrel roof is usually, as defined by Harper and Douglas in Online Etymology Dictionary, a

symmetrical two-sided roof with two slopes on each side. The upper slope is positioned at a

shallow angle while the lower slope is steep. In this case however, The Gardens Mall opted

to use half gambrel roof.

Figure 2.5: Bird view ofThe Gardens

Mall.

Figure 2.6: view from inside - One sided gambrel roof Figure 2.7: view form inside - Dome roof

The Gardens Mall adapted the gambrel roof system. The Gardens Mall is placed in an area

which encounters with storms and strong winds very frequent throughout the year

especially during monsoon seasons, this is why gambrel roof is used mainly to withstand this

kind of weather. According to one of the contractor’s document by Henry Butcher Malaysia,

the roof consist of weather-proof finishes as well to provide maximum immunity against the

bad weather of Kuala Lumpur.

Figure 2.8 Effect of win on buildings

Besides, it is also quite clear that this type of roof was chosen for its aesthetic qualities.

Gambrel roof requires very little frames for support therefore providing the architect with

more and better options when designing the building. Hence, with the right finishes and

some high order designing, it can look very appealing from the inside especially for

commercial buildings such as malls.

A roof truss serves the same function as the beam of a slab. It consists a series of separate

members instead of a continuous plate. A roof truss supports the load of the roof while a

beam, similarly, supports the load of a building. In a truss, the lower horizontal part and the

upper horizontal part provides support and carries tension and compression of the roof.

According to Henry Butcher Malaysia, a portion of the roof was constructed with steel

trusses covered with glass panel. The type of roof truss used here is Warren trusses and it’s

made up of mild steel. Warren trusses have inclined web members are sometimes

introduced to reduce panel length of the top cord which is compression.

Figure 2.9 shows the trusses used in The Gardens

Mall

Figure 2.10 shows a simple figure of a truss

Steel roof trusses are mainly used for industrial or recreational purpose. A steel truss is a

plane frame consisting of a series of rigid triangles composed of a compression and tension

members. The compression members are called rafters and struts, whereas the tension

members are termed ties. According to “Construction Technology 2” by R. Chudley, Standard

mild steel angles with the recommendations of BS 4848 are commonly used as the

structural members and these are connected together, where the centre lines converge

with flat shaped plates are called gussets.

A few disadvantages that needs to be considered when using Gambrel Roof is that it have

very poor ventilation. It requires a specifically designed ventilating system by engineers to

increase better performance in ventilation. This means that Gambrel Roof will be costly in

its maintenance including the consideration of its height in The Gardens Mall.

Dome

A Dome is an element in architecture that resembles the hollow upper half of a sphere.

Pantheon in Rome, Italy was the first to use the structure of Dome back in 27 BC during the

reign of Augustus Caesar. In later years, many building in Islamic region adopted this type of

roof to encounter hot weather in the Middle East.

Historically, domes were constructed using mud-brick and then baked brick and stone were

introduced in later stages. In modern times, with more building materials and better

understanding in laws of physics in structures, methods of construction have changed.

Bricks and blockes are now replaced with iron and steel beams, cables and pre-stressed

concrete which eliminates the use of external buttressing and made thinner domes possible.

The light weightiness in modern domes not only allow greater spans but also allow the

construction of moveable domes for modern sports stadium.

Similar to the gambrel roof, The Gardens Mall also uses Dome roof to improve the overall

appearance of the mall. As illustrated in the picture below, the bottom part of the dome

roof consist of reinforced block in my opinion and it is layered in English bond which is very

pleasant to look at. The

layer above the blocks is

timber followed by marble

and then the top is a glass

window

The strong and durable

structure is also a perfect

defence against storm just like the gambrel roof mentioned

before.

Besides that, the dome roof also provides a more cooling surrounding inside the building as

it has good air circulating properties. This is extremely advantageous to a hot and humid city

such as Kuala Lumpur. Thus, making the building more environmental in subject of air

conditioning as well as economical in its energy saving and also low cost in maintenance and

construction depending on the type of material used.

Figure 2.11 - Traditional construction of a dome roof

where bricka nd block were used

Figure 2.12 - Traditional construction of a dome roof

where bricka nd block were used

Figure 2.13 shows the dome used in The Gardens

Mall

However, if not done wisely, dome are more prone to material wastage. Geodesic dome,

which is a high likely method in dome construction in The Gardens Mall, has less surface

than a conventional structure, nonetheless cutting triangles from sheet material is very

uneconomical unless material of which the dome is built is carefully chosen.

Unlike the gambrel roof, the dome roof do not require any trusses frame nor joists for

support. However, if the dome structure is large then it requires trusses and framing. For

example, the Civic Arena in Pittsburgh, Pennsylvania adopts the dome roof and has trusses

to support it.

Figure 2.13- Civic Arena

Figure 2.14- Truss on Civic Arena

Part III: RECOMMENDATION

Foundation

1. Pad Footing]

Pad footing is a shallow foundation that is usually used to support individual or multiple

columns, spreading the loads to the ground below. Unlike raft or strip foundation, pad

foundation do not run around the building but rather as a single point around the

building. Like strip foundation, its thickness is governed by reasonably strong subsoil

exists near surface of ground or at the level of proposed basement floor.

Figure 3.1 Pad Footing

However, the possibility of using Pad Footing

instead of Raft Foundation is deemed to near

impossible because Pad Footing cannot take

excessive weight. The Gardens Mall holds a

load worth eight floors. For this to work, the

soil is required to be stiff such that mall would

not subside which, as discussed earlier, was

not the case. Despite being surrounded by man-made soil environment, pad footing is

still weak against differential settlement. This means that if this foundation is used for

the Mall with its dimension remained, the mall would suffer severe cracks and

eventually would crumble down.

In order to avoid the damages, deep excavation is needed which will increase labour

work and price of construction. Not to mention such a technique is not economic.

Henceforth, it is near impossible for the engineers to choose this foundation for the

mall.

2. Pile Foundation

Figure 3.2 Pad footing of a house

Pile Foundation are thin columns of

reinforced concrete that transmit the

load deeper into the subsoil where

material that are dense could be found

to prevent collapse or uplift or by

friction between soil or a combination

of both.

Through thorough consideration, there is a debate subject to either pile foundation or raft

foundation. By the end of the day, we have concluded that raft is a more suitable

foundation mainly because it is costly with unworthy cause. First of all, construction such as

this would require heavy equipment for handling. Boring piles into deep soil would take

more labour for the construction. Second, the exact length required at the side could hardly

be determined in advance. Along with the problematic dimensional stability of the ground

as an issue.

It is suggested in Mitchell’s Structure and Fabric Part 1 6th Edition that piles can be easily

formed by boring in firm soil. This pile is known as short bore pile foundation. This pile is

usually used in shrinkable clays and reduce the amount of excavated soil when the pile is

bored over trench and strip. It is faster to construct and can work in any weather.

However, we find a few probably rather similar to the general pile foundation. Like pile

foundation, short bore pile is costly due to similar reason except excavation is not as deep.

The soil that is suitable for this pile is not a characteristic of soil mentioned in Part II of

Foundation. These two alone proves that this foundation is not suitable for the mall.

Overall, there are more disadvantage to use Pile Foundation that using a Raft Foundation

despite its greater stability and capability in transferring greater loads to the soil.

Slab

1. Flat Slab

Flat slab is a reinforced concrete flat slab also known as beamless slab. It is basically a

structure that are supported directly by columns without beams. A part of the slab bounded

on each of the four sides by centre line of column named panel. Usually it is thickened close

to supporting column to provide enough strength in shear and to reduce negative

reinforcement in support regions.

Figure 3.3 Two way flat

plate and two way flat

slab.

Unfortunately, it have only medium spans and is not suitable for Malls such as The Gardens

Mall. It is necessary to know that The Gardens Mall holds a lot of mechanical conducting for

services such as air conditioning, water piping system and so on. Flat Slab have panels that

will interfere with these mechanical ducting. Should flat slab be reinforced, deflection at the

middle strip would be perilous.

2. Grid Slab

Grid Slab system involves beams spaced at regular intervals in perpendicular direction and

monolithic with slabs. They are usually employed for architectural use such as auditorium or

theatre halls. Voids in the ceiling in the form of rectangles or squares are advantageously

utilized for architectural lighting. Sizes of beam running in perpendicular directions are

generally kept the same. Sometimes, a diagonal grid is used instead of a rectangular beam.

Compared to Two-way slabs. Grid slab are found to be more efficient in load transferring. It

is distributed more evenly to the support due to the high surface area of the structure. This

reduce the cost of supporting structure such as heavy moving loads. Grid slabs could be

used anywhere in the plan giving architects more freedom in space planning.

Grid slab cost greatly due to complexity of its form which takes more labour work and more

surface area for formwork. When grid slab are used to support floors, fire protection is

required which is hard to achieve parsimoniously due to the high amount of surface area

needed to be covered.

Roof

1. Flat Roof

A flat roof is a low pitched roof and is defined in BS3589 as a pitch of 10o or less to the

horizontal. It is suitable for spans up to 4000mm, usually covered with a reinforced

concrete slab or patent form of decking.

It is agreeable among us that all malls should have a flat roof system because the

roof top can be used for many occasions. For example, the roof top can be used to

build a garden so that customer can enjoy the scenery. Opened air on the roof top

also enable customers to have a wonderful view over the city. Similar to One City

Mall, fine dining restaurants make use of the scenery for greater attraction. Roof top

dining is deemed romantic and considered popular.

The finishes used for flat roof are ceramic tiles and glass in the center. The ceramic

tiles provide good aesthetic qualities while glass can allow customers to have an

overhead view of the mall. That way, the mall won’t just have extra living space on

the roof top but also attract customers. For the roof top to hold restaurants, the

garden and the people on the roof, the roof is required to be strong in order to be

able to withstand such a load. Henceforth it is suggested that steel bar reinforced

concrete slab would be perfect for the job.

Unfortunately, there are several drawbacks in using flat roof system. Flat roof system

have poor insulators against the transfer of heat. In addition, should the roof is not

properly constructed, pools of water will collect on the surface after the rain. This

means that maintenance cost is needed. Another choice would be the roof to be

constructed with a slight pitch or a good drainage system. The roof must also have

waterproof membrane such as PVC to prevent leakage to the floors below.

2. Butterfly Roof

A butterfly roof is a V-shaped roof constructed of two tandem pieces which are

angled up on the outside. The midsection is angled downward where two pieces

meets the valley. This roof system is best used in bungalows in the west. Popular for

modern, eco-friendly and tropical home design.

The advantages of the roof is that the upper angle of the outer edges allows window

to be used, allowing natural light to enter. It is also pleasant and beautiful to view at.

This extraordinary type of roof design would, we all believe, attract more

shopaholic’s and noble’s attention.

The valley in the midsection of the butterfly roof allows rainwater to be collected,

making it beneficial for high drought areas. The water collected can also be used for

flushing toilets. A downspout is normally attached to a rain barrel is installed for this

reason.

The cons of the butterfly roof would be the complexity of the design that makes the

butterfly roof more expensive to build as well as maintaining it. Waterproofing in

butterfly roof must be ensured. Risk of a clogged drainage system will cause water to

pool or leak and will result in weakened columns weaken over time which could

cause immense casualty.

Conclusion

In brief, the importance of studying these horizontal elements in a building’s structure

begins with the analysis of structures that exists around us. What binds us to the bright

future of a greater civilization begins with research of those that can be analysed through, in

this case, observation alone.

There was a saying, “Life could only be understood backwards.” While similarly, the

structural elements of the existing building could be understood by studying the research

done by men who dedicated their time and blood to write down what they have learnt

through mistakes and experiment, both of which costs the lives of thousands of men, for the

sake of a greater civilization. Their hopes and effort will come to play, for what they have

recorded have benefited us not only the analysis and the understanding of the physics

applied within these structural elements but also the thousands of possibility of application.

From material to structural system, we now have the knowledge of how these structural

elements work in a building. What’s left to be explored is the creativity in using these

material and system to combine a new possible system, one that would bring us a step

further to the future. A step further to a greater civilization. A step forward to create a

better world for both nature and human.

For this, we say, appreciate all of the source provided by men who dedicated their lives for

us. Appreciate what men have built for us. Appreciate the knowledge we have explored and

shared in this report. Finally, appreciate the existence of all that is below and above the

clouds that watches over us.

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-End-