School of Architecture, Building and Design
Building Construction II (BLD 60703) Project 1: Skeletal Construction (Temporary Bus Shelter)
Group Members: Tan Yik Ting 0325043 Tan Yincy 0318355 Lim Zia Huei 0321031 Teo Kuo Chien 0320195 Rachael Cheong Ong Shi Hui 0320303
Content
Introduction
Idea Development Design concept Precedent studies Design Analysis Design Consideration
2 3 4 6
Construction Material selection Construction details and components Process
8 9 17
Test Result Forces and strength studies Analysis and Conclusion
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Introduction This project aims to create an understanding of skeletal structure and its relevant structural components and let us experience and improve our understanding about skeletal construction as one of the important and widely used structure for building support. We should be able to manipulate the skeletal structure to accommodate to our design and demonstrate a convincing understanding of how the structure works and reacts under loading. In a group of five to six people, we were required to construct a temporary bus shelter by combining two basic forms. The strength and flexibility of the materials and the stability of the structure itself would be tested to detect how it could endure lateral forces.
Design Development STRUCTURE
Tetrahedron + Hexagonal Prism -A very rigid structure -Took up to many space -Aesthetically unappealing 1 column
3 columns formed a structure
Cuboid + Cylinder - More space - Aesthetically more appealing - Experiment with the push and pull of forces X- column
The number of the structural components are reduced and the heavy looking structure is developed into a lighter looking structure.
ROOF The flat roof is developed into a curved roof which allows the easier flowing of the rainwater to the ground.
Idea Development
Design Concept INSPIRATION Light Weight
Low Impact
Sustainable
Efficient
The intention of the design is to create such open space with minimal structural elements and the absence of vertical columns. The challenge is to take bamboo not just as a finishing material but also as a structural element. The building uses no steel or fabricated structural materials. This unique structure bend in such way in both direction allows to experience a 4 meter wide and 3 meter high space without any vertical columns by concentrating all forces at the center where the interlocking part are and then towards the foundation.
‘’
While incorporating eco-friendly techniques into your daily routine is
The design inspiration came from the
certainly a fantastic way to help out the
flexibility of bamboo. The beauty of
environment
bamboo is that it’s extremely flexibility,
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allowing it to bend without snapping. It was able to sustain In earthquake area. 2
Precedent Study wNw Cafe
Good ventilation- The spaces allow airflow and cooling capacity of water.
Mushroom-shaped Bamboo Pavilions
The V-shaped roof relates to the surrounding trees and create an open space with breathtaking views.
Bus Shelter
Indochine Open-air Cafe
Open-air restaurant which is elegant in its simplicity. Traditional bamboo construction techniques were used.
Centrally positioned round skylights that Thatch overhangs from the inner provide additional natural lighting and basket-like structure creates deep eaves ensure optimal ventilation. and protects the whole bamboo structure from harsh sunshine and heavy rainfall.
Respecting and using the bamboo’s mechanical qualities, the bamboos were bent into strong and flowing shapes.
Linear sitting area to maximize the sitting area without blocking the view. Easy to access.
Constructed for commuters. The structure is intended to demonstrate the structural efficiency of bamboo and raise awareness of it as a strong and versatile building material.
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Bamboo as a Building Material Bamboo is a material that is very close to people's lives in tropical regions. It is an integral element in traditional Malay architecture besides wood, palm and rattan. The Malay vernacular architecture is highly admired because of its eco-friendly design, custom-friendly and user-friendly culture. Bamboo has a great potential in the construction industry, especially with its application in architectural design. As a material, bamboo is versatile, strong, renewable and environmentally friendly as its waste from construction is non-polluting and can easily be disposed of. Only mature bamboo of 4-6 years that has not flourished is used in construction. Example of bamboo that is used in construction is Dendrocalamus asper. Besides that, bamboo has twice the compressive strength of concrete and roughly the same strength to weight ratio of steel in tension. Not only that, experiment has shown that the hollow tube shape of the bamboo gives it a strength factor of 1.9 times over an equivalent solid pole. The reason being that in a beam, the only fibers doing the work are those in the very top (compression) and bottom (tension). The rest of the mass is dead weight. The strongest bamboo fibers have a greater shear resistance than structural woods, and they take much longer to come to ultimate failure. One of the structural advantages of bamboo is its strength and lightweight properties whereby properly constructed bamboo buildings are resistant to wind and earthquakes. And with new technologies, bamboo construction will be more enduring, and through the conservation and preservation of the bamboo species, better quality of bamboos could be implemented that would improve and enhance their performance. However, bamboo can be attacked by fungi and insects and untreated bamboo have a life expectancy of less than five years. The risk is especially high in bamboo buildings if the buildings were in fire compared to other buildings. This is because the combination of bamboo and matting as well as the tendency of the internodes to burst cause rapid spread of fire. The risk increases when the joint lashing is destroyed and this can cause the building to collapse. Hence, it is important to promote the correct use of treatment of bamboo that will be used as building material. The shelve-life of bamboo could definitely increased to 50 years or more by applying the appropriate treatments which is also more economical and sustainable in the long run. Chemical treatments is used for our project. For chemical treatments, water is used as solvent to carry preservatives into the cells of the bamboo. Water-soluble salts are dissolved in water that evaporates on treatment leaving the salts inside the bamboo. This treatment is most effective as it have longer effect against fungi and insects and have fire retardant properties because of high concentrations of salts.
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Design Analysis Initial Design
Tetrahedron + Hexagonal prism The columns are formed with two tetrahedron. An upside down tetrahedron were placed in a way that it intersect with another tetrahedron. The center of the roof structure shows a hexagonal prism from the top view. Advantage: The structure is very stable Disadvantage: Columns took up too many space. Too many components in one column.
Columns
Space
Columns
Columns
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Design Analysis Improved Design (Final Design)
Cuboid + Cylinder Changes from the initial designs are: 1) The number of columns were reduced from three main columns to two main columns. 2) The size of the columns were reduced. 3) The components of the structure were reduced. 4) Curved column incorporated that utilizes the flexibility of bamboos Advantages: Aesthetically more appealing, the structure looks ‘lighter’ and spacious. The space provided is maximised within the limitation. Easier to access. Disadvantage: No found disadvantages at the moment.
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Design Considerations Roof - Rafter are used as support. - The roofing need to be able to withstand the weather condition.
Structure - The size of the columns are reduced to maximize the space and the bamboo columns are multiplied to strengthen the support. Each sets of column consists of 4 bamboo curves interlocking with each other. - The columns are inserted into the concrete footing to provide support for the whole structure. - The components are reduced to make the structure looks lighter.
Seating - The seating is connected to the flooring. - The curve seating is changed to linear seating as it takes up a smaller space.
Circulation The linear form is accessible easily . By placing the columns in the center, the space is separated into two parts where it act as a guide for users to enter the front and the back entrance of a bus.
Flooring - The floor beams are connected to the footing. - Concrete footings are used to support the flooring. - Beam is used for the area where more load will be exerted. 7
Construction
Construction Details and Components Material Selection
Bamboo Used as supporting columns. ( 20mm diameter) Advantage: Easy to cut, light building material, astonishing strength and flexibility.
Acrylic Canvas / polyester fabric (Tight weave) Used as roofing. Advantage: Lightweight and stretchable fabric with relatively low mechanical properties, water-resistance, durable.
L-Shape Bracket Provide lateral stability of support to the beams.
Wood Used as ground beams, roof beams (10mm x 20mm) and floor joist ( 10mm x 10mm) Advantage: Safe, light, durable.
Concrete The bamboo columns are connected into the concrete pad footing with certain treatment. Advantage: High durability, resistant to wind and rain.
Recycled Timber Decking Used as flooring. Advantage: Easy to clean, eco-friendly if renewable timber is used.
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Construction Details and Components Technical Drawings 300mm 2000 mm 2700 mm 4000 mm
PLAN FRONT ELEVATION
BACK ELEVATION
3000 mm
PERSPECTIVE
LEFT ELEVATION
RIGHT ELEVATION
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Construction Details and Components Joints and Connection Friction-tight Rope Connection This connection is the most common connecting methods in making bamboo joints. Traditionally natural materials such as bast, strips of bamboo, rattan/hemp, and cocos/sago palm fiber are used as the rope in connecting bamboo poles. Nowadays, iron wire and plastic tapes/ropes are also used for friction-tight rope connection. Some examples of traditional bamboo lashing are square lashing, round lashing, diagonal lashing, shear lashing, tripod lashing, floor lashing and ladder lashing. Traditionally natural material - Rattan is used to tie.
Pros and Cons Pros: 1) Easy to build and simple for bamboo manufacturing. 2) Can be very strong with sufficient lashing techniques. 3) Can almost serve all the circumstances we need in building with bamboo. 4) Can drastically reduce the possibility of bamboo cracking because no notches or holes are in need in making such connections. 5) Easier for sealing because we can apply epoxy or other materials as a coating.
Cons: 1) It will cost more bamboo materials. 2) The choice of rope material is another important consideration. 3) The rope may be damaged by moisture, rot, insect, etc. 4) It requires some skills in doing lashing work. Shear Lashing
Square Lashing
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Construction Details and Components Joints and Connection
Terminology
Lashed joints are used in the structure to joint and secure all the bamboo in place. It is the most common method of jointing bamboo. Lashing is found in construction across the world and can be traced back over thousands of years. All the joinery in the structure is based on two types of lashing, shear lashing and square lashing. These two methods are used throughout the structure for adequate support and strong connection. Rattan is used to tie the column and beam.
Square Lashing
Lashing: Used for joining two or more poles together with a tying material. Wrap: A wrap is a turn around two or more poles. Frap: A frap is turn made between two poles to pull the wrap together. Clove Hitch: Used for joining two or more poles together with a tying material.
Shear Lashing
A shear lashing shall begin and end with a clove hitch. Two are more poles shall be first wrapped and then frapped to tighten the pole. This lashing is used in connecting the elements of columns together.
Square lashing shall begin and end in a clove hitch. It is used in a condition where there is no tendency for poles to spring apart. It is used on all 4 ends of the roof to connect beams to beams.
Columns connected to rafter on 4 sides
4 curved bamboo tied together to form 1 set of columns. 12
Construction Details and Components Joints and Connection Other joints that were used are L-shaped bracket joint, flat bracket joint, screw joint, nail joint and wood to wood joint.
L- Shaped Bracket Joint -
Used to connect wood to wood with right angle and wood to concrete. They are screwed on the inner corner of the wood where it’s hidden.
Advantage: Easy to install and remove. Aesthetically more appealing as the joint is hidden.
To hold the hardwood flooring in place. Timber flooring to beam (wood to wood). Advantage: Easy to install. Hardly visible as it is small in size
Screw Joint
Interlocking Joint
Bracket joint to wood.
Used to connect the beams and the joists. Double notched joint is used.
Bracket Joint
Wood
Flat Bracket Joint
Nail Joint
Advantage: Avoid the beams and joists to move away from their positions. The joint is stronger than single notched joint.
Used to connect the bench to floor beam (wood to wood). Advantage: Easy to install and remove. Could accommodate to different angled joints.
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Construction Details and Components Foundation Columns
Pad foundation are used to support the columns and the structure. Using pad foundation minimises costs and wastage for the concrete necessary at the same time reduce any excavation needed which you would usually use for pile, raft and strip. The foundation could be attacked by rain and wind, seepage water, ground water and termite. As the main structure is made up of bamboo and wood, special care must also be taken of.
During the casting and curing of concrete. bamboo will absorb water and expands, pushing the concrete away due to swelling. At the end of the curing period, the bamboo shrinks back almost to its original dimensions when it loses its moisture leaving voids around it.
Bench
Flooring
Additional pad foundation surrounding the structure as supporting foundation
To prevent that, a thin layer of water repellant epoxy would be applied to the bamboo surface followed by coating of fine sand. Materials such as asphalt paints, tar based paints and specific bituminous materials would also be used. Bamboo column 20 mm cement mortar Creosote coating over bamboo Sand packing
Pad Foundation Diagram
The floor is raised 400mm above the ground level, using concentre block to define plinth perimeter. It is filled with compacted earth and screeded with 20mm od cement mortar.
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Construction Details and Components Flooring
Columns
Recycled timber (hardwood) are used for the timber decking floor as it is easy to clean and maintain, very durable and gives an elegant and aesthetic look. It is the most long-lasting of all flooring types, and is also water resistant. It is also easy to resurfaced or disassemble that is suitable for a portable bus shelter and have a minimal effect on the environment as it can be reused or recycled from old wooden boards which have been reclaimed from old properties. Timber decking are usually hard and are less prone to damage when compared to engineered and laminated floors in the event when any heavy object falls on the surface. Besides that, it is the healthiest floors possible given its organic origin and non-electromagnetic nature tend to attract less dust. Hence they do not attract allergens, or molds that cause allergies which tend to travel with dust.
Timber decking
Columns
Floor plan
Hardwood decking
Joists Beams
Completed timber decking floor
Construction of floor beams and joists
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Construction Details and Components Roof Acrylic canvas was used as the roof as it is naturally breathable. Canvas fabric structure can keep cool on hot days and keep warm on cold nights. It have the ability to manage condensation which makes it a suitable material to be used as the roof. Can be installed quickly to shorten installation schedules and can be removed easily. It is also lightweight so it requires less structural steel to support the roof that enables long spans of column-free space which create a more functional and aesthetically pleasing space and earthquake resistant as it bear less building load.
Lightweight and flexible
Tensile structure: Canvas stretched, wrapping around the rafters and beam
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Process 1.
Formworks are made and pad foundation are cast-in-situ with the dimension of 1000 x 600 x 500 mm to support the bamboo columns. Pad foundation with the dimension of 250 x 600 x 500 mm are used as supporting foundation to stabilise the flooring.
2. Bamboo with diameter of 100mm is burnt and bent. Four bamboos are tied together as one column with square and shear lashing. Bamboo column are then embedded into foundation. The column are 2700mm high.
3. Ground beam is constructed with the
dimension 100 x 50 mm and attached to the foundation with L-shaped bracket. The area of the structure’s base is 2000 x 4000 mm.
4. Floor joists with the dimension 50 x 50 mm are then attached to the ground beam using interlocking mechanism.
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Process 5. The bench is built using wood with the height of 490 mm and is attached to the ground beam with straight bracket.
6. Roof beam with the dimension of 100 x 50 mm is tied to the column with square lashing.
7. Bamboo rafter is then tied to beam and column with shear lashing.
8. Timber decking with the dimension of 100 x 2000 mm are arranged and nailed to the ground beam.
9. Acrylic canvas is stretched and wrapped
around the rafter where the ends are sewed with upholstery thread.
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Test Result
Forces and Strength Studies Weather Resistance and Loading The type of construction and materials used are able to withstand rain, the uplift of strong wind and the scorching sunlight. The curved columns and roof was designed with the motion of air in mind and how air interacts with a solid object. Center hollowed columns gives way to airflow and the roof allows the wind to sail by. The acrylic canvas could block sunrays and cool down the shelter. As it is a tight weave canvas, it is also water resistant.
Loads were placed on the structure to test its stability and whether it could withstand certain amount of weight/ force
Water was poured on the canvas to test its degree of water resistance. 20
Forces and Strength Studies The roof structures carried the dead loadcanvas roofing and live loads- wind and rain. Transferring the loads to the roof beam which in turn transfer to bamboo columns and to the ground beams and then down to pad foundation. Floor joists also carried the live loads (standing user in the bus shelter).
Front view
Seated user's weight load is carried down to the bench and transfer to the ground beams. As the bench needs to take the live loads of 5 to 6 people, it could not connect to the floor joists because the support is not strong enough.
Side view
LOAD PATH
The two main curved rafter transferred the load to the four sides of the roof beams. The load and force is then equally transmitted to the four sides of the columns. Plan view
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Analysis and Conclusion
The final bus shelter design uses lesser supporting structure that make the whole structure looks light. The number of supporting structure can be reduced because of the mechanical properties of bamboo which is strong enough to support the structure and prevent bending. The loads are transferred from the roof through the columns and concrete footings to the ground. The concrete footing bears most of the weight. However, due to the compression and the size of the concrete footings, it enable them to withstand the loads. The structure passed through all the testing without any damage. Overall. we had increased our knowledge on skeletal structure and its relevant structural components. We tried to build a strong structure with less structural components. In order to do that, we explored the potential and limitation of the materials. We used the flexibility of the materials that we had chosen to build a organic form structure. We researched and improved our understanding on the different types of load and pressure/ forces and how it affects the structural integrity of a design. From that ( precedent studies) we explore and improve our design to its final structure.
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