1 Conclusion
In this assessment, the team felt that they effectively incorporated into the EWB Project various modern civil engineering techniques, as well as careful environmental consideration. The team also felt a level of passion for ethical action and social responsibility more than ever because of the project.
Furthermore, it was rather interesting to consider the different constraints on the engineering team because of the Tonle Sap context. Although the team was initially non-skeptical about an American perspective to a Cambodia solution, they soon understood what really was required was a multicultural, multitalented, and multi-technological solution.
As the Cambodian economy grows, so will the specifications of the MFB. As outlined previously, there is already some discussion on improvements of a possible second-generation MFB that uses even more lightweight material to increase buoyancy (thus load), as well as strength of material (thus product lifetime).
The MFB truly believes one person (or team) can change the world, and we hope the one which changes Cambodia, is the Modular Floating Bridge.
1 Sustainability & Maintenance
1.1 Environmental Impact of Materials
1.1.1 Timber and Deforestation
Because the MFB uses wood from trees that is being sourced from Cambodia, deforestation will be a direct result of the selection of timber.
v Negative aspects of deforestation is that it destroys the natural habitats of local flora and fauna that are unable to survive in an adversely different localized environment, due to both the different habit and climate conditions that arise (Telepool, 2008). Deforestation results in an increase in ground temperature, as a direct result of there being no physical coverage provided by trees. Soil will become significantly drier compared to the original moist soil conditions. A lower extent of carbon dioxide to oxygen exchange will result. Note however, the negative aspects of deforestation can be counteracted by the growing of more trees (North Carolina Christmas Tree Association, 2008).
v Positive aspects of using timber (and re-growing trees once the trees have been chopped down) is that throughout its lifecycle, a tree intakes carbon dioxide and releases this as oxygen through a process known as photosynthesis (Smith, 1997). Even when the tree is eventually cut down, the carbon is “locked” in the tissue and wood of the tree, until it is burnt, when it will react with the oxygen in the air (Current.com, 2009). Thus, you’re helping the environment!
Obviously, the issue is when deforestation occurs at a more rapid rate than forestation (which is a common occurrence since it takes longer to grow a tree than it does to chop it down). Nevertheless, in the long haul, as described in 2.1.1, self-use of Cambodian resources will increase the demand for wood, thus increase the price of woods, reducing price competitiveness, thus eventually, demand for Cambodian wood.
1.1.2 Marine Impacts
There are no predicted long-term effects to the marine life through the introduction and construction of the MFB to the Tonle Sap. All construction of the bridging system will be based on land, thus eliminating any potential contaminants and reducing any waste material from entering into the water supply during the construction process.
All assembly materials have been specifically treated and selected for the MFB’s construction, to minimize impact they pose to the sensitive marine ecology of the Tonle Sap, once the MFB implements.
Furthermore, the plastic barrels, which are the buoyancy device for our MFB design, are made out of recyclable materials and not severely distorted, thus will have no adverse environmental effects, and can be recycled and reused even at disposal of the MFB.
1.2 Sustainability of Materials
Due to the water exposure treatment, the wood can be immersed in water and will not show signs of warping and deterioration, as would if normal timber, if it were not treated. The long life expectancy of the timber is just one of the specifications of the MFB that make it a long-term sustainable advantage over its competitors for the Tonle Sap Region.
1.2.1.1 Polyethylene Drums
The drums used as the floatation devices have been molded from a polyethylene thermoplastic (River Lake Sea, 209), which exhibits exceptionally durability. These drums were selected, as they were very strong and lightweight, and furthermore would not rust, as it will be constantly subjected to water in the wet season.
However, since plastics will tend to breakdown from over exposure to the harmful ultraviolet light rays from the sun (Layfield Geosynthetics, 2009), and since the top of the drums will be above the waterline, an ultraviolet stabilized polyethylene material is used for the floatation devices in the bridge design.
It can potentially take centuries for Polyethylene (StateMaster, 2008) to fully breakdown, because of the synthetic polymers they are made from, thus their chemical stability; however if any faults were to happen to the drums, they can be recycled.
Thus, the material’s inactivity will mean little-to-no adverse affect when introduced into the bridging system in the Tonle Sap, providing a long-term sustainable component for the bridging network. The UV stabilizers only enhance their sustainability.
1.2.1.2 Wooden Planks
Although the MFB is designed to allow the polyethylene drums to be fully submerged in the water, the wooden planks used as decking along with the support beams that hold the MFB together are not underwater, though it will be constantly subject to water through waves, as well as rain. The treatment of wood with Tung Oil is intended to increase its life, so can be used in an aqueous environment (Food and Agriculture Organization of the United Nations, 2007).
As this bridge is going to be used quite frequently throughout the wet season, a good oil that stands up to the harsh conditions needs to be chosen. Although there was a range of products that provided water resistance, only Tung Oil could do it at a relatively cheap price, as well as being easy to obtain (Sankey, 2009). Tung oil comes from the Tung tree, and is a part of the flora of Cambodia’s neighboring country, Thailand (Thailand is directly West of Cambodia) (National Herbarium Nederland, 2009).
Tung oil enhances the toughness of wood and creates a hard durable surface (WoodBin Woodworking, 2009). Furthermore, it penetrates deep into the wood its fantastic waterproofing capabilities.
However, although a simple process, to maintain the water-resistance, the Tung oil needs to be reapplied every two to three months (Haymes Paint, 1998). The oil just needs to be re-applied to a clean surface and there is no need for the wood to be sanded down. Furthermore, pure Tung oil is a relatively safe product to use, as it is non-flammable and non-toxic (Refinish Furniture, 2009).
1.2.1.3 Steel Brackets
1.2.1.3.1 Corrosion Resistance
To connect the overall structure of the design, steel brackets were designed to connect the polyethylene drums to the wooded beams. Steel is a strong metal that is capable of doing its job well; however, steel can rust quite rapidly and will potentially be useless in holding the design together if this occurs. Steel will rust when subjected to moisture and oxygen (Holleman, 2001), thus the harsh wet condition of Cambodia and the oxygen in the atmosphere is the ideal climatically conditions for corrosion.
Thus, a layer of corrosion resistant paint is applied to the metal brackets (Suzuki, 1989), meaning the surface of the metal bracket is not exposed to the water. Therefore, the metal is unable to corrode and provides a sustainable join. Furthermore, the corrosion resistant paint includes rust inhibitive pigments, such as marine-grade primocon antifoul (MarineStore, 2009), ensuring that the steel lasts for the duration of the bridge’s service. Furthermore, it only needs to be reapplied yearly, with an ordinary paintbrush against a mildly sanded surface (preferably 40-80 grip sandpaper), requiring approximately eight hours to fully dry before it can be subjected to water (Micron).
If rust does appear on the steel brackets they can be recycled to a scrap metal yard where a kilogram of scrap steel can be sold for approximately 500-750 riel (approximately 15-20c AUS) as “scrap metal” (CAMNET, 2004).
1.2.1.3.2 Weld
The weld that joins the steel brackets together, which supports the floatation devices, provides strength, comparable to the original strength of a metal (Du, 2000). This strong join will provide strength for the bridging system over a long period.
1.2.2 Disposal
1.2.2.1 Polyethylene Drums
As polyethylene drums can potentially take centuries to break down (StateMaster, 2008), there is no need for them to be replaced. However, if holes and cracks do appear in the drums, the polyethylene drums can be recycled accordingly (Concord CA, 2009).
1.2.2.2 Wooden Planks
To dispose of the wooden planks that are no longer capable of doing their job safely, it is best that either the wood is:
v Reused for other purposes that is suitable, but isn’t dependent on the wooden planks being of paramount quality, such as small fences; or
v The treated wood can be recycled
It is strongly recommended that the treated wood must not be burnt in open fires. Although Tung Oil is non-toxic, it can potentially emit toxic chemicals in the fumes and ash when burnt (SWTOP, 2008).
1.3 Maintenance Strategy
The maintenance inspection will provide systematic guidelines that must be implemented in order to achieve the maximum functional usability of the bridging system and all it offers to the community.
Initial inspection will be conducted by qualified personnel, to ensure that the correct construction method and techniques are of a satisfactory standard. This will reduce stress on susceptible components of the MFB segments, once implemented into the community.
1.3.1 Inspection Methodology
1.3.1.1 Initial Material / Construction Inspection
The correct initial construction process is paramount in the long-term sustainability of the MFB segments.
The qualified personnel will review that:
v All materials used are the correct material as specified by the design: If incorrect materials are used for the construction of the MFB’s, detrimental effects may occur, as the incorrect materials will be unable to adequately support the anticipated loads, and the environmental conditions without deterioration;
v Defected materials will not be implemented in the construction process: Material defects and incorrect sizing will produce a “weak point”, which will be unable to support loading conditions, and hazardous environmental conditions. Despite it may be difficult to achieve, an optimistic target should be General Electric CEO, Jack Welsh’s “Six Sigma Program” (Antony, 2008);
v Materials dimension are made to the design specification: Components must be assembled to design specification for functionality and strength purposes;
Any poorly constructed bridging system will likely be seen by the Tonle Sap community as disastrous, as seen with the collapse of the Tonle Sap’s “25m Bridge”. Inspecting materials and construction integrity will reduce the likelihood of material and assembly failure, thus preventing any consequential safety hazards, and complex public relations issues that may result.
1.3.1.2 Routine Maintenance Inspections
Routine maintenance checks will be completed three times a year once the bridging systems have been introduced into the Tonle Sap community. This strategy enables any repairs to be made to the MFB components before, whilst, and after they are most used (during the wet season). Furthermore, other maintenance’s and adaption’s can be made accordingly.
1.3.1.2.1 Inspection 1: Pre Wet-Season
All sections of the MFB are to be inspected before the wet season commences, for:
v Material integrity
v Correct assembly
1.3.1.2.2 Inspection 2: During the Wet-Season
Samples of the MFB, generally of a size square root of the population (Baldwin, 2007), are to be simple randomly sampled (Yates, 2008) and inspected from various areas within the Tonle Sap, for:
v Material deterioration
v Material joints
If from within the samples there are consistent maintenance problems, inspections of a larger sample may need to be made (even the entire population). However, general maintenance and repairs will be based on accessibility, and the extent of the damage.
1.3.1.2.3 Inspection 3: Post Wet-Season
Samples of the MFB are to be simple randomly selected and inspected from various areas of the Tonle Sap, for
v Material deterioration
v Material joints
v Design improvements / Alterations / Checks against ISO Standards (ISO, 2009)
Because the MFB will be less used post wet-season, more vigorous checks can be achieved at this time of the year. An annual design review will occur, with recommendations, possibly improvements and adaption’s, to be made to the existing bridging system.
1.3.2 Special Maintenance Considerations for Susceptible Componentry
1.3.2.1 Weld Inspection
The weld will be inspected for join integrity upon all checks. This is vital in the construction of the bridging system as it provides the fundamental support for the buoyancy device. This will be maintained and repaired to ensure operational use of the bridging system.
The protective coating of the metal bracket is vital in corrosion prevention. This will be reapplied upon maintenance checks, subject to wear, to ensure the protection of the metal brackets, thus prevent rusting, hence material failure.
1.3.2.2 Bridge Loading
Despite the bridging system can only be subject to specific conditions (that is, only people and household items; and strictly no vehicle), because Cambodians may not follow civil regulations (European Commission, 2009), bridge loading has to be tested from time-to-time to ensure no safety issues will arise as a result of using the bridge.
1.4 Ethics
In designing the MFB, the engineering team faced little to no ethical dilemmas, riding on the back of a culture of “corporate social responsibility”, also known as “CSR”.
The MFB benefits Cambodia in terms of the “3 E’s”:
v Economy, both indirectly and directly, as mentioned in 2
v Environment, by the use of carefully chosen materials
v Entrepreneurship, by directly encouraging and inspiring other Cambodians; and indirectly by lowering costs of travel, thus lowering barriers to entry (to education, or business)
Posted on: June 6, 2009
1 Design Analysis
1.1 Alternative Analysis
1.1.1 Pontoon Alternatives
1.1.1.1 Pontoon Structure
Because the MFB would be subject to both physical forces and corrosion from both the atmosphere and the solution the bridge will float on, selection of the correct pontoon design and material was important. Furthermore, the pontoons would have to provide the buoyancy force and stability that a MFB requires. The materials available for the pontoon in the market are both vast and differ predominantly depending on environmental and social environments (as discussed in 2).
1.1.1.1.1 Barrel Design
Figure 4.1: Poly Drum
(ADCO Services, 2003)
Sealed short cylindrical drums, like that in Figure 4.1 and Figure 4.2, also known as barrels are regularly used in the construction of small rafts and pontoons (SookeRotary.com, 2009). These drums are readily available as many industries utilize these containers for the transportation and storage of liquids (Newcastle City Council, 2006). Barrels are available in different sizes and but the more common sizes are the 20L, 120L, 205L and 220L volume drums (Schutz DSL, 2009).
The physical size of a barrels provide little buoyancy and stability but do provide a streamline shape if orientated end into wind and water currents.
Using the Barrel Design for the MFB would mean using a product that had gone through the “test of time”, previously used for small rafts and pontoons, and was a readily available resource in Cambodia.
Figure 4.2: Steel Drum
(Global Industrial, 2009)
1.1.1.1.2 Cigar Design
Cigar-shaped pontoons are physically similar to barrels but have rounded ends and an elongated shape as seen in Figure 3.3. The elongated shape provides superior levels of stability if orientated perpendicular to a bridge span (Fidler, 2008). The increased displacement of this design over barrel design offer larger buoyancy forces, which can be utilized to support heavier bridge designs with fewer pontoons. The streamline shape of this design limits the effects of water and wind turbulence if orientated end onto the current flows and thus reduces the load on the anchoring system
Figure 4.3: Canary North Quay Bridge, West India (Darkwaters, 2009)
Although the superior levels of stability that the Cigar Design could provide, because the shape was unavailable in Cambodia, unless it was manufactured out of synthetic (and costly materials), this structure was left for reconsideration for second-generation MFB’s.
1.1.1.1.3 Box Design
Box design pontoons are commonly used in calm water environments (Alaska Department of Fish and Game, 2006) and are frequently installed in boat mariners. The design consist of a square or rectangular box section which provides the vessel for displacement on top of which is attached a flat surface used as the deck. The large area of displacement of this design provides large load bearing capacity with the trade off to large susceptibility to surface currents and wind loading. The stability of this design is poor due to the narrow displacement surface and so is generally installed between steel piles, which are used to locate and brace the bridge section.
Unfortunately, both the poor stability, and uncommon shape meant it was incompatible with both the environmental climate, as well as the environmental resources of Cambodia.
1.1.1.1.4 Displacement Design
The displacement design bridge is not regularly used in practice but does overcome the need to suspend a carry way, as seen in Figure 3.4.
Figure 4.4: Vera Katz Eastbank Esplanade and Floating Bridge
(Bridge Stories, 2009)
Unfortunately, this design is unsuitable for Cambodia due to the large effects water and wind currents would have on this structure due to its large longitudinal area.
1.1.1.1.5 Selection
Although the Cigar Design does provide increased superiority in terms of both stability as well as load, because of the unusual shape, considerations for this design will only be made for the 2nd generation MFB. Thus, because both the Box and Displacement Design are inappropriate for the Cambodian environment, the classic Barrel Design is selected by default.
1.1.1.2 Pontoon Material
The materials used in the construction of floats available on the market internationally are vast and vary greatly in their cost and availability. Not all materials listed in the conceptual analysis are appropriate for the use in the Tonle Sap, and is eliminated as necessary.
1.1.1.2.1 Concrete
Concrete is used in the construction of pontoons and offers good resilience to the effects of ultraviolet radiation (Hota, 2006). Concrete is a versatile material, which can be cast into complex shapes (Concrete.com, 2009) but is reliant on reinforcement steel to provide enough toughness in an environment such as the Tonle Sap.
Unfortunately, the density of concrete is approximately 2300 kg/m3 (Jackson, 1996) and thus limits both the size of a pontoon, and the load bearing capacity.
1.1.1.2.2 Steel Drums
205L steel drums are generally the standard in the petroleum industry (Perth Petroleum, 2009). It is appropriate for the buoyancy device used for the MFB, but is disadvantaged to the plastic barrel because plastic is generally less reactive to seawater than steel. However, the advantage of steel does not have the disadvantage of degeneration if exposed to ultra-violet light for prolonged periods (Askeland, 2008).
Despite the Tonle Sap is a freshwater lake (World Wildlife Fund, 2009), because of the reactivity of steel with salt water (Hall, 1997); the metallurgic process of converting steel into inox would increase the price above that which is accessible to Cambodians.
1.1.1.2.3 Non-Recycled Plastic Drums
Like steel drums, polyethylene (plastic) drums are often used in the construction of floats. Plastic barrels are generally used in the chemical industry, which require a corrosion resistant storage container (IndiaMart, 2009).
The selection of polyethylene drums, which have been treated with UV stabilizers, would extend the lifespan of the product (ASM, 1995) and provide a more sustainable design. Compared with other materials, plastic drums are one of the lightest (yet cheapest) materials (Hansma, 2007) and therefore can be transported easily, thus reducing cost of freight.
Since the price of treating polyethylene drums with UV stabilizers (ASM, 1995) would be far cheaper than that of treating steel in metallurgic process (Hall, 1997), plastic drums would be preferred over steel drums.
1.1.1.2.4 Recycled Plastic Drums
Among the more environmentally sustainable materials, which could be considered suitable for the construction of pontoons, are recycled plastics such as polyethylene terephthalate, high-density polyethylene and polyvinyl chloride (Lenau, 2003). These plastics are currently recycled and used to produce wheelie bins, which are comely, used in Europe for rubbish collection (Wheelie Bin Skins, 2009).
The production of recycled plastics relies on the collection of plastics currently thrown in waste deposits such as landfills (Waste Online, 2006). The plastic is then subjected to various chemical and mechanical processes in specialized facilities. Although this process has high initiation costs and logistics (Hinkley Center, 2002), increasingly complex and interlocked environmental regulations (AllBusiness.com, 2005) will mean increased demand in the long-term, thus good Return-On-Investment.
Fortunately, recycled plastic drums are readily available in Cambodia (EWB Australia, 2009).
1.1.1.2.5 Fiberglass Drums
A common composite material used in the marine environment for the construction of buoyancy devices such as boat hull design is fiberglass (Wiley, 1988). Fiberglass is a matrix of thermosetting resin in which a reinforcement mat of glass fibers is laid (Techstreet, 2004). Composites such as this require a mould in which the composite is laid into which determines the dimensions of the final product, as shown in Figure 3.5. Fiberglass has the advantage of being super-lightweight and can be filled with low-density foam, which strengthens the product as well as providing buoyancy.
Figure 4.5: Vera Katz Eastbank Esplanade and Floating Bridge
(Bridge Stories, 2009)
Unfortunately, the expense of fiberglass (Taunton Press, 1997) restricts access to such material. Nevertheless, consideration was given for second-generation MFB to include such materials.
1.1.1.2.6 Selection
Concrete was inappropriate as a floating device because of its restrictive density. Steel drums proved to be less potent (and readily available) than Plastic drums in the Cambodian economic and environmental climate. Fiberglass was another effective option, but was expensive.
Thus, recycled plastic drums were chosen by default.
1.1.2 Bridge Alternatives
A number of constraints limit the design of the bridge structure, which is supported by the pontoons. The most influential component on the bridge structure design is the pontoons as these provide both the buoyancy and stability to a non-pile tethered bridge designs.
As the supporting force of a MFB is solely supplied by the pontoons, the bridge structure and the load intended for the structure cannot exceed the buoyancy force (AllExperts.com, 2006). Therefore, a practical bridge structure needs to be lightweight to ensure an efficient safe working load is achieved. The bridge structure is used both as a load-carrying frame, but also to locate the pontoons. The secure locating of the pontoons to the bridge structure is paramount to ensure a safe design.
In designing the structure of the MFB, the design had to incorporate a centre of gravity in proportion to the stability provided by the pontoons. Without properly addressing this issue, a bridge when loaded can become unstable and unsafe due to an increase in the height of the center of gravity (Gaudron, 1999). The designs of floating bridges are generally of low modular type construction but can be as extravagant as the rolling bridge designed by Heatherwick Studio, which utilizes hydraulic rams to curl the structure (Figure 3.6).
Figure 4.6: Rolling Bridge designed by Heatherwick Studio
Geekologie (2007)
Furthermore, handrails were carefully considered for the purpose of safety. The handrails of the MFB had to supply adequate support for users in the event the structure is hit by waves or wind (Bennett, 1999). Furthermore, the handrails needed to be designed in such a way that they do not inhibit the flexibility of the structure.
1.1.3 Component Fixing Alternatives
1.1.3.1 Component Fixing Structure
After establishing all the various componentry, the next important consideration was the structure of the adjoining module. In particular, because of the cyclic and fluctuating stresses caused by the constantly changing water levels (Food and Agriculture Organization of the United Nations, 2001), special consideration had to be made for the flexibility factor to ensure brittle fracture does not occur. This consideration of environmental conditions, as well as of the loading capacities, led to the “modular design” of the MFB.
The modular design commonly seen in boat marinas (MarineTek, 2009) ensures the bridge structure has a moderate level of flexibility both in its structure and application sense. A modular design consists of a long bridge span being constructed from many smaller individual modules, which allow for flexibility at the point where they connect to one another. The modular design also has the additional benefit of its USB-like “plug-and-play” nature, which allows individual short spanning modules to be used where a long span would be impractical.
Figure 4.7: “Hot-Swap” Super-Fast Connectivity
(Scarlet Skunk Marine Services, 2009)
Furthermore, the connection of a modular design can also utilize “hot-swap” super-fast connectivity as seen in Figure 3.7, appropriate for a bridge that may need to be moved frequently, disassembled/reassembled quickly as seen in Figure 3.8.
Figure 4.8: Lacy V Murrow Bridge
(Seattle Daily Journal of Commerce, 2009)
1.1.3.2 Component Fixing Material
Note that the material used in the bridge structure would generally dictate the method of fixing components together in the bridge. For example:
1) In relation to concrete structures, methods include bracketing or bolting
2) In relation to plastic structures, methods include clipping, bracketing, or bolting
3) In relation to wooden structures, methods include dowelling, bolting, roping, or bracketing
4) In relation to metal structures, methods include welding, riveting, or bolting
Since 3.1 established the use of plastic drums, and 3.2 established the use of a wooden bridge, both (2) and (3) would be relevant. Furthermore, in order to adjoin the plastic drum and the wooden bridge, steel brackets were introduced, thus the relevance of (4) too.
1.1.4 Anchoring Alternatives
Because the bridge was likely to “float” in the middle of a vast flood of water, consideration for anchoring was required.
Traditionally, the methods used to hold bridges in place were to either:
1) Fix the bridge to a solid structure at either end as seen in Canary North Quay Bridge, West India (Figure 3.3) or;
2) To tether the bridge to pylons which are driven into the sea floor (Figure 3.4)
Unfortunately, these methods are only useful if, for (1) either there is a solid structure at the termination points of the bridge; or for (2) the bridge is not required to be removable in the case of pylon-tethered designs. Otherwise, as with the MFB, an alternative anchoring system would have to be employed.
As a result, the MFB uses “heavy weights” (conventional marine anchors), which are attached to the bridge, locked on to an area of the seabed. Furthermore, because the MFB needs to accommodate to changing water levels driven by wind and tides in large bodies of water, a special method is devised (see 5.6) to adjust for changing water levels accordingly.
1.2 Selection Analysis
1.2.1 Benefits
There are a number of benefits to the MFB bridge design, as finalized above, which makes it ideal for the communities living on and around the Tonle Sap.
1.2.1.1 Generic Parts
The componentry material is undemanding with generic parts for the construction of each section. This allows for standardized construction techniques (Berhow, 2005) to be used, which increase the economical benefits of this design by shortening the construction time needed.
1.2.1.2 Local Materials
The bridge uses materials that are easily sourced in Cambodia, including:
v Plastic drums (EWB Australia, 2009)
v Wooden decking (American University Washington D.C., 1996)
v Bamboo railings (Biodiversity International, 2009)
As discussed in 2.1.1, locally sourced materials aid in reducing the material costs due to eliminating freight and tariff charges while providing the benefits of supporting the Cambodian economy.
1.2.1.3 Entrepreneurial Design
A key feature that differentiates the MFB from its competitors is its modular sections, which are joined together to form a long structure. This allows for the easy extension or reduction in length and shape as the needs of the user change during the year. As the engineers described it, the MFB allows for “plug-and-play” and “hot-swapping” (3.3.1).
1.2.1.4 Increased Safety
The use of short bridge sections in this modular design provides additional levels of safety and flexibility when compared to a longer more rigid structure. The many joints between short sections allow for the flexibility of the structure when adverse weather conditions are experienced. In the event of a wave affecting the bridge the multiple joints allow the bridge to flex and rotate in a variety of directions increases the stability of the structure when compared to a more rigid structure.
The placement of the drums on the ends of the cross section timbers allow for an increase in stability due to the wide footprint of the bridge structure. The location of the drums helps to lower the center of gravity of the bridge, which is vital to ensuring a safe and sustainable design.
The location of the anchoring system onto the midpoint between the drums on the cross section timbers was a safety conscious decision. The location of this ensures that the structure will not heel over when subject to a disturbed water state and decreases the swaying action of the bridge much like a keel on a boat.
1.2.2 Detriments
The MFB was designed in such a way as to be superior in every manner; nevertheless, because of the restrictive financial constraints on the project, several materials were chosen for the “first-generation MFB” that could be upgraded in the likelihood of a “second-generation MFB”.
This includes:
v Cigar Design, rather than Barrel Design, which allows for increased stability and load; and
v Fiberglass Drums; rather than Recycled Plastic Drums, which allows for increased strength and buoyancy (thus load)
Nevertheless, the engineering team intends that the second-generation MFB will have full “back-compatibility”, meaning it will integrated perfectly with first-generation MFB’s, thus reducing operational redundancy.
1.3 Budget Analysis
For a project of the immense size that the MFB aimed to be, and the suitability of the project on a far smaller scale, meant that cost estimations were made based on two criteria (Taylor, 1999):
1) Precision: High level of repeatability, because if the MFB cost estimations were not precise, despite the project may be financially sustainable in the production of mass quantities, it would lack the consistency required for the production of smaller quantities of MFB’s; and
2) Accuracy: Degree of closeness to the true quantitative value, because if the MFB cost estimates were inaccurate, the project may not have the funding to properly expand, if not implemented at all
In coming up with a budget proposal, we kept in mind the following qualitative characteristics in drawing up one:
v Reliability: Synonymous with “Accuracy”, as described above; thus has representational faithfulness, and not biased;
v Consistency: Synonymous with “Precision”, as described above;
v Relevance:
- To provide a forecast of revenue and expenses, as well as assets and liabilities
- To provide a forecast of how the business may respond from certain strategies, and events (expected and unexpected)
- Have both predicative and feedback value
v Comparability: To enable actual financial operations of the business to be measured against the forecast;
v Understandability: Stakeholders, without prior accounting and engineering knowledge, can understand and apply the budget in a systematic manner. Obviously, this criterion assumes its users have a reasonable knowledge of business and economic activities and are willing to study the information with due diligence; and
v Decision Usefulness: The budget must be provided in a timely manner as so not to inhibit decision usefulness. This characteristic must be weighed up against the reliability criterion; since increased time would mean increased reliability, but may mean reduced decision usefulness.
For each independent (that is, separately funded) implementation of the MFB, there are three stages of product development:
1) Business start-up: In this period, working capital and labor service must be established. Since the bridge is Do-It-Yourself, assuming no labor costs (other than those of training staff at EWB), working capital is the predominant levy.
2) Business establishment: Once a community has established various MFB, it becomes established, and has a cash flow. Because of the franchise-nature of the MFB system, the franchisor would receive a fee, which would go towards a marketing budget. Note that economies of scale (with the exception of the steel bracket) is unlikely to be achieved because of the independent and autonomous nature of the MFB production system.
In order to increase perceived (as well as actual) professionalism, annual reports should be drawn up yearly, outlining the financial position, performance, and cash flow of each autonomous MFB system, and a consolidated report for the entire network of MFB’s (including the corporate head).
Because of the varying prices of componentry in Cambodia, the use of its own natural resources, and volatile economy, cost estimations could not be accurately provided in the design brief. Nevertheless, price minimization was the objective at every stage of analyses.
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1 Introduction
Cambodia is located across the Pacific Ocean from the West Coast of the United States of America, a bit further than Australia, as shown in Figure 1.1. It is the successor of the once powerful Hindu/Buddhist Khmer Empire between the 11th and 14th centuries (The Phnom Penh Post, 2009), but Christianity is rapidly expanding and shaping culture (Back to Jerusalem, 2006).
Figure 1.1: This is where Cambodia is located in
context of the World (University of Texas, 2009)
The Tonle Sap, Cambodian for “Large Freshwater River” (Geotimes, 2007), or “Great Lake” (Articles Base, 2009), is located in central Cambodia, and expands and contracts depending on the time of the year, as shown in Figure 1.2.
Figure 1.2: This is where the Tonle Sap is located in context
of Cambodia (Helsinki University of Technology, 2006)
Because the Tonle Sap region is susceptible to rising water levels (Food and Agriculture Organization of the United Nations, 2001), Cambodians mostly live in stilted (The Phnom Penh Post, 2009) or floating houses (Angkor Travel, 2009), predominantly travelling by boat. Figure 1.3 shows a modern-day example of a stilted house.
Figure 1.3: An example of a stilted house, from Disney’s Bridge to Terrabithia
Unfortunately, travelling in this manner restricts movement, and ultimately, geographical freedom. A modern-day equivalent would be requiring all Beverly Hills residents to use a vehicle when navigating the roadways, rather than allowing residents to walk freely through the roads. Obviously, requiring so would be somewhat limiting. The fundamental idea of a bridge was proposed to allow Cambodians to freely walk their “land”, or more semantically correct, freely “walk on water”.
As shown in Figure 1.4 however, even a Beverly Hills road is truly complex, everything from construction (Lay, 1992) to routing (Lexico Publishing Group, 2007) to transport economics (Nobel Foundation, 2000). It truly astonishing to see just how many Westerners take their roads and other civil infrastructure for granted.
Figure 1.4: A Beverly Hills road is complex in way of both design and construction.
Furthermore, unlike much of the Western World (including Venice in Europe), Cambodia faces a unique problem in relation to continuously changing water levels that differ vastly depending on season and time of year (Food and Agriculture Organization of the United Nations, 2001). In other words, the distinctive question that applied to Cambodia was what way was there to create a bridge that firstly, could stay stationary despite it was a large distance away from land; and secondly, could adjust for changing water levels.
The only solution was the Modular Floating Bridge (herein referred to as the “MFB”), which in its preliminary level has previously been used in the United States and around the World in defense, usually referred to as “pontoon bridges” (Brook, 1998). The MFB team’s task was ultimately transposing this Western idea to suit the Eastern environment that the Tonle Sap finds itself.
1.1 SWOT Analysis
The Strengths of Cambodia lies in the public perception it needs help, thus attracts attention from various agencies (Engineers Without Borders UK, 2004). Although this is counteracted by lack of access to capital (World Vision Singapore, 2007), it means that the MFB project has at least some start-up capital.
The Weaknesses of Cambodia lies in its inability to access capital, due to its bad credit rating (although slowly improving) (Monster’s and Critic’s, 2008), low aggregate country income (Bharat Book Bureau, 2005), and public perception (World Federation of Public Health Associations, 2005). Thus, the MFB budget was severely limited as a result. As a result, materials were also limited to those that were commonly available within Cambodia, rather than importing materials from overseas that would likely be comparatively more expensive, not even considering freight (ASENA Secretariat, 2009) and tariff charges (World Bank, 2008).
The Opportunities in Cambodia lie in its underdevelopment (Foundations Pour Des Actions Concretes, 2007), thus there are huge opportunities for investment in infrastructure (Government of Cambodia, 2009), which could potentially attract advertising revenue (Beyond Madison Avenue, 2008), as well as business-government partnerships (Asian Development Bank, 2005), and government funding (Economic Institute of Cambodia, 2004).
The Threats to Cambodia are that because the country is slowly gaining momentum, many companies may already be investing in Cambodia (Government of Cambodia, 2009), which could attract huge completion, which could ultimately lead to a price war (Ryckman, 1994).
1.2 Problem Definition
The problem the MFB team faced was creating a civil infrastructure, which would assist persons residing in the Tonle Sap Lake and River in Cambodia.
The proposal outlined is a response to the EWB Challenge, which hopes to help the lives of people living in poverty and disadvantage. The aim is to respond to the disadvantaged communities living on and around the Tonle Sap Lake and River in Cambodia, by presenting a sustainable human development solution (United Nations Development Program, 2007). It is truly hoped the Live & Learn and EWB community partners will find the MFB solution innovative and beneficial for new trials and pilot tests.
The various conceptual designs include an integrated design solution, including physical infrastructure, machinery, equipment and appropriate technologies. The design aims to assist Live & Learn to support the local communities in their own efforts to improve the quality of their lives from a social, environmental and economic perspective.
In short, the aim is to build a bridge that differentiates itself from the current pontoon bridges on the market because of its extendibility. Whereas current pontoon bridges are built to specific lengths, the MFB idea is to create a pontoon bridge that can be extended and shortened like the aggregating and disaggregating of Lego blocks.
MFB Design Brief by Jeremy Shum et al [2009] – Table of Content and Table of Figures {combined}
Posted on: June 6, 2009
I’m a smart duck this time! I combined the two together lol! Not that this part is important arghhh I take a long time to do things yep peoples, and I don’t know why I’m talking to myself anyway BRB!
Table of Contents
Executive Summary. ii
Letter to the Stakeholders. ii
Disclaimer v
Acknowledgments. vi
Table of Contents. viii
1 Table of Figures. x
1 Introduction. 2
1.1 SWOT Analysis. 4
1.2 Problem Definition. 4
2 Background. 7
2.1 Political 7
2.1.1 Increasing Use of Own Resources. 7
2.1.2 Dealing with Misappropriation. 7
2.2 Economic. 8
2.2.1 Access to Debt Finance. 8
2.2.2 Benefits to Industry. 8
2.2.3 Benefits to Community. 9
2.3 Social 9
2.3.1 “Free Lunch”. 9
2.3.2 Population Growth. 9
2.3.3 Culture. 10
2.4 Technological 10
2.5 Legal 11
2.6 Environmental 11
2.6.1 Climate Weather 11
3 Conceptual Design. 14
4 Design Analysis. 17
4.1 Alternative Analysis. 17
4.1.1 Pontoon Alternatives. 17
4.1.2 Bridge Alternatives. 21
4.1.3 Component Fixing Alternatives. 22
4.1.4 Anchoring Alternatives. 23
4.2 Selection Analysis. 24
4.2.1 Benefits. 24
4.2.2 Detriments. 25
4.3 Budget Analysis. 26
5 Final Design. 29
5.1 Polyethylene (Plastic) Drums. 29
5.2 Steel Brackets. 30
5.3 4”x6” Timbers. 31
5.4 Wooden Decking. 33
5.4.1 Extension Pieces. 34
5.4.2 “Branching” Pieces. 36
5.5 Handrails. 37
5.6 Anchoring. 37
6 Sustainability & Maintenance. 40
6.1 Environmental Impact of Materials. 40
6.1.1 Timber and Deforestation. 40
6.1.2 Marine Impacts. 40
6.2 Sustainability of Materials. 41
6.2.2 Disposal 43
6.3 Maintenance Strategy. 43
6.3.1 Inspection Methodology. 43
6.3.2 Special Maintenance Considerations for Susceptible Componentry. 45
6.4 Ethics. 46
7 Implementation Strategy. 48
7.1 Stakeholder and Customer Communications. 48
7.1.1 Marketing Mix. 48
7.2 Infrastructure Preparation. 52
7.3 Manufacturing Roll-Out 52
7.3.1 Quantity of Production. 52
7.4 Training. 52
7.5 Change Management 53
7.6 Problem Resolution. 54
8 Conclusion. 56
9 References. 57
1 Table of Figures
Figure 1.1: This is where Cambodia is located in context of the World (University of Texas, 2009) 2
Figure 1.2: This is where the Tonle Sap is located in context of Cambodia (Helsinki University of Technology, 2006) 2
Figure 1.3: An example of a stilted house, from Disney’s Bridge to Terrabithia. 3
Figure 1.4: A Beverly Hills road is complex in way of both design and construction. 3
Figure 2.1: For the same Supply curve, if the Demand of Cambodian wood increases, the price will increase, thus deterring “exploit” pricing of Cambodian wood. 7
Figure 4.1: Poly Drum (ADCO Services, 2003) 17
Figure 4.2: Steel Drum (Global Industrial, 2009) 18
Figure 4.3: Canary North Quay Bridge, West India (Darkwaters, 2009) 18
Figure 4.4: Vera Katz Eastbank Esplanade and Floating Bridge (Bridge Stories, 2009) 19
Figure 4.5: Vera Katz Eastbank Esplanade and Floating Bridge (Bridge Stories, 2009) 21
Figure 4.6: Rolling Bridge designed by Heatherwick Studio Geekologie (2007) 22
Figure 4.7: “Hot-Swap” Super-Fast Connectivity (Scarlet Skunk Marine Services, 2009) 23
Figure 4.8: Lacy V Murrow Bridge (Seattle Daily Journal of Commerce, 2009) 23
Figure 5.1: Artist’s Visualization of a Polyethylene Drum.. 30
Figure 5.2: Artist’s Visualization of a Modified Bracket 30
Figure 5.3: Artist’s Visualization of a Drum Assembly. 31
Figure 5.4: Artist’s Visualization of a 4”x6” Timber 31
Figure 5.5: Artist’s Visualization of how a Timber fits into a Bracketed Drum.. 32
Figure 5.6: Artist’s Visualization of a notched timber section. 33
Figure 5.7: Artist’s Visualization of an assembly bridge module. 33
Figure 5.8: Artist’s Visualization of a wooden decking. 34
Figure 5.9: Artist’s Visualization of an assembly decking onto bridge module. 34
Figure 5.10: Artist’s Visualization of an extension piece (note wider decking is the only modification) 35
Figure 5.11: Artist’s Visualization of an extension piece and a standard piece interoperating. 36
Figure 5.12: Artist’s Visualization of a bridge branch piece. 37
Figure 5.13: Artist’s Visualization of how the Bridge reacts to changing water levels. 38
Figure 7.1: Advertising Bridge by Sihun Highway (Huajian Rice Industry, 2007) 50
Figure 7.2: Users know they are buying “quality” when they spot the Hewlett Packard “HP” Brand As a result, bridges manufactured by “mfb” can be separately identified by that of a non-branded, non-certified nature. In some ways, the culture, as well as entrepreneurial ship in MFB bridges could be reflected in other aspects of business in Cambodia as a result. 51
Figure 7.3: Bridge on Tonle Sap (TravelPod, 2009) 54
jenna.butterfly.welcome 