Aluminum: A Sustainable Structural Choice

Celeste Allen Novak, AIA, LEED AP

For more information, please visit ce certification space frame.

Continuing Education

Use the following learning objectives to focus your study while reading this month’s Continuing Education article.

Learning Objectives - After reading this article, you will be able to:

1. Discuss the efficiency of using lightweight, recyclable aluminum in clear-span structures by eliminating secondary structural members.
2. Compare how aluminum is an efficient, waste reducing alternative to steel in overhead, sloped and vertical applications.
3. Avoid maintenance and life cycle costs by specifying a product that is durable and resists corrosion.
4. Explore case studies of geometric structural designs used for lattice and spaceframe aluminum structures that have received green building certifications.
5. Summarize the commitment by the aluminum industry to improve industry energy consumption, lower emissions, minimize land resource use and maximize sustainability.

Lamella geometries allow for the design of very large structures minimizing the amount of material necessary for the forms. The properties of aluminum made this large structure possible as the focal point for the Shanghai Scienceland Museum.

Latticed, tubed, segmented, half-domed, the promise of spatial geometries that emulated nature began well before Buckminster Fuller popularized one of the first geodesic domes, a spaceframe, a half century ago. Today’s architects are continuing to explore geometric forms and are finding that aluminum is a material that meets both structural as well as sustainable goals. “I‘ve never met an architect who doesn’t love geometry,” spoke Grace Ferretti, Manager of Architectural Division of CST Covers when discussing the sustainability of using aluminum for long span structures and spaceframes. Technology and computers are allowing architects freedom to span ever larger areas with more efficient structural components. Virtually any shape or form can be designed using an aluminum structural or spaceframe system. The only limitation is the designer’s imagination. Aluminum is strong, lightweight and a resilient material. It combines strength with flexibility and can flex under loads or spring back from the shock of an impact. Around the world aluminum is becoming the choice for long span structures over steel frames for many reasons including the many environmental benefits of its materials footprint. 

This article will explore the uses of aluminum in long span structures and spaceframes. It will also review the latest research by the Aluminum Association on the sustainability of aluminum from mining to recycling. This industry is committed to improve industry energy consumption, lower emissions, minimize land resource use and maximize sustainability. The projects highlighted in this article include projects that range from the largest Platinum LEED®-NC campus to the newest aluminum solar “trees” to be planted in parking lots as a high tech energy and water collection system.

Sustainability has many aspects and design professionals are working to improve the cost to the environment with better material choices. The international and national aluminum industry is helping this movement by providing research on the sustainability of aluminum from mining to manufacturing. From documenting recycled content to initiating a soon to be released life-cycle analysis the Aluminum industry is becoming a leader in sustainable mining and manufacturing processes.

Photo courtesy CST COVERS

The benefits of aluminum as an environmental choice are based on its intrinsic properties as an alloy that maintains strength. Social, economic and environmental goals are three principle goals for sustainability. As discussed later in this article, the international community is providing incentives for mining practices that promote best practices around the world. Environmentally, aluminum has a high recycled content and can be recycled. Aluminum is durable and long lasting. Aluminum meets economic goals because of its higher strength-to- weight ratio than most other metals or materials. Aluminum is one of the most efficient structural materials providing the same strength than steel at less than one-third the weight. This reduces the project material costs associated transportation costs and reduces the overall costs through the adaptation of a multitude of installation methodologies. Design professionals who choose this building material will be able to achieve many of their goals for sustainable buildings.

Intrinsic Benefits — Aluminum and Sustainability

Re-cycle and Re-Use

“There is recycled content in almost all aluminum products” according to Charles Johnson VP, EH&S of the Aluminum Association. Aluminum that was produced and recycled in the last century is still in use in buildings, containers and automobiles. In 2008, a survey of all aluminum producers indicated that the “total recycled content of domestically produced, flat rolled products for the building and construction market was approximately 85 percent. This industry survey of aluminum producers also indicated that on average, approximately sixty percent of the total product content is from post-consumer sources.”1 Individual producers may have higher post-consumer totals and total recycled content of the material is available for use with green building credits.

The composite of recycled and new aluminum has grown to be averaged at almost seventy-five percent recycled content in all aluminum products. Architects calculating USGBC LEED® certification points can count on obtaining at least one if not more points for recycled content, Material and Resources Credit MR 4.1 and 4.2. If the value of the recycled content is at least ten percent of the cost of the materials, the project will earn one LEED® point. If the recycled material value reaches twenty percent, it will earn another point. Aluminum extruders are currently producing materials with a seventy percent recycled content or greater and most fabricators should be able to provide documentation as required for green rating systems. 

The recycled content depends on where and when the raw materials are available. An aluminum product that is manufactured to a specific strength when recycled maintains its properties and can be reused again for structural purposes. Aluminum is sustainable in that it can both be recycled and re-used without any loss of strength. The market for aluminum, particularly recycled aluminum is booming and the aluminum industry is encouraging product designers to think about disassembly of components while designing for structural assembly of new buildings. Aluminum is very long lasting as a durable material as it is non-corrosive and will not degrade due to moisture, condensation, rust or salt-ladened air. The aluminum industry is currently developing an extensive study of life-cycle costs to document the longevity of aluminum as a sustainable product in any climate and for most products.

Photo courtesy CST COVERS

The Shanghai Scienceland Museum's egg-shaped atrium is constructed of sustainable, structural aluminum with recycled content.

Reduce

Architects are utilizing aluminum over steel for clear span applications because it is lightweight, corrosion resistant, extrudable into many custom forms, can be assembled and erected on difficult sites and is a sustainable material. Aluminum can also be designed for disassembly for future use in new projects.

Lightweight aluminum structures can weigh anywhere from 35 percent to as much as 80 percent less than steel, yet provide equivalent strength. Because aluminum is extrudable, it can be designed to put the material only where it is structurally required. Custom extrusions are designed per project allowing the minimal use of the metal and reducing overall costs and raw material use. These extrusions greatly eliminate the fabrication required to create the structural shape. The overall reduced weight of the structure enables efficient assembly, reduced transportation and additional savings on construction.

Although often considered a more expensive alternative to steel, in case after case, design professionals are finding that the costs are equal or less when specifying aluminum for major structural systems. Redundant secondary framing is unnecessary with efficient geometry creation as the structural shell system. This lightweight material can be shipped as components to be assembled on site without a crane. Aluminum structures are assembled with bolted connections and there is no welding required in the field. The connections are designed to accommodate the intersection of several members facilitating the ease of joining members together.

Aluminum is also easy to shape, extrude and machine into many types of structural components. Aluminum extrusions are fabricated with dies that can increase the thickness of the members where they are needed and decrease it where it is not needed while maintaining structural integrity. “Putting the metal where it is needed is one of the great advantages of aluminum as a material. The efficient use of materials results in lower cost structures,” notes CST Cover’s Ferretti as she comments on the diverse uses of this twentieth-century structural product.

Most window extrusions for commercial properties are made from aluminum. By using custom structural aluminum framing, adding skylights, windows, sun shading and solar panels are integral to the structure. Using aluminum eliminates dissimilar expansion and contraction rates of different materials. Complex shapes can be produced in one-piece extrusions without using mechanical fasteners. One-piece extrusions are less likely to fail, leak or loosen over time and are ideal for integrated system design.

An additional savings to labor and materials is the ability of aluminum to be used with a mill finish. Aluminum naturally generates a protective oxide coating providing a finish that is durable, corrosion resistant and aesthetically pleasing. Using a mill finish can also expedite delivery. Other environmentally friendly finishes that are chosen for appearance can also be applied. Finishes vary from mill finish to highly polished finishes and include sandblasting, anodizing, specialty coatings, paints and powder coatings.

MATERIAL RESEARCH: LONG SPANS, SALT AIR, AND FAST TRACK

Photo courtesy CST COVERS

The aluminum canopies over KAUST university walkways provide filtered light, encourages natural ventilation and adds to the cultural context of the designs.

According to Ed Abboud, P.E., Director of Structural Engineering at HOK, in the past, the majority of spaceframes have been constructed of steel rather than aluminum. However, when HOK researched a solution for the main gathering space at The King Abdullah University of Science and Technology (KAUST) in Jeddah, Saudi Arabia, aluminum was the obvious choice for this unique long span spaceframe.

HOK is a global architectural firm with an integrated approach to architecture. Their sustainable practice designs reflect their knowledge of technology and the use of natural systems to achieve results. One of their latest projects, one of eight in the past eleven years, to be awarded a “Top Ten Project” by the AIA Committee On The Environment (COTE) is King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia.

To meet a very short design and construction budget, HOK engaged their eleven offices across three continents to complete this massive six and one-half million – square – foot campus in three years. Multiple HOK design teams worldwide worked in tandem to integrate sustainability into the design and construction of the world-class twenty-six building campus. Several hundred HOK people in eleven different offices on three continents contributed to the ambitious project, which was delivered within an unprecedented schedule — from conception to completion in just three years.

Designed for a hot, desert climate and on the banks of the Jordan River, the HOK Planning Group began this project thinking about the environment with a “Racing the Sun” charrette. Planners from multiple offices and in many time zones contributed designs to a web server that were then incorporated into the final plans for the complex. They used environmental strategies from regional and traditional cultural designs as well as explored the translations of these concepts with the use of new technology and materials.

These elements included the massing of the buildings in a compressed area to reduce building envelope exposure and increase shading for natural cooling of the walkways laid out like a traditional “souk” or marketplace. They conceived of a monumental canopy that would span across buildings to block the sun, facilitate natural ventilation and to filter light. This canopy would also be the platform for solar panels that provides power to the facilities. These long spans were exposed to the elements. The salt air of this site on the banks of the Red Sea, near Jeddah, created a highly corrosive environment for this structure. According to Ed Abboud, HOK’s Director of Structural Engineering, P.E. the commitment to a product begins with research. 

The client recommended a steel spaceframe for this large clear span structure; however, HOK was uncomfortable with the weight of steel and durability in this corrosive environment. The soft soil and fast track construction required them to find a lighter, less massive solution for the problem. According to Abboud, the team showed the client “galvanized steel air-handlers that showed signs of corrosion in nearby structures as an example of their concerns.” Convinced, the client travelled with them to investigate the possibilities of using aluminum as an alternative material instead of steel for these large spaceframes.

The research team investigated numerous aluminum spaceframes across the world, ultimately selecting a company that would work with the designers to create the large spans with the least amount of materials. There is over 200,000 SF of aluminum spaceframe on this project. Typically, the depth of a standard spaceframe is normally seventy percent of the module size to create strut lengths of identical size in the upper diagonal and lower chords. For example a 10’ x 10’ module would have a depth of 7’.  This project was limited to a depth of 3’ – 3” (1 meter) and a depth of forty percent of the module size, to keep the structures as shallow and lightweight as possible. Aluminum trusses were also used in some areas, spanning seventy-five feet between buildings. Site restrictions and the ability to get cranes between two buildings caused the team to choose trusses instead of spaceframes for some locations.

The custom designed connectors or nodes of the spaceframe are variable but some are as large as 14” in diameter. In comparison, a standard node is usually 4.5” in diameter. The nodes were sheared off to provide a flat surface to accept the glass cladding system and to minimize the depth of the structure. The same detail for the nodes were used at the bottom of the frame to allow for the aluminum perforated panel system that let in filtered light to the walkways below. There are over 18,000 struts and 4,600 hubs on the job that were fabricated and shipped to the site in less than nine months. The structure was provided in a mill finish to expedite delivery and ultimately reduce overall costs. The project schedule on the aluminum structural elements for this project was less than nine months for the design, fabrication and shipping.

Photo courtesy of XX PHOTO

A view of the large flattened aluminum nodes of the spaceframe at KAUST.

The frames were fabricated in Houston and shipped to Arabia where they were lifted into place after assembly on site. Strong, durable, lightweight aluminum was chosen for this main element at KAUST which is the largest Platinum LEED®-NC project in the world.

Using a combination of passive solar strategies such as orientation, shading and natural ventilation with a high level of technological expertise, HOK was able to design a project that delivers a high level of environmental performance.2 These include in the areas of water (100 percent wastewater reuse, 42 percent water reduction), energy (27.1 percent annual energy cost savings, 7.8 percent on-site renewable energy, 80% of glazing shaded year-round) and materials (20 percent recycled content, 38 percent regional materials, 99 percent wood from Forest Stewardship Council sources, 80 percent construction waste management). These large aluminum canopies form the character of the campus. The roof vaults are an example of well researched integrated design strategy that encourages passive cooling and natural ventilation while reducing the heating and air-conditioning loads by the design of an environmentally responsible aluminum structure.

Geometry — Using Less Structure but Getting More

Clear span structures are possible with efficient geometric configurations. Architects have been challenged to cover the largest space possible with the least amount of material for centuries. Geometry principles from the Pythagorean theorem to Euclidian math have been the basis for their exploration and structural calculations of physical forms. Architects and engineers have been able to span ever-larger distances without columns using basic geometric principles. They balance the weight of physical members and environmental loads by spreading the loads across numerous members. Reducing the weight of the structure without losing the strength of the members by means of efficient geometries allows designers to use less metal in their structures. With the advent of computer modeling, new geometric forms are becoming even more viable. With the use of aluminum, large structures using complex geometric forms are lighter, stronger and can span greater area.

Photo courtesy CST COVERS

This large, enclosed, trapezoidal aluminum truss has a span of 135 feet at one end and 106 feet at the other, definitely making a statement about the power of engineering at the entry Lockheed Martin Aeronautics in Fort Worth, Texas.

Aluminum Lattice Spaceframes and Trapezoidal Designs

Spaceframes became popular in the seventies and are made up of a series of struts and nodes creating triangulation in each face. Spaceframes can work with and without curvature. Based on the geometry of crystals, with repeating units of structure, lattice designs are widely used to create unique structural solutions. Geometric framing configurations can be developed by using standard three dimensional spaceframe framing, a single layer lattice or reinforced stiffened shells and a combination of a single layer grid reinforced structurally by three dimensional trussing. Although one might assume that these structures are envisioned by computer modeling. In fact, many architects sketch their designs for the fabricator who then develops the intricate geometry to meet the necessary structural requirements.

A single-layer lamella enclosure in Shanghai is shaped like a very large egg that contains the planets in the universe. It spans one hundred and sixty feet and it is thirty feet high and hundred and ten feet at its widest point. This canopy has no columns or sub-steel framing. It is made of three types of ten-foot long aluminum extrusions. A lamella structure is a domed structure that can be created by forming a network of perpendicular ribs that appear to be diagonal in plan. The advantages of this type of geometry “– in addition to an economy of materials — is the use of the repetition of similar elements and joint details. Another advantage is in the use of straight linear elements to produce the curved vaulted surface.”3 Working with the fabricator, this egg-shaped dome was made possible only because the metal was designed where it was needed saving material and installation costs.

Photo courtesy of Bob Braun

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The mill finish aluminum spaceframe over the Lynx Bus Station in Orlando, Florida spans 88,000 SF designed by Helman Hurley Charvat Peacock Architects is curved to represent movement.

The space frame for the Lynx Bus station in Orlando, Florida is an example of a curved, trapezoidal structure that has thirty-three different radii and covers eighty-eight thousand square feet. The architect chose mill finish aluminum due to the cost savings. A mill finish product will not rust and corrode and does not require a paint coating or chemical to maintain its structural integrity.  This project was bid out for pricing both as a steel structure versus aluminum structure and in comparison, the aluminum structure was almost two million dollars lower in cost than steel.

Custom Truss Designs

As discussed in the KAUST case study, in some cases, aluminum is designed as a long span truss. For a project in Sea World, a series of aluminum spaceframes and trusses were combined to provide supporting equipment over the aquatic area. These custom trusses carry the weight and flexible loading of SeaWorld’s acrobatic performers. Aluminum was selected specifically for this project because of its non-corrosive properties in a salt-water environment. Aquatic life is sensitive to impurities in the water and using aluminum eliminated the concern for corroding metal leaching into the tanks.

The Lockheed Martin Gate in Fort Worth, Texas is a large trapezoidal structure with a span of 135 feet at one end and 106 feet at the other. It arches 30 feet to cover the entryway. The original concept drawing was designed as a structure only four feet deep. To incorporate additional maintenance access the truss was increased to 5 feet in depth. The designer was able to eliminate secondary steel and concrete support framing because of the strength of the aluminum and the geometry of the design. The truss is clad with aluminum panels and all exposed materials were painted with a Kynar finish. The interior trusses have the original mill finish. With aluminum trusses you eliminate the possibility for corrosion from simple condensation that would normally occur in this hot humid climate with a steel framed structure. This is particularly important, as the trusses in this design are fully enclosed and not easily visible or accessible for maintenance.

Hyperbolic Structures

Photo courtesy of CST COVERS

James B. Walters, Design Engineer, rendered this concept model of a fast train station in Taiwan. Although it appears to be a large glass curved structure, only the gusset plates are curved in this hyperbolic structure. The glass lites are flat, segmented panels and are identical in size reducing the fabrication and material cost for the project.

Using segmentation, designers can give the look of curved members to a large glass enclosure without adding cost. On a single-layer moment connected frame, beams come together and are fastened to gusset plates, one on the top and one on the bottom. The gusset plates are the only curved members – dished to accept the members properly. In most curved profiles, the plates are either concave or convex in shape creating curvature. In a hyperbolic structure, a professional can limit the number of identical glass panels to control costs.

Single Layer Aluminum Tubes

Photo courtesy of CST COVERS

Utilizing structural aluminum tubes, this curved entry canopy is only six inches deep. Curvature can eliminate the need for three dimensional framing, as shown here. It is fifty feet wide and thirty feet deep and the design can support the required 160 PSF snow load.

Aluminum can also be used in smaller span structures, as it allows for cantilevers and extensions of the material that would not be possible with a heavier structure. skylights can be designed using a single layer aluminum tubes without the need for steel sub-frames. Utilizing structural aluminum tubes, this curved entry canopy in Eau Claire, Wisconsin is only six inches deep. It is fifty feet wide and thirty feet deep and the design can support the required 160 PSF snow load.

Photo courtesy of R. Greg Hursley

These large botanical spaces designed by Emilio Ambasz are clad with large glass panels connected directly to the structural members by use of an aluminum purlin system.

Custom Nodes and Cladding Materials

The design of a space frame and its components includes the connectors or nodes that are used to join members and designed to carry loads. These connectors can be shaped to fit almost any profile. For example, a linear node system will allow the space frame to have a very flat structure that can be used both in an overhead or vertical wall system. Custom extrusions with rigid joints, tubular members and small node connectors can also allow glass to be flush mounted. Design professionals should consult aluminum fabricators at initial design phases. Fabricators can propose a variety of structural configurations and analyze the most efficient connections and structural forms to achieve the best sustainable design solution.

Aluminum structural systems are designed to support any cladding system available in the market. As seen in the large botanical spaces designed by Emilio Ambasz (The Lucille Halsell Conservatory at the San Antonio Botanical Gardens), spaceframes can be clad with large glass panels connected directly to the structural members by use of an aluminum purlin system. This structure encloses an environment which is high in humidity. The plants are misted daily. The advantage of the aluminum frame is that it will not corrode and maintains its appearance. Aluminum can also be clad in translucent panels or engineered to receive tension fabrics. Aluminum structures are the clear choice for designers engineering solar panels to clad roofs, walls and freestanding solar systems.

SOLAR CARPORTS TAKE ADVANTAGE OF ALUMINUM PROPERTIES

Photo courtesy of WATTLOTS, Inc.

Organic long solar beams carry curved solar panels that track the sun in this aluminum Power Arbor at a corporate campus by WATTLOTS, Inc.

When architect William Kaufman, AIA, president of WATTLOTS Inc. describes his new product, he talks about biomimetric inspirations. These solar “trees” can be planted in parking lots as arbors to reduce heat island effect while collecting solar power to be added to the grid. His design is “an exercise in biomimicry, the structures perform intellectually like trees, the light is not fully blocked and rainwater is collected at their bases. They are like a trellis growing from a root system.” These long, thin, solar beams track the sun and were designed to meet strict aesthetic requirements.  These new solar carports take advantage of the unused real estate in parking lots, providing new uses and other sources of parking lot revenue. They are not only solar and collectors, but also vehicle recharge stations. In addition, they can be used for advertising and part of a communication system.

Kaufman chose aluminum as his design material because it provided him with many sustainable features. He was able to integrate into a lightweight extruded aluminum frame a panel that holds the solar cells as well as integrate the micro-inverter and wiring into a chamber for electronic equipment. These modules are designed as eighteen feet long beams placed parallel to one another in segments. The strength of aluminum allowed all of the loads to be carried to one central base where a mechanism drives the rotation of the beams toward the sun. Using aluminum allowed for a high level of recycled content. Corrosion resistant, the aluminum frames are durable. The flexibility of aluminum and its extrudability allowed the designer to create the organic forms desired. The connections make the system easy to assemble and disassemble and at the end of its life will be able to be recycled and repurposed into a new use without a loss of strength from the original material.

In addition to the solar carports, Kaufman also has designed a solar wall system that also uses the advantages of aluminum as a material. The solar wall system is an identical product without the tracking system. The long thin one-foot, slightly curved panels are placed on the South-facing facade and are fully integrated into the building envelope. They act as shading fins and are tilted to the appropriate site solar aspect. They shed snow and water from one to the other, and act as fins or solar shingles across the building. These solar panels provide new opportunities for the facades of numerous windowless environments: parking garages, warehouses and big box stores. The aluminum extrusions are lightweight, carry the appropriate loads and create a productive use for otherwise lost building area.

Photo courtesy of WATTLOTS, Inc.

Solar shingles are added to this building in this WATTwalls warehouse application concept image. Panels will generate power that can be used by the building or sent back to the electrical grid.

Sustainability — Industry Research

In September 2011, the Aluminum Association published “Aluminum: The Element of Sustainability” developed by its sustainability group to document the industry’s sustainability achievements over the past two decades. The research also offers a broad overview of the use-phase achievements of aluminum as a sustainable material. Using a life-cycle approach, the report investigates the overall costs and benefits to society of aluminum as a sustainable material. From resource extraction to recycling of a finished product, the report includes charts, tables and comparisons that document the commitment and progress of the North American Aluminum Industry toward sustainable initiatives. 

Among the findings of the report, “Aluminum: The Element of Sustainability,”4 are that since 1991:

• Primary energy demand associated with primary aluminum production has been reduced 17 percent
• Primary energy demand associated with secondary aluminum production has been reduced 58 percent
• Cumulative greenhouse gas emissions associated with primary aluminum production have been reduced 72 percent
• Cumulative greenhouse gas emissions associated with secondary aluminum production have been reduced 65 percent

This well-documented report quantifies aluminum’s sustainability contributions during the product and end-of-life phases. The Aluminum Association is continuing its research on the life-cycle assessment of semi-fabricated building products that it hopes to publish in the next year.

Aluminum is the third most abundant element on the planet. In the late 1800’s Charles Martin Hall discovered a method to process aluminum using an electrolic process that made aluminum a viable commercial metal. Because aluminum does not lose strength or durability, nearly 75 percent of the aluminum produced then is still in use today. Aluminum has extraordinary value as a building material. When mixed with small amounts of other elements, aluminum can be processed, cast, forged, rolled or extruded into numerous structural forms. It is lightweight and provides the strength of steel at a third to half the weight. Aluminum structural members can span longer distances with smaller profiles. Aluminum does not rust and is corrosion resistant providing a natural oxide coating as a protection against degradation from water, salt, air and temperature variation. According to the sustainability report, “once manufactured, aluminum can be recycled repeatedly, using only five percent of the energy and generating only five percent of the emissions associated with primary production.”5

SPECIFYING A SERIES: ALUMINUM ALLOYS

The American National Standard Institute (ANSI) numbering system is used to classify aluminum alloys. An alloy is a combination of pure metals that when combined create an interstitial bond between the elements producing strength and in this case, resistance to corrosion. ANSI numbers describe the tensile strength, corrosion resistance and workability of aluminum. There are different numbering systems for wrought and cast aluminum products than there are for architectural aluminum. The amount of magnesium added to the aluminum will change the series number for the product and denote varying degrees of corrosion resistance and strength. The most common series of aluminum specified for use in long span structures are numbered between 5000 and 7000 (the strongest alloy). Structural systems generally use 6061 – T6 alloy.

 

Advances in Resource Extraction and Rehabilitation

In addition to the Aluminum Association reviewing the sustainability practices of it as an industry, the International Aluminium Institute released its Fourth Sustainable Bauxite Mining Report: IV 2008. Aluminum is one of the most abundant metallic elements in the world, the third most abundant of all elements after oxygen and silicon. The industry estimates the aluminum reserves to be able to supply another three hundred years. Most aluminum is a combination of hydroxides and bauxite minerals. Gibbsite, Boehmite and Diaspora are the base raw material for primary aluminum production created as part of a weathering product of low iron and silica bedrock in tropical climatic conditions. The industry has been surveying sustainability and mining practices since 1991. Survey data for the 2006 report covered 66 percent of all major bauxite-mining operations and the 2008 report shows continued substantial improvements in the environmental performance of the industry. 

Bauxite mining requires a small amount of energy when compared to the energy needed to refine aluminum. Diesel fuel (69 percent) and fuel oil (24 percent) are the primary use of energy. Mining operators have adopted several strategies to reduce energy consumption. They have purchased more efficient equipment and trucks, improved the maintenance of vehicles and reduced hauling distances. They have also changed to natural gas where possible from fuel oil as an energy source.

According to this research bauxite mining has a relatively small footprint in comparison to other types of mining. The land area used for Bauxite Mining in 2006 is half the size of Manhattan Island and the industry research shows that the amount of mined area is now equivalent to the amount of rehabilitated area demonstrating a  “land neutral footprint” to Bauxite mining operations. “Reporting mines have plans to rehabilitate more than 90 percent of the total area that was used for bauxite mining and infrastructure since operations commenced almost seventy years ago.”

The rehabilitation objectives can be summarized as follows: “The bauxite mining operations aim to restore pre-mining environment and the respective conditions; this can be a self-sustaining ecosystem consisting of native flora and fauna or any other land-use to the benefit of the local community.”6 Environmental management planning is based on local, national and international standards, practices as well as community expectations.

The respondents to the survey engage an average of twenty-one full time rehabilitation and environmental experts ranging from soil scientists to botanists to provide expertise toward best practice reclamation of mined areas. According to the survey, mining operations generated net social benefits that included:

• Paid employment under conditions that complied with accepted local labor standards. 75 percent of the total surveyed paid wages at the mines equal to or higher than the national wage average.
• Education and training programs for employees.
• Development of local industries and businesses.
• Support of community initiatives and social activities.
• Investment in infrastructure.
• Provision of health and sanitation programs that include malaria prevention and vaccinations.

Approximately 60 percent of the entire workforce is recruited locally. Only three of the fourteen companies surveyed reported any displacement of citizens. Most bauxite operations occur in areas of the world with low density. All of these companies have resettlement programs. Almost eighty percent of the surveyed mines are ISO 14001 certified for environmental management. The International Aluminium Industry (in 1925, the American Chemical Society changed the spelling to Aluminum, and both spellings are in use today) is a strong proponent of sustainable initiatives and continues to document progress by its members for best environmental practices.

Photo courtesy of CST COVERS

Aluminum frame for large solar collector in Arizona.

Engineering, Design and Environmental Benefits

Not every aluminum system will work on every project. The key to engineering and designing aluminum structures is the early involvement of the fabricator. Typical engineering services include preliminary models, renderings, calculations of the reaction loads, etc. In many instances, the fabricator will provide value-engineering services providing insights to the architect as to how to reduce the members of the structural system without impeding the design intent. Sometimes a change as simple as slightly increasing the modular grid to maximize the spanning capacity of the cladding materials can reduce the amount of structure, use less materials, finishes and decrease the cost of the overall structure.

To summarize, the sustainable advantages of aluminum are many and include the following environmental benefits.

• Design of lightweight clear-span structures that are easy to assemble. 
• Creation of open and column free flexible spaces that maximize daylight transmittance.
• Strength to weight ratios that will not decrease when aluminum is recycled into new products.
• Effective use of geometric properties to reduce material waste.
• Elimination of secondary framing members.
• Reduction of maintenance and increase in longevity because of the non-corrosive properties of aluminum.

The use of aluminum is increasing throughout the world for many uses. It is ideal for beverage containers and has contributed to the reduction of emissions and transportation costs as a component in automobile manufacturing. As a building material, aluminum provides many benefits to the designer, particularly the designer who uses geometry as a design element. Choosing aluminum as the structure for these new geometric forms and spaceframes reduces material consumption and has numerous environmental benefits. As more and more designers learn how to design for disassembly, aluminum products will continue to evolve and be re-used for centuries as a sustainable, durable building material.

 

Architect Celeste Allen Novak AIA, LEED AP specializes in sustainable design and planning in Ann Arbor, Michigan.

CST Covers is a global design/build firm with expertise in high-strength aluminum signature solutions such as spaceframes, domes, environmental enclosures, canopies, large span, and specialty lightweight structures designed for unique eco-friendly vertical and overhead applications.  www.cstcovers.com

 

Sparkymark said:

Hi all.
How important is the CE mark on sheds?
If i have to get planning permission to put a steel framed shed up does the resulting shed need a CE mark on it or can i make it myself with the help of a welder?
And if i built it myself would it qualify for insurance cover etc?

Click to expand...

If you are going to make it yourself get a design done on it from a structural engineer this will give you all the correct size steels and a bracing layout and connection details, maybe £200 would cover this if you are costal or in an elevated position make sure this is covered if you buy a generic design,as for the steel you should not be able to buy non ce marked steel stock, the differences people refer to in steel from the past could be the fact it was common to have different grades 43a and 50b or S235 and S355 but most only stock the higher grade now, as far as i am aware you can make it yourself if its a one off design and not a series production run but i would get the design done if i was you but watch the prices as they can vary massive some will want to charge you £1k +

If you are going to make it yourself get a design done on it from a structural engineer this will give you all the correct size steels and a bracing layout and connection details, maybe £200 would cover this if you are costal or in an elevated position make sure this is covered if you buy a generic design,as for the steel you should not be able to buy non ce marked steel stock, the differences people refer to in steel from the past could be the fact it was common to have different grades 43a and 50b or S235 and S355 but most only stock the higher grade now, as far as i am aware you can make it yourself if its a one off design and not a series production run but i would get the design done if i was you but watch the prices as they can vary massive some will want to charge you £1k +

If you are looking for more details, kindly visit types of space truss.