Building Technology - Dome Structures

10/6/2010

GROUP 8: DOME STRUCTURES

BAROA, FRANZE EMMANUELLE C. GUTIERREZ, MARLIN NOAH P. MENDOZA, ROBIEWILL B. PIEDAD, CHRISTINE JESUSA R. RETERACION, REYMOND S. BS ARCH IV-3D

ARCH. NOEL DOMINGO| neo Group 8 – Dome Structures [10.06.10]

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Outline: I. II. III. IV.

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VI. VII.

VIII. IX.

INTRODUCTION DEFINITON AND BRIEF HISTORY DOME BASICS DIFFERENT TYPES OF DOME STRUCTURES A. GEODESIC B. MONOLITHIC C. ECO-DOME DIFFERENT CONSTRUCTION TECHNIQUES OF GEODESIC DOMES A. FLATTENED CONDUIT B. TUBE AND HUB C. BEAM AND HUB D. PANELIZED TIMBER FRAME E. STRESSED SKIN F. MONOLITHIC G. SPACE FRAME H. BRICK AND FORMER I. FOAM AND RENDER DOME CONSTRUCTION PROCESS (DOME TECHNOLOGY) TECHNOLOGY / APPLICATIONS A. COATING B. RECLAIM SYSTEMS C. DRIVE-THROUGH DOMES D. TUNNEL TECHNOLOGY SAMPLE DETAILS REFERENCES

Group 8 – Dome Structures [10.06.10]

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INTRODUCTION Domes have been popular in the construction of buildings since ancient times. This particular design has the important characteristic of withstanding adverse climatic conditions such as earthquakes, tornadoes, floods, hurricanes, or even tropical storms. Earlier domes were used only in religious buildings, however its usage has now been seen in constructing residence buildings as well. Houses with dome construction are usually found in regions which experience heavy winds and extreme climatic conditions. The trend is speedily catching up in constructing residential buildings and public structures such as schools and colleges.

BRIEF DEFINITION AND HISTORY A dome is a structural element of architecture that resembles the hollow upper half of a sphere. Dome structures made of various materials have a long architectural lineage extending into prehistory. Corbel domes have been found in the ancient Middle East in modest buildings and tombs. The construction of technically advanced large-scale true domes began in the Roman Architectural Revolution, when they were frequently used by the Romans to shape large interior spaces of temples and public buildings, such as the Pantheon. This tradition continued unabated after the adoption of Christianity in the Byzantine (East Roman) religious and secular architecture, culminating in the revolutionary pendentive dome of the 6th century church Hagia Sophia. With the Muslim conquest of the Sassanid and the Byzantine Near East, the dome also became a feature of Muslim architecture. An original tradition of using multiple domes was developed in the church architecture in Russia, which had adopted Orthodox Christianity from Byzantium. Russian domes are often gilded or brightly painted, and typically have a carcass and an outer shell made of wood or metal. The onion dome became another distinctive feature in the Russian architecture, often in combination with the tented roof. Domes in Western Europe became popular again during the Renaissance period, reaching a zenith in popularity during the early 18th century Baroque period. Reminiscent of the Roman senate, during the 19th century they became a feature of grand civic architecture. As a domestic feature the dome is less common, tending only to be a feature of the grandest houses and palaces during the Baroque period. Many domes, particularly those from the Renaissance and Baroque periods of architecture, are crowned by a lantern or cupola, a medieval innovation which not only serves to admit light and vent air, but gives an extra dimension to the decorated interior of the dome.

MODERN-DAY DOMES The dome is a structurally sound design. These days they often made of concrete and reinforced by steel. The main advantage of this style of design is that as it’s heavier in weight, it is difficult to lift it off its base. Moreover, besides the weight of steel and concrete, the shape of the dome itself makes it a very solid structure. According to architects, the arches of the dome are naturally strong and are hardly influenced by extreme external forces like tornadoes. Also with no flat walls, these kinds of structures have very few seams, leading to less penetration of water in the construction especially during tropical


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storms. Moreover, using archways as gates on either side of the building can also help water to run straight off without causing any lasting damage. Today, modern construction techniques and materials reinforce the dome's position as the most classically versatile of all structures. The insulated concrete dome is the ideal solution wherever strength combined with low construction costs are called for. Compared to other types of structures, the domes enclose more volume with the greatest floor area, and the least amount of surface area and perimeter. Superbly energy-efficient, fire-safe, and with an inherent strength that enables it to withstand whatever nature throws at it, hurricanes, earthquakes, even tornadoes. It's no wonder that the modern concrete dome is experiencing a surge of popularity throughout the world.

DOME BASICS VARIETY OF SHAPES

TERMINOLOGY


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BASIC STRUCTURAL PRINCIPLES

SUITABILITY OF DOMES

DIFFERENT TYPES OF DOME STRUCTURES Group 8 – Dome Structures [10.06.10]

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GEODESIC DOMES A geodesic dome is a sphere-like structure composed of a complex network of triangles. The triangles create a self-bracing framework that gives structural strength while using a minimum of material. The term geodesic is from Latin, meaning earth dividing. A geodesic line is the shortest distance between any two points on a sphere. The the idea of combining triangles with the arch was pioneered by German engineer Dr. Walther Bauersfeld when he designed the world's first projection planetarium, built in Jena, Germany in 1922. However, it was Buckminster Fuller ("Bucky") who conceived the concept of geodesic dome homes. Fuller's first patent for a geodesic dome was issued in 1954. Geodesic domes are efficient, inexpensive, and durable. For $350, an African family can be housed in a corrugated metal dome. Plastic and fiberglass domes used for sensitive radar equipment in Arctic regions and for weather stations around the world. Geodesic domes are also used for emergency shelter and mobile military housing. Examples of Geodesic Domes:      

Spaceship Earth, the AT&T Pavilion at Epcot in Disney World, Florida, is an adaptation of Buckminster Fuller's geodesic dome Tacoma Dome in Washington State Milwaukee's Mitchell Park Conservatory Biosphere desert project in Arizona Des Moines Arboretum, a self contained ecosphere Biosphere, constructed for 1967 Expo in Montreal, Canada. Fuller claimed that it would be possible to enclose mid-town Manhattan in New York City with a two-mile wide temperaturecontrolled dome like this one. The dome, he said, would pay for itself within ten years... just from the savings of snow-removal costs.

ECO-DOMES The Eco-Dome is a small home design of approximately 400 square feet (40 sq. meters) interior space. It consists of a large central dome, surrounded by four smaller niches and a wind-scoop, in a clover leaf pattern. Learning and building an Eco-Dome is the next stage after building a small emergency shelter and provides hands-on learning experience in the essential aspects of Superadobe construction. It's small size of approximately 400 square feet (interior space), makes it a manageable structure for the first time owner builder.


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The finished "very small house" is self-contained and can become a small guest house, studio apartment, or be the first step in a clustered design for community use in an Eco-Village of vaults and domes.


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Some features of the Eco-Dome include: 1. Built from local earth-filled Superadobe coils (earth stabilized with cement or lime). 2. Tree free. 3. Maximum use of space through alternative options. The main dome and four niches, depending on local code approval, can function as: 1. main living room, entrance hall, kitchen, bathroom, bedroom (called "bed-womb" because of it's small, organic form!) 2. living room, entrance hall, and three bed-rooms. 3. living room, entrance hall, two bedrooms, and a bathroom. 4. Self-contained single unit (potential for a guest house or studio apartment) or double unit (larger family residence). 5. Can be repeated and joined together to form larger homes and courtyard houses. 6. Can be built by a team of 3-5 persons. 7. Designed with the sun, shade and wind for passive cooling and heating. 8. Wind-scoop can be combined with a rated furnace unit, depending on local code approval. Solar energy and radiant heating may be incorporated. 9. Interior furniture can be built-in with same material. The Blueprints for this design have been previously approved and built in Hesperia City and San Bernardino County, California, as well as other regions nationally and internationally.


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1. The Eco-Dome construction kit package (single unit) includes: documentary step-by-step DVD "Eco-Dome, building a small home", construction documents (mini-version, including the construction specification), unfilled Superadobe roll/earth-bags, educational book on Superadobe construction entitled "Sandbag Shelter and Eco-Village". 2. The full Eco-Dome blueprint package (double unit) includes: construction document blueprints, engineering calculations as permitted under the 1997 UBC / 2001 California Code, construction specification, title 24 energy calculations, and the engineering record. All plans are numbered. The above plans and materials are used in the CalEarth apprenticeship courses.


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DIFFERENT CONSTRUCTION TECHNIQUES OF GEODESIC DOME 1. Flattened conduit Probably the simplest way to build a geodesic dome frame, all you do is flatten the end of some metal tubing bend it slightly then drill a hole. Do these to both ends get yourself a bag of bolts and you can easily build a dome framework in a day. Used for burning man, climbing frames and other small projects. This method may be a bit crude but it’s cheap and easy to implement. Use this technique for building geodesic tent structures, climbing frames and other small homebrew projects.

Making the struts Use the dome calculation tools to find the strut lengths and number of struts to build your dome. Strut length is from hole centers so you need to cut your tube a little longer to allow for this. Building the frame Once you have your tubing cut to length you will need to flatten the end and put a slight bend in, the angle doesn’t have to be exact because the bolts will pull everything together when you assemble your dome framework. Construction tips Using a thin wall tube will make flattening the ends easier but don’t go too thin if you’re making a climbing frame. Colour coding the struts will make it easier to assemble, try using different coloured insulation tape. Use wing nuts for quick assembly/disassembly.


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Covering the framework This type of dome framework is usually covered in canvas or similar material, which can be quite difficult to get tight and crease free over the structure. Also of the unevenness of the joints can make it difficult to cover cleanly. Conclusion This method is a bit rough and ready but it’s cheap and simple to build a dome framework. Covering is quite difficult to get crease free and I wouldn’t recommend trying to cover with a hard covering material. This technique is best suited to building climbing frames and small experimental projects to get the feel for building geodesic structures.

2. Tube and hub Another simple construction technique, slightly more work than the flattened conduit method but is a more professional and flexible system. Instead of joining the struts directly together a larger diameter pipe is used as a hub holes are drilled through the hub and the struts are bolted to it. Advantages: Makes a nice neat job with all struts finishing level while still being cheap and easy to build. Disadvantages: Great for material covers but there is no easy way to fix a hard covering material. This is a great technique for building a tubular dome framework, much nicer and more flexible than the flattened conduit method but still simple to build. Group 8 – Dome Structures [10.06.10]

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Making the struts This is very similar to the flattened conduit method except you’ll need to bend the ends just less than 90 degrees. There are other ways of connecting the struts to the hubs Making the hubs The hubs are real easy to make all you do is take some large diameter metal tube cut it into short lengths and drill the appropriate number of holes evenly around the side. The only thing you’ll need to be careful of is making sure the tube is big enough so you can get a spanner in to tighten the bolts when you come to assemble the dome. Building the frame This method uses tubing with a flattened end like the flattened conduit method but instead of overlapping the ends a hub is used at each vertex. This has many advantages not least being able to take one strut out at a time. The only downside is that you’ll need five or six times as many nuts and bolts, what the heck bolts are cheap anyway. Construction tips Make sure that the pipe used for the hub is of sufficient diameter to allow up to six connections and still get the spanner in to tighten the bolts.


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Covering the framework This system is great for making canvas domes. Cut and stitch a canvas dome slightly smaller than the framework then pull the canvas tight through the centre of each hub (see picture below)

This makes a very professional and tidy job and also shows off the framework, very cool.


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3. Beam and hub Wooden beams are attached to specially made hubs to form the dome framework; the angles are taken care of by the hubs so all you have to do is cut the beams to the correct length. More expensive to build than a tube type framework but makes a solid permanent dome. Advantages: Simple dome construction system that doesn’t require specialist tools or knowledge to build. Disadvantages: The hubs can be expensive and hard to find because they have to be specially made. When the beams have board nailed on both sides there is no way to ventilate the void between, in a heated dome this can lead to damp, dry rot and a number of other problems.

4. Panelized timber frame This system uses wooden beams but instead of metal hubs at the joints panels are made that join at the edges and have the outside material attached (usually plywood). These panels are factory made so all you have to do is nail them together in the correct order to build a dome. Advantages: Simple and extremely fast way to build a permanent dome structure. Disadvantages: Because the panels are factory made you don''t get much design choice. Ventilation problems can occur when material is fixed to both sides.

5. Stressed skin Metal or fibreglass panels are bolted/riveted together to form the dome, there are no beams, hubs or separate support structure the skin does everything. Advantages: Probably the most cost effective and efficient way to build a dome. Some simple fabrication is required but this can be easily sourced locally. Disadvantages: Metal sweats when it gets cold so some form of insulation has to be glued to the inside of the panels to prevent condensation forming. Cutting holes for doors and windows can seriously weaken the dome structure.

6. Monolithic There are basically three stages involved in building a monolithic dome: First an airform membrane made from PVC is inflated on the site were the dome is to be built; this acts as the out weatherproof skin on the finished dome. Next the inside is sprayed with polyurethane foam Group 8 – Dome Structures [10.06.10]

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to insulate the structure; reinforcing bar is fixed to the foam ready for the next stage. Finally a concrete mix is sprayed on top of the urethane to finish. Advantages: Very strong efficient structure requiring very little in the way of heating/cooling. Disadvantages: The outer airform that acts as a weatherproof membrane can be damaged easily allowing water into the insulation layer. Both the PVC airform and the urethane foam insulation are oil based chemical materials, which are not that environmentally friendly. Most monolithic domes require dehumidifiers or heat exchange systems due to the fact that they are so airtight.

7. Space frame Building domes using space frame is actually quite simple, the struts are made from solid bar and they are connected together with solid balls that have fixing points machined into them. Very commonly seen at airports and exhibition halls. Too expensive for the DIY builder but still interesting, the Eden project was built using a space frame.

8. Brick and former This building method dates back hundreds of years and was also used to build arches, bridges etc. A wooden former is made to the shape required then stone, brick, or concrete is laid on top of the former to produce the final dome shape. The former is used to hold the brick, stone or concrete in place until it sets and is able to support its own weight. Usually the former is removed but there is no reason why it couldn’t be left in place. Advantages: Makes a very strong long lasting dome that can be built using reclaimed materials. Disadvantages: A lot of expense is involved in making the former that MUST support the whole weight of the dome when the dome is finished the former becomes redundant. Building very large domes is not cost effective using this system.

9. Foam and render This method uses polystyrene foam or urethane foam as a former. Cut and glue the foam together to form the dome shape. Next tie chicken wire over the foam to act as reinforcing mesh. Finally apply a thin layer of cement render over the whole structure to weatherproof and finish the dome. Advantages: Easy to change or alter the foam former Disadvantages: Only suitable for very small domes. Group 8 – Dome Structures [10.06.10]

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DOME CONSTRUCTION PROCESS (DOME TECHNOLOGY) Many memorable structures throughout history, like the Pantheon, have been built using the thin shell hemispherical shape of the dome. These time-tested monuments surpass many in beauty and longevity. Continuing in the tradition of these magnificent edifices, Dome Technology engages the latest engineering and architectural technologies to produce aesthetic, functional, and economical schools, gymnasiums, waterparks, community centers, and industrial facilities. At a fraction of the cost of a conventional structure, each building benefits from unobstructed views, seating efficiency, great acoustics, and space utilization. Modern insulated concrete dome construction combines several materials to create a strong, efficient, weather-proof structure. Compared to other types of structures for the same application. Insulated concrete dome construction consists of four main phases. Ring Beam Footing Continuous reinforcing bars are embedded in the ring beam foundation. These rebar dowels securely connect the dome to its footing. The ring beam creates a solid base on which to construct the dome. Inflate airform® Made of tough, weather-impermeable material, the airform® is attached to the ring beam footing. The airform® is then inflated with dual inflator fans. The airform® determines the final shape of the dome and becomes a protective cover when the dome is completed. Polyurethane foam The foam is spray applied from in the interior to stiffen the airform®, and provide a secure surface to which reinforcement bar is affixed. The foam hardens and creates a superior insulation layer in the final structure. Shotcrete A framework of rebar is attached to the interior surface of the foam. Application of sprayed concrete (shotcrete) to the reinforcement bar framework comprises the final step in construction of the dome.


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TECHNOLOGY/APPLICATION COATING Polyurethane Foam In the earlier years of dome construction, it was common practice to remove the airform® after the dome was complete. At the time it seemed like a good idea. This saved the customer some money since the cost of the airform® out weighed the cost of exterior paint. Unfortunately, this left a very unattractive finished product and waterproofing proved to be a great challenge. If left untreated, exposed polyurethane decomposes in sunlight at a rate of 1/16th-inch per year. How To Inspect Your Dome Covering No matter what covering is currently protecting your dome, a periodic inspection is required to insure that the polyurethane insulation is not in danger of being exposed. The following applicable guidelines can be used for the inspection:   

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Mechanical Damage: Check for any signs of tears, rips, burns or holes. PVC Degradation: This is usually evidenced by a light colored, chalky appearance. Seam Failure: Look at each seam paying particular attention to corners where horizontal and vertical seams meet. If the corners are starting to curl it may indicate that the vinyl has broken down and lost its plasticity. Vinyl Breakdown. The telltale sign of this condition is if you can see the threads of the polyester fabric. Paints, stuccos and other similar coatings. Besides the applicable steps listed above, check for cracking, flaking or peeling of the coating. Press firmly on the coating in questionable areas. The foam underneath should feel firm, if it seems spongy there is a chance that water has migrated into the foam. Suspect areas: Press firmly on any suspect areas. The foam underneath should feel firm. If it is spongy, water has probably migrated under the coating and saturated the urethane. Records Review: Check your maintenance records to see how long the current coating has been in place versus the manufacturers recommended service life.

Coatings Now Available For years, we have been researching protective coatings. We place strict prerequisites on all potential coatings. These include:  Bondability to the airform®  Water proofing ability  Soil resistance  Longevity  UV protection  Cost  Warranty availability


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Types of Coatings Available    

Paints. We have a wide variety of paints available, ranging in colors and price. Custom designs are available, and we can even put your logo on the side of the dome. Stuccos. For the south western look, we have special elastomeric stucco available that ranges in texture and can be custom colored to fit your needs. Ceramic Tile. This finish is somewhat difficult to apply, but is very aesthetically pleasing and durable. Metal Shingles. Certainly the most durable, metal shingles can be special ordered to match your color needs. Chemical resistant coatings and custom designs are also available.

RECLAIM SYSTEMS Filling and Reclaim of Concrete Domes The most common form of reclaim from dome structures is by front-end loader on a flat, horizontal floor. However, unlike flat structures, material can be piled higher against the walls of a dome, meaning that less floor area is required for a given amount of stored material. Hence, front-end loader reclaim is more efficient than with flat structures, since there is less distance to travel. The inherent strength of the dome's concrete wall allows a loader to scoop against the wall, and is able to withstand blows by front-end loaders better than other conventional structures. Service Access Access for service of automated equipment is normally through a drive-in entrance. This entrance allows the use of front-end loaders as an auxiliary reclaim method. Service access can be through an opening at the dome's apex, or anywhere else on the structure, as design and functionality requirements dictate. Automated Reclaim Systems Where automated reclaim systems are required, the concrete dome's shape and structural characteristics make it adaptable to a wide variety of systems. For products that can be fluidized, sloped floors with air slides have been installed. Conventional stackers and reclaim systems are also frequently installed in concrete domes.


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Conveyor Support The inherent strength of a concrete dome also allows heavy loads from conveyors to be supported on top of the dome. As much as 175,000 lbs. (80 tons) of conveyor loads have been supported on the apex of the concrete dome. The dome's compact shape and high internal volume utilization mean that conveyors can be shorter than those used with more conventional structures. Another significant saving results from the absence of many of the structural supports commonly used with conveyors.

DRIVE THROUGH DOMES Why not combine the benefits of a storage silo with that of a load-out station? Hence the birth of the drive through dome. The drive through dome has the following benefits and components. Drive-through Tunnel with Internal Surge-bin: 1. The product will be conveyed pneumatically in a pipeline at grade to the base of the dome. 2. We can provide a walk-in entry and vertical chase internally from grade to the apex. This chase provides support for the in-fill pipeline, access to the roof dust collector and is typically used to maintain the level controls for the storage facility. 3. The floor is covered with pneumatic extraction systems. As needed, these sections are momentarily activated to fluidize the ash into the collection channel or slot. 4. The central slot houses a pneumatic air gravity conveyor. In combination with the floor, literally all of the material in the dome can be withdrawn. 5. The slot structure discharges to an air lift conveyor, which discharges to the surge bin. There would be a sump pump in this, the lowest point of the system. 6. The surge bin holds enough material for 4 trucks. Much of the storage volume is live to the surge bin. The mechanical floor system is therefore activated less frequently than each truckload. 7. Trucks will approach the loading location. There will be a driver access platform where the truck driver opens the fill hatch on the vehicle. Similarly, there will be a second location for an existing platform to close the vehicle fill hatch. 8. The above grade scale will be located under the fill point which is controlled with a card-scan identification system. The driver will control the fill hatch, and the amount of material transferred to the vehicle. A PLC will record the transaction, which can be electronically synchronized with your accounting system.


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9. We can provide a building for the electrical room, mechanical room and control room of the terminal system over the truck scale. 10. Most drivers will set the lane productivity between 6 or 8 trucks an hour, despite the best planning of terminal designers. The equipment is sized for 200 tph refill rate, 350 tph fill rate from the surge bin. 11. The ends of the tunnel are open, but certainly automatic doors could be optioned, if they provided some local advantages. 12. All of the scale and loading system is well out of the effects of weather in this arrangement. 13. There is only the one dust collector on the dome for permitting purposes. Some states do require the loading DC to be permitted.

TUNNEL TECHNOLOGY (DOME TECHNOLOGY) Dome Technology has successfully designed and constructed several tunnels to compliment bulk storage projects associated with our large storage domes. The basic design criteria that we incorporate with our tunnel design is the basic arched roof geometric shape. This configuration has proved very successful with the following specific advantages: The tunnels are built using steel reinforced shotcrete (a concrete product incorporating 900 lbs of cement per cubic yard). Shotcrete is a product that Dome Technology, Inc has developed to provide the durability and strength requirements of dome structures. Past history and experience with this material at numerous locations has provided break tests as high as 6,000 psi from this product. The arched form used for the tunnel provides increased strength allowing the tunnel to utilize a much thinner wall, floor, and roof thickness compared to conventional rectangular shapes. Dome Technology's method of tunnel design and construction provides an arched metal liner that acts as the tunnel's internal form and supports the reinforced shotcrete method of construction without additional work. This simple factor allows the tunnels to be built in extremely long and continuous sections without downtime associated with extensive work forming techniques. The tunnel design provides the following features:   

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The arched tunnel is very adaptable to junctions, arteries, etc. The metal liner provides a very clean finish to the inside of the tunnel. Our design is very adaptable to custom sizing associated with specific width or height characteristics. The basic limitation of our standard tunnel is any width or height beyond a 6 foot width – 3 foot tall radius. The arch portion of the tunnel is a simple curve. The remaining height of the tunnel is created using vertical pony wall or stem wall procedures.

Some of the tunnel value engineering project improvements that we have constructed include:


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United Arab Emirates Clinker storage dome system. This project required and then utilized our tunnel system to construct approximately 900+ feet of tunnel under a Clinker Storage Dome System to be utilized with a gravity reclaimer that empties the 100,000 ton clinker storage upon demand. Kosmosdale cement storage dome project, Kosmosdale, KY. This Southdown Cement (now Cemex) project utilized one of our tunnel improvement designs to exit the 100,000 ton cement storage dome. It also utilized some 500+ feet of our tunnel to cover and protect the discharge conveyor between the transfer dome (buried dome structure) and the ship loading feed conveyor. This tunnel was constructed in a single run including the gradient and angle change at its midpoint. The transfer dome and tunnel system we constructed saved this client $50,000 and provided more space and usable mechanical area. The system has proven very adaptable to later plant modifications and use. FMC phosphate byproduct storage in Pocatello, ID. FMC utilized our tunnel design to house a combination discharge system above and below ground. The tunnel above ground actually bisects half of the dome and is used as a push wall for the loaders that processes the product into feeder holes in the top of the tunnel. The tunnel supports all of the conveyor systems and keeps the product system moving efficiently. The tunnel starts in a deep access pit at one side of the dome structure and rises completely out the ground prior to exiting the opposite side of the dome. The tunnel is approximately 12' wide and 10' high. The area of this project required structures that could absorb and function in spite of predicted differential settlement. Both the tunnel and dome met the settlement challenge and continue to work well.

REFERENCES http://www.dragishak.com/dome/dome.html http://www.dometech.com/content/Technology.aspx http://architecture.about.com/od/domes/g/geodesic.htm http://fineprints/DomeConstruction.pmd Group 8 – Dome Structures [10.06.10]

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Building Technology - Dome Structures

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