Building Information Modeling is More than Software
It is 2018, and it should be clear to everyone in the AEC industry that BIM is the future of building, infrastructure design, construction, and maintenance. There are millions of marketing dollars spent by BIM software companies each year trying to convince you that Building Information Modeling can’t happen without their product. They will try to convince you that their product is the “real BIM.” Of course, we live in an open, capitalist society where this behavior is expected. However, if you and your firm are making the move to BIM, this background noise may be concerning… and if it’s not, it should be.
In the first paragraph of Wikipedia’s entry on Building Information Modeling, the statement is made that building information models are files that are “…often but not always in proprietary formats and containing proprietary data…” This is troubling to some, however, understandable, of course. If your BIM software solution becomes inaccessible for any reason, your work is captive. For many, this is unacceptable and prevents them from moving forward to the power of BIM.
The idea of proprietary formats and databases is rooted in the concept of traditional BIM.
This concept goes back to the beginning days of computer science. The concept is that these custom data structures can be optimized to store information formatted in a way that improves access speed, reducing the time needed to load the BIM’s data. While this can be true, it’s not a given – especially when you consider the incredible capabilities of today’s computers. And it is possible that proprietary file formats actually hinder productivity by limiting the way that proprietary BIM solutions work across systems and disciplines.
This lack of good software interoperability is a major obstacle to efficiency and technology adoption. This is more insidious than it might appear at first. As firms resist the move to BIM, they limit their ability to work with other disciplines in the larger AEC workflow. This can limit access to expertise, raise total project costs, and add workflow gaps that can lead to costly rework.
Is there a solution to this problem? Yes, and it’s not what some may believe to be the obvious answer. The first part of a modern, interoperable BIM workflow is based on industry standard, non-proprietary file formats. Then, you’ll want your BIM model data represented in accordance with open, international standards. And you’ll need the ability to transfer BIM data accurately between multiple BIM tools that support all disciplines in this modern BIM workflow.
Building Information Modeling (BIM) is a term that has become ubiquitous in the design and construction fields over the past 20 years, but where did it come from? The story is rich and complex with players from the United States, Western Europe and the Soviet Block competing to create the perfect architectural software solution to disrupt 2-Dimensional CAD workflows.
The benefits of an architectural design model tied to a relational database have proven to be incredibly valuable, with contractors becoming the primary drivers of BIM technology for the first time in 2012.
What exactly is BIM?
The question often arises, for the purposes of this article, BIM software must be capable of representing both the physical and intrinsic properties of a building as an object-oriented model tied to a database . In addition most BIM software now features rendering engines, an optimized feature specific taxonomy and a programming environment to create model components. The user can view and interact with the model in three-dimensional views as well as orthographic two-dimensional plan, sections and elevation views of the model. As the model is developed, all other drawings within the project will be correspondingly adjusted. A Building Information Model could be designed in a software that is not strictly speaking, ‘parametric’ and where all information and geometry is explicitly defined but this would be cumbersome.
A parametric building modeler will allow the user to create constraints such as the height of a horizontal level, which can be tied to the height of specified set of walls and adjusted parametrically, creating a dynamic database model which is tied to geometry. This development answered a need in the architectural industry to be able to change drawings at multiple scales and across fragmented drawing sheets. The amount of hours that are necessary for the production of drawings has decreased steadily over time with the general trend of non-farm labor in the United States since 1964. The improvement in productivity has risen in concert with computer technology which has automated tedious tasks in all disciplines. Although some of the earliest programs for architectural representation used a BIM metaphor, limitations in computer power and awkward user interfaces for BIM platforms contributed to a growth in two-dimensional line drawing programs such as AutoCAD and Bentley Microstation.
The Beginnings
The conceptual underpinnings of the BIM system go back to the earliest days of computing. As early as 1962, Douglas C. Englebart gives us an uncanny vision of the future architect in his paper Augmenting Human Intellect.
“the architect next begins to enter a series of specifications and data–a six-inch slab floor, twelve-inch concrete walls eight feet high within the excavation, and so on. When he has finished, the revised scene appears on the screen. A structure is taking shape. He examines it, adjusts it… These lists grow into an evermore-detailed, interlinked structure, which represents the maturing thought behind the actual design.”
Englebart suggests object based design, parametric manipulation and a relational database; dreams that would become reality several years later. There is a long list of design researchers whose influence is considerable including Herbert Simon, Nicholas Negroponte and Ian McHarg who was developing a parallel track with Geographic Information Systems (GIS). The work of Christopher Alexander would certainly have had an impact as it influenced an early school of object oriented programming computer scientists with Notes on the Synthesis of Form. As thoughtful and robust as these systems were, the conceptual frameworks could not be realized without a graphical interface through which to interact with such a Building Model.
Visualizing the Model
From the roots of the SAGE graphical interface and Ivan Sutherland’s Sketchpad program in 1963, solid modeling programs began to appear building on developments in the computational representation of geometry. The two main methods of displaying and recording shape information that began to appear in the 1970s and 1980s were constructive solid geometry (CSG) and boundary representation(brep). The CSG system uses a series of primitive shapes that can be either solids or voids, so that the shapes can combine and intersect, subtract or combine to create the appearance of more complex shapes. This development is especially important in representing architecture as penetrations and subtractions are common procedures in design, (windows, doors).
The process of design requires a visceral connection to the medium that the designer is working in. This posed another challenge as architects required a way to tell the computer what to do that was less tedious than the punch cards that were used on early computers. The development of light pens, head-mounted displays and various contraptions in the early days of human-computer interaction (HCI) are well documented elsewhere. A rigorous history of HCI from an architectural perspective can be found in Nicholas DeMonchaux’s book, Spacesuit: Fashioning Apollo. The text carves a narrative of the precursors to BIM and CAD technology as they were entwined in the Space Race and Cold War.
Database Building Design
Seeing buildings through the lens of the database contributed to the breakdown of architecture into its constituent components, necessitating a literal taxonomy of a buildings constituent parts. One of the first projects to successfully create a building database was the Building Description System (BDS) which was the first software to describe individual library elements which can be retrieved and added to a model. This program uses a graphical user interface, orthographic and perspective views and a sortable database that allows the user to retrieve information categorically by attributes including material type and supplier. The project was designed by Charles Eastman who was trained as an architect at Berkeley and went on to work in computer science at Carnegie Melon Uniersity. Eastman continues as expert in BIM technology and Professor at the Georgia Tech School of Architecture.
Eastman claims that drawings for construction are inefficient and cause redundancies of one object that is represented at several scales. He also criticizes hardcopy drawings for their tendency to decay over time and fail to represent the building as renovations occur and drawings are not updated. In a moment of prophecy, the notion of automated model review emerges to “check for design regularity” in a 1974 paper.
Eastman concluded that BDS would reduce the cost of design, through ‘drafting and analysis efficiencies’ by more than fifty percent. Eastman’s project was funded by DARPA, the Advanced Research Projects Agency and was written before the age of personal computers, on a PDP-10 computer. Very few architects were ever able to work on the BDS system and its unclear whether any projects were realized using the software. BDS was an experiment that would identify some of the most fundamental problems to be tackled in architectural design over the next fifty years. Eastman’s next project, GLIDE (Graphical Language for Interactive Design) created in 1977 at CMU, exhibited most of the characteristics of a modern BIM platform.
In the early 1980′s there were several systems developed in England that gained traction and were applied to constructed projects. These include GDS, EdCAAD, Cedar, RUCAPS, Sonata and Reflex. The RUCAPS software System developed by GMW Computers in 1986 was the first program to use the concept of temporal phasing of construction processes and was used to assist in the phased construction of Heathrow Airport’s Terminal three (Laiserin – History of BIM). The founding of the Center for Integrated Facility Engineering (CIFE) at Stanford in 1988 by Paul Teicholz marks another landmark in the development of BIM as this created a wellspring of PhD students and industry collaborations to further the development of ‘four-dimensional’ building models with time attributes for construction. This marks an important point where two trends in the development of BIM technology would split and develop over the next two decades. On one side, the development of specialized tools for multiple disciplines to serve the construction industry and improve efficiency in construction. On the other side is the treatment of the BIM model as a prototype that could be tested and simulated against performance criteria.
A later but prominent example of a simulation tool that gave feedback and ‘suggested’ solutions based on a model is the Building Design Advisor, developed at Lawrence Berkeley National Lab beginning in 1993. This software utilizes an object model of a building and its context to perform simulations. This program was one of the first to integrate graphical analysis and simulations to provide information about how the project might perform given alternative conditions regarding the projects orientation, geometry, material properties and building systems. The program also includes basic optimization assistants to make decisions based on a range of criteria which are stored in sets called ‘Solutions’.
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“The input on the left generates the stairs on the right that can be adjusted parametrically. Charles Eastman’s GLIDE was one of the first programs to incorporate most of the major features present in BIM software today.” Image via Charles Eastman’s paper “GLIDE.”
Virtual Building
While the developments were happening rapidly in the United States, the Soviet Block had two programming geniuses who would end up defining the BIM market as it is known today. Leonid Raiz and Gábor Bojár would go on to be the respective co-founder and founder of Revit and ArchiCAD. ArchiCAD developed in 1982 in Budapest, Hungary by Gábor Bojár, a physicist who rebelled against the communist government and began a private company. Gábor wrote the initial lines of code by pawning his wife’s jewelry and smuggling Apple Computers through the Iron Curtain (Story). Using similar technology as the Building Description System, the software Radar CH was released in 1984 for the Apple Lisa Operating System. This later became ArchiCAD, which makes ArchiCAD the first BIMsoftware that was made available on a personal computer.
The software was slow to start as Bojár had to struggle with a unfriendly business climate and the limitations of personal computer software, so ArchiCAD was not used on large scale projects until much later. ArchiCAD has made substantial gains in user base from 2007-2011, mainly as a tool for developing residential and small commercial projects in Europe. Recent improvements have made ArchiCAD a major player in the market though fundamental issues such as a lack of a phasing component and a complicated (but flexible) programming environment for its family components using GDL (Geometric Description Language) To date, Graphisoft claims that more than 1,000,000 projects worldwide have been designed using ArchiCAD.
Not long after Graphisoft began to sell the first seats of Radar CH, Parametric Technology Corporation (PTC) was founded in 1985 and released the first version of Pro/ENGINEER in 1988. This is a mechanical CAD program that is utilizes a constraint based parametric modeling engine. Equipped with the knowledge of working on Pro/ENGINEER, Irwin Jungreis and Leonid Raiz split from PTC and started their own software company called Charles River Software in Cambridge, MA.
The two wanted to create an architectural version of the software that could handle more complex projects than ArchiCAD. They hired David Conant as their first employee, who is a trained architect and designed the initial interface which lasted for nine releases. By 2000 the company had developed a program called ‘Revit’, a made up word that is meant to imply revision and speed, which was written in C++ and utilized a parametric change engine, made possible through object oriented programming. In 2002, Autodesk purchased the company and began to heavily promote the software in competition with its own object-based software ‘Architectural Desktop’.
Revit revolutionized the world of Building Information Modeling by creating a platform that utilized a visual programming environment for creating parametric families and allowing for a time attribute to be added to a component to allow a ‘fourth-dimension’ of time to be associated with the building model. This enables contractors to generate construction schedules based on the BIM models and simulate the construction process. One of the earliest projects to use Revit for design and construction scheduling was the Freedom Tower project in Manhattan. This project was completed in a series of separated but linked BIM models which were tied to schedules to provide real-time cost estimation and material quantities. Though the construction schedule of the Freedom Tower has been racked with political issues, improvements in coordination and efficiency on the construction site catalyzed the development of integrated software that could be used to view and interact with architects, engineers and contractors models in overlay simultaneously.
“This screenshot from Radar CH (later ArchiCAD) shows how far BIM modeling capabilities had developed by 1984, the first major BIM release on a personal computer.” Image via Graphisoft
Towards a Collaborative Architecture
There has been a trend towards the compositing of architectural files with those of engineers who create the systems to support them which has become more prevalent within the past seven years as Autodesk has released versions of Revit specifically for Structural and Mechanical engineers. This increased collaboration has had impacts on the larger industry including a movement away from design-bid-build contracts towards integrated project delivery where many disciplines typically work on a mutually accessible set of BIM models that are updated in varying degrees of frequency. A central file takes an object and applies an attribute of ownership so that a user who is working on a given project can view all objects but can only change those that they have checked out of a ‘workset’. This feature released in Revit 6 in 2004, enables large teams of architects and engineers to work on one integrated model, a form of collaborative software. There are now several firms working towards visualization of BIM models in the field using augmented reality.
A broad variety of programs used by architects and engineers makes collaboration difficult. Varying file formats lose fidelity as they move across platforms, especially BIM models as the information is hierarchical and specific. To combat this inefficiency the International Foundation Class (IFC) file format was developed in 1995 and has continued to adapt to allow the exchange of data from one BIM program to another. This effort has been augmented by the development of viewing software such as Navisworks which is solely designed to coordinate across varying file formats. Navisworks allows for data collection, construction simulation and clash detection and is used by most major contractors in the US today.
Following in the footsteps of the Building Design Advisor, simulation programs such as Ecotect, Energy Plus, IES and Green Building Studio allow the BIM model to be imported directly and results to be gathered from simulations. In some cases there are simulations that are built directly into the base software, this method of visualization for design iteration has been introduced to Autodesk’s Vasari, a stand alone beta program similar to the Revit Conceptual Modeling Environment where solar studies and insolation levels can be calculated using weather data similar to the Ecotect package. Autodesk, through their growth and acquisition of a broad variety of software related to BIM have contributed to the expansion of what is possible from analysis of a model. In late November 2012, the development of formit, an application that allows the conceptual beginnings of a BIM model to be started on a mobile device is a leap for the company.
Contemporary Practice and Design Academics
Some have taken a negative stance on BIM and parametrics as they assume so much about the design process and limit any work produced to the user’s knowledge of the program. This can enable a novice designer who has learned how to perform basic commands to become an incredibly prolific producer while a highly educated and experienced architect can be crippled from inexperience with a programs interface or underlying concepts. This creates a potential for a generational break line that becomes more harsh as a new technology gains market parity.
Some BIM platforms that have a small market share but have made big impacts on the world of design include Generative Components (GC), developed by Bentley Systems in 2003. The GC system is focused on parametric flexibility and sculpting geometry and supports NURBS surfaces. The interface hinges on a node-based scripting environment that is similar to Grasshopper to generate forms. Digital Project is a similar program was developed by Gehry Technologies around 2006 based on CATIA, a design program (and one of the first CAD programs) that was developed as an in house project by Dessault systems, a French airplane manufacturer. These two platforms have spawned something of a revolution in design as the power to iterate and transform has resulted in especially complex and provocative architectural forms.
Patrick Schumacher has coined the movement of parametric building models in architecture, specifically those which allow for NURBS surfaces and scripting environments as ‘parametricism’ in his 2008 ‘Parametricist Manifesto’.
“The current stage of advancement within parametricism relates as much to the continuous advancement of the attendant computational design technologies as it is due to the designer’s realization of the unique formal and organizational opportunities that are afforded. Parametricism can only exist via sophisticated parametric techniques. Finally, computationally advanced design techniques like scripting (in Mel-script or Rhino-script) and parametric modeling (with tools like GC or DP) are becoming a pervasive reality. Today it is impossible to compete within the contemporary avant-garde scene without mastering these techniques.”
Since these techniques have become increasingly complex there has become a component of architectural schools which is specified to train in specific software. A student with knowledge of only one type of software platform may well be trained to design according to the biases of the programs that they are using to represent their ideas. Software performs useful tasks by breaking down a procedure into a set of actions that have been explicitly designed by a programmer. The programmer takes an idea of what is commonsense (Sack 14) and simulates a workflow using tools available to them to create an idealized goal. In the case of BIM tools, the building is represented as components including walls, roofs, floors, windows, columns, etc. These components have pre-defined rules or constraints which help them perform their respective tasks.
BIM platforms typically represent walls as objects with layers, these layers are defined in terms of the depth and height of a wall and are extruded along the length of a line. The program then has the ability to calculate the volume of material contained within the wall assembly and to create wall sections and details easily. This type of workflow is based on the existing building stock and common industry standards and therefore a project which is produced in a BIM platform which emphasizes these tools is likely to reinforce existing paradigms rather than develop new ones. Additionally, the programmers who worked on the early BIM platforms often did not have a background in architecture but employed hybrid architect/programmers who contributed to the development of the programs. One notable exception I have found to this is the work of Charles Eastman who received a Masters of Architecture from Berkeley before working on the Building Description System. The roots of the major BIM platforms that are in use today have been developed by programmers with the peripheral input of hybrid programmer/architects and a global user base who contributes to the development of the software via ‘wish lists’ or online forums where grievances can be aired about a product workflow. The grievances typically result in new features and build upon the existing interface.
Though the general concept and technology behind BIM is approaching its thirtieth anniversary, the industry has only begun to realize the potential benefits of Building Information Models. As we reach a point where a majority of buildings are being crafted digitally, an existing building marketplace where building materials and structural components can be bought and sold locally will emerge. Sustainable design practices reinforce an attitude of designing for disassembly and a marketplace of these parts is essential. Trends in Human Computer Interaction, Augmented Reality, Cloud Computing, Generative Design and Virtual Design and Construction continue to rapidly influence the development of BIM. Looking back at the past it is easier to realize that the present moment is an exciting time for designers and programmers in this evolving industry.
New materials and energy, design approaches, as well as advances in digital technology and big data, are creating a wave of innovation within the construction industry. Here are ten of the most exciting developments.
1. Self-healing concrete
Cement is one of the most widely used materials in construction, but also one of the largest contributors to harmful carbon emissions, said to be responsible for around 7 per cent of annual global emissions. Cracking is a major problem in construction, usually caused by exposure to water and chemicals. Researchers at Bath University are looking to develop a self-healing concrete, using a mix containing bacteria within microcapsules, which will germinate when water enters a crack in the concrete to produce limestone, plugging the crack before water and oxygen has a chance to corrode the steel reinforcement.
2. Thermal bridging
Efficient insulation material is becoming increasingly important throughout the construction industry. Heat transmission through walls tends to be passed directly through the building envelope, be it masonry, block or stud frame, to the internal fascia such as drywall. This process is known as “thermal bridging”. Aerogel, a technology developed by Nasa for cryogenic insulation, is considered one of the most effective thermal insulation materials and US spin-off Thermablok has adapted it using a proprietary aerogel in a fibreglass matrix. This can be used to insulate studs, which can reportedly increase overall wall R-value (an industry measure of thermal resistance) by more than 40 per cent.
3. Photovoltaic glaze
Building integrated photovoltaic (BIPV) glazing can help buildings generate their own electricity, by turning the whole building envelope into a solar panel. Companies such as Polysolar provide transparent photovoltaic glass as a structural building material, forming windows, façades and roofs. Polysolar’s technology is efficient at producing energy even on north-facing, vertical walls and its high performance at raised temperatures means it can be double glazed or insulated directly. As well as saving on energy bills and earning feed-in tariff revenues, its cost is only marginal over traditional glass, since construction and framework costs remain, while cladding and shading system costs are replaced.
4. Kinetic Footfall
Kinetic energy is another technology under development. Pavegen provides a technology that enables flooring to harness the energy of footsteps. It can be used indoors or outdoors in high traffic areas, and generates electricity from pedestrian footfall using an electromagnetic induction process and flywheel energy storage. The technology is best suited to transport hubs where a large flow of people will pass over it. The largest deployment the company has done so far is in a football pitch in Rio de Janeiro to help power the floodlights around the pitch. It also currently has a temporary installation outside London’s Canary Wharf station powering street lights.
5. Kinetic Roads
Italian startup Underground Power is exploring the potential of kinetic energy in roadways. It has developed a technology called Lybra, a tyre-like rubber paving that converts the kinetic energy produced by moving vehicles into electrical energy. Developed in co-operation with the Polytechnic University of Milan, Lybra operates on the principle that a braking car dissipates kinetic energy. The cutting-edge technology is able to collect, convert this energy into electricity and pass it on to the electricity grid. In addition to improving road safety, the device upgrades and promotes sustainability of road traffic.
6. Predictive Software
The structural integrity of any building is only as good as its individual parts. The way those parts fit together, along with the choice of materials and its specific site, all contribute to how the building will perform under normal, or extreme, conditions. Civil engineers need to integrate a vast number of pieces into building designs, while complying with increasingly demanding safety and government regulations. An example of this was work on the structural integrity of the arch rotation brackets at Wembley Stadium, undertaken by Bennett Associates, using ANSYS software, which simulated the stresses on the brackets that hold and move the distinctive arches above the stadium.
7. 3D Modelling
Planning innovation has been driven by the growth of smart cities. CyberCity3D(CC3D) is a geospatial-modelling innovator specialising in the production of smart 3D building models. It creates smart digital 3D buildings to help the architectural, engineering and construction sector visualise and communicate design and data with CC3D proprietary software. The models integrate with 3D geographic information system platforms, such as Autodesk and ESRI, and can stream 3D urban building data to Cesium’s open architecture virtual 3D globe. It provides data for urban, energy, sustainability and design planning, and works in conjunction with many smart city SaaS platforms such as Cityzenith.
8. Modular Construction
Modular construction is increasingly popular where a building is constructed off-site using the same materials and designed to the same standards as conventional on-site construction. It limits environmental disruption, delivering components as and when needed, and turning construction into a logistics exercise. It also has strong sustainability benefits, from fewer vehicle movements to less waste. With up to 70 per cent of a building produced as components, it allows a move towards “just in time” manufacturing and delivery. In use in the United States and UK, Chinese developer Broad Sustainable Building recently completed a 57-storey skyscraper in 19 working days using this method.
9. Cloud Collaboration
basestone is a system allowing the remote sharing of data on a construction site in real time. It is predominantly a review tool for engineers and architects which digitises the drawing review process on construction projects, and allows for better collaboration. The cloud-based collaboration tool is focused on the installation of everything from steel beams to light fittings. The system is used to add “snags”, issues that happen during construction, on to pdfs, then users can mark or add notes through basestone. Trials have revealed possible cost-savings of around 60 per cent compared with traditional paper-based review methods.
10. Asset mapping
Asset mapping focuses on operational equipment, including heating and air conditioning, lighting and security systems, collecting data from serial numbers, firmware, engineering notes of when it was installed and by whom, and combines the data in one place. The system can show engineers in real time on a map where the equipment needs to be installed and, once the assets are connected to the real-time system using the internet of things, these can be monitored via the web, app, and other remote devices and systems. It helps customers build databases of asset performance, which can assist in proactive building maintenance, and also reduce building procurement and insurance costs.
19 Amazing Vintage Photos That Show How People Worked Before AutoCAD
Technological advances cause some professions to cease to exist, but in the case of drafting technicians, it just made their desks smaller and tidier. AutoCAD was released in 1982 and by 1994 as many as 750 training centers had been using it worldwide. Before, drafting required pencils, erasers, t-squares, and much more time. And the photos below really show it. Looking at them, you can almost hear the rustling paper. Now, architectural, electrical and other drafters are mainly clicking their mouse and keyboard. Scroll down to check out what the old days were like.
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Whether its builder is a beaver or a person, a dam is always used for the same purpose: to manage, direct and prevent water flow. There an estimated 845,000 dams in the world; here are our picks for the 18 strangest.
Three Gorges Dam
Where: Sandouping, China–Yangtze River
Why It’s Unique: China’s Three Gorges Dam is not only the world’s largest hydroelectric dam, it’s also the world’s single largest source of electricity. The construction of the dam has been convoluted: Preliminary plans began as far back at 1932 but construction but didn’t start until late 1994; the dam isn’t scheduled to be completely finished until 2011. The structure’s estimated life is as short as 70 years; that was deemed long enough to justify the displacement of 1.24 million people.
Itaipu Dam
Where: On the border of Brazil and Paraguay–Parana River
Why It’s Unique: The Itaipu Dam, a partnership between Brazil and Paraguay, generated over 90,000 gigawatt hours of power in 2000—then a world record for hydroelectric generation. With a height of more than 196 meters, the dam stands as tall as a 65-story building. Its construction used enough steel to build 380 Eiffel Towers, along with 12.3 million cubic meters of concrete.
Guri Dam
Where: Bolivar State, Venezuela–Caroni River
Why It’s Unique: The Guri Dam in Venezuela not only boasts sky-high walls and powerful generators, it also has artistic flair. Artist Carlos Cruz Diez decorated one of the plant’s machine rooms in mind-bending pattern of colorful vertical bars, while Alejandro Otero built an enormous rotating kinetic sculpture nearby. The dam produces the energy equivalent of approximately 300,000 barrels of oil per day.
Grand Coulee Dam
Where:Grand Coulee, Washington–Columbia River
Why It’s Unique: Washington state’s Grand Coulee Dam is the largest in the United States. Nearly a mile long and 503 meters wide, its base area is large enough to hold all the pyramids of Giza. At 115 meters high, the dam is more than twice the height of Niagara Falls. The dam also has a memorable role in folk music history—a governmental energy organization commissioned Woody Guthrie to write songs about the dam in the early 1940s, including “Roll On, Columbia, Roll On” and “Grand Coulee Dam.”
Sayano-Shushenskaya Dam
Where: Khakassia, Russia–Yenisei River
Why It’s Unique: Russia’s Sayano-Shushenskaya Dam may not hold any records for its electricity generation, but other dams are no match for its sheer strength—the structure’s stated ability to withstand 8.0-magnitude earthquakes has earned it a spot in the Guinness Book of World Records. Still, not even the world’s strongest dam is immune to problems—a 2009 accident in which a turbine exploded resulted in the deaths of 75 people and 40 tons of oil spilled into the river.
Krasnoyarsk Dam
Where: Divnogorsk, Russia–Yenisey River
Why It’s Unique: Although the Krasnoyarsk dam has operated without the notoriety of its Russian neighbor, this concrete gravity dam has troubles of its own. The plant and its reservoir have apparently wrought changes on the local climate, causing the area to experience warmer and more humid weather conditions than the norm, and reducing ice cover in the area, which is in Siberia. Russia shows off the engineering feat on its 10-ruble bill.
Robert-Bourassa Dam
Where: Quebec, Canada–La Grande River
Why It’s Unique: Situated over Canada’s La Grande River, the Robert-Bourassa dam reaches 140 meters below the surface, making it the world’s largest underground plant. The dam’s centerpiece is a unique “giant’s staircase”—each step is the size of two football fields—that sweeps water downward.
Sand Dams
Where: Kenya
Why It’s Unique: Since 1995, Kenya has constructed more than 500 sand dams, which are usually about 50 meters long and 2 to 4 meters high. Unlike larger dams, which usually are used for hydroelectric power, these smaller structures are designed to store water during the wet season so dry communities have a water reservoir when the rain stops. These dams, which store water buried in silt, do a better job than surface water dams of keeping water from evaporating and maintaining water quality.
Redridge Steel Dam
Where: Redridge, Michigan–Salmon Trout River
Why It’s Unique: Located in Houghton County, Mich., this flat slab buttress dam is one of only three steel dams in the United States. Built in 1894, the dam’s spillway broke in 1941 and was partially repaired in 2001.
Timber Dams
Where: Japan
Why It’s Unique: To limit carbon dioxide emissions from steel and concrete dam construction, northern Japan’s Akita Prefecture started a project to build small-scale dams out of the country’s abundant supply of cedar. The dams serve mainly to minimize the effects of landslides and mud flows in the mountains.
Inguri Dam
Where: Jvari, Georgia–Inguri River
Why It’s Unique: At 892 feet in height, the Inguri Dam is the world’s tallest concrete arch dam. Completed in 1978, it was repaired in 1999 at a cost of 116 million euros.
New Cornelia Mine Tailings Dam
Where: New Cornelia Mine Tailings Dam
Why It’s Unique: In terms of sheer volume, the 7.4 billion cubic foot New Cornelia MineTailings Dam is the country’s largest dam structure. But this dam isn’t used for water—it’s used for mining. Mine tailings (loose collections of crushed rock left over from the mining process) were dumped here before the mine was shut down in 1983.
Syncrude Tailings Dam
Alberta, Canada
The Syncrude Tailings Dam holds the highest volume of material of any dam in the world: 540,000,000 cubic meters. This dam holds tailings from oil sands extraction; 500,000 tons of tailings are produced each day.
Verzasca Dam
Where: Ticino, Switzerland
Why It’s Unique: The Verzasca Dam, completed in 1965, is renowned for its beauty and its slender concrete arch. The design used less concrete than comparable dams, resulting in lower construction costs. When its reservoir was filled, small earthquakes were triggered.
Santee Cooper Dam System
Where: Pinopolis, South Carolina—Santee River
Why It’s Unique: Built to create jobs in the region during the Great Depression, the Santee Cooper Dam system boasts a reservoir area of 186,000 acres. The dam system, 42 miles in total, survived the third worst earthquake in U.S. history and was subsequently redesigned and stabilized for future quakes. The Pinopolis Dam, which is part of the Santee Cooper system, has the highest single-lift lock in the world for raising and lowering boats between different levels of water.
Roosevelt Dam
Where: Phoenix, Arizona—Salt River
Why It’s Unique: Italian stonemasons crafted this dam, hand-cutting all the stones for the project. In recent years, the dam’s height was raised 23 meters to increase water storage space by 20 percent, and it was completely resurfaced in concrete, changing its appearance.
Chalk Hills Dam
Where: On the Border of Wisconsin and Michigan—Menominee River
Why It’s Unique: The power house connected to this dam resembles a cathedral, complete with stained-glass windows celebrating the engineers and bankers involved in the original construction, and small multi-colored terrazzo tile. The structure was completed in 1927.
World’s Largest Beaver Dam
Where: Wood Buffalo National Park—Alberta, Canada
Why It’s Unique: Google Earth found the largest beaver dam in Alberta, Canada at 850 meters long–the closest size relative exists in Montana at 652 meters. Viewers think two beaver families constructed this massive piece of architecture, which contains two separate beaver lodges inside. The entire dam is surrounded by wetlands, common of more sizable beaver creations.
Dam types can be classified in different categories according to the material used in construction and how they withstand the thrust of water:
homogeneous drained earthfill dams, either zoned or with a man-made impervious element;
gravity dams, whether concrete or RCC;
arch dams;
and buttress or multiple arch dams (not dealt with here).
Fill dams are flexible structures while the other types are rigid.The main parameters to be taken into account in choosing a dam site and type are the following:
topography and inflow in the catchment area;
morphology of the river valley;
geological and geotechnical conditions;
climate and flood regime.
In many cases, after consideration of all these aspects, several types of dams will remain potential candidates. Economic considerations are then applied to rank the available alternatives.
1. TOPOGRAPHY AND INFLOW IN THE CATCHMENT AREA
If we ignore the case of lakes for recreational purposes and small dams for hydroelectric power generation, reservoir storage is the main factor influencing the entire dam design. The objective is in fact to have a volume of water available for increasing dry weather river flow, irrigation or drinking-water supply, or free storage capacity to attenuate flooding.
The first task therefore consists in calculating the volume of water that can be stored in a basin, possibly at several different sites. A first approximation can be achieved using a 1/25 000 scale map with contour lines every 5 or 10 metres, except for reservoirs with storage of several tens of thousand cubic metres. The second task will then be to check whether conditions in the catchment area are such that the reservoir will be filled and to calculate the risk of shortfall.
2. MORPHOLOGY OF THE RIVER VALLEY
A dam is by nature linked to an environment. The morphology of the river valley therefore plays a vital role in the choice of a dam site and the most suitable type of dam.
Of course, the ideal and most economical location will be a narrow site where the valley widens upstream of the future dam, provided that the dam abutments are sound (i.e. a narrowing with no zones prone to rockfall or landslide).
Such a site is rarely found, either because the natural structure of a valley does not offer any point of narrowing or because the choice of the site is not solely dependent on engineering considerations.
As a first approach, a wide valley will be more suitable for construction of a fill dam.
A narrow site will be suitable for a gravity dam as well, and a very narrow site will be suitable for an arch. In every case, of course, provided that the foundation is acceptable.
3. GEOLOGY AND FOUNDATION CONDITIONS
The nature, strength, thickness, dip, jointing and permeability of the geological foundations at the site are a set of often decisive factors in selection of the dam type.
ROCK FOUNDATIONS
Except for severely jointed rock or rock with very mediocre characteristics, rock foundations are suitable for construction of any type of dam, provided that suitable measures are taken to strip off severely weathered materials and, if necessary, treat the foundation by grouting. Fill dams will always be suitable. For the other types, requirements are more severe for RCC, still more for conventional concrete, and finally most stringent for arch dams. The most important aspect is cracking (faults, joints, schistosity).
GRAVEL FOUNDATIONS
Provided that they are sufficiently compacted, gravel foundations are generally suitable for earth or rockfill dams, at least in terms of mechanical strength. Leakage must be controlled by suitable impervious barriers and drainage systems. In practice however, this type of foundation essentially is found on rivers with high flows. The dam must
therefore be able to discharge high floods, which precludes earthfill dams. Very small concrete dams may also be suitable provided precautions are taken with leaks and seepage (risk of piping) and with differential settlement.
SANDY-SILT FOUNDATIONS
Silt or fine sand foundations can be suitable for construction of earthfill dams, and even, in exceptional cases, for very small concrete gravity dams provided strict precautions are taken.
CLAY FOUNDATIONS
Clay foundations almost automatically impose the choice of a fill dam with slopes that are compatible with the mechanical characteristics of the geological formations.
4. AVAILABLE MATERIALS
Availability, on the site or near it, of suitable materials to build the dam has a considerable influence and one that is often decisive in choosing the type of dam:
soil that can be used for earthfill,
rock for rockfill or slope protection (rip-rap),
concrete aggregate (alluvial or crushed materials),
cementitious materials (cement, flyash, etc.).
If it is possible to extract the materials from the reservoir itself, reservoir storage can be increased. This also usually keeps the cost of transport and restoring borrow areas to a minimum.
As a general rule, if silty or clay soil of satisfactory quality (fines content, plasticity, condition) and quantity (1.5 times or twice the volume of fill required) is available, a dam construction alternative using homogeneous earthfill or quarry-sorted materials – setting aside the coarsest materials for the downstream shoulder – will be the most economical provided that the flood flows to be discharged are moderate.
If only a limited quantity of impermeable materials, and coarse or rockfill materials as well, is available, the possibility of a zoned earthfill dam or a rockfill dam with a watertight core can be considered. The disadvantage of this alternative is placement in zones, which is all the more complicated when the site is narrow, hindering movement of the machinery.
If only coarse materials are available, they can be used to build a homogeneous embankment with a watertight diaphragm wall built in the centre of the dam, by grouting after the fill has been placed or by an upstream watertight structure (concrete or bituminous concrete facing).
If only rockfill is available, a compacted rockfill dam with external watertight structure (geomembrane, hydraulic concrete or bituminous concrete facing) on the upstream face, will be suitable. A concrete alternative, especially RCC, can also prove to be competitive provided the foundation is good enough (rock or compact ground) with no need for excessive excavation.
5. FLOODS AND FLOOD DISCHARGE STRUCTURES
The cost of flood discharge structures depends on the hydrological characteristics of
the catchment area.
When the catchment area is large and floods are likely to be high, it may be advantageous to combine the dam and spillway functions and build an overspill dam.
On the other hand, if the spillway can be kept small, a fill dam will be preferred if all other conditions are equal.
When construction of the spillway would require significant excavation, the possibility of using the excavated materials will also be a factor in favour of building a fill dam.
When a tunnel is required for temporary diversion of the river during the work, it can usefully be incorporated into the flood discharge structures, if necessary increasing its cross-section slightly.
The choice of an RCC dam can be attractive if it is a means of shortening construction lead time and removing the risk of damage from flooding of the site before construction is complete, a risk that, with any other alternative, would mean building costly diversion or protection structures.
6. ECONOMIC CRITERIA
In many cases, the considerations set out above will be sufficient to select several types of dam as potential alternatives. For example, if the foundation is rock, loose materials are available near the site and flood flows are high, the choice will be between an RCC dam and an earthfill dam with a costly spillway.
The studies must then be pursued for these two types of dam, taking care to refine the cost estimates as the studies progress. As soon as one of the dam types seems significantly more economical, it is preferable to waste no further time on the other option.
CONCLUSIONS ON SELECTING A TYPE OF DAM
The choice of a type of dam is imposed by natural conditions in many cases, with no need for in-depth investigations. For example, if the rock substratum is at a depth of more than 5 metres, the only reasonable alternative will be a fill dam, at least for any project less than 25 metres high. In some regions, the geological context is such that
only one type of dam is usually built.
In other cases, the choice of dam type will be a compromise between different aspects – type of foundation, availability of materials in the vicinity, hydrology – to arrive at the best option economically speaking.
However, it is always an advantage to make a decision as quickly as possible, as a rule after the feasibility studies.
Depending upon the position in a railway track, railway sleepers may be classified as:
Longitudinal Sleepers
Transverse Sleepers
1. Longitudinal Sleepers
These are the early form of sleepers which are not commonly used nowadays. It consists of slabs of stones or pieces of woods placed parallel to and underneath the rails. To maintain correct gauge of the track, cross pieces are provided at regular intervals.
At present this type of sleepers are discarded mainly because of the following reasons.
Running of the train is not smooth when this type of sleepers is used.
Noise created by the track is considerable.
Cost is high.
2. Transverse Sleepers
Transverse sleepers introduced in 1835 and since then they are universally used. They remove the drawbacks of longitudinal sleepers i.e. the transverse sleepers are economical, silent in operation and running of the train over these sleepers is smooth. Depending upon the material, the transverse sleepers may be classified as:
Timber/wooden sleepers
Steel sleepers
Cast Iron Sleepers
Concrete Sleepers
Timber or Wooden Sleepers
The timber sleepers nearly fulfilled all the requirements of ideal sleepers and hence they are universally used. The wood used may be like teak, sal etc or it may be coniferous like pine.
The salient features of timber/wooden sleepers with advantages and disadvantages.
Advantages of Timber Sleepers
They are much useful for heavy loads and high speeds
They have long life of 10-12 years depending upon the climate, condition, rain, intensity, nature of traffic, quality of wood etc
Good insulators and hence good for track circuited railway tracks
They are able to accommodate any gauge
Suitable for salty regions and coastal areas
Can be used with any section of rail
Can be handled and placed easily
They are not badly damaged in case of derailment
They are not corroded
Cheaper than any other types of sleepers
Disadvantages of Timber Sleepers
Liable to be attacked by vermin so, they must be properly treated before use
Liable to catch fire
They do not resist creep
They are affected by dry and wet rot
Become expensive day by day
Life is shorter compare to others
Steel sleepers
They are in the form of steel trough inverted on which rails are fixed directly by keys or nuts and bolts and used along sufficient length of tracks.
Advantages of Steel Sleepers
Have a useful life of 20-25 years.
Free from decay and are not attacked by vermins
Connection between rail and sleeper is stronger
Connection between rail and sleeper is simple
More attention is not required after laying
Having better lateral rigidity
Good scrap value
Suitable for high speeds and load
Easy to handle
Good resistance against creep
Disadvantages of Steel sleepers
Liable to corrosion by moisture and should not because in salty regions
Good insulators and hence cannot be used in track circuited regions
Cannot be used for all sections of rails and gauges
Should not be laid with any other types of ballast except store
Very costly
Can badly damaged under derailments
Way gauge is obtained if the keys are over driven
The rail seat is weaker
Having good shock absorber as there is not cushion between rail foot and ballast
Cast Iron Sleepers
They consist of two pots or plates with rib and connected by wrought iron tie bar of section of about 2″ ½” each pot or plate is placed below each rail. The pot is oval in shape with larger diameter 2′-0″ and smaller diameter 1′-8″ is preferred. Plate sleepers consist of rectangular plates of size about 2′ – 10′ x 1′ – 0″.
The relative advantages and disadvantages are given below.
Advantages of Cast Iron Sleepers
Long life upto 50-60 years
High scrape value as they can be remolded
Can be manufactured locally
Provided sufficient bearing area
Much stronger at the rail seat
Prevent and check creep of rail
They are not attacked by vermin
Disadvantages Cast Iron Sleepers
They are prone to corrosion and cannot be used in salty formations and coastal areas
Not suitable for track circuited portions of railways
Can badly damage under derailment
Difficult to maintain the gauge as the two pots are independent
Require a large number of fastening materials
Difficult to handle and may be easily damaged
Lack of good shock absorber
They are expensive
Concrete sleepers
R.C.C and pre-stressed concrete sleepers are now replacing all other types of sleepers except to some special circumstances such as crossing bridges etc here timber sleepers are used. They were first of all used in France round about in 1914 but are common since 1950. They may be a twin block sleepers joined by an angle iron. It may be a single block pre-stressed type.
Advantages Concrete Sleeprs
Durable with life range from 40-50 years
They can be produced on large quantities locally by installing a plant
Heavier than all other types thus giving better lateral stability to the track
Good insulators and thus suitable for use in track circuited lines
Efficient in controlling creep
They are not attacked by corrosion
Free from attacks of vermin and decay, suitable for all types of soils
Most suitable for welded tracks
Prevent buckling more efficiently
Initial cost is high but proves to be economical in long run
Effectively and strongly hold the track to gauge
Inflammable and fire resistant
Disadvantages Concrete Sleepers
Difficult to be handled
Difficult to be manufactured in different sizes thus cannot be used in bridges and crossing
It is a component of permanent way laid transversely under the rails and performing the following functions.
To support the rails firmly and evenly
To maintain the gauge of the back correctly
To distribute the weight common on the rails over a sufficiently large areas of the ballast
To act as an elastic medium between the rail and the ballast and to absorb the vibrations of the trains.
To maintain the track at proper grads
To align the rail properly
2. Characteristics of Ideal Railway Sleepers
Initial cost and maintenance cost should be low
They should resist weathering, corrosion, decay and other deterioration
They should bear the wheel load efficiently and satisfactorily
They should maintain the correct gauge
They should absorb shocks or vibrations due to moving vehicles
It should distribute the load properly and uniformly over the ballast
Fastenings of rail with sleepers should be strong and simple
They should not break while packing of ballast
Weight should not be low or high
3. Types of Railway Sleepers
Depending upon the position in a railway track, sleepers may be classified as:
1. Longitudinal Sleepers
2. Transverse Sleepers
i. Timber / wooden sleepers
ii. Steel Sleepers
iii. Cast Iron Sleepers
iv. Concrete Sleepers
4. Treatment of Wooden Sleepers
Untreated railway sleepers are prone to attack by decay and vermin. The life of untreated wooden sleepers is thus very less. The life of untreated sleepers can be prolonged considerably by treatment. An extra life of 30-50% is estimated for treated sleepers over untreated railway sleepers.
The fibers of wood contain millions of minute cells containing juices. When these juices ferment, they lead to decay of timber. In the treatment process these juices are removed as much as possible and cells are filled with some preserving solutions may be an oil or some salt solution.
5. Railway Sleeper Density
The number of sleepers required to be placed under the track per rail length is called as its sleepers density.
It is generally given by the formula Sleeper density = n + x
