- SPECIAL REPORTS
- THE MAGAZINE
As engineers and architects experiment with new transportation and building methods, taller and more innovative structures require more documentation. Monitoring a project in real time addresses the whole and the sum of its parts. Engineers and architects are now applying analysis-friendly technology to building design. The most sophisticated of these tools deliver immediate and continuous feedback on a far greater range of characteristics than traditional design tools. Material quantities and properties, energy performance, lighting quality, site disturbance, and what-if comparisons between new construction and renovation are some types of information that are easily available.
This approach to building design is so different from using conventional CAD that the industry has a separate name for it: building information modeling (BIM). In the last few years, BIM has become a successful and proven project delivery system in the vertical construction industry.
The movement to BIM began in 2006, when Caesars Palace in Las Vegas announced its ambitious $1 billion expansion and upgrade to the famed resort, and turned to BIM processes to document more than 41,000 square feet of above-ceiling space. When the largest producing power plant in the United States, Palo Verde, needed documentation to address safety concerns, 3D laser scanning and BIM were used to capture more than 2.6 million cubic feet. And when the General Services Administration (GSA), the largest landholder in the United States, needed inventory and documentation of its more than 8,700 buildings, BIM was the chosen technology.
“The learning curve is behind us in understanding point cloud data,” says Michael Frecks, president and CEO of Omaha, Neb.-based Terrametrix LLC., which provides terrestrial mobile LiDAR scanning (TMLS) services and has been involved in laser scanning since 2000. “The combined use of static and mobile LiDAR techniques can be a big benefit in certain environments, especially with the fast-developing indoor mobile applications. These two different techniques complement one another and can significantly reduce field data acquisition time.”
The time savings is a particular benefit for occupied buildings, as well as for office parks with multiple buildings and supporting infrastructure.
The use of laser imagery to produce “living” 3D building diagrams is an exciting application with the potential to save lives, protect property and maintain vital infrastructure. This technology involves laser imaging to “photograph” a structure floor by floor, with subdivisions, horizontal and vertical openings, and building service areas and objects made clearly visible. The highly graphic depiction of the structural features, occupancy and contents can take the viewer inside the structure to see the building in more meaningful detail than with the naked eye. Other facilities such as bridges, tunnels and industrial processes can be depicted as well.
Managing a project through its lifecycle requires a succession of strategies that can only be successfully implemented with accurate information and documentation. Piloting activities within services requires addressing the needs of trade consultants, architects, lawyers, auditors and insurance companies through communication, visualization and software applications. Being able to identify the activity of a project in real time through the use of 3D/4D laser documentation and scanning enhances performance-based engineering, computational mechanics, design construction integration, reliability and risk analysis for hazard mitigation, LEED issues and engineering informatics.
Documenting the completeness and correctness of information about every step in the process chain provides traceability, which is extremely valuable to an organization. Creating a transaction “footprint” enhances productivity, facilitates trade, improves quality of life and helps promote quality assurance. Organizations like The National Institute of Standards and Technology (NIST) and American Society for Testing and Materials (ASTM) allow comparisons of known standards that adhere to required accuracies. As views of measurement become more sophisticated, as national and international calibration bodies struggle toward organization, and as the regulation of quality assurance assumes a more prominent role in domestic and international trade, there is increasing interest in the objective validity of measurements at all levels.
From the preparedness and planning phase, to the training and drill cycle to actual utilization during an incident, BIM is creating a safer environment for employees, business partners and the local community. In pre-incident planning, vital building information can be recorded and used to formulate response procedures and identify specialized tactics that may be needed. Potential avenues of fire and smoke spread and propagation of chemical or biological agents can be identified. Areas for positive pressure ventilation can be preplanned. Probability estimates are vital. Having a clear sense of the probability of an event in a virtual world can help managers address a situation proactively in the real world.
Data integrity is an increasing area of concern. Collecting field data and developing areas of vulnerability are cumbersome to the insurance industry. The exact size of an area affected by an incident is difficult to identify if the data is not sound. “An independent technical review (ITR) is a key process in the quality management system (QMS),” says Kourosh Langari, senior transportation engineer with URS, a worldwide engineering, construction and technical services organization. “It is a documented critical review performed by a qualified individual who is not the originator of the work product being reviewed. The purpose of an ITR is to validate the assumptions, judgments, opinions, conclusions and recommendations within work products such as proposals, cost estimates, letters, memoranda, design documents, plans and reports.”
An ITR must be completed before a work product is delivered to a client and should validate that:
• The client’s contractual requirements are met
• Valid technical approaches and procedures are used
• Professional standards of care are met
• Ideas are expressed clearly and accurately
In training, 3D depictions can help building managers and emergency responders become familiar with the structure and develop tabletop simulations and response scenarios. The availability of graphic diagrams is invaluable in the tactical phase of an incident. Access points can be determined, entries visually rehearsed, and escape or shelter areas identified. In the event of a structural collapse, the pre-collapse status of the building could be a major asset in tactical planning and operations. BIM also provides the ability to automatically synch real-time digital photographs to the laser depiction to convey actual fire/collapse conditions. Obtaining accurate as-built information during construction increases safety and leads to lower insurance costs.
Typical BIM projects have involved the initial measurement of available space, measurement of the fabricated units and positioning of the units within the space. A variety of proven measurement techniques have been employed using specially calibrated instruments in order to achieve the required precision.
Instrumentation includes static and mobile 3D laser scanners, calibrated total stations and electronic levels. Laser scanning and related nondestructive measurement technologies have proven to be cheaper, better and faster than traditional surveying and other measurement techniques. In many circumstances, because laser scanners produce extremely robust data that is virtually a complete record, they are more accurate with measurements to very small units. 3D laser scanning can provide an unobtrusive, noncontact data capture method in dangerous or difficult-to-access environments. It collects geometry that could not otherwise be obtained by architects and is a foundation for BIM models.
However, more important than the instrumentation is the experience of the surveyors and technicians with this type of work and their understanding of precision measurement within a 3D environment. All construction system monitoring or measurements of elements of interest must have an accuracy of +/-¼ inch to a level of certainty of one standard deviation. In some cases, greater accuracies, precision or levels of detail are required on certain areas of interest.
Environmental concerns and rising energy costs will continue to drive the building industry toward sustainable design. BIM, supported by appropriate software like Revit, Archicad, Bentley Architecture, and Vectorworks, has the information power to reduce the cost of sustainable design, allowing analysis and certification throughout the lifecycle of the project.
As firms begin to understand the capabilities of BIM to support every stage of the project life cycle--from inception through start-up and operations to decommissioning and closure--they are sparking a new movement that is spreading the value of BIM to an even broader range of clients. “The profession has modified the term to transportation information model (TIM),” says Langari. “The TIM concept uses the geographic information system (GIS) as the cadastral fabric for wide area viewing and cartography. As one gets closer to the reference line of the transportation corridor, technologies like terrestrial mobile LiDAR scanning will fill in the gap for subcentimeter accuracy.”