VR/AR-based Smart Construction Simulation Technology
▲ Senior Researcher Seo Myung-bae, Department of Future Technology and Convergence Research
Construction Meets Virtual Reality Technology
In 2018, the Korean Ministry of Land, Infrastructure and Transport (MOLIT) announced the "Smart Construction Technology Roadmap” that can increase productivity by applying the latest ICT technology covered by the Fourth Industrial Revolution to the construction field. This was a move to enhance the competitiveness and safety of construction sites. In recent years, Korean construction sites have faced a number of issues that include an aging workforce, shortened working hours, and a sharp decrease in the number of skilled workers. As such, there was an urgent need to come up with response strategies to tackle these issues. Ultimately, this roadmap encompasses the government's will to dominate the future market while investing in innovative growth in construction by applying cutting-edge ICT to the construction field. Smart construction technology is technology that incorporates 3D modeling technologies, such as BIM (Building Information Modeling), drones, robots, IoT, big data, AI, VR/AR, and mobile, into construction (Figure 1).
In the last 20 years, the development and application of high-performance materials in the construction field have been increasing. Recently, carbon fiber has been introduced as a replacement material for rebar or rebar mesh. The thickness of carbon fiber is about one-tenth that of human hair, but it has a tensile strength ten times stronger than iron. The biggest advantage of carbon fiber as a construction material is that it is noncorrosive. From 10,000 to 50,000 carbon fiber filaments are gathered to form a bundle with a diameter of 2 to 5 mm; with this bundle, a textile grid reinforcement having a grid shape with an interval of 2 to 4 cm can be made. A textile grid can be used as a reinforcement for concrete or mortar, and when mortar is used as a binder, it is called TRM (Textile Reinforced Mortar) (Figure 1). Since the coating thickness required to secure durability is not necessary for the TRM design and construction due to the non-corrosive nature of the textile grid, it has the advantage of being able to construct very thin structures.
In the construction field, the use of BIM (Building Information Modeling), a three-dimensional information model, is becoming compulsory. Based on this, the demand for a new market combining VR/AR/MR technologies and advanced sensor devices is increasing. In 2016, GS E&C presented the optimal construction method using BIM-based on-site equipment simulation, beating leading construction companies around the world and winning the contract to build a vehicle depot in Singapore worth KRW 1.7 trillion. Since virtual construction simulation technology can be used for the review of the design, constructability and maintenance by multiple stakeholders including the client, the contractor, the designer, and the civil petitioner, there is high potential for innovation in the existing construction process. It can also be used as digital twin-based technology by linking to smart cities. In addition, virtual reality technology can be developed into user experience and experience-based technology rather than simply being visually utilized. Based on this, it is highly probable that it can be utilized for legal review, safety review, design certification, and virtual construction. The ultimate purpose of virtual construction technology is to enable an improved level of productivity and quality in the construction industry based on process innovation, and to support the base technology of the construction industry through various simulations and decision-making.
How VR/AR-based Smart Construction Simulation Technology is Being Utilized at Home and Abroad, and its Current Status
In practice, VR (Virtual Reality) technology is highly likely to be utilized in the design stage, while AR (Augmented Reality) and MR (Mixed Reality) technologies are highly applicable in the construction and maintenance stage. For example, the US-based AECOM and the US-based Marquette University utilize VR technology for decision-making in the design stage, such as building design, urban design, and road design, while the Finland-based VTT and the US-based Bently mainly use AR technology in the construction and maintenance field. In addition, it was found that VR-based disaster/disaster simulation, which is centered on Japan, and AR and MR, which is centered on private companies, are being used in the education and collaboration fields (Figure 2).
Why Is the Application of VR Technology Slow in the Construction Field, and How Can this be Resolved?
In Korea, there are various examples of VR technology being applied to the construction field. But there are not many cases in which it is actively applied to work, such as to support the client's decision making, to win a project contract, or by large construction companies in cyber model houses for publicity and sales. Recently, as BIM has been actively used, the number of cases of simple design review using VR tools compatible with BIM modeling authoring tools are increasing. But still, these are just at the prototype level. The research team conducted various virtual construction simulation experiments using a three-sided large virtual demonstration mockup laboratory, which was built at the KICT (Korea Institute of Construction Technology) in 2016. We learned that the additional work required to carry out various simulations when BIM drawings, which are 3D drawings actually used in construction, are projected to the VR environment, is quite time-consuming. Ultimately, the market is not being vitalized despite the fact that VR technology brings great effects when it is applied to construction. This is because it takes a lot of manpower and time to produce good quality VR content, and thus economic efficiency is not secured.
Therefore, this research team developed, based on BIM, a 3D model in the construction field, the best practice simulation that maintains the same quality when converted into a VR simulation while reducing the cost by shortening the time required to create the simulation compared to the conventional model. It has the best effect when the VR technology is utilized in the construction field rather than simply in the design review, interference check, and construction review. As a result, we conclude that it is possible to develop a new market if the effect of the VR technology is verified through field application, and related research was conducted to solve this issue (Figure 3).
Improving the Productivity of VR Content Production, the First Step in Vitalizing Virtual Construction
In creating VR content using the BIM model, if you simply want to create it with flat-based VR technology on a monitor rather than at a high level of quality, you still can do it with a simple tool. However, as users' expectations are rising with the advancement of technology, a lot of manpower and time is required to implement a realistic simulation with high immersion using VR HMD (Head Mounted Display) worn on the head. In fact, based on a 200 mega-scale plant facility, it was found that it took about 3 months to analyze the raw data, lighten the data, and optimize the object in order to produce content that meets the requirement of 120 FPS (Frames Per Second). 120 FPS is the minimum requirement for a realistic simulation that does not produce dizziness for the viewer.
In this study, to reduce the time and cost of implementing high-quality BIM data in a VR environment, we have developed an attribute lightweighting algorithm that reduces the physical data volume and automatically removes unnecessary BIM attributes to reduce the time required to convert existing BIM data to VR (BIM to VR). We also developed an auto material technology that can reduce manual work by extracting BIM model attributes and automatically mapping the most used textures (materials) in the construction field to create high-quality content based on a blank 3D model with nothing on it. The related core technology was transferred to a private company and was used to produce actual VR contents for Hyundai E&C. In addition, to verify this technology, a test was conducted based on 10 files of 200 mega-size. In the case of material mapping, the time taken was reduced by 50% compared to the conventional technology, and it was certified for its performance by the TTA (Telecommunications Technology Association) in March 2020.
Virtual Construction Simulation Platform, Best Practice Development, and Field Application
To vitalize virtual construction, it is very important to produce optimal contents that allow the various stakeholders including the client, designer, and construction company to actually feel the effect and verify the effect through field application. Therefore, at the beginning of the study, the optimal simulation contents were seriously considered for various stakeholders, and the simulation was developed in consideration of the public nature, urgency, and ripple effects due to the special nature of KICT (Korea Institute of Construction Technology) as a public institution. Since VR technology has strength in preliminary review based on 3D model, fire and noise simulation contents were developed. For fire simulation, the ignition source location and size of the fire can be adjusted at will, and the 3D model attribute information is linked to simulate the speed at which the flames spread. This technology can be used for future user experience-based firefighting design. In addition, by developing a noise simulation with visual effects, contents were developed that can support a response to complaints in the future (Figure 5).
AR and MR technologies can be used for facility maintenance and performance assessment in the field. In this study, the technology for AR-based railway facility performance assessment, AR-based tunnel facility maintenance, MR-based fire OJT (On-The-Job-Training), landscape review, and equipment remote control was developed. By actually applying these in the field, their potential was verified (Figure 6, 7).
Although BIM drawings are required for these simulations, a simulation platform was developed using FBX, a 3D neutral file format, considering that there are various authoring tools for creating BIM. FBX file was imported, the data weight reduction and auto material were run, each simulation is made as an add-in type plug-in, and then only base attributes (fire and noise level, location of the user, etc.) are set and mounted on the drawing. It was created in the form of a platform to enable simulation in various environments (Figure 8, 9).
To verify the core simulation technology developed in this project, the effectiveness of the technology was verified by applying it to the city of Goyang, Seoul Metro, and the Daegok-Sosa Zone 4 complex tunnel site. In addition, as part of the effort to advance into overseas markets, we signed an MOU with Tanal Group, a company owned by the Prince of Saudi Arabia, in February 2020 to apply BIM to VR core technology in the Saudi new city development project (Neon City). Discussions are also ongoing for the establishment of a local research institute, joint research, and core technology transfer.
Through this study, a productivity improvement technology for VR simulation content production to revitalize the virtual construction market, the development and field application of seven best practice cases, and technology transfer of core technologies to private companies were carried out. AR/VR/MR convergence technology in the construction field is a non-contact core technology that can respond to COVID-19 and is expected to grow explosively in the future. It is expected that it will be necessary to conduct additional studies from various angles, such as securing technological competitiveness and preoccupying the future construction market, developing additional success stories, researching applicable fields, discovering business models, and providing institutional support to revitalize the related industries. In addition, it is considered that smart construction virtualization simulation research can be used as a base technology for pioneering new markets in the future because it will allow the temporal and spatial constraints of the conventional construction industry to be overcome, and economic efficiency, diversity, and practicality to be secured.