Article by LU ZHI-HONG, General Manager, Zhejiang YASHA Decoration Co., Ltd., BIM Center; Member, China Graphics Society BIM Committee; Deputy Editor of BIM Standards for Interiors and Curtain Walls, China Building Decoration Association.
When the 2016 G20 summit was planned to be held at the Hangzhou International Expo Center, Zhejiang YASHA Co., Ltd. took on the major project for the core meeting area.
This construction project involved dynamic designs, complicated construction techniques, a short timeframe, and special security requirements.
The overall design and construction work was very challenging, particularly the G20 main meeting hall.
The Building Information Modeling (BIM) team at YASHA used on-site 3D laser scanning, parametric modeling, streamlined design and fabrication, and other BIM techniques to help designers and project managers flawlessly complete their tasks and ensure the seamless construction of the G20 main hall.
Background and Goals for BIM on the Project
The Hangzhou International Expo Center is a landmark project for the city of Hangzhou. It was selected as the site of the 2016 G20 summit.
Because of the site’s special functions and the short construction timeframe, construction proved to be extremely challenging. Most difficult was the complicated design and high construction standards for the G20 main hall.
To address this challenge, our company began preparing our BIM technology well in advance of the project. Our company put forth its full effort, organizing designers, builders, and BIM personnel into a working group to employ BIM technology during the design and construction phases to ensure high standards. This allowed us to achieve our goal of high levels of quality, efficiency, and control.
BIM Software and 3D Laser Scanning Technology
Decoration is the last work process in a construction project. Quality problems or errors in construction, structure, or electrical or mechanical systems will have a significant impact on the design and construction of decoration elements.
To avoid these problems, our company used 3D laser scanners to gather as-built structural data, and then conduct reverse modeling to compare with the original design and quickly, visually, and accurately find construction errors.
On-Site Data Gathering and Reverse Modeling
Our first task when we begin a project is to conduct an on-site structural check. From our previous project experience, we have found that are varying levels of error between the construction design data and the actual project.
Because of this project’s special nature, our company immediately arranged an on-site survey using advanced 3D laser scanners to collect complete structural data.
We then conducted cloud-based data processing and reverse modeling to create a completely 3D digital model of the site.
With this data, we can develop a detailed decoration design based on a reverse model that is identical to the actual space.
Reverse Model-Based Design Analysis
After integrating the completed design into the reverse model of the site, we found serious discrepancies between the model and the construction drawings, resulting in a serious conflict between the steel structure and the design of drop ceiling.
The drop ceiling would be embedded in the steel structure such that the four-cornered eaves would extend beyond the steel structure by over a meter.
Proceeding with construction based on this original design was impossible. Our designers and builders held emergency consultations to find solutions. Since the project deadline was so close, it was impossible to conduct alterations to the steel structure.
After multi-stakeholder discussions, it was agreed to redesign and lower the drop ceiling to accommodate the existing structure.
Detailing and Optimizing Design Based on BIM
BIM has been widely recognized as revolution in the construction industry. Direct 3D design and delivery is the trend. Not only is this a technological revolution, it is more importantly a complete process innovation.
During the design phase, BIM models were created for the architectural, structural, and interior elements of the project. Decision-making based on intuitive 3D scenarios allowed the project to truly achieve visualized design, such as complex spatial relationships, perspective effects, and optimization of component shaping.
BIM enables “what-you-see-is-what-you-get” design, and allows designers to make the best decisions.
Visual Plan Selection
Because the north-most corner eaves faced the largest impact and had to be dropped by over a meter, the lead designer was very concerned about the visual effect on the final result.
As such, our BIM team used parametric modeling technology to make multiple adjustments to the curve of the drop ceiling. After comparing multiple plans, it was decided to abandon the original plan and instead drop all the corner eaves.
By increasing the curve of the drop ceiling, we were able to achieve an acceptable visual result without scarifying the net space. This plan garnered agreement from the project manager and owner.
Streamlining and Optimizing the Design
The BIM design process allows multiple designers to work collectively within the same model. It compiles relevant information, and enables better coordination between disciplines and between designers. It reduces inefficiencies and liberates designers from the endless revision process. This frees up time and energy to optimize, improve and check plans, thereby achieving streamlined design.
The Chinese-style eaves design had four beams, originally designed to be 600×900 arched beams. However, the project manager found that in the BIM model, the beams looked too bold. Using the BIM model, our team created design options of different sizes of beams.
After multiple discussions and adjustments, it was agreed to resize the corner beams to 600×600 and to make targeted adjustments to the bracket design.
The BIM design achieves shortcuts for fabrication design. During the design, we fully consider the process of fabrication and construction. In-depth BIM software models all the way out to process accuracy, and creates process data to ensure seamless information handover.
The G20 main hall included 352 rafters of varying sizes and shapes. When the shape of the drop ceiling had to change, so did the rafters. Because of the difference between the as-built steel structure and original drawings, frequent adjustments were made during the fabrication design process, which led to huge amount of shop drawing changes. As soon as the design was confirmed, data needed to be sent to the fabrication site.
A traditional design process would never satisfy this level of speed and accuracy, so we used CATIA, advanced parametric design software, for our work.
The main steps were:
- Draft the drop ceiling shape design
- Confirm rafter and corner beam cross-sections
- Bind the rafters and beams based on parameters and curved surface
- Automatically generate rafters and beams based on parameters to create drop ceiling
- Generate shop drawings for each rafter and beam using 3D model
- Use CAD markup and submit to fabricators
Using this parameter-based design plan, as soon as the surface of the drop ceiling was confirmed, the fabrication data for the rafters could be quickly produced. This greatly increased accuracy and improved links between design and fabrication.
Without parametric design software, creating and repeatedly adjusting designs on such a short timetable would have been impossible.
For this project, YASHA brought forward the most advanced technology and best talent. Based on complete on-site data, we created accurate and parametric designs, and used BIM models to provide design data, quantity take-off, and reasonable and feasible shop drawings.
Because of our use of advanced technology and stringent implementation, leaders from around the world could meet under the hall’s flying eaves to discuss global affairs and enjoy the ambience of Chinese architecture and the distinguishing features of southern China.
In the last few years, BIM software has taken off in China. Thanks to the 2008 Beijing Olympics and 2010 Shanghai World Expo, BIM software has begun to become widely used. But the use of BIM software in construction and interior design has come about relatively late.
With the successful completion of the G20 summit and the high-profile G20 main hall project, the use of BIM software in the construction and interior design industries is bound to grow.
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