Erection-based construction planning for panelized building: Case Study
Erection-based construction planning for panelized building: Case Study
Erection-based construction planning for panelized buildings is a technique to optimize the sequence and timing of erecting pre-fabricated modules or panels to streamline the construction process (Staub-French et al., 2022). Erection-based construction planning is seen in the construction of the "Brock Commons Tallwood House" at the University of British Columbia in Vancouver, Canada. The construction was started in 2015 and was completed in 2017; it is an 18-story student residence, and at that time, it was the tallest mass timber hybrid building in the world. Mass timber is a sustainable building material manufactured from wood layers that are stacked and glued together, and it provides several environmental and structural benefits. Wood is a renewable source of energy and the construction process has less carbon footprint relative to steel and concrete buildings. The project team implemented an integrated design process supported by the consumption of virtual design and construction (VDC) modeling. The critical factors for the project's success are planning and sequencing of construction activities, thorough prefabrication of the building structure, and precise on-site erection and installation coordination.
The dimensions of this building are discussed as follows
Parameter Value
Height 53 m (18 storeys)
Site Area 2,315 m
Gross Area 15,120 m
Footprint 15 x 56 m, totaling 840 m
Typical Floor-to-Floor Height Ground Floor: 5 m, Upper Floors: 2.81 m
CLT Panels per Floor 29 panels/floor, 169 mm thick, 285 mm wide, changing lengths (600, 800, 1000, and 1200 mm)
Columns per Floor 78 columns/floor
In the case of the Brock Commons Tallwood House, the construction process was planned to optimize the erection of prefabricated wooden panels and modules. The building structure primarily consisted of cross-laminated timber (CLT) panels and glue-laminated timber beams. The construction team uses a just-in-time delivery approach, where components and panels are manufactured off-site and delivered to the construction site precisely when required. It implies that the elements of construction, such as the prefabricated CLT and glulam panels, were constructed off-site and delivered to the construction site when needed. It lessened the handling of material and storage on-site, lessening congestion and getting better safety.
The majority of the elements of the building, such as sections of the floors, walls, and even the iconic staircase of this building, were prefabricated off-site. These prefabricated components fit together in a precise way, lessening the requirement for on-site cutting and adjustments. The Brock Commons Tallwood House is a hybrid construction project which means it joins multiple building materials and systems. While the main structure is constructed of mass timber, the building also has a concrete podium and steel connectors for fire resistance and stability (Pilon et al., 2018).
The erection process for the building was carefully planned to reduce on-site construction time and reduce the disruption to the surrounding area. This strategy expedited the construction schedule, lessened the environmental impact, and improved safety on-site. The erection process was finished in just sixty-six days per floor, which was a major achievement for a building of this complexity and height.
The foundation of the building, ground floor, second-floor slab, and stair/elevator cores are made from reinforced cast-in-place concrete. The second-floor slab is a transfer slab, shifting upper-level mass-timber structure weight to the lower-level concrete structure. Moreover, these cores and the foundation lead to the structural stability of the building, allowing it to withstand lateral forces from seismic and wind activity.
Stringent risk management and safety protocols were implemented during the construction of Brock Commons. Comprehensive water and fire management plans were established, underscoring safeguarding the mass-timber components. A safety officer had an active role in planning the construction.
The major strategy involved enclosing every floor in the structure of the building shortly following the erection of the mass timber framework, ensuring minimum timber exposure. Prior to the enclosure, reusable guardrails and fall protection systems were applied to secure workers on open floors. The other protective measures are
Encapsulation of the mass-timber.
Installation of sprinkler standpipes in concrete cores.
Preventing welding or hot work after the mass-timber was in place.
Maintenance of a high level of site cleanliness.
Less storage of material to prevent fire hazards.
Workers were imparted with fire prevention and response training, and the site access was limited and carefully monitored.
The issues of complex and small construction sites were addressed through meticulous planning, the aim is to limit the presence of many trades and materials at any given time. Prefabrication methods moved a considerable portion of construction tasks to controlled factory environments, letting critical work be completed indoors instead of at elevated heights on the construction site. This strategy also lessened the influence of work stoppages because of adverse weather conditions (such as operations of cranes being halted) and reduced noise related to construction and campus disruptions (Kasbar, 2017).The Brock Commons Tallwood House project budget was $51.5 million in Canadian dollars. $3.8 million was assigned for design expenses, though the construction phase costs $40.5 million, equal to $248.90/ gross square foot. Structural elements, such as concrete, mass timber, and steel connections, comprise approximately 20% of the expenditure. The primary cost contributors to the budget were the building envelope, mechanical and electrical systems, and finishes. These systems, which operate independently from the building's structure, accounted for nearly half of the total construction costs.
This project grabbed considerable attention in the construction industry and got numerous awards for design, innovation, and sustainability. It lead to the growing interest in tall timber construction all over the world and determined the feasibility of building tall structures with wood.
References
Kasbar, M. 2017. Investigating the Performance of the Construction Process of an 18-storey Mass-timber Hybrid Building (T). University of British Columbia. Retrieved from https://open.library.ubc.ca/cIRcle/ collections/24/items/1.0347252
Pilon, A., Teshnizi, Z., & Lopez, D. (2018). An Overview of the Construction of a Tall Wood BuildingBrock Commons Tallwood House.New Zealand Journal of Forestry,63(1), 3-10.
Staub-French, S., Pilon, A., Poirier, E., Fallahi, A., Kasbar, M., Calderon, F., ... & Froese, T. (2022). Construction process innovation on brock commons Tallwood house.Construction Innovation,22(1), 1-22.
