Sprung instant structures and the fight against COVID-19

January 14, 2021

By David Thompson

In late 2019 to early 2020, COVID-19 took the world by surprise. It disrupted how people do business worldwide. Responding to the pandemic has opened doors for all businesses and industries (including the construction industry, consultants, and constructors) to be creative in their responses to new challenges.

The planning, design, and construction of hospital facilities normally take years. However, the pandemic presented a unique challenge where solutions had to be conceived and implemented within months. This is the story of one response to this unique challenge.

Photo © Andy Griffith[1]
Photo © Andy Griffith

Shortly after the World Health Organization (WHO) identified COVID-19 as a pandemic, and with the concerns raised by Canada’s early casualty projections, provincial governments realized the pandemic numbers could quickly overwhelm their health-care systems. More treatment capacity was required. Health regions identified a need for additional beds that could be housed in open wards. One solution was constructing a facility (an open ward) on a hospital’s parking lot and connecting it to the main building.  The site could be returned to its original use afterward.

Building firm Sprung Instant Structures[2], in conjunction with contractors, provided a solution in two provinces—Ontario and Alberta. The solution was a 15.24 x 45.7-m (50 x 165-ft) structure made with high-performance tension fabric with an adjustable floor system. The structure is able to accommodate between 70 to 100 beds with a 3-m (10-ft) connecting, enclosed corridor to the main hospital (Figure 1).

As of June 2020, four temporary facilities have been completed: the Joseph Brant Hospital, (Burlington, Ont.), Royal Victoria Regional Health Centre (Barrie, Ont.), Trillium Health Partners (Mississauga, Ont.), and Peter Lougheed Centre (Calgary, Alta).

The industries’ responses to COVID-19 demonstrated that, despite challenges, large hospital facilities can be constructed in days, not years.

Figure 1: Concept rendering of a COVID-19 structure. Photos courtesy Sprung Instant Structures[3]
Figure1: Concept rendering of a COVID-19 structure.
Photos courtesy Sprung Instant Structures

Ontario temporary facilities

The construction team consisted of BLT Construction Services, Mulvey & Banani Consulting Engineers, the HIDI Group, KTA Structural Engineers and Truetek Engineering Inc., Cumulus Architects Inc., and the owner’s representative Infrastructure Ontario, Colliers. These companies worked together to meet the diverse needs of their clients.

Two health centres required an infectious disease ward specifically for COVID-19 patients, and one of the two required a facility for use in the winter. Another centre required a ward for non-COVID-19 patients in order to free up regular hospital beds (Figure 2).

The construction team had to build on uneven parking lots. The structure is designed to accommodate changes in elevation. To create a level floor surface, an adjustable floor system was used. The structure was anchored to the ground using ballast weights and 20 x 300-mm (3/4 x 12-in.) steel pins. Two structures for COVID-19 patients used negative pressure. The two other structures employed static pressure. One structure was insulated for use during the winter, and two were left uninsulated to speed up construction.

According to Paul Waddell, vice-president, design and build, for BLT Construction Services, what made the project work well was “…the co-operation between all parties involved, including the owner’s representatives…the clients were satisfied with the quality of the facilities, especially considering the short time of construction.”

The Joseph Brant facility was designed, shipped, and constructed in 14 days. The Royal Victoria facility was completed on in 30 days. The Trillium Health Partners was completed in 24 days.

Figure 2: A COVID-19 ward at the Trillium Health Partners, Mississauga, Ont.[4]
Figure 2: A COVID-19 ward at the Trillium Health Partners, Mississauga, Ont.

Calgary temporary facility

In Alberta, the design/construction team consisted of CANA Construction, Stantec, Sprung Instant Structures, and KTA Structural Engineers. The size of the structure and the floor anchoring method mirrored the Ontario structures. However, this structure had to accommodate a site elevation slope of 900 mm (35 in.). A wood crib foundation was used to create a level working surface. As soon as the owner approved the project, construction and design began simultaneously. Alberta Health Services and Stantec completed the programming in three days (a project that involved 50 people including various user groups). For this project to be a success, there had to be co-operation and communication between all parties. This facility has static pressure, and it was left uninsulated to accelerate construction (Figure 3).

“The project was completed in 17 days from conception to turn over to the client, ahead of time, and under budget,” said Jim Avery, vice-president, Sprung Instant Structures. “The clients were surprised at the quality of the project.”

To achieve this schedule and prevent delays, daily onsite presence and attention of senior structural engineers was required. The real-time modification of structural systems and accommodation of alternative components and construction methods required in-depth knowledge of the structure’s behaviour. Having the manufacturer’s technical representatives onsite for the duration of construction helped ensure the quality and speed of construction (Figure 4).

Instant structure design and materials

All of the structures were fabricated at Sprung’s headquarters at Aldersyde, Alta. The design of, and the materials used in, the structures lend themselves to meeting the challenges of rapid design and construction. Waddell observed the structures had the most permanent features for an assembly occupancy in a temporary facility, and that the ones erected in Ontario met the requirements of the Ontario Building Code (OBC) and building envelope requirements.

Often, when people look at fabric structures, they assume them to be simple tents. Nothing is further from the truth. Present-day fabric structures are the result of years of research and development. The temporary structures described in this article can be used in all the Major Occupancy Classifications from Assembly Group A Division 1 to low-hazard industrial occupancies Group F Division 3.

SIDEBAR (Wide)

CONSTRUCTION SEQUENCE FOR PETER LOUGHEED FACILITY
Wednesday, April 8, 2020.

Day 1: Notification of start of work. Concept of foundation system. Materials delivered to site. Programming of facility started.

Day 2: Three senior structural engineers brought on to site (including a specialist with over 40 years’ experience in wood design) to verify the viability and enable the method of construction the construction manager wished to use. This meeting devised workable connection details and finalized wood framing concepts. Sketches provided for wood framing details. Analysis of Sprung structure.

Day 3: Six of 12 arches erected. Wood foundation 50 per cent completed. Redesign of foundation.

Day 4: All arches erected. Half of membrane installed. Programming completed. Modification of foundation anchorage.

Day 5: All membrane installed and stretched. Corridor started. South end installed. Modification of foundation to accommodate construction sequence.

Day 6: Flooring system started.

Day 8: Sprung structure completed except for doors. Corridor under construction. Floor system completed.

Day 10: Mechanical duct work being installed. Floor system and corridor under construction in the main building. Checked utility loads.

Day 11 to 16: Internal gas and electrical installed. Frame out of partitions. Mechanical units installed.

Day 17: Substantial completion (including beds and work stations) and turn over to hospital.

Structures are considered single-storey buildings or buildings with any height, as defined by the National Building Code of Canada (NBC). The temporary facilities erected at the hospitals were a “frame-supported structure—a structure consisting of a pre-stressed membrane cover that achieves and maintains its shape, strength, and stability through, and is supported by, an independent frame” as defined in Canadian Standards Association (CAN/CSA) S367-12, Air-, cable-, and frame-supported membrane structures. The structure consists of tensioned membrane materials (acrylic-coated polyvinyl chloride [PVC] fabric) interconnected and supported on a structural aluminum frame. They have been designed for ease of erection and dismantling, but require complex analysis and design.

The erected structures meet the requirements of CSA S367-12 and CSA S157, Strength Design in Aluminum, for environmental loads for wind, snow, and seismic criteria, as set out by a local authority. The wind forces on the structures are identified using wind tunnel experiments because of the unique shape and behaviour of the structure. The figures used in NBC’s structural commentaries require the designed building to have roof diaphragms. The values in Figure I-7 (CpCg) of the 2010 NBC Structural Commentaries (Part 4 of Division B are not appropriate for the design of structures without diaphragms, such as tension membrane structures and buildings using cabling for lateral support. The CpCg values from Figure I-7 were developed based on the building moving as a rigid body.

Figure 3: Day 4 of construction at the Peter Loughleed Centre in Calgary, Alta.[5]
Figure 3: Day 4 of construction at the Peter Loughleed Centre in Calgary, Alta.

The membrane is considered non-rated or combustible; the aluminum frame does not burn and can be categorized as non-combustible. Third-party testing has confirmed the membrane has a flame spread of 25 or less and a smoked developed index of 450 or less. The membranes have been tested to Underwriters Laboratories of Canada (CAN/ULC) S109, Standard Method for Flame Tests of Flame Resistant Fabrics and Films, and CAN/ULC S102, Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies, as outlined in (NBC, the 2019 Alberta Building Code, the 2012 Ontario Building Code, and CSA S367-12. The membrane also meets the requirements of National Fire Protection Association (NFPA) 701, Standard Methods of Fire Tests for Flame Propagation of Textiles and Films, and ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials.

From a building envelope viewpoint, the membranes have water vapour permeance between 21 to 38 ng/(Pa·s·m2), and the membranes are designed to be strong enough to resist wind pressures.

The exterior membrane and liner are always kept in tension and are attached/integrated into the arches by a compression connection. The envelope assembly shown in Figure 5 forms a continuous and tight barrier.

In 2010, full building testing of a similar structure was completed in the United Kingdom. The testing followed the English standard BS EN 13829:2001, Thermal performance of buildings. Determination of air permeability of buildings. Fan pressurization method, and showed air leakage (air permeance) of less than 2.01m3/h.m2 (0.56 l/m2sec). Improvements on the air leakage has been made since the testing was done.

The insulated envelope assembly not only provides an excellent environment barrier, but it is robust. The assembly has been tested and accepted by the Miami-Dade County, Florida, Product Control division, as complying with the requirements of the High Velocity Hurricane Zone (HVHZ) of the Florida Building Code.

Figure 4: The completed structure for the Peter Loughleed Centre after 17 days of construction.[6]
Figure 4: The completed structure for the Peter Loughleed Centre after 17 days of construction.

Project delivery method

The four projects were completed using multiple project delivery methods. The projects in Ontario were completed using a design/build delivery model, a construction management method, and a hybrid between design-build delivery and construction management using CCDC-2 as the contract form. The project in Calgary was completed using a construction management model with the foundation design as a delegated design. Due to the speed and uniqueness of the projects, no formal project manuals were produced. However, the structural work completed on the projects could have been covered using performance specifications in the following sections:

Project challenges

Not surprisingly, even with proven materials and design methods, projects in two provinces in the midst of a pandemic, while responding to unique design and construction needs, presented some challenges.

While the materials could be fabricated and shipped easily within Calgary, the same was not true for the Ontario facilities. With air traffic halted, the Ontario materials and personnel were trucked across country. All consultations were handled through a variety of phone calls and video conferencing, with a local engineering firm working with KTA Structural Engineers on the Ontario site inspections.

With the Calgary structure, the challenges were to accommodate the 900-mm difference in the slopes of the parking lot. A daily challenge was the need to use alternative materials and construction methods. As there are utilities under the parking lot, anchorage had to be shallow to prevent the piercing of the fibre-optic network.

Figure 5: Insulated envelope of sprung structure.[7]
Figure 5: Insulated envelope of sprung structure.

During construction, infection control had to be observed. Social distancing does not work well on a construction site. CANA adjusted its usual work habits by working 24/7 with workers coming on for 12-hour, staggered shifts to reduce the number of people onsite at any one time. Specific personal protective equipment (PPE) was available for all personnel, including N95 face masks and gloves in addition to regular construction safety equipment. Not only did workers have to have the requisite knowledge, skills, experiences, and tickets, they also had to be trained in infection control/safety protocols.

Weather during construction was not always compliant, and all sites had to deal with rain, wind, snow, and sub-zero temperatures which would normally cause delays, but not in the case of these projects.

Post-COVID-19 use

When the COVID-19 crisis has crested and the temporary facilities are no longer necessary, they can be sanitized, dismantled, stored, and reused. All major components of the facility can be reused, including the aluminum members, the membranes (which were stressed only to a certain level so they could be reused), the adjustable flooring, and the lights and mechanical units. The modular partitions can also be repurposed. The only components that cannot be reused are the bolts.

Conclusion

COVID-19 has presented unique challenges and opportunities. These temporary facilities demonstrate the construction industry can rise to the occasion. With the will and co-operation of all parties, rapid design, fabrication, and construction are possible. Temporary facilities, in time of crisis, can be constructed in weeks rather than years.

[8]David Thompson is a principal at KTA Structural Engineers Ltd of Calgary, Alta. He has been a professional engineer for more than 35 years with over 25 years of experience in the design of tension membrane structures in 55 countries. He was a member of the Canadian Standards Association (CSA) committee for CAN/CSA S157, Strength Design in Aluminum/Commentary on CSA S157-05, Strength Design in Aluminum Design of Aluminum Structures, and he serves as a member of ASCE Standard Committee for ACSE-55 Tension Membrane Structures. Thompson has been a member of CSC since 1990 during which he served on the Canadian Construction Documents Committee for 10 years representing the Association of Consulting Engineering Companies. He can be reached at dpt@kta-eng.com[9].

Endnotes:
  1. [Image]: https://www.constructioncanada.net/wp-content/uploads/2021/01/Joseph-Brant.jpg
  2. Sprung Instant Structures: https://www.sprung.com/
  3. [Image]: https://www.constructioncanada.net/wp-content/uploads/2021/01/Concept-2.jpg
  4. [Image]: https://www.constructioncanada.net/wp-content/uploads/2021/01/Reality.jpg
  5. [Image]: https://www.constructioncanada.net/wp-content/uploads/2021/01/Peter-Lougheed-Day-4.jpeg
  6. [Image]: https://www.constructioncanada.net/wp-content/uploads/2021/01/Peter-Lougheed-Day-17.jpeg
  7. [Image]: https://www.constructioncanada.net/wp-content/uploads/2021/01/Peter-and-david-for-engineering-aricle.jpg
  8. [Image]: https://www.constructioncanada.net/wp-content/uploads/2021/01/Dave-Picture.jpg
  9. dpt@kta-eng.com: mailto:dpt@kta-eng.com

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