VCD System for Post-Disaster Buildings
Challenges in Post-Disaster Building Design
Post-disaster buildings are required to be operational following a disaster, such as an earthquake or a large windstorm. Common Post-disaster buildings include hospitals, power generating stations, control centres, emergency response facilities, etc.
Non-Structural Damage Observed in Post-Disaster Structures in Earthquake
Following small and medium sized earthquakes conventionally designed structures can have distributed non-structural damage, so much so, that architectural features, partitions, equipment and services could be severely damaged resulting in closure and significant downtime following the earthquake.
Non-structural damage in hospitals in Turkey following the 2023 Turkey Earthquake [ref 1]
Structural Damage Observed in Post-Disaster Structures in Earthquake
Following large or extreme earthquakes, structural damage can accumulate in structural members, such as in conventional diagonally reinforced coupling beams in coupled core wall buildings, so much so, that if the building survives the earthquake it could still render the building a complete loss.
Structural damage in a 9-storey diagonally reinforced concrete coupled wall building following the 2011 Christchurch Earthquake [ref 2]
New NBCC-2020 Requirements for Post-Disaster Building Designs
Both of these outcomes are extremely problematic for health agencies throughout the world - In an effort to ensure operational continuity for post-disaster buildings such as hospitals, 2020 revisions to the National Building Code of Canada (NBCC) now require post-disaster buildings to remain elastic with less than 0.5% interstory drifts under seismic hazard corresponding to a 5% probability of exceedance in 50 years.
Achieving the targeted elastic response and drift requirements can be challenging for conventional design such as with reinforced concrete shear wall construction and other ductile systems with large R-factors.
Viscoelasic Coupling Dampers (VCDs) for Post-Disaster Buildings
Kinetica’s Viscoelastic Coupling Dampers (VCDs) have revolutionized the way high-rise buildings are being built. VCDs uses Viscoelastic (VE) material which was the first damping technology used in tall building construction in 1969, where it was implemented in the World Trade Center. Since then, viscoelastic material has evolved, and features higher damping and durability properties compared to earlier generations.
Key factors about VE dampers and Kinetica’s VCDs:
Over 50,000 - VE dampers in over 500 buildings for wind and seismic control.
Over 30,000 - VE dampers have been through multiple M6.5+ earthquakes.
VE dampers have substantial resistance to fatigue and aging.
VE Dampers have a usable life beyond that of the building. There is no expectation to monitor, maintain, inspect or service the dampers.
Multiple projects, with some dating back to 1992, have had periodic removal and retesting of dampers and have shown no change in damping material properties.
There has never been a VE damper replacement in 50+ years.
Now, Kinetica engineers have adapted the technology to provide an optimal solution for the seismic design of post-disaster buildings.
Viscoelastic Damped Coupled Wall System
VCDs are an excellent option for post-disaster buildings to meet the new NBCC requirements.
The system uses VE material which when sheared dissipates vibrational energy as heat. Under seismic or wind loads, VE material produces an elastic and viscous restoring force which reduces drifts, accelerations and loads on the building structure.
VCD Behaviour and Design
Large earthquakes cause shear deformations in VE materials adding supplemental damping to the structure, reducing loads, drifts and accelerations.
The energy dissipated is 100% recoverable and VE panels are undamaged. Under Maximum Credible Earthquakes (for example 2% in 50 yr loads) steel elements can be capacity designed and further protect the building structure.
Design Comparison
Conventional Reinforced Coupled Wall Design
As intended by the design, the bulk of the concrete beams are completely damaged requiring repair or replacement and may result in decommissioning of the structure
Viscoelastic Damped Coupled Wall Design
The bulk of energy dissipation has been in the absorbed in the VE material. Although unlikely, if there has been some degree of yielding in the steel beams that can be easily repaired.
Health Care Facility Case Study
A 11‑story post-disaster health care facility, 170 feet tall, with average floor area of 40,000sf. in Richmond, B.C. was designed according to the 2020 National Building Code of Canada. Because the facility is required to be a refuge for the community and 100% operational in the event of a rare seismic event it was designed with the VCDs coupling reinforced concrete walls.
Due to the large seismic demands, conventional design resulted in 6-large and significantly reinforced concrete coupled walls with deep diagonal reinforced coupling beams. The conventional design was very costly to build based on significant reinforcing percentages and challenging ductile detailing requirements.
The design was substantially improved by replacing all diagonally reinforced coupling beams replaced by the VCDs. The VCD design results in 25% reduction in RC wall thickness, 30% reduction in reinforcing steel in the lateral load resisting system as well as significant schedule improvement.
Reinforcing Profile Comparison
Conventional Reinforced Coupled Wall Design
Heavy diagonal reinforcements in the RC coupling beams as well as high reinforcing ratio required for the coupled wallss
Viscoelastic Damped Coupled Wall Design
VCDs connecting to steel beams that are embedded into walls with reduced reinforcing ratio as a result of reduced demands
Performance Comparison
Conventional Reinforced Coupled Wall Design
RC beams are designed to yield and dissipate energy. Following an earthquake there will be downtime to inspect, repair and replace those beams. Hospital will remain standing, but damage will be so widespread that the building could be a complete loss.
Viscoelastic Damped Coupled Wall Design
Damage-prone RC beams are replaced with Viscoelastic Coupling Dampers (VCDs). Energy mainly dissipated by damper with some possible energy dissipated in other structural members. No structural repair will be required of the VE damper panels.
Please Contact us to see how the VCD can be implemented in your project.
Ref1: Rapid report of seismic damage to hospitals in the 2023 Turkey earthquake sequences”, Qu. Z., Wang, F., Chen, X, Wang, X., Zhou, Z. Earthquake Research Advances, May 9, 2023.
Ref2: Kam, W. Y., Pampanin, S., & Elwood, K. (2011). Seismic performance of reinforced concrete buildings in the 22 February Christchurch (Lyttelton) earthquake. Bulletin of the New Zealand Society for Earthquake Engineering, 44(4), 239–278. https://doi.org/10.5459/bnzsee.44.4.239-278