Strength, stiffness, or deformation capacity: What makes a building more resilient?

SE Literature Café (4)

A quick look at Joyner, M. D., & Sasani, M. (2020). Building performance for earthquake resilience. Engineering Structures, 210, 110371.

Seismic resiliency is a system problem where all system components should perform well: buildings, the water and electricity infrastructure, and the road networks that connect these systems. From a structural engineering perspective, resiliency starts from building better structures.  But how can an architecture-engineering-construction (AEC) team do that?

Following codes requirements and engineering intuition, the structural engineer makes decisions that balance stiffness, strength and deformation capacity of building components, and consequently the building. Stiffness helps reduce damage to partitions and façade (AKA non-structural members) and reduces stories displacement under an earthquake.  Historically, strength is an essential requirement of building codes. All building members need to meet certain thresholds, which leads to the building’s overall strength. Finally, deformation capacity (or ductility) is the ability of structural members to deform without being damaged, which is vital for both repair cost and functionality.

An AEC team that wants to design a more resilient building needs to make many decisions. Yet, the outcome of these decisions on building resiliency is not well-understood. Should they increase the reinforcement ratio of all beams to get better strength? Or should they add shear walls at lower stories to increase the building stiffness? Or maybe they need partial height partitions with added deformation capacity?

What is this paper addressing?

The relationship between design and resilience-based measures such as repair cost and functionality

A quick wrap-up of the results

  • Increasing stiffness was more effective to reduce repair cost
  • For building functionality, the results depend on the building period of vibration: stiffness was more important for short-period buildings, whereas strength is more critical for long-period structures
  • Increasing deformation capacity was not as effective as the two other measures.
Comparison of the effect of increasing stiffness (T0/T) and strength (Vy/Vy0) adopted from Joyner and Sasani

What I like about this paper

Scientific clarity for a complex topic: The paper delivers a clear insight into the underlying relationship between seismic design and seismic resiliency. Also, it nicely explains the concepts of stiffness and strength, and their practical implementation in the design (see Sections  3 to 7 of the paper).

Additional resources

Mosalam, K. M., Alibrandi, U., Lee, H., & Armengou, J. (2018). Performance-based engineering and multi-criteria decision analysis for sustainable and resilient building design. Structural Safety74, 1-13.

Arroyo, O., Liel, A., & Gutiérrez, S. (2021). Practitioner-friendly design method to improve the seismic performance of RC frame buildings. Earthquake Spectra, 8755293020988019.

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