SE Literature Café (2): A party of four: resiliency, sustainability, hybrid simulations, and retrofitting non-ductile concrete frames

A quick look at the article: Hashemi, M. J., Al-Attraqchi, A. Y., Kalfat, R., & Al-Mahaidi, R. (2019). Linking seismic resilience into sustainability assessment of limited-ductility RC buildings. Engineering Structures, 188, 121-136.

A kind of intro

Non-ductile concrete frames (read old frames that were not really designed for earthquakes) are in the spotlight of resiliency assessments. Often these types of studies aim to understand what happens to these structures if the big one occurs. To answer this question,  numerical structural models are coupled with probabilistic models. This  coupling links impacts (what earthquakes do to the building), exposure (what you can expect from the site in terms of earthquake intensity), and consequences (what those impacts do to humans, the economy, etc.)

Let’s say we evaluate these structures and *surprise* we find out that the risk is too high; what now? Naturally, structural engineers love to retrofit these structures to lower the risk.  To ensure the risk is actually low, the SE scholars simulate retrofitting in their computer and calculate some measure, compare it to the original structures, and can figure out if (or how) the retrofitting was a success.

One of the most famous retrofitting methods is using fiber-reinforced polymer (FRPs), which are made by embedding tough fibers in a resin.  While FRPs have been used for some time now, not many quantitative studies evaluate their impact from a building perspective.

What is this paper addressing?

A holistic look at FRP retrofitting effect on non-ductile concrete frames from an economic, environmental, and hazard performance perspective

Quickly, wrap up the results. I have 2 minutes tops

Repairing with CFRP improves buildings under the major damage state and has a slight impact on collapse and negative impact on minor damage stages!

Comparing probability of exceeding (a) minor (b) major (c) collapse damage for repaired and initial structure! picture From Hashemi et al (2019)

The authors then only calculated loss for structure with FRP repairs and concluded that downtime has the highest contribution to normalized Expected annual loss (normalized to total reconstruction). Interestingly, collapse is quite important for CO2 emission and energy consumption, whereas non-structural components dominate downtime and cost losses!

annual loss across different performance measures as a percentage of building reconstruction for repaired building. (e.g. 1% means each year the cost of that decision variable is about 1% of price of rebuilding the structure!) Picture from Hashemi et al.

What I like about this paper

This paper is a prime example of combining the best of both (here trio) worlds to tackle a complex question. The beautiful balance of rigorous experimental work and numerical simulation is something of beauty ( The numerical models are calibrated based on hybrid 6-DOF simulations)

I’m hooked. Give me some more related papers

FRP retrofitting from the global building performance perspective

Harrington, C. C., & Liel, A. B. (2021). Indicators of improvements in seismic performance possible through retrofit of reinforced concrete frame buildings. Earthquake Spectra37(1), 262-283.

Tarfan, S., Banazadeh, M., & Zaker Esteghamati, M. (2019). Probabilistic seismic assessment of non-ductile RC buildings retrofitted using pre-tensioned aramid fiber reinforced polymer belts. Composite Structures208, 865-878.

Aliasghar-Mamaghani, M., & Khaloo, A. (2019). Seismic behavior of concrete moment frame reinforced with GFRP bars. Composites Part B: Engineering163, 324-338.

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