How Do We Best Prepare for Disaster?

20 May 2021

Repair – Rehabilitation – Retrofit: How Do We Best Prepare for Disaster? Originally published on LinkedIn by Ashish Sapre, Engineer at Walter P Moore Diagnostics.


All structures grow old and need periodic maintenance, whether the issues are structural or non-structural. While the latter addresses components that improve our living conditions—like electrical systems, plumbing, wall paint, etc—structural maintenance is meant to enhance the strength and durability of the buildings we inhabit or infrastructure we use.

When we think of urban or national development, we tend to focus on the creation of new structures. But at any given point, structures that need maintenance will always outnumber new construction projects. This is true for buildings, bridges, and any other infrastructure we encounter daily. Additionally, a structure may face several disasters during its lifetime, e.g. cyclone, flood, earthquake etc. Every disaster—low or high intensity—deteriorates structural strength and reduces the resiliency of our built environment.

So we need to focus on maintaining aging structures to best address our present needs and prepare for the imminent disasters we will face. Typically, we talk about structural maintenance more commonly as repair, rehabilitation, or retrofitting. Though these terms are often used interchangeably, they have some distinct differences, so let’s look at each to clearly understand what they mean.

1.   Repairs aim to strengthen the structure to its pre-disaster strength. Comparatively, repairs take the least amount of time and resources.

2.      Rehabilitation is the term used when the structure’s strength is increased up to its original design strength.

3.      Retrofitting refers to enhancing the structure’s strength to the present code level. Codes adapt over time with new materials and new safety measures. So older structures require upgrades to meet the newest standards and to resist higher level of forces. Retrofitting takes the most amount of planning and resources compared to previous two.

The figure above shows the qualitative relationship between a structure’s strength and elapsed time after its construction. A few years after construction, the structure slowly loses its strength due to multiple environmental factors. When a disaster strikes it, we observe an immediate loss of strength. In figure we see a graphic differentiation for repair, rehabilitation and retrofitting in terms of structural strength, as well as their required time.

When we look at the impacts of disaster, multiple studies have shown that initial investment in preventive measures can save five to seven times the financial burden of disaster recovery. Though, this doesn’t begin to measure the lives and livelihoods that can be preserved by strengthening our structures ahead of disaster.

Now, consider what happens to the structure above when rehabilitated or retrofitted before the disaster. Clearly, the strengthened structure performs much better and saves lives and money during and after the disaster event.

So, the lesson here is: we must monitor our homes, schools, shopping centers, factories, bridges etc. on a regular basis to ensure our structures can withstand a catastrophic event. Any sign of significant deterioration should prompt us to take immediate action – repair, rehabilitation or retrofit. Of course, we have to weigh all of the factors when developing the plan for strengthening measures, including available resources, shut down time and other priorities. But we must design solutions for these problems before it’s too late.

We, at Walter P Moore , have helped multiple clients to reduce losses and shut-down time with preventive action (Example-1Example-2). Its time to proactively prepare our society for disaster resiliency.

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