Miami Condo Collapse - A Perspective

First things first, my condolences to all who have lost their loved ones in the tragic collapse of Miami Condo in Florida. It is devastating to watch these incidents happening. Much have been already said (or speculated) about the #buildingcollapse in #miami. I am certain it will take quite sometime for forensic experts to accurately identify the contributing factors.

Over the past few years, I have inspected and assessed a number of residential, commercial, and industrial facilities. This relatively short experience has introduced me to complexities, and challenges in evaluating the condition of constructed facilities. In this short note, I am going to highlight some of the challenges I have been facing in this domain.

A structural systems is a complex systems

Structural systems are a combination of various components:

• Foundations
• Columns and Load Bearing Walls
• Girders and Beams
• Lateral Load Resisting Systems (Shear Walls, Braces, Dampers)
• Slabs (Floors, Roofs, Balconies)

While each component have complexities in design and detailing requirement (based on demand), the coupling of these elements and load distribution adds to the complexities.

Element Level Inspection is Good But Not Sufficient

Most inspections are planned at "component level". While this is quite useful in evaluating the maintenance needs, it often fails to provide an insight into the structural response of the entire system. A crack in a beam is different from a crack in a column or slab.

Corrosion of steel bars at the base of a parking garage column is not only a durability concern, but a structural problem as well. Inspectors might provide useful insight on the quality and structural integrity of elements, however, it is structural engineers job to solve the jigsaw puzzle of all contributing factors, and re-assess the structural performance.

Understanding the Deterioration of Construction Materials

Deterioration of construction materials over time is inevitable. Steel bars in concrete elements that are exposed to chloride or saline environment corrode. Concrete materials containing Active Silica can result in ASR, and experience significant cracking when exposed to moisture.

An experienced inspector can identify these defects, but assessing their impact on global performance of the structural systems requires modeling (even basic), and analysis.

Addressing the "Not Enough Money for Inspection" Problem

In talking to asset owners (capital assets, residential, and commercial), you often hear "Not Enough Money" for this. This is sad, but it is true. Asset owners feel money invested in the inspection is a lost capital. While major asset owners (oil and energy, nuclear, transportation) have implemented a much better inspection protocols, the residential and commercial sector lacks universal understanding of the inspection process.

Inspection can be costly; A good inspection and assessment is certainly costly, but it can save lives. And as we all learn from the code of ethics, public safety should be our paramount. Nothing should be more expensive than the lives of innocent residents.

4 Key to Successful Inspection and Assessment

Over the past few years, I have received some weird requests from my clients (not only building owners, but also consultants and contractors):

• Can you just sign this is Ok?
• Can you quickly look at this photo and let me know if it is safe?
• Can you come and take couple of readings and let me know if the structure is safe?

And these are from the developed parts of the world. I can imagine things can be far worst in the less privileged parts of the globe.

A successful inspection requires 4 key components:

1. Implementing a Scientific Approach (Use relevant codes, guidelines, and standards, or literature)
2. Use Scientific Methods (Rely on previously approved methods for each specific problem).
3. Collect Observations (Each and Every Crack, leak, spall can ring a bell). Don't ignore.
4. Collect Data (Use Technology to collect insight about mechanical and durability performance of structural components.

Multi-Technology Approach to Building Assessment

When I was a bachelor student, my Steel Design Professor had an interesting phrase when describing bolt connections "1 bolt means 0 bolt, 2 bolt means 0 bolt", literally specifying the minimum number of bolts required for a stable connection.

Recent advancements in inspection technologies and materials testing enable engineers collect far better insight about the structural integrity and quality of materials. #nondestructivetesting devices are now capable of identifying subsurface anomalies, help estimate the location and extent of defects, and get a better picture of the condition of elements.

More advanced structural systems such as modern bridges (New Champlain Bridge) and high rise towers (Burj Khalifa) use advanced monitoring and warning systems that trigger in the event of major structural changes (excessive strains, deformations, tilt, etc). Learn more about different SHM sensors here

Combine Inspection, Numerical Modeling and Structural Evaluation

Results from inspection should be incorporated into maintenance programs. But there is no magic trick here. Results from the laboratory tests, and nondestructive testing should be translated into something more meaningful.

As a structural engineer, we need to collect these information, reproduce structural models that are accurate representative of the current condition of the elements, and assess the structural performance (demand vs capacity). Engineers should work closely with asset owners to identify performance objectives, and design remedy/rehabilitation plans accordingly.