“She was about two steps ahead of me. As soon as it shook, I grabbed her by the neck, by the back of the shirt … and I yanked her back. And as I was yanking her back, it came down, grazed her head, grazed her leg, and that’s it.”1 

“When he placed his coffee on the table, Mr. Marceau heard a big bang and was hit by debris on the head, over the eyes, and on the nose. He lost consciousness immediately.”2 

On June 23, 2012, part of the Algo Centre Mall, located in Elliot Lake, Ontario, suddenly collapsed. The mall was a concrete-and-steel structure suffering from decades of water infiltration, corrosion, and delamination. A large reinforced-concrete slab weighing several tonnes detached and plunged into the food court below (Figure 1). 

“The Priestly demolition was complete at approximately 6 a.m. The immediate next step was to use a dog to conduct a search for live victims in the collapse zone. The OPP’s Cst. Dan Bailey was asked to perform this search and he decided to use Dare, a dog cross-trained for both cadaver and live searches. Cst. Bailey started his search of the collapse zone with Dare at or around 6 a.m. As his notes indicate, Dare gave indications only of deceased victims.”3 

“June 23, 2012: Rooftop garage caves in, killing Lucie Aylwin, 37, Doloris Perizzolo, 74, and injuring several other people. 

June 24, 2012: Heavy Urban Search and Rescue Team arrives from Toronto. 

June 27, 2012: Bodies of the two victims are recovered.” 4 

Figure 1. Photograph of the Algo Centre Mall in Elliot Lake, taken from CBC news reporting5 

In October 2014, the Ministry of the Attorney General of Ontario published a public inquiry report regarding the collapse. Reading the report is heartbreaking. The tragic structural failure of the Algo Centre Mall killed two women and injured over twenty people who were simply going about their daily lives. The victims may have been visiting the mall to make a purchase, attend work, or have coffee with a friend or relative. 

Reinforced concrete or steel buildings and parking structures rarely come with an instruction manual. Some are decades old. Some have been modified without drawings. Others have weathered corrosion, leaks, heavy vehicle loads, or even decades of winter de-icing chemicals and salts. Old buildings may have also changed hands multiple times, and regular condition assessments and maintenance programs are at times abandoned and neglected. In some extreme cases or when a collapse occurred, short-term financial considerations were prioritized over sustained investments to ensure long-term serviceability with adequate safety levels. 

It is important to note that diligent owners do follow property management and maintenance plans and maintain updated documentation to ensure safety and compliance over time (e.g., property records, maintenance and monitoring programs, operational procedures). 

Beyond perception, is a structure still strong enough? 

To most people, concrete and steel appear strong regardless of their age and condition. In some cities, people have become numb to seeing signs of deterioration in buildings and non-building structures exposed to the elements or in industrial or commercial settings where concrete and steel are prone to deterioration (e.g., parking structures, overpasses, tanks, silos, towers, municipal infrastructure).  

As a specialized structural forensic engineer, I regularly investigate structural failures and am therefore not only familiar with the aging infrastructure in North America but also follow recent events, research, and investigations that make this topic increasingly relevant. For this reason, I decided to write this article to remind the general public of the importance of regularly assessing, monitoring, and maintaining structures and infrastructure, particularly those prone to deterioration, based on a program reviewed and approved by industry professionals. 

The Importance of Investigating a Structural Failure 

Forensic investigations of structural failures provide valuable insights to society, helping regulators ensure that such tragedies never happen again. Investigations aim to uncover the truth and understand what occurred before and during a failure. Sometimes, a failure is an unfortunate complete collapse, while at other times it is localized or identified as a deficiency to be addressed to ensure safety. 

The investigative work combines engineering judgment, non-destructive evaluations, intrusive testing, structural and code analyses, and a deep understanding of the behaviour and performance of the structural system, construction materials, and loads. The process is more complex than many people expect. 

The Investigative Process 

A forensic structural engineer begins a failure investigation the same way a detective begins a case: by establishing a detailed history. Relevant records typically include design and construction records, permit documents, past repairs or claims, contractual records, historical photographs, inspection logs, and correspondence, among other pertinent documents. However, in many cases, this paperwork is either incomplete or nonexistent. 

In addition, a firsthand assessment or inspection of the physical evidence, such as the collapsed structure, is essential to gather relevant information. There is no substitute for walking the structure. On that first visit, beyond observing cracks or rust stains, it is essential to reconstruct and understand the original design intent, looking for possible subtle signs of distress, deterioration, damage or modifications (e.g., visible displacements or deformation, spalling or delamination of concrete, corrosion of steel, signs of water intrusion or previous fire damage, structural alterations, distinction between widespread or localized symptoms, etc.). 

Before a complete collapse, a visual survey may reveal clues about whether the structure is aging gracefully or showing signs of distress, such as abnormal deformation, cracking, or deterioration. Such observations should trigger the necessary actions to ensure safety and prevent failures. 

Since information is at times incomplete, a forensic investigation must be strategic, targeted, and risk driven. For instance, it is important to identify the structural members, connections, and other components that are most critical to safety, as well as the areas or factors of highest uncertainty and immediately act to ensure safety. Once all safety measures are implemented, the expert must consider the tests that will provide the most reliable information and the required locations. 

Under the Surface Evaluation 

Structures hold their secrets beneath the surface, such as materials that clad the structure (e.g., interior and exterior finishes) or beneath an outer thickness of concrete cover, in the case of reinforced concrete. A mix of techniques and technologies and hands-on methods to uncover the truth are implemented during an investigation to gather the necessary data related to the structure. 

For instance, regarding the geometry and configuration of steel reinforcement, we locate the rebar using tools like concrete scanners, rebar locators, ground-penetrating radars, cover meters, or small tests openings to visually confirm bar size, spacing, and anchorage. In some cases, we may find that the steel reinforcement (bars) may not match the drawings (e.g., missing reinforcement, unconventional or inconsistent details, etc.). The as-built conditions matter when determining the actual strength of the existing structure. 

As another example, the investigative work may find inconsistencies in the as-built material properties, which may not match what the original drawings specified. The investigation may require laboratory testing to verify the relevant material properties, such as the material strength under specific loads and other properties. For instance, depending on the case and when required, we may extract concrete cores or steel coupons for different laboratory tests. These data points are essential, especially when deterioration or poor construction quality has altered the original design or intended properties. 

Assess, Maintain, Monitor 

In general, structures deteriorate over time, particularly those exposed to cyclic loading, aggressive chemical environments, freeze–thaw cycles, sustained moisture infiltration, harsh environmental conditions, temperature fluctuations, and UV radiation, among other factors. Property managers and owners must follow maintenance and monitoring programs as required to assess the level of deterioration of structures based on the aforementioned factors and the building’s age, as deterioration affects a structure’s capacity to resist loads and could lead to failure. Understanding the level of safety and how a structure will perform in the years ahead is incredibly valuable to building owners, tenants and occupants, municipalities, and other stakeholders. 

Once owners, property managers, and their engineers understand how a structure was actually built and how it has aged, the structural performance can be simulated and analyzed to develop or update consequential assessment, maintenance, and monitoring programs. For instance, models can be created and calculations performed to determine how a structure would perform under certain loading conditions. Assessing an existing structure requires, not simply reporting observations or plugging numbers into formulas, but also uncovering the true story of a building, how it was designed and constructed, how it has aged, how it actually behaves today, how it should be used or reinforced, and what can be anticipated in the future. 

Improving and following regular assessment, maintenance, and monitoring programs to ensure safety would not only assist in decision-making but also honour the victims of the Algo Centre Mall collapse and help to prevent future tragedies and save lives. 

  1. Report of the Elliot Lake Commission of Inquiry, Part Two: The Emergency Response and Inquiry Process, Jason Morrissey testimony (p. 49).
  2. Report of the Elliot Lake Commission of Inquiry, Part Two: The Emergency Response and Inquiry Process, Jean-Marie Marceau testimony (p. 50).
  3. Report of the Elliot Lake Commission of Inquiry, Part Two: The Emergency Response and Inquiry Process, A sniffer dog search of the collapse zone at 6 a.m. indicates two deceased (p. 288).
  4. Elliot Lake Mall chronology: from birth to death — and beyond | CBC News.
  5. Elliot Lake roof collapse class action lawsuit OK’d by judge | CBC News.