Uncovering the Root Cause: The Vital Role of Forensic Engineering in Preventing Structural Failures
By Cecilia Muchemi, Samuel Mbugua
TL;DR
Forensic engineering is the systematic investigation of a failure or an incident with the aim of establishing the root cause or causes of the event, and recommending actions to prevent recurrence. This field promotes responsibility, accountability and emphasizes the value of adhering to the engineer’s code of ethics. Despite its growing significance and application in engineering disputes globally, investigative engineering has not yet found its rightful place in the engineering curriculum. There is a need for every civil engineer to have a comprehensive understanding of structural failure. Buildings fail because of design errors, material defects, poor management, professional misconduct, execution defects and more. Forensic engineering helps anticipate failures and provides insights from those that have already occurred. This field has not been fully leveraged in Kenya’s engineering industry. Embracing Forensic engineering will encourage contractors to be more keen on following engineer specifications and will definitely discourage unethical conduct.
Introduction
Forensic Engineering involves the analysis of physical evidence, documentation, and eyewitness accounts to determine factors contributing to the failure and how to prevent similar failures from occurring in the future.
According to the American Society of Civil Engineers (ASCE), “Engineering forensics is the systematic investigation of a failure or incident to establish the root cause or causes of the event, and to recommend actions to prevent recurrence” (ASCE, 2011).
Like in many other parts of the world, Forensic engineering is not well known in Kenya despite being an important field in Civil engineering. Through failure investigation, corrections as well as additions have been made to design codes therefore accommodating new lessons learnt. This counts as significant development in the field and has helped anticipate failures that would have otherwise been missed. In addition to that, ASCE notes that engineering forensics is not just limited to investigating failures, but can also be used to assess the safety and reliability of structures, materials, and systems before they are put into service.
Although Forensic Engineering might seem as if it is a field solely dedicated to assigning blame for catastrophic structural failures, it’s main objectives are to promote responsibility and accountability and to emphasize the value of adhering to the engineer’s code of ethics.
History
The word forensic originates from “forensis” in Latin meaning “in open court”. Forensic engineering therefore literally is engineering presented in an open forum, mostly a judicial one. There exists little material on the history of forensic civil engineering but the earliest case could be one dated 1389 where master builder Simone da Orsenigo began construction of the Milan Cathedral in Italy. He later was dismissed in the same year and Jean Mignot replaced him. The latter found fault with Simone’s work and a pseudo-judiciary made up of master builders in Europe convened to decide whether Jean Mignot had reason to denounce the work. The builders ruled in Simone’s favor and the building is still standing.
Why it is easy to fail: Understanding the Challenges
According to the American Society of Civil Engineers (ASCE), construction projects face challenges due to the unpredictable exposure to natural and man-made hazards. In addition, the design team is composed of various stakeholders e.g., owners, design professionals, and construction professionals, who come together temporarily to work on the project. Due to the interdependence of these multiple factors, the design must prioritize sound engineering judgment over certainty to ensure the facility’s safety.
“Design and construction of civil engineering projects presents unique challenges. The design and construction “team” consists of owners, design professionals, and construction professionals in a temporary association for a specific project. The unpredictability of the exposure to natural and man-made hazards that the facility will experience during its life necessitates that the design be based on sound engineering judgment rather than certainty.” (ASCE, 2012, Preface. Failure case studies in civil engineering: Foundations and the geoenvironment (2nd ed.))
Despite these challenges, civil engineers are tasked with creating structures that are not only functional but also durable and resilient. They must take into account all the factors that are involved e.g., environmental conditions, building codes, and materials selection to ensure the safety of the public and minimize the risk of failure. Despite the complexity of their work, civil engineers play a critical role in shaping the built environment and improving quality of life.
Therefore, there is a need for every civil engineer to have comprehensive failure understanding and literacy.
According to Norbert J. Delatte, “It [failure literacy] is a knowledge of potential failure modes and limit states informed by a historical perspective on reasons for past failures and patterns of failure.”(Beyond failure- Forensic Case Studies for Civil Engineers, 2009)
Building Collapses in Kenya and the untapped potential of Forensic Engineering
Recently there have been numerous cases of buildings collapsing during and after construction. The rise in structural failure in Kenya has been alarming and unsettling as it has cost people’s lives and property. A recent failure in Kiambu suggests failure due to substandard materials, lack of proper supervision and poor workmanship. These are all based on visual observations. Forensic engineering requires deeper analysis involving laboratory and field tests. As evidenced by how challenging it is to obtain reports on structural failures at the site in Kiambu and many others, it is accurate to say that the field of forensic engineering has not been fully utilized in Kenya’s engineering industry.
Embracing Forensic engineering will encourage contractors to be more keen to follow the engineer’s specifications as they will be held accountable following investigations in case of failure. It will also discourage unethical conduct by the contractors for instance, the use of substandard materials, corruption evading correct procedures in construction, cutting back on the quantity of materials to save cost and more. In addition, failure literacy will help engineers develop an “intuition” for structural behavior which in turn will help with failure prediction. It will also help engineers appreciate the need for ethical conduct when making construction decisions. Finally, embracing Forensic Engineering will equip engineers with the necessary tools to drive developments in the field as new information is acquired from observations on structural performance.
Surviving the Stress: The Two Vital Limit States for Structural Design
As mentioned earlier buildings fail because of a myriad of reasons. These could be design errors, material defects, managerial problems, professional misconduct, execution defects and more.
On structural design, Eurocode defines two limit states as far as structural design is concerned. A limit state is the disposition of a structure beyond which it does not fulfill the relevant design criteria. The first limit state is the Ultimate limit state and it is concerned with the safety of people and/or the safety of the structure. The second limit state is the serviceability limit state that is concerned with the functioning of the structure or structural members under normal use, the comfort of people and the appearance of the construction works. Adequately designing for limit states is perhaps the most important aspect of structural failure prevention. These should be verified in every design to minimize design errors.
The engineer should be in the know about different aspects of a project and should not over rely on software
Engineers are required to have intricate knowledge concerning material strengths as well as the site properties such as the soil bearing capacity in order to design adequately.. Soil bearing capacity is the capacity of soil to support the loads that are applied to the ground above and is used in the design of column bases. This capacity is a key factor of structural integrity and using nominal figures as it was done in school is dangerous as these figures vary a lot in the field.. Also, engineers are required to understand design well before using computer design software. Overdependence on software can be detrimental in some cases. A space truss roof in Hartford Civic Center in the US collapsed under snowfall in 1978 due to design errors and underestimation of loads. The engineers had trusted software to check the integrity of their structure and the results were faulty.
According to Shepherd and Frost, “Computer programs are only as good as their programmers and may tend to offer engineers a false sense of security.”(Failures in Civil Engineering: Structural, Foundation, and Geoenvironmental Case Studies, ASCE, 1995)
Engineers and contractors ought to know the quality of the materials they use. Quality materials that have been tested minimize the possibility of structural deformity and failure. Engineers at FlamiCore construction, Nyeri, Kenya tested commercially available reinforcement steel bars in Nairobi and observed that steel reinforcement specified to be grade 500, meaning the yield tensile strength is 500N/mm2, is not always exactly grade 500, technically speaking. In most situations its yield tensile strength is below the specified 500N/mm2.It is important to accommodate this knowledge in the structural design. Moreover, concrete compressive strength is an important parameter in concrete construction in general. Given that cement in the market is not always up to standard, mix design to attain the required strength is needed. The normal practice for concrete mixing is the use of nominal ratios; 1:2:4 for class 20 concrete and 1:1.5:3 for class 25. However, concrete mix design is useful in ensuring that the 28-day strength of concrete is as specified in the structural specifications.
Engineers at FlamiCore construction, Nyeri, Kenya tested commercially available reinforcement steel bars in Nairobi and observed that steel reinforcement specified to be grade 500, meaning the yield tensile strength is 500N/mm2, is not always exactly grade 500, technically speaking. In most situations its yield tensile strength is below the specified value.
The principle of ownership in traditional management also applies to construction projects
Every project requires one person who is responsible for it in its entirety. A construction project has a couple of professionals involved: architect, structural engineer, construction manager and quantity surveyor. These professionals work with the contractor to see the project to its completion. When none of these are wholly responsible, managerial breakdown occurs and certain problems during construction slip into the cracks. The Hartford Civic Center case had been divided into five subcontracts which made it possible for errors to go unnoticed. in the same line of thought, when skilled and unskilled laborers are shuffled, the fragmentation and discontinuity creates a breeding ground for mistakes to go unnoticed and/or uncorrected.
Professional conduct and flawless execution is critical in construction projects
Professional misconduct is a thorn in Kenya’s construction industry because corruption has been normalized. Contractors are paying bribes to be able to evade certain procedures like approvals which are there to regulate construction and promote safety of structures. Moreover, cost saving has been over-prioritized by contractors such that some are willing to sacrifice the safety of the structure by unauthorized conversion or alteration or addition to the approved structure.
Execution problems occur when there is poor workmanship and/or blatant disregard of standard construction specifications. An example is improper shoring which is a source of concern especially for slabs. It is important to design the slab formwork to ensure it holds the concrete as it cures.
Moreover, it is important to ensure the concrete has gained enough strength to support itself before removing the formwork. Premature removal of shoring has caused disastrous damage in the past. Ensuring the necessary concrete strength can be achieved through field testing, as field conditions frequently differ from those in the laboratory. Low temperature is known to delay concrete curing and so the testing of cubes that have been cured in the same environment as the building concrete is important in determining whether the concrete has reached enough strength for formwork removal.
There are many other reasons for failure and a good book to read about them is Norbert J. Delatte’s Beyond failure- Forensic Case Studies for Civil Engineers, ASCE, 2009. Forensic investigations keep unearthing more failure types as structural behavior continues to be studied.
Future
In addition to promoting accountability, Forensic engineering plays a crucial role in advancing the construction industry by identifying mistakes that would have otherwise been repeated. Past mistakes are an important source of information to the engineering field, informing decisions in both the technical and management aspects of a project.
This sub-discipline is growing and will keep doing so and in the near future, failure prediction and detection will be a more important aspect in construction decisions than it is today. The engineering profession will benefit a great deal from failure investigation and information obtained from these studies.
Advancing the Construction Industry Through Forensic Engineering: Call to action
Given its potential to bring about transformative changes, more professionals should explore failure analysis. Being knowledgeable about structural failure can aid in comprehending complex technical concepts and developing an instinctual understanding of how structures behave. It also allows for an understanding of how the engineering science evolves over time as performance is observed and lessons are learned from failures. Additionally, failure literacy fosters an appreciation for the importance of ethics in decision making and a recognition of the impact of engineering decisions on society.
Authors
Cecilia Muchemi, cessmuchemi@gmail.com
Samuel Mbugua, skm228@cornell.edu
