A structural collapse compresses every competing interest into the same chaotic window. Rescue operations take priority. Law enforcement may declare the site a crime scene. Federal agencies may assert jurisdiction within hours. The investigation may not yet have begun, and in some cases, evidence may already be altered, displaced, or lost.
By the time forensic engineers retained by insurance carriers, property owners, contractors, and design professionals can access the site, critical evidence may be disturbed, removed, or demolished before forensic access is granted.
This article examines the primary causes of catastrophic structural failure, how forensic investigations establish causation under those conditions, and what the evidentiary record typically reveals when engineering, materials, and human factors intersect.
Key takeaways: Understanding catastrophic failure in construction
Claims managers and litigation attorneys handling complex structural failures benefit from understanding the formal mechanisms, investigation methodology, and governing standards before they need them.
What matters most
- “Catastrophic failure” describes severity; the operative legal and technical mechanisms are progressive collapse and disproportionate collapse, a distinction that drives foreseeability analysis and design-obligation questions.
- NIST and NTSB investigations may take several years to complete. Claims and litigation timelines often proceed more quickly, and federal statutes limit how agency reports may be used in civil proceedings.
- Major federal case studies frequently document compound causation involving multiple contributing factors and parties, rather than a single isolated cause.
How investigations typically proceed
- Private forensic teams may conduct investigations concurrent with federal inquiries, often following ASTM guidance for evidence handling and methodology to develop documentation that may be used in claims and dispute resolution.
- Root cause analysis is typically structured as a hypothesis-driven process: develop potential failure mechanisms, gather evidence, and evaluate each hypothesis against the available data.
- Multidisciplinary coordination across structural, materials, and geotechnical disciplines is typically required, and gaps between those disciplines are a common source of contested expert opinions in litigation
Contact us for forensic investigation support.
What is catastrophic failure?
In practice, “catastrophic failure” does real work in insurance coverage analysis and liability framing. It is not consistently defined as a formal technical term in principal building codes and structural engineering standards, including the IBC and ASCE 7.
Progressive and disproportionate collapse: The operative distinction
American Society of Civil Engineers (ASCE) standard ASCE/SEI 76-23, published in April 2023, provides widely referenced current definitions. Disproportionate collapse is characterized by a pronounced disparity between the original cause and the ensuing collapse of a major part or the whole of a structure. Progressive collapse describes the mechanism: it commences with the failure of one or a few structural components and spreads through the successive failures of others, often producing a disproportionate outcome.
That distinction may influence how causation and design obligations are analyzed after a collapse.. The loss of a single column or connection failure may raise different duty-of-care questions than a progressive collapse triggered by that same element in a non-redundant structural system. Whether the structure was designed with adequate redundancy under the standards in effect at the time of construction often emerges as a key investigation question.
The standards gap for pre-2023 structures
ASCE/SEI 76-23 is the first consensus performance standard in the United States specifically for disproportionate collapse mitigation. Before April 2023, practitioners evaluating a structure’s disproportionate collapse resistance did not have a single unified consensus benchmark: they worked from Department of Defense guidance, U.S. General Services Administration progressive collapse guidance, or general ASCE 7 structural integrity provisions, none of which functioned as a single unified performance standard..
For structures designed and built before ASCE/SEI 76-23’s adoption, the forensic question becomes which guidance applied at the time of design, and whether the structure met it. That is not a trivial determination. The code of record at the time of construction is generally one of several factors considered when evaluating standard of care, and identifying the applicable edition is typically one of the first tasks in a major collapse investigation.
What types of catastrophic failure occur?
Catastrophic failures in construction are often described by failure mechanism and by the degree of warning available before collapse; both typically inform causation analysis. Federal investigations commonly document the following:
- Progressive or disproportionate collapse: initiating event damage that spreads element by element to produce a system-wide collapse disproportionate to the original cause (NIST IR 7396; ASCE/SEI 76-23).
- Connection failure: failure at structural joints including bolt fracture, bolt hole tear-out, and weld failure; these may produce physical evidence that survives the collapse and may support material testing.
- Brittle fracture: sudden crack extension with rapid propagation and limited plastic deformation; may produce little visible warning, which may be relevant to reasonable-care analysis.
- Buckling and overload failure: structural member instability under excessive or unanticipated load, including gusset plate deficiency and cumulative added load over the structure’s life, as examined in NTSB HAR-08/03.
- Foundation and geotechnical failure: subsurface failure via sliding, toppling, or erosion-related undermining, as addressed in U.S. Army Corps of Engineers (USACE) engineering guidance.
The degree of warning available before collapse is generally relevant in construction claims and reasonable-care analysis. Failure modes that provide visible pre-collapse distress (widening cracks, lateral displacement, deflection acceleration) may present different questions than sudden brittle failures that provide none.
What are common causes of catastrophic failure?
Federal investigations frequently document compound causation: an initiating event compounded by pre-existing deficiencies that removed redundancy. For claims professionals, that pattern may signal multiple potentially liable parties across subrogation analysis, reserve-setting, and allocation discussions.
Design error with quality control breakdown. A calculation deficiency that, in some cases, may have been caught by a functioning review process often surfaces alongside evidence that the review process failed. The I-35W Bridge collapse (2007) involved inadequate gusset plate load capacity attributed to a design error, compounded by failure of the designer’s quality control procedures, according to NTSB HAR-08/03.
Deferred maintenance accelerating latent deficiency. The collapse event and the originating deficiency are often years apart: inspection reports document deterioration, maintenance recommendations go unaddressed, and the structure continues to carry load until a threshold is crossed. According to NTSB HIR-24-02, the 2022 Fern Hollow Bridge collapse involved a fracture-critical transverse tie plate with extensive corrosion attributed to clogged drains, with repeated maintenance recommendations going unaddressed in prior inspection reports.
Vulnerability not assessed or mitigated. When a known risk category applies and no assessment has been documented, the absence may be evaluated in relation to project requirements, risk management practices, and applicable standards. Preliminary NTSB investigation records indicate the Francis Scott Key Bridge substantially exceeded American Association of State Highway and Transportation Officials (AASHTO) risk thresholds for vessel-strike vulnerability, with no vulnerability assessment on record (NTSB DCA24MM031).
Because these patterns appear consistently across major collapses, investigations are typically structured from the outset to evaluate each potential contributing party and mechanism rather than narrowing to a single cause.
How are catastrophic failures investigated?
The ASCE Guidelines for Failure Investigation, Second Edition defines five phases: planning, data collection, testing protocol development, analysis, and presentation of opinions. Each phase builds on the integrity of the one before it. What can be proven at the end depends on decisions made at the beginning.
Planning begins before site access is granted. By law, the NTSBis authorized to investigate bridge collapses involving loss of life and may control the scene and subpoena evidence. Under the National Construction Safety Team (NCST) Act, NIST may exercise discretionary authority over building collapses involving substantial loss of life. When law enforcement declares a crime scene, criminal authority takes precedence. Private forensic teams coordinate access within those constraints, not around them.
Data collection is constrained by whoever controls the scene first. The Champlain Towers South investigation illustrates this directly: NIST and Miami-Dade County Sheriff personnel triaged debris, transported evidence to a secured warehouse, and catalogued hundreds of structural specimens before testing began.
Testing protocol development follows ASTM International (ASTM) standards for evidence handling and methodology, including E1188-23, E860-22, and E1459-24. These standards provide guidance on how physical evidence is collected, preserved, and prepared for analysis.
Analysis examines the full chain of contributing conditions, not just the triggering event. The ASCE Guidelines establish this explicitly. In construction collapse litigation, that distinction determines how liability is allocated across parties.
Presentation produces the defensible opinions that support legal proceedings. The Champlain Towers civil litigation settled in 2022, years before NIST’s final report. Private forensic investigation, running parallel to the federal track, generated the documentation those proceedings required.
When do structural failure investigations require multidisciplinary coordination?
Examining that full chain rarely involves a single discipline. Structural engineering analysis may identify a gusset plate deficiency; materials testing may determine whether the steel met specified properties; geotechnical analysis may evaluate whether foundation movement contributed. Each discipline may produce separate expert opinions that typically need to be reconciled before findings are presented in litigation.
Whether those opinions ultimately converge depends on the investigation. Multiple independent teams investigated the I-35W Bridge collapse and largely reached consistent conclusions on the primary cause; that convergence is not always the outcome. In complex collapses, different teams working from the same physical evidence sometimes reach different causation theories, and when they do, those differences are often addressed through expert deposition and trial testimony.
Coordinated expert services managed under a single framework, rather than separately commissioned opinions assembled after the fact, may help reduce the risk of internal inconsistencies across technical findings.
What standards govern catastrophic failure investigations?
The standards used in conducting an investigation may influence how its findings are evaluated in legal proceedings.
ASTM E2713-25 (Standard Guide to Forensic Engineering, 2025 edition) provides the foundational professional practice reference for forensic engineering in the private sector, covering practitioner qualifications, roles, and the elements of forensic investigation. Use of recognized methodology standards may be considered when evaluating the reliability of expert opinions in legal proceedings..
Additional ASTM standards govern specific process steps: E3176-24 addresses forensic engineering expert report preparation; E620-18 establishes elements of expert opinion reports. Because standards are periodically updated, identifying the current edition and whether it was in effect at the time of the investigation is standard practice.
Those private-sector standards exist in part because federal investigation reports cannot serve the same function in civil proceedings. NTSB investigation reports are generally barred by federal statute from admission as evidence in civil damages actions. NIST National Construction Safety Team reports carry the same bar under the NCST Act. Private forensic investigation following equivalent methodology is often an important component in developing technical findings that may be used in claims and dispute resolution.
What forensic practitioners need to know about claims strategy
Independent forensic investigation is generally most effective when begun before federal agencies conclude theirs. Federal investigations take years, their reports are inadmissible in civil proceedings, and claims reserve decisions, coverage disputes, and discovery schedules cannot wait. Early engagement may support more complete documentation, while delayed engagement may limit the availability of certain evidence.
The case for early engagement is reinforced by what the field has documented about the structures that have not yet collapsed. The Collaborative Reporting for Safer Structures (CROSS-US), an ASCE-endorsed confidential reporting system modeled on the aviation safety framework developed by NASA, publishes near-miss accounts and structural safety reports from practicing engineers. The program reflects a broader recognition that compound causation, deferred maintenance, and pre-existing redundancy deficiencies are not unique to high-profile collapses; they appear across the broader built environment.
Rimkus forensic engineers can discuss the specific requirements of your investigation. Contact us to get started.
Frequently asked questions
Why can’t claims professionals and litigants use NIST or NTSB reports as evidence?
NTSB and NIST National Construction Safety Team reports are subject to federal statutory limitations regarding their use as evidence in civil damages actions; neither agency issues findings of fault or negligence. Independent forensic investigation governed by ASTM standards is commonly used to develop causation documentation for claims and dispute resolution.
What are the key indicators of impending catastrophic failure?
Commonly documented pre-collapse indicators include accelerating deflection rates, audible cracking, widening cracks, spalling concrete, exposed rebar, out-of-plane movement, lateral displacement, and rust staining associated with subsurface section loss. Prior inspection reports documenting such conditions may be significant to post-collapse liability analysis and are often among the first documents forensic engineers request.
What role does non-destructive testing play in catastrophic failure analysis?
Non-destructive testing allows investigators to characterize material condition and map structural anomalies without consuming evidence, which can be important when preserving physical evidence for further evaluation. Methods including ultrasonic testing, radiographic examination, and thermographic imaging may be performed alongside visual documentation and prior to or in coordination with destructive laboratory testing to identify failure initiation sites and guide sampling decisions.
Authored by: Rimkus Forensics Marketing Team
Published April 10, 2026.
This article is intended to provide general information and insights into prevailing industry practices. It is not intended to constitute, and should not be relied upon as, legal, technical, or professional advice. The content does not replace consultation with a qualified expert or professional regarding the specific facts and circumstances of any particular matter.