Special Structures (Bridges, Tanks)
For more than 40 years, Exponent has been called to investigate structural failures ranging from major catastrophes to simple performance failures. In that time, we have developed specialized expertise in various structural systems that have unique functions and behaviors. In these specialized areas, Exponent’s structural engineers can draw on the firm’s other 90+ science and engineering disciplines, applying state-of-the-art analytical and testing methods. Structures for which we have developed specialized expertise include bridges, pre-engineered metal buildings, and bulk storage structures.
More than 40% of the nation’s bridges are over 40 years old, while the average truck traffic loads in many states have almost doubled over the same period. Periodic high-profile bridge failures revitalize replacement, retrofit, inspection, and maintenance of our aging infrastructure.
Exponent bridge engineers draw from our other in-house disciplines, including structural engineering, geotechnical engineering, reinforced/pre-stressed concrete, concrete degradation, metal corrosion, fatigue and fracture, construction claims, risk and reliability, instrumentation, and accident reconstruction to address multi-disciplinary problems presented over the entire lifespan of bridges. Our extensive experience in investigating failures of bridges and other structures gives us a unique perspective to assist the design and construction industry in providing preventive measures in early stages of design and construction, as well as identifying the root cause(s) of a failure or defect. Exponent has worked with both contractors and state Departments of Transportation to evaluate the construction claims arising out of schedule-related problems, and also to separate the effects of design errors or omissions from those due to poor construction.
- Failure investigation
- Peer review of design
- Construction management and claims analysis
- Diagnostic testing/long-term monitoring
- Accident reconstruction
- Seismic evaluation
- Construction quality and material defect investigation
- Load rating
Storage Structures for Bulk Solids and Liquids
Storage facilities for bulk solids involve diverse loading and withdrawal systems that produce complex flow patterns. Failure of storage structures such as silos and bunkers, as well as large liquid tanks, can have catastrophic consequences for both injury and economic loss. Failure is often sudden and may occur after years of trouble-free operation.
Exponent’s engineers have designed bulk storage facilities and have investigated problems with silos and bunkers that range from water intrusion to total collapse. Our scientific and engineering team is uniquely qualified to investigate and pinpoint the root cause of the failure and provide a thorough assessment of the damage and associated repair, retrofit, or improvement of operational performance. Our state-of-the-art engineering often serves as the basis for determining insurance claims or settling legal disputes.
Bulk Storage Services
- Structural design and detailing
- Flow properties of stored bulk solids
- Seismic, wind, and dust explosion hazard analysis
- Construction defects, cracking, and structural degradation
- Operation of mechanical shifting and control devices
- Maintenance procedures
- Failure risk analysis
- Accident reconstruction
- Retrofit or repair designs
Pre-Engineered Building and Metal Roof Failures
Pre-engineered metal buildings (also known as metal building systems) are designed and fabricated by their manufacturers. These structures represent, by some estimates, about two-thirds of all low-rise nonresidential buildings in the United States. Despite their great numbers, metal buildings often present an enigma to the specifier and user alike, and their proprietary design makes analysis by outside engineers difficult.
Like all other structures, pre-engineered buildings can, and do, fail. Their failures can be caused by a variety of factors, the most common of which include:
- Overload by snow or wind forces
- Improper design practices by the specifiers or manufacturers
- Defective construction
- Deterioration caused by corrosion, fire, and other factors
- Improper alterations
A combination of two or more of these factors is often responsible for a failure of the building or some of its components. Finding the primary cause may take significant effort, considering the complex behavior of partly braced, light-gauge structures under load. Metal roofs often cover pre-engineered buildings, and their design is also proprietary. Metal roof failures include leakage, deterioration, and wind damage. In some cases, the standing-seam roofs, designed to expand and contract with changes in temperature, fail to do so, resulting in panel buckling, fastener failure, and leakage. A separate issue involves workers falling through metal roofs during installation or maintenance, and bringing claims alleging defective roof design and construction.