Selected Projects

Automotive Accident Reconstruction: A Truck Rollover Accident Reconstruction Summary
An accident occurred in the Washington, D.C. area a few years ago where a dump truck rolled over onto another vehicle in an intersection and fatally injured the automobile driver.

The dump truck, with a total load of over 57,000 pounds, was carrying excavated soil across the city line where load limits for its class of wheelbase were lower than that at its origination point. The truck's route took it onto a two way residential street. The street's downgrade, overhanging foliage, parked cars, traffic signals, and the upcoming intersection coupled with a 25 mph speed limit, provided the necessary circumstances for the accident. When descending the grade, the driver began to apply his brakes, but when the truck did not slow down fast enough, he pumped his brakes even more. The uneven brake forces caused the tires to leave long skid marks as the truck reached the intersection on a red signal. At this point in an attempt to avoid collision with the crossing traffic, the driver steered hard to the right. The truck entered the intersection, impacted a crossing vehicle, and then rolled over onto a passenger vehicle waiting to enter the intersection.

Exponent's automotive engineers were called to investigate and reconstruct this accident. A thorough review and investigation was undertaken which included direct measurements to determine the truck's center of gravity location. Exponent's accident analysis showed that the truck's initial speed, which exceeded the speed limit, in combination with the steering input upon entering the intersection, provided the necessary lateral forces needed to tip it over.

Turbine Explosion and Investigation
When an IPP plant in Ashland, Virginia suffered a catastrophic fire and explosion, Exponent deployed a field team from the Alexandria office to investigate. The 122 MW gas turbine was a total loss and detailed on-scene documentation of the incident was undertaken. Engineering investigations by our consultants examined metallurgical, thermal, and mechanical issues associated with the loss. Operational records of the plant's DCS system were studied. The turbine and generator set were examined and selected components were analyzed in Exponent's Alexandria metallurgical laboratory for clues as to what happened.

Exponent found that a fatigue failure of a blade in the 4th stage of the turbine had occurred. An engineering stress analysis of the turbine blades and a mechanical analysis of the turbine rotor were then undertaken. Exponent staff provided engineering consulting services to the plant owners in support of litigation arising from the incident.

Concrete Bridge Collapse in the Washington, D.C. Area
A few years ago the falsework for a concrete bridge collapsed in the Washington, D.C. metropolitan area. The bridge was in the process of being demolished and the falsework had been installed to protect the workers and collect the debris during the demolition. One Sunday morning, a portion of the system fell which fatally injured one worker and severely injured another. Exponent's engineers were retained by one of the co-defendants in the litigation to determine why the bridge falsework collapsed.

Exponent reviewed the design drawings, examined the erection drawings and implementation procedures, inspected the failed hardware including steel beams, girders, support brackets, bolts, and connections, and evaluated the epoxy used to secure the bracket connections. In addition, we thoroughly examined several field changes that had occurred during the demolition. Utilizing sophisticated finite element analysis modeling techniques in our investigation, Exponent was able to develop a sequence of events to explain what specifically happened in the accident and more importantly, the specific cause of the collapse. This information was later provided in two reports to assist our client in this litigation.

Exterior Insulation and Finish Systems (EIFS)
Exterior Insulation and Finish Systems (EIFS), commonly known as "synthetic stucco", is widely used in building construction. Architects and designers employ this material because of its versatility as a building facade. When it is used on light wood-framed structures, though, moisture intrusion poses a potential problem. If the intruding moisture becomes trapped between the system and the wood sheathing, the sheathing can decay.

Exponent became involved with this problem in 1995, after a $6 billion class-action lawsuit was filed in Wilmington, NC. Several hundred homes in the area were affected, and thousands more may be at risk throughout the country. Because EIFS moisture intrusion was originally thought to be a regional problem, many builders dismissed the issue and continued to use the product. However, by testing homes around the country and showing results similar to those from North Carolina, Exponent demonstrated that it is not a regional problem, but a national one.

Exponent also inspects and provides consultation for commercial properties, such as multi-story condominium units, community colleges, and the like. We are currently involved in inspecting homes and commercial properties throughout Northern Virginia, Washington, and Maryland. Recognized as the region's leading engineering consulting firm, Exponent offers services ranging from inspection work to expert testimony in support of litigation.

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