3D Modeling Combined with Weather Data Analysis Illustrates Expert’s Opinion / by Jeff Drake

Co-authored with Donald G. Parent, PE

Last month’s article explained how scene documentation in a slip-and-fall case resulted in the discovery of physical evidence of the building failure that contributed to the accident. The failure mechanism was a frozen and fractured PVC pipe that allowed water to fill an overhead soffit structure, leak out, and create icy conditions on the pavement. While the physical evidence demonstrated the failure, it was still necessary to understand the sequence of weather events that caused this failure. A series of illustrations depicting the construction details and a graphic timeline of weather events was created to explain the cause of the building failure and resulting conditions.

Photo of the accident scene

3D model of the building structure

A 3D computer model was created from building plans, photos, and on-site measurements. The model was utilized to create a series of 3D views that were incorporated into a comprehensive presentation used to explain the building failure mechanism. The 3D model also provided input into a thermal Finite Element Analysis (FEA) model that was used to determine the thermal behavior of the column structure under varying weather conditions.

3D model reconstruction

Weather Data Timeline

A weather data timeline was developed to show alternating periods of freezing and thawing combined with precipitation events over the four weeks preceding the accident on January 26th. Post-accident weather data analysis also provided the basis for concluding the conditions photographed eight days after the accident accurately reflected the conditions expected.

CLICK THROUGH THE SLIDESHOW BELOW TO SEE THE WEATHER DATA TIMELINE

The ice sheets on the cold-soaked column illustrate the flow of water from the overhead soffit to the ground below. Soffit panels were deformed by the weight of water and ice as shown in the photos below.

Photos of the cold soaked concrete and brick column

Conclusion

Combining the 3D computer model of the documented building elements, accident scene photos, and weather data enabled the expert analysis that determined the building failure was a direct cause of the ice forming in the area where a plaintiff sustained serious injuries.

In addition, a Thermal Finite Element Analysis model was created to demonstrate the temperature behavior of the cold-soaked masonry column under the weather conditions that occurred. This will be described in a future article.

CO-AUTHOR NOTE:
Donald G. Parent is a licensed professional engineer (PE) with more than 35 years of experience in the design and analysis of mechanical and electrical products and systems.  Mr. Parent provides engineering consulting and expert witness services relating to product design, process development, and product launch, as well as patent and intellectual property-related matters. He has testified and been deposed as an expert on product design, safety, and intellectual property cases.