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Gaddy v. Terex Corp.

United States District Court, N.D. Georgia, Atlanta Division

August 2, 2017




         This matter is before the Court on Defendants Terex Corporation, Terex South Dakota, Inc., and Terex Utilities, Inc.'s (collectively, “Defendants” or “Terex”) Motion to Strike Rebuttal Report of Nathan Morrill [380].

         I. BACKGROUND

         A. Facts

         This is a products liability action stemming from the failure of a 2002 Terex Hi-Ranger XT 60/70 boom, Serial No. 2021020554 (the “Subject Boom Truck”), an aerial lift device. Terex XT aerial devices are commonly utilized by tree trimming companies.

         On April 9, 2014, Plaintiff Jeffrey Gaddy (“Plaintiff”) was in the bucket of the Subject Boom Truck when the lower boom stub fractured, causing Plaintiff to fall to the ground. Plaintiff suffered spinal injuries resulting in paraplegia. Plaintiff claims Terex negligently manufactured and designed the Subject Boom Truck, and that it failed to warn him of certain dangers. Plaintiff also claims that the steel used in the lower boom stub did not meet Terex's design specifications.

         In support of his negligent design claim, Plaintiff identified Nathan Morrill, P.E. as a design expert. Mr. Morrill issued a report [393.1] (the “Original Report”) that stated a variety of opinions regarding Terex's design of the Subject Aerial Device, including his interpretation of the standards promulgated by the American National Standards Institute (the “ANSI Standards”), the applicability of the ANSI Standards to Terex's design of the Subject Aerial Device, and the feasibility of alternative designs. Mr. Morrill's opinions included that the ANSI Standards required, among other things, that calculated or known stresses may not exceed 50 percent of the yield strength of the material-a standard known as a “2.0 safety factor.” (Original Report ¶ 51). In this case, that would mean stresses could not exceed 35, 000 psi. (Id. ¶ 81). Mr. Morrill concluded that Terex ignored the ANSI Standards when assessing stress concentrated areas and that the boom had a 1.47 safety factor from a crane testing standard. (Id. ¶¶ 66-67). Mr. Morrill also opined that Terex failed to apply stress concentration factors and dynamic load factors to their preproduction calculations as required by ANSI A92.2. (Id. ¶ 182). Mr. Morrill created Finite Element Analysis (“FEA”) models of three lower boom stubs in the XT series, and offered two proposed alternative designs of the XT 60 lower boom stub. (Id. ¶¶ 108-153). Mr. Morrill concluded that the cracking and failure of the XT boom was caused by Terex's use of weaker steel and Terex's design of the boom, and that, had the XT 60 been designed to meet ANSI A92.2 standards, it would not have failed in this case. (Id. ¶ 187).

         Terex designated civil engineer Vijay K. Saraf, Ph.D. as an expert regarding the design of the Terex XT 60 boom. On September 30, 2016, Terex produced Dr. Saraf's expert report [393.4] (“Saraf Report”). Dr. Saraf opined that ANSI Standards addressed only static loading conditions and that stress concentrations could, in practice, be ignored. (Saraf Report at 16; Saraf Dep. [393.5] at 153). Dr. Saraf further opined that Terex's testing of the XT-60/70 boom prototype exceeded ANSI Standards because they applied a safety factor of 1.1 when accounting for stress concentrations, instead of ignoring stress concentrations. In his deposition, Dr. Saraf justified his opinion that stress concentrations could be ignored by giving examples from design criteria for buildings and bridges. (Saraf Dep. at 47. Dr. Saraf also gave opinions regarding Mr. Morrill's use of FEA models, opining that using FEA-aided measured stress is not “good engineering practice” and would lead to an “impossible design goal.” (Saraf Report at 16). He also opined that it was “impossible” to design any aerial lift device that would satisfy Mr. Morrill's interpretation of ANSI A92.2 that stresses could not exceed 50% of yield strength based on verified stress concentration factors and dynamic loads. (Id. at vii, ¶ 18).

         Plaintiff designated Mr. Morrill as a rebuttal expert to rebut Dr. Saraf's opinions. On November 4, 2016, Plaintiff produced Mr. Morrill's Rebuttal Report [393.3]. The Rebuttal Report included the following opinions:

37. Based off of the new information I have reviewed, my analyses, my professional experience design mobile equipment including aerial lifts, and my education as a mechanical engineer, I add to the opinions set forth in my first report and those mentioned above.
38. Buildings and bridges are designed to different standards and regulations than aerial lifts, the design requirements of each are different due to the loading and operating conditions.
39. Dr. Saraf is wrong in assuming that stress concentrations and dynamics can be ignored for aerial lift design. Stress concentration factors when subjected to cyclic loading cannot and should not be ignored. Doing so reduces the life of a design and can lead to failure which will endanger the operator of an aerial device.
40. ANSI A92.2-2001 specifically instructs designers and manufacturers to take into account the effects of stress concentrators and dynamic loading because they cannot be ignored.
41. Terex S.D. measured and calculated stresses in 1996 for the XT 52 lower boom stub, and should have been put on notice that the stress concentration factor for the area of failure was at least 1.85. These concentration factor is [sic] a result of Terex SD's design of this location, and is unique to this geometry. This factor can be reduced or removed with designs that better distribute the stresses and load paths.
42. The XT 52 lower boom stub did not meet ANSI A92.2-2001.
43. Terex S.D. should have known from 1996 forward that a stress concentration factor of 1.1 was inappropriate for the weld in the lower boom ...

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