Company: J. C. Banks Construction, LLC

Industry: Bridge Maintenance

Location: Port Saint Lucie, FL

The Company:
Julio C. Banks, MSME, PE & CGC is the owner of J. C. Banks Construction, LLC established in 1993. Julio has had direct experience in the analysis and design of thermo fluids (incompressible & compressible) flow as well as structural engineering consulting. Julio has worked in diverse industries such as Fossil and Nuclear (Stone & Webster), Military-grade Weapons (General Electric), Turbojet (Pratt & Whitney) and Turboshat (Pratt & Whitney and Siemens-Westinghouse), Airframes (Northrop Grumman, and Piper Aircraft), as well as commercial and residential construction including General Contracting. Numerical Analysis and Solution Methods is the passion of Julio who considers the subject of computational algorithms a hobby.

The Challenge:
A bridge maintenance mobil-frame was arbitrarily modified by the fabricator. The base of the frame was doubled in width. This is a typical example where no thought was given to the response of the platform such as lateral deflection due to the increase in width of the platform. The original fabricator maintained the single 2x2x0.124 HSS made from steel. During the modification study, the shop proposed the use of double the original 2x2x0.124 HSS (henceforth, the HSS) without any offset. I promptly demonstrated that a 6” minimum offset would be required to take advantage of the parallel-axis theorem use of the square-influence of the offset dimension multiplying the cross sectional are of the HSS (See Image Above).

The Solution:
The solution was made most effective by the use of the combined application of Mathcad (for manual calculations), IronCAD (for solids modeling) FEMAP (for FEA Pre- and Post-processing) and NEi Nastran (for FEA solution, also known as “the solver”) for the structural deflections and stresses. I have used Mathcad, IronCAD, FEMAP and NEi Nastran for over twelve (12) continuous years and find such combination of analytical tools to be the most cost-effective method of solution especially for solo-consultants.

Mathcad Manual Analyses
The first step in a structural analysis is to determine, at a global level, the geometry and material to be used for a given set of loads. Mathcad is the best cost-effective means of achieving cost-effective and prompt solutions. Once the most promising design candidates are selected, then the generation of detail geometry proceeds to be performed using IronCAD solids modeling.

IronCAD Solid Modeling
IronCAD, which I believe is the best solid modeling software, easily allows me to create a full 3D solid model of the frame. Additionally, IronCAD is especially useful for analyst engineers since it allows the “slicing” of 3D surfaces and solids to accommodate the FE (Finite Elements) entities (nodes and elements). With its short learning curve and ease of use, I can shorten the project time by spending more time on the analysis versus the design aspects.

NEi Nastran Finite Element Analyses (FEA)
I worked on a bridge maintenance frame project for a client with the objective of reducing the lateral deflection of the frame from 7” to 3/4”.

This study was required to understand the structural adequacy of a mobile frame and catwalk designed to be used for bridge maintenance and repair by a crew of maximum two occupants. Its design needed to meet Occupational Safety and Health Administration (OSHA) requirements.

In order to effectively ensure these requirements, Julio C. Banks used NEi Nastran FEA software to run a structural analysis. The mesh consisted of plate and beam elements for the walking surfaces and tubular elements for the supporting structure. A steady-state gravity load was applied, in accordance with OSHA requirements, to represent the weight of the occupants. Lastly, fixed constraints were placed on the supporting structure to represent real world conditions. The FEA model shown in Figure 1 was created using IronCAD and Figure 2 shows the FEA solution.

The model was analyzed with the objective of reducing the lateral deflection of the frame from 7” to 3/4”. By using the NEi Nastran FEA software, Julio was able to adjust localized structural properties (such as moment of inertia by offsetting a new HSS member) to produce reactions at the supports, as well as beam and plate stresses and deflections. With these tools in hand, both the customer’s and OSHA’s specifications were met before any prototypes had to be manufactured.

Having used the software for over 14 years, I believe that “NEi Nastran is truly reliable software allowing him to make a commitment to his consulting client and deliver without any delays.”

Results:
This case can serve as a cautionary case due to the ease of use of current FEA (Finite Element Analysis) software at affordable prices. It is recommended that, at a minimum, companies should have their design reviewed by either in-house consultant or independent consultants to ensure that a FEA user has not made critical errors during the FEA modeling and interpretation of results. This warning is especially of greatest importance if the design is mass produced such as consumer products with potential harm to the users in the event of a structural failure.
 

"IronCAD, which I believe is the best solid modeling software, easily allows me to create a full 3D solid model of the frame. With its short learning curve and ease of use, I can shorten the project time by spending more time on the analysis versus the design aspects.”
   Julio C. Banks, MSME, PE & CGC
   Owner of J. C. Banks Construction, LLC