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Simulations of a Truck Crashing Into a Reinforced Concrete Wall

Kiewit Corporation, a diverse company specializing in construction, mining, oil, gas, power, transportation, and water projects, was contracted to design a boundary wall around a large electrical switching station. One of the requirements of the design was to prevent a medium duty truck from penetrating through the wall, as detailed in the crash test specifications of ASTM F2656-07. Kiewit contacted CAE Associates to request dynamic structural analyses to simulate the wall impact events for two different wall designs at different impact angles and locations. They also required a detailed structural analysis report to include with their final design.

CAE Associates developed six models to simulate the proposed wall designs, impact angles, and impact locations. These models were developed with Workbench/LS-Dyna and solved with the LS-Dyna Explicit Dynamics finite element code. Two different wall designs were analyzed as well as impacts at the vertical support columns and halfway between the columns. In addition, both direct and off-angle impact orientations were analyzed as well as impacts above the base of the wall. One of these models is shown in Figure 1.
 

Figure 1: Complete LS-Dyna Model of the Truck and Wall


These highly complex models included the following features:

  • A representative section of the wall containing two support columns.
  • A large block of soil beneath the concrete base and column foundations.
  • The soil model was calibrated to simulate deflections provided in a geotechnical report.
  • A concrete model was used for all wall, base, foundation, and column parts.  This model was calibrated and tested to the specified unconfined compression strength.  A material damage model was included.
  • All rebar, studs, anchors, and bolts were included in the model, using beams and shell elements.  A section of the model is shown in Figure 2 with some of the concrete elements hidden to show the underlying support structure.
  • Material failure was included in all concrete and steel parts, with associated element erosion.
  • Contact with friction was included between all parts.
  • A model of a medium duty truck with a specified total weight, payload, and impact velocity.
  • All parts were preloaded with gravity prior to applying an initial velocity to the truck.

     
Figure 2: Section of the Column and Foundation Showing the Internal Rebar and Support Structure

 

The simulations showed that, while some of the rebar and concrete was damaged, none of the truck components penetrated through the wall for any of the evaluated wall designs, impact angles, and impact locations.  Figure 3 shows impact deformations at different times for a 30° impact angle striking at a column location.
 

Figure 3: Crash Deformation History – Wall Design 1, 30° Impact Angle, Column Strike


Figure 4 shows deformations of the second wall design for a perpendicular impact halfway between two columns.  Plots of internal and kinetic energies showed that most of the kinetic energy is converted into internal energy in the truck (plastic deformation and failure), some of the energy is transferred to the wall and the soil, while the remainder is lost to friction. Damage to the concrete, rebar, and other reinforcement parts was also evaluated.
 

Figure 4: Maximum Wall Deflection – Wall Design 2, Direct Impact, Mid-Span Strike


 

A plot of final damage in the wall is shown in Figure 5 for a perpendicular mid-span impact at an elevated location.

 

Figure 5: Concrete Damage After Impact – Wall Design 2 (Red = full damage)


Based on the simulation results for the initial wall design showing no penetration of the truck through the wall, Kiewit decided to evaluate a second design with a shorter wall and considerably greater spacing between the columns.  This design showed more deflection and damage as compared to the original design but still no penetration of the truck components through the wall. 

 



As a result, Kiewit decided that the second design was acceptable and would also provide considerable material and cost savings.  Ultimately, CAE Associates not only provided Kiewit with all of the required crash simulations and reporting, but also helped them propose and verify a considerably more efficient design.