The design of longitudinal barriers using reinforced concrete is typical in roadside safety design. Roadside safety hardware such as bridge rails, median barriers, and transitions are designed to safely contain and redirect impacting vehicles without imposing any significant risks to the occupants. Manual for Assessing Safety Hardware (MASH) guidelines are followed to design a barrier for given impact criteria at a specific test level. As full-scale crash tests of new designs are expensive and time-consuming, finite element modeling and simulation of the impact event is often involved. In LS-DYNA, one of the most popular software in roadside design, there are multiple material models for concrete modeling and there is no specific guideline on the selection of the concrete material model.&nbsp;Manitoba concrete bridge rail was selected as a representative reinforced concrete bridge rail for the study. The barrier has a height of 1250 mm (49-1/4 in), a base width of 450 mm (17-3/4 in) and a top width of 250 mm (9-7/8 in). The full-scale crash test installation of the barrier consisted of a concrete mix with a compressive strength of 45 MPa (6500 ksi) and Grade 400W Canadian Metric Rebar steel reinforcement. The full-scale crash test setup included a joint and the tractor-van trailer impacted the barrier 914 mm [3ft] upstream from the joint. The design of the end section of the barrier was altered to match the design strength of the interior section; it was done to ensure that the interior section is equally sufficient for MASH TL-5 impact loading.&nbsp;In this study, MAT_CSCM_CONCRETE and MAT_RHT with default parameters were used to create two reinforced concrete barrier FEA models of a barrier in LS-DYNA. The barrier FEA models were impacted consecutively by two tractor-van trailers under MASH Test Level 5 (TL-5) criteria. The initial impact on both barrier FEA models was evaluated against the full-scale crash test. The second in-series MASH TL-5 impact into both barrier FEA models was compared and analyzed. Based on the concrete damage, effective plastic strain behavior and failure pattern/mechanism of two consecutive tractor-van trailer impacts observed in the simulations, the most representative material concrete material model was selected for further study and is recommended for future studies involving dynamic simulations with multiple in-series impacts.&nbsp;The study considered only a few major factors such as deflection, concrete erosion, and damage mechanism for comparison of the FEA models. The leading tractor-van trailer impacts were comparable to the full-scale crash test for both models, but the erosion in the second tractor-trailer impact was considered excessive in MODEL272. While the deflections observed in both simulations did not fully agree with the full-scale crash test, the yield line damage mechanism was observed only in MODEL159. Based on the simulations, MODEL159 was selected as a representative model for further study. MAT_CSCM_CONCRETE is recommended for simulating impacts into reinforced concrete impacts when a simplified approach with automatically generated input parameters are used.

Reinforced Concrete Barrier Modeling of Multiple In-Series Impacts in LS-DYNA

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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