Design Guidelines for Test Level 3 through Test Level 5 Roadside Barrier Systems Placed on Mechanically Stabilized Earth Retaining Walls (2022) / Chapter Skim
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Pages 72-99
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72 4 MOMENT SLAB WIDTH FE models of TL-4 and TL-5 BMS systems were developed to evaluate the dynamic response of the systems when subjected to vehicle impact loading. The analyses were performed using the commercially available FE software LS-DYNA (6)
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73 The components of the BMS model (precast barrier, leveling pad, cast-in-place moment slab and soil) were modeled using solid elements.
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74 b) Contact Algorithm The modeling of this large deformation problem required the implementation of advanced contact algorithms to successfully capture the interaction between all free surfaces.
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75 Figure 4-2 Yield surface of the cap model (6)
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76 yield surface at the elastic range. They are usually evaluated by fitting a curve through failure data taken from a set of triaxial compression tests (6)
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77 4.1.2 Analyses for Test Level 4 Impact A nonlinear FE analysis was performed to investigate the dynamic behavior of a BMS system subjected to a MASH TL-4 impact. The principal objective was to obtain the optimum width of moment slab required to contain a MASH TL-4 test vehicle with a limiting permanent displacement of 1.0 in.
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78 d) Three-dimensional view Figure 4-3 BMS system details for TL-4 analyses (Continued)
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80 a) Lateral impact force (Ft)
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81 Figure 4-6(c) through Figure 4-6(e)
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82 In all cases, the relative displacement at the coping is very small which indicates that the shear dowels and the connection between the barrier and the moment slab are adequate to withstand this impact level. At the top of the barrier, the relative displacement is more appreciable.
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83 TL-5 2'-10"3'-6" 3' 1' #7 @ 8" 512" 1'-4" 8" 1' 7' 112" 1' A-A B-B 35° B A a) Concrete barrier detail b)
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84 Since the impact load applied by a fully loaded tractor-trailer is significantly larger than a MASH TL-4 impact, the number of shear dowels was increased from two #9 steel bars to three #11 steel bars. The shear dowels were embedded 18 in.
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85 The time history of the impact load shows that the maximum 50-msec. average force (Ft)
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86 In the longitudinal and vertical direction, the maximum 50-msec. average impact loads were 94.4 kips (420.1 kN)
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87 e) Relative displacement at B4-B5 f)
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88 a) Description of the Barrier and the Moment Slab The cross section of the 48-in.
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89 The methodology followed to design and model the 48 in.
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90 The time history of the impact force indicates that the maximum 50-msec. average force (Ft)
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91 The maximum displacement of the barriers occurred close to the IP and was 2.12 in.
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92 a) Displacement at IP b)
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93 4.2.1 Static Analytical Solution The static analyses for sliding and overturning were conducted using equilibrium equations. The static force (Fs)
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94 Equivalent Static Load, L hh Rotation Point B Rotation Point A Overburden Soil BA W lA lB Moment Slab Traffic Barrier C.G. Panels s Finished Grade Figure 4-15 Detail of the rotation points on the BMS system.
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96 The results of the numerical simulation showed that the BMS system was controlled by overturning rather than sliding. Figure 4-17 presents the results as a load versus displacement curve, and compares them with the analytical solution using equilibrium equations.
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97 Table 4-3 Comparison between analytical solution and FE analyses Test Level Rotation Point A (RP-A) Rotation Point B (RP-B)
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98 a) Rotation Point B (RP-B)
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99 However, significant sliding was also observed in the analyses for TL-5. Therefore, both criteria should be checked for the TL-4 and the TL-5 cases.
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