Design of Roadside Barrier Systems Placed on MSE Retaining Walls (2010) / Chapter Skim
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50 The objectives of the bogie tests include quantification of the movement of the barrier, coping, and moment slab system and measurement of the force distributions in the reinforcement strips due to a design impact load. To help plan the bogie test, wall and finite element models were developed and impact simulations using the bogie impactor were performed using LS-DYNA.
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at the second layer. Therefore, the unfactored total load per strip was 4.433 kN (1.0 kips)
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higher that observed in previous dynamic bogie testing. The moment capacity of the "toe" of the safety shape is large and, thus, typically restricts failure to the upper wall portion of the barrier.
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Contact Although LS-DYNA features some of the most advanced contact algorithms available, capturing interaction between solid and beam or shell elements is rather complex. The requirement of matching nodes to merge the reinforcing steel inside the concrete continuum would dictate the creation of elements with poor aspect ratios and the creation of unnecessarily small element sizes, which has a significant effect on time step control (24)
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as material MAT type 159 developed by APTEK (24)
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In Equation 5-2, Fc(I1, κ) can be expressed as: where X(κ)
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Bogie Vehicle The Texas Transportation Institute (TTI) test bogie is a 2,268 kg (5,000 lb)
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57 0 0.2 0.4 0.6 0.8 1 1.2 0 50 100 150 200 250 300 350 400 450 0 0.1 0.150.05 0.2 0.25 0.3 0.35 G ra vi ty (g )
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fracture the wall panel and/or result in sufficient movement of the panel to cause pullout of the reinforcing strips. It was theorized that some of this "excessive movement" in the barrier– moment slab system might be attributed to the model's neglect of friction along the sides of the overburden soil and moment slab.
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soil and overlying pavement surface that is continuous across the moment slab interface will increase the overall resistance of the system to movement. A second model was constructed with frictional contact on each side of the barrier–moment slab system and soil [Figure 5.12(b)
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60 A1C1 A2C2 B1 B2 D1F1 D2F2 E1 E2 Figure 5.13. Strip location indicator.
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shown in Figure 5.15. The maximum dynamic displacement was 99 mm (3.9 in.)
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63 -3 -2 -1 0 1 2 3 4 5 6 7 0 0.05 0.1 0.15 0.2 0.25 0.3 Fo rc e (ki ps )
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load decreases along its length. The loads in the strips attached to the wall panel below the point of impact in the middle of the barrier section have similar distributions.
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impact was slightly offset from the centerline of the middle barrier section to align with one of the reinforcement strips (D1)
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66 0.00 -0 .0 7 -0 .2 3 -0 .2 8 -0 .4 6 -0 .4 8 -0 .4 2 -0 .1 9 -0 .1 2 0 1 2 3 4 5 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 Pa n el H eig ht (ft ) Bending Moment (kips-ft/ft)
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(7 in.) from the face of the panel which corresponds to the planned location of strain gages in the test installation.
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-4 -2 0 2 4 6 8 0 0.05 0.1 0.15 0.2 0.25 0.3 Time (sec)
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The distribution of the shear load, vertical load, and bending moment along the panel at the time of peak force during the impact is shown in Figures 5.34, 5.35, and 5.36, respectively. The predicted shear load was 6.98 kN (1.57 kips)
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the panel by ACI specifications (29) (12.9 kN or 2.9 kips)
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concrete placed on top of the wall panels. The moment slab connecting the precast barrier–coping sections was cast in place in two 9.14 m (30 ft)
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The placement of these strain gages was selected to measure the maximum tensile load in each layer of reinforcement as well as give an indication of the distribution of forces in the lateral, longitudinal, and vertical directions. Five strain gages were used on the upper reinforcement layer, and three strain gages were placed on the lower reinforcement layer.
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Data from Accelerometers The accelerations at the top of the barrier and end of the moment slab exceeded the range set for the accelerometers at these locations. Therefore, a portion of the signal representing the peak acceleration of the barrier and moment slab was truncated as shown in Figure 5.40(b)
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tory and displacement–time histories were calculated by integration of the acceleration data. Targets affixed to the displacement bars attached to the top and bottom of the barrier–coping section (see Figures 5.44 and 5.45)
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second number indicates the reinforcement layer. For example, with reference to Figure 5.48, gage location 1-1 is positioned away from the wall on a strip beneath the impact point in the first (upper)
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A contact switch placed on the top edge of the level-up concrete on top of the wall panels inside the recess of the coping indicated that the coping contacted the wall panel from 0.0784 to 0.1186 sec, which, as shown in Figure 5.50, corresponds to a period of time after maximum impact load. Thus, the barrier–coping section continued in motion under its own momentum as the impact loads were decreasing.
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78 2' -6 1/ 2" 2' -5 1/ 2" 1' -2 1/ 2" 4' -6 " 8' or 16' B ogi e 0.
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79 Figure 5.48. Location of strain gages and labeling (Test 1)
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and 20 mm (0.79 ins)
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ing because the short length of this precast barrier section caused other failure modes to occur at similar failure loads. Cracking in the soil was observed approximately 1.22 m (48 in.)
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82 (a) Front side of the barrier Impact Point 8.43 ft 15-in.
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range set for the barrier accelerometer. Consequently, these data must be analyzed with appropriate caution.
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associated velocity–time and displacement–time histories are shown in Figure 5.60. Targets affixed to the displacement bars attached to the top and bottom of the barrier–coping section (see Figures 5.61 and 5.62)
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as shown in Figure 5.65. Note that two strain gages were used at locations 2-1 and 2-2 adjacent to the wall panel at the point of impact to provide some measurement redundancy at the location expected to experience maximum tensile loading.
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86 (c) Velocity (d)
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87 (b) Velocity (c)
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88 (b) Velocity (c)
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89 Figure 5.62. Location of displacement bars affixed on the barrier and panels (Test 2)
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Time (sec)
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of the barrier of 25 mm (1 in.)
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front edge of the panel due to contact with the inside face of the coping. The bonding of the leveling concrete to the top of the wall panel caused the top edge of the wall panel to spall as shown in Figure 5.72(b)
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93 (a) Front view of the barrier Impact Point 6.88 ft (b)
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94 (c) Side view of the barrier (d)
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95 (f) Closeup back view of the barrier Figure 5.71.
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96 (b) Barrier (c)
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97 (c) Velocity (d)
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98 (b) Velocity (c)
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99 Load in the Reinforcement Strips A total of eight strain gages were used to instrument the strips to capture the tensile forces transmitted into the reinforcement during the dynamic bogie vehicle impact. To enable comparison of loads on the strips, the locations of strain gages were assigned a numeric designator as shown in Figure 5.81.
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in this figure, there was some increase in force in the strips observed after the time of maximum barrier impact load, but the increase was not as significant as that seen in Test 1. The maximum 50 msec average design strip loads corresponding to a design impact load of 240 kN (54 kips)
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101 where 312.13 kN (70.17 kips) is the maximum 50 msec average impact load measured for the vertical wall barrier over 2.43 m (8 ft)
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Panel Analysis The wall reinforcement was instrumented with a total of five strain gages to capture the resistance of the panel during the bogie impacts as shown in Figure 5.85. The maximum compressive strain of 0.00022 occurred at 0.056 sec (see Figure 5.86)
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103 (a) Front view of the barrier Impact Point 8.28 ft 7.17 ft 6.51 ft (b)
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104 (c) Side view of the barrier (d)
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105 shown in Figure 5.87(c) , extended 18.29 m (60 ft)
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106 (b) Barrier (c)
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107 (c) Velocity (d)
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108 (b) Velocity (c)
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109 determine angular and translational displacement of the wall panel from analysis of high-speed film. From the film analysis, the maximum dynamic displacement of the panel was 7.6 mm (0.3 in.)
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110 Time (sec)
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111 Time (sec)
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less than the movement observed in the previous test of the vertical barrier with the 8 ft strips. Panel Analysis The wall reinforcement was instrumented with a total of five strain gages to capture the resistance of the panel during the bogie impacts as shown in Figure 5.101.
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113 (a) Front view of the barrier Impact Point 5.77 ft 20-in.
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114 (c) Side view of the barrier (d)
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115 shown in Figure 5.103(c) , extended 18.29 m (60 ft)
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maximum dynamic horizontal displacement of the panel at the bottom layer of reinforcement varied from 0 mm to 5 mm (0.19 in.)
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117 Test 1 Test 2 Test 3 Test 4* Test Installation Barrier Type New Jersey Vertical Wall Vertical Wall Vertical Wall Reinforcement 16 ft long strip (4 per panel)
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120 0 10 20 30 40 50 60 70 80 90 0 0.1 0.150.05 0.2 0.25 Time (sec)
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121 Layer Static Load by AASHTO LRFD (kips) Dynamic Load Measured (kips)
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122 -0.0025 -0.002 -0.0015 -0.001 -0.0005 0 0.0005 0 0.05 0.1 0.15 0.2 0.25 Time (sec)
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