Design of Roadside Barrier Systems Placed on MSE Retaining Walls (2010)

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123 A full-scale crash test was performed to validate the prelim- inary design guidelines and/or modify them as necessary. The finite element analysis using LS-DYNA was performed to help plan and predict the outcome of the TL-3 crash test. 6.1 10 ft High MSE Wall and Barrier Study Description The total length of the installation was about 27.43 m (90 ft). The MSE wall on which the nine 3.05 m (10 ft) long precast barrier–coping sections were placed was approximately 2.74 m (9 ft) tall and comprised full and half-panel sections that were approximately 1.52 m (5 ft) wide. The bottom wall panels were placed on a 304.8 mm (1 ft) wide × 152.4 mm (6 in.) thick concrete leveling pedestal. The MSE wall had three layers of reinforcement. The steel reinforcement strips were 3.05 m (10 ft) long. The wall panels were recessed inside the coping of the precast barrier–coping sections a distance of 19 mm (0.75 in.). The moment slabs connecting the 3.05 m (10 ft) long precast barrier–coping sections were cast in place in three 9.14 m (30 ft) lengths. The three 1.37 m (4.5 ft) wide × 9.14 m (30 ft) long moment slabs were connected to one another using two No. 9 shear dowels across each joint. The barrier portion of the precast barrier–coping sections consisted of a vertical concrete barrier conforming to the Texas Type T221 traffic barrier. The barrier portion was 0.81 m (2.67 ft) in height (measured from the roadway to the top of the barrier) and 304.8 mm (12 in.) wide at the top. At the direction of the NCHRP Project 22-20 panel, the draft AASHTO Manual for Assessing Safety Hardware (MASH) was used for the full-scale crash test. MASH test designation 3-11 involves a 2,270 kg (5,000 lb), 0.5-ton, four-door pickup truck (denoted 2270P) impacting the barrier at a speed of 100 km/h (62 mph) and an angle of 25 degrees. At the time the finite element analysis was performed, a model of the 2270P design vehicle was not available. Therefore, the impact sim- ulation was performed with a model of a Chevrolet C2500 pickup that conforms to the design test vehicle of NCHRP Report 350 (3). 6.1.1 Calculation of MSE Wall Capacity AASHTO LFRD (2) was used to estimate the forces expected in the reinforcement strips due to both gravity and impact loads for the planned MSE wall with 3.05 m (10 ft) long strips. This information ultimately was compared to forces estimated through numerical simulation and measured in the TL-3 crash test. The unfactored pullout resistance of the reinforcement was calculated to be 9.129 kN (2.052 kips) (F* = 1.668) at the upper- most layer, 15.183 kN (3.413 kips) (F* = 1.524) at the second layer, and 19.946 kN (4.484 kips) (F* = 1.381) at the third layer. The unfactored static load per strip due to gravity was calcu- lated to be 3.06 kN (0.688 kips) at the uppermost layer, 5.359 kN (1.205 kips) at the second layer, and 7.467 kN (1.679 kips) at the third layer. In this analysis, the traffic surcharge was not considered. The unfactored dynamic load per strip due to bar- rier impact was calculated to be 1.762 kN (0.396 kips) at the uppermost layer, 1.151 kN (0.259 kips) at the second layer, and 0.541 kN (0.122 kips) at the third layer. Therefore, the unfactored total load per strip was calculated to be 4.822 kN (1.084 kips) at the uppermost layer, 6.51 kN (1.464 kips) at the second layer, and 8.01 kN (1.8 kips) at the third layer. A sum- mary of resistance and load per strip is presented in Table 6.1. The detailed design calculations for designing the MSE test wall are provided in Appendix A. 6.1.2 Calculation of Barrier Capacity The ultimate load capacity for the 0.81 m (32 in.) tall ver- tical barrier was computed to be 440.95 kN (99.13 kips) using the yield line failure mechanism in AASHTO LRFD. The length of the failure mechanism calculated for the barrier section analyzed was 1.75 m (5.73 ft) for the 0.81 m (32 in.) tall verti- C H A P T E R 6 10 ft High MSE Wall and Barrier Study

124 • Modeling the 0.81 m (32 in.) high vertical barrier with explicit reinforcement details as shown in Figure 6.1 • Raising the wall height to reflect an MSE wall configuration composed of two rows of 1.52 m (5 ft) tall panels using a total of four layers of reinforcement • Incorporating 3.05 m (10 ft) long soil reinforcement strips • Using a density of three strips per panel for the top layer of reinforcement and a density of two strips per panel for the other layer of reinforcement • Incorporating the model of the Chevrolet C2500 pickup truck (reflective of the 2000P test vehicle in NCHRP Report 350). Figures 6.2 and 6.3 show the model setup of the 3.49 m (11.46 ft) high MSE wall with the Chevrolet C2500 vehicle model. The vehicle model was given an initial velocity of 100 km/h (62 mph) and hit the barrier at an angle of 25 degrees per Test Level 3-11 impact conditions. To enable comparison of forces and displacements, barriers and selected strip locations were assigned an alphanumeric designator that describes their horizontal position and vertical reinforcement layer. For example, strip B3-A-1st is positioned beneath the third barrier at vertical position A in the first (i.e., upper) layer of reinforcement. Figure 6.4 shows the rebar details of vertical concrete barrier and moment slab, which was modeled based on the drawings provided by RECO. Figure 6.5 shows the rel- ative position of the vehicle with respect to the middle barrier joint. This barrier joint is aligned with the joint between the two moment slab sections that were modeled. The first phase of the simulation process was to account for the steady-state conditions of the system due to the gravitational Table 6.1. Unfactored resistance and force in case of MSE wall with 10 ft long strip. Layer (1) TStatic Static Load (kips) (2) TDynamic Dynamic Load (kips) (3)=(1)+(2) TTotal Total Load (kips) P Resistance of Pullout (kips) Top 0.688 0.396 1.084 2.052(F*=1.668) Second 1.205 0.259 1.464 3.413(F* = 1.524) Third 1.679 0.122 1.800 4.484(F* = 1.381) Figure 6.1. RECO vertical concrete barrier detail. cal wall barrier. This indicates that, provided the coping has sufficient capacity to develop the ultimate strength of the bar- rier, the 3.05 m (10 ft) section length selected for evaluation in the TL-3 crash test should be sufficient for developing the primary failure mechanism for the barrier. 6.2 Finite Element Analysis The MSE wall model used in the bogie impact simulation was modified to model the proposed full-scale test installa- tion. The modifications to the model included: • Extending the model length from 9.14 m (30 ft) to 18.28 m (60 ft) by incorporating two moment slab components each of which was 9.14 m (30 ft) long • Incorporating two 22.6 mm (8⁄9 in.) diameter, 0.91 m (36 in.) long dowel connectors between the moment slabs

125 B1B2B3B4B6 B5 Joint between Moment Slab (a) Three-dimensional view (b) Elevation view Figure 6.2. MSE wall, barrier, and C2500 model. Figure 6.3. Downstream view of model showing profile of barrier and embedded soil strips.

126 0 1000 2000 3000 4000 5000 6000 7000 0 0.1 0.2 0.3 0.4 0.5 W ei gh t ( kN ) Time (sec) Simulation weight Calculated weight Figure 6.6. System reaction force of the MSE wall model. load. The weight of the system was measured and used as a con- vergence criterion for the steady-state solution. The total mass of the model for the vertical wall barrier on top of the MSE wall with 3.05 m (10 ft) long strips is 664,630 kg (45,542 slug or 1,465,258 lb mass). The weight of the system is calculated to be 6,517 kN (1,465 kips) using the mass of the finite element model and the acceleration of gravity. Therefore, after accounting for gravitational load, the weight of the model system should con- verge to the calculated system weight. The weight of the finite element model was 6,531 kN (1,468 kips) at the end of the ini- tialization step. A reasonable agreement shows that the weight of the finite element model approached the calculated weight of the model system as shown in Figure 6.6. The initialized model was then set up with the C2500 vehi- cle model, and the impact simulation was conducted. The vehicle was successfully contained and redirected by the bar- rier. Figure 6.7 shows sequential images of the impact that correspond to the following events: 0.06 sec: Maximum force on the barrier 0.1 sec: Maximum load in the strips 0.195 sec: Back slap impacts the barrier 0.345 sec: Back bumper impacts the barrier 0.5 sec: Vehicle exits the barrier Figure 6.4. Rebar detail in the barriers and panels of model. B3B4 F E D C B A F E D C B A Figure 6.5. Side view of the model show- ing the distribution of the strips.

127 6.2.1 Barrier Damage and Displacement The calculated impact force on the barrier was 248.21 kN (55.8 kips) at 0.0575 sec as shown in Figure 6.8. At 0.198 sec, the second peak impact force occurred due to the back slap impact. The damage to the concrete barrier is shown in Fig- ures 6.9 and 6.10. The concrete barrier exhibited a damage profile typically observed in impacts on barrier joints. The damage profiles shown in Figures 6.9 and 6.10 are limited to the surface elements and did not indicate failure of the barrier. The maximum displacement at the top of the barrier occurred in barrier section B4. The displacement–time history for this barrier section is shown in Figure 6.11. The initial impact induced a displacement of 41.4 mm (1.63 in.) at the top of the barrier. The barrier was rebounding back when the back slap impact occurred, which resulted in a maximum displacement of 48.5 mm (1.91 in.). As the barrier was rebounding from the back slap, the rear bumper of the pickup contacted the barrier and the barrier displacement momen- tarily increased to 37.3mm (1.47 in.). Figure 6.12 shows the displacement distribution on barrier segments B3 and B4 at 0.1 sec. (a) 0 sec (b) 0.06 sec (c) 0.1 sec (d) 0.195 sec (e) 0.345 sec (f) 0.5 sec Figure 6.7. Vehicle position at each significant moment.

128 6.2.2 Loads and Displacements in Reinforcement Strips The load–time histories for selected strips in the upper layer of reinforcement are presented in Figure 6.13(a). The 50 msec moving average is shown in Figure 6.13(b). Figures 6.14 through 6.16 show 50 msec average load–time histories for strips in the second through fourth layers of reinforcement, respectively. The maximum 50 msec average load in the strips is 18.7 kN (4.2 kips) in strip B4-A-1st [Figure 6.13(b)]. The strip loads in each layer show similar load histories, therefore, one strip was chosen to represent the load at each layer in Figure 6.17. Maximum displacement of the strips was 2.8 mm (0.11 in.) at 0.085 sec at strip B4-A-1st as shown in Figure 6.18. Because the strips and panels were tied together, the maximum displace- ment of the panel also corresponds to this value. Figure 6.19 shows the displacement distribution of the strips at 0.085 sec. 6.2.3 Panel Analysis The strain on the wall panel was evaluated as shown in Figure 6.20. The maximum compressive strain was 18 micro strains at 0.065 sec. The distribution of bending moment along the panel at the time of peak force during the impact is shown in Figure 6.21. 0 10 20 30 40 50 60 0 0.1 0.2 0.3 0.4 0.5 0.6 Fo rc e (ki ps ) Time (sec) Figure 6.8. Time history of impact force on barrier (50 msec average). (c) 0.19 sec. (at Rear Tire Hit) (d) 0.345 sec. (at Back Bumper Hit) B3 B4 B3 B4 (a) 0.06 sec. (at Max. Impact Load) (b) 0.1 sec (at Max. Strip Load) B3 B4 B4 B3 Figure 6.9. Damage to the concrete barrier at the front of the joint.

B3 B4 Figure 6.10. Damage to the back of the concrete barrier (0.1 sec). 0 0.5 1 1.5 2 2.5 0 0.1 0.2 0.3 0.4 0.5 D is pl ac em en t ( in. ) Time (sec) Top of B4 Barrier Bottom of B4 barrier Figure 6.11. Barrier displacement–time history (Barrier B4). B3 B4 Figure 6.12. Distribution of barrier displacement (Barrier B3 and B4).

130 0 0.5 1 1.5 2 Lo ad (k ips ) B4-A-2nd B4-C-2nd 0 0.1 0.2 0.3 0.4 0.5 0.6 Time (sec) Figure 6.14. Total load on the strip at second layer. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.1 0.2 0.3 0.4 0.5 0.6 Time (sec) Lo ad (k ips ) B4-A-1st B4-D-1st B5-A-1st (a) Raw data (b) 50 msec average 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.1 0.2 0.3 0.4 0.5 0.6 Time (sec) Lo ad (k ips ) B4-A-1st B4-D-1st B5-A-1st Figure 6.13. Total load on the strip at uppermost layer.

131 2.5 3 B4-A-3rd B4-C-3rd 0 0.5 1 1.5 2 Lo ad (k ips ) 0 0.1 0.2 0.3 0.4 0.5 0.6 Time (sec) Figure 6.15. Total load on the strip at third layer. 3.5 B4-A-4th B4-C-4th 2.5 3 0 0.5 1 1.5 2 Lo ad (k ips ) 0 0.1 0.2 0.3 0.4 0.5 0.6 Time (sec) Figure 6.16. Total load on the strips at fourth layer. 4 4.5 B4-A-1st B4-A-2nd B4-C-3rd B4-C-4th 3.5 2.5 3 0 0.5 1 1.5 2 Lo ad (k ips ) 0 0.1 0.2 0.3 0.4 0.5 0.6 Time (sec) Figure 6.17. Load on the strips for all layers.

132 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 0.12 D is pl ac em en t ( in) B4-A-1st B4-A-2nd B4-A-3rd B4-A-4th 0 0.1 0.2 0.3 0.4 0.5 Time (sec) Figure 6.18. Displacement in the strips at B4-A. Back Front Figure 6.19. Distribution of displacement in the strips at 0.085 sec (unit: mm). -2.0E-05 -1.5E-05 -1.0E-05 -5.0E-06 0.0E+00 5.0E-06 1.0E-05 0 0.05 0.1 0.15 0.2 0.25 Time (sec) St ra in (in ./in .) Figure 6.20. Panel strain at D1.

6.3 TL-3 Crash Test 6.3.1 10 ft High MSE Wall Construction and Test Installation An overall layout of the 3.05 m (10 ft) high MSE wall test installation is shown in Figure 6.22. The instrumented MSE wall was about 27.43 m (90 ft) long and approximately 2.74 m (9 ft) tall and comprised full and half-panel sections that were approximately 1.52 m (5 ft) wide. The bottom wall panels were placed on a 304.8 mm (1 ft) wide × 152.4 mm (6 in.) thick concrete leveling pedestal. The MSE wall had three layers of reinforcement. The uppermost layer was at a depth of 0.91 m (3 ft) below the ground surface. The vertical spacing of the suc- cessive reinforcement layers was approximately 0.76 m (2.5 ft). The steel reinforcement strips were 3.05 m (10 ft) long. The reinforcement had a density of three strips per layer per panel. The wall panels were recessed inside the coping of the precast barrier–coping sections. The barrier–coping sections rested on a 66.7 mm (2.625 in.) layer of a level-up concrete placed on top of the wall panels. The moment slabs connecting the 133 -0.01 -0.01 -0.18 -0.24 0.00 -0.01 -0.12 -0.11 0.04 -0.22 -0.16 -0.02 -0.02 0.00 -0.30 -0.34 -0.14 -0.120 1 2 3 4 5 6 7 8 9 10 -0.4 -0.3 -0.2 -0.1 0 0.1 Pa ne l H ei gh t ( ft) Moment (kips-ft) / ft Figure 6.21. Bending moment on the panel (B4-A). Accelerometer Reinforcement strips w/ strain gages Accelerometer : Concrete strain gages B8 B7 B6 B5 B4 B3 B2 B1 B0 4.5' 10' 90'-4" 30'-1" Moment slab 30'-1" Moment slab 30'-1" Moment slab SOUTHNORTH 0.5" TYP. 0.5" TYP. B8-D3 8-A6 B8-B3 B8-H6 B7-D3 B7-A6 B7-B3 B7-H6 B6-D3 B6-A6 B6-B3 B6-H6 B5-D3 B5-A6 B5-B3 B5-H6 B4-D3 B4-A6 B4-B3 B4-H6 B3-D3 B3-A6 B3-B3 B3-H6 B2-D3 B2-A6 B2-B3 B2-H6 B1-D3 B1-A6 B1-B3 B1-H6 B0-D3 B0-A6 B0-B3 B0-H6 5'-7 1/2" 3/4" 4'-1 3/8" 32" 9'-1 3/4" 24" TL-3 25° 4' 0.5" TYP. Figure 6.22. Layout of the barrier on MSE wall.

3.05 m (10 ft) long precast barrier–coping sections were cast in place in three 9.14 m (30 ft) lengths. The three 1.37 m (4.5 ft) wide × 9.14 m (30 ft) long moment slabs were connected to one another using two No. 9 shear dowels across each joint. The barrier portion of the precast barrier–coping sections consisted of a vertical concrete barrier that conforms to the Texas Type T221 traffic rail. The barrier portion was 0.81 m (2.67 ft) in height (measured from the roadway to the top of barrier) and 304.8 mm (12 in.) wide at the top. The coping was 0.61 m (2 ft) in height (measured from the bottom of the coping to the roadway). Longitudinal reinforcement in the barrier–coping section consisted of ten No. 4 bars. Trans- verse reinforcement consisted of alternating No. 5 bars spaced 254 mm (10 in.) apart. The barrier–coping sections are attached to the moment slab using No. 6 bars spaced at 254 mm (10 in.) Figure 6.23 shows a cross section of the barrier–coping sec- tion and MSE wall. Figure 6.24 shows photos of the instru- mented MSE wall before the TL-3 crash test. The barriers and panels were assigned alphanumeric designators as described earlier. The precast barrier–coping sections, concrete wall pan- els, and steel strip wall reinforcement were provided by RECO at no cost to the project. The MSE wall backfill was made of two layers: a poorly graded clean sand from the bottom of the wall to the bottom of the moment slab [2.18 m (7.15 ft)] and a limestone rock fill usually used as road base from the bottom of the moment slab to the riding surface [0.61 m (2 ft)]. The sand backfill and the road base satisfied the gradation limits of TxDOT Type B (Table 6.2) and Type A backfill material respectively. For the sand, the particle diameters corresponding to 10% fines (D10) and 60% fines (D60) were 0.25 mm and 1.1 mm, respectively, and the percent passing a #200 sieve was 0% as shown in Fig- ure 6.25. For the road base, the particle diameters correspond- ing to 10% fines (D10) and 60% fines (D60) were 0.18 mm and 14 mm, respectively, and the percent passing a #200 sieve was 7%. Both the sand and the road base layers were compacted in 0.15 m (6 in.) layers with 10 passes of a 12.9 kN (2,905 lb), 0.89 m (35 in.) wide drum roller. The in situ dry density and the water content as compacted were 17.3 kN/m3 and 6% for the sand and 23.1 kN/m3 and 3.9% for the road base. These dry densities represented 93% and 105% of the maximum dry den- sities obtained in the modified Proctor test for the sand and the road base, respectively. The friction angle of the sand was mea- sured in the direct shear test by recompacting the sand at its in situ dry density; a value of 40 degrees was obtained together with an apparent cohesion of 9 kPa (1.31 psi). The friction angle of the road base was measured in a large triaxial cell by recompacting the road base to its in situ dry density; a value of 45 degrees was obtained with a cohesion intercept of 80 kPa (11.6 psi). The modulus of the sand and the road base were measured with the Briaud Compaction Device (31); the val- ues obtained were 15.1 MPa and 67.2 MPa respectively. The friction factor (F*) used in the calculation of the strip resis- tance to pullout in the sand was calculated to be 1.84 at the ground level according to AASHTO LRFD. The particle diam- eters corresponding to 10% fines (D10) and 60% fines (D60) were 0.25 mm and 1.1 mm, respectively. The coefficient of uniformity [Cu (= D60 / D10)] was determined to be 4.4. The friction factor (F*) was calculated to be 1.84 at the ground level. 134 Accelerometer: 2 ( ) 3.54' 5' String Line for measurement of permanent displacement of barrier and panels Displacement bars are located on the centerline of the panel close to the impact point 9" 10' Displacement Bar Accelerometer Strain Gages (Top & Bottom each location) 1'-2 3/4" 5" Tape Switch Strain Gages: 13 (3: on the Panel, 10: on the Strips) Tape Switch: 1 Displacement Bars:5 4' 6" 9" 3/16" RUBBER SHIM (2 PER PANEL) 3/4" BEARING PAD 3' 2'-5 1/2" 2'-5 1/2" TL 3 6"x12" UNREINFORED CONCRETE LEVELING PAD 9'-1 3/4" Level-Up Concrete 2 5/8" Figure 6.23. Side view of TL-3 crash test with 32 in. tall vertical wall barrier.

135 Selected reinforcement strips in the MSE wall were instru- mented with strain gages to capture the tensile forces trans- mitted into the reinforcement during the full-scale crash test. A total of 14 strain gages were used. The four strips in the upper layer and the three strips in the middle layer of reinforcement on the wall panel immediately downstream from the impact location were instrumented. The simulation results indicate that these strips develop the maximum tensile loads during impact. Two strain gages were used at each selected location (one on the top of the strip and one on the bottom of the strip) to compensate for any bending in the strip. A contact switch was placed on the top edge of the traffic face (inside face) of the wall panels inside the coping recess. The switch indicates the time (referenced from impact) at which the barrier slides and/or rotates sufficiently for the coping to contact the wall panel. The wall panel attached to the instrumented strips was instrumented with three concrete strain gages to capture nor- mal strains in the panel induced from impact loads transmit- ted into the MSE wall through the soil and generated from direct contact of the barrier–coping section with the top of the wall panel. The strain gages were placed in a vertical position along the height of the panel. A strain gage was placed adja- cent to the anchorage locations for the upper and lower layer Sieve Size Percentage Retained 3 in. 0 No. 4 See Note No. 40 40–100 No. 200 85–100 Note: If 85% or more material is retained on the No. 4 sieve, the backfill will be considered rock backfill. Source: Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges (30) Table 6.2. Gradation limits for TxDOT Type B select backfill. B3B4 B5 Figure 6.24. Barrier on MSE wall prior to testing.

136 of reinforcement, and one strain gage was placed in the center of the panel between the two layers of reinforcement. An accelerometer was mounted behind and at the top of the barrier section immediately downstream of impact (which was shown in the simulation to experience the maximum load and displacement). An accelerometer also was placed on the end of the 9.14 m (30 ft) long moment slab to which this barrier sec- tion was attached at its midpoint to measure any acceleration or motion imparted to the moment slab during impact. Displacement and/or rotation of the barrier and wall pan- els were determined from high-speed film operating at 1,000 frames/second. Displacement gages were placed at the top and bottom of the precast barrier–coping section and on the wall panels at heights corresponding to the three layers of soil rein- forcement. The location of the strain gages and other instru- mentation are shown in side view in Figure 6.22. The location of the strain gages on the steel reinforcement strips is shown in plan view in Figure 6.23. Detailed drawings of the test instal- lation and photographs of the construction procedure are pre- sented in Appendix E and F, respectively, which are available from the NCHRP Report 663 summary web page on the TRB website (www.trb.org) by searching for “NCHRP Report 663”. 6.3.2 Impact Conditions The MASH (10) test guidelines were applied for the TL-3 crash test. MASH test designation 3-11 (10) involves a 2270P vehicle weighing 2,270 kg ± 50 kg (5,000 lb ± 100 lb) and hitting the bridge rail at an impact speed of 100 km/h ± 4 km/h (62.2 mph ± 2 mph) and an angle of 25 degrees ± 1.5 degrees. The target impact point was 1.2 m (4 ft) upstream of the fourth barrier joint. The 2004 Dodge Ram 1500 quad-cab pickup truck used in the test weighed 2,246 kg (4,951 lb), and the actual impact speed and angle were 101.7 km/h (63.2 mph) and 25.6 degrees, respectively. The actual impact point was 1.3 m (4.3 ft) upstream of the fourth barrier joint. 6.3.3 Test Vehicle A 2004 Dodge Ram 1500 quad-cab pickup truck, shown in Figures 6.26 and 6.27, was used for the crash test. Test inertia weight of the vehicle was 2,246 kg (4,951 lb). The height to the lower edge of the vehicle front bumper was 349 mm (13.75 in.), and the height to the upper edge of the front bumper was 660 mm (26.0 in.). The vehicle was directed into the installa- tion using the cable reverse tow and guidance system and was released to be free-wheeling and unrestrained just prior to impact. Detailed test vehicle properties and information are presented in Appendix G, which is available from the NCHRP Report 663 summary web page on the TRB website (www.trb.org) by searching for “NCHRP Report 663”. 6.3.4 Test Description The 2270P vehicle, traveling at an impact speed of 101.7 km/h (63.2 mph), hit the MSE wall 1.31 m (4.3 ft) upstream of the fourth barrier joint at an impact angle of 25.6 degrees. At approximately 0.027 sec after impact, the vehicle began to redirect, and at 0.092 sec, the right front tire began to ride up the barrier face. The right rear tire lost contact with the ground surface at 0.129 sec, and the right rear of the vehicle began to rise at 0.147 sec. At 0.166 sec, the vehicle was traveling paral- lel with the barrier at a speed of 92.4 km/h (57.4 mph). The rear of the vehicle contacted the barrier at 0.186 sec, and the vehicle began to roll counterclockwise at 0.237 sec. At 0.338 sec, the vehicle lost contact with the barrier and was traveling at an exit speed and angle of 88.8 km/h (54.9 mph) and 7.9 degrees, respectively. As the vehicle continued forward, the vehicle 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.01 0.10 1.00 10.00 Pe rc en t p as si ng (% ) Grain size (mm) Figure 6.25. Particle size distribution curve of the backfill for TL-3 crash test.

137 Figure 6.27. Vehicle before test. B4 B3 B5 Figure 6.26. Vehicle/installation geometrics.

138 yawed clockwise and came to rest 53.34 m (175 ft) downstream of impact and 1.83 m (6 ft) forward of the traffic face of the barrier. Sequential photographs of the test period are shown in Appendix H, which is available from the NCHRP Report 663 summary web page on the TRB website (www.trb.org) by searching for “NCHRP Report 663”. 6.3.5 Test Article and Vehicle Damage Damage to the barrier was mostly cosmetic, as shown in Fig- ures 6.28 and 6.29. In the soil forward of the face of the barrier, there were two cracks. The first was a 4 mm (0.16 in.) crack 1,321 mm (52 in.) forward of the traffic face of the barrier that started at the joint between barrier B2 and B3 and ended at the joint between barrier B5 and B6. The second was a 2 mm (0.08 in.) crack 1,372 to 1,727 mm (54 to 68 in.) forward of the traf- fic face of the barrier, starting 6 m (2 ft) upstream of the joint between barrier B0 and B1 and ending 0.6 m (2 ft) downstream of the joint between barrier B2 and B3. Length of contact of the vehicle with the barrier was 4.1 m (13.6 ft). No measurable deflection of the barrier occurred. The 2270P vehicle sustained damage to the front left and left side, as shown in Figure 6.30. The left upper A-arm, left outer tie rod end, left frame rail, and rear axle were deformed and the left upper ball joint broke. Also damaged were the Crack in soil B3 B4 Figure 6.29. Installation after test. Figure 6.30. Vehicle after test. B4 B3 Figure 6.28. Vehicle trajectory path after test.

139 front bumper, hood, grill, radiator and support, fan, left front fender, left front and rear doors, left and right exterior bed, rear bumper, and tailgate. The windshield sustained stress cracks at the left lower corner, which radiated upward toward the roof and center. Maximum exterior crush to the vehicle was 0.4 m (15.75 in.) in the left side plane at the left front cor- ner at bumper height. Maximum occupant compartment deformation was 54 mm (2.1 in.) laterally across the cab at hip height in the instrument panel area. Photographs of the interior of the vehicle are shown in Figure 6.31. 6.3.6 Occupant Risk Data from the accelerometer, located at the vehicle center of gravity, were digitized for evaluation of occupant risk and were computed as follows. In the longitudinal direction, the occu- pant impact velocity was 12.8 ft/s (3.9 m/s) at 0.088 sec, the highest 10 msec occupant ridedown acceleration was −4.4 g from 0.088 to 0.098 sec, and the maximum 50 msec average acceleration was −6.5 g between 0.009 and 0.059 sec. In the lateral direction, the occupant impact velocity was 29.2 ft/s (8.9 m/s) at 0.088 sec, the highest 10 msec occupant ridedown acceleration was 9.2 g from 0.199 to 0.209 sec, and the maxi- mum 50 msec average was 15.7 g between 0.037 and 0.087 sec. Theoretical head impact velocity (THIV) was 34.6 km/h or 9.6 m/s at 0.087 sec, and post-impact head deceleration (PHD) was 9.3 g between 0.199 and 0.209 sec. These data and other pertinent information from the test are summarized in Figure 6.32. 6.3.7 Data from Accelerometers To estimate the impact force from the vehicle accelerometer data, Equation 6-1 was used. Before Test After Test Figure 6.31. Interior of vehicle for test.

140 where Fi(t) = the impact force φ(t) = the vehicular yaw angle Fx(t) = ma→x(t) = the longitudinal component of truck impact force Fy(t) = ma→y (t) = the horizontal component of truck impact force m = the mass of truck The coordinate systems for the truck and barrier are schema- tically shown in Figure 6.33. Equation 6-1 assumes the vehi- cle as a single rigid body for the purpose of calculating the impact force. Data obtained from the truck-mounted accelerometer were analyzed, and the results are presented in Figure 6.34. As shown in Figure 6.34(a) and (b), the maximum 50 msec average longitudinal and lateral accelerations were −6.5 g and 15.7 g, respectively. The change in yaw angle with respect to time is shown in Figure 6.34(c). Using Equation F t F t t F t t m a t i x y x ( ) = ( ) ( )− ( ) ( ) = ( ) sin cos si φ φ  n cos ( )φ φt a t ty( )− ( ) ( )( ) 6 1- 6-1, the acceleration–time histories shown in Figures 6.34(a) and (b), and the yaw angle–time history, the resultant impact force was computed as a function of time as shown in Fig- ure 6.34(d). The maximum 50 msec average resultant impact force was calculated to be 371.3 kN (83.5 kips) at a time of 0.062 sec. The maximum 50 msec average acceleration of the barrier, as measured by the accelerometer at the top of the barrier, is shown in Figure 6.35(a). The barrier acceleration oscillated in 0.000 s 0.086 s 0.171 s 0.340 s General Information Test Agency............................. Texas Transportation Institute Test No. .................................. 475350-1 Date......................................... 2008-09-25 Test Article Type......................................... 32 in. Vertical Barrier (T-221) Name....................................... MSE Wall Installation Length................... 90 ft Material or Key Elements........ Soil Type and Condition........... TxDOT Type B Backfill, Dry Test Vehicle Type/Designation..................... 2270P Make and Model...................... 2004 Dodge Ram 1500 Quad-Cab Curb......................................... 4794 lb Test Inertial.............................. 4951 lb Dummy.................................... No. Dummy Gross Static............................. 4951 lb Impact Conditions Speed......................................63.2 mi/h Angle.......................................25.6 degrees Location/Orientation................4.3 ft upstream Exit Conditions Speed......................................54.9 mi/h Angle.......................................7.9 degrees Occupant Risk Values Impact Velocity Longitudinal.........................12.8 ft/s Lateral..................................29.2 ft/s Ridedown Accelerations Longitudinal.........................–4.4g Lateral................................. 9.2 g THIV........................................34.6 km/h PHD........................................9.3g Max. 0.050 s Average Longitudinal......................... –6.5 g Lateral.................................15.7g Vertical................................ –3.7 g of 4th joint Post-Impact Trajectory Stopping Distance.....................175 ft downstream Vehicle Stability Maximum Yaw Angle................. 42 degrees @ 1.04 sec Maximum Pitch Angle................–10 degrees @ 1.64 sec Maximum Roll Angle..................-39 degrees @ 0.58 sec Vehicle Snagging.......................No Vehicle Pocketing......................No Test Article Deflections Dynamic.....................................0.84 in. (top of barrier) Permanent.................................0.37 in. (bot. of barrier) Working Width...........................0 Vehicle Damage VDS...........................................11LFQ5 CDC...........................................11FLEW4 Max. Exterior Deformation.........15.75 inches Max. Occupant Compartment Deformation.........................2.1 inches CDI..........................................LF0000100 6 ft toward traffic Figure 6.32. Summary of results for MASH test 3-11 on the MSE wall. ax ay y' x' y x Barrier 4Barrier 3 Truck 25° Figure 6.33. Coordinate system for vehicle and barrier.

141 (a) Longitudinal deceleration (b) Lateral acceleration (c) Yaw angle with respect to the barrier (d) Impact force Figure 6.34. Acceleration, impact force, and yaw angle of truck.

142 (a) Acceleration (b) Velocity (c) Displacement Figure 6.35. Acceleration, velocity, and displacement of barrier.

143 the range of 1.5 to −1.5 g. Examination of the impact events helps explain the barrier acceleration–time history. The barrier initially accelerated toward the field side of the installation as a result of the initial impact. As the vehicle was redirecting, the barrier began to rebound and accelerate back toward the traf- fic side. The back slap impact of the rear of the vehicle once again resulted in an acceleration of the barrier toward the field side, followed by the barrier rebounding and accelerating back toward the traffic side. The velocity–time history of the barrier, as calculated by integration of the raw acceleration data, is shown in Figure 6.35(b). Some error in this time history is evident, given that the velocity did not return to zero at the end of the test. This error is magnified in the displacement–time his- tory obtained from integration of the velocity history. Fig- ure 6.35(c) presents displacement–time history from both double integration of the acceleration data and from analy- sis of the high-speed film, which is considered to be more accurate. The maximum 50 msec average acceleration of the moment slab is shown in Figure 6.36(a). The velocity–time and vertical displacement–time histories of the moment slab are shown in Figure 6.36(b) and (c), respectively. The velocity–time history and displacement–time histories were calculated by integration of the acceleration data. 6.3.8 Photographic Instrumentation Targets affixed to the displacement bars attached to the top and bottom of the barrier–coping section (see Figures 6.23 and 6.37) were used as reference points to determine angular and translational displacement of the barrier from analysis of high- speed video. Two distinct impacts are evident in the displace- ment data corresponding to the front and rear vehicle-barrier (a) Acceleration (b) Velocity (c) Displacement Figure 6.36. Acceleration, velocity, and displacement of moment slab.

contact. The dynamic displacement associated with the initial impact of the barrier was 21.3 mm (0.84 in.) at the top of the barrier and 14 mm (0.55 in.) at the bottom of the coping. After first impact, the barrier began to rebound. The subsequent rear impact (back slap) resulted in the dynamic displacements at the top of the barrier and bottom of the coping of 18.8 mm (0.74 in.) and 14 mm (0.55 in.), respectively. The permanent displacement of the barrier was 9.4 mm (0.37 in.) at the top of the barrier and 6.4 mm (0.25 in.) at the bottom of the coping. Figure 6.38 shows the displacement–time history of the barrier and panel. Three additional targets affixed to the displacement bars attached to the wall panel at locations corresponding to these layers of wall reinforcement were used to determine angular and translational displacement of the panel from analysis of high-speed film. From the film analysis, the maximum dynamic displacement of the panel was 10.7 mm (0.42 in.) at the upper- most layer of reinforcement. The permanent displacement of the panel was 6.1 mm (0.24 in.) at the upper reinforcement layer. Less than 0.5 in. movement was measured at the second and third reinforcement layers. 6.3.9 Load on the Strip from Strain Gages A total of seven wall-reinforcement strips were instru- mented with two strain gages (top and bottom) to capture the tensile forces transmitted into the reinforcement during vehicle impact. To enable comparison of forces and displace- ments, barriers and selected strip locations have been assigned alphanumeric designators that describe their horizontal posi- tion and vertical reinforcement layer. For example, strip B4-F-1st is positioned beneath the downstream end of the fourth barrier in the first (i.e., upper) layer of reinforcement as shown in Figure 6.39. Raw data obtained from the strain gages on the strips were analyzed, and the results are presented in Figure 6.40. The 50 msec average of the raw data was analyzed to obtain design loads for the strips, and the results are presented in Figure 6.41. A summary of the maximum dynamic loads measured in the strips is shown in Table 6.3. The static load in the strips was measured during the con- struction to allow computation of the total load in the strips during impact. The average static load in the uppermost layer of reinforcement was 3.34 kN (0.75 kips) and the average 144 Figure 6.37. Location of displacement bars affixed on the barrier and panels. Time (sec) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 H or iz .D is pl ac em en t o f B ar rie r a nd P an el (in .) -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 Top of Barrier Bottom of Coping Top Layer of Strip 2nd Layer of Strip 3rd Layer of Strip Figure 6.38. Horizontal displacement of barrier and panel (Film). TL-3 B5 B4 B3 F E D C B A F E D C B A F E D C B A Figure 6.39. Location indicators for strain gages on the strips.

145 Table 6.3. Dynamic loads on the wall reinforcement. Top Layer (kips) B5-B-1st B4-E-1st B4-B-1st B3-F-1st Maximum load from raw data 2.15 2.37 2.10 2.32 Maximum 50 msec avg. load 2.08 2.21 1.94 2.20 Second Layer (kips) B4-E-2nd B4-B-2nd B3-F-2nd Maximum load from raw data 0.16 0.83 0.15 Maximum 50 msec avg. load 0.09 0.66 0.06 Table 6.4. Static loads on the wall reinforcement. Static Load Measured (kips) Static Load by AASHTO (kips) Top Layer 0.75 0.688 Second Layer 1.85 1.205 Table 6.5. Total loads on the wall reinforcement. Static Load Measured Dynamic Load* Measured Total Loads (kips) Resistance By AASHTO** (kips) (kips) (kips) Top Layer 0.75 2.20 2.95 2.052 Second Layer 1.85 0.66 2.51 3.413 * Maximum 50 msec average load from the four tests. ** AASHTO LRFD Equation 11.10.6.3.2-1 static load in the second layer of reinforcement was 8.23 kN (1.85 kips). A comparison of the measured static loads with those calculated by AASHTO LRFD is shown in Table 6.4. Table 6.5 shows the total measured load (measured static load + measured dynamic load) in the reinforcement strips in Figure 6.40. Dynamic load on the strips (raw data). Figure 6.41. Dynamic load on the strips (50 msec avg.). comparison to the calculated resistance of the strips using the AASHTO LRFD Equation 11.10.6.3.2-1. The pullout resis- tance of the strip was calculated to be 6.623 kN (1.489 kips) at the uppermost layer of strips and 11.821 kN (2.658 kips) at the second layer.

146 TL-3 B5 B4 B3 2 6 7 13 12 11 1 7 5 8 8 9 1 3 1 5 3 4 -2 3 1 4 5 3 1 2 1 1 3 0 -1 2 4 2 1 4 1 1 2 1 0 1 1 1 1 0 2 0 Figure 6.43. Permanent deflection of barrier and panels (units: mm). 6.3.10 Panel Analysis The wall panel was instrumented with three strain gages to capture the strains in the panel at points corresponding to the three layers of wall reinforcement. Figure 6.42 shows the 50 msec average strain–time history of the panel at each rein- forcement layer. The maximum strain in the panel occurred at a point corresponding to the upper layer of reinforcement and had a magnitude of 55.3 micro strain. 6.3.11 Other Instrumentations String lines located 1.08 m (3.54 ft) from the face of wall panels were used to measure the permanent deflection of the barriers and panels after vehicle impact at different elevations. After vehicle impact, the permanent deflection ranged from 13 mm (0.51 in.) at the top of barrier segment B4 to 1 mm (0.04 in.) at the bottom of the coping on barrier segment B5 as shown in Figure 6.43. The maximum residual dis- placement occurred at the joint of barrier segment B3 and B4. The permanent deflection obtained from the film analysis, which tracked targets affixed to the barrier–coping section, was 9.4 mm (0.37 in.) at the top of the barrier and 6.4 mm (0.25 in.) at the bottom of the coping. Note that the location of the target is the centerline of the panel (B5-H6). The permanent defection of the wall panels ranged from 5 mm (0.20 in.) to 1 mm (0.04 in.) as shown in Figure 6.43. Note that negative values indicate movement toward the traffic side of the barrier. Such movement may be the result of the panel being loaded eccentrically and rotating. The contact switch placed on the top edge of the level-up concrete on top of the wall panels inside the coping recess indicated that the coping did not contact the wall panel. 6.3.12 Damage of Moment Slab after Test After the crash test, the overburden soil was removed to per- mit inspection of the moment slab and the connection between the coping and moment slab. Thin cracks were found on top of the moment slab between Barrier 3 and 4 as shown in Figure 6.44. 6.4 Conclusions The roadside barrier mounted on the edge of the MSE wall performed acceptably according to the evaluation cri- teria specified for MASH test designation 3-11, as shown in Table 6.6. The roadside barrier on the MSE wall contained and redirected the 2270P vehicle. The vehicle did not penetrate, underride, or override the installation. No lateral move- ment of the barrier was noted. No detached elements, frag- ments, or other debris was present to penetrate or show potential for penetrating the occupant compartment, or to present hazard to others in the area. Maximum occupant compartment deformation was 53.3 mm (2.1 in.) in the lat- eral area across the cab. The 2270P vehicle remained upright during and after the collision event. Maximum roll was 39 degrees. Occupant risk factors were within the limits specified in MASH. -60 -50 -40 -30 -20 -10 0 10 20 30 0 0.1 0.2 0.3 0.4 0.5 0.6 Time (sec) St ra in (m icr o s tr ai n) Top Layer of Strip (50ms) Second Layer of Strip (50ms) Third Layer of Strip (50ms) 57.8 kips Figure 6.42. Strain on the panel.

147 6.5 Comparison of Test and Simulation A comparison between the results of the TL-3 test and the numerical simulations was conducted to establish confi- dence in the simulation for use in the guideline development process. Because the numerical simulation was modeled prior to performing the TL-3 test, the differences between the TL-3 test and simulation are listed below. These items may explain some of differences observed between test and numerical simulation. 1. While a 27.43 m (90 ft) long MSE wall was constructed for the test, an 18.28 m (60 ft) long MSE wall was modeled to reduce computational costs of the simulation. 2. While the wall was two full panels high [3.05 m (10 ft)] in the simulation, the test used a wall that was one and half panels high [2.29 m (7.5 ft)], as shown in Figure 6.45. How- ever, the simulation results indicate that the load in the fourth layer of strips was negligible. 3. The simulation model had a density of three strips per layer per panel in the first layer and two strips per layer per panel in the other layers. In the test, all layers of reinforce- ment had a density of three strips per layer per panel. 4. The panel orientation at the location of impact (see circle in Figure 6.45) was different in simulation and test. How- ever, this should not affect the loads in the strips. 5. The C2500 pickup truck model (reflective of NCHRP Report 350) used in the simulation has different character- istics than the 2270P truck (reflective of MASH) used in the TL-3 test as shown in Figure 6.46. 6. The coping detail of the barrier differed between model and test installation, as shown in Figure 6.47. Although field practice varies, the 254 mm (10 in.) coping depth and 101.6 mm (4 in.) high leveling pad used in the sim- ulation is considered to be a typical detail. However, because the test barrier sections were cast using forms developed for a concrete pavement application, the depth of the recess had to be adjusted for the asphalt concrete application to provide the necessary strength in the cop- ing section. Sequential images from the simulation and TL-3 test are shown in Figure 6.48. The correlation is considered reason- able given the difference in pickup-truck body styles. In addi- tion, the maximum 50 msec average impact loads from the accelerometer data on the truck were 439 kN (98.7 kips) in the simulation and 371.3 kN (83.5 kips) in the TL-3 test, as shown in Figure 6.49. The vehicle–barrier contact definition was used to measure the impact force on the barrier as shown in Figure 6.49. The maximum 50 msec average impact force from the contact definition was 248.21 kN (55.8 kips). The displacement of barrier is shown in Figure 6.50. The simula- tion overpredicts the displacement at the top of the barrier. The strip load in the simulation includes the static load due to earth pressure and the dynamic load due to the barrier impact. Therefore, the measured average static load in the reinforcement (Table 6.4) was subtracted from the simulated strip load to provide a simulated dynamic impact load to the measured dynamic impact load (Table 6.7). The simulation overpredicted the maximum strip load in the upper layer of reinforcement but captured the trends in the load–time history of the strip [Figure 6.51(a)]. The simulation underpredicted the maximum strip load in the second layer of reinforcement but captured the trends in the load–time history of the strip [Figure 6.51(b)]. The strain on the wall panel was evaluated as shown in Figure 6.52. The maximum compressive strain was about 60 micro strain at 0.08 sec in the test and about 18 micro strain at 0.065 sec in the simulation. In the simulation, the impact occurred above a half panel rather than a full- height panel, so the estimated panel strain was smaller than in the test. As can be seen in the comparison, the simulation is close to the results of TL-3 test. This simulation and test were evalu- ated to support the verification of design guidelines. B4 B3 B4B3 Figure 6.44. Cracks on the moment slab after test.

148 (a) Simulation (b) TL-3 Test 0.5" Gap TYP. 10' Barrier TYP. D3 A6 B3 H6 D3 A6 B3 H6 D3 A6 B3 H6 D3 A6 B3 H6 D3 A6 B3 H6 D3 A6 B3 H6 D3 A6 B3 H6 D3 A6 B3 H6 D3 A6 B3 H6 TL-3 32" 9'-1 3/4" 24" Figure 6.45. Difference of wall panel details. Table 6.6. Performance evaluation summary for MASH Test 3-11 on the MSE wall. Test Agency: Texas Transportation Institute Test No.: 475350-1 Test Date: 2008-09-25 MASH Evaluation Criteria Test Results Assessment Structural Adequacy A. Test article should contain and redirect the vehicle or bring the vehicle to a controlled stop; the vehicle should not penetrate, underride, or override the installation although controlled lateral deflection of the test article is acceptable. The roadside barrier on the MSE wall contained and redirected the 2270P vehicle. The vehicle did not penetrate, underride, or override the installation. No lateral movement of the barrier was noted. Pass Occupant Risk Detached elements, fragments, or other debris from the test article should not penetrate or show potential for penetrating the occupant compartment, or present an undue hazard to other traffic, pedestrians, or personnel in a work zone. No detached elements, fragments, or other debris was present to penetrate or show potential for penetrating the occupant compartment, or to present hazard to others in the area. Pass D. Deformations of, or intrusions into, the occupant compartment should not exceed limits set forth in Section 5.3 and Appendix E of MASH. Maximum occupant compartment deformation was 2.1 in. in the lateral area across the cab. Pass F. The vehicle should remain upright during and after collision. The maximum roll and pitch angles are not to exceed 75 degrees. The 2270P vehicle remained upright during and after the collision event. Maximum roll was 39 degrees. Pass H. Longitudinal and lateral occupant impact velocities should fall below the preferred value of 9.1 m/s (30 ft/s), or at least below the maximum allowable value of 12.2 m/s (40 ft/s). Longitudinal occupant impact velocity was 12.8 ft/s, and lateral occupant impact velocity was 29.2 ft/s. Pass I. Longitudinal and lateral occupant ridedown accelerations should fall below the preferred value of 15.0 g, or at least below the maximum allowable value of 20.49 g. Longitudinal ridedown acceleration was –4.4 g, and lateral ridedown acceleration was 9.2 g. Pass Vehicle Trajectory For redirective devices, the vehicle shall exit the barrier within the exit box. The 2270P vehicle did not cross the exit box.

149 (a) Simulation (b) TL-3 Test Figure 6.47. Difference of barrier details. Figure 6.46. Comparison of truck of (a) simulation and (b) TL-3 test.

150 (a) 0 sec (b) 0.085 sec (c) 0.17 sec (d) 0.34 sec Figure 6.48. Comparison of sequential photos.

151 Figure 6.49. Inertia deceleration force and impact force on the barrier. 0 0.5 1 1.5 2 2.5 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 D isp la ce m en t ( in. ) Time (sec) Top of Barrier (Simulation) Bottom of Barrier (Simulation) Top of Barrier (Test) Bottom of Barrier (Test) Figure 6.50. Displacement of barrier. Layer Measured Static Load (kips) Measured Dynamic Load (kips) Simulated Dynamic Load (kips) Top 0.75 2.20 3.39 Second 1.85 0.66 –0.09 Table 6.7. Total loads on the wall reinforcement. (a) First layer of strip (b) Second layer of strip Figure 6.51. Comparison of 50 msec average data of dynamic load on the strip. -7.0E-05 -5.0E-05 -3.0E-05 -1.0E-05 1.0E-05 3.0E-05 0 0.05 0.1 0.15 0.2 0.25 Time (sec) St ra in (in ./in .) TL-3 Test Simulation Figure 6.52. Comparison of panel strain at B4-A1.