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From page 241...
... 241 9 DESIGN GUIDELINES FOR BARRIER-MOMENT SLAB SYSTEMS MOUNTED ON MSE WALLS FOR TL-3 THROUGH TL-5 IMPACTS The format presented in this section follows Chapter 7 of the NCHRP Report 663, "Design Guidelines" (2)
From page 242...
... 242 Rotation Point B Rotation Point A Overburden Soil Moment Slab Traffic Barrier C.G. Panels Finished Grade Figure 9-1 Rotation points for design of BMS system.
From page 243...
... 243 Equivalent Static Load, L hh Leveling Pad Overburden Soil BA W lA lB Moment Slab Traffic Barrier C.G. Panels s Finished Grade He FSRotationPoint A Rotation Point B Equivalent Static Load, L hh Leveling Pad Overburden Soil BA W lA lB Moment Slab Traffic Barrier C.G.
From page 244...
... 244 9.1 Guidelines for the Barrier The barrier, coping, and moment slab system should be designed for both strength and stability. The barrier should be designed in accordance with AASHTO LRFD to have an ultimate strength capable of resisting the dynamic impact load, Ld, recommended in this report and summarized in Table 9-1.
From page 245...
... 245 where W = weight of the monolithic section of barrier and moment slab plus any material laying on top of the moment slab (kips) φr = friction angle of the soil - moment slab interface The factored equivalent static load should be applied to the length of the moment slab between joints.
From page 246...
... 246 Leveling Pad Rotation Point A Overburden Soil Moment Slab Traffic Barrier C.G. Panels Finished Grade Rotation Point B Critical Section Leveling Pad Rotation Point A Overburden Soil Moment Slab Traffic Barrier C.G.
From page 247...
... 247 9.2 Guidelines for the Wall Reinforcement The wall reinforcement guidelines should ensure that the reinforcement does not pullout or break during a barrier impact with the chosen design vehicle. The connection between the reinforcement and the wall panel should be able to resist the pullout load or breaking load whichever controls.
From page 248...
... 248 Traffic Barrier C.G. h h Moment Slab Soil Top Layer of Reinforcement Second Layer of Reinforcement p dp-1 p dp-2 p s 1 2 Figure 9-4 Pressure distribution pdp for reinforcement pullout.
From page 249...
... 249 Figure 9-5 Default values for the pullout friction factor, F* (AASHTO LRFD Figure 11.10.6.3.2-1)
From page 250...
... 250 Table 9-3 Design line load Qdp for reinforcement pullout Test Designation Line Load (lb/ft) First Layer, Qdp-1 Second Layer, Qdp-2 TL-3(1)
From page 251...
... 251 The reinforcement resistance P for bar mats should be calculated as: P = F*
From page 252...
... 252 Traffic Barrier C.G. h h Moment Slab Soil Top Layer of Reinforcement Second Layer of Reinforcement p dy-1 p dy-2 p s 1 2 Figure 9-7 Pressure distribution pd for reinforcement yield.
From page 253...
... 253 due to the impact. The static load Fs should be obtained from the static earth pressure ps times the tributary area At of the reinforcement unit.
From page 254...
... 254 The reinforcement resistance R for strips or bar mats should be calculated as: t sR Aσ= (9-20) where σt= tensile strength of the reinforcement, and As= cross section area of the reinforcement.
From page 255...
... 255 2. Failure of the coping during impact: strength analysis is carried out as recommended by AASHTO.
From page 256...
... 256 2) Equivalent Static Load on the Barrier The equivalent static load on the barrier is the best estimate of the load that should be used in design to obtain a barrier moment slab system that satisfies the serviceability limit state.
From page 257...
... 257 9.3.3 Selection of Serviceability Limits The selection of serviceability limits was based on analysis of data from the crash tests and the FE impact simulations of different BMS systems for all test designations. This section describes the process of selecting an acceptable maximum dynamic and permanent movement for a BMS system at which the system is still considered serviceable.
From page 258...
... 258 Table 9-6 Summary of crash test barrier and simulation displacement results Test Level Description Moment Slab Length (ft) Moment Slab Width a (ft)
From page 259...
... 259 Figure 9-9 Locations of displacement measurements. Based on these results, it was decided to assign an allowable maximum dynamic displacement at the top of the barrier for each of the test levels.
From page 260...
... 260 Figure 9-10 Difference in dynamic displacements at the barrier top for the same angle of rotation. Figure 9-11 Barrier displacements at the top level of the adopted BMS systems for static load calculations.
From page 261...
... 261 The maximum permanent movement in the TL5-1 crash test barrier was 1.06 in.
From page 262...
... 262 Table 9-7 Selected moment slab system for static load calculations System Selected MSWa (ft) Tested MSWa (ft)
From page 263...
... 263 Figure 9-13 TL3 (3 in) Impact Load versus Time.
From page 264...
... 264 Figure 9-14 Maximum displacements at the top of the barrier versus time for TL-3 Impact Levels with moment slab widths 3.5, 4.0 and 4.5 ft. Figure 9-15 Maximum displacements at the coping level of the barrier versus time for TL3 Impact Levels with moment slab widths 3.5, 4.0 and 4.5.
From page 265...
... 265 Figure 9-16 TL-3 BMS system used in the calculation of resistance against sliding and overturning.
From page 266...
... 266 (311 kN) based on FE simulation using the MASH 2270P pickup truck model, the measured strip loads no longer require the interpolation of the measured values.
From page 267...
... 267 Table 9-8 Simulation results and calculation of TL-3 design strip load for pullout (1) Total Load (kips)
From page 268...
... 268 Table 9-9 TL-3 design pressure for yielding of soil reinforcement based on bogie test results Layer Total Design Load (kips) Static Load (kips)
From page 269...
... 269 1) Dynamic Load TL-4-1 The MASH TL-4-1 impact case relates to a barrier height of 36 in.
From page 270...
... 270 Figure 9-18 TL4-2 Impact Load versus Time for 42 in.
From page 271...
... 271 Figure 9-19 Maximum displacements at the top of the barrier versus time for TL-4-1 Impact Levels with moment slab widths 4.0, 4.5 and 5.2 ft. Figure 9-20 Maximum displacements at the coping level of the barrier versus time for TL4-1 Impact Levels with moment slab widths 4.0, 4.5 and 5.2 ft.
From page 272...
... 272 ft (1.37 m)
From page 273...
... 273 Figure 9-22 Maximum displacements at the coping level of the barrier versus time for TL4-1 and TL-4-2 Impact Levels with 4.5 ft moment slab width.
From page 274...
... 274 The 4.5-ft (1.37 m) wide moment slab was considered as the minimum required moment slab width for TL-4-1.
From page 275...
... 275 A 4.5-ft (1.37-m) wide moment slab was considered as the minimum width required for the moment slab for TL-4-2.
From page 276...
... 276 Table 9-10 Summary of the pullout resistance, maximum 50-msec. average strip load and wall displacement for MASH TL-4 impact simulation.
From page 277...
... 277 368.68 psf (17.65 kPa) for the first layer and 269.67 psf (12.91 kPa)
From page 278...
... 278 Table 9-12 Simulation results for TL-4 impact and calculation of design strip load for yielding design. Strip Length (ft)
From page 279...
... 279 Table 9-13 TL-4 design pressure for yielding of soil reinforcement based on simulation results. Layer Total Design Load (kips)
From page 280...
... 280 One of the recommendations made to preclude damage to the underlying MSE wall or significant relative displacement between barriers is that the length of the precast barrier section for TL-5-1 be at least 15 ft (4.57 m)
From page 281...
... 281 Figure 9-27 Maximum Displacements obtained at the coping level of a barrier of TL5-1 tested NJ Barrier and a straight barrier versus Time. The dynamic movements of the barrier system could not be obtained from the crash test due to a camera trigger malfunction.
From page 282...
... 282 Figure 9-28 BMS system used in the calculation of resistance against sliding and overturning.
From page 283...
... 283 Table 9-14 Summary of the pullout resistance, maximum 50-msec. average strip load and wall displacement for MASH TL-5-1 impact simulation.
From page 284...
... 284 Based on crash test data, the maximum measured load (50-msec. average)
From page 285...
... 285 To calculate the corresponding line load, the recommended pressures of 725 psf (34.71 kPa) for the first layer and the 400 psf (19.15 kPa)
From page 286...
... 286 For the 16 ft (4.88 m) long strips with a density of three strips per panel per layer, the tributary area was 2.47 ft2 (0.23 m2)
From page 287...
... 287 preferred failure mode of the barrier coping–moment slab system because it reduces the cost of repair after a severe impact. Figure 9-29 TL5-2 (48 in)
From page 288...
... 288 Figure 9-30 Maximum Displacements obtained at the top of a barrier of TL-5-2 tested straight barriers. Figure 9-31 Maximum Displacements obtained at the coping level of a barrier of TL-5-2 tested straight barriers.
From page 289...
... 289 Figure 9-32 TL-5-2 BMS system used in the calculation of resistance against sliding and overturning.
From page 290...
... 290 Table 9-19 Summary of the pullout resistance, maximum 50-msec. average strip load and wall displacement for MASH TL-5-2 impact simulation Strip Length/ Moment Slab Width (ft)
From page 291...
... 291 strip at the depth of the first layer (3.71 kips (16.50 kN)
From page 292...
... 292 To develop the design guideline against yielding of the reinforcement, the highest design load on any strip, computed from the full-scale impact simulations, was used; this was the load obtained in the simulation of the wall with 16 ft long strips and with the 12 ft (3.66 m) moment slab width.
From page 293...
... 293 Table 9-22 TL-5-2 design pressure for yielding of soil reinforcement Layer Total Design Load (kips) Static Design Load (kips)

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