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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294 10 AASHTO LRFD FORMAT DESIGN GUIDELINES SECTION 1 DESIGN GUIDELINES 1.1 SCOPE This section provides guidelines to design two MSE wall components: the BMS and the MSE wall reinforcement. The guidelines are applicable to test levels TL-3 through TL-5 criteria as defined in Section 13 of AASHTO LRFD Bridge Design Specifications, and for inextensible MSE wall reinforcement (e.g., strips, bar mats)
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295 1.2 DEFINITIONS Rotation Point A -- The rotation point of a BMS system if the top of the wall panel is isolated from contact with the coping by the presence of an air gap or a sufficiently compressible material as shown in Figure 1.1-1. Rotation Point B -- The rotation point of a BMS system if there is direct bearing between the bottom of the coping and the top of the wall panel or level-up concrete as shown in Figure 1.11.
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296 pdp-1 = dynamic pressure for pullout of the first layer of soil reinforcement (psf) pdy-1 = dynamic pressure for yielding of the first layer of soil reinforcement (psf)
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297 1.4 GUIDELINES FOR THE BARRIER 1.4.1 General The barrier, the coping, and the moment slab should be safe against structural failure. Any section along the coping and moment slab should not fail in bending or shear when the barrier is subjected to the design impact load.
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298 1.4.2 Sliding of the Barrier The factored static resistance (ɸP) to sliding of the BMS system along its base should satisfy the following condition (Figure 1.4.2-1)
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299 1.4.3 Overturning of the Barrier The factored static moment resistance (ɸM) of the BMS system to overturning should satisfy the following condition (Figure 1.4.4-1)
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300 1.4.4 Design of the Coping The critical section of the coping must be designed to resist the applicable impact load condition for the appropriate test level as defined in Table 1.4.4-1 (Figure 1.4.4-1)
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301 1.5 GUIDELINES FOR THE SOIL REINFORCEMENT 1.5.1 General The reinforcement guidelines aim to ensure that the reinforcement does not pullout or yield during the selected design impact event. C1.5.1 In this section, the recommendations for the load in the reinforcement due to the impact are based on a pressure diagram approach back calculated by using the design loads in excess of static earth pressure loads recorded in full-scale crash tests or FE impact simulations.
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302 1.5.2 Pullout of the Soil Reinforcement The factored ultimate static resistance (ɸP) to pullout of the reinforcement should satisfy the following condition: ɸP ≥ γs p s At+ γd pdp At (1.5.2-1)
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From page 303... ...
303 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 1.5.2-1 Pressure distribution pdp for reinforcement pullout.
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304 1.5.3 Yielding of the Soil Reinforcement The factored resistance (ɸR) to yielding of the reinforcement should satisfy the following condition: ɸR ≥ γs ps At + γd pdy At (1.5.3-1)
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305 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 1.5.3-1 Pressure diagram pdy for reinforcement yielding.
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