Design Guidelines and Full-Scale Verification for MSE Walls with Traffic Barriers

Millions of square meters of mechanically stabilized earth (MSE) retaining walls are constructed annually in the United States. For highway applications, a roadside barrier system is placed at the edge of the wall. This barrier system generally consists of an $L$-shape concrete structure so that if a vehicle hits the vertical part of the $L$ shape (barrier), the horizontal part of the $L$ (moment slab) provides the resisting moment during the impact. This impact must be resisted by the soil, the reinforcement, and the panels in the MSE wall. This paper gives guidelines on how to design the reinforcement for pullout and yielding and the panels for flexural and shear failure. It also gives the guidelines on how to ensure the stability of the barrier. These design guidelines are developed in terms of AASHTO load and resistance factor design procedures. In a second part, a full-scale crash test on an instrumented 2.79 m high MSE wall is described and analyzed. The wall and barrier behaved very satisfactorily and represented a verification of the proposed guidelines. Pressure distributions are presented for designing the top two layers of wall reinforcement to resist barrier impact forces. A 44.5-kN static equivalent load is recommended for evaluating the stability of the barrier and moment slab system.