Safety Analysis of Concrete Barriers Shielding Roadside Obstacles from Impact Simulation Test

In order to select the barrier level for roadside safety design, models of single unit truck collisions with Level 3 to Level 6 concrete barriers were established by adopting explicit finite element software LS-DYNA 3D; the impact speed was between $40\mathrm{km}/\mathrm{h}$ and $80\mathrm{km}/\mathrm{h}$. A finite element model of a modified vehicle verified by full-scale impact test to improve credibility of the simulation model was used. The relations between impact speed, level of concrete barriers, and the amount of vehicle overhang beyond the barrier was studied, the effectiveness of concrete barriers shielding roadside obstacles was quantitatively evaluated, and the minimum safe distance from the traffic side of barriers to roadside obstacles was obtained. The relationship between the Chinese specification method and the 50 ms mean lateral impact force in the calculation of barrier impact force is compared. The equation of important roadside obstacle impact force was developed and evaluated, and the design value of important roadside obstacle impact force is revised. The results indicate that when the barrier level is Level 3 to 6 and the design speed is $60\mathrm{km}/\mathrm{h}$ for roads, the minimum safe distance between barriers and roadside obstacles is 1.8 m to 1.2 m, and for roads with the design speed of $80\mathrm{km}/\mathrm{h}$, the minimum safety distance between barriers and roadside obstacles is 3.0 m to 1.7 m. The single unit truck VI_n of enhanced barrier is at least 5% lower than the F-shape barrier. The enhanced barrier contains and redirects the single unit truck in a more stable manner. The 50 ms mean lateral impact force between the cargo and the barrier is close to the Chinese specification method. Under the same impact conditions, a higher level of barrier lowers VI_n significantly, however, the impact force of the barrier increases greatly since the cargo is more likely to collide with barrier.