Three-Dimensional Load Transfer of Colorado Type 7 and Type 10 Rails on Independent Moment Slab Under High Test Level Impact Load;Final rept

摘要

The AASHTO LRFD Bridge Specifications changed the rail impact load requirement ranging from TL1 to TL6 with progressively increasing loads to accommodate heavier vehicles traveling at higher speeds to assure the safety of all traveling motorists and reduce maintenance time. Safety rails are usually top-mounted on retaining walls with independent moment slab and crashing vehicles can severely damage the retaining walls. Besides the safety concerns, the 2000 specs intend to mitigate the severe damage to rails and walls to facilitate cost-effective and speedy repair or reset. In the United States, over two million walls are MSE wall with modulus block facings, which are weaker than the reinforced concrete wall facings in hybrid walls. The Federal Highway Administration recommended the implementation of the 2000 Specs. The AASHTO Specs provide no design details or guidelines, but recommend the use of finite element analysis as a design tool. The consensus from the survey of all state DOT's indicates that the inertia resistance of rail-slab-wall systems should be included as resistance to the rail movement under high impact loads. Finite element analyses were performed to assess the need for design guidelines revisions to address the need for the high impact loads resistance enhancement. This study uses the three-dimensional nonlinear finite ele ment program, NIKE-3D, to assess the performance of Colorado Type 7 and Type 10 rails under different impact loads. Results show that the 200-ft length is the minimum length requirement and the rail end (or edge) needs strong foundation support.