Iowa Department of Transportation
Iowa Highway Research Board
Alice Alipouralipour@iastate.edu email >
Structure and Infrastructure Engineer, BEC
Behrouz Shafeishafei@iastate.edu email >
Structural Engineer, BEC
About the research
This study investigated the differences between the American Railway Engineering and Maintenance-of-Way Association (AREMA), American Association of State Highway and Transportation Officials (AASHTO), and Iowa Department of Transportation (DOT) concerning vehicular collisions. The researchers evaluated the performance of common Iowa bridges and their components when an 80 kip tractor-semitrailer collides into them. The researchers also performed a parametric study on a frame pier and T-pier that experience vehicular collision.
The frame pier with two 3.5 ft column diameters with a spiral of #5 rebar and 4 in. pitch experiences minor damage when impacted by a tractor-semitrailer at an impact velocity of 50 mph. There is, however, severe damage and failure for the impact velocity of 70 mph and 90 mph, respectively. The T-pier commonly used in Iowa does not collapse under any of the three impact velocities. The minimum requirements for a crash wall specified by the Iowa DOT were able to keep the frame pier from failure when it was struck by a tractor-semitrailer traveling at each of the three impact velocities. The Iowa DOT’s 54 in. tall concrete barrier successfully redirects a tractor-semitrailer and therefore prevents it from hitting the frame pier it is set up to protect.
The frame pier with two column diameters of 4 ft with at least 1.0% longitudinal reinforcement, #5 spiral rebar at a 4 in. pitch, and Grade 60 steel, did not collapse under any of the three impact velocities. The T-pier with no ties experiences minor damage when impacted at the 50 mph impact velocity. However, ties spaced at 24 in. and 12 in. are required for minor damage at a 70 mph and 90 mph impact velocity, respectively.
The damage ratio index (DRI) values and damage description for the frame pier accurately predicted the damage observed in the frame pier due to vehicular collision. The DRI damage state description for the frame pier did not accurately describe the damage for the T-pier. Therefore, a DRI damage state description table was developed for the T-pier.