Background
MassHighways is re-designing the bridge railing for the Annisquam River Bridge in Gloucester, Massachusetts (i.e., Bridge No. G-05-017). MassHighways would like to use the Minnesota Combination Bridge Railing Number Three. The new proposed bridge cross-section is shown in Attachment A to this proposal. The Minnesota combination bridge railing type three was successfully tested by Midwest Roadside Safety Facility (MwRSF)at the University of Nebraska for NCHRP Report 350 Test Level 4 conditions in 1996. This system is included in a list of FHWA accepted bridge railings in a memorandum dated May 30, 1997.
MassHighways would like to reconfigure the rail slightly to conform to the particular design requirements of the Annisquam River Bridge. For historic and aesthetic reasons, MassHighways would like to use a 32-inch tall railing rather than the crash tested 36-inch tall railing. In addition, a Test Level 3 system was deemed to be adequate for this site whereas the crash tested version of the Minnesota Combination Bridge Railing Number 3 exceeds the design requirements since it is a Test Level 4 system. Changes anticipated include lowering the rail height to 32", making the traffic face of the railing vertical, changing the curb from 20" to 17" and eliminating the grout pad for the steel post base plate.
Project
The MassHighways Division of Bridges and Structures asked WPI to evaluate the new bridge railing design using LS-DYNA finite element simulation to determine if the new configuration satisfies Report 350 Test Level 3 conditions.
A FE model of the crash tested Minnesota version of the bridge railing was built, based on the test documentation. This was necessary to demonstrate that the FE model produced correct results with respect to the crash tested results. This step was particularly important since MassHighways wanted to avoid performing full-scale crash tests, so it was essential to establish confidence with FHWA by showing the FE simulation replicates the results of the existing tests.
The next step was to take the validated model of the Minnesota configuration and change it such that it represented the cross-section desired for the Annisquam River Bridge. The FE model was then modified to correspond to the new design requirements. Simulations for both the small passenger car test and the full-size pickup truck test were then performed to determine the performance of the railing. The simulation results were evaluated according to NCHRP Report 350 in exactly the same way a physical full-scale crash test would have been evaluated. Evaluation parameters like the occupant risk, ride-down acceleration, etc. were determined with the standard post-processing program TRAP, the same program used to calculate evaluation parameters in full-scale crash tests
. For more details, please visit the project website at http://civil-ws2.wpi.edu/Documents/Roadsafe/A/
For further information, please contact:
Malcolm H. Ray, P.E., Ph.D.
Department of Civil and Environmental Engineering
Worcester Polytechnic Institute
Worcester, MA 01609-2280
508-831-5340 (voice)
508-831-5808 (fax)
mhray@wpi.edu
Updated 05-21-07 by mhr.
