25 Jun 2020

PUBLICATION NOTICE: Improved Ribbon Bridge Structural Response Validation Testing

Abstract: vehicles and trucks up to Military Load Capacity 96. The Bridge Supplemental Set (BSS) includes Bridge Erection Boats and an anchorage system to allow for the positioning and securing of the bridge in moving water. Designed to function as either a floating bridge or a raft, the IRB and BSS give military commanders multiple options with regards to the tactical river crossings. The US Army Engineer Research and Development Center (ERDC) was contracted by Product Manager Bridging to provide a structural analysis via high-fidelity numerical modeling of various IRB spans and water flow rates. To this end, a finite element model (FEM) of the IRB was constructed using field measurements of IRB interior bays. To ensure accurate structural response characteristics of the FEM and to build confidence in the simulation results, a validation test series was devised to generate empirical data to correlate against. This report documents the IRB structural response validation testing conducted at ERDC in March 2018. The data contained in this report was used to validate the IRB structural FEM.

25 Jun 2020

PUBLICATION NOTICE: Structural Analysis of an Improved Ribbon Bridge Subjected to Hydrodynamic and Vehicular Loading

Abstract: Structural modeling and simulations were performed to determine limit states of an Improved Ribbon Bridge (IRB) subjected to hydraulic and vehicle loadings. Measurements of as-built IRB bays were used to construct a three-dimensional, computer-aided design model. The model was used to create a computational finite element model (FEM) that was validated through correlations of simulation results and empirical data. The validated FEM was used to establish limit states (i.e., maximum current and vehicular loading conditions for 110 and 210 m IRB crossings). Analyses revealed that the primary structural failure mode was yielding in the steel pins that link IRB bays. Assuming the IRB is adequately restrained at the shores, a 110 m IRB can withstand currents up to 11 ft/s with no vehicle traffic; a 210 m IRB can endure up to 7 ft/s under the same conditions. For risk crossings, one Military Load Classification-70 vehicle on the bridge, 110 and 210 m IRBs can tolerate currents up to 9 and 7 ft/s, respectively. Under normal crossing conditions vehicle spaced 100 ft apart, a 110 m IRB has the structural capacity to endure currents up to 9 ft/s; the maximum current for a 210 m IRB is 5 ft/s.

29 Apr 2020

PUBLICATION NOTICE: Improved Vehicle Mobility by Using Terrain Surfacing Systems

Abstract: Even for military vehicles designed with superior off-road capabilities, problematic soil conditions can impede mobility, particularly when many vehicles need to traverse the same path. Loose sands with little shear strength or wet silts or clays with little bearing capacity can deform rapidly under traffic. U.S. Army Engineer Research and Development Center researchers conducted field testing over several terrain conditions to measure performance of terrain surfacing systems designed to improve vehicle mobility. Soil conditions included poorly-graded sand, medium-strength silt, weak marsh, and two different slope conditions. Five different terrain surfacing, or matting systems, were tested that included four commercial variants and one U.S. government design. All testing took place at the ERDC Ground Vehicle Terrain Surfacing Test Facility in Vicksburg, Mississippi. Military test vehicles included a Marine Tactical Vehicle Replacement, Common Bridge Transporter, and M1 Abrams tank. Results from the testing showed that all matting systems provided notable improvement in the number of allowable vehicle passes over soft sands. Results varied for the different systems over weaker soils, with performance improved for those matting systems having thicker and stiffer panels. However, improved performance among matting systems came with a sacrifice of increased logistical burden. Data presented here-in include detailed site characteristics and soil deformation as a function of traffic.