17 Dec 2024

Full-Scale Demonstration of the Modernized Bridge Supplemental Set

Abstract: The Overhead Cable System (OCS) serves as the main anchorage system of the Bridge Supplemental Set and is used to hold the Improved Ribbon Bridge (IRB) against river flow. Several improvements have been made to OCS components and employment procedures, theoretically allowing the OCS to operate safely within most environments. However, the modernized OCS had yet to be constructed over an actual river, making it necessary to conduct a full-scale capability demonstration. Range W2 of Camp Ripley was selected as the test site because the 200th Multi-Role Bridge Company agreed to support the demonstration during an ongoing training cycle. A site reconnaissance trip revealed environmental obstacles on each bank, which made the site a unique test for the modernized OCS. The OCS model, a software package developed to analyze the loading imposed by river drag force on the OCS, was used to design a unique layout that circumvents Camp Ripley’s environmental challenges. The OCS was successfully deployed over Camp Ripley’s wet gap flowing at a river speed of 3.5 ft/s, and the IRB supported vehicular traffic for 3 hr before safe disassembly. Several lessons were learned regarding system deployment, and data were collected to facilitate technical manual development.

13 Apr 2023

Advanced Cementitious Materials for Blast Protection

Abstract: Advanced cementitious materials, commonly referred to as ultra-high performance concretes (UHPCs), are developing rapidly and show promise for civil infrastructure and protective construction applications. Structures exposed to blasts experience strain rates on the order of 102 s-1 or more. While a great deal of research has been published on the durability and the static properties of UHPC, there is less information on its dynamic properties. The purpose of this report is to (1) compile existing dynamic property data—including compressive strength, tensile strength, elastic modulus, and energy absorption—for six proprietary and research UHPCs and (2) implement a single-degree-of-freedom (SDOF) model for axisymmetric UHPC panels under blast loading as a means of comparing the UHPCs. Although simplified, the model allows identification of key material properties and promising materials for physical testing. Model results indicate that tensile strength has the greatest effect on panel deflection, with unit weight and elastic modulus having a moderate effect. CEMTECmultiscale® deflected least in the simulation. Lafarge Ductal®, a commonly available UHPC in North America, performed in the middle of the five UHPCs considered.

22 Apr 2021

Estimating Bridge Reliability by Using Bayesian Networks

Abstract: As part of an inspection, bridge inspectors assign condition ratings to the main components of a bridge’s structural system and identify any defects that they observe. Condition ratings are necessarily somewhat subjective, as they are influenced by the experience of the inspectors. In the current work, procedures were developed for making inferences on the reliability of reinforced concrete girders with defects at both the cross section and the girder level. The Bayesian network (BN) tools constructed in this work use simple structural mechanics to model the capacity of girders. By using expert elicitation, defects observed during inspection are correlated with underlying deterioration mechanisms. By linking these deterioration mechanisms with reductions in mechanical properties, inferences on the reliability of a bridge can be made based on visual observation of defects. With more development, this BN tool can be used to compare conditions of bridges relative to one another and aid in the prioritization of repairs. However, an extensive survey of bridges affected by deterioration mechanisms is needed to confidently establish valid relationships between deterioration severity and mechanical properties.