17 May 2024

A Dynamic Aircraft Response Model for Determining Roughness Limits

Abstract: Runway roughness poses significant risks to aircraft and aircraft personnel. Roughness irregularities can be found in both civilian and military airfields, from rutting to bomb-damaged repairs. Various methods exist for determining roughness criteria, such as discrete surface deviation evaluation and dynamic response models. Although validated dynamic response models such as TAXI-G were used extensively in the HAVE BOUNCE program from the 1970s up to the late 1990s, modern military aircraft have not undergone the same formal analysis. This paper presents the mathematical formulation and validation of the WESTAX dynamic response model. The computer program is capable of simulating the responses of different critical aircraft components while trafficking over idealized runway profiles. The validation results showed that the numerical model was capable of closely matching field data over single- and double bump events. The findings suggest that the WESTAX dynamic response model is a capable candidate for establishing aircraft roughness limits.

3 Oct 2023

Pattern Language for a More Resilient Future

Abstract: The Department of the Army (DA) manages millions of acres of land for military use. Military installations and other US DoD operations contain architectural structures and civil infrastructure that require continuous improvements to resiliency. This includes resiliency in the form of protection against both natural and man-made disasters. This document seeks to identify multiple risks to infrastructure and people and encourages open dialogue for creative solutions. Designers and engineers as well as other disciplines can work together to achieve higher resiliency in both new and renovated work. The following sections are created to provide a starting guide, utilizing various tools to discover the best resilient design strategies for your building. This special report will argue for actionable design strategies; drawing inspiration from historical building forms, while also looking toward emerging technologies that should be further explored.

5 May 2022

Waterborne Geophysical Investigation to Assess Condition of Grouted Foundation: Old River Control Complex – Low Sill Structure, Concordia Parish, Louisiana

Abstract: The Old River Low Sill Structure (ORLSS) at the Old River Control Complex (ORCC) in Concordia Parish, LA, is a steel pile-founded, gated reinforced-concrete structure that regulates the flow of water into the Atchafalaya River to prevent an avulsion between the Mississippi River and the Atchafalaya River. A scour hole that formed on the southeast wall of ORLSS during the Mississippi River flood of 1973 was remediated with riprap placement and varied mixtures of self-leveling, highly pumpable grout. Non-invasive waterborne geophysical surveys were used to evaluate the distribution and condition of the grout within the remediated scour area. Highly conductive areas were identified from the surveys that were interpreted to consist mostly of grout. Resistive responses, likely representing mostly riprap and/or sediment, were encountered near the remediated scour area periphery. A complex mixture of materials in the remediated scour area is interpreted by the more gradual transitions in the geophysical response. Survey measurements immediately beneath ORLSS were impeded by the abundance of steel along with the structure itself. The survey results and interpretation provide a better understanding of the subsurface properties of ORLSS.

31 Mar 2022

Continued Investigation of Thermal and Lidar Surveys of Building Infrastructure

ABSTRACT: We conducted a combined lidar and thermal infrared survey from both ground-based and Unmanned Aerial System (UAS) platforms at McMurdo Station, Antarctica, in February 2020 to assess the building thermal envelope and infrastructure of the Crary Lab and the wet utility corridor (utilidor). These high-accuracy, coregistered data produced a 3-D model with assigned temperature values for measured surfaces, useful in identifying thermal anomalies and areas for potential improvements and for assessing building and utilidor infrastructure by locating and quantifying areas settlement and structural anomalies. The ground-based survey of the Crary Lab was similar to previous work performed by the team at both Palmer (2015) and South Pole (2017) Stations. The UAS platform focused on approximately 10,500 linear-feet of utilidor throughout McMurdo Station. The datasets of the two survey areas overlapped, allowing us to combine them into a single, georeferenced 3-D model of McMurdo Station. Coincident exterior temperature and atmospheric measurements and Global Navigation Satellite System real-time kinematic surveys provided further insights. Finally, we assessed the thermal envelope of the Crary Lab and the structural features of the utilidor. The resulting dataset is available for analysis and quantification.

22 Nov 2021

Artificial Ground Freezing Using Solar-Powered Thermosyphons

Abstract: Thermosyphons are an artificial ground-freezing technique that has been used to stabilize permafrost since the 1960s. The largest engineered structure that uses thermosyphons to maintain frozen ground is the Trans Alaska Pipeline, and it has over 124,000 thermosyphons along its approximately 1300 km route. In passive mode, thermosyphons extract heat from the soil and transfer it to the environment when the air temperature is colder than the ground temperature. This passive technology can promote ground cooling during cold winter months. To address the growing need for maintaining frozen ground as air temperatures increase, we investigated a solar-powered refrigeration unit that could operate a thermosyphon (nonpassive) during temperatures above freezing. Our tests showed that energy generated from the solar array can operate the refrigeration unit and activate the hybrid thermosyphon to artificially cool the soil when air temperatures are above freezing. This technology can be used to expand the application of thermosyphon technology to freeze ground or maintain permafrost, particularly in locations with limited access to line power.