Engineer Research And Development Center Research Articles

A Hybrid Expert System for Estimation of the Manufacturability of a Notional Design

The more “manufacturable” a product is, the “easier” it is to manufacture. For two different product designs targeting the same role, one may be more manufacturable than the other. Evaluating manufacturability requires experts in the processes of manufacturing, “manufacturing process engineers” (MPEs). Human experts are expensive to train and employ, while a well-designed expert system (ES) could be quicker, more reliable, and provide higher performance and superior accuracy. In this work, a group of MPEs (“Team A”) externalized a portion of their expertise into a rule-based expert system in cooperation with a group of ES knowledge engineers and developers. We produced a large ES with 113 total rules and 94 variables. The ES comprises a crisp ES which constructs a Fuzzy ES, thus producing a two-stage ES. Team A then used the ES and a derivation of it (the “MAKE A”) to conduct assessments of the manufacturability of several “notional” designs, providing a sanity check of the rule-base. A provisional assessment used a first draft of the rule-base, and MAKE A, and was of notional wing designs. The primary assessment, using an updated rule-base and MAKE A, was of notional rotor blade designs. We describe the process by which this ES was made and the assessments that were conducted and conclude with insights gained from constructing the ES. These insights can be summarized as follows: build a bridge between expert and user, move from general features to specific features, do not make the user do a lot of work, and only ask the user for objective observations. We add the product of our work to the growing library of tools and methodologies at the disposal of the U.S. Army Engineer Research and Development Center (ERDC). The primary findings of the present work are (1) an ES that satisfied the experts, according to their expressed performance expectations, and (2) the insights gained on how such a system might best be constructed.

Physics-Based Watercraft Simulator in Virtual Reality

In this paper, watercraft and ship simulation is summarized, and the way that it can be extended through realistic physics is explored. A hydrodynamic, data-driven, immersive watercraft simulation experience is also introduced, using the Unreal Engine to visualize a Landing Craft Utility (LCU) operation and interaction with near-shore waves in virtual reality (VR). The VR application provides navigation scientists with a better understanding of how coastal waves impact landing operations and channel design. FUNWAVE data generated on the supercomputing resources at the U.S. Army Corps of Engineers (USACE) Engineering Research and Development Center (ERDC) are employed, and using these data, a graphical representation of the domain is created, including the vessel model and a customizable VR bridge to control the vessel within the virtual environment. Several dimension reduction methods are being devised to ensure that the FUNWAVE data can inform the model but keep the application running in real time at an acceptable frame rate for the VR headset. By importing millions of data points output from the FUNWAVE version 3.4 software into Unreal Engine, virtual vessels can be affected by physics-driven data.

Structural infrasound from a barge collision with the Mississippi river bridge.

The Mississippi River Bridge in Vicksburg, Mississippi, is a seven-span cantilever bridge that is 1033 m long by 20.9 m wide and is part of the Interstate-20 corridor. On March 23, 2011, at approximately 14:30 CST, a barge moving downstream struck a pier of the bridge. An infrasound array located at the U.S. Army Engineer Research and Development Center (ERDC) detected the impact. Finite Element (FE) models were developed to investigate the structural behavior of the bridge due to the impact. The FE models identified events within the infrasound record that were possibly produced by the different modes of vibration of the bridge structure. The emerging technology of structural infrasound monitoring and the potential for using infrasound as a forensic tool is demonstrated with the results of the bridge-barge collision event and capability of deployment in the future.

Technology and Policy: System Acquisition in a Complex Operational Environment

The United States’ (US) ability to maintain a technological edge in the current operational environment is challenged by the increased ability of near-peer nations to produce military technology. In response to this problem, the US Army Engineer Research and Development Center (ERDC) seeks to model the three key elements of military system acquisition—context, product, and process—to develop a more comprehensive understanding regarding how and why nations acquire technical solutions. Through the application of the System Dynamics Modeling Process (SDMP), this research examines the interactions between the strategic context of Germany, the military products it acquires to address its operational needs, and the processes it employs to acquire military technology. The results of this research indicate that numerous dynamic variables of context impact the acquisitions process for Germany, particularly political support and subsequent monetary allocations to research and development.

Data Analytics Development from Military Operational Data

Each year, the National Training Center (NTC) located at Fort Irwin, California, hosts multiple Brigade-level rotational units to conduct training exercises. NTC’s Instrumentation Systems (NTC-IS) digitally capture and store characteristics of movement and maneuver, use of fires, and other tactical operations in a vast database. The Army’s Engineer Research and Development Center (ERDC) recently partnered with Training and Doctrine Command (TRADOC) to make some of the data available for introductory analysis within a relational database. While this data has the potential to expose capability gaps, uncover the truth behind doctrinal assumptions, and create a sophisticated feedback platform for Army leaders at all levels, it is largely unexplored and underutilized. The purpose of this project is to demonstrate the value of this data by developing a prototype information system that supports post-rotation analytics, playback capabilities, and repeatable workflows that measure and expose ground-truth operational and logistical behavior and performance during a rotation. The Army modeling and analysis community will use these products to systematically curate and archive the database and enable future analysis of the NTC-IS data.

Multifaceted Approach of Assessing Channel Design through Ship Simulations in Mobile Harbor, Alabama

Recently, Mobile Harbor, Alabama, experienced an increase in vessel size and traffic, which resulted in navigation inefficiencies. This prompted a navigation improvement study that included ship simulations to assess proposed modifications to the federal navigation channels. In 2017, the US Army Engineer Research and Development Center (ERDC) ship/tow simulator (STS) was used to complete a feasibility-level screening simulation (FLSS) study. Areas of focus included: a bend easing, a passing lane, and a turning basin. Over the course of 1 week, a variety of proposed designs were screened and subsequently revised. In 2020, the FLSS study databases were used as a foundation for a more robust study. Approximate meeting locations in the passing simulation track plots were differentiated to capture an instant in time. Additional analysis was performed to identify grounding factors in the passing lane. It was determined that the proposed modifications were feasible under certain restrictions. Through this two-pronged approach, a project deficiency was identified early in the process that allowed for revision and rigorous testing of a preassessed channel.

C-FLEX Advanced Finite Element Analysis Program for Flexible Pavement Analysis and Design

The U.S. Army Engineer Research and Development Center (ERDC) of the U.S. Army Corps of Engineers has initiated an effort to modernize the Department of Defense (DOD) pavement design and evaluation procedures initially developed in the 1950s. Flexible pavement analyses and evaluations are currently performed based on the elastic layered WESLEA and WESDEF software programs. To modernize the current pavement design and evaluation procedures used by the DOD, an advanced axisymmetric Finite Element Method (FEM) based analysis program, named C-FLEX, was developed and is introduced in this paper. The C-FLEX program is designed to feature accurate material models for all pavement layers with the capability to model the cross-anisotropic and nonlinear elastic properties of unbound base/subbase and subgrade layers, the viscoelastic behavior of the asphalt mixture, as well as mechanical reinforcement using geosynthetics in flexible pavements. The FEM formulation in C-FLEX and the program architecture and implementation details are introduced and discussed in this paper. The different analysis schemes and proper models used to characterize the cross-anisotropy and stress-dependent material nonlinearity are also described in detail. The viscoelastic analysis scheme and the geosynthetic characterization are currently under development and so are not included in this paper. Furthermore, two conventional flexible pavements with different layer properties are analyzed to verify the solutions and reliability of the C-FLEX program. Based on this development effort with ERDC, the C-FLEX program is envisioned to eventually serve as the flexible pavement analysis engine for the DOD’s new mechanistic design and evaluation platform.

A finite element analysis engineering solution to short riveted connections under dynamic loadings

The research presented in this manuscript focuses on the development of an LS-DYNA finite element model to predict the dynamic shear strength of short riveted lap-spliced specimens. Using data collected from experimental testing at the U.S. Army Engineer Research and Development Center (ERDC), a finite element model was developed to replicate the behavior of A502 Grade short riveted connections under quasi-static loading. Subsequent analyses used published Cowper-Symonds constitutive model coefficients to replicate the behavior of these connections under dynamic loading. Computed results were then compared with available test data from ERDC. Given the challenges involved in creating physical models with riveted connections and the abundance of historical bridges constructed with rivets, the developed finite element analysis engineering solution can serve as a critical tool for researchers interested in predicting the response of short riveted connections to dynamic loading and those interested in developing strategies to mitigate against this loading.

MODAL GRAIN SIZE EVOLUTION AS IT RELATES TO THE DREDGING AND PLACEMENT PROCESS - GALVESTON ISLAND, TEXAS

During the fall and winter of 2015, a beneficial-use of dredged material project taking material from the Galveston Entrance Channel and placing it on a severely eroded beach of Galveston Island was conducted. This material was estimated to have 38percent fines. This operation was conducted again in the fall of 2019 and monitored for estimation of the loss of fines, changes in compaction and color from the dredging source to the beach. The local community and state funded the incremental cost at approximately $8 a cubic yard in 2015, and $10.5 a cubic yard in 2019 to have this material pumped to the beach. The projects were closely monitored by the U.S. Army Corps of Engineers (USACE) Engineer Research and Development Center (ERDC) and the USACE Galveston District. The data from this placement project was used to calculate and better understand the loss of fines during the dredging and placement process as well as aid in the generation of an empirical formula to estimate the loss of fine sediments during dredging and beach placement. This formula takes into account: losses due to dredging equipment operations, slope of the effluent return channel at the beach, sediment settling velocity, and sorting parameter.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/VQ36upT2iQo

Review of wide-area geophysical urban infrastructure monitoring techniques

Geophysical techniques have the potential to comprehensively assess the urban landscape, including the human-built environment. The U.S. Army Engineer Research and Development Center (ERDC) has developed methods to persistently and remotely monitor critical infrastructure by using infrasound (subaudible acoustics below 20 Hz). Infrasound can propagate tens of kilometers or more depending on source characteristics and meteorological conditions. Large bridges, dams, and other industrial sources are considered critical infrastructure. They emit infrasound since they exhibit characteristics of modal motion in the infrasound passband. While the motion of these structures may not be perceptible to humans, instrumentation can detect small air-coupled movements, providing real-time information about infrastructure behavior and condition. Techniques originally developed by the nuclear monitoring community for detecting large impulsive events from permanently emplaced instrumentation located in quiet isolated locations had to be adapted to the complex and dynamic urban space. The infrasound arrays and associated processing schema developed by the ERDC do not need to be in close proximity to the structures, are omnidirectional, and are capable of assessing multiple structures simultaneously. They continually record structural information to provide real-time information to infrastructure owners. However, several unique challenges must be addressed to successfully accomplish no-contact, persistent, structural monitoring in cluttered and noisy urban areas. This article describes recommendations for urban-appropriate instrumentation deployment methods and elevated noise floor concerns based on three field experiments representing metropolitan (Dallas, Texas), suburban (San Diego, California), and industrial (Sutter County, California) areas.

Full-Scale Evaluation of Relatively Thin Airfield Pavements

A full-scale airfield pavement test section was constructed and trafficked by the U.S. Army Engineer Research and Development Center (ERDC) to evaluate the performance of relatively thin airfield pavement structures. The test section consisted of four test items that included three asphalt pavement thicknesses and two different aggregate base courses. The test items were subjected to simulated aircraft traffic to evaluate their response and performance to realistic aircraft loads. Rutting behavior, instrumentation response, and falling weight deflectometer response were monitored at selected traffic intervals. It was found that the performance of the airfield pavement sections were most sensitive to aggregate base course properties, where a 50% reduction in base course strength resulted in a 99% reduction in allowable passes. The data suggested that when sufficient asphalt thickness is not provided, the failure mechanism shifted from subgrade failure to base course failure, particularly at higher subgrade CBR values. In addition, the number of aircraft passes sustained was less than that predicted by current Department of Defense (DOD) methods that include assumptions of a high-quality aggregate base and a minimum asphalt concrete thickness. The results of this study were used to extend existing DOD pavement design and evaluation techniques to include the evaluation of airfield pavement sections that do not meet the current criteria for aggregate base quality and minimum asphalt concrete surface thickness. These performance data were used to develop a new base failure design curve using existing stress-based design criteria.

Analysis of Full-Scale Geosynthetic Reinforced Airfield Pavement Subjected to Accelerated Aircraft Loading

AbstractA full-scale airfield pavement section was constructed and trafficked by the US Army Engineer Research and Development Center (ERDC) to evaluate the performance of geogrid reinforced flexib...

Ballistic performance of Cross-laminated Timber (CLT)

Cross-laminated Timber (CLT) is a relatively new building material that has gained recent attention in the United States construction industry. CLT is a prefabricated, engineered wood product, composed of three or more plies of lumber with alternating ply directions. CLT is relatively strong and stiff, with the potential to meet the requirements for structures that are subjected to a variety of loading conditions. While CLT’s response to static, dynamic (i.e., seismic), and fire loads has been characterized in the past, its response to the loads seen in force protection scenarios (i.e., blast or ballistic) is much less understood.In order to begin to fill this gap in knowledge, one of the first known sets of ballistic experiments were conducted on CLT and the results were used to develop and validate predictive models. This article describes the results of 122 ballistic experiments conducted at the United States Army Engineer Research and Development Center (ERDC). The experiments were conducted on two species of CLT of varying thicknesses: Spruce Pine Fir-South and Southern Yellow Pine. The experiments measured either penetration depth or residual velocity over a range of intermediate striking velocities. The effects of weathering (i.e., moisture content) were also explored on a data set.The results of the experiments were compared to existing United States Unified Facilities Criteria models for predicting the ballistic response of wood. The findings show the deficiencies in utilizing this wood model for CLT and explore alternate models for prediction. In general, it was found that models that incorporate both projectile and CLT target parameters most accurately predict the response. Most importantly, the results reinforce the necessity for re-calibration of models as new parameters are added to the CLT ballistic characterization database.

Performance of multi-axial geogrid stabilised flexible pavements

Full-scale test sections were constructed and trafficked at the U.S. Army Engineer Research and Development Center (ERDC) to provide performance data for comparing the effectiveness of multi-axial geogrid stabilised flexible pavement sections with an unstabilised flexible pavement section. Two test sections containing differing multi-axial geogrids were constructed and trafficked under shelter in ERDC's hangar 2 pavement test facility. The test sections were subjected to accelerated traffic loading using a dual-wheel tandem-axle configuration simulating typical highway loadings. Permanent surface deformation, rutting, pavement stiffness and instrumentation response data were collected at designated traffic intervals. The results of the study indicate that the geogrid stabilised sections improved the performance of the pavement section when compared with the unstabilised section.

Compaction and Spall of UHPC Concrete Under Shock Conditions

Several dozen impact experiments were conducted utilizing gun-driven, parallel-plate impacts in several complimentary configurations to produce weak shock waves in an ultra-high performance concrete (UHPC) known as “cortuf.” This UPHC variant was developed and fabricated at the U.S. Army Engineer Research and Development Center (ERDC) in Vicksburg, MS with no fiber reinforcement or coarse aggregate. The Hugoniot of the material in the range of 0–21 GPa is reported, although at lower shock pressures the material is highly dispersive and does not transmit a shock, leading to some ambiguity when conveying the results in the construct of a shock. The results, when compared with similar studies on other concrete variants, suggest that Portland cement based concretes without fiber reinforcement display shock behavior below 3 GPa which is dependent on the formulation and curing, but above 3 GPa, most can be represented by the empirical shock relation US = 2.35 km/s + 1.66uP up to at least the maximum pressure investigated in this work (21 GPa). Furthermore, it is shown that of the three types of porosity present in most concrete, in the concrete examined, only the entrapped air acts as porosity that is compacted during the shock. This investigation shows that although different grades of concrete vary widely in quasi-static compressive and tensile strength, under dynamic shock loading (uniaxial strain), most have similar yield points that can be described as a Hugoniot elastic limit of ~ 0.5 GPa or a yield strength of 0.4 GPa. In cortuf, the dynamically determined compressive yield point agrees closely with the quasi-statically determined yield (in conditions of uniaxial strain), implying very little strain-rate strengthening in UHPC, but in low strength (conventional) concrete, the dynamically determined yield is much higher than the corresponding quasi-static yield point. Therefore, the yield point of concrete in high-rate uniaxial strain is found to be independent of unconfined yield strength, and limited to an upper bound of ~ 0.4 GPa (HEL = 0.5 GPa). Post-yield compaction is strain-rate dependent in cortuf as well as other formulations for which literature data is available. In uniaxial-strain tension, cortuf has a spall strength of ~ 50 MPa, in rough agreement with the limited spall data available elsewhere, and the work shows that the spall and tensile behavior of cortuf loosely follows trends recently proposed by others.

Formulation and application of the adaptive hydraulics three-dimensional shallow water and transport models

Next generation, conservative finite element hydrodynamic and transport models are vital for accurate and efficient ocean, estuary and river simulation. Numerical models such as these have been developed for decades by the U.S. Army Corps of Engineers at the Engineering Research and Development Center (ERDC). This paper focuses on recently developed implicit, multi-dimensional finite element 3D shallow water and transport models included in the Adaptive Hydraulics (AdH) numerical suite. These AdH 3D models benefit from their adaptive meshing capabilities to resolve sharp solution gradients, such as those often encountered with baroclinic wedges traveling up an estuary channel. This paper presents the AdH 3D mathematical formulation and solution procedure used to solve the weak finite element equations for these models, along with results for several common verification cases and an AdH Galveston Bay validation study. A novel Streamline Upwind Petrov–Galerkin (SUPG) method for 3D shallow water models is described which reduces to the AdH 2D shallow water SUPG formulation under certain conditions. Careful attention is placed on ensuring discrete consistency in the equation set.

Assessment of Equivalent Thickness Design Principles for Geosynthetic Reinforced Pavements by Way of Accelerated Testing

The Engineer Research and Development Center (ERDC) of the U.S. Army Corps of Engineers has performed multiple laboratory and full-scale evaluations of geosynthetic reinforced pavements. One result from early geosynthetic reinforced pavement evaluations was a pavement design methodology implemented in ETL 1110-1-189: Use of Geogrids in Pavement Construction. Since that time, the evaluations have been primarily focused on comparing performance between varying types of geosynthetic products. While the studies have independently compared the discrete performance of single geosynthetic reinforced sections to unreinforced sections, a comprehensive analysis of available data has not been performed to validate or refine the implemented design methodology. The objective of this effort was to assemble available data from laboratory and full-scale testing conducted at ERDC for the primary purpose of assessing the flexible pavement design methodology presented in ETL 1110-1-189. Simplifying assumptions were made to allow comparison of varying loading and pavement structure conditions. This assessment found that the combined dataset supports the original design curve produced with the equivalent thickness methodology described in ETL 1110-1-189. The updated dataset would reduce the equivalent reinforced thickness by approximately 1.0-inches (25.4 mm) at unreinforced thicknesses less than 14 inches (356 mm), providing a slightly more conservative result. The adjusted data converged with the original equivalency chart at an unreinforced thickness of approximately 16 inches (406 mm).

Seismic-infrasound-acoustic-meteorological sensors to dynamically monitor the natural frequencies of concrete dams

The U.S. Army Engineer Research and Development Center (ERDC) is leading research using seismic-infrasound-acoustic-meteorological (SIAM) arrays to determine structural characteristics of critical infrastructure. Large infrastructure, such as dams, emit infrasound (acoustic energy below that of human perception) at their natural modes of vibration, which are related to their structural condition. To validate the concept and its potential use for monitoring flood control structures, a structural evaluation was conducted at the Portuguese Dam in Ponce, Puerto Rico. The dam’s dynamic properties were studied prior to the deployment of SIAM arrays using detailed finite element (FE) models assembled in COMSOL Multiphysics software. The principal natural frequencies of the dam were identified and the fundamental modes were confirmed in the infrasound pass-band. The natural frequencies of 4.8 Hz, 6.7 Hz, and 10.2 Hz, respectively, were determined for the lower modes of vibrations. A total of three SIAM arrays wer...

Five-Hour Autoclave Test for Determining Potential Alkali-Silica Reactivity of Concrete Aggregates: A Multi-Laboratory Study

Abstract Alkali-silica reaction (ASR) is a deleterious chemical reaction that can lead to expansion and cracking of concrete structures. The reaction occurs between alkali hydroxides in the pore solution and reactive forms of silica present in some aggregates. To successfully mitigate ASR in new structures, the potential alkali reactivity of the aggregates must be known. Standardized test methods for this purpose are sometimes too time-consuming for rapid military construction operations. To assess the viability of a five-hour autoclaved mortar bar test method for ultra-rapid identification of aggregate reactivity, researchers in five laboratories participated in a multi-laboratory study led by the U.S. Army Engineer Research and Development Center (ERDC). The test method uses fine aggregate in mortar bars like those used in ASTM C1260, Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method), but the equivalent alkali content of the mortar is boosted to 3.5 % by mass of cement. Mortar bars are cured for 48 hours prior to autoclaving at 130°C for five hours at peak temperature. This paper details the test procedure, expansions, comparisons with the accelerated mortar bar test and the concrete prism test, within- and multi-laboratory precisions, and investigation into the amount of alkali leaching during the test. For 85 % of the 20 aggregates tested, there was agreement between the autoclave test and ASTM C1260 in determining whether or not an aggregate was reactive to some degree. The agreement between the autoclave test and ASTM C1293, Standard Test Method for Determination of Length Change of Concrete Due to Alkali-Silica Reaction, was 100 % for ten of the aggregates for which ASTM C1293 data were available. The average within- and multi-laboratory coefficients of variation were 5.9 and 20.0 %, respectively. Results showed alkali leaching to be between 6 and 9 % per mortar bar. This study demonstrated the viability of the five-hour autoclave test for rapidly assessing aggregate reactivity in military construction operations.

Infrasound from small explosions from near to intermediate ranges

An experiment was performed near the U.S. Army Engineer Research and Development Center (ERDC) site near Vicksburg MS on May 2014. Explosive charges were detonated and the shock and acoustic waves were detected with pressure gauges, infrasound sensors, and seismometers stationed at various distances from the source, from 3 m to 15 km. One objective of the experiment was to compare the effectiveness of different wind filter strategies. Toward this end, several sensors were deployed near each other, approximately 8 km from the site of the explosion. These sensors used different types of wind filters, including different length of porous hoses, a bag of rocks, a foam pillow, and no filter. Signal-to-noise estimates made from signals recorded with these different sensors will be used to evaluate the effectiveness of the different strategies. A second objective was to compare the infrasound and seismic signals recorded with collocated infrasound sensors and geophones. Results from this experiment will be presented. Permission to publish was granted by Director, Geotechnical & Structures Laboratory.