Scholars Hangar (United States Air Force Academy)
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Influence of Slow-Moving Nature of Super Heavy Load (SHL) Vehicles on the Service Life of Pavement Structures
No full textConference Paper.Trucks transferring super heavy load (SHL) typically weigh several folds of the permissible weight limits set forth by regulatory agencies. Operation of such vehicles with heavy wheel loads and nonconventional axle arrangements can result in substantial loss of service life of transportation facilities. Such detrimental impacts are more significant, considering the slow-moving nature of SHLs and time-dependent behavior of viscoelastic asphalt layers. This was the motivation for our research team to develop a framework to quantify pavement life reduction (PLR) associated with the slow-moving nature of SHL vehicles. To achieve this objective, our research team initially deployed portable weight-in-motion (P-WIM) devices to ten sites with high frequency of SHLs in Texas. Subsequently, nondestructive field tests such as falling-weight-deflectometer (FWD) and ground-penetrating-radar (GPR) were performed during summer and winter months for back-calculation of the layer moduli. The field-derived data were in turn incorporated into a 3D finite element code for the characterization of pavement responses under different SHL-vehicle speeds. The numerical simulation results showed that slow movement of the SHL vehicle can essentially impart higher level of damages on the pavement structures compared to the same vehicle traveling at conventional highway speed. The increase in the cumulative damages associated with the slow-moving nature of the SHL vehicles can potentially jeopardize the longevity of pavements structures and result in premature failure of transportation facilities. Analysis of the representative pavements sections in this study revealed that inclusion of the slow-moving nature of SHLs into the damage assessment algorithms can result in significant PLR as high as 36%. Consequently, analysis of the slow-moving nature of the SHL vehicles should be an integral component in risk management studies of overload corridors
Influence of Traffic Characterization Methodology on Service Life Prediction of Pavements Subjected to Overweight Traffic Operations
No full textIn book: Infrastructure Sustainability Through New Developments in Material, Design, Construction, Maintenance, and Testing of Pavements (pp.57-74)Mechanistic-Empirical (ME) design and analysis of pavement structures are highly sensitive to the traffic data inputs. Hence, proper characterization of truck traffic is the key step for accurate assessment of performance and service life of pavements subjected to overweight (OW) traffic movements. Therefore, this study aimed to evaluate the impact of different traffic characterization methodologies on the predicted service life of pavements in overload corridors. To accomplish this objective, initially, the authors collected the site-specific traffic information by deploying Portable Weight-in-Motion (P-WIM) devices to ten representative pavement sections in Texas. Subsequently, non-destructive field tests such as Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR) were performed during summer and winter months for the back-calculation of the layer moduli in representative sites. Ultimately, different traffic data inputs, including the site-specific Axle Load Spectra (ALS), Equivalent Single Axle Load (ESAL) values, and software default values, as well as the pavement layer properties were incorporated into a series of ME analyses to estimate the service life of the pavements. The comparative analysis results indicated that the incorporation of ESAL and software default values in the analysis, instead of using site-specific ALS, substantially overestimated the service life of the pavements. Such deviation was more pronounced for pavement sections of Farm-to-Market roadways subjected to unprecedented OW traffic operations. Therefore, the traditional traffic characterization methodologies were not capable of representing the demanding loading conditions in the studied network. Further comparisons between the post-processed results and field distress records in this study showed that the most promising methodology to incorporate the traffic information into the service life analysis of pavements in overload corridors is the concept of the site-specific ALS
Infrastructure Truths for Air, Space, and Cyberspace
Full text linkThe importance of the air base and the physical infrastructure that it contains to the success of air operations is not a new concept. There is a general acknowledgment in the Air Force today that the air base itself is a “weapons system.” As former Secretary of the Air Force Dr. Heather Wilson stated with the release of the Infrastructure Investment Strategy (I2S), “in the Air Force, we fight from our bases. . . the places we call home are also the platforms from which we project combat power.” The Air Force major command (MAJCOM) commanders further stated that “the foundation of Air Force readiness and lethality is an integrated network of resilient installations that enable advanced-generation, multi-domain operations while also providing safe communities for our Airmen and families.” Nevertheless, budgets are tight, and it is often difficult to quantify the value provided to the mission through the investment in physical infrastructure or the risk to mission associated with neglecting infrastructure. To that end, this article describes a succinct set of “infrastructure truths,” clear statements of the foundational principles of infrastructure management. Airmen and Guardians can use these principles to guide advocacy and funding decisions at all levels of leadership. To set the stage for these truths, this article includes a brief history of the important role that air base infrastructure has played in airpower employment with logical extensions to space and cyberspace and a brief review of current doctrine pertaining to infrastructure. Although infrastructure has a broader definition in some contexts, including industries and institutions, the focus of this work is on the physical infrastructure—the facilities, airfield pavement, and utilities that are integral components of mission success
Verification of the Axle Load Spectra Databases Using Stationary and Portable Weight-in-Motion Devices in Overload Corridors of East Texas
Full text linkAxle Load Spectra (ALS) data collected from the Portable Weight-in-Motion (P-WIM) devices, provides the primary Mechanistic-Empirical (ME) traffic data input for optimal and accurate pavement design and analysis. Reliable readings from the P-WIM devices are the key factors that contribute to the accuracy of the analysis results. Therefore, this study was aimed to accurately assess the reliability and quality of the traffic data directly derived from the field data collection efforts. To accomplish this objective, the authors initially deployed P-WIM devices to US281 highway as a representative site in Texas overload corridors to collect the traffic data. The results were synthesized to compile the site-specific axle load spectra database, comprising of traffic information on the axle weights, vehicle classifications, and axle configurations. Subsequently, to assess the reliability of the collected data, P-WIM achieved traffic data were contrasted with those captured by the stationary WIM located at the vicinity of the evaluated site, using the available databases. Comparative analysis results indicated that traffic characterizations using the two WIM systems led to comparable outcomes, validating the accuracy and reliability of the P-WIM data measurements in the field. Additionally, as a practical means to investigate the quality of the recorded data, the longevity of the P-WIM piezo-sensors in several sites with different traffic patterns was investigated. Hence, the deterioration of the calibration factors over the operational life of the installed piezo-electric sensors in the field was analyzed. The post-processed results revealed that the piezo-electric sensors sustained substantial damage after nearly 37 days of operation in the field. Consequently, proper quantification of the ALS should include cross-validation assessments, as well as continuous evaluations of the calibration factors throughout the P-WIM data collection process to achieve good-quality, accurate, and reliable traffic data
Mechanistic approach to predict service life of flexible pavements subjected to heavy traffic loads
No full textOperation of specialty trucks with heavy axle and wheel loads can result in significant loss of service life of pavements. This study aimed to propose a mechanistic framework for the characterisation of the remaining service life (RSL) of pavements with heavy truck traffic operations. A field testing plan was devised to collect relevant information on traffic and pavement structural properties in ten heavily trafficked roadways in Texas. Portable Weight-in-Motion devices and Non-Destructive Testing were deployed to collect site-specific axle load spectra and pavement layer configurations, respectively. Furthermore, a novel methodology was developed for the mechanistic quantification of the loss of pavement life due to the recent changes in traffic characteristics, considering demanding loading conditions and environmental effects. The results underscored the importance of roadway type and its role in damage assessment procedures. Further comparison of the analysed results, using the developed framework, with field measurement records also showed sound agreements
Influence of acceleration and deceleration of Super Heavy Loads (SHLs) on the service life of pavement structures
Full text linkSuper Heavy Load (SHL) vehicles typically consist of heavy axles that impart substantial damages on transportation facilities such highway pavements and bridges. The taxing loading conditions, when combined with acceleration and deceleration forces from SHL vehicles, results in substantial interfacial shear stresses that manifests itself in premature failure of transportation facilities. This was the motivation for our research team to explore the detrimental effects of the acceleration and deceleration on the service life of roadways. To achieve this objective, our research team, initially deployed portable Weight-in-Motion (WIM) devices to ten sites with high frequency of SHLs in overload corridors of east and southeast Texas. Subsequently, nondestructive field tests such as Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR) were performed during summer and winter months for the back-calculation of the layer moduli in ten sites. The field observations and measurements were in turn incorporated in a three-dimensional (3D) finite element code for characterization of the influence of the acceleration and deceleration on the mechanical responses of the pavement structures. Then, a series of scenarios consisted of different patterns of acceleration, and deceleration were simulated in the 3D finite element software for ten sites and the results were contrasted with the steady rolling conditions. The sensitivity analyses of the representative pavements sections in this study showed that the deceleration or braking forces from the SHL vehicles resulted in the development of significant shear stresses in surface layers of thin structures. The stresses imparted by sudden changes in the velocity of super heavy vehicles can potentially jeopardize the longevity of the pavements structures and result in premature failure of transportation facilities. Therefore, analysis of acceleration and deceleration of the SHL vehicles should be an integral component in risk management studies of overload corridors
China's Strategic Arsenal : Worldview, Doctrine, and Systems
No full textOpen book - Check JSTOR for this book. 2021-01-01 - 2021-12-31China's strategic capabilities and doctrine have historically differed from the United States' and Russia's. China has continued to modernize and expand its arsenal despite its policy of no first use, while the United States and Russia have decreased deployed weapons stocks. This volume brings together an international group of distinguished scholars to provide a fresh assessment of China's strategic military capabilities, doctrines, and political perceptions in light of rapidly advancing technologies, an expanding and modernizing nuclear arsenal, and an increased great-power competition with the United States. Analyzing China's strategic arsenal is critical for a deeper understanding of China's relations with both its neighbors and the world. Without a doubt, China's arsenal is growing in size and sophistication, but key uncertainties also lie ahead. Will China's new capabilities and confidence lead it to be more assertive and take more risks? Will China's nuclear traditions change as the strategic balance improves? Will China's approach to military competition be guided by a notion of strategic stability or not? Will there be a strategic arms race with the United States? China's Strategic Arsenal provides a current understanding of these issues as we strive for a stable strategic future with China
Impact of super heavy load vehicles on transportation infrastructure: economic aspects
Full text linkSometimes, there is a need to transport very heavy equipment, so heavy that the resulting load is several times larger than the maximal load that the corresponding road segment was designed to withstand. Such super heavy load vehicles decrease the remaining service life of the road segment, and sometimes even make the segment unusable and needing repairs. In both cases, the need for earlier-than-expected repairs means additional costs. It is therefore desirable to estimate the expected value of this additional cost. In locations where the owner of the super heavy load vehicle pays for the vehicle passage, this is necessary to decide how much to charge the owner. In other locations, where the agreement is that the cost of additional repairs comes from the additional taxes that the vehicle owners pay, such an estimate is needed to the road owners—e.g., to the county or to the state—so as to select the route for which the expected additional cost of repairs is the smallest
Verification of the Axle Load Spectra Databases Using Stationary and Portable Weight-in-Motion Devices in Overload Corridors of East Texas
Full text linkConference Paper. Conference: Second ASCE India Conference on “Challenges of Resilient and Sustainable Infrastructure Development in Emerging Economies” (CRSIDE2020)At: Kolkata, IndiaAxle Load Spectra (ALS) data collected from the Portable Weight-in-Motion (P-WIM) devices, provides the primary Mechanistic-Empirical (ME) traffic data input for optimal and accurate pavement design and analysis. Reliable readings from the P-WIM devices are the key factors that contribute to the accuracy of the analysis results. Therefore, this study was aimed to accurately assess the reliability and quality of the traffic data directly derived from the field data collection efforts. To accomplish this objective, the authors initially deployed P-WIM devices to US281 highway as a representative site in Texas overload corridors to collect the traffic data. The results were synthesized to compile the site-specific axle load spectra database, comprising of traffic information on the axle weights, vehicle classifications, and axle configurations. Subsequently, to assess the reliability of the collected data, P-WIM achieved traffic data were contrasted with those captured by the stationary WIM located at the vicinity of the evaluated site, using the available databases. Comparative analysis results indicated that traffic characterizations using the two WIM systems led to comparable outcomes, validating the accuracy and reliability of the P-WIM data measurements in the field. Additionally, as a practical means to investigate the quality of the recorded data, the longevity of the P-WIM piezo-sensors in several sites with different traffic patterns was investigated. Hence, the deterioration of the calibration factors over the operational life of the installed piezo-electric sensors in the field was analyzed. The post-processed results revealed that the piezo-electric sensors sustained substantial damage after nearly 37 days of operation in the field. Consequently, proper quantification of the ALS should include cross-validation assessments, as well as continuous evaluations of the calibration factors throughout the P-WIM data collection process to achieve good-quality, accurate, and reliable traffic data
Impact of Super Heavy Load Vehicles on Transportation Infrastructure: Economic Aspects
Full text linkSometimes, there is a need to transport very heavy equipment, so heavy that the resulting load is several times larger than the maximal load that the corresponding road segment was designed to withstand. Such super heavy load vehicles decrease the remaining service life of the road segment, and sometimes even make the segment unusable and needing repairs. In both cases, the need for earlier-than-expected repairs means additional costs. It is therefore desirable to estimate the expected value of this additional cost. In locations where the owner of the super heavy load vehicle pays for the vehicle passage, this is necessary to decide how much to charge the owner. In other locations, where the agreement is that the cost of additional repairs comes from the additional taxes that the vehicle owners pay, such an estimate is needed to the road owners -- e.g., to the county or to the state -- so as to select the route for which the expected additional cost of repairs is the smallest