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The concept of frailty has been suggested to comprise physical, mental, and social phenotypes. However, there is no general consensus about the appropriate components for assessing frailty. The purpose of this study was to reach consensus on components of frailty assessment using the Delphi process. To achieve consensus on the definition of frailty, a modified Delphi method was used. Geriatric and gerontologic experts were selected from various fields. The detailed components of frailty were composed of data from the Korean Frailty and Aging Cohort Study. Establishing consensus and collecting opinions from experts were conducted using a modified Delphi method. Overall, nine domains with 14 components of frailty assessment were accepted. There was consensus on the necessity of a broad phenotype including physical, mental, and social frailty. Consensus on the components of a frailty assessment in a clinical setting is achieved through the Delphi process to establish a new tool of frailty assessment.

In Portland cement concrete (PCC) pavements, tie bars are commonly used at longitudinal construction joints (LCJs) to prevent the lanes from separating. Meanwhile, the increase in multiple lanes due to greater traffic volumes has raised concerns about potential longitudinal cracking, this has led to the use of dowel bars instead of tie bars at LCJs. However, there is a paucity of studies focused on the comparison between the behaviors of concrete pavement based on the restrained conditions provided by tie and dowel bars at LCJs. In this study, we investigated the effects of the placement of tie and dowel bars at LCJs on the potential for longitudinal cracking in response to the increase in concrete stress that may occur when the lanes are tied together in PCC pavements. Field testing verified that the variation in concrete strain was more restrained in the case of a tie bar than a dowel bar, whereas it resulted in higher stress in the concrete element in the tie bar section. However, the use of dowel bars caused more movement in the transverse direction at LCJs as compared with tie bars. Thus, our results indicate that using dowel bars reduces the potential for longitudinal cracking, however, it may increase the potential for lane separation.

In continuously reinforced concrete pavement (CRCP) research, it has been assumed that transverse crack spacing plays an important role in determining CRCP behaviour and performance. For the longit...

Fly ash is widely used in the cement industry to improve the performance and durability of concrete. The future availability of fly ash, however, is a concern, as most countries are inclining towards renewable energy sources as opposed to fossil fuels. Additional concerns have been raised regarding the impact of strict environmental regulations on fly ash quality and variability. This paper, therefore, evaluates if nano calcium carbonate (nano CaCO3) can be used as an alternative to fly ash. This paper presents comprehensive testing results (fresh, hardened, and durability) for OPC (Ordinary Portland Cement) and PLC (Portland Limestone Cement) concretes with 1% nano CaCO3 and compares them to those for concretes with fly ash (both Class F and C). Compared to concretes with fly ash, OPC and PLC with nano CaCO3 presented improved testing results in most cases, including later age strength, permeability, and scaling resistance. As nanotechnology in concrete is a relatively new topic, more research on the efficient use of nanotechnology, such as for proper dispersion of nano CaCO3 in the concrete, has potential to offer increased benefits. Further, nano CaCO3 is environmentally and economically viable, as it has the potential to be produced within the cement plant while utilizing waste CO2 and generating economic revenue to the industry. Thus, nano CaCO3 has the potential to serve as an alternative to fly ash in all beneficial aspects—economic, environmental, and technical.

The authors apologize for a typing error that occurred in the September 2020 article that changes the meaning of a sentence.

Understanding spin textures in magnetic systems is extremely important to the spintronics and it is vital to extrapolate the magnetic Hamiltonian parameters through the experimentally determined spin. It can provide a better complementary link between theories and experimental results. We demonstrate deep learning can quantify the magnetic Hamiltonian from magnetic domain images. To train the deep neural network, we generated domain configurations with Monte Carlo method. The errors from the estimations was analyzed with statistical methods and confirmed the network was successfully trained to relate the Hamiltonian parameters with magnetic structure characteristics. The network was applied to estimate experimentally observed domain images. The results are consistent with the reported results, which verifies the effectiveness of our methods. On the basis of our study, we anticipate that the deep learning techniques make a bridge to connect the experimental and theoretical approaches not only in magnetism but also throughout any scientific research.

In South Korea, the performance of continuously reinforced concrete pavement (CRCP) has been better than that of jointed concrete pavement (JCP). However, most of the Portland cement concrete (PCC)...

The performance of Portland Cement Concrete pavement depends on the support provided by layers under the concrete slab. Considering the importance of slab support on concrete pavement performance, a good quality assurance testing is needed for the construction of layers under the concrete slab. Deflection measurements on stabilized base could provide sound quality assurance testing. A threshold deflection value for construction acceptance was developed from the analysis of the field deflection data as well as theoretical analysis. Based on the information obtained, a protocol for quality assurance testing for base and subgrade construction was developed.

Lane separations at longitudinal joints not only allow water to infiltrate into layers under the concrete slabs and deteriorate slab support, but degrade load transfer efficiency (LTE) along longitudinal joints, resulting in an increase in load-related stresses in concrete slabs and poor performance of pavement. Slot stitching provides one of the more efficient methods to restore pavement structural capacity due to lane separations. In 2010, three slot stitching design configurations were implemented on US-75 in Sherman, Texas, which experienced lane separations as well as faulting along the longitudinal construction joint. After the dowel bars were installed, the ultra rapid repair method with the use of high early strength, low shrinkage, and low coefficient of thermal expansion (CoTE) backfill materials was utilized to minimize the traffic interruption and to restore the elevation. For measuring the effectiveness of the repair method, LTE at longitudinal joints was evaluated using Falling Weight Deflectometer (FWD). Testing results in this paper demonstrate the effect of slot stitching design, or more specifically the number of slot stitching in a slab and/or bar size, on improving LTE by providing before-and-after LTE measurements and detailed material information. In particular, the design configuration with 5 #8 bars (25.4-mm diameter) was the most cost-effective and efficient, with about 28% improvement in LTE after more than 4 years of service. Moreover, three design configurations with the use of low-shrinkage, low-CoTE backfill materials were demonstrated to improve LTE substantially, with an average increase from 45% to 74%.

The original version of this article contained an error in Table and manuscript. The correct information Table and manuscript should be as follows. The authors would like to apologize for any inconvenience caused.

To determine the percentage of children with autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and combined ASD + ADHD who had sleep problems documented by developmental-behavioral pediatricians at diagnostic and follow-up visits at 12 US academic medical centers comprising the Developmental-Behavioral Pediatrics Research Network (DBPNet) and to identify the predictors of sleep problem documentation.Developmental-behavioral pediatricians completed encounter forms that covered sociodemographic, medical, clinician, and visit factors. There was 1 dependent variable, sleep problem documentation, for which 4 definitions were developed (Model 1 = Sleep Disorder coded; Model 2 = Sleep Disorder or polysomnogram coded; Model 3 = Sleep Disorder, polysomnogram, or sleep medication coded; and Model 4 = Sleep Disorder, polysomnogram, sleep medication, or clonidine coded).Sleep problem documentation was 14.1% for Model 1, 15.2% for Model 2, 17.3% for Model 3, and 19.7% for Model 4. All values were lower (p0.001) than the reported prevalence of sleep problems in these conditions. For Model 4, predictors of sleep problem documentation were age group, ethnicity, medical insurance type, and DBPNet site.Developmental-behavioral pediatricians in DBPNet under-reported sleep problems in children with ASD and ADHD. Variation among sites was substantial. Care plans for children with ASD and ADHD should specify which treating clinician(s) monitors sleep issues.

The objective of this study is to suggest reasonable structural evaluation method of continuously reinforced concrete pavement (CRCP) using falling weight deflectometer (FWD). The effects of transverse crack spacing and temperature conditions were investigated in CRCP sections with various slab thicknesses and pavement ages. A total of 20 CRCP sections were selected throughout Texas and structural responses were evaluated from 2006 to 2013 for 8 testing years. Test results show that transverse crack spacing has little effect on deflection and load transfer efficiency (LTE). The LTE values were maintained at above 90%, regardless of crack spacing, temperature condition or pavement age. Temperature variations had small effects on deflections at cracks and the mid-slab, but almost no effects on LTE. Maximum deflections and back-calculated k-values appear to be better indicators of structural condition of CRCP than LTE. Load transfer efficiency is not the best indicator of structural condition of transverse cracks in CRCP. Deficiencies in slab support are the primary cause of full-depth distresses in Texas, and back-calculated k-values, which combine both a maximum deflection and the shape of deflection bowl from FWD testing, may be a better indicator of the structural condition of CRCP.

Reflective cracking potential in hot mix asphalt (HMA) overlays on Portland cement concrete (PCC) pavement depends on the condition of PCC pavement in terms of slab stability at discontinuities (cracks and joints) and asphalt material characteristics in terms of their ability to resist reflective cracking. To develop a more comprehensive HMA overlay on PCC pavement program that minimizes reflective cracking potential and thus improves HMA overlay performance, TxDOT employed evaluation tools for both continuous deflection measurement of PCC slabs and overlay mix material characteristics. Rolling Dynamic Deflectometers (RDD) evaluate deflections on pavement surface continuously, providing valuable information on the stability of concrete slabs and load transfer efficiencies at discontinuities such as cracks and joints. Overlay testers (OT) evaluate the capacity of asphalt mixtures to resist reflective cracking. Since the performance of HMA overlay on PCC pavement depends on the extent of reflective cracking, design criteria should be developed for both slab stability and asphalt material properties. To that end, RDD and OT were utilized for the evaluations of HMA overlay on PCC pavements in four projects in Texas: (1) IH20, (2) SH225, (3) SH12, and (4) US96, with the objective of developing design criteria. This paper documents the efforts made to evaluate the PCC pavement condition before overlay, overlay material properties, and long-term performance of the four sections. CAM and SMA mixtures have been used successfully to retard reflective cracking, as they have exceeded eight years of life expectancy. Threshold values were validated for slab stability and asphalt materials, and applied for the designs of three rehabilitation projects.

Significant efforts have been made to identify the correlations between pavement design, materials and construction variables and pavement performance for new pavement construction; in response to these efforts, specifications and design standards have been developed to optimize pavement performance. On the other hand, less positive correlations have been found between pavement repair materials/methods and the performance of repairs. This issue is primarily due to the incompatibility between existing pavement and repair materials including bonding at the repair interface, as well as the complex nature of pavement behavior near distressed areas. As a result, the variability in the performance of pavement repairs has been rather large. As more pavement sections have reached or even exceeded their design lives, with more frequent distresses, it is important to identify optimum repair methods and/or materials. This paper presents the field performance of several repair strategies with Fiber Reinforced Polymer Patching Binder (FRPPB) patching material for the repairs of spalling, partial-depth punchout and longitudinal joint separations in rigid pavement, for retarding reflection cracking in asphalt overlay on jointed concrete pavement, and for repairs at the transition area between rigid and flexible pavements by the Texas Department of Transportation (TxDOT). The repairs for these distress types have been a challenge to TxDOT districts; repair specifications with acceptable properties of repair materials and methods have not been as well-developed as the specifications for new construction have, resulting in a large variability in the performance of repairs of these distresses. The performance of repairs for the distresses mentioned above with FRPPB has been excellent, with no need for repeated repairs up to this point. The results from this study indicate that if the right materials are used for repairs, along with the correct repair method, the performance of pavement repairs and rehabilitations could be substantially enhanced, minimizing traffic delays and financial resources associated with further repairs and rehabilitations.

The transverse crack in continuously reinforced concrete pavement (CRCP), more specifically transverse crack spacing and crack widths, has been cited as one of the most important pavement structural responses determining CRCP performance. Efforts have been made to predict crack spacing and crack widths for given environmental conditions and traffic loading, pavement structure, and material properties, with the primary objective of developing rational CRCP designs. However, that most transverse cracks develop at or near transverse steel implies substantial interactions between transverse steel and other factors causing transverse cracks. These interactions have not been fully incorporated in the theoretical models developed so far to predict transverse crack spacing and crack widths in CRCP. This study investigated the interactions between transverse steel and other factors and identified the mechanisms of transverse crack development at or near the transverse steel. Drying shrinkage and temperature drop in concrete cause concrete volume contractions in all directions (not just transverse and longitudinal, but vertical directions as well). Interactions between concrete volume contraction vertically and transverse steel cause larger concrete tensile stresses at or near transverse steel than at other areas and cause a higher probability of transverse cracks near transverse steel. Traditionally, subgrade drag theory has been used in the design of transverse steel even though current practice is to place just enough transverse steel to support longitudinal steel during concrete placement. If transverse cracks have such substantial effects on CRCP performance as currently thought, interactions between transverse steel and other factors should be considered in the design of optimum transverse steel.

The long-term performance of continuously reinforced concrete pavement (CRCP) has been quite satisfactory in Texas, providing an important network of highways with heavy truck traffic and minimal maintenance. However, certain forms of distresses were observed within a few years after construction, requiring repair of the distresses and causing traffic delays. Distresses at transverse construction joints (TCJs) were one of the most frequently observed distresses, and efforts were made to identify the mechanisms of those distresses and develop or improve design standards or specifications. Field evaluations of concrete and steel behavior near TCJs were made using various gages. The analysis of the data indicates that the current practice of placing additional tie bars at TCJs, along with poor construction practices, are the major causes of the distress. There is a large difference in the behavior of reinforcement between additional tie bars and longitudinal steel that is continuous through transverse construction joints. The premise that additional tie bars at TCJs will behave the same way as longitudinal steel, thus reducing steel stresses of longitudinal steel at TCJs, keeping the joint widths tight, and improving TCJ performance, is not necessarily correct. Also, the use of additional tie bars makes the consolidation of concrete at TCJs difficult due to the reduced spacing between longitudinal reinforcing steel. Not placing additional tie bars at TCJs, and the use of relief transverse saw cut joints near TCJs, along with improved construction practices at TCJs, will minimize the distresses.

Some of the conventional Full-Depth Repairs (FDR) in Jointed Concrete Pavement (JCP) suffered recurring failures in less than one year. Under very heavy truck trafficking, tie bars were ruptured, and the slabs were settled for as much as 100 mm. This indicates the conventional method of slab replacement does not address the underlying problem. Falling Weight Deflectometer (FWD) and Dynamic Cone Penetrometer (DCP) were utilized to determine Load Transfer Efficiency (LTE) and base/subgrade support conditions, respectively. After one month of the heavy truck trafficking since opening to traffic, some transverse joints had LTE less than 10%. DCP results confirmed extremely weak base/subgrade support. It was concluded that the weak base/subgrade support was one of the main culprits for the recurring failures. For more effective repair of failures in JCP with heavy truck traffic, an innovative FDR technique with two layers of steel reinforcements and tie/dowel bars to adjacent JCPs was developed. The weak and poor base/subgrade layers were completely removed and replaced with concrete and steel reinforcements. Both longitudinal and transverse repair joints were designed considering the compatibility of concrete volume changes between the existing JCP slabs and repair slabs. Condition survey results indicated that the performance to date has been excellent with no visible distress under almost two years of the heavy truck traffic. For the repair of JCP sections with recurring failures, the implementation of the proposed technique with steel reinforcements and joint designs is expected to result in improved performance.

A critical challenge to our nation’s Intelligence, Surveillance, and Reconnaissance (ISR) community is the complex task of identifying clandestine networks in cultural “clutter” for counter-terror / counter- insurgency operations. MIT Lincoln Laboratory has developed an ISR “Red/Blue” exercise in which teams work to uncover a complex “Red” network within a simulated urban environment. Teams use wide-area persistent surveillance data and decision support tools to trace relationships between individuals, events, and sites. This exercise was used to investigate the influence of resources on teamwork and performance, modeling the activity as a two-stage decision process, and using Signal Detection Theory (SDT) as a framework to describe performance at each stage and derive metrics to describe teamwork. Team performance and teamwork were investigated within the naturalistic behavior of self-organizing teams, comprising of different organization structures, teamwork behaviors, and communication interactions that were promoted by resource allocation. The affordances provided by available resources drove the mechanisms for communication and collaboration that distinguished the different team types. The research was executed in two phases. Phase 1 involved 46 teams, of varying team size (1, 3, 4, 6, 8) and number of computers per team (1, 2, 3, 4, 6). Results from Phase 1 showed that increasing resources (people and computers) had the potential to improve performance, but once team size grew beyond an optimal size, it caused degradation in performance. Phase 1 also showed that balanced communication interactions amongst team members were indicative of better teamwork. This phase also demonstrated that the exercise, as a two-stage process, could be decomposed into taskwork and teamwork components. Phase 2 extended the study by focusing on the teamwork component of the process within 3-person teams. By holding the team size variable constant, the investigation specifically studied the effect of resource allocation (1, 2, or 3 computers) on teamwork, organization, and performance. Phase 2 results showed that providing each team member his/her own information source (computer), which provided each person the direct ability to produce and process information, resulted in improved teamwork and performance. The indication, then, in designing high performing teams, would be to facilitate each person’s ability to acquire, generate, process, and share their own information as active contributors to the team process and performance.

The current mechanistic-empirical pavement design guide (MEPDG) postulates that zero-stress temperature (ZST) has substantial effects on the behavior and performance of Portland cement concrete (PCC) pavements. To date, the only available ZST prediction model for PCC pavements is the one proposed by the MEPDG, which was quite simplified with a function of only two input variables: cementitious content and mean monthly temperature for the month of construction. In this study, the feasibility of the current ZST prediction model in the MEPDG was assessed by comparing the ZSTs evaluated from a series of field tests with the ones estimated from the MEPDG model. In order to find ZSTs in actual PCC pavements, accurate evaluations of early-age concrete stress developments were essential. To achieve this aim, non-stress cylinders (NCs), which directly measure stress-independent strain in the field concrete structures, were employed. Once the stress-dependent strain history was estimated based on the measured total and stress-independent strain histories, it was converted to the stress history using a step-by-step numerical method considering creep and modulus developments of concrete. The results of this study showed that about 4.5–7.7 °C of differences existed between the measured and predicted ZST values. This finding strongly suggests a need for development of a more advanced ZST prediction model with reasonable assumptions and diverse parameters.

The Texas Department of Transportation has by far the most continuously reinforced concrete pavement (CRCP) lane miles in the nation, and sections as old as 50 years are still in service. Having served much longer than intended, some sections are showing distress. Full-depth repair (FDR) is one of the methods used to repair CRCP distresses in Texas. Over the years, various FDR methods have been used, and the effectiveness of each method has varied. In the most widely used FDR method, a full-depth cut is made at a minimum of 1.5 ft (0.46 m) inside the transverse repair boundaries, a partial-depth cut is made at repair boundaries, and the concrete between the cuts is removed to expose longitudinal steel. The method has inherent disadvantages, the longer repair time being the primary one. The full-depth cut FDR method, in which a full-depth cut is made at the repair boundaries and longitudinal tie bars are epoxy grouted into the existing concrete, has advantages over other methods, including a faster operation that minimizes roadway closure time. Because CRCP is normally used in areas with high traffic volume, the maximum time the Texas Department of Transportation allows for the FDR operation is usually 9 h, which makes the full-depth cut method the only acceptable repair method. Factors affecting the effectiveness of the full-depth cut method were investigated with laboratory testing and field evaluations. The method of epoxy injection, keeping the epoxy in the holes after insertion of the tie bars, restoring base support, and the length of the embedded tie bar were the most important variables affecting the performance of FDR. Recommendations were made to revise specifications for FDR and epoxy materials on the basis of these research findings. Implementation of the recommendations should result in improved FDR performance of CRCP.

Curing of concrete has substantial effects on the performance of Portland cement concrete (PCC) pavement. The effectiveness of membrane-forming curing compound depends on the quality of curing materials, time of curing compound application in relation to bleeding and evaporation, and amount and uniformity of curing materials applications. This study presents the efforts to develop simple compliance testing for application rate and uniformity. Compliance testing was based on the speed control of a curing machine utilizing a non-contact Doppler radar speed sensor and wireless data logger system. The findings from trial implementations of this method in PCC paving projects include: (1) speed control of a curing machine could be the most practical and simplest method for compliance testing; (2) Doppler sensor and wireless data logger showed fairly good performance and can be an effective and practical curing compliance testing system; and (3) as wind speed increases, the loss of curing compound tends to increase nearly proportionally.

This paper proposes a robust adaptive backstepping synchronization method for a class of uncertain chaotic systems. Unknown factors including system uncertainties and external disturbances are estimated by a fuzzy disturbance observer. By use of the fuzzy disturbance observer, any prior information about the unknown factors is not need. The proposed method using the estimated values guarantees the global synchronization for chaotic systems with mismatched uncertainties in the sense of uniform ultimate boundedness. Finally, numerical examples are presented to show the effectiveness of the method.

Portland cement concrete (PCC) pavements have long been thought to expand and push bridge structures, with bridge damage resulting. To protect bridge structures from expanding PCC pavements, three terminal systems are currently used in Texas: anchor lug (AL), wide flange (WF), and expansion joint (EJ). Even though the Texas Department of Transportation uses all three systems in continuously reinforced concrete pavement (CRCP), the effectiveness of these three systems has not been fully evaluated. The parameters affecting CRCP movement near bridge terminal areas are investigated: whether thermal expansion of CRCP is damaging bridge structures, and if so, which terminal type is most cost-effective. Extensive field evaluations reveal that slab movement at the end of the CRCP are substantially restrained by subbase friction. Slab length from the end of the CRCP that significantly contributes to slab movement is limited to about 200 ft (60.96 m) for the CRCP system with asphalt base typically used in Texas. Slab movement rates due to seasonal temperature variations are larger than daily slab movement rates. The movement at the end of the CRCP can be accommodated by a simple EJ with subbase friction, which can be achieved with typical asphalt-stabilized base. The use of an AL system is not needed to restrain concrete slab movement. The benefits of WF and AL systems are doubtful when one considers that their cost is higher than that of the simpler EJ system.

The objective of this study is to identify the mechanisms and associated variables of horizontal cracking in continuously reinforced concrete pavement (CRCP) and to develop mitigation methodologies. To this end, the laboratory and field testing were carried out. The behavior of CRCP at relatively early ages under environmental loadings was measured and compared with numerical analysis. The effect of factors related to design, materials, and construction on the horizontal cracking potential was evaluated through the comprehensive numerical analysis. It is expected that this study could help develop or improve design standards and/or material or construction specifications to prevent distress from horizontal cracking in CRCP.

In the last 10 years, TxDOT has utilized Dowel Bar Retrofit (DBR) in five projects. International Roughness Index (IRI), Falling Weight Deflectometer (FWD), Rolling Dynamic Deflectometer (RDD), and coring were employed to evaluate DBR effectiveness in those five projects. Different versions of special specifications were utilized for each DBR project. The main variables in different versions of the specifications are grout material and slot width requirements. Out of the five projects, four projects (SH73, SH73/SH87, US69, and US287) have performed to the designers’ satisfaction. Those four projects demonstrated that DBR was able to improve Load Transfer Efficiency (LTE) and minimize reflective cracking on an AC overlay. The US69 project reveals that after DBR, Diamond Grinding (DG) should be applied to restore the ride quality. Faulting of greater than 25 mm has been successfully corrected by DBR and DG on the US287 project, which still provides good ride quality after 6 years of service. The experiences from these four projects suggest that DBR with either DG or an AC overlay can be used effectively to extend pavement life and restore the ride if it is done properly. However, on the US59 project, the DBR performance is unsatisfactory. Visible faulting of 6.4 mm–9.4 mm developed in less than 2 years. It was found that the primary cause for the unsatisfactory performance was excessive voids under the dowel bar, which prevented proper load transfer at the joint. X-ray tomography results indicate that approximately 50% of the area under the dowel was void. The following four main variables were investigated in the laboratory for potential causes for voids around dowels: (1) time of placement after grout mixing, (2) vibration time of grout, (3) slot width, and (4) maximum aggregate size. It was found that maximum aggregate size, in the range of 9.5 mm–12.7 mm was not a critical factor for the consolidation of the grout. Although slot width above 63.5 mm may be beneficial, it was not a critical factor for grout consolidation either. The factors that had significant effects on consolidation of the grout were time of placement after mixing and vibration time. Delayed placement of the grout without vibration led to substantial voids. These two factors might be the causes for the voids under dowels that led to poor performance of DBR on US59. The most significant factor for the consolidation of grout materials is vibration. Although vibration has been included in the current Texas Department of Transportation (TxDOT) special specifications for DBR, it should be properly enforced to ensure optimum consolidation. Based on the test results, 20 s of vibration is recommended for each slot. In addition, it is preferable to place grout into the slots before the initial set takes place, or within the manufacturers’ recommended working time.

In 2005, the Texas Department of Transportation initiated a rigid pavement database to collect information in preparation for the calibration and potential implementation of the Mechanistic–Empirical Pavement Design Guide (MEPDG) for continuously reinforced concrete pavement (CRCP). Twenty-seven sections, each 300 m (1,000 ft) long, were selected throughout the state. Deflection testing was conducted with a falling weight deflectometer. The information collected included load transfer efficiency (LTE) at small, medium, and large crack spacing for two different seasons, summer and winter. Also collected were crack-spacing information and slab deflections. LTE values for all the cracks were higher than 90% regardless of slab thickness, pavement age, crack spacing, or season. Mechanisms of primary distresses in CRCP were investigated. The investigation tentatively revealed that many distresses identified and recorded as punch-outs in Texas were not actually caused by structural deficiency. Rather, most of the distresses were caused by imperfections in design details, construction or material quality issues, or both. Horizontal cracking appears to be the major cause of distresses in CRCP in Texas. The interactions between longitudinal steel and concrete in response to dynamic wheel loading applications appear to be the cause of horizontal cracking. From the findings, mechanistic–empirical (ME) CRCP design procedures and a calibration function were developed. Because the accuracy of any ME design procedure depends to a great extent on the reasonableness of the transfer function, further efforts will be made to improve that function.

The design method of whitetopping in Texas is a method suggested by the American Concrete Pavement Association (ACPA). However, one of the limitations on this particular design method is that an existing asphalt pavement condition is not considered for slab thickness. Recently, the Texas Department of Transportation developed an improved whitetopping design procedure considering mechanistic-empirical (ME) behavior. In the present study, performance of whitetopping projects constructed by the ACPA design method in Texas were investigated, and improved design details were suggested in order to minimize distresses, such as corner break and slab movement, in transition areas. To evaluate the structural performance of whitetopping, various tests, including the falling weight deflectometer, ground penetration radar, and investigation of concrete coring were conducted on US 90. According to the field survey and tests results, most of the distress was caused by insufficient slab support conditions related to asphalt concrete pavement materials and inadequate slab thickness design. In addition, early-age behavior of whitetopping constructed by the improved ME design method was evaluated and analyzed, and various gage installations, such as vibrating wire strain gage, electric resistance-type strain gages, porous nonstress cylinder, and impervious nonstress cylinder, are discussed.

Tie bars are used at longitudinal construction joints (LCJs) in portland cement concrete (PCC) pavement primarily to keep lanes from separating. As more lanes are tied together because of ever-increasing traffic volume, concerns about the potential for longitudinal cracking have led to the use of dowel bars at LCJs. However, a survey of a number of state highway agencies (SHAs) revealed that few of them have guidelines and design standards for the use of dowel bars at LCJs and that no in-depth studies conducted in this area have been identified. The effects of multiple lane ties and dowel bar placements in PCC pavements are analyzed in this paper to provide basic information on whether dowel bars are really needed, and if they are, where they should be placed and what their advantages and disadvantages are. Field testing verified that the longitudinal cracking potential is greater as slab thickness and lane width increase. The effects of multiple lane ties and dowel bar placements at LCJs are evaluated with numerical analysis. Placing dowel bars in lieu of tie bars reduces the longitudinal cracking potential, and the effectiveness of using dowel bars is enhanced when they are applied to thicker and wider pavements. However, the use of dowel bars could result in increased potential for lane separations.

The performance of cast-in-place posttensioned concrete pavement (PTCP) constructed in 1985 on I-35 in Waco, Texas, has been excellent. Encouraged by the performance of the section, the Texas Department of Transportation began construction of another PTCP project in 2008 on I-35 in Hillsboro. In this study, the time-dependent behavior of PTCP under environmental loading was experimentally investigated and its implications in PTCP design investigated. Concrete strain and slab movement as well as temperature and relative humidity were measured. The effects of such factors as posttensioning (PT) force, friction, curling stress, creep, and shrinkage on the behavior of PTCP were investigated. The stress introduced by longitudinal PT varied along the slab length, with a maximum near the armor joint and a minimum at the center of the slab. The variations were induced by the friction between concrete and subbase. The concrete strain at middepth of the slab under environmental loading was also affected by friction. The concrete thermal strain restrained by friction was larger near the slab center, and the degree of restraint was 20%. The distribution of longitudinal slab movement was nonlinear along with the distance from the slab center, and 13% of free slab movement was restrained at the armor joint. Continued contraction of the concrete slab due to creep and shrinkage was observed, which will result in the opening of joint width. Because creep and shrinkage are long-term effects, slab movement monitoring will continue until their effects become insignificant and the information gained should be used for the design of initial joint width.

A section of jointed concrete pavement on U.S. 75, which was built from 1982 to 1985, in the Paris District of the Texas Department of Transportation (TxDOT) experienced severe pumping and settlement, even though two types of treatment (full depth repair and polyurethane foam injection) were performed. An extensive field investigation was conducted using ground penetrating radar, falling weight deflectometer, dynamic cone penetrometer, and coring to identify the causes of the continued pumping and settlement problems, and develop an optimal repair strategy. The pavement evaluation included tie bar condition, load transfer efficiency (LTE) at transverse and longitudinal construction joints, and base support conditions. Some of the tie bars failed in shear due to corrosion, which resulted in substantially low LTEs (

Spalls and wide cracks represent functional and structural distresses in portland cement concrete pavement. Traditionally, these distresses were repaired by partial depth repair (PDR). The performance of PDR varies substantially. Two types of polymeric patch materials, Material-A and Material-B, were used to repair spalls and cracks. Material-A was used to repair spalls in continuously reinforced concrete pavement. It provided quite satisfactory performance for more than 6 years. Material-B was used to repair cracks in jointed concrete pavement. Its performance was satisfactory when applied to stable slabs. Compared with full-depth repair (FDR), PDRs utilizing polymeric patch materials is much more cost effective, and PDR takes much less time than FDR. It was found that chip-and-patch method would work as well as saw-and-patch method as long as the repair limits include all the delaminated areas.

Where faulting takes place due to the absence of dowel bars and inadequate subbase support in jointed concrete pavement (JCP), dowel bar retrofit (DBR) is used to improve load transfer efficiency (LTE) and to prevent further faulting of slabs at transverse joints. Even though DBR generally improves LTEs and overall performance of JCPs, not all DBR projects have been successful. Faulting reoccurred within 2 years after DBR treatment on US59 in Texas. An investigation from the cores taken in the project revealed excessive voids under a dowel bar due to poor consolidation of the grouting material. A laboratory investigation was performed to determine the most critical factors for adequate consolidation of grouting materials in DBR. Typical rapid-setting grout materials widely used in DBR were selected and full-scale specimens were made for evaluations. Four testing variables for consolidation performance were investigated: time of placement after mixing, vibration time, slot width, and maximum aggregate size. Maximum aggregate size and slot width were not critical factors for consolidation performance of grout. The most significant factor was vibration time. Twenty s of vibration is recommended. Placement time was also an important factor, with grout materials placed after initial set performing poorly. Delayed placement of grout materials without vibration led to the most voids under the dowel bars.

Tie bar design at longitudinal construction joints in portland cement concrete pavement is based on the so-called subgrade drag theory. According to this theory, the required maximum spacing between tie bars is inversely proportional to the widths of the lanes that are tied together. As the number of lanes increases to accommodate greater traffic demand, tie bar spacing decreases. In a recent IH-10 project in Houston, Texas, the width of pavement lanes tied together was great enough to require 30-cm (1-ft) tie bar spacing. In Texas Department of Transportation design standards for continuously reinforced concrete pavement, the same spacing is required for both tie bars and transverse steel. The use of 30-cm spacing for both tie bars and transverse steel results in a substantial increase in the cost of the project. The subgrade drag theory assumes uniform temperature distribution through the concrete slab depth and no curling effect is incorporated. This assumption needs reconsideration. Field testing was conducted to investigate slab behavior and to develop more rational designs for tie bars and transverse steel. Concrete displacement gauges were installed at the free edge of the concrete slab to measure transverse horizontal as well as vertical displacements. Steel strain gauges were installed at different locations in tie bars. The concrete slab showed curling behavior; the stresses in tie bars clearly demonstrated the effects of curling. Theoretical analysis was conducted, and the results verified the field data. A new design method was proposed for tie bars.

In Texas, many miles of plain jointed concrete pavement (JCP) were constructed without proper load transfer devices such as dowels. After a number of years of service, some JCP sections without dowels showed distresses in the form of faulting at transverse joints. Some of the sections were designed in accordance with the AASHTO 1986 Guide, which required 50–75 mm thicker slabs in exchange for not using dowels. This pavement design did not work, with faulting at transverse joints that cause poor ride. Dowel bar retrofit (DBR) was performed on four projects to restore the pavement condition. Overall, DBR restored load transfer efficiency and resulted in improvement of ride quality. Even where the subbase stiffness is 5–10 times less than the minimum value required for proper performance of JCPs, properly installed DBR effectively restored pavement condition with minimum faulting after decades of service. Therefore, it indicated that DBR is able to minimize the faulting even where there is poor base/subgrade...

It is well-known that the performance of Portland cement concrete (PCC) pavement depends, to a great extent, on the support condition under the slab. The Texas Department of Transportation (TXDOT) recognized the importance of the support condition and requires the use of a stabilized base, either a 10.16-cm hot mix asphalt layer or a minimum 2.54-cm asphalt concrete over a 15.24-cm cement-stabilized layer. For pavement design purposes, 81.4 MPa/m has been used as the default value for the modulus of the subgrade reaction (k value) for the support provided by these bases. The use of a single value of 81.4 MPa/m for the k value in rigid pavement design was partly because of the insensitivity of the required slab thickness to the modulus of the subgrade reaction in the current TXDOT rigid pavement design procedure. To improve rigid pavement design, TXDOT developed a new design procedure for continuously reinforced concrete pavement (CRCP) on the basis of mechanistic-empirical principles and plans t...

In the safety-critical environment of air traffic control, increases in system efficiency in the form of cost, capacity, and safety are primary drivers for integrating automated decision support tools (DSTs) into the National Airspace System (NAS). However, increased use of automation brings new concerns, including the impact on operator situation awareness, over- or under-reliance on automation, and the ability of the system to recover to a suitable performance level when faced with degradation or off-nominal situations. Such effects may create a brittle system—one that performs well under normal conditions but poorly when faced with degraded or adverse situations. As automated tools become critical components in air traffic management, it will be necessary to have clear guidelines to aid the development of human-computer systems to protect against system brittleness. This work identifies key factors that contribute to human-system resiliency and proposes a series of relationships between these factors to provide a framework for guiding the development of system resiliency requirements in the context of air traffic management. The identification of such relationships will facilitate the development of guidance intended to help stakeholders proactively incorporate resiliency into human-automation systems that are being developed currently and in the future as part of the NextGen air traffic modernization effort.

As a compaction control parameter, stiffness has been investigated as an alternative to dry unit weight, because the design of pavement is based on the elastic modulus of pavement layers. A reliable and practical quality assurance system was proposed to accelerate the quality assessment of field compaction. The proposed system, which has evolved from the spectral analysis of surface waves (SASW) method, profiles the shear wave velocity of the unbound aggregate base and subgrade. The system consists of dedicated hardware for surface wave measurements and an analysis algorithm to automate the interpretation and analysis procedures. The measurement hardware consists of two sensor units and one source unit and can be operated by one person. The automation in interpretation and analysis was implemented with the peak–trough method and the frequency wave number technique. Consequently, the surface wave measurement for stiffness profiling is reduced to a 10- to 15-min task. The validity of the proposed hardware and algorithm was verified by a comparison of the results acquired by the conventional SASW measurements with the results acquired by the accelerated SASW system. Twenty-one subgrade and 11 base sections were selected at three pavement construction sites and tested with the accelerated SASW system, the dynamic cone penetrometer (DCP), the plate-bearing test, and the falling weight deflectometer (FWD). Results indicated that the shear wave velocity predicted by the accelerated SASW system showed a favorable agreement with DCP index at both subgrades and bases. Young's modulus evaluated from the shear wave velocity also agreed roughly with the FWD modulus and subgrade reaction coefficients.

The dynamic stress response of concrete pavements subjected to moving tandem-axle loads of constant amplitude and harmonic and arbitrary variations was investigated. The concrete pavement was modeled using a plate of infinite extent on a viscoelastic foundation. Formulations were developed in the transformed field domain using ( a) a double Fourier transform in space and moving space for moving loads of constant amplitude and for the steady-state response to moving harmonic loads and ( b) a triple Fourier transform in time, space, and moving space for moving loads of arbitrary variation. The effects of viscous damping, velocity, load frequency, and phase between front- and rear-axle loads on the maximum stress and the stress distribution were analyzed. Without viscous damping, the effects of velocity and frequency, within practical ranges, on the stresses are negligible; however, with viscous damping, those effects are significant. Since materials used in various pavement layers possess damping characteristics, wheel load stresses can vary considerably because of velocity and load frequency. The increase in wheel load variations and corresponding concrete stresses can be significant if the roughness of the pavement surface is not controlled. The difference in the phase angles between front- and rear-axle loads can considerably increase the maximum stress; therefore, the use of tandem-axle loads and dynamic analyses is necessary to obtain the accurate stresses because the phase effect cannot be obtained with single-axle loads or static analyses.

Continuously reinforced concrete pavement (CRCP) performance depends primarily on early-age cracks that result from changes in temperature and drying shrinkage. Presented is the behavior of the CRCP due to the temperature change obtained by using a three-dimensional finite element model. The nonlinear effects of the bond-slip between concrete and steel and between concrete and base have been studied. Modeling for the curling effect and for the viscoelastic material characteristics also has been considered. The results from the two-dimensional and three-dimensional models have been compared to verify the possibility of using a two-dimensional model. From this study, it was found that crack width and concrete stress are dependent on the transverse steel arrangement near the edge (longitudinal joint), but they are almost independent in the interior of the slab. The tensile stress occurring at the top of the edge on the transverse steel location can be higher than that occurring at the top of the slab center. This represents the possibility of forming a transverse crack from the edge on the transverse steel location. The twodimensional model with the plane stress element gives results very close to those of the three-dimensional model, except near the edge.

The etching damage was studied on lead zirconate titanate (PZT) thin film capacitors with RuOx/Pt multi-layered electrodes. PZT films were deposited on RuOx/Pt/Ti/SiO2/Si substrates by spin coating with the sol-gel solution and etched by an inductively coupled plasma (ICP) etcher. Etching damage was systematically investigated by varying etching parameters such as coil RF power, DC bias to wafer susceptor, and chamber pressure. Quantitative analysis of etching damage was made in terms of the degree of the coercive field shift (Eshift ) in hysteresis loops. In this study, the optimization of etching process for PZT films was attempted to minimize the etching damage to the ferroelectric capacitors.

Longitudinal joint separations are often observed in concrete pavements. An innovative repair procedure was developed in this study for slot stitching in faulted or separated longitudinal joints. It involves with three stages: (1) low pressure grout to restore support under slabs that exhibited signs of pumping and faulting (2) the slot stitching method of retrofitting tie bars, to restore lateral restraint and load transfer across longitudinal joints, and (3) latex modified concrete overlay to restore proper elevation to slabs that had faulted. This paper discusses the results and lesson learned from the first implementation project on US Highway 75 near Sherman, Texas.

There are many kinds of distresses occurring in jointed concrete pavement (JCP), especially those which have exceeded or are approaching the end of their design life. Considerable effort and money have been spent to maintain the pavements by providing full-depth repair, under sealing, and patching; however, these distresses reoccur frequently. In the case of severe distresses, an overlay was constructed on the top of JCP. If the asphalt overlay was constructed on the top of deteriorated JCP, the reflective crack would occur in the overlay quickly. Continuously reinforced concrete pavement (CRCP) would provide good performance in terms of high structural capacity and efficient riding quality. CRCP bonded overlay was selected as the option for the rehabilitation of a 0.5 mile section on JCP US75 in Sherman, Texas, USA, which had been subjected to numerous rehabilitation. The pavement design and concrete mix design are introduced. In order to reduce the reflective cracking at the location of the JCP joints, geotextile were placed before the construction of the overlay. To study the effectiveness of the geotextile, twenty joints were not covered by the geotextile. The falling weight deflectometer testing was run on the pavement before and after the curing time and was analyzed and shown in this paper.

In order to investigate the behaviors of the longitudinal construction joint of continuously reinforced concrete pavement (CRCP), one set of vibrating wire strain gages (VWSG) were instrumented in a new constructed CRCP transversely, one was located at the longitudinal construction joint, six were embedded in the two adjacent concrete slabs of the joint respectively. Nine steel strain gages (SSG) were installed on three tie bars in sequence. Data logger CR1000 was used to monitor the behavior of the concrete and collect the data from the setting time. Temperature variation of the concrete was tested by the thermocouple at different depth. The result show that the opening of the joint and the movement of slab have been affected by the environmental factors and change with time. The opening of the joint at the early age resulted from the drying shrinkage of the concrete and cycled with the daily temperature change. The linear regression between the concrete movement and temperature represents the different of the effects of the temperature and drying shrinkage on joint. The analysis on SSG shows that the effects of the environment on the concrete affect the behavior of the steel. The findings in this research are beneficial for the design of the construction joint for the CRCP.