Structural Overlay Strategies for Jointed Concrete Pavements. Volume IV: Guidelines for the Selection of Rehabilitation Alternatives

DTFH61-86-C-00079A major field study and evaluation has been conducted into the effectiveness of three structural overlay types for portland cement concrete (PCC) pavements. These include sawing and sealing asphalt concrete (AC) overlays of PCC pavements, cracking and seating PCC pavements prior to AC overlay, and constructing a thin bonded PCC overlay on top of the existing PCC pavement. Condition surveys, deflection testing, and roughness measurements were performed on a total of 55 sections. The performance of these sections was evaluated and the effectiveness of each overlay type analyzed. Based on the field data, guidelines were developed for the use of these structural overlays. This volume provides detailed guidelines and case studies prepared specifically for the practicing engineer as an aid in the evaluation and rehabilitation of jointed concrete pavements. Feasibility guidelines are given for restoration, resurfacing, and reconstruction alternatives in terms of constructability, future life and life-cycle costs. New prediction models are developed for bonded PCC overlays, sawing and sealing and AC overlay, and cracking and seating and AC overlay. The EXPEAR program was extensively modified to include the above rehabilitation alternatives and improved predictive models and to provide for much easier usage by the practicing engineer for evaluation and rehabilitation. Detailed rehabilitation case studies are presented that will be of interest to the practicing engineer

Structural Overlay Strategies for Jointed Concrete Pavements. Volume VI: Appendix A, User's Manual for the EXPEAR Computer Program

DTFH61-86-C-00079A major field study and evaluation has been conducted into the effectiveness of three structural overlay types for portland cement concrete (PCC) pavements. These include sawing and sealing asphalt concrete (AC) overlays of PCC pavements, cracking and seating PCC pavements prior to AC overlay, and constructing a thin bonded PCC overlay on top of the existing PCC pavement. Condition surveys, deflection testing, and roughness measurements were performed on a total of 55 sections. The performance of these sections was evaluated and the effectiveness of each overlay type analyzed. Based on the field data, guidelines were developed for the use of structural overlays. This volume provides a users guide to the EXPEAR computerized system to assist practicing engineers in evaluating concrete highway pavements, in developing feasible rehabilitation alternatives, and in predicting the performance and cost-effectiveness of the alternatives. EXPEAR is intended for use by State highway engineers in project-level rehabilitation planning and design for conventional concrete pavements (JRCP, JPCP, and CRCP). EXPEAR uses information about the pavement to guide the engineer through evaluation of a pavement's present condition and development of one or more feasible rehabilitation strategies. A computer program has been developed for each of the three pavement types addressed. The EXPEAR version 1.4 program operates on any IBM-compatible personal computer. Extensive revisions were made in EXPEAR 1.4 to improve the user-friendliness of the program and its capabilities

Performance of Concrete Pavements, Volume III: Improving Concrete Pavement Performance

DTFH61-91-C-00053With the goal of improving future concrete pavement design and construction practices, this project evaluated the performance of 303 inservice concrete pavement sections located throughout North America. An extensive field testing program, consisting of pavement condition surveys, drainage surveys, falling weight deflectometer (FWD) testing, coring/boring operations, and roughness testing, was conducted in order to collect the information needed for analysis. Because many of these pavement sections are part of State-level studies on concrete pavements, a range of design variables (e.g., load transfer, slab thickness, joint spacing, drainage) thought to affect concrete pavement performance are present. Over one-third of the sections was evaluated under a preceding Federal Highway Administration study, meaning that 5-year performance trends are available for some of the sections. Additional pavement performance data are also available for 96 European concrete pavement sections and for 21 Chilean concrete pavement sections. The average age and average cumulative equivalent single axle loads (ESALs) for the North American sections are 16 years and 7.1 million, respectively, compared to 21 years and 21.8 million for the European sections and 9 years and 5.9 million for the Chilean sections. This volume presents pavement performance prediction models that were developed from the data collected under this study. Prediction models are presented for transverse joint faulting (doweled and nondoweled), transverse cracking [jointed plain concrete pavement (JPCP) and jointed reinforced concrete pavement (JRCP)], transverse joint spalling (JPCP and JRCP), pavement serviceability (JPCP and JRCP), and pavement roughness (JPCP only). Based on the results of the models and on the results of the field evaluation findings, guidelines for the improved design of concrete pavements are presented

Performance of Concrete Pavements, Volume II: Evaluation of Inservice Concrete Pavements

DTFH61-91-C-00053With the goal of improving future concrete pavement design and construction practices, this project evaluated the performance of 303 inservice concrete pavement sections located throughout North America. An extensive field testing program, consisting of pavement condition surveys, drainage surveys, falling weight deflectometer (FWD) testing, coring/boring operations, and roughness testing, was conducted in order to collect the information needed for analysis. Because many of these pavement sections are part of State-level studies on concrete pavements, a range of design variables (e.g., load transfer, slab thickness, joint spacing, drainage) thought to affect concrete pavement performance are present. Over one-third of the sections was evaluated under a preceding Federal Highway Administration study, meaning that 5-year performance trends are available for some of the sections. Additional pavement performance data are also available for 96 European concrete pavement sections and for 21 Chilean concrete pavement sections. The average age and average cumulative equivalent single axle loads (ESALs) for the North American sections are 16 years and 7.1 million, respectively, compared to 21 years and 21.8 million for the European sections and 9 years and 5.9 million for the Chilean sections. This volume examines the performance of the North American concrete pavement sections included in the study. This examination primarily consists of an evaluation of the effect of concrete pavement design features on concrete pavement performance. Design features investigated include slab thickness, joint spacing, joint orientation, load transfer, joint sealant, base type, drainage, shoulder type, reinforcement, and pavement type. The results of an examination of the backcalculation results are also presented, as are the significant findings of an evaluation conducted on the performance of European and Chilean concrete pavements

Locomotor adaptability in persons with unilateral transtibial amputation

Background Locomotor adaptation enables walkers to modify strategies when faced with challenging walking conditions. While a variety of neurological injuries can impair locomotor adaptability, the effect of a lower extremity amputation on adaptability is poorly understood. Objective Determine if locomotor adaptability is impaired in persons with unilateral transtibial amputation (TTA). Methods The locomotor adaptability of 10 persons with a TTA and 8 persons without an amputation was tested while walking on a split-belt treadmill with the parallel belts running at the same (tied) or different (split) speeds. In the split condition, participants walked for 15 minutes with the respective belts moving at 0.5 m/s and 1.5 m/s. Temporal spatial symmetry measures were used to evaluate reactive accommodations to the perturbation, and the adaptive/de-adaptive response. Results Persons with TTA and the reference group of persons without amputation both demonstrated highly symmetric walking at baseline. During the split adaptation and tied post-adaptation walking both groups responded with the expected reactive accommodations. Likewise, adaptive and de-adaptive responses were observed. The magnitude and rate of change in the adaptive and de-adaptive responses were similar for persons with TTA and those without an amputation. Furthermore, adaptability was no different based on belt assignment for the prosthetic limb during split adaptation walking. Conclusions Reactive changes and locomotor adaptation in response to a challenging and novel walking condition were similar in persons with TTA to those without an amputation. Results suggest persons with TTA have the capacity to modify locomotor strategies to meet the demands of most walking conditions despite challenges imposed by an amputation and use of a prosthetic limb

Performance of Concrete Pavements, Volume I: Field Investigation

DTFH61-91-C-00053With the goal of improving future concrete pavement design and construction practices, this project evaluated the performance of 303 inservice concrete pavement sections located throughout North America. An extensive field testing program, consisting of pavement condition surveys, drainage surveys, falling weight deflectometer (FWD) testing, coring/boring operations, and roughness testing, was conducted in order to collect the information needed for analysis. Because many of these pavement sections are part of State-level studies on concrete pavements, a range of design variables (e.g., load transfer, slab thickness, joint spacing, drainage) thought to affect concrete pavement performance are present. Over one-third of the sections was evaluated under a preceding Federal Highway Administration study, meaning that 5-year performance trends are available for some of the sections. Additional pavement performance data are also available for 96 European concrete pavement sections and for 21 Chilean Concrete pavement sections. The average age and average cumulative equivalent single axle loads (ESALs) for the North American sections are 16 years and 7.1 million, respectively, compared to 21 years and 21.8 million for the European sections and 9 years and 5.9 million for the Chilean sections. This volume describes the field data collection activities that were conducted under the study and also summarizes the individual performance of the 303 concrete pavement sections evaluated. Pertinent design and construction data are given for each project and key performance data are presented. Where available, 5-year performance trends are also summarized

Rehabilitation of Concrete Pavements, Volume III: Concrete Pavement Evaluation and Rehabilitation System

DTFH61-85-C-00004Extensive field, laboratory and analytical studies were conducted into the evaluation and rehabilitation of concrete pavements. Field studies included over 350 rehabilitated pavement sections throughout the U.S., and the construction of two field experiments. A laboratory study was conducted on anchoring dowels in full-depth repairs. Analyses of field and laboratory data identified performance characteristics, improved design and construction procedures, and provided deterioration models for rehabilitated pavements. A concrete pavement advisory system was developed to assist engineers in project level evaluation and rehabilitation. The repair techniques in Volume I include full-depth repair, partial-depth repair, load transfer restoration, edge support and diamond grinding. Overlay techniques in Volume II include bonded concrete, unbonded concrete and crack and seat with an asphalt concrete overlay. This volume, Volume III, presents a comprehensive concrete pavement evaluation and rehabilitation advisory system for jointed plain, jointed reinforced and continuously reinforced concrete pavements. Volume IV contains a description of the data collection procedures, original pavement and rehabilitation design factors, extent of the database, description of database variables, and documentation of the laboratory dowel anchoring experiment

Between-Monitor Differences in Step Counts Are Related to Body Size: Implications for Objective Physical Activity Measurement

The quantification of the relationships between walking and health requires that walking is measured accurately. We correlated different measures of step accumulation to body size, overall physical activity level, and glucose regulation.Participants were 25 men and 25 women American Indians without diabetes (Age: 20-34 years) in Phoenix, Arizona, USA. We assessed steps/day during 7 days of free living, simultaneously with three different monitors (Accusplit-AX120, MTI-ActiGraph, and Dynastream-AMP). We assessed total physical activity during free-living with doubly labeled water combined with resting metabolic rate measured by expired gas indirect calorimetry. Glucose tolerance was determined during an oral glucose tolerance test.Based on observed counts in the laboratory, the AMP was the most accurate device, followed by the MTI and the AX120, respectively. The estimated energy cost of 1000 steps per day was lower in the AX120 than the MTI or AMP. The correlation between AX120-assessed steps/day and waist circumference was significantly higher than the correlation between AMP steps and waist circumference. The difference in steps per day between the AX120 and both the AMP and the MTI were significantly related to waist circumference.Between-monitor differences in step counts influence the observed relationship between walking and obesity-related traits

Feasibility of a walking virtual reality system for rehabilitation: objective and subjective parameters

[EN] Background: Even though virtual reality (VR) is increasingly used in rehabilitation, the implementation of walking navigation in VR still poses a technological challenge for current motion tracking systems. Different metaphors simulate locomotion without involving real gait kinematics, which can affect presence, orientation, spatial memory and cognition, and even performance. All these factors can dissuade their use in rehabilitation. We hypothesize that a marker-based head tracking solution would allow walking in VR with high sense of presence and without causing sickness. The objectives of this study were to determine the accuracy, the jitter, and the lag of the tracking system and its elicited sickness and presence in comparison of a CAVE system. Methods: The accuracy and the jitter around the working area at three different heights and the lag of the head tracking system were analyzed. In addition, 47 healthy subjects completed a search task that involved navigation in the walking VR system and in the CAVE system. Navigation was enabled by natural locomotion in the walking VR system and through a specific device in the CAVE system. An HMD was used as display in the walking VR system. After interacting with each system, subjects rated their sickness in a seven-point scale and their presence in the Slater-Usoh-Steed Questionnaire and a modified version of the Presence Questionnaire. Results: Better performance was registered at higher heights, where accuracy was less than 0.6 cm and the jitter was about 6 mm. The lag of the system was 120 ms. Participants reported that both systems caused similar low levels of sickness (about 2.4 over 7). However, ratings showed that the walking VR system elicited higher sense of presence than the CAVE system in both the Slater-Usoh-Steed Questionnaire (17.6 +/- 0.3 vs 14.6 +/- 0.6 over 21, respectively) and the modified Presence Questionnaire (107.4 +/- 2.0 vs 93.5 +/- 3.2 over 147, respectively). Conclusions: The marker-based solution provided accurate, robust, and fast head tracking to allow navigation in the VR system by walking without causing relevant sickness and promoting higher sense of presence than CAVE systems, thus enabling natural walking in full-scale environments, which can enhance the ecological validity of VR-based rehabilitation applications.The authors wish to thank the staff of LabHuman for their support in this project, especially José Miguel Martínez and José Roda for their assistance. This study was funded in part by Ministerio de Economia y Competitividad of Spain (Project NeuroVR, TIN2013-44741-R and Project REACT, TIN2014-61975-EXP), by Ministerio de Educacion y Ciencia of Spain (Project Consolider-C, SEJ2006-14301/PSIC), and by Universitat Politecnica de Valencia (Grant PAID-10-14).Borrego, A.; Latorre Grau, J.; Llorens Rodríguez, R.; Alcañiz Raya, ML.; Noé, E. (2016). Feasibility of a walking virtual reality system for rehabilitation: objective and subjective parameters. Journal of NeuroEngineering and Rehabilitation. 13:1-9. https://doi.org/10.1186/s12984-016-0174-1S1913Lee KM. Presence. Explicated Communication Theory. 2004;14(1):27–50.Riva G. Is presence a technology issue? Some insights from cognitive sciences. Virtual Reality. 2009;13(3):159–69.Banos RM, et al. Immersion and emotion: their impact on the sense of presence. Cyberpsychol Behav. 2004;7(6):734–41.Llorens R, et al. 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Automatic Railway Signal.

Patent for a new and improved railroad signal. This design, "[w]hen the wheels of a passing train come in contact with the spring and bent end of the lever . . . said end is lowered or depressed, causing the movement in the same direction of the outer end of said lever, which, through the agency of the wire, will cause the ringing or sounding of the gong or bell as the wheels . . . come in contact with the end of the lever. . . .[A]fter the wheels of the last car of a train have passed the point where the lever is located, said lever will be returned to its normal position by means of the coil-spring" (lines 57-71)