Fiber-Optic Strain-Based Deflection and Twist Sensing for a High-Aspect-Ratio Swept Wing

Designs of aircraft structures have been moving toward leaner, lightweight designs for increased fuel efficiency. The Passive Aeroelastic Tailored (PAT) wing developed under the NASA Advanced Air Transport Technology (AATT) project is an example of a swept-wing design with high aspect ratio that incorporates lightweight highly-flexible tailored composite construction. The passive aeroelastic tailored structural design has explored the design space to enable aeroelastically tailored wing structures to increase aspect ratios (from 9 to 14) and ultimately reduce weight by 20 percent to 25 percent without impacting aeroelastic performance. To further study the aeroelastic performance of such a wing, the NASA Armstrong Flight Research Center (AFRC) (Edwards, California) has developed efficient real-time structural algorithms that are used in conjunction with a fiber-optic measurement system for lightweight vehicle applications. The AFRC Fiber Optic Sensing System (FOSS) provides up to 8,000 distributed surface strain measurements at one-half-inch increments and can be used to estimate a variety of structural parameters such as shape and load. This report discusses the implementation of strain-based displacement and twist-sensing techniques applied to the PAT wing test article tested at the NASA AFRC Flight Loads Laboratory. Empirical FOSS strain data are collected under varying loading conditions. Strain data are processed with the displacement and twist-sensing algorithms and independently verified by comparison to conventional ground-based instrumentation

Evaluation of Precut Transverse Cracks for an Asphalt Concrete Pavement in Interior Alaska (Moose Creek –Richardson Highway)

Road-width thermal cracks (major transverse cracks) are perhaps the most noticeable form of crack-related damage on AC pavements throughout colder areas of Alaska. The main objective of this study is to recommend design strategies and construction practices aimed at controlling thermal cracking in AC pavements. In this report, literature review summarizes selected items of the engineering literature directly relevant to precutting of pavement-type structures and control of thermal cracking in general. Crack surveys and data collection were conducted at the test sections in an AKDOT&PF resurfacing project to compare various precut strategies (variations of cut spacing and depth), with the locations of natural major transverse cracks both before and after construction. Laboratory testing and numerical analysis were also presented to provide basic data about the physical properties of the AC and help explain some of the observed characteristics associated with natural thermal cracking. 17.I. INTRODUCTION ............................................................................................ 1 PROBLEM STATEMENT ..................................................................................... 1 BACKGROUND .................................................................................................... 2 OBJECTIVES ......................................................................................................... 4 Research Approach .............................................................................................. 4 II. LITERATURE REVIEW ................................................................................. 7 INTRODUCTION TO THERMAL CRACKING (McHattie et al. 2013) ............. 7 TECHNOLOGY REGARDING PRECUTTING OF TRANSVERSE CRACKS ............................................................................................................. 10 Sawing Joints to Control Cracking in Flexible Pavements (Morchinek 1974).10 Sawing and Sealing Joints in Bituminous Pavements to Control Cracking (Janisch 1996) .................................................................................................. 12 III. DESCRIPTION OF RESEARCH AREA ...................................................... 15 CONSTRUCTION PROJECT / RESEARCH AREA LOCATION ..................... 15 RESEARCH LAYOUT / PRECUT DESIGN/EXECUTION .............................. 17 IV. MATERIALS PROPERTIES ........................................................................ 19 ASPHALT CONCRETE SPECIFICATIONS & MARSHALL MIX DESIGN ..20 DATA FROM AKDOT&PF CONSTRUCTION ACCEPTANCE TESTS ....... 21 DESCRIPTION OF PAVEMENT CORES & LABORATORY RESULTS ....... 23 V. CRACK SURVEYS & DESCRIPTIONS ...................................................... 25 CRACK SURVEYS .............................................................................................. 25 Data Collection and Availability ....................................................................... 25 Analysis of Crack Survey Data ......................................................................... 25 CRACK DESCRIPTIONS .................................................................................... 29 VI. NUMERICAL ANALYSES .......................................................................... 35 SIMULATION CONFIGURATIONS AND INPUTS ......................................... 35 FEM Model Configurations .............................................................................. 35 Simulation Inputs............................................................................................... 37 SIMULATION RESULTS AND ANALYSIS ..................................................... 38 VII. CONCLUSIONS & RECOMMENDATIONS .............................................. 42 CONCLUSIONS ................................................................................................... 42 IMPLEMENTATION RECOMMENDATIONS ................................................. 42 RECOMMENDATIONS FOR CONTINUING RESEARCH ............................. 43 APPENDIX A: EXAMPLES OF CRACK SURVEY SHEETS ............................. 44 APPENDIX B: RAW CRACK SURVEY DATA ................................................... 47 APPENDIX C: CRACK MAP BASED ON 2014 FIELD DATA ........................... 57 REFERENCES ......................................................................................................... 6

An analytical and experimental assessment of flexible road ironwork support structures

This paper describes work undertaken to investigate the mechanical performance of road ironwork installations in highways, concentrating on the chamber construction. The principal aim was to provide the background research which would allow improved designs to be developed to reduce the incidence of failures through improvements to the structural continuity between the installation and the surrounding pavement. In doing this, recycled polymeric construction materials (Jig Brix) were studied with a view to including them in future designs and specifications. This paper concentrates on the Finite Element (FE) analysis of traditional (masonry) and flexible road ironwork structures incorporating Jig Brix. The global and local buckling capacity of the Jig Brix elements was investigated and results compared well with laboratory measurements. FE models have also been developed for full-scale traditional (masonry) and flexible installations in a surrounding flexible (asphalt) pavement structure. Predictions of response to wheel loading were compared with full-scale laboratory measurements. Good agreement was achieved with the traditional (masonry) construction but poorer agreement for the flexible construction. Predictions from the FE model indicated that the use of flexible elements significantly reduces the tensile horizontal strain on the surface of the surrounding asphaltic material which is likely to reduce the incidence of surface cracking

Sustainable Building Materials of the Future: Architectural Forms and Structural Design

This research investigates the use of non-rigid formwork and the techniques aiming to create more efficient concrete forms. During casting, concrete takes the shape of its formwork; traditionally, these formworks are made of rigid materials like steel or wood. The results are prismatic members, which are not optimized for material usage but only for simplicity in construction. Most of the research in the area focuses on improving the constituent materials, while the formworks have remained unchanged throughout the years. By using the approach described in this study, optimized shapes are achieved. These geometries can save up to 30% of the material while maintaining the same strength. In this study, we investigated the structural capacity of reinforced concrete members built with this technique along with the necessary solutions to perform better casts. Formworks were improved with each cast until a consistent method of creating the desired beam shape was achieved. Using both software are standard laboratory tests, the data were collected and analyzed. The results show that flexible forms can create more environmentally friendly concrete structures. Our research also opened up new questions. How can the processes be more streamlined, and are there real-world applications? This research investigates the use of non-rigid formwork and the techniques aiming to create more efficient concrete forms. During casting, concrete takes the shape of its formwork; traditionally, these formworks are made of rigid materials like steel or wood. The results are prismatic members, which are not optimized for material usage but only for simplicity in construction. Most of the research in the area focuses on improving the constituent materials, while the formworks have remained unchanged throughout the years. By using the approach described in this study, optimized shapes are achieved. These geometries can save up to 30% of the material while maintaining the same strength. In this study, we investigated the structural capacity of reinforced concrete members built with this technique along with the necessarily solutions to perform better casts. Formworks were improved with each cast until a consistent method of creating the desired beam shape was achieved. Using both software are standard laboratory tests, the data were collected and analyzed. The results show that flexible forms can create more environmentally friendly concrete structures. Our research also opened up new questions. How can the processes be more streamlined, and are there real-world applications

Numerical investigation into the failure of a micropile retaining wall

The paper presents a numerical investigation on the failure of a micropile wall that collapsed while excavating the adjacent ground. The main objectives are: to estimate the strength parameters of the ground; to perform a sensitivity analysis on the back slope height and to obtain the shape and position of the failure surface. Because of uncertainty of the original strength parameters, a simplified backanalysis using a range of cohesion/friction pairs has been used to estimate the most realistic strength parameters. The analysis shows that failure occurred because overestimation of strength and underestimation of loads.Peer ReviewedPostprint (author's final draft

Technology for large space systems: A special bibliography with indexes (supplement 04)

This bibliography lists 259 reports, articles, and other documents introduced into the NASA scientific and technical information system between July 1, 1980 and December 31, 1980. Its purpose is to provide information to the researcher, manager, and designer in technology development and mission design in the area of the Large Space Systems Technology Program. Subject matter is grouped according to systems, interactive analysis and design. Structural concepts, control systems, electronics, advanced materials, assembly concepts, propulsion, solar power satellite systems, and flight experiments

Technology for large space systems: A special bibliography with indexes (supplement 03)

A bibliography containing 217 abstracts addressing the technology for large space systems is presented. State of the art and advanced concepts concerning interactive analysis and design, structural concepts, control systems, electronics, advanced materials, assembly concepts, propulsion, solar power satellite systems, and flight experiments are represented