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Preston Kendall - One of the best experts on this subject based on the ideXlab platform.
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measuring hydraulic properties of geotextiles after Installation Damage
Geotextiles and Geomembranes, 2017Co-Authors: Charmaine Yi Ting Cheah, Chaminda Gallage, Les A Dawes, Preston KendallAbstract:Since geotextiles have been progressively incorporated into coastal protection structures, the influence of Installation Damage on them has been the primary concern. During Installation/construction, geotextiles are repeatedly subjected to high mechanical stresses which often exceed service stress. It is therefore vital to evaluate the mechanical and hydraulic Damage and determine the consequences of these Damages to better develop criteria for selection of suitable products. As these Damages could reduce the material's mechanical strength and hydraulic efficiency, or in the severest form of Damage, puncturing, would end the separation function. The properties investigated in this paper include the permittivity and apparent opening size (AOS) of geotextiles. Generally, the greater the drop energy of armour units applied to geotextiles, the greater the potential for Damage. Findings show that the residual permittivity could increase significantly, 45% during Installation. The preliminary design of coastal structures will be optimised as engineers and designers can better estimate the amount of Damage on geotextiles upon Installation.
D Roach - One of the best experts on this subject based on the ideXlab platform.
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Damage tolerance assessment of bonded composite doubler repairs for commercial aircraft applications
Advances in the Bonded Composite Repair of Metallic Aircraft Structure, 2002Co-Authors: D RoachAbstract:The Federal Aviation Administration has sponsored a project at its Airworthiness Assurance NDI Validation Center (AANC) to validate the use of bonded composite doublers on commercial aircraft. A specific application was chosen in order to provide a proof-of-concept driving force behind this test and analysis project. However, the data stemming from this study serves as a comprehensive evaluation of bonded composite doublers for general use. The associated documentation package provides guidance regarding the design, analysis, Installation, Damage tolerance, and nondestructive inspection of these doublers. This report describes a series of fatigue and strength tests which were conducted to study the Damage tolerance of Boron-Epoxy composite doublers. Tension-tension fatigue and ultimate strength tests attempted to grow engineered flaws in coupons with composite doublers bonded to aluminum skin. An array of design parameters, including various flaw scenarios, the effects of surface impact, and other off-design conditions, were studied. The structural tests were used to: (1) assess the potential for interply delaminations and disbonds between the aluminum and the laminate, and (2) determine the load transfer and crack mitigation capabilities of composite doublers in the presence of severe defects. A series of specimens were subjected to ultimate tension tests in order to determinemore » strength values and failure modes. It was demonstrated that even in the presence of extensive Damage in the original structure (cracks, material loss) and in spite of non-optimum Installations (adhesive disbonds), the composite doubler allowed the structure to survive more than 144,000 cycles of fatigue loading. Installation flaws in the composite laminate did not propagate over 216,000 fatigue cycles. Furthermore, the added impediments of impact--severe enough to deform the parent aluminum skin--and hot-wet exposure did not effect the doubler`s performance. Since the tests were conducting using extreme combinations of flaw scenarios (sizes and collocation) and excessive fatigue load spectrums, the performance parameters were arrived at in a conservative manner.« less
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Damage tolerance assessment of bonded composite doubler repairs for commercial aircraft applications
Other Information: PBD: Aug 1998, 1998Co-Authors: D RoachAbstract:The Federal Aviation Administration has sponsored a project at its Airworthiness Assurance NDI Validation Center (AANC) to validate the use of bonded composite doublers on commercial aircraft. A specific application was chosen in order to provide a proof-of-concept driving force behind this test and analysis project. However, the data stemming from this study serves as a comprehensive evaluation of bonded composite doublers for general use. The associated documentation package provides guidance regarding the design, analysis, Installation, Damage tolerance, and nondestructive inspection of these doublers. This report describes a series of fatigue and strength tests which were conducted to study the Damage tolerance of Boron-Epoxy composite doublers. Tension-tension fatigue and ultimate strength tests attempted to grow engineered flaws in coupons with composite doublers bonded to aluminum skin. An array of design parameters, including various flaw scenarios, the effects of surface impact, and other off-design conditions, were studied. The structural tests were used to: (1) assess the potential for interply delaminations and disbonds between the aluminum and the laminate, and (2) determine the load transfer and crack mitigation capabilities of composite doublers in the presence of severe defects. A series of specimens were subjected to ultimate tension tests in order to determine strength values and failure modes. It was demonstrated that even in the presence of extensive Damage in the original structure (cracks, material loss) and in spite of non-optimum Installations (adhesive disbonds), the composite doubler allowed the structure to survive more than 144,000 cycles of fatigue loading. Installation flaws in the composite laminate did not propagate over 216,000 fatigue cycles. Furthermore, the added impediments of impact--severe enough to deform the parent aluminum skin--and hot-wet exposure did not effect the doubler`s performance. Since the tests were conducting using extreme combinations of flaw scenarios (sizes and collocation) and excessive fatigue load spectrums, the performance parameters were arrived at in a conservative manner.
Ivo Sterba - One of the best experts on this subject based on the ideXlab platform.
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strength reduction factors due to Installation Damage of reinforcing geosynthetics
Geotextiles and Geomembranes, 2005Co-Authors: Rudolf Hufenus, Rudolf Ruegger, Daniel Flum, Ivo SterbaAbstract:Abstract The Installation may represent the hardest stress on a geosynthetic during its service life. Full-scale field Installation tests have been performed on 38 different geotextiles and geogrids. The findings have been used to determine the corresponding reduction factor which must be taken into account to assess the long-term tensile strength of reinforcing geosynthetics. Based on the present study and full-scale field Installation tests presented elsewhere, a matrix to assess the survivability of geosynthetics is proposed. In addition, parts of the geosynthetics have been submitted to a laboratory simulation of the Damage during Installation, which showed a reasonable correlation to the results of the field test.
Richard J Bathurst - One of the best experts on this subject based on the ideXlab platform.
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reliability based analysis of combined Installation Damage and creep for the tensile rupture limit state of geogrid reinforcement in japan
Soils and Foundations, 2015Co-Authors: Richard J Bathurst, Yoshihisa MiyataAbstract:Abstract The paper uses statistical data for the prediction of Installation Damage and creep-reduced strength collected by the writers in earlier investigations to estimate the probability of failure of tensile rupture of geogrid reinforcement products. The original data were compiled from Public Works Research Center (PWRC) geogrid product certification reports issued in Japan. The paper develops the formulation for the ultimate tensile rupture limit state equation and links it to allowable stress design (ASD) practice currently used in Japan and reliability theory-based load and resistance factor design (LRFD) used in North America. The paper shows that variability in the prediction of creep-reduced strength is largely captured by the inherent variability in strength of the materials at the time of manufacture. Combined variability due to creep and Installation Damage is typically dominated by variability in the prediction of strength after Installation Damage. Where this is not the case the combined variability is very low (less than 5%). The variability in the estimate of strength reduction due to combined Installation Damage and creep is demonstrated to be less than the variability in the estimates of reinforcement load even for the case of a load model judged to give relatively accurate load predictions. For poorer load models the under-prediction of reinforcement loads provides an additional margin of safety. The paper provides a framework for future rigorous reliability theory-based LRFD calibration for the ultimate tensile rupture of geogrid reinforcement in reinforced soil applications in Japan and elsewhere, and provides the necessary bias statistics for the resistance side in the ultimate tensile rupture limit state equation.
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combined allowable strength reduction factor for geosynthetic creep and Installation Damage
Geosynthetics International, 1996Co-Authors: Tony M Allen, Richard J BathurstAbstract:The current practice to determine the combined geosynthetic strength reduction due to Installation Damage and creep is to multiply the individual strength reduction factors for Damage and creep together. However, it is difficult to know if this procedure results in conservative design, nonconservative design, or is sufficiently accurate for practical purposes. The effect of synergism on the combined effect of polymeric creep and Installation Damage is explored in the paper by reviewing published and unpublished constant load (creep) data for both unDamaged and Installation-Damaged geosynthetic specimens. A methodology is developed that uses data from both constant load (creep) tests and index tests to reconstruct Installation-Damaged isochronous creep curves. Based on the limited data available and the interpretation of reconstructed isochronous curves, it is shown that multiplication of creep reduction and Installation Damage factors may be conservative and hence results in errors on the safe side for de...
Charmaine Yi Ting Cheah - One of the best experts on this subject based on the ideXlab platform.
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measuring hydraulic properties of geotextiles after Installation Damage
Geotextiles and Geomembranes, 2017Co-Authors: Charmaine Yi Ting Cheah, Chaminda Gallage, Les A Dawes, Preston KendallAbstract:Since geotextiles have been progressively incorporated into coastal protection structures, the influence of Installation Damage on them has been the primary concern. During Installation/construction, geotextiles are repeatedly subjected to high mechanical stresses which often exceed service stress. It is therefore vital to evaluate the mechanical and hydraulic Damage and determine the consequences of these Damages to better develop criteria for selection of suitable products. As these Damages could reduce the material's mechanical strength and hydraulic efficiency, or in the severest form of Damage, puncturing, would end the separation function. The properties investigated in this paper include the permittivity and apparent opening size (AOS) of geotextiles. Generally, the greater the drop energy of armour units applied to geotextiles, the greater the potential for Damage. Findings show that the residual permittivity could increase significantly, 45% during Installation. The preliminary design of coastal structures will be optimised as engineers and designers can better estimate the amount of Damage on geotextiles upon Installation.