Pull-off bond strength of novel wide rounded ends fiber and impact of fiber stretching on fiber/matrix frictional-slip bond strength

This paper presents a study about fiber slippage behavior under direct pull-out and assessment of fiber/matrix pull-off bond strength. This study was prepared through theoretical calculations validated by experimental tests. Theoretically, the study shows a general solution for the fiber-slip mechanism in a general matrix using a new frictional-shear-lag model and an analytical model for pull-off bond strength. Experimentally, pull-out tests were conducted for selected types of single fiber in micro-level (glass, carbon, and short-steel fiber); and macro-level (straight steel fiber). The results showed significant improvements in the pull-off bond strength using novel shape of fiber with wide rounded ends-WESF. The pull-off bond strength in normal-weight concrete was found lower than in lightweight concrete, and the matrix with higher compressive strength improves the pull-off bond strength. Also, the steel fiber showed higher pull-off bond strength compared to glass and carbon fiber; whereas the efficiency of short-steel fiber was higher than the long one. All types of fiber showed that the higher aspect ratio reduces the pull-off bond strength. Using the novel-WESF, the performance of fiber-slip improved 52.65% in normal-weight concrete. Moreover, the fiber-slip performance improved 61.79% in sand-lightweight concrete, and 70.20% in all other types of light-weight concrete

Crop Updates 2005 - Cereals

This session covers thirty six papers from different authors: WHEAT AGRONOMY 1. Optimum sowing time of new wheat varieties in Western Australia, Darshan Sharma, Brenda Shackley, Mohammad Amjad, Christine M. Zaicou-Kunesch and Wal Anderson, Department of Agriculture 2. Wheat varieties updated in ‘Flowering Calculator’: A model predicting flowering time, B. Shackley, D. Tennant, D. Sharma and C.M. Zaicou-Kunesch, Department of Agriculture 3. Plant populations for wheat varieties, Christine M. Zaicou-Kunesch, Wal Anderson, Darshan Sharma, Brenda Shackley and Mohammad Amjad, Department of Agriculture 4. New wheat cultivars response to fertiliser nitrogen in four major agricultural regions of Western Australia, Mohammad Amjad, Wal Anderson, Brenda Shackley, Darshan Sharma and Christine Zaicou-Kunesch, Department of Agriculture 5. Agronomic package for EGA Eagle Rock, Steve Penny, Department of Agriculture 6. Field evaluation of eastern and western wheats in large-scale farmer’s trials, Mohammad Amjad, Ben Curtis and Veronika Reck, Department of Agriculture 7. New wheat varieties for a changing environment, Richard Richards, CSIRO Plant Industry; Canberra 8. Farmers can profitably minimise exposure to frost! Garren Knell, Steve Curtin and David Sermon, ConsultAg 9. National Variety Trials, Alan Bedggood, Australian Crops Accreditation System; Horsham 10. Preharvest-sprouting tolerance of wheat in the field, T.B. Biddulph1, T.L. Setter2, J.A. Plummer1 and D.J. Mares3; 1Plant Biology; FNAS, University of Western Australia; 2Department of Agriculture, 3School of Agriculture and Wine, University of Adelaide 11. Waterlogging induces high concentration of Mn and Al in wheat genotypes in acidic soils, H. Khabaz-Saberi, T. Setter, I. Waters and G. McDonald, Department of Agriculture 12. Agronomic responses of new wheat varieties in the Northern Agricultural Region, Christine M. Zaicou-Kunesch and Wal Anderson, Department of Agriculture 13. Agronomic responses of new wheat varieties in the Central Agricultural Region of WA, Darshan Sharma, Steve Penny and Wal Anderson, Department of Agriculture 14. EGA Eagle Rock tolerance to metribuzin and its mixtures, Harmohinder Dhammu, David Nicholson and Chris Roberts, Department of Agriculture 15. Herbicide tolerance of new bread wheats, Harmohinder Dhammu1 and David Nicholson2, Department of Agriculture NUTRITION 16. The impact of fertiliser placement, timing and rates on nitrogen-use efficiency, Stephen Loss, CSBP Ltd 17. Cereals deficient in potassium are most susceptible to some leaf diseases, Ross Brennan and Kith Jayasena, Department of Agriculture 18. Responses of cereal yields to potassium fertiliser type, placement and timing, Eddy Pol, CSBP Limited 19. Sulphate of Potash, the potash of choice at seeding, Simon Teakle, United Farmers Co-operative 20. Essential disease management for successful barley production, K. Jayasena, R. Loughman, C. Beard, B. Paynter, K. Tanaka, G. Poulish and A. Smith, Department of Agriculture 21. Genotypic differences in potassium efficiency of wheat, Paul Damon and Zed Rengel, Faculty of Natural and Agricultural Sciences, University of Western Australia 22. Genotypic differences in potassium efficiency of barley, Paul Damon and Zed Rengel, Faculty of Natural and Agricultural Sciences, University of Western Australia 23. Investigating timing of nitrogen application in wheat, Darshan Sharma and Lionel Martin, Department of Agriculture, and Muresk Institute of Agriculture, Curtin University of Technology 24. Nutrient timing requirements for increased crop yields in the high rainfall cropping zone, Narelle Hill, Ron McTaggart, Dr Wal Anderson and Ray Tugwell, Department of Agriculture DISEASES 25. Integrate strategies to manage stripe rust risk, Geoff Thomas, Robert Loughman, Ciara Beard, Kith Jayasena and Manisha Shankar, Department of Agriculture 26. Effect of primary inoculum level of stripe rust on variety response in wheat, Manisha Shankar, John Majewski and Robert Loughman, Department of Agriculture 27. Disease resistance update for wheat varieties in WA, M. Shankar, J.M. Majewski, D. Foster, H. Golzar, J. Piotrowski and R. Loughman, Department of Agriculture 28. Big droplets for wheat fungicides, Rob Grima, Agronomist, Elders 29. On farm research to investigate fungicide applications to minimise leaf disease impacts in wheat, Jeff Russell and Angie Roe, Department of Agriculture, and Farm Focus Consultants PESTS 30. Rotations for nematode management, Vivien A. Vanstone, Sean J. Kelly, Helen F. Hunter and Mena C. Gilchrist, Department of Agriculture 31. Investigation into the adaqyacy of sealed farm silos in Western Australia to control phosphine-resistant Rhyzopertha dominica, C.R. Newman, Department of Agriculture 32.Insect contamination of cereal grain at harvest, Svetlana Micic and Phil Michael, Department of Agriculture 33. Phosure – Extending the life of phosphine, Gabrielle Coupland and Ern Kostas, Co-operative Bulk Handling SOIL 34. Optimum combinations of ripping depth and tine spacing for increasing wheat yield, Mohammed Hamza and Wal Anderson, Department of Agriculture 35. Hardpan penetration ability of wheat roots, Tina Botwright Acuña and Len Wade, School of Plant Biology, University of Western Australia MARKETS 36. Latin America: An emerging agricultural powerhouse, Ingrid Richardson, Food and Agribusiness Research, Rabobank; Sydne

Assessment of frictional-bond strength at the interface of single SSF in cementitious composite and prediction of accompanying pressure of surrounding matrix

This paper deals with the study of bond in fiber-reinforced concrete composites and the effect of fiber/concrete interfacial friction on the fiber bond capacity. The paper presents the results of an experimental campaign including direct pull-out test of straight steel fiber-SSF embedded in concrete matrix, aimed at investigating the effect of some parameters, such as bonded length, yielding strength of steel fiber, fiber/concrete roughness, surrounding pressure of concrete matrix, and Poisson's ratio of concrete. Two analytical models based on the experimental results were proposed. Groups of single fiber embedded in concrete were prepared using different values of bonded length. The results showed that the frictional-bond strength, during fiber-slip stage, can be considered as constant despite changing the fiber embedment length. Furthermore, the SSF/concrete system can be considered as an elastic system, whereas the stress-displacement relation is semilinear. Finally, the results showed good improvements in the efficiency of frictional-bond strength when using fresh concrete with higher self-compacting, greater roughness at the interface of SSF/hardened-concrete, and fiber with lower yield strength. While no significant effect of Poisson's ratio on the frictional-bond strength was noticed

Construction and design requirements of green buildings' roofs in Saudi Arabia depending on thermal conductivity principle

Green buildings aim to promote the positive role of buildings in the community service, and to reduce the negative impact of buildings on the natural environment, as well as to support the national economy. This research showed the inefficiency of conventional roofs, especially those of residential buildings, against heat transfer at different geographical zones of KSA - Kingdom of Saudi Arabia. Thermal analysis of different computational models also led to improvements reached to 89% on roof performance regarding its thermal insulation. These improvements were obtained by converting those conventional concrete roofs into green roofs. In this study, details of several scenarios were shown, and analytical calculations were conducted for different types of green roofs compared to conventional roofs in two main cases, air absence and air presence inside it. According to these scenarios, the impact of vegetation cover on the building roof was determined using thermal models of roof slab in two sub-cases of vegetation cover, one when using the turfing and second when using the shrubs. The results showed that the use of turfing as a vegetation cover is insufficient at all thermal climatic zones of KSA, and the use of air spaces technique increased the efficiency of turfing-solid roof by 87% compared to conventional-solid roof. The use of shrubs in addition to air spaces technique increased the efficiency to acceptable level at most thermal climatic zones. The results also led to recommendations to use a manufactured thermal insulation layer, in addition to shrubs and air spaces, at the first thermal climatic zone of KSA. (C) 2018 Elsevier Ltd. All rights reserved

Optimum thermal performance of green walls systems and design requirements against heat transfer of conventional external walls of low-rise concrete buildings in hot regions

This paper presents a study on how the thermal performance of conventional external walls of concrete building could be improved against heat transfer in hot regions. 45 buildings were visited to observe the heat transfer from the warmer side of the external wall to the cooler side. The measurements showed that the conventional walls are insufficient because of high indoor temperatures. This study introduced three environmentally friendly scenarios to enhance the efficiency of the concrete wall against heat transfer. In the first scenario, a continuous air layer was added at the middle of the wall to form an aired-concrete wall. In the second scenario, a living green layer was added on the exterior side of the wall to form a living-concrete wall. The third scenario merged the previous two insights to form a living-aired-concrete wall. Thermal models were prepared to conduct thermal analysis. The results showed that the air layer deactivates the work of thermal bridges and improves the thermal resistance of the wall 5 to 15 times. In the aired-concrete wall, the results showed that the minimum depth of the air layer should be at least 6 cm, to secure a convenient indoor environment with indoor temperature not more than 25 degrees C. Furthermore, the results showed that adding only an outdoor living green layer to the conventional wall is insufficient in all thermal zones of hot regions. Finally, the best thermal performance against heat transfer was found in the living-aired-concrete wall using outdoor Perennials plants and 5 cm middle air layer

Experimental and Numerical Investigation of Single Fiber Pull-Out Tests of Steel Macro-Fiber and Glass Micro-Fiber in a Cementitious Matrix

This paper presents a modeling-based relationship between fiber diameter and frictional bond strength for steel macro-fiber (0.8-mm diameter) and glass micro-fiber (5-24-mu m diameter) embedded in a cementitious matrix. A combined approach of experimental stress-displacement results obtained through single fiber pull-out tests and finite element modeling (FEM)-based stress-displacement results yielded the friction coefficient for the two types of fibers used. Further analysis relating to the pressure exerted on the fiber caused by the surrounding concrete reveals that a smaller fiber diameter would improve the bond strength. The improvements in frictional bond strength due to reduced diameter are based on FEM analysis. Validation of the experimental results is done through numerical approaches. The results showed that in the case of the same diameter, the pressure of the surrounding concrete decreases throughout the fiber sliding. The results also showed that the smaller diameter of fiber improves the properties of fiber-reinforced concrete interfaces

Prediction of (Steel-Glass) Fiber/Concrete Interfacial Friction Properties in FRC Composites Using Calibration Method and Evaluation of Fiber Diameter Role

This paper presents a series of single fiber pull-out tests on steel and glass fiber embedded in a cementitious matrix. First, the phase of fiber sliding in the concrete matrix was defined using a shear lag model; then, governing equations for the sliding mechanism were derived using the analytical model. FEM analysis was then used to calibrate the frictional coefficient. Further analysis related to the pressure exerted on the fiber by the surrounding concrete revealed that a smaller fiber diameter would improve bond strength. In terms of the relationship between pressure from the surrounding concrete and the diameter of the fiber, the results showed that a smaller fiber diameter would increase the matrix pressure; improved frictional bond strength and behavior would be expected compared to larger fiber diameters. The results also showed that decreasing fiber diameter by 75% would improve the frictional bond strength by as much as 300% for smooth and straight steel fiber, whereas reducing the fiber diameter by 66% would improve the frictional bond strength by 190% for single glass fibers. In addition, the results showed that a smaller diameter of the fiber improves interfacial properties between the fiber and concrete in fiber-reinforced concrete (FRC) composites

Fracture and Post-Cracking Behavior Prediction for Glass and Carbon Fibre Reinforced Concrete Construction Members

Experimental investigation of AR glass fiber and carbon fiber concrete strength and post cracking non-linear behaviour were realized. Simultaneously fiber pull-out micromechanical investigation was realized experimentally (for glass and carbon single fiber and fiber bundles) and numerically (using FEC ANSYS). Structural fiberconcrete fracture model were elaborated. On the base of micromechanical results predictions for fiberconcrete non-linear post-cracking behaviour were successfully made for fiberconcrete prisms subjected to 4-point bending. Model predictions were experimentally verified