Current Issue : July - September Volume : 2019 Issue Number : 3 Articles : 5 Articles
The paper presents experimental and numerical investigations on the behaviour of rubberized concrete short columns confined\nwith aramid fibre reinforced polymer (AFRP) subjected to compression. Additionally, the possibilities to substitute fine aggregate\nwith crumb rubber granules, obtained from discarded worn tires, in structural concrete is also assessed. Because replacing\ntraditional concrete aggregates by rubber particles leads to a significant loss in compressive strength, the authors highlight the use\nof AFRP confinement to partially or fully restore the compressive strength by applying a number of 1, 2, and 3 layers. Analytical\nmodels available for confined regular concrete are used to predict the peak stresses and the corresponding peak strains. Some\nanalytical models give accurate results in terms of peak stress while others better approximate the ultimate strain. The full stressstrain\ncurve of rubberized concrete and the experimentally obtained values for the material properties of AFRP are used as input\ndata for the numerical modelling. A good agreement is found between the results obtained for the peak stress and corresponding\naxial strain from both the numerical simulations and the experimental investigations....
The adhered mortars in recycled aggregates (RA) may lower the performance of the\nconcrete, by for instance reducing its strength and durability, and by cracking. In the present study,\nthe effect of nylon fiber (NF) on the permeability as well as on the mechanical properties of concrete\nincorporating 100% RA was experimentally investigated. Concrete was produced by adding 0, 0.6 and\n1.2 kg/m3 of NF and then cured in water for a predetermined period. Measurements of compressive\nand split tensile strengths, ultrasonic pulse velocity and total charge passed through concrete were\ncarried out, and the corresponding test results were compared to those of concrete incorporating\ncrushed stone aggregate (CA). In addition, the microstructures of 28-day concretes were examined\nby using the FE-SEM technique. The test results indicated that recycled coarse aggregate concrete\n(RAC) showed a lower performance than crushed stone aggregate concrete (CAC) because of the\nadhered mortars in RA. However, it was obvious that the addition of NF in RAC mixes was much\nmore effective in enhancing the performance of the concretes due to the crack bridging effect from\nNF. In particular, a high content of NF (1.2 kg/m3) led to a beneficial effect on concrete properties\ncompared to a low content of NF (0.6 kg/m3) with respect to mechanical properties and permeability,\nespecially for RAC mixes....
This paper presents the ground deformation induced by the large slurry shield tunnelling with a diameter of about 12m in urban\nareas, which may challenge the safety of the existing nearby constructions and infrastructures. In this study, the ground deformation\nis analyzed by a three-dimensional finite difference model, involving the simulation of tunnelling advance, grouting,\nand grouting hardening. The transverse settlement, longitudinal settlement, and horizontal displacement of the ground are\nanalyzed by comparing the simulation results with the field measurements in the Rapid Transit Line Project from Beijing Railway\nstation to West Beijing Railway station in China. The numerical model proposed in this paper could well predict the ground\ndeformation induced by large slurry shield tunnelling. The results show that the main transverse settlement occurs within the zone\nabout 1.5 times of the excavation diameter, and the settlement during the passage of the shield and the tail void plays a most\nimportant role in the excavation process....
This paper presents possibilities for anti-seismic improvement of traditional timber\ncarpentry joints. It is known that the structural response of historical roof frameworks is highly\ndependent on the behavior of their joints, particularly, their capacity for rotation and energy\ndissipation. Any strengthening, or retrofitting, approach must take into account conservation\nrequirements, usually expressed as conditions involving minimal intervention. Several retrofitting\nmethods were tested on replicas of historical halved joints within various national and international\nresearch projects. The joints were produced with traditional hand tools, and made using aged\nmaterial taken from a demolished building. The paper presents two approaches, each utilizing\ndifferent retrofitting technologies that avoid completely dismantling the joint and consequently\nconserve frame integrity. The energy dissipation capacity is increased by inserting mild steel nails\naround a wooden pin, and connecting the two parts of the halved joint. In the second case, two thin\nplates made of a material with a high friction coefficient are inserted into the joint and fastened to the\nwooden elements. This is done by removing the wooden connecting pin and slightly opening a slot\nfor the plates between the halved parts. In addition, the paper presents an application for disc brake\nplates, as well as thin plates made of oak....
Buildings that are designed to meet high-energy performance requirements, e.g., passive\nhouses, require well-insulated building envelopes, with increased insulation thicknesses for roof,\nwall and floor structures. We investigate whether there are differences in the efficiency of thermal\ninsulation materials at different moisture levels in the insulation and if there is a larger or smaller\nrisk of natural convection in wood-fibre based insulation than in mineral wool. The work has mainly\nbeen performed by use of laboratory measurements included permeability properties and full-scale\nmeasurements of thermal transmittance of mineral wool and wood-fibre insulated constructions.\nIn addition, calculations have been used to calculate resulting effects on the thermal performance\nof constructions. Results showed that the thermal conductivity was unaffected by moisture in the\nhygroscopic range. The air permeability was found to be approximately 50% higher for the wood-fibre\ninsulation compared to mineral wool insulation. Measurements showed that the largest U-values\nand Nusselt numbers were found for the wall configuration. Calculation of the U-value of walls\nshowed that in order to achieve the same U-value for the wood-fibre insulated wall as the mineral\nwool, it is necessary to add 20 mm insulation to the 250 mm wall and approximately 30 mm for the\n400 mm wall....
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