Current Issue : January - March Volume : 2020 Issue Number : 1 Articles : 5 Articles
Many researchers worldwide have extensively used fibre-reinforced polymer (FRP) strengthening materials and near-surface\nmounted (NSM) to enhance the shear and flexural strengths of reinforced concrete (RC) beams. However, studies on torsional\nstrengthening are limited. Although a few studies have focused on torsional strengthening, none of them simultaneously investigated\ntorsion with shear and/or bending moment. This study aims at demonstrating the behaviour of RC beams strengthened\nwith FRP sheets (strips) with different configurations and NSM steel bars with different spacing that was subjected to combined\nactions of torsion and bending moment and making a comparison between them. Seven beams with a dimension of\n15 * 25 * 200 cm were casted. One of the beams was not strengthened; three of them were strengthened with carbon FRP, and the\nothers were strengthened with NSM steel bar. The angle of twist at torque intervals, first cracking torque, ultimate torque, and\nultimate twist angle of the conventional and strengthened beams during the testing process are compared. Results show a\nsignificant improvement in the torsional performance of RC beams using carbon FRP and NSM steel bar. The test beams that were\nstrengthened with CFRP wrapping showed better enhancement in the ultimate torsional moment as opposed to the beams that\nwere strengthened with NSM steel bar....
At the present, the natural stone used for traditional block rock revetment is becoming increasingly scarce, and other commonly used\nrevetment types also have some problems, such as poor stability, complex fabrication and installation process, and large investment.\nTherefore, it is imminent to study a new type of reinforcement of dangerous dam banks with both ecological and environmental\nprotection functions to meet the requirement of river flood stability. Combining theoretical calculation with laboratory tests, a new slope\nprotection block of H-type gravity mutual-aid steel slag core concrete (H-type gravity mutual-aid steel slag core concrete block\nhereinafter), which is composed of an ordinary concrete shell and a steel slag core, is designed as an improvement of revetment reinforcement\ntype and for solid waste utilization and resource saving. The indoor test method shows that the optimal shell thickness of the\nnew block is 6 cm, and the steel slag of a single block can replace the natural aggregate ratio of 25%.The new block has concave and convex\nstructures to enhance the interlocking effect between blocks. The compressive strength of the new block is tested by the drilling core\ncompressive strength test to meet the strength requirement of the revetment works. Moreover, on the basis of the overall stability test\nplatform of the interlocking block and numerical simulation analysis, the H-type gravity mutual-aid steel slag core concrete block was\nproved to have a better interlocking effect than the traditional blocks and exhibits excellent overall stability....
The trench cutting remixing deep wall (TRD) method is a new cement soil cut-off wall construction technique, which has been\nwidely used in cofferdam, embankment dam, and underground waterproof curtain structures. The chain cutter of TRD moves\nhorizontally to cut and stir different soil layers by up and down to form a cement-mixed soil diaphragm wall with continuous and\nuniform thickness, the mechanics and permeability of which are obviously different from those of cement soil with a horizontally\nmixed single soil layer in traditional deep mixing pile (DMP). In this paper, five sets of onsite walling tests with different cement\nratios were carried out to analyse the unconfined compression and permeability of undisturbed cement-mixed soil in TRD. The\ndifference of both unconfined compressive and permeability coefficients in between TRD and DMP was analysed to discuss the\nstirring performance of TRD. Then, the microscopic mechanism of soil properties affecting the performance of cement-mixed soil\nhas been studied by scanning electron microscopy (SEM) in the unconfined compression strength test and permeability coefficient\ntest of cement soil with different mixed soil properties. The test results show that the unconfined compressive strength of cementmixed\nsoil is closely correlated to its gradation. As the mixed soil gradation curve approaches to the Fuller curve, the unconfined\ncompressive strength would gradually increase. In mesoscopic, cement fine sand has a large pore structure, and the average pore\narea is 2.46 times as cement clay. The permeability coefficient of cement-mixed soil is controlled by the proportion of fine sand\ncontent with high permeability....
Inverse analysis is necessary for concrete dams in normal operation to overcome the discrepancy between the true mechanical\nparameters and test results. In view of the uncertain characteristics of concrete dams, a stochastic inverse model is proposed in this\nstudy to solve the undetermined mechanical parameters with sequential and spatial randomness using measured displacement\ndata and Bayesian back analysis theory. An inversion method for the mechanical parameters of concrete dams is proposed. Fast\nFourier transform algorithm is introduced to generate random fields for SFEM analysis. The case study shows that the proposed\ninversion method can reflect the random characteristics of concrete dams, the mechanical parameters obtained are reasonable,\nand the inverse model is feasible....
Reservoir dams are mostly built in alpine valley areas. The water surface of the river valley is narrow and the geometric features of\nhydraulic structures are complex, which result in different absorption, reflection, and diffraction effects on sound waves for\nvarious propagation media. Further, for relatively narrow underwater water space where the underwater detection equipment is\nlocated, there is significant interference to the underwater acoustic communication signal. This is a major challenge to underwater\npositioning technology. Therefore, in this study, the scattering effect of different markers placed on a dam face on the sound waves\nemitted by sonar carried by a remote control unmanned submersible in a reservoir environment was investigated. The singular\nboundary method was used to develop a simulation model of the scattering effect on the sound waves of three different markers\n(i.e., cross boards, spherical bodies, and square plates) placed on a dam face in the deepwater environment of a reservoir. The\nscattering effect of typical geometrical markers was also investigated with respect to the sound waves of different frequencies and\ndifferent incident angles. The sound pressure level (SPL) was used as an indicator for determining the scattering effect, so that the\ngeometry of the marker with well scattering effect could be determined. In this study, the Guanyinyan hydropower dam was\nconsidered as the research area. The results show that the scattering SPL of the cross board is higher than those of the spherical\nbody and the square plate, i.e., using the cross board as a marker produces the most accurate positioning of the underwater\ndetection remote control unmanned submersible of a dam project in the deepwater environment of a reservoir....
Loading....