Current Issue : October - December Volume : 2016 Issue Number : 4 Articles : 5 Articles
An overall review of the structural behaviors of ultra-high-performance fiber-reinforced concrete (UHPFRC) elements\nsubjected to various loading conditions needs to be conducted to prevent duplicate research and to promote its practical applications.\nThus, in this study, the behavior of various UHPFRC structures under different loading conditions, such as flexure, shear,\ntorsion, and high-rate loads (impacts and blasts), were synthetically reviewed. In addition, the bond performance between\nUHPFRC and reinforcements, which is fundamental information for the structural performance of reinforced concrete structures,\nwas investigated. The most widely used international recommendations for structural design with UHPFRC throughout the world\n(AFGC-SETRA and JSCE) were specifically introduced in terms of material models and flexural and shear design. Lastly,\nexamples of practical applications of UHPFRC for both architectural and civil structures were examined....
This paper presents an experimental work to study the flexural strength of reinforced concrete (RC) beams\nstrengthened by partially de-bonded near surface-mounted (NSM) fiber reinforced polymer (FRP) strip with various de-bonded\nlength. Especially, considering high anchorage capacity at end of a FRP strip, the effect of de-bonded region at a central part was\ninvestigated. In order to check the improvement of strength or deformation capacity when the bonded surface area only increased\nwithout changing the FRP area, single and triple lines of FRP were planned. In addition, the flexural strength of the RC member\nstrengthened by a partially de-bonded NSM FRP strip was evaluated by using the existing researchers� strength equation to predict\nthe flexural strength after retrofit. From the study, it was found that where de-bonded region exists in the central part of a flexural\nmember, the deformation capacity of the member is expected to be improved, because FRP strain is not to be concentrated on the\ncenter but to be extended uniformly in the de-bonded region. Where NSM FRP strips are distributed in triple lines, a relatively high\nstrength can be exerted due to the increase of bond strength in the anchorage....
As part of this study, has been developed a numerical method which allows to establish abacuses connecting the\nnormal force with bending moment for a circular section and therefore to predict the rupture of this type of section. This may be for\nreinforced concrete (traditional steel) or concrete reinforced with steel fibers. The numerical simulation was performed in nonlinear\nelasticity up to exhaustion of the bearing capacity of the section. The rupture modes considered occur by plasticization of the steel\nor rupture of the concrete (under compressive stresses or tensile stresses). Regarding the fiber-reinforced concrete, the rupture\noccurs, usually, by tearing of the fibers. The behavior laws of the different materials (concrete and steel) correspond to the real\nbehavior. The influence of several parameters was investigated, namely; diameter of the section, concrete strength, type of steel,\npercentage of reinforcement and contribution of concrete in tension between two successive cracks of bending. A comparison was\nmade with the behavior of a section considering the conventional diagrams of materials; provided by the BAEL rules. A second\ncomparative study was performed for fibers reinforced section....
Steel fiber-reinforced prestressed concrete (SFRPSC) members typically have high shear strength and deformation\ncapability, compared to conventional prestressed concrete (PSC) members, due to the resistance provided by steel fibers at the\ncrack surface after the onset of diagonal cracking. In this study, shear tests were conducted on the SFRPSC members with the test\nvariables of concrete compressive strength, fiber volume fraction, and prestressing force level. Their localized behavior around the\ncritical shear cracks was measured by a non-contact image-based displacement measurement system, and thus their shear\ndeformation was thoroughly investigated. The tested SFRPSC members showed higher shear strengths as the concrete compressive\nstrength or the level of prestress increased, and their stiffnesses did not change significantly, even after diagonal cracking due to the\nresistance of steel fibers. As the level of prestress increased, the shear deformation was contributed by the crack opening\ndisplacement more than the slip displacement. In addition, the local displacements around the shear crack progressed toward\ndirections that differ from those expected by the principal strain angles that can be typically obtained from the average strains of\nthe concrete element. Thus, this localized deformation characteristics around the shear cracks should be considered when measuring\nthe local deformation of concrete elements near discrete cracks or when calculating the local stresses....
Recently, advanced transit systems are being constructed to reduce traffic congestions in metropolitan areas. For these\nprojects, curved bridges with various curvatures are required. Many curved bridges in the past were constructed using aesthetically\nunpleasant straight beams with curved slabs or expensive curved steel box girders with curved slabs. Therefore, many recent\nstudies have been performed to develop less expensive and very safe precast prestressed concrete (PSC) curved girder. One method\nof reducing the construction cost of a PSC curved girder is to use a reusable formwork that can easily be adjusted to change the\ncurvature and length of a girder. A reusable and curvature/dimension adjustable formwork called Multi-tasking formwork is\ndeveloped for constructing efficient precast PSC curved girders. With the Multi-tasking formwork, two 40 m precast PSC box\ngirders with different curvatures were constructed to build a two-girder curved bridge for a static flexural test to evaluate its safety\nand serviceability performance. The static flexural test results showed that the initial cracking load was 1400 kN, exceeding the\ndesign cracking load of 450 kN. Also, the code allowed deflection of 50 mm occurred at a load of 1800 kN, verifying the safety\nand serviceability of the precast PSC curved bridge constructed using the multi-tasking formwork....
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