Current Issue : July - September Volume : 2017 Issue Number : 3 Articles : 5 Articles
Flat slab systems are vastly used in multi-story buildings because of their savings in story height and construction time,\nas well as for their flexibility in architectural remodeling. However, they frequently suffer brittle punching-shear failure around\ncolumns, especially when subjected to lateral loads. Therefore, seismic codes labeled flat slabs as non-ductile systems. This\nresearch goal is investigating some construction alternatives to enhance flat slab ductility and deformability. The alternatives are:\nadding different types of punching-shear reinforcement, using discreet fibers in concrete mixes, and increasing thickness of slab\naround columns. The experimental study included preparation and testing of seven half-scale interior slab-column connections up\nto failure. The first specimen is considered a reference, the second two specimens made of concrete mixes with different volumetric\nratios of polymer fibers. Another three specimens reinforced with different types of punching-shear reinforcement, and the last\nspecimen constructed with drop panel of inverted pyramidal shape. It is found that using the inverted pyramid-shape drop panel of\nspecimen, increases the punching-shear capacity, and the initial and the post-cracking stiffnesses. The initial elastic stiffnesses are\ndifferent for all specimens especially for the slab with closed stirrups where it is experienced the highest initial stiffness compared\nto the reference slab....
This study investigates the blast resistance of fiber-reinforced cementitious composite (FRCC) panels, with fiber\nvolume fractions of 2%, subjected to contact explosions using an emulsion explosive. A number of FRCC panels with five\ndifferent fiber mixtures (i.e., micro polyvinyl alcohol fiber, micro polyethylene fiber, macro hooked-end steel fiber, micro polyvinyl\nalcohol fiber with macro hooked-end steel fiber, and micro polyethylene fiber with macro hooked-end steel fiber) were fabricated\nand tested. In addition, the blast resistance of plain panels (i.e., non-fiber-reinforced high strength concrete, and non-fiberreinforced\ncementitious composites) were examined for comparison with those of the FRCC panels. The resistance of the panels to\nspall failure improved with the addition of micro synthetic fibers and/or macro hooked-end steel fibers as compared to those of the\nplain panels. The fracture energy of the FRCC panels was significantly higher than that of the plain panels, which reduced the local\ndamage experienced by the FRCCs. The cracks on the back side of the micro synthetic fiber-reinforced panel due to contact\nexplosions were greatly controlled compared to the macro hooked-end steel fiber-reinforced panel. However, the blast resistance of\nthe macro hooked-end steel fiber-reinforced panel was improved by hybrid with micro synthetic fibers...
A steel-fiber-reinforced polymer (FRP) composite bar (SFCB) is a kind of rebar with inner steel bar wrapped by FRP, which can\nachieve a better anticorrosion performance than that of ordinary steel bar. The high ultimate strength of FRP can also provide\na significant increase in load bearing capacity. Based on the adequate simulation of the load-displacement behaviors of concrete\nbeams reinforced by SFCBs, a parametric analysis of the moment-curvature behaviors of concrete beams that are singly reinforced\nby SFCB was conducted. The critical reinforcement ratio for differentiating the beam�s failuremode was presented, and the concept\nof the maximum possible peak curvature (MPPC) was proposed. After the ultimate curvature reached MPPC, it decreased with an\nincrease in the postyield stiffness ratio (...
A numerical simulation was conducted to investigate the local buckling behaviour of the bolted steel plates in steel jacketing\ntechnique. The numerical model was firstly validated by the results of a previous experimental study. Then a parametric study\nwas conducted to investigate the influence of different restraint measures on the local buckling behaviour and the sensitivity of the\nbuckling behaviour to the initial imperfection. Fitted formulae were developed to calculate the structural field capacity of the bolted\nsteel plates, and recommended values of stiffener size were also provided to facilitate the strengthening design of steel jacketing....
Strengthening reinforced concrete (RC) beams with openings by using aramid fiber reinforcement polymers (AFRP)\non the beamsââ?¬â?¢ surfaces offers a useful solution for upgrading concrete structures to carry heavy loads. This paper presents a\nrepairing technique of the AFRP sheets that effectively strengthens RC beams, controls both the failure modes and the stress\ndistribution around the beam chords and enhances the serviceability (deflection produced under working loads be sufficiently small\nand cracking be controlled) of pre-cracked RC beams with openings. To investigate the possible damage that was caused by the\nservice load and to simulate the structure behavior in the site, a comprehensive experimental study was performed. Two unstrengthened\ncontrol beams, four beams that were pre-cracked before the application of the AFRP sheets and one beam that was\nstrengthened without pre-cracking were tested. Cracking was first induced, followed by repair using various orientations of AFRP\nsheets, and then the beams were tested to failure. This load was kept constant during the strengthening process. The results show\nthat both the preexisting damage level and the FRP orientation have a significant effect on strengthening effectiveness and failure\nmode. All of the strengthened specimens exhibited higher capacities with capacity enhancements ranging from 21.8 to 66.4%, and\nthe crack width reduced by 25.6ââ?¬â??82.7% at failure load compared to the control beam. Finally, the authors present a comparison\nbetween the experimental results and the predictions using the ACI 440.2R-08 guidelines....
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