Current Issue : October - December Volume : 2017 Issue Number : 4 Articles : 5 Articles
Theimportance of an accurate simulation of service conditions in the bond performance of reinforced concrete structures in coastal\nregions is highlighted. Four widths of initial crack of 0, 80, 150, and 210 microns were artificially made by inserting slice into bond\nspecimens during concrete casting. Three bar diameters of 10 mm, 14 mm, and 18mmwere selected. At 28 days, the bond specimens\nwere exposed to the environment of wet-dry cycles of seawater and atmosphere for another 90 days. The pull-out test was then\nconducted and chloride contents were tested at crack area along 40mm depth. Results show that, for the specimen with 10mm\nbar diameter, cracks width of less than 80 microns vanished rapidly during wet-dry cycles; for other specimens, cracks width of\n100ââ?¬â??150 microns decreased slightly. However the cracks of width more than 200 microns increased gradually; the chloride content\ndecreased along the depth of concrete, and the chloride content increased as the widths of initial cracks increased or as the bar\ndiameters increased.The ductility of bond specimens decreased as the diameter increased....
Corrosion occurs more rapidly under high tensile stress and this leads to several problems like degradation of serviceability and\nstructural performance in PSC (prestressed concrete) structures. In this paper, impressed current method, so-called ICM, was\napplied to tendons under tensile loadings of 0.0, 20.0, 40.0, and 60.0% of ultimate load.With induction of 20 volts for 24 hours to\ntendon under tensile stress, loading was induced to failure and the ultimate load was evaluated with varying corrosion behaviors.\nThechanging mechanical behaviors in the same corrosive conditions were evaluated under different initial prestressing levels.With\nincreasing initial prestressing load, corrosion occurredmore rapidly and corrosion amount also increased linearly.The ultimate load\naccordingly decreased with increasing initial prestressing and corrosion amount. The relationships between prestressing levels and\ncorrosion behaviors were quantitatively obtained through regression analysis.Themeasured current during applied voltage and the\nrelated corrosion amounts were also dealt with in this work....
Recently, ultra high performance fiber reinforced concrete (UHPFRC) has been developed to attain considerably increased\ncompressive cracking strength and ductile tensile behavior with high tensile strength through adding straight steel fibers in concrete\nmixture. Although benefits with UHPFRC were investigated through experimental program, it is difficult to predict structural\nbehavior ofUHPFRCmembers since theoretical approaches are limited. In this paper, inverse analysis procedure has been proposed\nfor a three-point bending test with notched UHPFRC beams so that tensile behavior of UHPFRC could be rationally evaluated.\nOn the inverse analysis procedure, failure mode of the UHPFRC beam was simplified and the simplified diverse embedment\nmodel (SDEM) was employed. To verify the proposed inverse analysis procedure, UHPFRC beams with a notch were analyzed\nwith the tensile behavior of UHPFRC evaluated through the inverse analysis procedure. The analytical predictions showed good\nagreement with the load-crack mouth opening displacement (CMOD) responses measured through the three-point bending test.\nConsequently, it can be concluded that UHPFRC tensile behavior can be rationally evaluated through the proposed inverse analysis\nprocedure.Theproposed inverse analysis procedure can be useful in relevant research areas such as development of advanced design\napproaches or computational methods for UHPFRC members....
A reliability-based method was developed for\npredicting the initiation time and the probability of flexural\nfailure for continuous slab bridges with load-induced\ncracks exposed to chloride environment resulting from deicing\nsalts. A practical methodology was used for predicting\nthe diffusion coefficient of chloride ingress into the\npre-existing load-induced cracks in concrete. The reduction\nin the cross-sectional area of the reinforcement due to\ncorrosion was included in the model. The proposed\nmethodology accounts for uncertainties in the strength\ndemand, structural capacity, and corrosion models, as well\nas uncertainties in environmental conditions, material\nproperties, and structural geometry. All probabilistic data\non uncertainties were estimated from the information\ncontained in previous experimental and statistical studies.\nAs an application of the proposed model, a three-span\ncontinuous slab bridge in Ohio is presented for demonstration\nof the developed methodology. A comparison of\nresults clearly shows the importance of considering the\neffects of the load-induced cracks for correct prediction of\nthe initiation of corrosion time and the critical time to\nmaintain structural integrity....
According to the purpose of the opening and the structural designer, the\nshape of the web opening is decided. It is too easy to choose the shape of\nopenings from regular shape whether it is circular or rectangular shape. The\npresence of openings in the web of steel beams decreases stiffness of the beam\nand introducing a larger deflection than in the steel web opening with solid\nopening. A steel beam with web opening is analyzed in this paper. ABAQUS\nsoftware is using for analyzing nonlinear static and dynamic opening of steel\nbeam with different position and supporting conditions....
Loading....