• Computers and Concrete
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• v.30 no.4
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• pp.277-287
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• 2022

Due to the scarcity of extortionate experimental data, fatigue failure of the reinforced concrete (RC) element might be achieved economically adopting nonlinear finite element (FE) analysis as an alternative approach. However, conventional implicit dynamic analysis is expensive, quasi-static method overlooks interaction effects and inertia, direct cyclic analysis computes stabilized responses. Apart from this, explicit dynamic analysis may provide a numerical operating system for factual long-term responses. The study explores the fatigue behavior based on a simplified explicit dynamic solution employing nonlinear time domain analysis. Among fourteen RC beams, one beam is selected to validate under static loading, one under fatigue with the experimental study and other twelve to check the detail fatigue behavior. The SWOT (Strength, Weakness, Opportunities, Threats) analysis has been carried out to pinpoint the detail scenario in the adoption of numerical approach as an alternative to the experimental study. Excellent agreement of FE and experimental results is seen. The 3D nonlinear RC beam model at service fatigue limits is truthful to be used as an expedient contrivance to envisage the precise fatigue behavior. The simplified analysis approach for RC beam under fatigue offers savings in computation to predict responses providing acceptable accuracy rather than the complicated laboratory investigation. At higher frequency, the flexural failure occurs a bit earlier gradually compared to the repeated loading case of lower frequency. The deflection increases by 6%-10% at the end of first cycle for beams with increasing frequency of cyclic loading. However, at the end of fatigue loading, greater deflection occur earlier for higher load range because of more rapid stiffness degradation. For higher frequency, a slight boost in concrete compressive strains at an initial stage of loading has been seen indicating somewhat stepper increment. Stiffness degradation in larger loading cycle at same duration escalates the upsurge of the rate of strain in case of higher frequency.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3A
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• pp.383-390
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• 2008

A Precast Prefabricated Bridge Column using steel tube and prestressing bar was proposed for the application of precast method on substructure. A column specimen designed by the proposed bridge column system was made and performed a quasi-static test. The failure mode appeared to be a flexural failure and there is no damage on column segment connection. And it is good use of the self-centering ability by prestressing force. Test results showed that a column specimen satisfy the earthquake specification, and the structural stability was verified. Nonlinear finite element analysis was performed and compared with the test results. Force-displacement relation and location of crack from the analysis results were compared with the test results and it agreed well. The quantitative analysis was also performed by a parametric study using this modeling technique.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.1
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• pp.47-57
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• 2024

Recently, in newly constructed apartment buildings, the exterior wall structures have been characterized by thinness, having various openings, and a significantly low reinforcement ratio. In this study, a nonlinear finite element analysis was performed to investigate the crack damage characteristics of the exterior wall structure. The limited analysis models for a 10-story exterior wall were constructed based on the prototype apartment building, and nonlinear static analysis (push-over analysis) was performed. Based on the finite element (FE) analysis model, the parametric study was conducted to investigate the effects of various design parameters on the strength and crack width of the exterior walls. As the parameters, the vertical reinforcement ratio and horizontal reinforcement ratio of the wall, as well as the uniformly distributed longitudinal reinforcement ratio and shear reinforcement ratio of the connection beam, were addressed. The analysis results showed that the strength and deformation capacity of the prototype exterior walls were limited by the failure of the connection beam prior to the flexural yielding of the walls. Thus, the increase of wall reinforcement limitedly affected the failure modes, peak strengths, and crack damages. On the other hand, when the reinforcement ratio of the connection beams was increased, the peak strength was increased due to the increase in the load-carrying capacity of the connection beams. Further, the crack damage index decreased as the reinforcement ratio of the connection beam increased. In particular, it was more effective to increase the uniformly distributed longitudinal reinforcement ratio in the connection beams to decrease the crack damage of the coupling beams, regardless of the type of the prototype exterior walls.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.121-128
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• 2005

This study focuses on evaluating the reliability index of a deck of RC slab having chloride contamination and studying the relation of grades of rebar corrosion and the reliability index of a bridge deck For this purpose, first, the failure probability related to flexural strength was calculated using a model for deterioration, which contains the application of deicing salts that usually causes significant long-term deterioration and reduction in the structural safety for strength of structure. And also, according to the depth of covering, the chloride contents depending on time due to depths of RC slab deck, the appearance time for initial corrosion of rebar and the occurrence time for split of covering were investigated using a MCS method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.479-486
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• 2004

The purpose of this study is to practical use with increase safety, usablility and economical. In this study, the property of fatigue behavior was tested by comparing reinforced concrete and steel fiber reinforced concrete. The basic test, the static test and fatigue test were used as the research methods. Basic on the test, the material compressive strength test and split tensile strength test ware conducted 7 days and 28 days after the concrete was poured. In the static test, there ware four types of experimental variables of the steel fiber mixing ratio : 0.00%, 0.75%, 1.00%, and 1.25%. The ultimate load initial diagonal tension crack, and initial load of flexural cracking were all observed by static test. A methodology for the probabilistic assement of steel fiber reinforced concrete(SFRC) which takes into account material variability, confinement model uncertainty and the uncertainty in local and globa failure criteria is applied for the derivation of vulnerability curves for the serviceability and ultimate limit states, the reliability of SFRC using the proposed practical linear limit state model is evaluated by using the AFOSM(Advanced First Order Second Moment) method and MCS(monte-Calrosimulation) method.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.5
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• pp.25-35
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• 2003

Scale model tests were performed to investigate the seismic behavior of the solid and hollow rectangular RC piers with 50% of lap-spliced longitudinal bars in plastic hinge regions. Continuous bars and lap-spliced ones with a lap length of 39 times the bar diameter were arranged alternately in the sections. In order to clarify the influence of lap splice on a ductility the effect of axial force and lateral confinement were excluded in the test. The typical flexural failure conducting a ductile behavior were observed in both models. It is confirmed that the 50% of lap-spliced bars can be considered as an alternative of seismic detailing for longitudinal bars.

• Smart Structures and Systems
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• v.16 no.4
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• pp.593-606
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• 2015

This paper presents a novel concept of healing some of the damages in wind turbine blades (WTBs) such as cracks and delamination. This is achieved through an inherent functioning autonomous repairing system. Such wind turbine blades have the benefit of reduced maintenance cost and increased operational period. Previous techniques of developing autonomous healing systems uses hollow glass fibres (HGFs) to deliver repairing fluids to damaged sites. HGFs have been reported with some limitations like, failure to fracture, which undermines their further usage. The self-healing technique described in this paper represents an advancement in the engineering of the delivery mechanism of a self-healing system. It is analogous to the HGF system but without the HGFs, which are replaced by multiple hollow channels created within the composite, inherently in the FRP matrix at fabrication. An in-house fabricated NACA 4412 WTB incorporating this array of network hollow channels was damaged in flexure and then autonomously repaired using the vascular channels. The blade was re-tested under flexure to ascertain the efficiency of the recovered mechanical properties.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.13-24
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• 1999

The external, unbonded prestressed concrete(PSC) members exhibit very different structural behavior from that of internal bonded PSC members because of eccentricity change and slip occurrence during loading process. The purpose of the present study is to propose the ultimate failure stresses of prestressing (PS) steels for those external unbonded PSC members. To this end, a comprehensive analysis has been made using the nonlinear finite element analysis program developed recently for external unbonded PSC members by authors. A series of major influencing variables have been included in the analysis. It was found that the span-depth ratio, neutral axis depth-effective depth ratio, load geometry, amount of ordinary steel, and prestressing steel ration have great influence for the ultimate failue stress of PS steel is preposed and is compared with experimental dat as well as existing formulas for internal unbonded members. The Comparison indicates that the proposed equation agrees relatively well with experimental data and that existing formulas including ACI and AASHTO equations show some discrepancies from experimental ones. The present study allows more realistic analysis and design of prestressed concrete structures with external unbonded tendons.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.4
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• pp.1-8
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• 1991

Recently the use of steel fibers has been increased in flexural members and columns of concrete structures subjected to cyclic loadings; such as bridge decks, highway roads, runway of airport, buildings, etc.. However only a few experimental tests have been carried out under fatigue loading. In the present study, the reinforced concrete beams with 1% and 2% steel fiber volume fraction are investigated with and without stirrups. It has been found that in fatigue tests, the failure of the beam is usually due to breaking of fibers rather than fiber pull-out. A comparison of experiments and numerical analysis using the nonlinear F.E.M. program (ADINA) is also presented herein.

• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.379-388
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• 2013

This paper aims to experimentally investigate the fire resistance of U-shaped hybrid composite beams protected by spay and paint insulations. Subjected to two and three hours of the Standard ISO fire, the flexural performance of 4.4m beams with/without imposed loadings was examined with respect to failure criteria such as deflection and deflection rate of the mid-span and temperatures measured in the steel section. The results demonstrated that the proposed configuration of the composite beam is able to achieve a very competitive 3-hour fire resistance rating in economical aspects.