• Structural Engineering and Mechanics
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• v.42 no.4
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• pp.551-570
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• 2012

An experimental program was carried out to investigate the influence of fibre reinforcement on the mechanical behaviour of high strength reinforced concrete beams. Eighteen beams, loaded in four-point bending tests, were examined by applying monotonically increasing controlled displacements and recording the response in terms of load-deflection curves up to failure. The major test variables were the volume fraction of steel fibres and the transverse steel amount for two different values of shear span. The contribution of the stirrups to the shear strength was derived from the deformations of their vertical legs, measured by means of strain gauges. The structural response of the tested beams was analyzed to evaluate strength, stiffness, energy absorption capacity and failure mode. The experimental results and observed behaviour are in good agreement with those obtained by other authors, confirming that an adequate amount of steel fibres in the concrete can be an alternative solution for minimizing the density of transverse reinforcement. However, the paper shows that the use of different theoretical or semi-empirical models, available in literature, leads to different predictions of the ultimate load in the case of dominant shear failure mode.

• Steel and Composite Structures
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• v.13 no.2
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• pp.123-137
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• 2012

Steel plate-masonry composite structure is a newly-developed type of structural technique applicable to existing masonry buildings by which the load-bearing walls can be removed for large spaces. This kind of structure has been used in practice for its several advantages, but experimental investigation on its elements is nearly unavailable in existing literature. This paper presents an experimental study on the flexural behaviour of four steel plate-masonry composite beams loaded by four-point bending. Test results indicate that failure of the tested beams always starts from the local buckling of steel plate, and that the tested beams can satisfy the requirement of service limit state. In addition, the assumption of plane section is still remained for steel plate prior to local buckling or steel yielding. By comparative analyses, it was also verified that the working performance of the beam is influenced by the cross-section of steel plate, which can be efficiently enhanced by epoxy adhesive rather than cement mortar or nothing at all. Besides, it was also found that the contribution of the encased masonry to the flexural capacity of the composite beam cannot be ignored when the beam is injected with epoxy adhesive.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.831-836
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• 2000

During machining, since more than 50% compliance of the cutting point in machine tool structures comes from headstocks, with the remainder coming from beds, slides and structural joints, the structural analysis of the headstock is very important to improve the static and dynamic performances. Especially, in case of machining hard and brittle materials such as glasses and ceramics with the grinding machine, the reinforced headstock with the high damping material is demanded. Since the fiber reinforced composite materials have excellent properties for structures, owing to its high specific modulus, high damping and low thermal expansion, it is expected that the dynamic and thermal characteristics of the headstock will be improved if they are employed as the materials fur headstock. In this paper, the design and the manufacturing methods as well as the static and dynamic characteristics of a steel-composite hybrid headstock were investigated analytically and experimentally to improve the performance of the grinding machine system.

• Steel and Composite Structures
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• v.22 no.6
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• pp.1337-1358
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• 2016

The current study focuses on the assessment and interface response of reinforced concrete elements with composite materials (carbon fiber reinforced polymers-CFRPs, glass fiber reinforced polymers-GFRPs, textile reinforced mortars-TRM's, near surface mounted bars-NSMs). A description of the transfer mechanisms from concrete elements to the strengthening materials is conducted through analytical models based on failure modes: plate end interfacial debonding and intermediate flexural crack induced interfacial debonding. A database of 55 in total reinforced concrete columns (scale 1:1) is assembled containing elements rehabilitated with various techniques (29 wrapped with CFRP's, 5 wrapped with GFRP's, 4 containing NSM and 4 strengthened with TRM). The failure modes are discussed together with the performance level of each technique as well as the efficiency level in terms of ductility and bearing/ bending capacity. The analytical models' results are in acceptable agreement with the experimental data and can predict the failure modes. Despite the heterogeneity of the elements contained in the aforementioned database the results are of high interest and point out the need to incorporate the analytical expressions in design codes in order to predict the failure mechanisms and the limit states of bearing capacities of each technique.

• Computers and Concrete
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• v.20 no.4
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• pp.439-448
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• 2017

Reinforced concrete (RC) infrastructures often require strengthening due to error in design, degradation of materials properties after prolong utilization and increases load carrying capacity persuaded by new use of the structures. For this purpose, a newly proposed Side Near Surface Mounted (SNSM) composite technique was used for flexural strengthening of RC beam specimens. Analytical and non-linear finite element modeling (FEM) using ABAQUS were performed to predict the flexural performance of RC specimens strengthened with S-NSM using steel bars as a strengthening reinforcement. RC beams with various SNSM reinforcement ratios were tested for flexural performance using four-point bending under monotonic loading condition. Results showed significantly increase the yield and ultimate strengths up to 140% and 144% respectively and improved failure modes. The flexural response, such as failure load, mode of failure, yield load, ultimate load, deflection, strain, cracks characteristic and ductility of the beams were compared with those predicted results. The strengthened RC beam specimens showed good agreement of predicted flexural behavior with the experimental outcomes.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.2
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• pp.157-166
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• 2001

The purpose of this study is to examine the accuracy of the code provisions on lateral load distribution factors of prestressed concrete girder bridges. Most designers in Korea use the lever method or lateral load distribution formula in the existing design codes. However, the methods do not account for the effect of bridge skew or direction of diaphragm. Therefore, this study analysed the prestressed concrete girder bridge with grillage model for various girder spacings, directions of diaphragms, span lengths, and skews, and compared the results with those of existing design code. It has been found that lateral load distribution factors were proportional to the girder spacing while they were not significantly affected by the change of span length, direction of diaphragm, and skew. For bending moments, lateral load distribution factors from the grillage analysis were 60%~68% of those from Korean bridge design code. Therefore, the code provisions result in very conservative design. For support reactions, however, lateral load distribution factors from the grillage analysis were slightly greater than those from Korean bridge design code. Therefore, the capacity of bearings of the bridge with a large skew should be determined by grillage analysis.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.5
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• pp.23-30
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• 2009

According to Korea Highway Bridge Design Code the bridge deck is designed by the strength design method and is regarded as a beam possessing the unit width based on the bending theory. By many researches it is revealed that the existing bridge deck is failed by punching shear. For evaluating the ultimate capacity of bridge deck it is important to estimate the behavior of bridge deck under the punching shear. For the punching strength it is difficult that the existing research results are applied to the simplified composite deck. In this study for comparing characteristics on punching shear the punching shear tests on simplified composite deck and RC deck are performed. The punching shear strength of simplified composite deck is compared with several bridge design codes.

• Journal of Ocean Engineering and Technology
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• v.21 no.6
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• pp.16-25
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• 2007

In a companion paper, a rational mechanical model to predict the entire behavior of point-loaded RC slender beams (a/d > 2.5) without shear reinforcement was developed. This paper presents the test results of 9 slender shear beams and compares them with analytical results performed by the proposed model. They are grouped by two parameters, which are shear span ratio and concrete strength. Three kinds of concrete strength the 26.5, 39.2, and 58.8 MPa were included as a major experimental parameter together with different shear span ratios ranging from 3 to 6 depending on the test series. Tests were set up as a traditional 3 point bending test. Various measurements were taken to monitor abrupt shear failure. Test results were not only compared with analytical results from the proposed model, but also other formulas, to consider the various aspects of shear failure such as kinematical conditions or shear capacity. Finally, a review of the proposed model is presented with respect to the shear transfer mechanisms and the effect of test parameters. Results show that several assumptions and proposals adopted in the proposed model are rational and reasonable.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.4
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• pp.405-413
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• 2019

In this study, a progressive process was performed to fabricate the inner fin of a high-efficiency heat exchanger. A forming simulation was also carried out on the concavo-convex of the inner fin, forming a simulation based on elastic-plastic finite element method. The forming analysis where the speed of the press descended and ascended was set to five seconds showed that the effective stress was at a maximum of about 69 MPa in the curved portion where the bending occurred. Therefore, the die was designed based on the simulation results, and the inner fin die was installed on the 400-ton capacity press. After that, the inner fin fabrication experiment was conducted under the same condition as the simulation. Crack was not found from the curved portion of the concavo-convex of the inner fin. The profile of the concavo-convex of the prepared inner fin measured 6.7~6.8 mm in depth, 2.65~2.7 mm in width, and 0.3 mm in thickness.

• Computers and Concrete
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• v.22 no.6
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• pp.527-538
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• 2018

Buckling of longitudinal bars is a brittle failure mechanism, often recorded in reinforced concrete (RC) structures after an earthquake. Studies in the literature highlights that it often occurs when steel is in the post elastic range, by inducing a modification of the engineered stress-strain law of steel in compression. A proper evaluation of this effect is of fundamental importance for correctly evaluating capacity and ductility of structures. Significant errors can be obtained in terms of ultimate bending moment and curvature ductility of an RC section if these effects are not accounted, as well as incorrect evaluations are achieved by non-linear static analyses. This paper presents a numerical investigation aiming to evaluate the engineered stress-strain law of reinforcing steel in compression, including second order effects. Non-linear FE analyses are performed under the assumption of local buckling. A role of key parameters is evaluated, making difference between steel with strain hardening or with perfectly plastic behaviour. Comparisons with experimental data available in the literature confirm the accuracy of the achieved results and make it possible to formulate recommendations for design purposes. Finally, comparisons are made with analytical formulations available in the literature and based on obtained results, a modification of the stress-strain law model of Dhakal and Maekawa (2002) is proposed for fitting the numerical predictions.