• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.458-463
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• 2000

Recently, there are increasing much concerns about repair and rehabilitation works for aged Concrete Structures which had been constructed on around the 1970's for rapid economic growth in Korea. In particular, it is believed that there are many aged concrete slabs for Highway bridges in these days. Thus new construction method of concrete slabs are strongly needed to minimize the traffic congestion during the repair works. The objective of this research is to develop the new constructional method of concrete slab in bridge structure, which can contribute to minimize the traffic congestion to be occurred during the repair and rehabilitation works of aged concrete slab, and can also assure the reliable quality through the minimization of in-situ works at the site. I-beams with punch holes will be manufactured in accordance with the specification in the factory, and will be preassembled into the panel. After erecting the preassembled panels in the site, concrete will be poured into the slab panel. This research is to investigate physical properties of I-Beam with punch holes itself, and then to investigate structural properties of assembled I-Beam panels through static and fatigue test, of which result can be utilized for the development of the new constructional method for concrete slab in bridge structure.

• Computers and Concrete
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• v.33 no.3
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• pp.301-308
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• 2024

This paper proposes a numerically-based methodology to implicitly model irreversible deformations in concrete through a damage model. Plasticity theory is not explicitly employed, although resemblances are still present. A scalar isotropic damage model is adopted and the damage variable is split in two: one contributing for stiffness degradation (cracking) and other contributing for irreversible deformations (plasticity). The proposed methodology is thermodynamically consistent as it consists in a damage model rewritten in different terms. Its Finite Element coding is presented, indicating that minor changes are necessary. It is also demonstrated that nonlinear algorithms are unnecessary to model concrete cracking and plasticity. Experimental data from direct tension and four-point bending tests under cyclic loading are compared to the proposed methodology. A numerical case study of a low-cycle fatigue is also presented. It can be concluded that the model is simple, feasible and capable to capture the essentials concerning cracking and plasticity.

• Computers and Concrete
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• v.19 no.3
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• pp.243-256
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• 2017

Epoxy-coated reinforcing bars are widely used to protect the corrosion of the reinforcing bars in the RC elements under their in-service environments and external loads. In most field surveys, it was reported that the corrosion resistance of the epoxy-coated reinforcing bars is typically better than the uncoated bars. However, from the experimental tests conducted in the labs, it was reported that, under the same loads, the RC elements with epoxy-coated reinforcing bars had wider cracks than the elements reinforced with the ordinary bars. Although this conclusion may be true considering the bond reduction of the reinforcing bar due to the epoxy coating, the maximum service loads used in the experimental research may be a main reason. To answer these two phenomena, service performance of 15 RC beam specimens with uncoated and epoxy-coated reinforcements under different fatigue loads was experimentally studied. Influences of different coating thicknesses of the reinforcing bars, the fatigue load range and load upper limit as well as fatigue load cycles on the mechanical performance of RC test specimens are discussed. It is concluded that, for the test specimens subjected to the comparatively lower load range and load upper limit, adverse effect on the service performance of test specimens with thicker epoxy-coated reinforcing bars is negligible. With the increments of the coating thickness and the in-service loading level, i.e., fatigue load range, load upper limit and fatigue cycles, the adverse factor resulting from the thicker coating becomes noticeable.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.507-512
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• 1999

In recent years, glassfibers have been used for strengthening in RC structure because of low material cost and easy repairing work. The purpose of this study is to experimentally and analytically investigate the effect of glassfibers for enhancing the capacity of RC flexural beams and shear beams. The experimental result shows that yield and ultimate strength of RC flexural beam with glassfibers are increased by approxiamate 13% and 26%, comparing with those for without glassfibers, and also ultimate strength of RC shear beam with glassfibers are increased by 34%, comparing with those for without glassfibers.

• Steel and Composite Structures
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• v.50 no.6
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• pp.659-674
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• 2024

Casting Ultra High-Performance Concrete (UHPC) on an orthotropic steel deck and forming a composite action by connectors could improve the steel deck fatigue performance. This study presents the mechanical performance of a proposed post-combination connection between UHPC and steel, which had a low constraint effect on UHPC shrinkage. A total of 10 push-out tests were conducted for static and fatigue performance investigations. And the test results were compared with evaluation methods in codes to verify the latter's applicability. Meanwhile, nonlinear simulation and parametric works with material damage plasticity models were also conducted for the static and fatigue failure mechanism understanding. The static and fatigue test results both showed that fractures at stud roots and surrounding local UHPC crushes were the main failure appearances. Compared with normally arranged studs, group arrangement could result in reductions of static stud shear stiffness, strength, and fatigue lives, which were about 18%, 12%, and 27%, respectively. Compared with the test results, stud shear capacity and fatigue lives evaluations based on the codes of AASHTO, Eurocode 4, JSCE and JTG D64 could be applicable in general while the safety redundancies tended to be smaller or even insufficient for group studs. The analysis results showed that arranging studs in groups caused obviously uneven strain distributions. The severer stress concentration and larger strain ranges caused the static and fatigue performance degradations of group studs. The research outcome provides a very important basis for establishing a design method of connections in the novel post-combination steel-UHPC composite deck.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.57-62
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• 2020

Concrete pump cars are a type of construction equipment that continuously supplies concrete using hydraulic pressure. When manually casting concrete, there may be a problem in the final quality of the concrete due to differences in the degree of cure between the pre-poured and subsequent concretes. Concrete pump cars are the most efficient machines to supply concrete in the shortest time; however, it is difficult to calculate their margin of safety during operation. In this paper, we verified the structural safety of the concrete pump car using a static/dynamic analysis at various position angles. Next, these results were compared with experimental results; strains using strain gages were compared with the strains measured using FEM software to verify the static analysis. In addition, the maximum displacement during the pumping was measured and it was used for fatigue analysis to evaluate the dynamic structural safety.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.317-320
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• 2005

In recent years, according to the development of construction technique, the constructions of longer span bridges, taller buildings, deeper offshore structures, and other megastructures are calling for construction materials with increasingly improve properties. So, the demand for high-strength concrete(HSC) have been increased and many new structures have been built using HSC with the compressive strength about 100MPa. However, it is well-known that as the strength of concrete increases, concrete becomes more brittle. Recent studies, however, shown that the brittleness of HSC can be improved by adding some fibers to the concrete. Especially steel fiber reinforced concrete(SFRC) can be used in this case. Many research works have shown that SFRC results in better crack and deflection control, higher shear strength, improved fatigue performance, increased impact strength, reformed flexural strength, advanced fracture toughness and enhanced postcracking resistance. So, this is a study on the long-term response of SFRC applied to HPC about 40MPa. Therefore, in this study, the test results of twenty-six high-strength concrete specimens and steel fiber-reinforced concrete specimens, with steel fiber content of 1 $\%$ by volume were presented. And the results are analyzed by using of the factors of time, mix properties, humidity/temperature, and loading conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.917-920
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• 2006

This paper reports a comparative study for performance evaluation guidelines for bridge bearings. Guidelines for bridge bearings such as KS, EN1337, AASHTO LRFD, and Japanese code were analyzed. In addition, fatigue tests of elastomeric bearing are being conducted for allowable shear deformation and compressive stress. Based on literature survey and tests, the innovative concept of performance evaluation guidelines for bridge bearings is suggested.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.463-468
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• 2002

Transverse prestressing of bridge decks is an attractive concept with substantial benefits in both economy and crack control in slabs. To evaluate the necessary information for the prestressed long span bridge slab design, a series of static and fatigue tests were peformed. It is shown that the minimum thickness recommendation in Korean Highway Bridge Design Code is too conservative.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.81-86
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• 2014

Composite materials have high specific stiffness, specific strength than existing concrete or steel materials. It has superior dynamic properties when utilizing advantages of material such as Non-corrosive, light weight, non-conducting and it has superior mold ability which can make variable shapes. Thus, in the construction, for using composite materials as construction materials, the study carried out static strength of fiber right angle direction and fatigue performance of FRP deck member. The study is going to deduct S-N curve by analyzing the results comparatively and estimate long-term durability. From now on, the study is going to provide interpretation of FRP member and basic data of design basis, furthermore providing foundation technique of composite materials' application of structural frame is the goal of this study.