• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.11-18
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• 2007

A laboratory investigation was conducted to characterize the flexural fatigue behavior of high performance fiber reinforced cement mortar. Five specimens for statics flexural test and fourteen specimens for the flexural fatigue test were made based on the fiber mixing ratio. Static flexural tests were firstly performed to obtain magnitudes of static failure loads and stress levels before flexural fatigue tests. The flexural fatigue behaviors were investigated based on the stress level and fiber mixing ratio. Also, the equations for the interrelation of the flexural fatigue stress levels with the number at loading cycle were proposed.

• Steel and Composite Structures
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• v.18 no.4
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• pp.925-946
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• 2015

This paper presents a new cost-effective hybrid GFRP-Concrete deck system that the GFRP panel serves as both tensile reinforcement and stay-in-place form. In order to understand the fatigue behavior of such hybrid deck, fatigue test on a full-scale specimen under sagging moment was conducted, and a series of static tests were also carried out after certain repeated loading cycles. The fatigue test results indicated that such hybrid deck has a good fatigue performance even after 3.1 million repeated loading cycles. A three-dimensional finite element model of the hybrid deck was established based on experimental work. The results from finite element analyses are in good agreement with those from the tests. In addition, flexural fatigue analysis considering the reduction in flexural stiffness and modulus under cyclic loading was carried out. The predicted flexural strength agreed well with the analytical strength from finite element simulation, and the calculated fatigue failure cycle was consistent with the result based on related S-N curve and finite element analyses. However, the flexural fatigue analytical results tended to be conservative compared to the tested results in safety side. The presented overall investigation may provide reference for the design and construction of such hybrid deck system.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.62-65
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• 2000

Potentially significant engineering advantages can be gained by the incorporation of steel fibers in tension-weak concrete. A variety of tests have been developed to measure and quantify the improvements achievable in steel fiber reinforced concrete. An objective of the study is to experimentally investigate the flexural fatigue behavior of steel-reinforced concrete with a experimental variables such as steel fiber types. To predict the behavior of steel reinforced structural componets under fatigue conditions.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.2
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• pp.117-126
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• 2002

Concrete containing discontinuous discrete steel fiber in a normal concrete is called steel fiber reinforced concrete(SFRC). Tensile as well as flexural strengths of concrete could be substantially increased by introducing closely spaced fibers which delay the onset of tension cracks and increase the tension strength of cracks. However, many properties of SFRC have not been investigated, especially properties on repeated loadings. Thus, the purposes of this dissertation is to study the flexural fatigue characteristics of SFRC considering cumulative damage. A series of experimental tests such as compressive strength, splitting tensile strength, flexural strength, flexural fatigue, and two steps stress level fatigue were conducted to clarify the basic properties and fatigue-related properties of SFRC. The main experimental variables were steel fiber fraction (0, 0.4, 0.7, 1, 1.5%), aspect ratio (60, 83). The principal results obtained through this study are as follows: The results of flexural fatigue tests showed that the flexural fatigue life of SFRC is approxmately 65% of ultimate strength, while that of plain is less than 58%. Especially, the behavior of flexural fatigue life shows excellent performance at 1.0% of steel-fiber volume fraction. The cumulative damage test of high-low two stress levels is within the value of 0.6 ∼ 1.1, while that of low-high stress steps is within the value of 2.4 ∼ 4.0.

• Magazine of the Korea Concrete Institute
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• v.5 no.3
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• pp.179-186
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• 1993

본 연구는 무근 폴리에스터 폴리머 콘크리트보의 휨피로 거동을 구명키 위한 것으로서 초기균열깊이와 높이의 비 (a/h)를 0, 0.2, 0.4로 하고 응력수준을 45%, 55%, 65%로 하여 피로 시험을 실시한 것이다. 그 결과 초기균열깊이가 커질수록 피로수명이 짧아졌으며, 피로수명비에 따른 휨인장변형도는 균열깊이가 클수록 작아졌다. 또한 휨탄성계수는 피로수명비 0.2에서 0.6정도까지는 선형적인 변화를 보였으나, 초기와 말기에는 비선형적인 변화를 보여주었다. 그리고 응력수준과 균열깊이가 커질수록 취성적인 성질이 더 크게 나타남을 알 수 있었다.

• Journal of Industrial Technology
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• v.19
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• pp.163-172
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• 1999

This study is conducted on the flexural toughness and flexural fatigue test to fine the mechanical properties of steel fiber reinforced rapid-set cement concrete. Experimental investigation is examined according to fiber contents(0, 0.4, 0.7, 1.0, 1.5%), fiber aspect ratio(58, 60, 83), fiber type (hooked, crimped fiber), and cement type (normal portland & rapid-set cement). The principal results obtained through this study are as follows; toughness and fatigue resistance tend to considerably increase with fiber contents, fiber aspect ration. And hooked fiber is improved better than crimped fiber. Concrete using rapid set cement is increased strength properties compared with concrete using normal portland cement, but relative strength properties behavior and fatigue resistance show a tendency to decrease a little.

• International Journal of Concrete Structures and Materials
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• v.8 no.1
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• pp.43-59
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• 2014

Many bridges are subject to lateral damage for their girders due to impact by over-height vehicles collision. In this study, the optimum configurations of carbon fiber reinforced polymers (CFRP) laminates were investigated to repair the laterally damaged prestressed concrete (PS) bridge girders. Experimental and analytical investigations were conducted to study the flexural behavior of 13 half-scale AASHTO type II PS girders under both static and fatigue loading. Lateral impact damage due to vehicle collision was simulated by sawing through the concrete of the bottom flange and slicing through one of the prestressing strands. The damaged concrete was repaired and CFRP systems (longitudinal soffit laminates and evenly spaced transverse U-wraps) were applied to restore the original flexural capacity and mitigate debonding of soffit CFRP longitudinal laminates. In addition to the static load tests for ten girders, three more girders were tested under fatigue loading cycles to investigate the behavior under simulated traffic conditions. Measurements of the applied load, the deflection at five different locations, strains along the cross-section height at mid-span, and multiple strains longitudinally along the bottom soffit were recorded. The study investigated and recommended the proper CFRP repair design in terms of the CFRP longitudinal layers and U-wrapping spacing to obtain flexural capacity improvement and desired failure modes for the repaired girders. Test results showed that with proper detailing, CFRP systems can be designed to restore the lost flexural capacity, sustain the fatigue load cycles, and maintain the desired failure mode.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.4 s.74
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• pp.337-345
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• 2006

In this study, to evaluate fatigue characteristics of developed composite bridge deck, compression fatigue test at girder support and flexural fatigue test for the 2.8m-long flexural test model were carried out. For the test specimen, DB 24 truck load was applied up to 2,000,000 cycles. In the compression fatigue test, behavior at deck tube and its bonded connection were evaluated. In the flexural fatigue test, deck behavior at mid-span and girder connection were evaluated.

• Structural Engineering and Mechanics
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• v.40 no.6
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• pp.847-866
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• 2011

The objective of this study was to experimentally investigate the bond-related tension stiffening behavior of flexural reinforced concrete (RC) beams made with lightweight aggregate concrete (LWAC) under various high-cycle fatigue loading conditions. Based on strain measurements of tensile steel in the RC beams, fatigue-induced degradation of tension stiffening effects was evaluated and was, compared to reinforced normal weight concrete (NWC) beams with equal concrete compressive strengths (40 MPa). According to applied load-mean steel strain relationships, the mean steel strain that developed under loading cycles was divided into elastic and plastic strain components. The experimental results showed that, in the high-cycle fatigue regime, the tension stiffening behavior of LWAC beams was different from that of NWC beams; LWAC beams had a lesser reduction in tension stiffening due to a better bond between steel and concrete. This was reflected in the stability of the elastic mean steel strains and in the higher degree of local plasticity that developed at the primary flexural cracks.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.623-624
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• 2006

The behavior of hardmetals under cyclic loads is investigated. Unnotched specimens were employed to obtain practical information regarding fatigue in hardmetals. All the tested hardmetals exhibit an increase in the number of cycles until failure with a decrease in the maximum stress, i.e., the hardmetals exhibit a high fatigue sensitivity. The fatigue strength increases with the cobalt content. Although distinct fatigue limits, as observed in metals, cannot be observed, the calculated fatigue limit stress at $10^7$ cycles is found to be approximately 70% of the flexural strength, and the stress value exhibits a linear relationship with the flexural stress.