• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.206-211
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• 2015

Recently, for UHPC (Ulta High Performance Concrete) which is researched actively, as the tensile strength is absolutely influenced on the content of steel fiber, in this paper, experiments of compressive strength, elasticity modulus and tensile strength were performed according to compressive strength and content of steel fiber as variables. By the test results, compressive strength, elasticity modulus and tensile strength are proportioned and have a good correlation and according to content of steel fiber, compressive and tensile strength are also proportioned and have a good correlation. In case of elasticity modulus, the difference between test and present design code is not large, so it is possible to adapt to present design code. On the other hand, in case of tensile strength, as there is no specification of present design code, new prediction equation is proposed by using nonlinear regression analysis and the proposed equation have a good correlation to test results.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.103-111
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• 2007

Experimental study was carried out to investigate the structural performance of composite beams with steel fiber concrete and angle. For this purpose, seven specimens composed of two RC beams with or without steel fiber and five composite beams with steel fiber and angle were constructed and tested. All specimens had no web shear reinforcement. Main variables for the specimens were tensile reinforcement ratio and fiber volume fraction. Based on the test results, structural performance such as strength, stiffness, ductility and energy dissipation capacity was evaluated and compared with the predicted strength. The prediction of flexure and shear strength gives a good relationship with the observed strength. The strength, ductility and energy dissipation capacity are increased, as the fiber volume fraction is increased. Meanwhile, high tensile reinforcement ratio resulted in the reduction of ductility and energy dissipation capacity for the composite beams.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.4
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• pp.49-60
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• 2010

The actual hysteretic behavior of structural elements and systems is smooth. Smooth hysteretic behavior is more representative of actual behavior than bi-linear or piece-wise linear stiffness degrading models. The strength reduction factor in seismic design is used to reduce the elastic strength demand to design levels. In this study, the effect of smoothness on the strength reduction factor is evaluated for several smooth hysteretic systems subjected to near-fault and far-fault earthquakes. For design purposes, a simple expression of the strength reduction factor considering hysteretic smoothness and earthquake characteristics, represented as near-fault and far-fault earthquakes, is proposed. The strength reduction factors calculated by the proposed simple formulation are more similar to the factors directly obtained from inelastic response spectrum analyses than those calculated by several existing formulas.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.53-60
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• 2024

Compressive strength in concrete has many affecting parameters and varies with exposure conditions. Although the concrete has same mix proportions, its properties are different with exposure conditions, and sea-environment can be classified into three groups such as tidal, atmospheric, and sea submerged region particularly. In this study, compressive strength was evaluated on 7-year-cured concrete and the results from previous equations (KDS, ACI, CEB, and JSCE) were compared with them. Furthermore the strength and carbonation progress were evaluated on concrete cured for 7 years exposed to three different sea environment. Three levels of w/c (water to cement) ratio (0.37, 0.42, and 0.47) and three different exposure conditions (tidal, atmospheric, and submerged) were considered. The results from wet-cured condition are all higher than those from the previously proposed equations, and the results from different sea exposure conditions (tidal, atmospheric, and submerged region) were lower than those from wet-cured condition. A reduction of strength was evaluated with increasing w/c ratio and the minimum strength was evaluated in the sea-submerged conditions. Several experimental constants applicable to the previous equations were obtained from regression analysis since the strength change with w/c ratios were not considered in those equations. Regarding carbonation depth with different exposure conditions, higher carbonation depth clearly was observed with increasing w/c ratios, and evaluated in the order of atmospheric, submerged, and tidal region. Considerable carbonation depth was observed in submerged and tidal region due to sulfate ion and dissloved carbon dioxide as well.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.365-373
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• 2016

Ultra-High-Performance Steel Fiber-Reinforced Concrete (SUPER Concrete) exhibits improved compressive and tensile strengths far superior to those of conventional concrete. These characteristics can significantly reduce the cross sectional area of the member and the anchorage strength of a headed bar is expected to be improved. In this study, the anchorage strengths of headed bars with $4d_b$ or $6d_b$ embedment length were evaluated by simulated exterior beam-column joint tests where the headed bars were used as beam bars and the joints were cast of 120 or 180 MPa SUPER Concrete. In all specimens, the actual yield strengths of the headed bars over 600 MPa were developed. Some headed bars were fractured due to the high anchorage capacity in SUPER Concrete. Therefore, the headed bar with only $4d_b$ embedment length in 120 MPa SUPER Concrete can develop a yield strength of 600 MPa which is the highest design yield strength permitted by the KCI design code. The previous model derived from tests with normal concrete and the current design code underestimate the anchorage capacity of the headed bar anchored in SUPER Concrete. Because the previous model and the current design code do not consider the effects of the high tensile strength of SUPER Concrete. From a regression analysis assuming that the anchorage strength is proportional to $(f_{ck})^{\alpha}$, the model for predicting anchorage strength of headed bars in SUPER Concrete is developed. The average and coefficient of variation of the test-to-prediction values are 1.01 and 5%, respectively.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.335-338
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• 2009

일반적으로 비중이 큰 철광석이나 석탄 등을 운반하는 선박화물선의 호퍼 너클 이음부는 여러 판이 용접되어 복잡한 형상을 가지고 있어 응력이 집중되어지므로 피로강도평가 시 많은 문제점이 노출되는 구간이다. 이번 연구에서는 기존 sloping 방식의 호퍼 너클 이음 부를 갖는 180k 산적화물선 표준 모델과 제안 되어진 round 방식의 호퍼 너클 이음 부를 갖는 산적화물선에 대하여 구조강도평가와 피로강도평가를 수행하였다. 이때 합리적인 비교를 위하여 제안되어진 모델은 기존의 표준 모델의 화물창과 발라스트창의용적이 일치하도록 제안하였다. 또한 CSR을 기반으로 한 하중들에 대하여 허용응력과 25년 피로수명을 만족하도록 구조부재를 결정하였으며 피로강도평가 결과를 바탕으로 호퍼 너클부의 변화에 따른 선각 중량과 상대 건조 비 개념을 이용하여 보다 효율적인 구조를 제시 하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.81-90
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• 2008

This paper concerns the flexural capacity of reinforced concrete beams with ultra-high performance cementitious composites(UHPCC). It was investigated if the existing equations to estimate the flexural capacity of reinforced fiberous concrete beams are applicable with the experiments including lightly reinforced concrete beams. The reinforcing effect when the steel fiber reinforced concrete was used in beams was also estimated. The results showed that the equation to predict the flexural capacity of reinforced steel fiber concrete by ACI 544 committee didn't have a good agreement with the test results and underestimated the flexural capacity in especially lightly reinforced beams with under 1.5% reinforcement ratio. the enhancement of flexural capacity was quite considerable in lightly reinforced beams when the steel fiber reinforced concrete was used. A equation to predict the reinforcing effect of steel fiber in reinforced steel fiber beams was developed. the equation was proposed as a function of both the characteristics of steel fiber and reinforcement ratio.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2195-2209
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• 2013

The effective strength of concrete struts must be determined accurately for the reliable strut-tie model analysis and design of structural concrete. In this study, the equations of the effective strength, which are useful for the three types of determinate and indeterminate strut-tie models of reinforced concrete deep beams employed in current design codes, are proposed. The effects of shear span-to-effective depth ratio, compressive strength of concrete, and flexural and shear reinforcement ratios are reflected in the development of the proposed equations. To examine the appropriateness of the proposed equations, the strengths of 241 reinforced concrete deep beams, all tested to shear failure, are evaluated by using the three types of strut-tie models with the existing and proposed equations.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.738-740
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• 2012

최근 변단면 거더의 경제성을 고려하여 장경간 거더 교량과 강골조 구조물에 변단면보의 사용이 증가하고 있으며, 고강도 강의 등장으로 인해 변단면보의 정확한 좌굴 강도의 평가가 매우 중요시 되고 있다. 본 논문에서는 기존에 연구된 탄성 횡-비틀림 좌굴 강도에 관한 연구를 바탕으로하여 별로 비탄성 구간에 비지지 길이가 존재하는 일축대칭 I형 변단면보의 횡-비틀림 좌굴 강도 해석을 실시하였다. 해석에는 유한요소해석프로그램인 ABAQUS(2007)가 사용되었으며, MINITAB(2006)을 이용하여 간편한 설계식을 제안하고 있다. 일단 계단식 단면을 가지는 보에 대하여 고려하였으며, 플랜지 길이 방향 비, 너비방향 비, 두께의 비로 계단식 I형 보를 나타내었다. 집중 하중을 적용시켰으며 비선형 해석을 위해 잔류응력 및 초기변형과 재료비선형을 고려하였다. 본 연구 결과에서 제안된 식은 향후 다양한 하중이 작용하는 비탄성 횡-비틀림 좌굴 강도에 대한 연구에 많은 도움이 될 것이다.

• Culinary science and hospitality research
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• v.16 no.5
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• pp.208-220
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• 2010

This study investigates the influence of the attractive dining space on customers' restaurant evaluation, using an experiment research method. It also examines whether the perceived risks in purchasing and the affect intensity moderate the effect of the attractive dining space on the restaurant evaluation. Service quality and purchasing intention are set up as a dependant variable in oilier to figure out the effect of the dining space. The summary of the research result is as follows. First, an attractive dining space induces more positive evaluation of service quality and increases purchasing intention. Second, an attractive dining space has more significant influence on the service quality and the purchasing intention of customers in the purchasing situation of high level of perceived risk than in the purchasing situation of low level of perceived risk. Third, it is shown that personal variable such as affect intensity moderates the effect of an attractive dining space on the service quality perception and the purchasing intention.