• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1081-1094
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• 2014

The strut-tie model approach has proven to be effective in the ultimate analysis and design of structural concrete with disturbed regions. For the reliable analysis and safe design of the structural concrete, however, the effective strengths of concrete struts must be determined accurately. In this study, the equations of the effective strengths of concrete struts, which are useful for the three types of determinate and indeterminate strut-tie models of reinforced concrete corbels, were proposed. The effects of shear span-to-effective depth ratio, the vertical-to-horizontal force ratio, and flexural and horizontal shear reinforcement ratios were reflected in the development of the proposed equations. To examine the appropriateness of the proposed and existing equations, the ultimate strengths of 243 reinforced concrete corbels tested to failure were evaluated by using the three types of corbel strut-tie models.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1065-1079
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• 2014

The ultimate behavior of reinforced concrete corbel is complicated due to the primary design variables including the shear span-to-effective depth ratio a/d, flexural reinforcement ratio, load condition, and material properties. In this study, a simple indeterminate strut-tie model reflecting all characteristics of the ultimate strength and complicated structural behavior is proposed for the design of the reinforced concrete corbels with shear span-to-effective depth ratio of $a/d{\leq}1$. A load distribution ratio, defined as the fraction of applied load transferred by horizontal truss mechanism, is also proposed to help structural designers perform the design of reinforced concrete corbels by using the strut-tie model approaches of current design codes. For the development of the load distribution ratio, numerous material nonlinear finite element analyses of the proposed indeterminate strut-tie model were conducted by changing primary design variables. The ultimate strengths of reinforced concrete corbels tested to failure were evaluated by incorporating the proposed strut-tie model and load distribution ratio into the ACI 318-11's strut-tie model method. The validity of the proposed model and load distribution ratio was examined by comparing the strength analysis results with those by the ACI 318-11's conventional design method and strut-tie model methods of current design codes.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.197-200
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• 2008

The RC corbels with the ratio of shear span-to-effective depth less than 1 are commonly used to transfer loads from beams to columns. The ultimate strengths and structural behaviors of RC corbels are controlled by the shear span-to-effective depth ratio, strength of concrete, shape and quantity of the reinforcement, and geometry of corbels. In this study, a simple indeterminate strut-tie model reflecting all characteristics of the ultimate strengths and complicated structural behaviors is presented for the design of RC corbels. In addition, a load distribution ratio, defined as a magnitude of load transferred by a horizontal truss mechanism, is proposed to help structural designers perform the design of RC corbels by using the strut-tie model approaches of current design codes. The ultimate strengths of 30 RC corbels tested to failure are evaluated by using the ACI 318-05's strut-tie model code for the validity check of the proposed indeterminate strut-tie model and load distribution ratio.

• Journal of the Korean Institute of Gas
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• v.10 no.1 s.30
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• pp.56-60
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• 2006

The connection part (corbel) between bottom slab and side wall in inground LNG storage tank has hinge conditions partly fixed by using anchor bars to reduce stress concentration. The corbel deforms in both radial and vertical directions under load conditions of the LNG tank such as LNG temperature, hydraulic pressure, etc. Membrane is an important part from the viewpoint of design because the deformation of the corbel is transformed directly to the membrane and superposed with other deformations. Behavior of the corbel has been investigated through various sensors to measure temperature, load and displacement. And the test data have been compared with finite element results analysis to propose a more reasonable design of LNG storage tank.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.391-396
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• 2003

The concrete corbels consist of various failure mechanisms such as the yielding of the tension reinforcement, the crushing or splitting from compression concrete struts, and localized bearing or shearing failure under the loading plate. However, predicting those failure mechanisms is very difficult. In this study, the ACI 318-02, the softened strut-tie model approach, and the nonlinear strut-tie model approach are applied to ultimate strength analysis of normal strength concrete corbels tested to failure. From the result of the analysis, an effective analysis and design method of normal strength concrete corbels is suggested.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.544-547
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• 2004

Predicting the failure modes of reinforced concrete corbels is difficult because the reinforced concrete corbels show the shapes of sudden shear failures at even slight deflection. For this reason, an exact analysis method is demanded highly. In this study, the validity of the grid softened strut-tie model method suggested for concrete member analysis was examined through the ultimate strength evaluation of the reinforced concrete corbels tested to failure. The evaluated ultimate strengths by the grid softened strut-tie model method were compared with those by the ACI 318-02 and the softened strut-tie model method.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.373-376
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• 2004

The designer has difficulty due to inadequacy of provisions in the domestic design code and lack of understanding for behavior of D-region. The rectangular shaped corbel consist of various failure mechanisms as the crushing or splitting from compression concrete, and shearing failure under the loading plate. However, predicting those failure mechanisms is very difficult. In this study, rectangular shaped corbel is analyzed and designed by using strut-tie model. Adequacy for the application of strut-tie model is verified by comparison with the way used in current design practice. The results show that strut-tie model can be a rational and an economical design than current conventional design methods.

• Archives of design research
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• v.13 no.4
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• pp.233-242
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• 2000

The traditional image of hydraulic excavator started to change in two ways since 1990. First, post-heavy equipment's visual image was new waves to traditional image of heavy, strong, and wild. They are the negative aspect that excavators have. Another movement of getting rid of its negative image can be found in late-heavy equipment, which was intended to adapt traditional and positive, but off negative images. In 1990s, the design trend is moving from warm/hard to warm/soft, and KOBELCO can be exceptional example that went even further, gone up to cool-soft image. KOBELCO specially aimed 'post- excavator image' strategy, which has been successful. Image of cabin as a human space changed little bit further than outside image. Each company tried to differentiate the design of cabin focusing on its safety. Following paragraphs show specific trend of image change in form, colour, texture, and the composition. Major visual image change in form tries to follow the image of cars and home appliances which are showing the movement from tough and hard image to soft one. Structural change on local image shows the movement from angular edge to edgeless and the movement of cabin's pillar C placed to back of the equipment with gentle inclination. All of these movements are the result of effort to improve traditional excavator's negative image, that top structure is assembled separately, to positive ones. Today's tendency about its color becomes important to apply two different colour styles. Each style has brightness and tone comparison. As an enormous power convey system, it was in common that its brightness comparison was useful because of the alarm of its damage possibility. However, as its colour control and its design have been emphasized gradually, the tone comparison takes a part in an important role, too. As an example, there is an occasion that these comparisons are compromised simultaneously. In the respect of its image creation, its texture treatments make the tendency of being the same as passenger cars. It is caused from its development of the manufacture techniques of from the fabrication method in small business to the press method in big firm. Further, it is also because of its improvement of painting & coating skills. It may prohibit the reflection effect from solar rays. In the point of view of its visual images, it is recognized the prominent tendency that its composition has been gradually decreased. Lots of windows and the frames tends dark-colour as a whole. It is more preferred to have one colour image, but except KOBELCO and HITACHI. As well, there is another high-tendency to improve its standard treatments, especially for its corner and texture treatments.

• Economic and Environmental Geology
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• v.37 no.3
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• pp.291-301
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• 2004

In order to charaterize weathering of chalcopyrite and behavior of dissolved metal ions in waste rocks from Manjang Cu mine, mineralogical studies such as refractive microscope, XRD and SEM/EDS analyses carried out. The weathering was mainly occurred in fractures and edge of the chalcopyrite within the mine waste rocks. The weathering process can be seen to reflect four stages based on the weathering degree of chalcopyrite. The main secondary minerals are goethite, covellite, azurite, malachite and brochantite. Dissolved Cu and As were mainly adsorbed Fe-hydroxide. Poorly crystalline Fe-oxide contains relatively high As contents. In oxdizing condition, the weathering of chalcopyrite mainly occurs along the fracture, while the replacement of chalcopyrite observed mainly in the grain and produced covellite and brochantite. The dissolved metals (Cu, Fe, As) in waste rocks from the abandoned Manjang mine area could attenuate naturally by precipitation, adsorption and replacement reaction.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.689-696
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• 2003

Recently, Appendix A of ACI 318∼02 Code introduced the Strut-and-Tie Model(STM) procedure in shear design of deep flexural members. The STM procedure is widely used in the design of concrete regions where the distribution of longitudinal strains is significantly nonlinear, such as deep beams, beams with large openings, corbels, and dapped-end beams. Experimental study included five high-strength reinforced concrete deep beams with different detailing schemes for the horizontal and vertical reinforcement. The specimens were designed as simply supported beams subjected to concentrated loads on the top face and supported on the bottom face. At failure, all specimen exhibited primary diagonal crack running from the support region to the point load. Specimens which had mechanical anchorages(terminators) gives better representation of the load-carrying mechanism than the specimen had standard 90-degree anchorage at failure in deep flexural members. Based on the test results, shear design procedures contained in the ACI 318-99 Code, Appendix A of the ACI 318-02 Code, CSA A23.3-94 Code and CIRIA Guide-2 were evaluated. The Shear design of ACI 318-99 Code, Appendix A of the ACI 318-02 Code and CIRIA Guide-2 shown to be conservative predictions from 10% to 36% in the shear strength of the single-span deep beam which was tested. ACI 318-99 Code was the lowest standard deviation.