• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1829-1836
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• 2010

The district heating system distributes the heat generated from a cogeneration plant to wider locations. In this process, the district heating pipe (DHP) is subjected to internal and external loadings. The internal loadings are generally caused by the operating conditions such as water temperature and internal pressure. Frictional interactions between the pipes and the soil contribute to the external loadings. Thus, investigation of the mechanisms of failure of DHPs will help to guarantee both mechanical stability and heating efficiency. In this study, we investigate the local buckling of DHPs using limit state design (LSD). Two methods are considered: the use of the limit state for the width-thickness ratio and the use of the limit state for the strain. The results are used to confirm that the DHP is stable under local buckling. Finally, we suggest a minimum preheating temperature for avoiding local buckling.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.107-117
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• 2004

This paper is to investigate the reinforcing effects of newly devised Tire-cell mat made of waste tires in sand. Parametric study on number of connection bolts between Tirecells, relative density of sand, embedded depth, number of reinforced layers and width of Tirecell mat was made by using plate loading tests. It is found that the number of connection bolt was enough to maintain the given pressure. The bearing capacity ratio(BCR), which is defined as the rate of ultimate bearing capacity of reinforced soil to that of unreinforced soil, is the highest at the lowest density. And the reinforcing effect can be obtained in case of embedded depth within 1.0B, where B is loading width. Also settlement reduction is the highest at the lowest density of sand. The effect of number of Tirecell reinforced layers with 0.4B to 0.5B interval is limited to 2 layers and further reinforcing effects can not be obtained beyond 3 layers. Especially, the bearing capacity increased remarkably at 1 layer of reinforcement and the degree of increase was small from 1 layer to 2 layers of reinforcement. The effect of mat width of Tirecell was not significant because of high stiffness of Tirecell although the maximum bearing capacity was shown at the 2.0B mat width and the reinforcing effects of Tirecell, in general, was prominent compared with those of commercial Geoweb.