• Computers and Concrete
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• v.21 no.3
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• pp.279-289
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• 2018

Hydration heat and thermal induced cracking have always been a fatal problem for massive concrete structures. In order to study a massive reinforced concrete wall of a storage tank for liquefied natural gas (LNG) during its construction, two mock-ups of $0.8m{\times}0.8m{\times}0.8m$ without and with metal corrugated pipes were designed based on the actual wall construction plan. Temperature distribution and strain development of both mock-ups were measured and compared inside and on the surface of them. Meanwhile, time-dependent thermal and mechanical properties of the concrete were tested standardly and introduced into the finite-element (FE) software with a proposed hydration degree model. According to the comparison results, the FE simulation of temperature field agreed well with the measured data. Besides, the maximum temperature rise was slightly higher and the shrinkage was generally larger in the mock-up without pipes, indicating that corrugated pipes could reduce concrete temperature and decrease shrinkage of surrounding concrete. In addition, the cooling rate decreased approximately linearly with the reduction of heat transfer coefficient h, implying that a target cooling curve can be achieved by calculating a desired coefficient h. Moreover, the maximum cooling rate did not necessarily decrease with the extension of demoulding time. It is better to remove the formwork at least after 116 hours after concrete casting, which promises lower risk of thermal cracking of early-age concrete.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.1
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• pp.7-12
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• 2017

Most of existing buried pipes are composed of reinforced concrete. Reinforced concrete pipes have many problems such as aging, corrosion, leaking, etc. The polyethylene (PE) pipes have advantages to solve these problems. The plastic pipes buried underground are classified into a flexible pipe. National standard that has limited the long-term vertical deformation of the pipe to 5% for flexible pipes including PE pipe. This study presents a prediction for the long-term behavior of the polyethylene pipe based on ASTM D 5365. This prediction method is presented to estimate by using the statistical method from the initial deflection measurement data. We predict the behavior of long-term performance on the double-wall pipe and multi-wall pipe. As a result, it was found that the PE pipe will be sound enough more than 50 years if the compaction of soil around the pipe is more than 95% of the standard soil compaction density.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.198-201
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• 2003

The R.C Building will be superannuated as time passes. This program is generated by propagation of cracks. In order to manage such cracks, time and efforts, expense, etc. are required. In this study, glass sensors were embedding in a model beam and column and leakage of fluorescence and adhesive material was investigated. Further, currents in glass pipe were observed to find the leakage of liquid in glass pipes. Progressive cracks generated by cause the fracture of glass pipes. Therefore, the liquid become to flow and electric current stops, and the cracked part of the member can be found easily. Moreover, the adhesive delays progressive cracking system that responds in air, and the life of a structure can be made to extend. The purpose of this research is to develop of low price sensors that can perform of self-diagnosis in addition to ability of concrete repair concrete to damage.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.69-70
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• 2014

For the curved concrete track construction of 2018 winter Olympic sliding center in Pyeongchang, in this study proposed the digital fabrication technology using CNC. This method can control the 3D geometries of the curved concrete structure based on the digital design. Conventional method generates the construction errors because this method fabricates many temporary zig bar using 1:1 full size drawing for install frozen pipes and sets up each zig bars at the construction site. Propose method is effective to ensure the precise fabrication and construction of zig bars. Also this method can eliminate errors of the frozen pipes position and curved concrete construction.

• International Journal of Concrete Structures and Materials
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• v.18 no.3E
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• pp.161-164
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• 2006

Cellulose fiber reinforced cement(CFRC) pipe has been gradually introduced in the pipe market as a replacement of previously popular asbestos cement pipes. Since CFRC pipe is still relatively unknown in the pipe market, there are great concerns for the design and application in practice related to the time-dependent behavior of CFRC under long-term sustained loading. This paper presents an experimental investigation of the time-dependent behavior of cellulose fiber reinforced cement(CFRC) pipe. A total of six CFRC pipes were tested under various loading levels, and their vertical deformation was recorded to understand the characteristics of the time-dependent behavior. Based on the test results, a factor of safety(FS) of 1.82 is proposed, and a regression factor(R) of 1.88 is estimated for the application of CFRC pipes in practice.

• Magazine of the Korean Society of Agricultural Engineers
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• v.14 no.2
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• pp.2593-2602
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• 1972

Plastic pipes Wrapped with synthetic filter are recently used for drainage or Collecting of Underground water. But it's use is possible only for small size of diameter less than 300mm, because large size plastic pipes are not readily availabe. For large diameter infiltration gallery, porous concrete pipes are now used, but it's heavy weight brings difficulties in making, moving and setting of the pipes. With it's conventional method of filter setting, fine sands are brought into the pipes to make trouble to lifting pumps and channels Therefore, initial construction cost and maintenance cost become high. To solve-this problem, new method is developed and tested. Small PVC pipes(diameter 14mm) are assembled at the site of construction to newly devised I beam type circls. The size of circular inpiltration gallery is optionally determined by I beam type circle which support small PVC pipes and is made of PVC amterial. This gallery are wrappd with syntheitc filter to prevent sand instruction. In this test, the diameter of 300, 400, 500mm were used. I beam type circles were made with PVC plated with thickness. t=6, 9, 12mm. Water quantity collected through the PVC circulor gallery are measured and the strengths of the gallery. 1. Allowable setting depth of gallery pipe below graund for the case of t=6mm, D=500mm is 2.72m. 2. Collected water quantity depends on soil texture, depth of water grandient of water surface, filter material angle of setting etc. 3. About 126% of water quantity collected from the one gallery pipe measured in two gallery pipes of two parallel installation.

• Advances in concrete construction
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• v.9 no.3
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• pp.327-335
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• 2020

Concrete pipes are considered important structures playing integral role in spread of cities besides transportation of gas as well as oil for far distances. Further, concrete structures under seismic load, show behaviors which require to be investigated and improved. Therefore, present research concerns dynamic stress and strain alongside deflection assessment of a concrete pipe carrying water-based nanofluid subjected to seismic loads. This pipe placed in soil is modeled through spring as well as damper. Navier-Stokes equation is utilized in order to gain force created via fluid and, moreover, mixture rule is applied to regard the influences related to nanoparticles. So as to model the structure mathematically, higher order refined shear deformation theory is exercised and with respect to energy method, the motion equations are obtained eventually. The obtained motion equations will be solved with Galerkin and Newmark procedures and consequently, the concrete pipe's dynamic stress, strain as well as deflection can be evaluated. Further, various parameters containing volume percent of nanoparticles, internal fluid, soil foundation, damping and length to diameter proportion of the pipe and their influences upon dynamic stress and strain besides displacement will be analyzed. According to conclusions, increase in volume percent of nanoparticles leads to decrease in dynamic stress, strain as well as displacement of structure.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.275-280
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• 1999

It was analysed the effect of pipe cooling as a measure to avoid thermal cracks due to the heat of hydration during the curing process of a massive prestressed concrete (PSC) slab. PSC slab has a complex three-dimensional shape of which the maximal and minimal thicknesses of cross-section were 2.8 and 0.95m, respectively. Steel pipes of which the diameter was 1 inch were employed for cooling. The horizontal and vertical distances between the contiguous pipes were 0.5 and 0.6m, respectively. One the four layers of cooling pipe were arranged according to the thickness of cross-section. Temperature distribution was calculated by the program developed by the authors, of which the accuracy was verified on a few published papers by the authors. Based on the temperature analysis of the cross-section which had four layers of cooing pipe, the maximum temperature of concrete interior was 54.2$^{\circ}C$ and the maximum differenced between the interior and surface temperatures of concrete was 14.$0^{\circ}C$ and, thereby, the thermal cracking index was 1.1. Upon the stress analysis, the thermal cracking index was 0.92 and the probability of thermal-crack development was 52%. Therefore, it was expected to make it possible to reduce the probability of thermal-crack development in a massive PSC slab by adopting pipe cooling.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.373-378
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• 2000

Zinc galvanized steel plates(sections) of annular corrugations have been used in buried steel culverts. These structures are referred to by a variety of names such as flexible pipes, buried pipes, soil-steel bridges, corrugated steel culverts, and etc. Buried corrugated steel structures show flexible behaviour under the soil load. compared with concrete box structures. Finite element analysis was performed to suggest the reasonable connecting method between the flexible steel culverts and the rigid concrete box. It was predicted that perfectly constrained connections could induce the excessive stress in steel plates. Therefore elastic bearing connections that allow vertical displacement at the connecting point were applied.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.164-172
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• 2008

The heat of hydration for early aged mass concrete induces high temperature with the hydration. Control of the temperature difference across a section is an effective strategy to minimize the hydration heat induced cracks for the structures where internal restraint is dominant. The current prevention methods for hydration cracking show some limitations for the control of thermal gradients, and these limitations could make micro and macro cracks in surface and core of concrete. Especially cooling methods can decrease the increasing hydration temperature, but it can not prevent the problem while decreasing temperature. Consequently heating pipes are added simultaneously with the cooling pipes in order to control the temperature gradients between core and surface of the concrete, followed by the finite element analysis (FEA). Based on the FEA, the proposed method using cooling pipe and heating pipes together has been found to be an effective alternative in thermal gradient control, in terms of controlling temperature induced cracks significantly.