• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.183-192
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• 2008

Generally, application of steel pipe pile as deep foundation member needs special requirement for the connection method between steel pipe pile and concrete footing. Even though two types of connection method are suggested in the korea highway bridge code, type-B method is prevalent. In this study, vertical, lateral, and tension loading test are done for two types of type B connection to review stress concentration, formation and behavior of imaginary RC column in the footing. Welding type and hook type as the connection method are considered in this study. Test results show that welding type have the more reserve capacity than hook type and the specimens connected by the welding type behave as the imaginary RC column in the footing. However, the specimens connected by the hook type did not behave as the imaginary RC column in the footing but behave as the hinge.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.650-661
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• 2003

During construction of reinforced concrete building, construction load two times as much as the self weight of a slab, is imposed on the slab, and strength and stiffness of the early-age concrete are not fully developed. As the result, the construction load frequently causes excessive deflection and cracking in the flat plate. The minimum thickness of flat plate specified by the current design codes does not properly address such effect of the construction load. In the present study, a simplified method was developed to calculate the deflection of flat plate affected by the construction load. The proposed method can consider the effects of a variety of design parameters such as the aspect ratio of plate, boundary condition, concrete strength, and construction load. A design equation for the minimum thickness was developed based on the proposed method.

• Land and Housing Review
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• v.4 no.3
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• pp.279-286
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• 2013

Driving a prefabricated pile is the efficient construction method with low cost and excellent bearing capacity charateristics. But pile drinving method has often been changed to bored pile method with mechanical boring due to the unexpected problems occurred in the various domestic ground condition with landfill. So, pile driving method has more uncertainty than the Bored Pile method. This paper proposed LRFD design value which is one of limit states design method for the PHC driven pile used as building foundation to guarantee the reliable design with reduced uncertainty. This paper analysed 221 dynamic load test results(E.O.I.D : 93, Resrike : 128) and the different methods of estimating bearing design(Meyerhof method & SPT-CPT conversion method), and proposed LRFD value for each design reliability Index 2.33 and 3.0 for PHC driven pile. LRFD value of PHC driven pile represents 0.43~0.55 for Meyerhof method and 0.40~0.49 for SPT-CPT conversion method according to the deign reliability index.

• Journal of the Korean GEO-environmental Society
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• v.5 no.3
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• pp.5-15
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• 2004

SIP has been widely used as a low noise and vibration piling method in Korea. But the quality control of SIP was not properly settled down and field workers did not fully understand the principle of SIP method. So not a less troubles were raised at construction site and bearing capacity was not fully mobilized. To settle these problems, Korea National Housing Corporation amended the construction and load test criteria of SIP in 2002. After load tests on the SIPs installed in field according to the new criteria, we found that the bearing capacity in field vs the design load ratio increased and bearing characteristics was enhanced than that installed by the former criteria. To consider the enhanced bearing characteristics in the pile design and determine the adequate design criteria, this paper analyzed the accuracy of design criterion which were commonly used in Korea comparing with the load test results. Analysis result shows that Meyerhof criteria(1976) properly simulates the bearing capacity of SIP installed by the new construction and load test criteria.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.345-356
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• 2010

An alternative design method for interior flat plate-column connections subjected to punching shear and unbalanced moment was developed. Since the slab-column connections are severely damaged by flexural cracking before punching shear failure, punching shear was assumed to be resisted mainly by the compression zone of the slab critical section. Considering the interaction with the flexural moment of the slab, the punching shear strength of the compression zone was evaluated based on the material failure criteria of concrete subjected to multiple stresses. The punching shear strength was also used to evaluate the unbalanced moment capacity of the slab-column connections. For verification, the proposed strength model was applied to existing test specimens subjected to direct punching shear or combined punching shear and unbalanced moment. The results showed that the proposed method predicted the strengths of the test specimens better than current design methods in ACI 318 and Eurocode 2.

• Journal of the Society of Disaster Information
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• v.15 no.4
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• pp.524-530
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• 2019

Purpose: In this paper, we construct a detailed three-dimensional interface element using a three-dimensional analysis program, and evaluate the composite behavior stability of the connector by applying physical properties such as the characteristics of general members and those of reinforced members Method: The analytical model uses solid elements, including non-linear material behavior, to complete the modeling of beam structures, circular flanges, bolting systems, etc. to the same dimensions as the design drawing, with each member assembled into one composite behavior linkage. In order to more effectively control the uniformity and mesh generation of other element type contact surfaces, the partitioning was performed. Modeled with 50 carbon steel materials. Results: It shows the displacement, deformation, and stress state of each load stage by the contact adjoining part, load loading part, fixed end part, and vulnerable anticipated part by member, and after displacement, deformation, The effect of the stress distribution was verified and the validity of the design was verified. Conclusion: Therefore, if the design support of the micro pile is determined based on this result, it is possible to identify the Vulnerable Parts of the composite behavior connector and the degree of reinforcement.

• International Journal of Highway Engineering
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• v.10 no.1
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• pp.135-144
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• 2008

The dynamic loads imposed by moving vehicles have variations in the magnitude due to the surface roughness of the pavement systems and the larger dynamic loads than the design loads may affect the pavement performance. This paper presents variations of the moving dynamic vehicle loads due to the pavement surface roughness. This study was performed as a basic study to apply the pay factor to the surface roughness for the improvement of pavement quality and performance. The profile data was obtained from the old and new pavements and the analysis was performed to investigate the dynamic loads when vehicles move on the pavements having those profiles. The artificial profiles were also developed to find the effects of the vehicle speed, wavelength and amplitude of the surface roughness on the dynamic vehicle loads. The increase in the load magnitude due to the surface roughness affects the stresses and strains of pavements and finally reduces the pavement life. The methodology to obtain the relationship between the surface roughness and the pavement performance was proposed in this study.

• Journal of the Korean Geosynthetics Society
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• v.3 no.4
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• pp.41-48
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• 2004

Recently a method for increasing the bearing capacity by laying the reinforcing materials with three or four layers as a method reinforcing the ground was studied recently. The purpose of this study is to examine the method for increasing shear-strength factor of the ground by reinforcing the ground under the foundation. According a method of wrapping ground with bakk-shape or semicircle-shape by geotextile was developed in this study and it looks likes anaspect that spreading footing exits under spread footing. A simulation loading-test using Aluminum sticks was carried out in order to examine the mechanism about bearing capacity of spread footing reinforced by geotextile. Increase of ultimate bearing capacity was verified in this simulation loading-test when charging loads to spread footing, which is propose from this study, reinforced by geotextile. And moving directions of points of the ground were also checked by grid-type indication method, and the areas where plastic failure appeared were checked by B-shutter photographing.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.657-665
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• 2011

LB-DECK, a precast concrete panel type, is a permanent concrete deck form used as a formwork for cast-in-place concrete pouring at bridge construction site. LB-DECK consists of 60 mm thick concrete slab and 125 mm height Lattice-girders partly embedded in the concrete slab. These decks have been applied to the bridges, which girder spacings are short enough to resist longitudinal cracking caused by construction loads. This paper presents experimental research work conducted to evaluate the cracking load of LB-DECKs designed for long span bridge decks. Twenty four non-composite beams and four composite beams are fabricated considering three design variables of thickness of concrete slab, height of lattice-girder, and diameter of top-bar. Static loads controlled by displacements are applied to test beams to obtain cracking and ultimate loads. Vertical displacements at the center of beams, strains of top-bar, crack propagation in concrete slab, and final failure modes are carefully monitored. The obtained cracking loads are compared to the analytical results obtained by elastic analyses. Long-term analyses using age-adjusted effective modulus method (AEMM) are also conducted to investigate the effects of concrete shrinkage on the cracking loads. Based on the test results, the tensile strength and the design details of LB-DECKs are discussed to prevent longitudinal cracking of long span bridge decks.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.53-60
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• 2019

The purpose of this study is to evaluate the degree of improvement in strengths by mixing blast-furnace slag and fly ash in polymer cement mortar(PCM). The test specimens are prepared with EVA polymer dispersion, two types of Admixtures (blast-furnace slag and fly ash), five kinds of polymer-cement ratios (0, 5, 10, 15 and 20%), and six kinds of admixtures (0, 3, 5, 10, 15 and 20%). Plain cement mortar is also made for comparison. From the test results, the flowing of PCM is greatly improved with the mixing of the admixtures, and strengths of PCM compared to ordinary cement mortar are also improved due to a decrease in water cement ratio. In addition, the strength characteristics of PCM by admixtures are greatly improved in flexural strength with fly ash compared to other strengths. It is apparent that the optimum mix proportions with polymer-cement ratio of 10% or more, admixture contents 5 to 10% of flay ash for flexural strength improvement of EVA-cement mortar are recommended in this study.