• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.727-735
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• 2012

Recently, a high-strength strand of 2400 MPa was developed using domestic technologies. In 2011, KS D 7002 was revised to cover the newly developed high-strength strands to support their practical usage. Presently, however, discussions and evaluations are not sufficient on the mechanical properties of the strands and their performance in structural members. Also, there were no detailed reviews on the need to revise the current design code for practical use of the high-strength strands. In this study, flexural behavior of a member with the high-strength strands was estimated through sectional analysis and a review and comparison of the domestic and foreign design codes were conducted considering the analysis results. Also, the need for the revision of the design code was discussed. Such discussion especially focused on the estimation of the stress in strand, which related with various issues such as determination methods for yield point of strands, time-dependent loss of prestressing force, estimation of stress in strand at member failure, and net strain limit for ductile failure of member. The discussion revealed that some parts in the design code need a revision and the further studies are required.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.33 no.12
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• pp.45-52
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• 2017

The precast concrete (PC) method has many advantages in fast construction, quality control, etc. In domestic construction market, however, its application has been quite limited because of the concerns about structural integrity and seismic performances due to the discrete connections between precast concrete members. By applying the post-tensioning method, the precast beam-column connection can be well tightened, allowing improved structural integrity, and proper seismic performances can be also achieved. In this study, reversed cyclic tests have been conducted on the beam-column connection specimens, where the test variables included the compressive strength of grouting mortar and the tensile strengths of prestressing strands, based on which their seismic performances have been examined in detail. The post-tensioned PC beam-column connections showed good seismic performances comparable to that of the monolithic reinforced concrete connection specimen. When 2400 MPa prestressing strands are applied to the beam-column connection, it is preferable to adjust the prestress level similar to that applied for the 1860 MPa prestressing strands to avoid premature local crushing failures at the beam-column connections.

• Journal of Korean Association for Spatial Structures
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• v.20 no.1
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• pp.41-48
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• 2020

In this study, the design of anchorage zone for unbonded post-tensioned concrete beam with single tendons of ultimate strength 2400MPa was evaluated to verify that the KDS 14 20 60(2016) and KHBDC 2010 codes are applicable. The experimental results showed that the bursting force equation of current design codes underestimated bursting stress measured by test, because the KDS 14 20 60(2016) and KHBDC 2010 propose the location of the maximum bursting force 0.5h which is the half of the height of member regardless of stress contribution. Although the allowable bearing force calculated by current design codes was not satisfied the prestressing force, the cracks and failure in anchorage zone was not observed due to the strengthening effect of anchorage zone reinforcement.