A Study on the Calculation of Load Resistance Factor of over Tension Anchors by Optimization Design

Soung-Kyu Lee; Yeong-Jin Lee; Yong-Jae Song; Tae-Jun Cho; Kang-Il Lee

doi:10.12814/jkgss.2023.22.4.017

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2023 Vol.22, Issue 4 Preview Page Next Page

Research Article

A Study on the Calculation of Load Resistance Factor of over Tension Anchors by Optimization Design 최적화 설계를 통한 과긴장 앵커의 하중-저항계수 산정 연구

31 December 2023. pp. 17-26

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Abstract

강연선의 손상 및 파단위험에 대하여 적극적으로 대처하기 위해서는 기존의 사후 유지관리 체계만으로는 한계가 있으며 시설물의 내구성, 안전성 저하를 정량적으로 평가 및 예측하고 시설물의 자산가치를 고려한 합리적인 유지관리 체계의 구축이 요구된다. 따라서 가설앵커에 큰 결함이 발생하기 전 사전조치가 이루어지도록 하는 선제적 유지관리 방안을 고려해볼 가치가 있다. 이를 위해 본 연구에서는 선제적 과긴장 공법을 고안하여 설계 및 현장시험을 통해 그 효과를 검토하고 신뢰성 기반 최적화 설계를 수행하여 저항계수를 산정하였다. 이때 과긴장 앵커의 흙막이 가시설 지지효과는 강연선 파단전 유효긴장력에 대한 강연선 파단후 잔존긴장력의 비를 이용하여 평가하였으며 저항계수는 각 확률변수에 대한 최적해를 Excel solver를 이용하여 구하고 이를 한계상태식에 적용하여 산정하였다. 연구결과 과긴장률이 125%~130%인 경우 강연선 파단 후에도 높은 흙막이 가시설 지지효과를 보였으며 최적화 설계결과 하중계수(γ)는 1.25, 저항계수 Φ1, Φ2, Φ3은 0.7, 0.5, 0.6을 적용함이 적절한 것으로 나타났다.

Keywords

Anchor

P.C strand

Over tension method

Preventive maintenance

Resistance factor

To consider the risk of damage and fracture of P.C strands, the existing post-maintenance system alone has the limitations, hence it is necessary to quantitatively evaluate and predict the deterioration, durability and safety of facilities and establish a reasonable maintenance system considering the asset value of facilities. Therefore, it is worth considering a preventive maintenance plan that allows proactive measures to be taken before a major defect occurs in the temporary anchor. This study devised a preventive over tension method, reviewed its effectiveness through design and field tests, by calculating the resistance factors by performing a reliability-based optimization design. At this time, the over tension anchor method was evaluated using the ratio of the residual tension force after the fracture of P.C strands to the effective tension force before the fracture of P.C strand, followed by the resistance factor calculated by the optimal solution for each random variables using Excel solver and applying it to the limit state equations. As a result of the study, if the over tension ratio is 125% to 130%, the remaining strands showed a high resistance effect even after the fracture of P.C strand. As a result of the optimization design, it was found that it is appropriate to apply the load factor (γ) of 1.25, and the resistance factors of Φ1, Φ2, Φ3 as 0.7, 0.5, 0.6.

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Information

Publisher :Korean Geosythetics Society
Publisher(Ko) :한국지반신소재학회
Journal Title :Journal of the Korean Geosynthetics Society
Journal Title(Ko) :한국지반신소재학회 논문집
Volume : 22
No :4
Pages :17-26
Received Date : 2023-10-10
Revised Date : 2023-11-28
Accepted Date : 2023-12-11
DOI :https://doi.org/10.12814/jkgss.2023.22.4.017

Journal of the Korean Geosynthetics Society ISSN:2508-2876(Print) 2287-9528(Online) 한국지반신소재학회 논문집

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