냉간성형 듀플렉스계 스테인리스강(STS329FLD) 용접접합부 모재 블록전단파단 거동

Abstract

본 연구에서는 냉간성형 듀플렉스계 스테인리스강(STS329FLD) 용접접합부의 모재 블록전단파단 거동을 조사한다. 용접접합부는 전형형적인 블록전단파단이 발생하였고, 용접길이가 증가함에 따라 최대내력도 상승하였다. 현행기준(KBC2016/AISC2016과 EC3)과 용접접합부에 대한 기존연구자에 의해 제안된 식에 의한 블록전단파단내력과 실험최대내력을 비교하였다. 현행기준식은 용접접합부의 블록전단내력을 평균 27%정도 과소평가하였고 기존연구자의 제안식에 의해서는 최대 44%정도 과대평가하는 것으로 나타났다.

Recently, lean duplex stainless steel, STS329FLD with less nickel (reduced to 0.5~1.5%) has been developed as a substitute of austenitic stainless steel (8%~10.5% nickel in STS304) and included in Korean standards (KS). This paper investigates the block shear behavior of cold-formed duplex stainless steel (STS329FLD, nominal plate thickness of 1.5mm) fillet-welded connection with base metal fracture. Main variables are weld lengths in the longitudinal and the transverse directions of applied force ranged from 20mm to 50mm. As a result, specimens failed by typical block shear facture (the combination of gross section tensile fracture and shear fracture or shear yielding) and ultimate strength of the specimens got higher with the increase of weld length. Block shear fracture strengths predicted by current design specifications (KBC2016/AISC2016 and EC3) and existing proposed equations for welded connections by Topkaya, Oosterhof & Driver and Lee et al. were compared with test strengths. KBC2016/AISC2016 and EC3 design specifications underestimated block shear strength of STS329FLD welded connections by on average 24%, 29%, respectively and Oosterhof & Driver, Topkaya and Lee et al’s equations overestimated the ultimate strength of the welded connection by the range of 3% to 44%.