Behaviour of Ferritic Stainless Steel Bolted T‐stubs Under Tension‐Part 1: Experimental Investigations

Abstract

Research on stainless steel structures has primarily focused on the structural response and design of individual members, whilst the response of joints has received far less attention to date. Recently, a series of experimental tests has been conducted on austenitic and duplex stainless steel moment resisting connections which highlighted both the excellent ductility and significant overstrength exhibited by such connections as well as the severe conservatism of current design rules specified in EN 1993‐1‐8 when applied to stainless steel joints. A comprehensive experimental study on the structural behaviour of stainless steel T‐stubs fabricated from EN 1.4003 ferritic stainless steel grade is reported in this paper. The tested configurations included both single and double bolt rows and have been assembled with A4‐80 stainless steel bolts. In order to determine the material characteristics of the T‐stubs and the connecting bolts, tensile coupon tests were performed and the material anisotropy exhibited by ferritic stainless steel has been quantified. The ultimate resistance, plastic deformation capacity and failure mode of each T‐stub were obtained and are reported herein. The obtained results are utilised to assess the accuracy of existing design rules and to validate the numerical model discussed in the companion paper.

Behaviour of Ferritic Stainless Steel Bolted T‐stubs Under Tension‐Part 2: Numerical Investigations

“…The comparisons between the FE predictions and the test results including the force-deformation curves and the failure modes of the specimens are presented in Figure 4. It can be observed that the numerically predicted load-deformation curves are in close agreement with the experimental ones reported in the companion paper [30]. The anisotropic FE models significantly improve the accuracy of the predictions as evidenced by the load-displacement curves especially for the models of specimens S1, S2, D2 and D3 with respect to the experimental response.…”

“…Furthermore, the stress distribution developed the flange to web junction at various load levels is inspected and the validity of current design assumptions regarding the development of stresses and the applicability of plastic design procedures is assessed. In line with the companion paper [30], the importance of membrane action at high deformations is highlighted and its importance on predicting the ultimate failure load is demonstrated.…”

“…For sections D2 and D4 a more uniform stress distribution at the plastic load level can be observed along the T-stubs. For all models, at the attainment of the plastic resistance of the T-stub, the maximum recorded stress is approximately 25% higher than the nominal yield stress, a value that corresponds to the ultimate tensile stress in the longitudinal direction as reported in [30]. In a recent study on austenitic and duplex stainless steel T-stubs [29] the respective value was 100% higher than the nominal yield stress, due to the significantly more favourable strain-hardening characteristics that these grades exhibit compared to ferritic stainless steel.…”

“…The studies in the literature focused primarily on austenitic and duplex stainless steel grades, while the structural performance of ferritic stainless steel connections has not been studied to date. In order to fill this gap in the literature, the ultimate behaviour of ferritic stainless steel bolted T-stubs under tension has been studied by the authors and reported as a companion paper in reference [30].…”

“…In order to incorporate the material anisotropy in the numerical analysis, material properties in the longitudinal, transverse and diagonal directions are required. In the scope of this study, material properties were adopted from the companion paper [30]. In Table 1, the average material property values form the duplicate specimens are reported for each direction.…”