Kapalı kesit paslanmaz çelik çekme elemanları kaynaklı uç birleşimlerinin davranış ve tasarımı

Abstract

Among the various alternatives to make a steel tubular member connection, making a slotted and gusset plate welded connection is one of the most frequently preferred alternatives. This type of connection is essentially an end connection that is made by slotting the tube longitudinally, inserting the gusset plate and then placing longitudinal fillet welds at the tube-to-plate interface. In this thesis an experimental and numerical study on the behaviour of such connections in stainless steel is presented. Relatively high initial cost of stainless steel is one burden for its structural use. To achieve a safe and economic design it is necessary to investigate the mechanical response of structural components, connections and the overall system, thus leading to efficient design. Therefore the results of this thesis study are considered to serve this purpose for the chosen connection type. 24 specimens were tested under concentrically applied axial tensile forces for varying tube-to-gusset plate weld lengths. Both circular and box section members were considered in the test program. Load-deformation curves were obtained and comparisons were made in terms of strength and ductility. General deformation behavior under axial tensile loading and variation of strength with weld length were also examined. Following the experimental study, a numerical model was developed that could simulate the test behavior by using the ABAQUS® finite element software. Nonlinear modeling features of the software were used to simulate as closely as possible the full nonlinear behavior of the connections. Experimental as well as the numerical ultimate strength values achieved for the range of geometries considered in the test program were then critically examined and compared with currently available design guidance for slotted gusset plate welded tubular end connections. It is noted that no specific rules exist in international specifications on structural stainless steel which cover the design of such connections. Therefore, the results of this study are compared with the existing design rules for carbon steel. For design purposes which would take into account of serviceability limitations regarding the excessive distortions of the connections a lower test strength value than the peak test strength value is suggested to be applied. For this purpose a first yield approach is adopted to calculate the design strength levels. For all the specimen tests a yield capacity point (YCP) is identified on the test load-displacement plots. In particular, the YCP values were used to propose a design equation for the calculation of the shear-lag reduction factor. This factor takes into account the loss of efficiency of the connection due to shear lag under axial tensile loading. For the dimensional range studied in the test program the proposed equation can be used for the design of slotted and gusset plate welded connections in stainless steel in Grade 304. The results and original contributions are summarized and recommendations for design are also provided.