A parametric study on OPB fire response of steel CHS T-joints

Document Type : Research Article

Authors

1 Ph.D student, Civil Engineering Department, K.N.Toosi University of Technology, Tehran, Iran

2 Professor of Civil Engineering Department, K.N.Toosi University of Technology

3 Department of Civil Engineering, Parand Branch, Islamic Azad University, Parand, Iran

4 Ph.D student, Civil Engineering Department, K.N.Toosi University of Technology

5 Master of Structural Laboratory, Civil Engineering Department, K.N.Toosi University of Technology

Abstract

The behaviour of steel circular hollow section (CHS) T-joints under combined fire load and out-of-plane bending (OPB) is investigated. A review of the literature indicates that the subject has not been previously considered by researchers. The authors carried out the first laboratory experimental study on OPB behaviour of simple steel tubular T-joints under standard fire. The results of an experimental and numerical study performed on three small-scale steel tubular T-joint specimens is reported. One specimen was tested at ambient temperature under quasi-static incremental OPB moment in the brace and the other two specimens were tested under OPB moment plus exposure to ISO-834 standard fire.

In order to have a deeper insight into the strength and failure mechanism of steel tubular T-joints under fire, their OPB behaviour was also studied using a coupled mechanical-thermal finite element modelling. The numerical model was validated against the experimental results and reasonable agreements were achieved. A parametric study was then performed on the OPB fire behaviour of full-scale steel tubular T-joints. The results showed that the superimposed OPB ratio in the brace and the diameter ratio parameter had more pronounced effects on the fire response of the joint as compared to other geometric and loading parameters. Increasing the the diameter ratio parameter from 0.2 to 1, reduced the joint’s residual rotation by 56 % and increased the critical temperature by 23 %. By increasing OPB ratio from 0.2 to 1, the residual rotation increased by 245 % and the critical temperature decreased by 37%.

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