Keywords: welded beam-to-column connections, T-stiffeners, semi-rigid connections, steel connections, finite element analysis, non-linear analysis.

Welded beam-to-column connection with T-stiffener is particularly useful in Multi-storey buildings where beams are framed to column web to support lateral loads. The conventional design method of such connection was based on a set of empirical formulas outlined by Salmon [1] and Machaly [2]. The T-stiffener flange and web thickness were determined as a function of the beam flange area regardless to the applied moment on the connection. On the other hand, the size of T-stiffener welds was determined based on an assumption that one-third of the applied moment, , was supported by the T-stiffener flange weld whereas three-quarters of was supported by the T-stiffener. Therefore, it was necessary to analyze the connection to study the connection behavior and stress distribution, evaluate the design assumptions used in the conventional design method, and to propose a set of design formulas that reflect the analysis results.

In this work, a finite element model was constructed for the connection using the general purpose finite element program ANSYS [3]. All the connection plate elements were modeled with the four-noded isoparametric shell element, Shell43, built in ANSYS element library whereas welds were modeled with the link element, Combin14. The analysis was conducted incorporating material and geometric non-linearties using the arc-length method at which the applied moment on the connection is applied incrementaly and solution is obtained at each load increment by iterations.

Unlike the conventional design method, the finite element analysis of the connection showed that the applied moment on the connection was almost equally distributed among the T-stiffener flange and web welds. On the other hand, the application of the allowable stress requirements stipulated in the Egyptian Code of Practice, ECP 2001 [4] revealed that a connection designed by the conventional design method can only support an allowable moment value equals to 43% of the beam allowable moment capacity.

Based on a comprehensive parametric analysis conducted in a previous research work, the effective parameters controlling the connection behavior were found to be the T-stiffener flange and web thicknesses and ratio of the beam flange width to the T-stiffener flange width, . The finite element analysis conducted herein was used to determine the recommended design values for the connection parameters such that the connection can support 85% of the beam allowable moment capacity for each value of . Such limiting moment value was set to suit the moment capacity of the fillet weld connecting the T-stiffener and the beam.

Based on simple mathematical models and finite element results, a set of design equations was established for the connection. The proposed design equation describe the T-stiffener flange and weld thickness, flange and web weld sizes and portion of applied moment supported by the T-stiffener flange and web welds. The use of such design equations is limited to the condition that and the applied moment, , does not exceed 85% of the beam allowable moment capacity.

1

Salmon, C.G., Johnson, J.E.,"Steel Structures: Behavior and Design", Harper and Row Publishers, 4th Edition, 1996.

2

Machaly, E.B., "Behavior, Analysis and Design of Steel Work Connections", 4th Edition, 2000.

3

Desalvo, G.J., Gorman, R.W., "ANSYS User's Manual", Swanson Analysis Systems, Houston, PA, 1989.

4

Egyptian Code of practice for Steel Construction and Bridges (Allowable Stress Design), Code no. (205), Permanent Committee for the Code of Practice for Steel Construction and Bridges, 1st Edition 2001.

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