Stress-Deformation Behavior of Connection

Figure 6 shows the deformation configuration at ultimate state for model A2. From this figure, it is observed that although the horizontal maximum displacement is occurred at the heel of top angle, the vicinity of the bolt hole of top angle’s vertical leg is deformed severely. Figure 7 shows the von Mises stress contour at ultimate state for model A2, in which at this time, applied connection moment is evaluated to be 103.5 kNm. From this figure, it is confirmed that the comparatively higher stresses were developed near the bolt hole and fillets of top angle. The bending moment evaluated using the reaction force developed at the beam end support can be converted into tension and compression forces in the connection, which are transferred to the column flange through the bolts fastening angles to the column flange. The bolts are elongated due to the bending-tension force applied to the

Fig. 6. Deformation configuration of connection model A2 at ultimate state.

Fig. 7. Von Mises stress contour at ultimate state for model A2.

top angle, and the top angle’s vertical leg behaves as a lever supported in the area from the upper portion of bolt hole through the top edge. As a result of interaction among top angle, column flange and bolts, a reaction pressure is developed in the area from the centerline of bolt hole through the top edge. To keep the forces acting in the top angle in equilibrium state, an equivalent additional tensile force corresponding to the reaction pressure is surcharged to the bolts. The reaction pressure developed on vertical leg can be substituted by a resultant, which is well known as prying force. So, tension bolts undergo not only pretension and bending-tension forces but also prying force.