Experimental and analytical studies are conducted on four repair/upgrade details for welded moment connections. The first of these seeks to improve the weld material without doing anything to the beam and column sections at the joint (weld enhancement). The simplest of these removes the cracked weld material and replaces it with a more ductile, notch-tough weld material (weld replacement). A more recently developed procedure places a layer of weld material having a higher notch toughness on top of the existing welds (weld overlay).
The second weld repair/retrofit detail considers the addition of rectangular cover plates to the top and bottom beam flanges. The plates which are the same width as the beam flange are beveled to permit partial penetration welds along the sides. A variation of this detail adds a rectangular miniplate which is half the length and width of a full sized plate to the top and bottom beam flanges.
The third detail considers the addition of a vertical, triangular plate (fin) to the top and bottom flanges of the beam in the plane of the web. A modification to the initial detail includes a hole in the fin which moves the net section of the fin away from the column face and causes yielding to occur at the hole rather than the column face. A fourth detail is a retrofit detail which considers a reduced beam section formed by using drilled holes to approximate the geometry of a tapered cut in the beam flanges.
These details are shown to provide varying degrees of improvement in connection behavior with plastic rotation capacities between 1.5 percent and 4 percent being achieved. The best results were obtained by the horizontal flange plates, both full sized and miniplate. The worst perfor- mance occurred using a single flange plate. The two weld overlays tested attained plastic rotations of 3 and 3.5 percent.
Detailed finite element analyses are conducted for all of these configurations. The analytical model was used to give direction to the test program and to correlate with the test results. Calcu- lated stresses in the analytical model are shown as colored stress contours. The analytical model was loaded with an increasing, monotonic load at the beam tip. In this manner an estimate of the skeleton curve of the hysteresis curve was obtained.
In order to repair connections in frames located on the perimeter of a building it is often necessary to cut access windows in the web of the beam and in the panel zone of the column. One full size specimen of this type was tested to failure to verify the performance of the connection after the web windows were closed with welded plates. Results indicated that the windows create an eccentricity which may cause premature buckling of the beam web.
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